<?xmlversion="1.0" encoding="US-ASCII"?>version='1.0' encoding='utf-8'?> <!DOCTYPE rfc SYSTEM"rfc2629.dtd"> <?rfc toc="yes"?> <?rfc tocompact="yes"?> <?rfc tocdepth="4"?> <?rfc tocindent="yes"?> <?rfc symrefs="yes"?> <?rfc sortrefs="yes"?> <?rfc comments="yes"?> <?rfc inline="yes"?> <?rfc compact="yes"?> <?rfc subcompact="no"?>"rfc2629-xhtml.ent"> <rfc xmlns:xi="http://www.w3.org/2001/XInclude" category="std" docName="draft-ietf-dots-signal-channel-41"ipr="trust200902">number="8782" ipr="trust200902" obsoletes="" updates="" submissionType="IETF" consensus="true" xml:lang="en" tocInclude="true" tocDepth="4" symRefs="true" sortRefs="true" version="3"> <!-- xml2rfc v2v3 conversion 2.39.0 --> <front> <title abbrev="DOTS Signal Channel Protocol">Distributed Denial-of-Service Open Threat Signaling (DOTS) Signal Channel Specification</title> <seriesInfo name="RFC" value="8782"/> <author fullname="TirumaleswarReddy"Reddy.K" initials="T." role="editor"surname="Reddy">surname="Reddy.K"> <organization abbrev="McAfee">McAfee, Inc.</organization> <address> <postal> <street>Embassy Golf Link Business Park</street> <city>Bangalore</city> <region>Karnataka</region> <code>560071</code> <country>India</country> </postal> <email>kondtir@gmail.com</email> </address> </author> <author fullname="Mohamed Boucadair" initials="M." role="editor" surname="Boucadair"> <organization>Orange</organization> <address> <postal><street></street><city>Rennes</city><region></region><code>35000</code> <country>France</country> </postal> <email>mohamed.boucadair@orange.com</email> </address> </author> <author fullname="Prashanth Patil" initials="P." surname="Patil"> <organization abbrev="Cisco">Cisco Systems, Inc.</organization> <address><postal> <street></street> <street></street> <city></city> <country></country> </postal><email>praspati@cisco.com</email> </address> </author> <author fullname="Andrew Mortensen" initials="A." surname="Mortensen"> <organization>Arbor Networks, Inc.</organization> <address> <postal> <street>2727 S. StateSt</street>Street</street> <city>AnnArbor, MI</city> <region></region>Arbor</city> <region>MI</region> <code>48104</code> <country>UnitedStates</country>States of America</country> </postal> <email>andrew@moretension.com</email> </address> </author> <author fullname="Nik Teague" initials="N." surname="Teague"> <organization>Iron Mountain Data Centers</organization> <address> <postal><street></street> <city></city> <region></region> <code></code><country>United Kingdom</country> </postal> <email>nteague@ironmountain.co.uk</email> </address> </author> <date/>month="May" year="2020"/> <workgroup>DOTS</workgroup> <keyword>security</keyword> <keyword>mitigation</keyword> <keyword>service delivery</keyword> <keyword>connectivity</keyword> <keyword>anti-DDoS</keyword> <keyword>automation</keyword> <keyword>cooperation</keyword> <keyword>resilience</keyword> <keyword>filtering</keyword> <keyword>security center</keyword> <keyword>mitigator</keyword> <keyword>scrubbing</keyword> <keyword>dynamic service protection</keyword> <keyword>dynamic mitigation</keyword> <keyword>cooperative networking</keyword> <keyword>protective networking</keyword> <abstract> <t>This document specifies theDOTSDistributed Denial-of-Service Open Threat Signaling (DOTS) signal channel, a protocol for signaling the need for protection against Distributed Denial-of-Service (DDoS) attacks to a server capable of enabling network traffic mitigation on behalf of the requesting client.</t> <t>A companion document defines the DOTS data channel, a separate reliable communication layer for DOTS management and configuration purposes.</t> </abstract><note title="Editorial Note (To be removed by RFC Editor)"> <t>Please update these statements within the document with the RFC number to be assigned to this document:<list style="symbols"> <t>"This version of this YANG module is part of RFC XXXX;"</t> <t>"RFC XXXX: Distributed Denial-of-Service Open Threat Signaling (DOTS) Signal Channel Specification";</t> <t>"| [RFCXXXX] |"</t> <t>reference: RFC XXXX</t> </list></t> <t>Please update this statement with the RFC number to be assigned to the following documents:<list style="symbols"> <t>"RFC YYYY: Distributed Denial-of-Service Open Threat Signaling (DOTS) Data Channel Specification (used to be I-D.ietf-dots-data-channel)</t> </list></t> <t>Please update TBD/TBD1/TBD2 statements with the assignments made by IANA to DOTS Signal Channel Protocol.</t> <t>Also, please update the "revision" date of the YANG modules.</t> </note></front> <middle> <section anchor="introduction"title="Introduction">numbered="true" toc="default"> <name>Introduction</name> <t>Adistributed denial-of-serviceDistributed Denial-of-Service (DDoS) attack is a distributed attempt to make machines or network resources unavailable to their intended users. In most cases, sufficient scale for an effective attack can be achieved by compromising enoughend-hostsend hosts and using those infected hosts to perpetrate and amplify the attack. The victim in this attack can be an application server, a host, a router, a firewall, or an entire network.</t><t>Network<t> Network applications have finite resources like CPU cycles, the number of processes or threads they can create and use, the maximum number of simultaneous connections they can handle, thelimitedresourcesofassigned to the control plane, etc. When processing network traffic, such applications are supposed to use these resources to provide the intended functionality in the most efficient manner. However, a DDoS attacker may be able to prevent an application from performing its intended task by making the application exhaust its finite resources.</t> <t>A TCP DDoSSYN-floodSYN flood <xreftarget="RFC4987"></xref>,target="RFC4987" format="default"/>, for example, is a memory-exhausting attack while anACK-floodACK flood is a CPU-exhausting attack. Attacks on the link are carried out by sending enough traffic so that the link becomes congested, thereby likely causing packet loss for legitimate traffic. Stateful firewalls can also be attacked by sending traffic that causes the firewall to maintain an excessive number of states that may jeopardize the firewall's operation overall,besidesin addition to likely performance impacts. The firewall then runs out of memory, and it can no longer instantiate the states required to process legitimate flows. Other possible DDoS attacks are discussed in <xreftarget="RFC4732"></xref>.</t>target="RFC4732" format="default"/>.</t> <t>In many cases, it may not be possible for network administrators to determine the cause(s) of an attack. They may instead just realize that certain resources seem to be under attack. This document defines a lightweight protocol that allows a DOTS client to request mitigation from one or more DOTS servers for protection against detected, suspected, or anticipated attacks. This protocol enables cooperation between DOTS agents to permit ahighly-automatedhighly automated network defense that is robust, reliable, and secure. Note that "secure" means the support of the features defined inSection 2.4 of<xreftarget="RFC8612"></xref>.</t>target="RFC8612" section="2.4" sectionFormat="of" format="default"/>.</t> <t>An example of a network diagram that illustrates a deployment of DOTS agents is shown in <xreftarget="fig1"></xref>.target="fig1" format="default"/>. In this example, a DOTS server is operating on the access network. A DOTS client is located on the LAN (Local Area Network), while a DOTS gateway is embedded in the CPE (Customer Premises Equipment).</t><t><figure anchor="fig1" title="Sample<figure anchor="fig1"> <name>Sample DOTS Deployment(1)">(1)</name> <artworkalign="center"><![CDATA[align="center" name="" type="" alt=""><![CDATA[ Network Resource CPErouterRouter AccessnetworkNetwork __________ +-----------+ +--------------+ +-------------+ / \ | |___| |____| |___ | Internet | |DOTSclient|Client| | DOTSgatewayGateway | | DOTSserverServer | | | | | | | | | | | +-----------+ +--------------+ +-------------+\__________/]]></artwork> </figure></t>\__________/ ]]></artwork> </figure> <t>DOTS servers can also be reachable over the Internet, as depicted in <xreftarget="fig_blah"></xref>.</t> <t><figure anchor="fig_blah" title="Sampletarget="fig_blah" format="default"/>.</t> <figure anchor="fig_blah"> <name>Sample DOTS Deployment(2)">(2)</name> <artworkalign="center"><![CDATA[align="center" name="" type="" alt=""><![CDATA[ Network DDoSmitigationMitigation Resource CPErouterRouter __________serviceService +-----------++-------------++--------------+ / \ +-------------+ | |___| |____| |___ | | |DOTSclient| |DOTS gatewayClient| | DOTS Gateway | | Internet | | DOTSserverServer | | | | | | | | | +-----------++-------------++--------------+ \__________/ +-------------+ ]]></artwork></figure>In</figure> <t>In typical deployments, the DOTS client belongs to a different administrative domain than the DOTS server. For example, the DOTS client is embedded in a firewall protecting services owned and operated by a customer, while the DOTS server is owned and operated by a different administrative entity (service provider, typically) providing DDoS mitigation services. The latter might or might not provide connectivity services to the network hosting the DOTS client.</t> <t>The DOTS server may (not) be co-located with the DOTS mitigator. In typical deployments, the DOTS server belongs to the same administrative domain as the mitigator. The DOTS client can communicate directly with a DOTS server or indirectly via a DOTS gateway.</t><t>The<t>This document adheres to the DOTS architecture <xreftarget="I-D.ietf-dots-architecture"></xref>.target="I-D.ietf-dots-architecture" format="default"/>. The requirements for DOTS signal channel protocol are documented in <xreftarget="RFC8612"></xref>.target="RFC8612" format="default"/>. This document satisfies all the use cases discussed in <xreftarget="I-D.ietf-dots-use-cases"></xref>.</t>target="I-D.ietf-dots-use-cases" format="default"/>.</t> <t>This document focuses on the DOTS signal channel. This is a companion document of the DOTS data channel specification <xreftarget="I-D.ietf-dots-data-channel"></xref>target="RFC8783" format="default"/> that defines a configuration and a bulk data exchange mechanism supporting the DOTS signal channel.</t> </section> <section anchor="notation"title="Terminology">numbered="true" toc="default"> <name>Terminology</name> <t>The key words"MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY","<bcp14>MUST</bcp14>", "<bcp14>MUST NOT</bcp14>", "<bcp14>REQUIRED</bcp14>", "<bcp14>SHALL</bcp14>", "<bcp14>SHALL NOT</bcp14>", "<bcp14>SHOULD</bcp14>", "<bcp14>SHOULD NOT</bcp14>", "<bcp14>RECOMMENDED</bcp14>", "<bcp14>NOT RECOMMENDED</bcp14>", "<bcp14>MAY</bcp14>", and"OPTIONAL""<bcp14>OPTIONAL</bcp14>" in this document are to be interpreted as described in BCP 14 <xreftarget="RFC2119"></xref><xref target="RFC8174"></xref>target="RFC2119" format="default"/><xref target="RFC8174" format="default"/> when, and only when, they appear in all capitals, as shown here.</t> <t>(D)TLS is used for statements that apply to both Transport Layer Security <xreftarget="RFC5246"></xref><xref target="RFC8446"></xref>target="RFC5246" format="default"/> <xref target="RFC8446" format="default"/> and Datagram Transport Layer Security <xreftarget="RFC6347"></xref>.target="RFC6347" format="default"/>. Specific terms are used for any statement that applies to either protocol alone.</t> <t>The reader should be familiar with the terms defined in <xreftarget="RFC8612"></xref>.</t>target="RFC8612" format="default"/>.</t> <t>The meaning of the symbols in YANG tree diagrams is defined in <xreftarget="RFC8340"></xref>.</t>target="RFC8340" format="default"/>.</t> </section> <sectiontitle="Design Overview">numbered="true" toc="default"> <name>Design Overview</name> <t>The DOTS signal channel is built on top of the Constrained Application Protocol (CoAP) <xreftarget="RFC7252"></xref>,target="RFC7252" format="default"/>, a lightweight protocol originally designed for constrained devices and networks. The many features of CoAP (expectation of packet loss, support for asynchronous Non-confirmable messaging, congestion control, small message overhead limiting the need for fragmentation, use of minimal resources, and support for (D)TLS)makesmake it a good candidate upon which to build the DOTS signalingmechanism from.</t>mechanism.</t> <t>DOTS clients and servers behave as CoAP endpoints. By default, a DOTS client (or server) behaves as a CoAP client (or server). Nevertheless, a DOTS client (or server) behaves as a CoAP server (or client) for specific operations such as DOTS heartbeat operations (<xreftarget="hb"></xref>).</t>target="hb" format="default"/>).</t> <t>The DOTS signal channel is layered on existing standards(<xref target="fig_dots"></xref>).</t> <t><figure anchor="fig_dots" title="Abstract(see <xref target="fig_dots" format="default"/>).</t> <figure anchor="fig_dots"> <name>Abstract Layering of DOTS Signal Channel over CoAP over(D)TLS">(D)TLS</name> <artworkalign="center"><![CDATA[+---------------------+align="center" name="" type="" alt=""><![CDATA[ +---------------------+ | DOTS Signal Channel | +---------------------+ | CoAP | +----------+----------+ | TLS | DTLS | +----------+----------+ | TCP | UDP | +----------+----------+ | IP | +---------------------+ ]]></artwork></figure></t></figure> <t>In some cases, a DOTS client and server may have a mutual agreement to use a specific port number, such as by explicit configuration or dynamic discovery <xreftarget="I-D.ietf-dots-server-discovery"></xref>.target="I-D.ietf-dots-server-discovery" format="default"/>. Absent such mutual agreement, the DOTS signal channelMUST<bcp14>MUST</bcp14> run over port numberTBD4646 as defined in <xreftarget="port"></xref>,target="port" format="default"/>, for both UDP and TCP. In order to use a distinct port number (as opposed toTBD),4646), DOTS clients and serversSHOULD<bcp14>SHOULD</bcp14> support a configurable parameter to supply the port number to use.</t><t><list style="empty"><aside> <t>Note: The rationale for not using the default port number 5684 ((D)TLS CoAP) is to avoid the discovery of services and resources discussed in <xreftarget="RFC7252"></xref>target="RFC7252" format="default"/> and allow for differentiated behaviors in environments where both a DOTS gateway and anIoTInternet of Things (IoT) gateway (e.g., Figure 3 of <xreftarget="RFC7452"></xref>)target="RFC7452" format="default"/>) are co-located.<vspace blankLines="1" />Particularly,</t> <t>Particularly, the use of a default port number is meant to simplify DOTS deployment in scenarios where no explicit IP address configuration is required. For example, the use of the default router as the DOTS server aims to ease DOTS deployment within LANs (inwhich,which CPEs embed a DOTS gateway as illustrated in Figures <xref format="counter"target="fig1"></xref>target="fig1"/> and <xref format="counter"target="fig_blah"></xref>)target="fig_blah"/>) without requiring a sophisticated discovery method and configuration tasks within the LAN. It is also possible to use anycast addresses for DOTS servers to simplify DOTS client configuration, including service discovery. In such an anycast-based scenario, a DOTS client initiating a DOTS session to the DOTS server anycast address may, for example, be (1) redirected to the DOTS server unicast address to be used by the DOTS client following the procedure discussed in <xreftarget="redirect"></xref>target="redirect" format="default"/> or (2) relayed to a unicast DOTS server.</t></list>The</aside> <t>The signal channel uses the "coaps" URI scheme defined inSection 6 of<xreftarget="RFC7252"></xref>target="RFC7252" section="6" sectionFormat="of" format="default"/> and the "coaps+tcp" URI scheme defined inSection 8.2 of<xreftarget="RFC8323"></xref>target="RFC8323" section="8.2" sectionFormat="of" format="default"/> to identify DOTS server resources that are accessible using CoAP over UDP secured with DTLS and CoAP over TCP secured with TLS, respectively.</t> <t>The DOTS signal channel can be established between two DOTS agents prior to or during an attack. The DOTS signal channel is initiated by the DOTS client. The DOTS client can then negotiate, configure, and retrieve the DOTS signal channel session behavior with its DOTS peer (<xreftarget="sigconfig"></xref>).target="sigconfig" format="default"/>). Once the signal channel is established, the DOTS agents may periodically send heartbeats to keep the channel active (<xreftarget="hb"></xref>).target="hb" format="default"/>). At any time, the DOTS client may send a mitigation request message (<xreftarget="m_req"></xref>)target="m_req" format="default"/>) to a DOTS server over the active signal channel. While mitigation is active (because of the higher likelihood of packet loss during a DDoS attack), the DOTS server periodically sends status messages to the client, including basic mitigation feedback details. Mitigation remains active until the DOTS client explicitly terminatesmitigation,mitigation or the mitigation lifetime expires. Also, the DOTS server may rely on the signal channel session loss to trigger mitigation forpre-configuredpreconfigured mitigation requests (if any).</t> <t>DOTS signaling can happen with DTLS over UDP and TLS over TCP. Likewise, DOTS requests may be sent using IPv4 or IPv6 transfer capabilities. A Happy Eyeballs procedure for the DOTS signal channel is specified in <xreftarget="HE"></xref>.</t>target="HE" format="default"/>.</t> <t>A DOTS client is entitled to access onlytothe resources it creates. In particular, a DOTS clientcan notcannot retrieve data related to mitigation requests created by other DOTS clients of the same DOTS client domain.</t> <t>Messages exchanged between DOTS agents are serialized using Concise Binary Object Representation (CBOR) <xreftarget="RFC7049"></xref>,target="RFC7049" format="default"/>, a binary encoding scheme designed for small code and message size. CBOR-encoded payloads are used to carry signal channel-specific payload messageswhichthat convey request parameters and response information such as errors. In order to allow the reusing of data models across protocols, <xreftarget="RFC7951"></xref>target="RFC7951" format="default"/> specifies the JavaScript Object Notation (JSON) encoding of YANG-modeled data. A similar effort for CBOR is defined in <xreftarget="I-D.ietf-core-yang-cbor"></xref>.</t>target="I-D.ietf-core-yang-cbor" format="default"/>.</t> <t>DOTS agents determine that a CBOR data structure is a DOTS signal channel object from the application context, such as from the port number assigned to the DOTS signal channel. The other method DOTS agents use to indicate that a CBOR data structure is a DOTS signal channel object is the use of the "application/dots+cbor" content type (<xreftarget="MediaReg"></xref>).</t>target="MediaReg" format="default"/>).</t> <t>This document specifies a YANG module for representing DOTS mitigation scopes, DOTS signal channel session configuration data, and DOTS redirected signaling (<xreftarget="YANG"></xref>).target="YANG" format="default"/>). All parameters in the payload of the DOTS signal channel are mapped to CBOR types as specified in <xreftarget="mapping">Table 4</xref>.</t>target="cbor-key-values" format="default"/> (<xref target="mapping" format="default"/>).</t> <t>In order to prevent fragmentation, DOTS agents must follow the recommendations documented inSection 4.6 of<xreftarget="RFC7252"></xref>.target="RFC7252" section="4.6" sectionFormat="of" format="default"/>. Refer to <xreftarget="mtu"></xref>target="mtu" format="default"/> for more details.</t> <t>DOTS agentsMUST<bcp14>MUST</bcp14> support GET, PUT, and DELETE CoAP methods. The payload included in CoAP responses with 2.xx Response CodesMUST<bcp14>MUST</bcp14> be of content type "application/dots+cbor". CoAP responses with 4.xx and 5.xx error Response CodesMUST<bcp14>MUST</bcp14> include a diagnostic payload(Section 5.5.2 of <xref target="RFC7252"></xref>).(<xref target="RFC7252" section="5.5.2" sectionFormat="of" format="default"/>). TheDiagnostic Payloaddiagnostic payload may contain additional information to aid troubleshooting.</t> <t>In deployments where multiple DOTS clients are enabled in a network (owned and operated by the same entity), the DOTS server may detect conflicting mitigation requests from these clients. This document does not aim to specify a comprehensive list of conditions under which a DOTS server will characterize two mitigation requests from distinct DOTS clients as conflicting, nor does it recommend a DOTS server behavior for processing conflicting mitigation requests. Those considerations areimplementation-implementation anddeployment-specific.deployment specific. Nevertheless,thethis document specifies the mechanisms to notify DOTS clients when conflicts occur, including the conflict cause (<xreftarget="m_req"></xref>).</t>target="m_req" format="default"/>).</t> <t>In deployments where one or more translators (e.g., Traditional NAT <xreftarget="RFC3022"></xref>,target="RFC3022" format="default"/>, CGN <xreftarget="RFC6888"></xref>,target="RFC6888" format="default"/>, NAT64 <xreftarget="RFC6146"></xref>,target="RFC6146" format="default"/>, NPTv6 <xreftarget="RFC6296"></xref>)target="RFC6296" format="default"/>) are enabled between the client's network and the DOTS server, any DOTS signal channel messages forwarded to a DOTS serverMUST NOT<bcp14>MUST NOT</bcp14> include internal IP addresses/prefixes and/or port numbers; instead, external addresses/prefixes and/or port numbers as assigned by the translatorMUST<bcp14>MUST</bcp14> beused instead.used. This document does not make anyrecommendationrecommendations about possible translator discovery mechanisms. The following are some (non-exhaustive) deployment examples that may be considered:<list style="symbols"> <t>Port</t> <ul spacing="normal"> <li>Port Control Protocol (PCP) <xreftarget="RFC6887"></xref>target="RFC6887" format="default"/> or Session Traversal Utilities for NAT (STUN) <xreftarget="RFC5389"></xref>target="RFC8489" format="default"/> may be used to retrieve the external addresses/prefixes and/or port numbers. Information retrieved by means of PCP or STUN will be used to feed the DOTS signal channel messages that will be sent to a DOTSserver.</t> <t>Aserver.</li> <li>A DOTS gateway may be co-located with the translator. The DOTS gateway will need to update the DOTSmessages,messages based upon the local translator's bindingtable.</t> </list></t>table.</li> </ul> </section> <sectiontitle="DOTSnumbered="true" toc="default"> <name>DOTS Signal Channel: Messages &Behaviors">Behaviors</name> <section anchor="discover"title="DOTSnumbered="true" toc="default"> <name>DOTS Server(s)Discovery">Discovery</name> <t>This document assumes that DOTS clients are provisioned with the reachability information of their DOTS server(s) using any of a variety of means (e.g., localconfiguration,configuration or dynamic means such as DHCP <xreftarget="I-D.ietf-dots-server-discovery"></xref>).target="I-D.ietf-dots-server-discovery" format="default"/>). The description of such means is out of scope of this document.</t> <t>Likewise, it is out of the scope of this document to specify the behavior to be followed by a DOTS client in order to send DOTS requests when multiple DOTS servers are provisioned (e.g., contact all DOTS servers, select one DOTS server among the list). Such behavior is specified in other documents (e.g., <xreftarget="I-D.ietf-dots-multihoming"></xref>).</t>target="I-D.ietf-dots-multihoming" format="default"/>).</t> </section> <section anchor="uri-path"title="CoAP URIs">numbered="true" toc="default"> <name>CoAP URIs</name> <t>The DOTS serverMUST<bcp14>MUST</bcp14> support the use of thepath-prefixpath prefix of "/.well-known/" as defined in <xreftarget="RFC8615"></xref>target="RFC8615" format="default"/> and the registered name of "dots". Each DOTS operation isindicateddenoted by apath-suffixpath suffix that indicates the intended operation. The operation path (<xreftarget="uris"></xref>)target="uris" format="default"/>) is appended to thepath-prefixpath prefix to form the URI used with a CoAP request to perform the desired DOTS operation.</t><texttable<table align="center"anchor="uris" style="all" title="Operationsanchor="uris"> <name>Operations andtheirCorrespondingURIs"> <ttcol>Operation</ttcol> <ttcol>Operation Path</ttcol> <ttcol>Details</ttcol> <c>Mitigation</c> <c>/mitigate</c> <c><xref target="m_req"></xref></c> <c>Session configuration</c> <c>/config</c> <c><xref target="sigconfig"></xref></c> <c>Heartbeat</c> <c>/hb</c> <c><xref target="hb"></xref></c> </texttable> <t></t>URIs</name> <thead> <tr> <th align="left">Operation</th> <th align="left">Operation Path</th> <th align="left">Details</th> </tr> </thead> <tbody> <tr> <td align="left">Mitigation</td> <td align="left">/mitigate</td> <td align="left"> <xref target="m_req" format="default"/></td> </tr> <tr> <td align="left">Session configuration</td> <td align="left">/config</td> <td align="left"> <xref target="sigconfig" format="default"/></td> </tr> <tr> <td align="left">Heartbeat</td> <td align="left">/hb</td> <td align="left"> <xref target="hb" format="default"/></td> </tr> </tbody> </table> </section> <section anchor="HE"title="Happynumbered="true" toc="default"> <name>Happy Eyeballs for DOTS SignalChannel">Channel</name> <t><xreftarget="RFC8612"></xref>target="RFC8612" format="default"/> mentions that DOTS agents will have to support both connectionless and connection-oriented protocols. As such, the DOTS signal channel is designed to operate with DTLS over UDP and TLS over TCP. Further, a DOTS client may acquire a list of IPv4 and IPv6 addresses (<xreftarget="discover"></xref>),target="discover" format="default"/>), each of which can be used to contact the DOTS server using UDP and TCP. If no list of IPv4 and IPv6 addresses to contact the DOTS server is configured (or discovered), the DOTS client adds the IPv4/IPv6 addresses of its default router to the candidate list to contact the DOTS server.</t> <t>The following specifies the procedure to follow to select the address family and the transport protocol for sending DOTS signal channel messages.</t> <t>Such a procedure is needed to avoid experiencing long connection delays. For example, if an IPv4 path toreacha DOTS server is functional, but the DOTS server's IPv6 path isnon-functional,nonfunctional, a dual-stack DOTS client may experience a significant connection delay compared to an IPv4-only DOTSclient,client in the same network conditions. The other problem is that if a middlebox between the DOTS client and DOTS server is configured to block UDP traffic, the DOTS client will fail to establish a DTLS association with the DOTSserver and, as a consequence,server; consequently, it will have to fall back to TLS over TCP, thereby incurring significant connection delays.</t> <t>To overcome these connection setup problems, the DOTS client attempts to connect to its DOTS server(s) using both IPv6 and IPv4, and it tries both DTLS over UDP and TLS over TCP following a DOTS Happy Eyeballs approach. To some extent, this approach is similar to the Happy Eyeballs mechanism defined in <xreftarget="RFC8305"></xref>.target="RFC8305" format="default"/>. The connection attempts are performed by the DOTS client when itinitializes, orinitializes or, ingeneralgeneral, when it has to select an address family and transport to contact its DOTS server. The results of the Happy Eyeballs procedure are used by the DOTS client for sending its subsequent messages to the DOTS server. Thedifferencedifferences in behavior with respect to the Happy Eyeballs mechanism <xreftarget="RFC8305"></xref>target="RFC8305" format="default"/> are listed below:</t><t><list style="symbols"> <t>The<ul spacing="normal"> <li>The order of preference of the DOTS signal channel address family and transport protocol (most preferred first)is:is the following: UDP over IPv6, UDP over IPv4, TCP over IPv6, and finally TCP over IPv4. This order adheres to the address preference order specified in <xreftarget="RFC6724"></xref>target="RFC6724" format="default"/> and the DOTS signal channel preferencewhich privilegesthat promotes the use of UDP over TCP (to avoid TCP's head of lineblocking).</t> <t>The DOTS client afterblocking).</li> <li>After successfully establishing aconnection MUSTconnection, the DOTS client <bcp14>MUST</bcp14> cache information regarding the outcome of each connection attempt for a specific timeperiod, andperiod; it uses that information to avoid thrashing the network with subsequent attempts. The cached information is flushed when its age exceeds a specific time period on the order of few minutes (e.g., 10 min). Typically, if the DOTS client has tore-establishreestablish the connection with the same DOTS server within a few seconds after the Happy Eyeballs mechanism is completed, caching avoidstrashingthrashing the network especially in the presence of DDoS attacktraffic.</t> <t>Iftraffic.</li> <li>If a DOTS signal channel session is established with TLS (but DTLS failed), the DOTS client periodically repeats the mechanism to discover whether DOTS signal channel messages with DTLS over UDPbecomesbecome available from the DOTSserver,server; this is so the DOTS client can migrate the DOTS signal channel from TCP to UDP. Such probingSHOULD NOT<bcp14>SHOULD NOT</bcp14> be done more frequently than every 24 hours andMUST NOT<bcp14>MUST NOT</bcp14> be done more frequently than every 5minutes.</t> </list></t> <t><!--When connection attempts are made when no mitigation request is active, the DOTS client SHOULD use a "Connection Attempt Delay" [RFC8305] set to 5 seconds. -->Whenminutes.</li> </ul> <t> When connection attempts are made during an attack, the DOTS clientSHOULD<bcp14>SHOULD</bcp14> use a "Connection Attempt Delay" <xreftarget="RFC8305"></xref>target="RFC8305" format="default"/> set to 100 ms.</t> <t>Inreference to<xreftarget="fig_happy_eyeballs"></xref>,target="fig_happy_eyeballs" format="default"/>, the DOTS client proceeds with the connection attempts following the rules in <xreftarget="RFC8305"></xref>.target="RFC8305" format="default"/>. In this example, it is assumed that the IPv6 path is broken and UDP traffic is dropped by amiddleboxmiddlebox, but this has little impacttoon the DOTS client because there isnonot a long delay before using IPv4 and TCP.</t><t><figure anchor="fig_happy_eyeballs" title="DOTS<figure anchor="fig_happy_eyeballs"> <name>DOTS Happy Eyeballs (SampleFlow)">Flow)</name> <artworkalign="center"><![CDATA[align="center" name="" type="" alt=""><![CDATA[ +-----------+ +-----------+ |DOTSclient|Client| |DOTSserver|Server| +-----------+ +-----------+ | | T0 |--DTLS ClientHello, IPv6 ---->X | T1 |--DTLS ClientHello, IPv4 ---->X | T2 |--TCP SYN, IPv6-------------->X | T3 |--TCP SYN,IPv4--------------------------------------->|IPv4------------------------------------->| |<-TCPSYNACK-------------------------------------------|SYNACK-----------------------------------------| |--TCPACK--------------------------------------------->|ACK------------------------------------------->| |<------------Establish TLSSession-------------------->|Session------------------>| |----------------DOTSsignal--------------------------->|signal------------------------->| | | Note: * Retransmission messages are not shown. * T1-T0=T2-T1=T3-T2= Connection AttemptDelay.]]></artwork> </figure></t>Delay. ]]></artwork> </figure> <t>A single DOTS signal channel between DOTS agents can be used to exchange multiple DOTS signal messages. To reduce DOTS client and DOTS server workload, DOTS clientsSHOULD re-use<bcp14>SHOULD</bcp14> reuse the (D)TLS session.</t> </section> <section anchor="m_req"title="DOTSnumbered="true" toc="default"> <name>DOTS MitigationMethods">Methods</name> <t>The following methods are used by a DOTS client to request, withdraw, or retrieve the status of mitigationrequests:<list hangIndent="8" style="hanging"> <t hangText="PUT:">DOTSrequests:</t> <dl newline="false" spacing="normal" indent="10"> <dt>PUT:</dt> <dd>DOTS clients use the PUT method to request mitigation from a DOTS server (<xreftarget="post"></xref>).target="post" format="default"/>). During active mitigation, DOTS clients may use PUT requests to carry mitigation efficacy updates to the DOTS server (<xreftarget="put"></xref>).</t> <t hangText="GET:">DOTStarget="put" format="default"/>).</dd> <dt>GET:</dt> <dd>DOTS clients may use the GET method to subscribe to DOTS server statusmessages,messages or to retrieve the list of its mitigations maintained by a DOTS server (<xreftarget="get"></xref>).</t> <t hangText="DELETE:">DOTStarget="get" format="default"/>).</dd> <dt>DELETE:</dt> <dd>DOTS clients use the DELETE method to withdraw a request for mitigation from a DOTS server (<xreftarget="del"></xref>).</t> </list></t>target="del" format="default"/>).</dd> </dl> <t>Mitigation request and response messages are marked as Non-confirmable messages(Section 2.2 of <xref target="RFC7252"></xref>).</t>(<xref target="RFC7252" section="2.2" sectionFormat="of" format="default"/>).</t> <t>DOTS agentsMUST NOT<bcp14>MUST NOT</bcp14> send more than one UDP datagram per round-trip time (RTT) to the peer DOTS agent on average following the data transmission guidelines discussed inSection 3.1.3 of<xreftarget="RFC8085"></xref>.</t>target="RFC8085" section="3.1.3" sectionFormat="of" format="default"/>.</t> <t>Requests marked by the DOTS client as Non-confirmable messages are sent at regular intervals until a response is received from the DOTS server. If the DOTS client cannot maintain an RTT estimate, itMUST NOT<bcp14>MUST NOT</bcp14> send more than one Non-confirmable request every 3 seconds, andSHOULD<bcp14>SHOULD</bcp14> use an even less aggressive rate whenever possible (case 2 inSection 3.1.3 of<xreftarget="RFC8085"></xref>).target="RFC8085" section="3.1.3" sectionFormat="of" format="default"/>). Mitigation requestsMUST NOT<bcp14>MUST NOT</bcp14> be delayed because of checks on probing rate(Section 4.7 of <xref target="RFC7252"></xref>).</t>(<xref target="RFC7252" section="4.7" sectionFormat="of" format="default"/>).</t> <t>JSON encoding of YANGmodelledmodeled data <xreftarget="RFC7951"></xref>target="RFC7951" format="default"/> is used to illustrate the various methods defined in the followingsub-sections.subsections. Also, the examples use the Labels defined in Sections <xref format="counter"target="sc"></xref>,target="sc"/>, <xref format="counter"target="cs"></xref>,target="cs"/>, <xref format="counter"target="cc"></xref>,target="cc"/>, and <xref format="counter"target="as"></xref>.</t>target="as"/>.</t> <section anchor="post"title="Request Mitigation">numbered="true" toc="default"> <name>Request Mitigation</name> <t>When a DOTS client requires mitigation for some reason, the DOTS client uses the CoAP PUT method to send a mitigation request to its DOTS server(s) (Figures <xref format="counter"target="Figure1"></xref>target="Figure1"/> and <xref format="counter"target="Figure1c"></xref>).</t>target="Figure1c"/>).</t> <t>If a DOTS client is entitled to solicit the DOTS service, the DOTS server enables mitigation on behalf of the DOTS client by communicating the DOTS client's request to a mitigator (which may be co-located with the DOTS server) and relaying the feedback of the thus-selected mitigator to the requesting DOTS client.</t><t><figure anchor="Figure1" title="PUT<figure anchor="Figure1"> <name>PUT to Convey DOTS MitigationRequests"> <artwork align="left"><![CDATA[Requests</name> <sourcecode><![CDATA[ Header: PUT (Code=0.03) Uri-Path: ".well-known" Uri-Path: "dots" Uri-Path: "mitigate" Uri-Path: "cuid=dz6pHjaADkaFTbjr0JGBpw" Uri-Path: "mid=123" Content-Format: "application/dots+cbor" { ... }]]></artwork> </figure></t>]]></sourcecode> </figure> <t>The order of the Uri-Path options is important as it defines the CoAP resource. In particular, 'mid'MUST<bcp14>MUST</bcp14> follow 'cuid'.</t> <t>The additional Uri-Path parameters to those defined in <xreftarget="uri-path"></xref>target="uri-path" format="default"/> are as follows:</t><t><list hangIndent="6" style="hanging"> <t hangText="cuid:">Stands<dl newline="false" spacing="normal" indent="6"> <dt>cuid:</dt> <dd> <t>Stands for Client Unique Identifier. A globally unique identifier that is meant to prevent collisions among DOTS clients, especially those from the same domain. ItMUST<bcp14>MUST</bcp14> be generated by DOTSclients.<vspace blankLines="1" />Forclients.</t> <t>For the reasons discussed in <xreftarget="motiv"></xref>,target="motiv" format="default"/>, implementationsSHOULD<bcp14>SHOULD</bcp14> set 'cuid' using the following procedure: first, theDistinguished Encoding Rules (DER)-encoded Abstract Syntax Notation One (ASN.1)DOTS client inputs one of the following into the SHA-256 <xref target="RFC6234" format="default"/> cryptographic hash: the DER-encoded ASN.1 representation of the Subject Public Key Info (SPKI) ofthe DOTS clientits X.509 certificate <xreftarget="RFC5280"></xref>, the DOTS clienttarget="RFC5280" format="default"/>, its raw public key <xreftarget="RFC7250"></xref>,target="RFC7250" format="default"/>, the "Pre-Shared Key (PSK) identity"used by the DOTS clientit uses in the TLS 1.2 ClientKeyExchange message, or the "identity"used by the DOTS clientit uses in the "pre_shared_key" TLS 1.3extension is input to the SHA-256 <xref target="RFC6234"></xref> cryptographic hash.extension. Then, the output of the cryptographic hash algorithm is truncated to 16 bytes; truncation is done by stripping off the final 16 bytes. The truncated output is base64url encoded(Section 5 of <xref target="RFC4648"></xref>)(<xref target="RFC4648" section="5" sectionFormat="of" format="default"/>) with the trailing "=" removed from the encoding, and the resulting value used as the 'cuid'.<vspace blankLines="1" />The</t> <t>The 'cuid' is intended to be stable when communicating with a given DOTS server, i.e., the 'cuid' used by a DOTS clientSHOULD NOT<bcp14>SHOULD NOT</bcp14> change over time. Distinct 'cuid' valuesMAY<bcp14>MAY</bcp14> be used by a single DOTS client per DOTS server.<vspace blankLines="1" />If</t> <t>If a DOTS client has to change its 'cuid' for some reason, itMUST NOT<bcp14>MUST NOT</bcp14> do so when mitigations are still active for the old 'cuid'. The 'cuid'SHOULD<bcp14>SHOULD</bcp14> be 22 characters to avoid DOTS signal message fragmentation over UDP. Furthermore, if that DOTS client created aliases and filtering entries at the DOTS server by means of the DOTS data channel, itMUST<bcp14>MUST</bcp14> delete all the entries bound to the old 'cuid' andre-installreinstall them using the new'cuid'.<vspace blankLines="1" />DOTS'cuid'.</t> <t>DOTS serversMUST<bcp14>MUST</bcp14> return 4.09 (Conflict) error code to a DOTS peer to notify that the 'cuid' is alreadyin-usein use by another DOTS client. Upon receipt of that error code, a new 'cuid'MUST<bcp14>MUST</bcp14> be generated by the DOTS peer (e.g., using <xreftarget="RFC4122"></xref>). <vspace blankLines="1" />Client-domaintarget="RFC4122" format="default"/>). </t> <t>Client-domain DOTS gatewaysMUST<bcp14>MUST</bcp14> handle 'cuid' collision directly and it isRECOMMENDED<bcp14>RECOMMENDED</bcp14> that 'cuid' collision is handled directly by server-domain DOTSgateways.<vspace blankLines="1" />DOTSgateways.</t> <t>DOTS gatewaysMAY<bcp14>MAY</bcp14> rewrite the 'cuid' used by peer DOTS clients. Triggers for such rewriting are out of scope.<vspace blankLines="1" />This</t> <t>This is a mandatory Uri-Path parameter.</t><t hangText="mid:">Identifier</dd> <dt>mid:</dt> <dd> <t>Identifier for the mitigation request represented with an integer. This identifierMUST<bcp14>MUST</bcp14> be unique for each mitigation request bound to the DOTS client, i.e., the 'mid' parameter value in the mitigation request needs to be unique (per 'cuid' and DOTS server) relative to the 'mid' parameter values of active mitigation requests conveyed from the DOTS client to the DOTSserver.<vspace blankLines="1" />Inserver.</t> <t>In order to handle out-of-order delivery of mitigation requests, 'mid' valuesMUST<bcp14>MUST</bcp14> increase monotonically.<vspace blankLines="1" />If</t> <t>If the 'mid' value has reached 3/4 of(2**32(2<sup>32</sup> - 1) (i.e., 3221225471) and no attack is detected, the DOTS clientMUST<bcp14>MUST</bcp14> reset 'mid' to 0 to handle 'mid' rollover. If the DOTS client maintains mitigation requests withpre-configuredpreconfigured scopes, itMUST re-create<bcp14>MUST</bcp14> recreate them with the 'mid' restarting at 0.<vspace blankLines="1" />This</t> <t>This identifierMUST<bcp14>MUST</bcp14> be generated by the DOTSclient.<vspace blankLines="1" />Thisclient.</t> <t>This is a mandatory Uri-Path parameter.</t></list></t></dd> </dl> <t>'cuid' and 'mid'MUST NOT<bcp14>MUST NOT</bcp14> appear in the PUT request message body (<xreftarget="Figure1c"></xref>).target="Figure1c" format="default"/>). The schema in <xreftarget="Figure1c"></xref>target="Figure1c" format="default"/> uses the types defined in <xreftarget="mapping"></xref>.target="mapping" format="default"/>. Note that this figure (and other similar figures depicting a schema) are non-normative sketches of the structure of the message.</t><t><figure anchor="Figure1c" title="PUT<figure anchor="Figure1c"> <name>PUT to Convey DOTS Mitigation Requests (Message BodySchema)"> <artwork align="left"><![CDATA[Schema)</name> <sourcecode><![CDATA[ { "ietf-dots-signal-channel:mitigation-scope": { "scope": [ { "target-prefix": [ "string" ], "target-port-range": [ { "lower-port": number, "upper-port": number } ], "target-protocol": [ number ], "target-fqdn": [ "string" ], "target-uri": [ "string" ], "alias-name": [ "string" ], "lifetime": number, "trigger-mitigation": true|false } ] } }]]></artwork> </figure></t>]]></sourcecode> </figure> <t>The parameters in the CBOR body (<xreftarget="Figure1c"></xref>)target="Figure1c" format="default"/>) of the PUT request are described below:</t><t><list style="hanging"> <t hangText="target-prefix:">A<dl newline="false" spacing="normal"> <dt>target-prefix:</dt> <dd> <t>A list of prefixes identifying resources under attack. Prefixes are represented using Classless Inter-Domain Routing (CIDR) notation <xreftarget="RFC4632"></xref>. <vspace blankLines="0" />Astarget="RFC4632" format="default"/>. </t> <t>As a reminder, the prefix length must be less than or equal to 32 (or 128) for IPv4 (orIPv6).<vspace blankLines="1" />TheIPv6).</t> <t>The prefix listMUST NOT<bcp14>MUST NOT</bcp14> include broadcast, loopback, or multicast addresses. These addresses are consideredasto be invalid values. In addition, the DOTS serverMUST<bcp14>MUST</bcp14> validate that target prefixes are within the scope of the DOTS client domain. Other validation checks may be supported by DOTSservers.<vspace blankLines="1" />Thisservers.</t> <t>This is an optional attribute.</t><t hangText="target-port-range:">A</dd> <dt>target-port-range:</dt> <dd> <t>A list of port numbers bound to resources under attack.<vspace blankLines="1" />A</t> <t>A port range is defined by two bounds, a lower port number(lower-port)('lower-port') and an upper port number(upper-port).('upper-port'). When only 'lower-port' is present, it represents a single port number.<vspace blankLines="1" />For</t> <t>For TCP, UDP, Stream Control Transmission Protocol (SCTP) <xreftarget="RFC4960"></xref>,target="RFC4960" format="default"/>, or Datagram Congestion Control Protocol (DCCP) <xreftarget="RFC4340"></xref>,target="RFC4340" format="default"/>, a range of ports can be, for example, 0-1023, 1024-65535, or 1024-49151.<vspace blankLines="1" />This</t> <t>This is an optional attribute.</t><t hangText="target-protocol:">A</dd> <dt>target-protocol:</dt> <dd> <t>A list of protocols involved in an attack. Values are taken from the IANA protocol registry <xreftarget="proto_numbers"></xref>. <vspace blankLines="1" />Iftarget="IANA-Proto" format="default"/>. </t> <t>If 'target-protocol' is not specified, then the request applies to any protocol.<vspace blankLines="1" />This</t> <t>This is an optional attribute.</t><t hangText="target-fqdn: ">A</dd> <dt>target-fqdn: </dt> <dd> <t>A list of Fully Qualified Domain Names (FQDNs) identifying resources under attack <xreftarget="RFC8499"></xref>.<vspace blankLines="1" />Howtarget="RFC8499" format="default"/>.</t> <t>How a name is passed to an underlying name resolution library isimplementation-implementation anddeployment-specific.deployment specific. Nevertheless, once the name is resolved into one or multiple IP addresses, DOTS serversMUST<bcp14>MUST</bcp14> apply the same validation checks as those for'target-prefix'.<vspace blankLines="1" />The'target-prefix'.</t> <t>The use of FQDNs may be suboptimalbecause:<list style="symbols"> <t>Itbecause:</t> <ul spacing="normal"> <li>It induces both an extra load and increased delays on the DOTS server to handle and manage DNS resolutionrequests.</t> <t>Itrequests.</li> <li>It does not guarantee that the DOTS server will resolve a name to the same IP addresses that the DOTS clientdoes.</t> </list><vspace blankLines="1" />Thisdoes.</li> </ul> <t>This is an optional attribute.</t><t hangText="target-uri: ">A</dd> <dt>target-uri: </dt> <dd> <t>A list ofUniform Resource Identifiers (URIs)URIs <xreftarget="RFC3986"></xref>target="RFC3986" format="default"/> identifying resources under attack.<vspace blankLines="1" />The</t> <t>The same validation checks used for 'target-fqdn'MUST<bcp14>MUST</bcp14> be followed by DOTS servers to validate a target URI.<vspace blankLines="1" />This</t> <t>This is an optional attribute.</t><t hangText="alias-name:">A</dd> <dt>alias-name:</dt> <dd> <t>A list of aliases of resources for which the mitigation is requested. Aliases can be created using the DOTS data channel(Section 6.1 of <xref target="I-D.ietf-dots-data-channel"></xref>),(<xref target="RFC8783" section="6.1" sectionFormat="of" format="default"/>), direct configuration, or other means.<vspace blankLines="1" />An</t> <t>An alias is used in subsequent signal channel exchanges to refer more efficiently to the resources underattack.<vspace blankLines="1" />Thisattack.</t> <t>This is an optional attribute.</t><t hangText="lifetime: ">Lifetime</dd> <dt>lifetime: </dt> <dd> <t>Lifetime of the mitigation request in seconds. TheRECOMMENDED<bcp14>RECOMMENDED</bcp14> lifetime of a mitigation request is 3600seconds --seconds: this value was chosen to be long enough so that refreshing is not typically a burden on the DOTS client, while still making the request expire in a timely manner when the client has unexpectedly quit. DOTS clientsMUST<bcp14>MUST</bcp14> include this parameter in their mitigation requests. Upon the expiry of this lifetime, and if the request is not refreshed, the mitigation request is removed. The request can be refreshed by sending the same request again.<vspace blankLines="1" />A</t> <t>A lifetime of '0' in a mitigation request is an invalid value.<vspace blankLines="1" />A</t> <t>A lifetime of negative one (-1) indicates indefinite lifetime for the mitigation request. The DOTS serverMAY<bcp14>MAY</bcp14> refuse an indefinite lifetime, for policy reasons; the granted lifetime value is returned in the response. DOTS clientsMUST<bcp14>MUST</bcp14> be prepared to not be granted mitigations with indefinitelifetimes.<vspace blankLines="1" />Thelifetimes.</t> <t>The DOTS serverMUST<bcp14>MUST</bcp14> always indicate the actual lifetime in the response and the remaining lifetime in status messages sent to the DOTS client.<vspace blankLines="1" />This</t> <t>This is a mandatory attribute.</t><t hangText="trigger-mitigation: ">If</dd> <dt>trigger-mitigation: </dt> <dd> <t>If the parameter value is set to 'false', DDoS mitigation will not be triggered for the mitigation request unless the DOTS signal channel session is lost.<vspace blankLines="1" />If</t> <t>If the DOTS client ceases to respond to heartbeat messages, the DOTS server can detect that the DOTS signal channel session is lost. More details are discussed in <xreftarget="hb"></xref>.<vspace blankLines="1" />Thetarget="hb" format="default"/>.</t> <t>The default value of the parameter is 'true' (that is, the mitigation starts immediately). If 'trigger-mitigation' is not present in a request, this is equivalent to receiving a request with 'trigger-mitigation' set to 'true'.<vspace blankLines="1" />This</t> <t>This is an optional attribute.</t></list></t></dd> </dl> <t>In deployments where server-domain DOTS gateways are enabled, identity information about the origin source client domain ('cdid')SHOULD<bcp14>SHOULD</bcp14> be propagated to the DOTS server. That information is meant to assist the DOTS serverto enforcein enforcing some policies such as grouping DOTS clients that belong to the same DOTS domain, limiting the number of DOTS requests, and identifying the mitigation scope. These policies can be enforcedper-client, per-clientper client, per client domain, or both. Also, the identity information may be used for auditing and debugging purposes.</t> <t><xreftarget="Figure1a"></xref>target="Figure1a" format="default"/> shows an example of a request relayed by a server-domain DOTS gateway.</t><t><figure anchor="Figure1a" title="PUT<figure anchor="Figure1a"> <name>PUT for DOTS Mitigation Request as Relayed by a DOTSGateway"> <artwork align="left"><![CDATA[Gateway</name> <sourcecode><![CDATA[ Header: PUT (Code=0.03) Uri-Path: ".well-known" Uri-Path: "dots" Uri-Path: "mitigate" Uri-Path: "cdid=7eeaf349529eb55ed50113" Uri-Path: "cuid=dz6pHjaADkaFTbjr0JGBpw" Uri-Path: "mid=123" Content-Format: "application/dots+cbor" { ... }]]></artwork> </figure></t>]]></sourcecode> </figure> <t>A server-domain DOTS gatewaySHOULD<bcp14>SHOULD</bcp14> add the following Uri-Path parameter:</t><t><list hangIndent="6" style="hanging"> <t hangText="cdid:">Stands<dl newline="false" spacing="normal" indent="6"> <dt>cdid:</dt> <dd> <t>Stands for Client Domain Identifier. The 'cdid' is conveyed by a server-domain DOTS gateway to propagate the source domain identity from the gateway'sclient-facing-sideclient-facing side to the gateway'sserver-facing-side,server-facing side, and from the gateway'sserver-facing-sideserver-facing side to the DOTS server. 'cdid' may be used by the final DOTS server for policy enforcement purposes (e.g., enforce a quota on filtering rules). These policies aredeployment-specific. <vspace blankLines="1" />Server-domaindeployment specific. </t> <t>Server-domain DOTS gatewaysSHOULD<bcp14>SHOULD</bcp14> support a configuration option to instruct whether 'cdid' parameter is to be inserted.<vspace blankLines="1" />In</t> <t>In order to accommodate deployments that require enforcing per-client policies, per-client domain policies, or a combination thereof, server-domain DOTS gateways instructed to insert the 'cdid' parameterMUST<bcp14>MUST</bcp14> supply the SPKI hash of the DOTS client X.509 certificate, the DOTS client raw public key, or the hash of the "PSK identity" in the 'cdid', following the same rules for generating the hash conveyed in 'cuid', which is then used by the ultimate DOTS server to determine the corresponding client's domain. The 'cdid' generated by a server-domain gateway is likely to be the same as the 'cuid' exceptifthe case in which the DOTS message was relayed by a client-domain DOTS gateway or the 'cuid' was generated from a rogue DOTS client.<vspace blankLines="1" />If</t> <t>If a DOTS client is provisioned, for example, with distinct certificates as a function of the peer server-domain DOTS gateway, distinct 'cdid' values may be supplied by a server-domain DOTS gateway. The ultimate DOTS serverMUST<bcp14>MUST</bcp14> treat those 'cdid' values as equivalent.<vspace blankLines="1" />The</t> <t>The 'cdid' attributeMUST NOT<bcp14>MUST NOT</bcp14> be generated and included by DOTS clients.<vspace blankLines="1" />DOTS</t> <t>DOTS serversMUST<bcp14>MUST</bcp14> ignore 'cdid' attributes that are directly supplied by source DOTS clients or client-domain DOTS gateways. This implies that first server-domain DOTS gatewaysMUST<bcp14>MUST</bcp14> strip 'cdid' attributes supplied by DOTS clients. DOTS serversSHOULD<bcp14>SHOULD</bcp14> support a configuration parameter to identify DOTS gateways that are trusted to supply 'cdid'attributes.<vspace blankLines="1" />Onlyattributes.</t> <t>Only single-valued 'cdid' are defined in this document. That is, only the first on-path server-domain DOTS gateway can insert a 'cdid' value. This specification does not allow multiple server-domain DOTS gateways, whenever involved in the path, to insert a 'cdid' value for each server-domain gateway.<vspace blankLines="1" />This</t> <t>This is an optional Uri-Path. When present, 'cdid'MUST<bcp14>MUST</bcp14> be positioned before 'cuid'.</t></list></t></dd> </dl> <t>A DOTS gatewaySHOULD<bcp14>SHOULD</bcp14> add the CoAP Hop-LimitOptionoption <xreftarget="I-D.ietf-core-hop-limit"></xref>.</t>target="RFC8768" format="default"/>.</t> <t>Because of the complexityto handleof handling partial failure cases, this specification does not allowfor includingthe inclusion of multiple mitigation requests in the same PUT request. Concretely, a DOTS clientMUST NOT<bcp14>MUST NOT</bcp14> include multiple entries in the 'scope' array of the same PUT request.</t> <t>FQDN and URI mitigation scopes may be thought of as a form of scope alias, in which the addresses associated with the domain name or URI (as resolved by the DOTS server) represent the scope of the mitigation. Particularly, the IP addresses to which the host subcomponent of authority component ofana URI resolves represent the 'target-prefix', the URI scheme represents the 'target-protocol', the port subcomponent of authority component ofana URI represents the 'target-port-range'. If the optional port information is not present in the authority component, the default port defined for the URI scheme represents the 'target-port'.</t> <t>In the PUTrequestrequest, at least one of the attributes 'target-prefix', 'target-fqdn','target-uri', or 'alias-name'MUST<bcp14>MUST</bcp14> be present.</t> <t>Attributes and Uri-Path parameters with empty valuesMUST NOT<bcp14>MUST NOT</bcp14> be present in a requestandas an empty value will render the entire requestinvalid.</t> <t><xref target="Figure2"></xref>invalid. </t> <t> <xref target="Figure2" format="default"/> shows a PUT request example to signal that servers 2001:db8:6401::1 and 2001:db8:6401::2 are receiving attack traffic on TCP port numbers 80, 8080, and443 used by 2001:db8:6401::1 and 2001:db8:6401::2 servers are under attack.443. The presence of 'cdid' indicates that a server-domain DOTS gateway has modified the initial PUT request sent by the DOTS client. Note that 'cdid'MUST NOT<bcp14>MUST NOT</bcp14> appear in the PUT request message body.</t><t><figure anchor="Figure2" title="PUT<figure anchor="Figure2"> <name>PUT for DOTS Mitigation Request (AnExample)"> <artwork align="left"><![CDATA[Example)</name> <sourcecode><![CDATA[ Header: PUT (Code=0.03) Uri-Path: ".well-known" Uri-Path: "dots" Uri-Path: "mitigate" Uri-Path: "cdid=7eeaf349529eb55ed50113" Uri-Path: "cuid=dz6pHjaADkaFTbjr0JGBpw" Uri-Path: "mid=123" Content-Format: "application/dots+cbor" { "ietf-dots-signal-channel:mitigation-scope": { "scope": [ { "target-prefix": [ "2001:db8:6401::1/128", "2001:db8:6401::2/128" ], "target-port-range": [ { "lower-port": 80 }, { "lower-port": 443 }, { "lower-port": 8080 } ], "target-protocol": [ 6 ], "lifetime": 3600 } ] } }]]></artwork> </figure></t>]]></sourcecode> </figure> <t>The corresponding CBOR encoding format for the payload is shown in <xreftarget="Figure2a"></xref>.</t> <t><figure anchor="Figure2a" title="PUTtarget="Figure2a" format="default"/>.</t> <figure anchor="Figure2a"> <name>PUT for DOTS Mitigation Request(CBOR)"> <artwork align="left"><![CDATA[A1(CBOR)</name> <sourcecode><![CDATA[ A1 # map(1) 01 # unsigned(1) A1 # map(1) 02 # unsigned(2) 81 # array(1)A3A4 #map(3)map(4) 06 # unsigned(6) 82 # array(2) 74 # text(20) 323030313A6462383A363430313A3A312F313238 74 # text(20) 323030313A6462383A363430313A3A322F313238 07 # unsigned(7) 83 # array(3) A1 # map(1) 08 # unsigned(8) 18 50 # unsigned(80) A1 # map(1) 08 # unsigned(8) 19 01BB # unsigned(443) A1 # map(1) 08 # unsigned(8) 19 1F90 # unsigned(8080) 0A # unsigned(10) 81 # array(1) 06 # unsigned(6) 0E # unsigned(14) 19 0E10 # unsigned(3600)]]></artwork> </figure></t>]]></sourcecode> </figure> <t>In both DOTS signal and data channel sessions, the DOTS clientMUST<bcp14>MUST</bcp14> authenticate itself to the DOTS server (<xreftarget="mutauth"></xref>).target="mutauth" format="default"/>). The DOTS serverMAY<bcp14>MAY</bcp14> use the algorithm presented inSection 7 of<xreftarget="RFC7589"></xref>target="RFC7589" section="7" sectionFormat="of" format="default"/> to derive the DOTS client identity or username from the client certificate. The DOTS client identity allows the DOTS server to accept mitigation requests with scopes that the DOTS client is authorized to manage.</t> <t>The DOTS server couples the DOTS signal and data channel sessions using the DOTS client identity and optionally the 'cdid' parameter value, so the DOTS server can validate whether the aliases conveyed in the mitigation request were indeed created by the same DOTS client using the DOTS data channel session. If the aliases were not created by the DOTS client, the DOTS serverMUST<bcp14>MUST</bcp14> return 4.00 (Bad Request) in the response.</t> <t>The DOTS server couples the DOTS signal channel sessions using the DOTS client identity and optionally the 'cdid' parameter value, and the DOTS server uses 'mid' and 'cuid' Uri-Path parameter values to detect duplicate mitigation requests. If the mitigation request contains the 'alias-name' and other parameters identifying the target resources (such as 'target-prefix', 'target-port-range', 'target-fqdn', or 'target-uri'), the DOTS server appends the parameter values in 'alias-name' with the corresponding parameter values in 'target-prefix', 'target-port-range', 'target-fqdn', or 'target-uri'.</t> <t>The DOTS server indicates the result of processing the PUT request using CoAPresponse codes.Response Codes. CoAP 2.xx codes are success. CoAP 4.xx codes are some sort of invalid requests (client errors). COAP 5.xx codes are returned if the DOTS server is in an error state or is currently unavailable to provide mitigation in response to the mitigation request from the DOTS client.</t> <t><xreftarget="put_response"></xref>target="put_response" format="default"/> shows an example response to a PUT request that is successfully processed by a DOTS server (i.e., CoAP 2.xxresponse codes).Response Codes). This version of the specification forbids 'cuid' and 'cdid' (if used) to be returned in a response message body.</t><t><figure anchor="put_response" title="2.xx<figure anchor="put_response"> <name>2.xx ResponseBody"> <artwork align="left"><![CDATA[{Body</name> <sourcecode><![CDATA[ { "ietf-dots-signal-channel:mitigation-scope": { "scope": [ { "mid": 123, "lifetime": 3600 } ] }}]]></artwork> </figure></t>} ]]></sourcecode> </figure> <t>If the request is missing a mandatory attribute, does not include 'cuid' or 'mid' Uri-Path options, includes multiple 'scope' parameters, or contains invalid or unknown parameters, the DOTS serverMUST<bcp14>MUST</bcp14> reply with 4.00 (Bad Request). DOTS agents can safely ignore comprehension-optional parameters they don't understand (<xreftarget="format"></xref>).</t>target="format" format="default"/>).</t> <t>A DOTS server that receives a mitigation request with alifetime'lifetime' set to '0'MUST<bcp14>MUST</bcp14> reply with a 4.00 (Bad Request).</t> <t>If the DOTS server does not find the 'mid' parameter value conveyed in the PUT request in its configuration data, itMAY<bcp14>MAY</bcp14> accept the mitigation request by sending back a 2.01 (Created) response to the DOTS client; the DOTS server will consequently try to mitigate the attack. A DOTS server could reject mitigation requests when it is near capacity or needs to rate-limit a particular client, for example.</t> <t>The relative order of two mitigationrequests, having therequests with the same 'trigger-mitigation'type,type from a DOTS client is determined by comparing their respective 'mid' values. If two mitigation requests with the same 'trigger-mitigation' type have overlapping mitigation scopes, the mitigation request with the highest numeric 'mid' value will override the other mitigation request. Two mitigation requests from a DOTS client have overlapping scopes if there is a common IP address, IP prefix, FQDN, URI, oralias-name.alias. To avoid maintaining a long list of overlapping mitigation requests (i.e., requests with the same 'trigger-mitigation' type and overlapping scopes) from a DOTS client and to avoid error-prone provisioning of mitigation requests from a DOTS client, the overlapped lower numeric 'mid'MUST<bcp14>MUST</bcp14> be automatically deleted and no longer available at the DOTS server. For example, if the DOTS server receives a mitigation requestwhichthat overlaps with an existing mitigation with a higher numeric 'mid', the DOTS server rejects the request by returning 4.09 (Conflict) to the DOTS client. The response includes enough information for a DOTS client to recognize the source of the conflict as described below in the 'conflict-information' subtree with only the relevant nodes listed:</t><t hangText="status:"><list style="hanging"> <t hangText="conflict-information:">Indicates<dl newline="false" spacing="normal"> <dt>conflict-information:</dt> <dd> <t>Indicates that a mitigation request is conflicting with another mitigation request. This optional attribute has the following structure:<list style="hanging"> <t hangText="conflict-cause:">Indicates</t> <dl newline="false" spacing="normal"> <dt>conflict-cause:</dt> <dd> <t>Indicates the cause of the conflict. The following values aredefined:<list style="format %d:"> <t>Overlappingdefined:</t> <dl spacing="normal"> <dt>1:</dt> <dd>Overlapping targets. 'conflict-scope' provides more details about the conflicting targetclauses.</t> </list></t> <t hangText="conflict-scope:">Characterizesclauses.</dd> </dl> </dd> <dt>conflict-scope:</dt> <dd>Characterizes the exact conflict scope. It may include a list of IP addresses, a list of prefixes, a list of port numbers, a list of target protocols, a list of FQDNs, a list of URIs, a list ofalias-names,aliases, or a'mid'.</t> </list></t> </list></t>'mid'. </dd> </dl> </dd> </dl> <t>If the DOTS server receives a mitigation requestwhichthat overlaps with an active mitigation request, but bothhavinghave distinct 'trigger-mitigation' types, the DOTS serverSHOULD<bcp14>SHOULD</bcp14> deactivate (absent explicit policy/configuration otherwise) the mitigation request with 'trigger-mitigation' set tofalse.'false'. Particularly, if the mitigation request with 'trigger-mitigation' set tofalse'false' is active, the DOTS server withdraws the mitigation request (i.e., status code is set to '7' as defined in <xreftarget="status"></xref>)target="status" format="default"/>) and transitions the status of the mitigation request to '8'.</t> <t>Upon DOTS signal channel session loss with a peer DOTS client, the DOTS serverSHOULD<bcp14>SHOULD</bcp14> withdraw (absent explicit policy/configuration otherwise) any active mitigation requestsoverlappingthat overlap with mitigation requests having 'trigger-mitigation' set tofalse'false' from that DOTS client, as the loss of the session implicitly activates these preconfigured mitigationrequestsrequests, and they take precedence. Note that the active-but-terminating period is not observed for mitigations withdrawn at the initiative of the DOTS server.</t> <t>DOTS clients may adopt various strategies for setting the scopes of immediate andpre-configuredpreconfigured mitigation requests to avoid potential conflicts. For example, a DOTS client may tweakpre-configuredpreconfigured scopes so that the scope of any overlapping immediate mitigation request will be a subset of thepre-configuredpreconfigured scopes. Also, if an immediate mitigation request overlaps with any of thepre-configuredpreconfigured scopes, the DOTS client sets the scope of the overlapping immediate mitigation request to be a subset of thepre-configuredpreconfigured scopes, so as to get a broad mitigation when the DOTS signal channel collapses and to maximize the chance of recovery.</t> <t>If the requestis conflictingconflicts with an existing mitigation request from a different DOTS client, the DOTS server may return 2.01 (Created) or 4.09 (Conflict) to the requesting DOTS client. If the DOTS server decides to maintain the new mitigation request, the DOTS server returns 2.01 (Created) to the requesting DOTS client. If the DOTS server decides to reject the new mitigation request, the DOTS server returns 4.09 (Conflict) to the requesting DOTS client. For both 2.01 (Created) and 4.09 (Conflict) responses, the response includes enough information for a DOTS client to recognize the source of the conflict as described below:</t><t hangText="status:"><list style="hanging"> <t hangText="conflict-information:">Indicates<dl newline="false" spacing="normal"> <dt>conflict-information:</dt> <dd> <t>Indicates that a mitigation request is conflicting with another mitigation request(s) from other DOTS client(s). This optional attribute has the following structure:<list style="hanging"> <t hangText="conflict-status:">Indicates</t> <dl newline="false" spacing="normal"> <dt>conflict-status:</dt> <dd> <t>Indicates the status of a conflicting mitigation request. The following values aredefined:<list style="format %d:"> <t>DOTSdefined:</t> <dl spacing="normal"> <dt>1:</dt> <dd>DOTS server has detected conflicting mitigation requests from different DOTS clients. This mitigation request is currently inactive until the conflicts are resolved. Another mitigation request isactive.</t> <t>DOTSactive.</dd> <dt>2:</dt> <dd>DOTS server has detected conflicting mitigation requests from different DOTS clients. This mitigation request is currentlyactive.</t> <t>DOTSactive.</dd> <dt>3:</dt> <dd>DOTS server has detected conflicting mitigation requests from different DOTS clients. All conflicting mitigation requests areinactive.</t> </list></t> <t hangText="conflict-cause:">Indicatesinactive.</dd> </dl> </dd> <dt>conflict-cause:</dt> <dd> <t>Indicates the cause of the conflict. The following values aredefined:<list style="format %d:"> <t>Overlappingdefined:</t> <dl spacing="normal"> <dt>1:</dt> <dd>Overlapping targets. 'conflict-scope' provides more details about the conflicting targetclauses.</t> <t>Conflictsclauses.</dd> <dt>2:</dt> <dd>Conflicts with an existing accept-list. This code is returned when the DDoS mitigation detects source addresses/prefixes in the accept-listed ACLs are attacking thetarget.</t> <t>CUIDtarget.</dd> <dt>3:</dt> <dd>CUID Collision. This code is returned when a DOTS client uses a 'cuid' that is already used by another DOTS client. This code is an indication that the request has been rejected and a new request with a new 'cuid' is to be re-sent by the DOTS client (see the example shown in <xreftarget="newcuid"></xref>).target="newcuid" format="default"/>). Note that 'conflict-status', 'conflict-scope', and 'retry-timer'MUST NOT<bcp14>MUST NOT</bcp14> be returned in the errorresponse.</t> </list></t> <t hangText="conflict-scope:">Characterizesresponse.</dd> </dl> </dd> <dt>conflict-scope:</dt> <dd>Characterizes the exact conflict scope. It may include a list of IP addresses, a list of prefixes, a list of port numbers, a list of target protocols, a list of FQDNs, a list of URIs, a list ofalias-names,aliases, or references to conflicting ACLs (by an 'acl-name', typically <xreftarget="I-D.ietf-dots-data-channel"></xref>).</t> <t hangText="retry-timer:">Indicates,target="RFC8783" format="default"/>).</dd> <dt>retry-timer:</dt> <dd> <t>Indicates, in seconds, the time after which the DOTS client mayre-issuereissue the same request. The DOTS server returns 'retry-timer' only to DOTS client(s) for which a mitigation request is deactivated. Any retransmission of the same mitigation request before the expiry of this timer is likely to be rejected by the DOTS server for the samereasons.<vspace blankLines="1" />The retry-timer SHOULDreasons.</t> <t>The 'retry-timer' <bcp14>SHOULD</bcp14> be equal to the lifetime of the active mitigation request resulting in the deactivation of the conflicting mitigation request.<vspace blankLines="1" />If</t> <t>If the DOTS server decides to maintain a state for the deactivated mitigation request, the DOTS server updates the lifetime of the deactivated mitigation request to 'retry-timer + 45 seconds' (that is, this mitigation request remains deactivated for the entire duration of 'retry-timer + 45 seconds') so that the DOTS client can refresh the deactivated mitigation request after 'retry-timer' seconds, but before the expiry of the lifetime, and check if the conflict is resolved.</t></list></t> </list></t> <t hangText="conflict-information:"><figure align="center" anchor="newcuid" title="Example</dd> </dl> </dd> </dl> <figure anchor="newcuid"> <name>Example of Generating a New'cuid'"> <artwork><![CDATA['cuid'</name> <sourcecode><![CDATA[ Header: PUT (Code=0.03) Uri-Path: ".well-known" Uri-Path: "dots" Uri-Path: "mitigate" Uri-Path: "cuid=7eeaf349529eb55ed50113" Uri-Path: "mid=12" (1) Request with a conflicting 'cuid' { "ietf-dots-signal-channel:mitigation-scope": { "scope": [ { "conflict-information": { "conflict-cause": "cuid-collision" } } ] } } (2) Message body of the 4.09 (Conflict) response from the DOTS server Header: PUT (Code=0.03) Uri-Path: ".well-known" Uri-Path: "dots" Uri-Path: "mitigate" Uri-Path: "cuid=f30d281ce6b64fc5a0b91e" Uri-Path: "mid=12" (3) Request with a new'cuid']]></artwork> </figure></t> <t hangText="conflict-information:">As'cuid']]></sourcecode> </figure> <t>As an active attack evolves, DOTS clients can adjust the scope of requested mitigation as necessary, by refining the scope of resources requiring mitigation. This can be achieved by sending a PUT request with a new 'mid' value that will override the existing one with overlapping mitigation scopes.</t><t hangText="conflict-information:">For<t>For a mitigation request to continue beyond the initial negotiated lifetime, the DOTS client has to refresh the current mitigation request by sending a new PUT request. This PUT requestMUST<bcp14>MUST</bcp14> use the same 'mid' value, andMUSTit <bcp14>MUST</bcp14> repeat all the other parameters as sent in the original mitigation request apart from a possible change to thelifetime'lifetime' parameter value. In such a case, the DOTS serverMAY<bcp14>MAY</bcp14> update the mitigation request, and a 2.04 (Changed) response is returned to indicate a successful update of the mitigation request. If this is not the case, the DOTS serverMUST<bcp14>MUST</bcp14> reject the request with a 4.00 (Bad Request).</t> </section> <section anchor="get"title="Retrievenumbered="true" toc="default"> <name>Retrieve Information Related to aMitigation">Mitigation</name> <t>A GET request is used by a DOTS client to retrieve information (including status) of DOTS mitigations from a DOTS server.</t> <t>'cuid' is a mandatory Uri-Path parameter for GET requests.</t> <t>Uri-Path parameters with empty valuesMUST NOT<bcp14>MUST NOT</bcp14> be present in a request.</t> <t>The same considerations for manipulating the 'cdid' parameter by server-domain DOTS gateways specified in <xreftarget="post"></xref> MUSTtarget="post" format="default"/> <bcp14>MUST</bcp14> be followed for GET requests.</t> <t>The 'c' Uri-Query option is used to control selection of configuration and non-configuration data nodes. Concretely, the 'c' (content) parameter and its permitted values defined inthe following table<xreftarget="I-D.ietf-core-comi"></xref>target="tab-option-controls" format="default"/> <xref target="I-D.ietf-core-comi" format="default"/> can be used to retrieve non-configuration data (attack mitigation status), configuration data, or both. The DOTS serverMAY<bcp14>MAY</bcp14> support this optional filtering capability. It can safely ignore it if not supported. If the DOTS client supports the optional filtering capability, itSHOULD<bcp14>SHOULD</bcp14> use "c=n" query (to get back only the dynamically changing data) or "c=c" query (to get back the static configuration values) when the DDoS attack is active to limit the size of the response.</t><texttable> <ttcol>Value</ttcol> <ttcol>Description</ttcol> <c>c</c> <c>Return<table anchor="tab-option-controls" align="center"> <name>Permitted Values of the 'c' Parameter</name> <thead> <tr> <th align="left">Value</th> <th align="left">Description</th> </tr> </thead> <tbody> <tr> <td align="left">c</td> <td align="left">Return only configuration descendant datanodes</c> <c>n</c> <c>Returnnodes</td> </tr> <tr> <td align="left">n</td> <td align="left">Return only non-configuration descendant datanodes</c> <c>a</c> <c>Returnnodes</td> </tr> <tr> <td align="left">a</td> <td align="left">Return all descendant datanodes</c> </texttable>nodes</td> </tr> </tbody> </table> <t>The DOTS client can useBlock-wiseblock-wise transfer <xreftarget="RFC7959"></xref>target="RFC7959" format="default"/> to get the list of all its mitigations maintained by a DOTS server, it can send a Block2 Option in a GET request with NUM = 0 to aid in limiting the size of the response. If the representation of all the active mitigation requests associated with the DOTS client does not fit within a single datagram, the DOTS serverMUST<bcp14>MUST</bcp14> use the Block2 Option with NUM = 0 in the GET response. The Size2 Option may be conveyed in the response to indicate the total size of the resource representation. The DOTS client retrieves the rest of the representation by sending additional GET requests with Block2 Options containing NUM values greater than zero. The DOTS clientMUST<bcp14>MUST</bcp14> adhere to the block size preferences indicated by the DOTS server in the response. If the DOTS server uses the Block2 Option in the GETresponseresponse, and the response is for a dynamically changing resource (e.g., "c=n" or "c=a" query), the DOTS serverMUST<bcp14>MUST</bcp14> include the ETag Option in the response. The DOTS clientMUST<bcp14>MUST</bcp14> include the same ETag value in subsequent GET requests to retrieve the rest of the representation.</t> <t>The following examples illustrate how a DOTS client retrieves active mitigation requests from a DOTS server. In particular:<list style="symbols"> <t><xref target="Figure4"></xref></t> <ul spacing="normal"> <li> <xref target="Figure4" format="default"/> shows the example of a GET request to retrieve all DOTS mitigation requests signaled by a DOTSclient.</t> <t><xref target="Figure4a"></xref>client.</li> <li> <xref target="Figure4a" format="default"/> shows the example of a GET request to retrieve a specific DOTS mitigation request signaled by a DOTS client. The configuration data to be reported in the response is formatted in the same order as it was processed by the DOTS server in the original mitigationrequest.</t> </list></t>request.</li> </ul> <t>These two examples assume the default of "c=a"; that is, the DOTS client asks for all data to be reported by the DOTS server.</t> <figureanchor="Figure4" title="GETanchor="Figure4"> <name>GET to RetrieveallAll DOTS MitigationRequests"> <artwork align="left"><![CDATA[Requests</name> <sourcecode><![CDATA[ Header: GET (Code=0.01) Uri-Path: ".well-known" Uri-Path: "dots" Uri-Path: "mitigate" Uri-Path: "cuid=dz6pHjaADkaFTbjr0JGBpw" Observe:0]]></artwork>0 ]]></sourcecode> </figure><t><figure anchor="Figure4a" title="GET<figure anchor="Figure4a"> <name>GET to Retrieve a Specific DOTS MitigationRequest"> <artwork align="left"><![CDATA[Request</name> <sourcecode><![CDATA[ Header: GET (Code=0.01) Uri-Path: ".well-known" Uri-Path: "dots" Uri-Path: "mitigate" Uri-Path: "cuid=dz6pHjaADkaFTbjr0JGBpw" Uri-Path: "mid=12332" Observe: 0]]></artwork> </figure></t>]]></sourcecode> </figure> <t>If the DOTS server does not find the 'mid' Uri-Path value conveyed in the GET request in its configuration data for the requesting DOTS client, itMUST<bcp14>MUST</bcp14> respond with a 4.04 (Not Found) errorresponse code.Response Code. Likewise, the same errorMUST<bcp14>MUST</bcp14> be returned as a response to a request to retrieve all mitigation records (i.e., 'mid' Uri-Path is not defined) of a given DOTS client if the DOTS server does not find any mitigation record for that DOTS client. As a reminder, a DOTS client is identified by its identity (e.g., client certificate, 'cuid') and optionally the 'cdid'.</t> <t><xreftarget="Figure5"></xref>target="Figure5" format="default"/> shows a response example of all active mitigation requests associated with the DOTS client as maintained by the DOTS server. The response indicates the mitigation status of each mitigation request.</t><t><figure anchor="Figure5" title="Response<figure anchor="Figure5"> <name>Response Body to a GETRequest"> <artwork align="left"><![CDATA[{Request</name> <sourcecode><![CDATA[ { "ietf-dots-signal-channel:mitigation-scope": { "scope": [ { "mid": 12332, "mitigation-start": "1507818434", "target-prefix": [ "2001:db8:6401::1/128", "2001:db8:6401::2/128" ], "target-protocol": [ 17 ], "lifetime": 1756, "status": "attack-successfully-mitigated", "bytes-dropped": "134334555", "bps-dropped": "43344", "pkts-dropped": "333334444", "pps-dropped": "432432" }, { "mid": 12333, "mitigation-start": "1507818393", "target-prefix": [ "2001:db8:6401::1/128", "2001:db8:6401::2/128" ], "target-protocol": [ 6 ], "lifetime": 1755, "status": "attack-stopped", "bytes-dropped": "0", "bps-dropped": "0", "pkts-dropped": "0", "pps-dropped": "0" } ] }}]]></artwork> </figure></t>}]]></sourcecode> </figure> <t>The mitigation status parameters are described below:</t><t><list style="hanging"> <t hangText="mitigation-start:">Mitigation<dl newline="false" spacing="normal"> <dt>mitigation-start:</dt> <dd> <t>Mitigation start time is expressed in seconds relative to 1970-01-01T00:00Z in UTC time(Section 2.4.1 of <xref target="RFC7049"></xref>).(<xref target="RFC7049" section="2.4.1" sectionFormat="of" format="default"/>). The CBOR encoding is modified so that the leading tag 1 (epoch-based date/time)MUST<bcp14>MUST</bcp14> beomitted.<vspace blankLines="1" />Thisomitted.</t> <t>This is a mandatory attribute when an attack mitigation is active. Particularly, 'mitigation-start' is not returned for a mitigation with 'status' code set to 8.</t><t hangText="lifetime:">The</dd> <dt>lifetime:</dt> <dd> <t>The remaining lifetime of the mitigation request, inseconds.<vspace blankLines="1" />Thisseconds.</t> <t>This is a mandatory attribute.</t><t hangText="status:">Status</dd> <dt>status:</dt> <dd> <t>Status of attack mitigation. The various possible values of 'status' parameter are explained in <xreftarget="status"></xref>.<vspace blankLines="1" />Thistarget="status" format="default"/>.</t> <t>This is a mandatory attribute.</t><t hangText="bytes-dropped:">The</dd> <dt>bytes-dropped:</dt> <dd> <t>The total dropped byte count for the mitigation request since the attack mitigationiswas triggered. The count wraps around when it reaches the maximum value of unsigned integer64.<vspace blankLines="1" />This</t> <t>This is an optional attribute.</t><t hangText="bps-dropped:">The</dd> <dt>bps-dropped:</dt> <dd> <t>The average number of dropped bytes per second for the mitigation request since the attack mitigationiswas triggered. This averageSHOULD<bcp14>SHOULD</bcp14> be over five-minute intervals (that is, measuring bytes into five-minute buckets and then averaging these buckets over the time since the mitigation was triggered).<vspace blankLines="1" />This</t> <t>This is an optional attribute.</t><t hangText="pkts-dropped:">The</dd> <dt>pkts-dropped:</dt> <dd> <t>The total number of dropped packet count for the mitigation request since the attack mitigationiswas triggered. The count wraps around when it reaches the maximum value of unsignedinteger64.<vspace blankLines="1" />Thisinteger64.</t> <t>This is an optional attribute.</t><t hangText="pps-dropped:">The</dd> <dt>pps-dropped:</dt> <dd> <t>The average number of dropped packets per second for the mitigation request since the attack mitigationiswas triggered. This averageSHOULD<bcp14>SHOULD</bcp14> be over five-minute intervals (that is, measuring packets into five-minute buckets and then averaging these buckets over the time since the mitigation wastriggered).<vspace blankLines="1" />Thistriggered).</t> <t>This is an optional attribute.</t></list></t> <t></t> <texttable</dd> </dl> <table anchor="status"style="all" title=" Valuesalign="center"> <name>Values of 'status'Parameter"> <ttcolParameter</name> <thead> <tr> <th align="right">ParameterValue</ttcol> <ttcol align="left">Description</ttcol> <c>1</c> <c>AttackValue</th> <th align="left">Description</th> </tr> </thead> <tbody> <tr> <td align="right">1</td> <td align="left">Attack mitigation setup is in progress (e.g., changing the network path to redirect the inbound traffic to a DOTSmitigator).</c> <c>2</c> <c>Attackmitigator).</td> </tr> <tr> <td align="right">2</td> <td align="left">Attack is being successfully mitigated (e.g., traffic is redirected to a DDoS mitigator and attack traffic isdropped).</c> <c>3</c> <c>Attackdropped).</td> </tr> <tr> <td align="right">3</td> <td align="left">Attack has stopped and the DOTS client can withdraw the mitigation request. This status code will be transmitted for immediate mitigation requests till the mitigation is withdrawn or the lifetime expires. For mitigation requests withpre-configuredpreconfigured scopes (i.e., 'trigger-mitigation' set to 'false'), this status code will be transmitted4four times and then transition to"8".</c> <c>4</c> <c>Attack"8".</td> </tr> <tr> <td align="right">4</td> <td align="left">Attack has exceeded the mitigation providercapability.</c> <c>5</c> <c>DOTScapability.</td> </tr> <tr> <td align="right">5</td> <td align="left">DOTS client has withdrawn the mitigation request and the mitigation is active butterminating.</c> <c>6</c> <c>Attackterminating.</td> </tr> <tr> <td align="right">6</td> <td align="left">Attack mitigation is nowterminated.</c> <c>7</c> <c>Attackterminated.</td> </tr> <tr> <td align="right">7</td> <td align="left">Attack mitigation is withdrawn (by the DOTS server). If a mitigation request with 'trigger-mitigation' set tofalse'false' is withdrawn because it overlaps with an immediate mitigation request, this status code will be transmitted4four times and then transition to "8" for the mitigation request withpre-configured scopes.</c> <c>8</c> <c>Attackpreconfigured scopes.</td> </tr> <tr> <td align="right">8</td> <td align="left">Attack mitigation will be triggered for the mitigation request only when the DOTS signal channel session islost.</c> </texttable> <t></t>lost.</td> </tr> </tbody> </table> <sectiontitle="DOTSnumbered="true" toc="default"> <name>DOTS Servers Sending MitigationStatus">Status</name> <t>The Observe Option defined in <xreftarget="RFC7641"></xref>target="RFC7641" format="default"/> extends the CoAP core protocol with a mechanism for a CoAP client to "observe" a resource on a CoAP server:Thethe client retrieves a representation of the resource and requests this representation be updated by the server as long as the client is interested in the resource. DOTS implementationsMUST<bcp14>MUST</bcp14> use the Observe Option for both 'mitigate' and 'config' (<xreftarget="uri-path"></xref>).</t>target="uri-path" format="default"/>).</t> <t>A DOTS client conveys the Observe Option set to '0' in the GET request to receive asynchronous notifications of attack mitigation status from the DOTS server.</t> <t>Unidirectional mitigation notifications within the bidirectional signal channel enables asynchronous notifications between the agents. <xreftarget="RFC7641"></xref>target="RFC7641" format="default"/> indicates that (1) a notification can be sent in a Confirmable or a Non-confirmable message, and (2) the message type used is typicallyapplication-dependentapplication dependent and may be determined by the server for each notification individually. For the DOTS server application, the message typeMUST<bcp14>MUST</bcp14> always be set to Non-confirmable even if the underlying COAP library elects a notification to be sent in a Confirmable message. This overrides the behavior defined inSection 4.5 of<xreftarget="RFC7641"></xref>target="RFC7641" section="4.5" sectionFormat="of" format="default"/> to send a Confirmable message instead of a Non-confirmable message at least every 24hourhours for the following reasons: First, the DOTS signal channel uses a heartbeat mechanism to determine if the DOTS client is alive. Second, Confirmable messages are not suitable during an attack.</t> <t>Due to the higher likelihood of packet loss during a DDoS attack, the DOTS server periodically sends attack mitigation status to the DOTS client and also notifies the DOTS client whenever the status of the attack mitigation changes. If the DOTS server cannot maintain an RTT estimate, itMUST NOT<bcp14>MUST NOT</bcp14> send more than one asynchronous notification every 3 seconds, andSHOULD<bcp14>SHOULD</bcp14> use an even less aggressive rate whenever possible (case 2 inSection 3.1.3 of<xreftarget="RFC8085"></xref>).</t> <t><!--The DOTS server MUST use the same CUID as the one used by the DOTS client to observe a mitigation request.-->Whentarget="RFC8085" section="3.1.3" sectionFormat="of" format="default"/>).</t> <t>When conflicting requests are detected, the DOTS server enforces the corresponding policy (e.g., accept all requests, reject all requests, accept only one request but reject all the others,...).etc.). It is assumed that this policy is supplied by the DOTS server administrator or that it is a default behavior of the DOTS server implementation. Then, the DOTS server sends a notification message(s) to the DOTS client(s) at the origin of the conflict (refer to the conflict parameters defined in <xreftarget="post"></xref>).target="post" format="default"/>). A conflict notification message includes information about the conflict cause, scope, and the status of the mitigation request(s). Forexample,<list style="symbols"> <t>Aexample:</t> <ul spacing="normal"> <li>A notification message with 'status' code set to '7 (Attack mitigation is withdrawn)' and 'conflict-status' set to '1' is sent to a DOTS client to indicate that an active mitigation request is deactivated because a conflict isdetected.</t> <t>Adetected.</li> <li>A notification message with 'status' code set to '1 (Attack mitigation is in progress)' and 'conflict-status' set to '2' is sent to a DOTS client to indicate that this mitigation request is in progress, but a conflict isdetected.</t> </list></t>detected.</li> </ul> <t>Upon receipt of a conflict notification message indicating that a mitigation request is deactivated because of a conflict, a DOTS clientMUST NOT<bcp14>MUST NOT</bcp14> resend the same mitigation request before the expiry of 'retry-timer'. It is also recommended that DOTS clients support the means to alert administrators about mitigation conflicts.</t> <t>A DOTS client that is no longer interested in receiving notifications from the DOTS server can simply "forget" the observation. When the DOTS server sends the next notification, the DOTS client will not recognize the token in the messageand thusand, thus, will return a Reset message. This causes the DOTS server to remove the associated entry. Alternatively, the DOTS client can explicitlyderegisterde-register itself by issuing a GET request that has the Token field set to the token of the observation to becancelledcanceled and includes an Observe Option with the value set to '1'(deregister).(de-register). The latter is more deterministicand thusand, thus, isRECOMMENDED.</t><bcp14>RECOMMENDED</bcp14>.</t> <t><xreftarget="Figure6"></xref>target="Figure6" format="default"/> shows an example of a DOTS client requesting a DOTS server to send notifications related to a mitigation request. Note that for mitigations withpre-configuredpreconfigured scopes (i.e., 'trigger-mitigation' set to 'false'), the state will need to transition from 3 (attack-stopped) to 8 (attack-mitigation-signal-loss).</t><t><figure anchor="Figure6" title="Notifications<figure anchor="Figure6"> <name>Notifications of Attack MitigationStatus">Status</name> <artworkalign="center"><![CDATA[+-----------+align="center" name="" type="" alt=""><![CDATA[ +-----------+ +-----------+ |DOTSclient|Client| |DOTSserver|Server| +-----------+ +-----------+ | | | GET /<mid> | | Token: 0x4a | Registration | Observe: 0 | +----------------------------------------->| | | | 2.05 Content | | Token: 0x4a | Notification of | Observe: 12 | the current state | status: "attack-mitigation-in-progress" | |<-----------------------------------------+ | ||<-----------------------------------------+| 2.05 Content | | Token: 0x4a | Notification upon | Observe: 44 | a state change | status: "attack-successfully-mitigated" | |<-----------------------------------------+ | ||<-----------------------------------------+| 2.05 Content | | Token: 0x4a | Notification upon | Observe: 60 | a state change | status: "attack-stopped" | |<-----------------------------------------+ | | ... ]]></artwork></figure></t></figure> </section> <sectiontitle="DOTSnumbered="true" toc="default"> <name>DOTS Clients Polling for MitigationStatus">Status</name> <t>The DOTS client can send the GET request at frequent intervals without the Observe Option to retrieve the configuration data of the mitigation request and non-configuration data (i.e., the attack status). DOTS clientsMAY<bcp14>MAY</bcp14> be configured with a policy indicating the frequency of polling DOTS servers to get the mitigation status. This frequencyMUST NOT<bcp14>MUST NOT</bcp14> be more than one UDP datagram per RTT as discussed inSection 3.1.3 of<xreftarget="RFC8085"></xref>.</t>target="RFC8085" section="3.1.3" sectionFormat="of" format="default"/>.</t> <t>If the DOTS server has been able to mitigate the attack and the attack has stopped, the DOTS server indicates as such in the status. In such case, the DOTS client recalls the mitigation request by issuing a DELETE request for this mitigation request (<xreftarget="del"></xref>).</t>target="del" format="default"/>).</t> <t>A DOTS clientSHOULD<bcp14>SHOULD</bcp14> react to the status of the attackasper the information sent by the DOTS server rather than performing its own detection that the attack has been mitigated. This ensures that the DOTS client does not recall a mitigation request prematurely because it is possible that the DOTS client does not sense the DDoS attack on its resources, but the DOTS server could be actively mitigating the attack because the attack is not completely averted.</t> </section> </section> <section anchor="put"title="Efficacynumbered="true" toc="default"> <name>Efficacy Update from DOTSClients">Clients</name> <t>While DDoS mitigation is in progress, due to the likelihood of packet loss, a DOTS clientMAY<bcp14>MAY</bcp14> periodically transmit DOTS mitigation efficacy updates to the relevant DOTS server. A PUT request is used to convey the mitigation efficacy update to the DOTS server. This PUT request is treated as a refresh of the current mitigation.</t> <t>The PUT request used for the efficacy updateMUST<bcp14>MUST</bcp14> include all the parameters used in the PUT request to carry the DOTS mitigation request (<xreftarget="post"></xref>)target="post" format="default"/>) unchanged apart from the 'lifetime' parameter value. If this is not the case, the DOTS serverMUST<bcp14>MUST</bcp14> reject the request with a 4.00 (Bad Request).</t> <t>The If-Match Option(Section 5.10.8.1 of <xref target="RFC7252"></xref>)(<xref target="RFC7252" section="5.10.8.1" sectionFormat="of" format="default"/>) with an empty value is used to make the PUT request conditional on the current existence of the mitigation request. If UDP is used as transport, CoAP requests may arriveout-of-order.out of order. For example, the DOTS client may send a PUT request to convey an efficacy update to the DOTS server followed by a DELETE request to withdraw the mitigation request, but the DELETE request arrives at the DOTS server before the PUT request. To handle out-of-order delivery of requests, if an If-Match Option is present in the PUT request and the 'mid' in the request matches a mitigation request from that DOTS client, the request is processed by the DOTS server. If no match is found, the PUT request is silently ignored by the DOTS server.</t> <t>An example of an efficacy update message, which includes an If-Match Option with an empty value, is depicted in <xreftarget="Figure7"></xref>.</t>target="Figure7" format="default"/>.</t> <figureanchor="Figure7" title="Ananchor="Figure7"> <name>An Example of EfficacyUpdate"> <artwork align="left"><![CDATA[Update</name> <sourcecode><![CDATA[ Header: PUT (Code=0.03) Uri-Path: ".well-known" Uri-Path: "dots" Uri-Path: "mitigate" Uri-Path: "cuid=dz6pHjaADkaFTbjr0JGBpw" Uri-Path: "mid=123" If-Match: Content-Format: "application/dots+cbor" { "ietf-dots-signal-channel:mitigation-scope": { "scope": [ { "target-prefix": [ "2001:db8:6401::1/128", "2001:db8:6401::2/128" ], "target-port-range": [ { "lower-port": 80 }, { "lower-port": 443 }, { "lower-port": 8080 } ], "target-protocol": [ 6 ], "attack-status": "under-attack" } ] }}]]></artwork>}]]></sourcecode> </figure><t></t><t>The 'attack-status' parameter is a mandatory attribute when performing an efficacy update. The various possible values contained in the 'attack-status' parameter are described in <xreftarget="astatus"></xref>.</t> <texttabletarget="astatus" format="default"/>.</t> <table anchor="astatus"style="all" title=" Valuesalign="center"> <name>Values of 'attack-status'Parameter"> <ttcolParameter</name> <thead> <tr> <th align="right">Parametervalue</ttcol> <ttcol align="left">Description</ttcol> <c>1</c> <c>TheValue</th> <th align="left">Description</th> </tr> </thead> <tbody> <tr> <td align="right">1</td> <td align="left">The DOTS client determines that it is still underattack.</c> <c>2</c> <c>Theattack.</td> </tr> <tr> <td align="right">2</td> <td align="left">The DOTS client determines that the attack is successfully mitigated (e.g., attack traffic is notseen).</c> </texttable>seen).</td> </tr> </tbody> </table> <t>The DOTS server indicates the result of processing a PUT request using CoAPresponse codes.Response Codes. Theresponse codeResponse Code 2.04 (Changed) is returned if the DOTS server has accepted the mitigation efficacy update. The errorresponse codeResponse Code 5.03 (Service Unavailable) is returned if the DOTS server has erred or is incapable of performing the mitigation. As specified in <xreftarget="RFC7252"></xref>,target="RFC7252" format="default"/>, 5.03 uses Max-AgeoptionOption to indicate the number of seconds after which to retry.</t> </section> <section anchor="del"title="Withdrawnumbered="true" toc="default"> <name>Withdraw aMitigation">Mitigation</name> <t>DELETE requests are used to withdraw DOTS mitigation requests from DOTS servers (<xreftarget="Figure3"></xref>).</t>target="Figure3" format="default"/>).</t> <t>'cuid' and 'mid' are mandatory Uri-Path parameters for DELETE requests.</t> <t>The same considerations for manipulating 'cdid' parameter by DOTS gateways, as specified in <xreftarget="post"></xref>, MUSTtarget="post" format="default"/>, <bcp14>MUST</bcp14> be followed for DELETE requests. Uri-Path parameters with empty valuesMUST NOT<bcp14>MUST NOT</bcp14> be present in a request.</t> <figureanchor="Figure3" title="Withdrawanchor="Figure3"> <name>Withdraw a DOTSMitigation"> <artwork align="left"><![CDATA[Mitigation</name> <sourcecode><![CDATA[ Header: DELETE (Code=0.04) Uri-Path: ".well-known" Uri-Path: "dots" Uri-Path: "mitigate" Uri-Path: "cuid=dz6pHjaADkaFTbjr0JGBpw" Uri-Path: "mid=123"]]></artwork>]]></sourcecode> </figure> <t>If the DELETE request does not include 'cuid' and 'mid' parameters, the DOTS serverMUST<bcp14>MUST</bcp14> reply with a 4.00 (Bad Request).</t> <t>Once the request is validated, the DOTS server immediately acknowledges a DOTS client's request to withdraw the DOTS signal using 2.02 (Deleted)response codeResponse Code with no response payload. A 2.02 (Deleted) Response Code is returned even if the 'mid' parameter value conveyed in the DELETE request does not exist in its configuration data before the request.</t> <t>If the DOTS server finds the 'mid' parameter value conveyed in the DELETE request in its configuration data for the DOTS client, then to protect against route or DNS flapping caused by a DOTS client rapidly removing a mitigation, and to dampen the effect of oscillating attacks, the DOTS serverMAY<bcp14>MAY</bcp14> allow mitigation to continue for a limited period after acknowledging a DOTS client's withdrawal of a mitigation request. During this period, the DOTS server status messagesSHOULD<bcp14>SHOULD</bcp14> indicate that mitigation is active but terminating (<xreftarget="get"></xref>).</t>target="get" format="default"/>).</t> <t>The initial active-but-terminating periodSHOULD<bcp14>SHOULD</bcp14> be sufficiently long to absorb latency incurred by route propagation. The active-but-terminating periodSHOULD<bcp14>SHOULD</bcp14> be set by default to 120 seconds. If the client requests mitigation again before the initial active-but-terminating period elapses, the DOTS serverMAY<bcp14>MAY</bcp14> exponentially increase (the base of the exponent is 2) the active-but-terminating period up to a maximum of 300 seconds (5 minutes).</t> <t>Once the active-but-terminating period elapses, the DOTS serverMUST<bcp14>MUST</bcp14> treat the mitigation as terminated, as the DOTS client is no longer responsible for the mitigation.</t> <t>If a mitigation is triggered due to a signal channel loss, the DOTS server relies upon normal triggers to stop that mitigation (typically, receipt of a valid DELETE request, expiry of the mitigation lifetime, or scrubbing the traffic to the attack target). In particular, the DOTS serverMUST NOT<bcp14>MUST NOT</bcp14> consider the signal channel recovery as a trigger to stop the mitigation.</t> </section> </section> <section anchor="sigconfig"title="DOTSnumbered="true" toc="default"> <name>DOTS Signal Channel SessionConfiguration">Configuration</name> <t>A DOTS client can negotiate, configure, and retrieve the DOTS signal channel session behavior with its DOTS peers. The DOTS signal channel can be used, for example, to configure thefollowing:<list style="letters"> <t>Heartbeatfollowing:</t> <ol spacing="normal" type="a"> <li>Heartbeat interval (heartbeat-interval): DOTS agents regularly send heartbeats to each other after mutual authentication is successfully completed in order to keep the DOTS signal channel open. Heartbeat messages are exchanged between DOTS agents every 'heartbeat-interval' seconds to detect the current status of the DOTS signal channelsession.</t> <t>Missingsession.</li> <li>Missing heartbeats allowed (missing-hb-allowed): This variable indicates the maximum number of consecutive heartbeat messages for which a DOTS agent did not receive a response before concluding that the session is disconnected ordefunct.</t> <t>Acceptabledefunct.</li> <li>Acceptable probing rate (probing-rate): This parameter indicates the average data rate that must not be exceeded by a DOTS agent in sending to a peer DOTS agent that does notrespond.</t> <t>Acceptablerespond.</li> <li>Acceptable signal loss ratio: Maximum retransmissions, retransmission timeout value, and other message transmission parameters for Confirmable messages over the DOTS signalchannel.</t> </list></t>channel.</li> </ol> <t>When the DOTS signal channel is established over a reliable transport (e.g., TCP), there is no need for the reliability mechanisms provided by CoAP over UDP since the underlying TCP connection provides retransmissions and deduplication <xreftarget="RFC8323"></xref>.target="RFC8323" format="default"/>. As a reminder, CoAP over reliable transports does not support Confirmable or Non-confirmable message types. As such, the transmission-related parameters(missing-hb-allowed('missing-hb-allowed' and acceptable signal loss ratio) are negotiated only for DOTS over unreliable transports.</t> <t>The same or distinct configuration sets may be used during times when a mitigation is active ('mitigating-config') and when no mitigation is active ('idle-config'). This is particularly useful for DOTS servers that might want to reduce heartbeat frequency or cease heartbeat exchanges when an active DOTS client has not requested mitigation. If distinct configurations are used, DOTS agentsMUST<bcp14>MUST</bcp14> follow the appropriate configuration set as a function of the mitigation activity (e.g., if no mitigation request is active (also referred to as 'idle' time),'idle-config'-relatedvalues related to 'idle-config' must be followed). Additionally, DOTS agentsMUST<bcp14>MUST</bcp14> automatically switch to the other configuration upon a change in the mitigation activity (e.g., if an attack mitigation is launched after an 'idle' time, the DOTS agent switches from values related to 'idle-config' to'mitigating-config'-related values).</t>values related to 'mitigating-config').</t> <t>CoAPRequestsrequests and responses are indicated for reliable delivery by marking them as Confirmable messages. DOTS signal channel session configuration requests and responses are marked as Confirmable messages. As explained inSection 2.1 of<xreftarget="RFC7252"></xref>,target="RFC7252" section="2.1" sectionFormat="of" format="default"/>, a Confirmable message is retransmitted using a default timeout and exponentialback-offbackoff between retransmissions, until the DOTS server sends an Acknowledgement message (ACK) with the same Message ID conveyed from the DOTS client.</t> <t>Message transmission parameters are defined inSection 4.8 of<xreftarget="RFC7252"></xref>.target="RFC7252" section="4.8" sectionFormat="of" format="default"/>. The DOTS server can either piggyback the response in theacknowledgementAcknowledgement message or, if the DOTS server cannot respond immediately to a request carried in a Confirmable message, it simply responds with an Empty Acknowledgement message so that the DOTS client can stop retransmitting the request. Empty Acknowledgement messages are explained inSection 2.2 of<xreftarget="RFC7252"></xref>.target="RFC7252" section="2.2" sectionFormat="of" format="default"/>. When the response is ready, the server sends it in a new Confirmablemessage whichmessage, which, inturnturn, needs to be acknowledged by the DOTS client (see Sections5.2.1<xref target="RFC7252" section="5.2.1" sectionFormat="bare" format="default"/> and5.2.2<xref target="RFC7252" section="5.2.2" sectionFormat="bare" format="default"/> of <xreftarget="RFC7252"></xref>).target="RFC7252" format="default"/>). Requests and responses exchanged between DOTS agents during 'idle' time, except heartbeat messages, are marked as Confirmablemessages.<list style="empty">messages.</t> <aside> <t>Implementation Note: A DOTS client that receives a response in a Confirmable message may want to clean up the message state right after sending the ACK. If that ACK is lost and the DOTS server retransmits the Confirmable message, the DOTS client may no longer have any state that would help it correlate this response: from the DOTS client's standpoint, the retransmission message is unexpected. The DOTS client will send a Reset message so it does not receive any more retransmissions. This behavior is normal and not an indication of an error (seeSection 5.3.2 of<xreftarget="RFC7252"></xref>target="RFC7252" section="5.3.2" sectionFormat="of" format="default"/> for more details).</t></list></t></aside> <section anchor="discovery"title="Discovernumbered="true" toc="default"> <name>Discover ConfigurationParameters">Parameters</name> <t>A GET request is used to obtain acceptable (e.g., minimum and maximum values) and current configuration parameters on the DOTS server for DOTS signal channel session configuration. This procedure occurs between a DOTS client and its immediate peer DOTS server. As such, this GET requestMUST NOT<bcp14>MUST NOT</bcp14> be relayed by a DOTS gateway.</t> <t><xreftarget="Figure18"></xref>target="Figure18" format="default"/> shows how to obtain configuration parameters that the DOTS server will find acceptable.</t> <figureanchor="Figure18" title="GETanchor="Figure18"> <name>GET to RetrieveConfiguration"> <artwork align="left"><![CDATA[Configuration</name> <sourcecode><![CDATA[ Header: GET (Code=0.01) Uri-Path: ".well-known" Uri-Path: "dots" Uri-Path: "config"]]></artwork>]]></sourcecode> </figure> <t>The DOTS server in the 2.05 (Content) response conveys the current, minimum, and maximum attribute values acceptable by the DOTS server (<xreftarget="Figure19"></xref>).</t> <t><figure anchor="Figure19" title="GETtarget="Figure19" format="default"/>).</t> <figure anchor="Figure19"> <name>GET Configuration Response BodySchema"> <artwork align="left"><![CDATA[{Schema</name> <sourcecode><![CDATA[ { "ietf-dots-signal-channel:signal-config": { "mitigating-config": { "heartbeat-interval": { "max-value": number, "min-value": number, "current-value": number }, "missing-hb-allowed": { "max-value": number, "min-value": number, "current-value": number }, "probing-rate": { "max-value": number, "min-value": number, "current-value": number }, "max-retransmit": { "max-value": number, "min-value": number, "current-value": number }, "ack-timeout": { "max-value-decimal": "string", "min-value-decimal": "string", "current-value-decimal": "string" }, "ack-random-factor": { "max-value-decimal": "string", "min-value-decimal": "string", "current-value-decimal": "string" } }, "idle-config": { "heartbeat-interval": { "max-value": number, "min-value": number, "current-value": number }, "missing-hb-allowed": { "max-value": number, "min-value": number, "current-value": number }, "probing-rate": { "max-value": number, "min-value": number, "current-value": number }, "max-retransmit": { "max-value": number, "min-value": number, "current-value": number }, "ack-timeout": { "max-value-decimal": "string", "min-value-decimal": "string", "current-value-decimal": "string" }, "ack-random-factor": { "max-value-decimal": "string", "min-value-decimal": "string", "current-value-decimal": "string" } } }}]]></artwork> </figure></t>}]]></sourcecode> </figure> <t>The parameters in <xreftarget="Figure19"></xref>target="Figure19" format="default"/> are described below:</t><t><list style="hanging"> <t hangText="mitigating-config:">Set<dl newline="false" spacing="normal"> <dt>mitigating-config:</dt> <dd> <t>Set of configuration parameters to use when a mitigation is active. The following parameters may be included:<list style="hanging"> <t hangText="heartbeat-interval: ">Time</t> <dl newline="false" spacing="normal"> <dt>heartbeat-interval: </dt> <dd> <t>Time interval in seconds between two consecutive heartbeat messages.<vspace blankLines="1" />'0'</t> <t>'0' is used to disable the heartbeat mechanism.<vspace blankLines="1" />This</t> <t>This is an optional attribute.</t><t hangText="missing-hb-allowed: ">Maximum</dd> <dt>missing-hb-allowed: </dt> <dd> <t>Maximum number of consecutive heartbeat messages for which the DOTS agent did not receive a response before concluding that the session is disconnected.<vspace blankLines="1" />This</t> <t>This is an optional attribute.</t><t hangText="probing-rate:">The</dd> <dt>probing-rate:</dt> <dd> <t>The average data rate that must not be exceeded by a DOTS agent in sending to a peer DOTS agent that does not respond (referred to as PROBING_RATE parameter in CoAP).<vspace blankLines="1" />This</t> <t>This is an optional attribute.</t><t hangText="max-retransmit: ">Maximum</dd> <dt>max-retransmit: </dt> <dd> <t>Maximum number of retransmissions for a message (referred to as MAX_RETRANSMIT parameter in CoAP).<vspace blankLines="1" />This</t> <t>This is an optional attribute.</t><t hangText="ack-timeout: ">Timeout</dd> <dt>ack-timeout: </dt> <dd> <t>Timeout value in seconds used to calculate the initial retransmission timeout value (referred to as ACK_TIMEOUT parameter in CoAP).<vspace blankLines="1" />This</t> <t>This is an optional attribute.</t><t hangText="ack-random-factor: ">Random</dd> <dt>ack-random-factor: </dt> <dd> <t>Random factor used to influence the timing of retransmissions (referred to as ACK_RANDOM_FACTOR parameter in CoAP).<vspace blankLines="1" />This</t> <t>This is an optional attribute.</t></list></t> <t hangText="idle-config: ">Set</dd> </dl> </dd> <dt>idle-config: </dt> <dd>Set of configuration parameters to use when no mitigation is active. This attribute has the same structure as'mitigating-config'.</t> </list></t>'mitigating-config'.</dd> </dl> <t><xreftarget="Figure17"></xref>target="Figure17" format="default"/> shows an example of acceptable and current configuration parameters on a DOTS server for DOTS signal channel session configuration. The same acceptable configuration is used during mitigation and idle times.</t><t><figure anchor="Figure17" title="Example<figure anchor="Figure17"> <name>Example of a Configuration ResponseBody"> <artwork align="left"><![CDATA[{Body</name> <sourcecode><![CDATA[ { "ietf-dots-signal-channel:signal-config": { "mitigating-config": { "heartbeat-interval": { "max-value": 240, "min-value": 15, "current-value": 30 }, "missing-hb-allowed": { "max-value": 20, "min-value": 3, "current-value": 15 }, "probing-rate": { "max-value": 20, "min-value": 5, "current-value": 15 }, "max-retransmit": { "max-value": 15, "min-value": 2, "current-value": 3 }, "ack-timeout": { "max-value-decimal": "30.00", "min-value-decimal": "1.00", "current-value-decimal": "2.00" }, "ack-random-factor": { "max-value-decimal": "4.00", "min-value-decimal": "1.10", "current-value-decimal": "1.50" } }, "idle-config": { "heartbeat-interval": { "max-value": 240, "min-value": 15, "current-value": 30 }, "missing-hb-allowed": { "max-value": 20, "min-value": 3, "current-value": 15 }, "probing-rate": { "max-value": 20, "min-value": 5, "current-value": 15 }, "max-retransmit": { "max-value": 15, "min-value": 2, "current-value": 3 }, "ack-timeout": { "max-value-decimal": "30.00", "min-value-decimal": "1.00", "current-value-decimal": "2.00" }, "ack-random-factor": { "max-value-decimal": "4.00", "min-value-decimal": "1.10", "current-value-decimal": "1.50" } } }}]]></artwork> </figure></t>}]]></sourcecode> </figure> </section> <section anchor="convey"title="Conveynumbered="true" toc="default"> <name>Convey DOTS Signal Channel SessionConfiguration">Configuration</name> <t>A PUT request (Figures <xref format="counter"target="Figure13"></xref>target="Figure13"/> and <xref format="counter"target="Figure13a"></xref>)target="Figure13a"/>) is used to convey the configuration parameters for the signal channel (e.g., heartbeat interval, maximum retransmissions). Message transmission parameters for CoAP are defined inSection 4.8 of<xreftarget="RFC7252"></xref>.target="RFC7252" section="4.8" sectionFormat="of" format="default"/>. TheRECOMMENDED<bcp14>RECOMMENDED</bcp14> values of transmission parameter values areack-timeout'ack-timeout' (2 seconds),max-retransmit'max-retransmit' (3), andack-random-factor'ack-random-factor' (1.5). In addition to those parameters, theRECOMMENDED<bcp14>RECOMMENDED</bcp14> specific DOTS transmission parameter values are 'heartbeat-interval' (30 seconds) and 'missing-hb-allowed' (15).<list style="empty"></t> <aside> <t>Note:heartbeat-interval'heartbeat-interval' should be tweaked to also assist DOTS messages for NAT traversal (SIG-011 of <xreftarget="RFC8612"></xref>).target="RFC8612" format="default"/>). According to <xreftarget="RFC8085"></xref>,target="RFC8085" format="default"/>, heartbeat messages must not be sent more frequently than once every 15 seconds and should use longer intervals when possible. Furthermore, <xreftarget="RFC4787"></xref>target="RFC4787" format="default"/> recommends that NATstouse a state timeout of 2 minutes or longer, but experience shows that sending packets every 15 to 30 seconds is necessary to prevent the majority of middleboxes from losing state for UDP flows. From that standpoint, theRECOMMENDED<bcp14>RECOMMENDED</bcp14> minimumheartbeat-interval'heartbeat-interval' is 15 seconds and theRECOMMENDED<bcp14>RECOMMENDED</bcp14> maximumheartbeat-interval'heartbeat-interval' is 240 seconds. The recommended value of 30 seconds is selected to anticipate the expiry of NAT state.</t> <t>Aheartbeat-interval'heartbeat-interval' of 30 seconds may be consideredasto be too chatty in some deployments. For such deployments, DOTS agents may negotiate longerheartbeat-interval'heartbeat-interval' values to prevent any network overload with too frequent heartbeats.</t> <t>Different heartbeat intervals can be defined for 'mitigating-config' and 'idle-config' to reduce being too chatty during idle times. If there is an on-path translator between the DOTS client (standalone or part of a DOTS gateway) and the DOTS server, the 'mitigating-config'heartbeat-interval'heartbeat-interval' has to be smaller than the translator session timeout. It is recommended that the 'idle-config'heartbeat-interval is'heartbeat-interval' also be smaller than the translator session timeout to prevent translator traversalissues,issues ordisabled entirely.that it be disabled entirely. Means to discover the lifetime assigned by a translator are out of scope.</t> <t>Given that the size of the heartbeat requestcan notcannot exceed(heartbeat-interval('heartbeat-interval' *probing-rate)'probing-rate') bytes,probing-rate'probing-rate' should be set appropriately to avoid slowing down heartbeat exchanges. For example,probing-rate'probing-rate' may be set to 2 * ("size of encrypted DOTS heartbeatrequest"/heartbeat-interval)request"/'heartbeat-interval') or (("size of encrypted DOTS heartbeat request" + "average size of an encrypted mitigationrequest")/heartbeat-interval).request")/'heartbeat-interval'). Absent any explicit configuration or inability to dynamically adjustprobing-rate'probing-rate' values(Section 4.8.1 of <xref target="RFC7252"></xref>),(<xref target="RFC7252" section="4.8.1" sectionFormat="of" format="default"/>), DOTS agents use 5 bytes/second as a defaultprobing-rate'probing-rate' value.</t></list></t></aside> <t>If the DOTS agent wishes to change the default values of message transmission parameters, itSHOULD<bcp14>SHOULD</bcp14> follow the guidance given inSection 4.8.1 of<xreftarget="RFC7252"></xref>.target="RFC7252" section="4.8.1" sectionFormat="of" format="default"/>. The DOTS agentsMUST<bcp14>MUST</bcp14> use the negotiated values for message transmission parameters and default values for non-negotiated message transmission parameters.</t> <t>The signal channel session configuration is applicable to a single DOTS signal channel session between DOTS agents, so the 'cuid' Uri-PathMUST NOT<bcp14>MUST NOT</bcp14> be used.</t><t><figure anchor="Figure13" title="PUT<figure anchor="Figure13"> <name>PUT to Convey the DOTS Signal Channel Session ConfigurationData"> <artwork align="left"><![CDATA[Data</name> <sourcecode><![CDATA[ Header: PUT (Code=0.03) Uri-Path: ".well-known" Uri-Path: "dots" Uri-Path: "config" Uri-Path: "sid=123" Content-Format: "application/dots+cbor" { ...}]]></artwork> </figure></t>} ]]></sourcecode> </figure> <t>The additional Uri-Path parameter to those defined in <xreftarget="uris"></xref>target="uris" format="default"/> is as follows:<list hangIndent="5" style="hanging"> <t hangText="sid:">Session</t> <dl newline="false" spacing="normal" indent="5"> <dt>sid:</dt> <dd> <t>Session Identifier is an identifier for the DOTS signal channel session configuration data represented as an integer. This identifierMUST<bcp14>MUST</bcp14> be generated by DOTS clients. 'sid' valuesMUST<bcp14>MUST</bcp14> increase monotonically (when a new PUT is generated by a DOTS client to convey the configuration parameters for the signal channel).<vspace blankLines="1" />This</t> <t>This is a mandatory attribute.</t></list></t> <t><figure anchor="Figure13a" title="PUT</dd> </dl> <figure anchor="Figure13a"> <name>PUT to Convey the DOTS Signal Channel Session Configuration Data (Message BodySchema)"> <artwork align="left"><![CDATA[Schema)</name> <sourcecode><![CDATA[ { "ietf-dots-signal-channel:signal-config": { "mitigating-config": { "heartbeat-interval": { "current-value": number }, "missing-hb-allowed": { "current-value": number }, "probing-rate": { "current-value": number }, "max-retransmit": { "current-value": number }, "ack-timeout": { "current-value-decimal": "string" }, "ack-random-factor": { "current-value-decimal": "string" } }, "idle-config": { "heartbeat-interval": { "current-value": number }, "missing-hb-allowed": { "current-value": number }, "probing-rate": { "current-value": number }, "max-retransmit": { "current-value": number }, "ack-timeout": { "current-value-decimal": "string" }, "ack-random-factor": { "current-value-decimal": "string" } } }}]]></artwork> </figure></t>} ]]></sourcecode> </figure> <t>The meaning of the parameters in the CBOR body (<xreftarget="Figure13a"></xref>)target="Figure13a" format="default"/>) is defined in <xreftarget="discovery"></xref>.</t>target="discovery" format="default"/>.</t> <t>At least one of the attributes 'heartbeat-interval', 'missing-hb-allowed', 'probing-rate', 'max-retransmit', 'ack-timeout', and 'ack-random-factor'MUST<bcp14>MUST</bcp14> be present in the PUT request. Note that 'heartbeat-interval', 'missing-hb-allowed', 'probing-rate', 'max-retransmit', 'ack-timeout', and 'ack-random-factor', if present, do not need to be provided for both 'mitigating-config', and 'idle-config' in a PUT request.</t> <t>The PUT request with a higher numeric 'sid' value overrides the DOTS signal channel session configuration data installed by a PUT request with a lower numeric 'sid' value. To avoid maintaining a long list of 'sid' requests from a DOTS client, the lower numeric 'sid'MUST<bcp14>MUST</bcp14> be automatically deleted and no longer available at the DOTS server.</t> <t><xreftarget="Figure14"></xref>target="Figure14" format="default"/> shows a PUT request example to convey the configuration parameters for the DOTS signal channel. In this example, the heartbeat mechanism is disabled when no mitigation is active, while the heartbeat interval is set to '30' when a mitigation is active.</t><t><figure anchor="Figure14" title="PUT<figure anchor="Figure14"> <name>PUT to Convey the ConfigurationParameters"> <artwork align="left"><![CDATA[Parameters</name> <sourcecode><![CDATA[ Header: PUT (Code=0.03) Uri-Path: ".well-known" Uri-Path: "dots" Uri-Path: "config" Uri-Path: "sid=123" Content-Format: "application/dots+cbor" { "ietf-dots-signal-channel:signal-config": { "mitigating-config": { "heartbeat-interval": { "current-value": 30 }, "missing-hb-allowed": { "current-value": 15 }, "probing-rate": { "current-value": 15 }, "max-retransmit": { "current-value": 3 }, "ack-timeout": { "current-value-decimal": "2.00" }, "ack-random-factor": { "current-value-decimal": "1.50" } }, "idle-config": { "heartbeat-interval": { "current-value": 0 }, "max-retransmit": { "current-value": 3 }, "ack-timeout": { "current-value-decimal": "2.00" }, "ack-random-factor": { "current-value-decimal": "1.50" } } }}]]></artwork> </figure></t>} ]]></sourcecode> </figure> <t>The DOTS server indicates the result of processing the PUT request using CoAPresponse codes:<list style="symbols"> <t>IfResponse Codes:</t> <ul spacing="normal"> <li>If the request is missing a mandatory attribute, does not include a 'sid' Uri-Path, or contains one or more invalid or unknown parameters, 4.00 (Bad Request)MUST<bcp14>MUST</bcp14> be returned in theresponse.</t> <t>Ifresponse.</li> <li>If the DOTS server does not find the 'sid' parameter value conveyed in the PUT request in its configuration data and if the DOTS server has accepted the configuration parameters, then aresponse codeResponse Code 2.01 (Created)MUST<bcp14>MUST</bcp14> be returned in theresponse.</t> <t>Ifresponse.</li> <li>If the DOTS server finds the 'sid' parameter value conveyed in the PUT request in its configuration data and if the DOTS server has accepted the updated configuration parameters, 2.04 (Changed)MUST<bcp14>MUST</bcp14> be returned in theresponse.</t>response.</li> <li> <t>If any of the 'heartbeat-interval', 'missing-hb-allowed', 'probing-rate', 'max-retransmit', 'target-protocol', 'ack-timeout', and 'ack-random-factor' attribute values are not acceptable to the DOTS server, 4.22 (Unprocessable Entity)MUST<bcp14>MUST</bcp14> be returned in the response. Upon receipt of this error code, the DOTS clientSHOULD<bcp14>SHOULD</bcp14> retrieve the maximum and minimum attribute values acceptable to the DOTS server (<xreftarget="discovery"></xref>).<vspace blankLines="1" />Thetarget="discovery" format="default"/>).</t> <t>The DOTS client mayre-tryretry and send the PUT request with updated attribute values acceptable to the DOTS server.</t></list></t></li> </ul> <t>A DOTS client may issue a GET message with a 'sid' Uri-Path parameter to retrieve the negotiated configuration. The response does not need to include 'sid' in its message body.</t> </section> <sectiontitle="Configurationnumbered="true" toc="default"> <name>Configuration Freshness andNotifications">Notifications</name> <t>Max-Age Option(Section 5.10.5 of <xref target="RFC7252"></xref>) SHOULD(<xref target="RFC7252" section="5.10.5" sectionFormat="of" format="default"/>) <bcp14>SHOULD</bcp14> be returned by a DOTS server to associate a validity time with a configuration it sends. This feature allows the update of the configuration data if a change occurs at the DOTS server side. For example, the new configuration may instruct a DOTS client to cease heartbeats or reduce heartbeat frequency.</t> <t>It isNOT RECOMMENDED<bcp14>NOT RECOMMENDED</bcp14> to return a Max-Age Option set to 0.</t> <t>Returning a Max-Age Option set to2**32-12<sup>32</sup>-1 is equivalent to associating an infinite lifetime with the configuration.</t> <t>If a non-zero value of Max-Age Option is received by a DOTS client, itMUST<bcp14>MUST</bcp14> issue a GET request with a 'sid' Uri-Path parameter to retrieve the current and acceptable configuration before the expiry of the value enclosed in the Max-Ageoption.Option. This request is considered by the client and the serverasto be a means to refresh the configuration parameters for the signal channel. When a DDoS attack is active, refresh requestsMUST NOT<bcp14>MUST NOT</bcp14> be sent by DOTSclientsclients, and the DOTS serverMUST NOT<bcp14>MUST NOT</bcp14> terminate the (D)TLS session after the expiry of the value returned in Max-Age Option.</t> <t>If Max-Age Option is not returned in a response, the DOTS client initiates GET requests to refresh the configuration parameters each 60 seconds(Section 5.10.5 of <xref target="RFC7252"></xref>).(<xref target="RFC7252" section="5.10.5" sectionFormat="of" format="default"/>). To prevent such overload, it isRECOMMENDED<bcp14>RECOMMENDED</bcp14> that DOTS servers return a Max-Age Option in GET responses. Considerations related to which value to use and how such a value isset,set areimplementation-implementation anddeployment-specific.</t>deployment specific.</t> <t>If an Observe Option set to 0 is included in the configuration request, the DOTS server sends notifications of any configuration change(Section 4.2 of <xref target="RFC7641"></xref>).</t>(<xref target="RFC7641" section="4.2" sectionFormat="of" format="default"/>).</t> <t>If a DOTS server detects that a misbehaving DOTS client does not contact the DOTS server after the expiry of Max-Ageandto retrieve the signal channel configuration data, itMAY<bcp14>MAY</bcp14> terminate the (D)TLS session. A (D)TLS session is terminated by the receipt of an authenticated message that closes the connection (e.g., a fatal alert(Section 6 of <xref target="RFC8446"></xref>)).</t>(<xref target="RFC8446" section="6" sectionFormat="of" format="default"/>)).</t> </section> <sectiontitle="Deletenumbered="true" toc="default"> <name>Delete DOTS Signal Channel SessionConfiguration">Configuration</name> <t>A DELETE request is used to delete the installed DOTS signal channel session configuration data (<xreftarget="Figure15"></xref>).</t>target="Figure15" format="default"/>).</t> <figureanchor="Figure15" title="Delete Configuration"> <artwork align="left"><![CDATA[anchor="Figure15"> <name>Delete Configuration</name> <sourcecode><![CDATA[ Header: DELETE (Code=0.04) Uri-Path: ".well-known" Uri-Path: "dots" Uri-Path: "config" Uri-Path: "sid=123"]]></artwork>]]></sourcecode> </figure> <t>The DOTS server resets the DOTS signal channel session configuration back to the default values and acknowledges a DOTS client's request to remove the DOTS signal channel session configuration using 2.02 (Deleted)response code.</t>Response Code.</t> <t>Upon bootstrapping or reboot, a DOTS clientMAY<bcp14>MAY</bcp14> send a DELETE request to set the configuration parameters to default values. Such a request does not include any 'sid'.</t> </section> </section> <section anchor="redirect"title="Redirected Signaling">numbered="true" toc="default"> <name>Redirected Signaling</name> <t>Redirected DOTS signaling is discussed in detail inSection 3.2.2 of<xreftarget="I-D.ietf-dots-architecture"></xref>.</t>target="I-D.ietf-dots-architecture" section="3.2.2" sectionFormat="of" format="default"/>.</t> <t>If a DOTS server wants to redirect a DOTS client to an alternative DOTS server for a signal session, then theresponse codeResponse Code 5.03 (Service Unavailable) will be returned in the response to the DOTS client.</t> <t>The DOTS server can return the errorresponse codeResponse Code 5.03 in response to a request from the DOTS client or convey the errorresponse codeResponse Code 5.03 in a unidirectional notification response from the DOTS server.</t> <t>The DOTS server in the error response conveys the alternate DOTS server's FQDN, and the alternate DOTS server's IP address(es) values in the CBOR body (<xreftarget="Figure20"></xref>).</t>target="Figure20" format="default"/>).</t> <figureanchor="Figure20" title="Redirectedanchor="Figure20"> <name>Redirected Server Error Response BodySchema"> <artwork align="left"><![CDATA[{Schema</name> <sourcecode><![CDATA[ { "ietf-dots-signal-channel:redirected-signal": { "alt-server": "string", "alt-server-record": [ "string" ]}]]></artwork>} }]]></sourcecode> </figure> <t>The parameters are described below:</t><t><list style="hanging"> <t hangText="alt-server:">FQDN<dl newline="false" spacing="normal"> <dt>alt-server:</dt> <dd> <t>FQDN of an alternate DOTS server.<vspace blankLines="1" />This</t> <t>This is a mandatory attribute.</t><t hangText="alt-server-record:">A</dd> <dt>alt-server-record:</dt> <dd> <t>A list of IP addresses of an alternate DOTSserver.<vspace blankLines="1" />Thisserver.</t> <t>This is an optional attribute.</t></list></t></dd> </dl> <t>The DOTS server returns the Time toliveLive (TTL) of the alternate DOTS server in a Max-Age Option. That is, the time interval that the alternate DOTS server may be cached for use by a DOTS client. A Max-Age Option set to2**32-12<sup>32</sup>-1 is equivalent to receiving an infinite TTL. This value means that the alternate DOTS server is to be used until the alternate DOTS server redirects the traffic with another 5.03 responsewhich enclosesthat conveys an alternateserver.</t>server's FQDN.</t> <t>A Max-Age Option set to '0' may be returned for redirecting mitigation requests. Such a value means that the redirection applies only for the mitigation request in progress. Returning short TTL in a Max-Age Option may adversely impact DOTS clients on slow links. Returning short values should be avoided under such conditions.</t> <t>If the alternate DOTS server TTL has expired, the DOTS clientMUST<bcp14>MUST</bcp14> use the DOTSserver(s),server(s) that was provisioned using means discussed in <xreftarget="discover"></xref>.target="discover" format="default"/>. Thisfall backfallback mechanism is triggered immediately upon expiry of the TTL, except when a DDoS attack is active.</t> <t>Requests issued by misbehaving DOTS clientswhichthat do not honor the TTL conveyed in the Max-Age Option or react to explicitre-directredirect messages can be rejected by DOTS servers.</t> <t><xreftarget="Figure21"></xref>target="Figure21" format="default"/> shows a 5.03 response example to convey the DOTS alternate server 'alt-server.example' together with its IP addresses 2001:db8:6401::1 and 2001:db8:6401::2.</t><t><figure anchor="Figure21" title="Example<figure anchor="Figure21"> <name>Example of Redirected Server Error ResponseBody"> <artwork align="left"><![CDATA[{Body</name> <sourcecode><![CDATA[ { "ietf-dots-signal-channel:redirected-signal": { "alt-server": "alt-server.example", "alt-server-record": [ "2001:db8:6401::1", "2001:db8:6401::2" ]}]]></artwork> </figure></t>} }]]></sourcecode> </figure> <t>When the DOTS client receives a 5.03 response with an alternate server included, it considers the current requestasto have failed, butSHOULDit <bcp14>SHOULD</bcp14> tryre-sendingresending the request to the alternate DOTS server. During a DDoS attack, the DNS server may be the target of another DDoS attack, the alternate DOTS server's IP addresses conveyed in the 5.03 response help the DOTS client skip the DNS lookup of the alternate DOTS server, at the cost of trusting the first DOTS server to provide accurate information. The DOTS client can then try to establish a UDP or a TCP session with the alternate DOTS server. The DOTS clientMAY<bcp14>MAY</bcp14> implement a method to construct IPv4-embedded IPv6 addresses <xreftarget="RFC6052"></xref>;target="RFC6052" format="default"/>; this is required to handle the scenario where an IPv6-only DOTS client communicates with an IPv4-only alternate DOTS server.</t> <t>If the DOTS client has been redirected to a DOTS servertowith which it has already communicatedwithwithin the last five (5) minutes, itMUST<bcp14>MUST</bcp14> ignore the redirection and try to contact other DOTS servers listed in the local configuration or discovered using dynamic means such as DHCP or SRV procedures <xreftarget="I-D.ietf-dots-server-discovery"></xref>.target="I-D.ietf-dots-server-discovery" format="default"/>. It isRECOMMENDED<bcp14>RECOMMENDED</bcp14> that DOTS clients support the means to alert administrators about redirect loops.</t> </section> <section anchor="hb"title="Heartbeat Mechanism">numbered="true" toc="default"> <name>Heartbeat Mechanism</name> <t>To provide an indication of signal health and to distinguish an 'idle' signal channel from a 'disconnected' or 'defunct' session, the DOTS agent sends a heartbeat over the signal channel to maintain its half of the channel (also, aligned with the "consents" recommendation inSection 6 of<xreftarget="RFC8085"></xref>).target="RFC8085" section="6" sectionFormat="of" format="default"/>). The DOTS agent similarly expects a heartbeat from its peer DOTS agent, and it may consider a session terminated in the prolonged absence of a peer agent heartbeat. Concretely, while the communication between the DOTS agents is otherwise quiescent, the DOTS client will probe the DOTS server to ensure it has maintained cryptographic state and vice versa. Such probes can also keep the bindings of firewalls and/or stateful translatorsbindingsalive. This probing reduces the frequency of establishing a new handshake when a DOTS signal needs to be conveyed to the DOTSserver.<list style="empty">server.</t> <aside> <t>Implementation Note: Given that CoAP roles can be multiplexed over the same session as discussed in <xreftarget="RFC7252"></xref>target="RFC7252" format="default"/> and are already supported by CoAP implementations, both the DOTS client and server can send DOTS heartbeat requests.</t></list></t></aside> <t>The DOTSHeartbeatheartbeat mechanism usesnon-confirmableNon-confirmable PUT requests (<xreftarget="hbreq"></xref>)target="hbreq" format="default"/>) with an expected 2.04 (Changed) Response Code (<xreftarget="hbrep"></xref>).target="hbrep" format="default"/>). This procedure occurs between a DOTS agent and its immediate peer DOTS agent. As such, this PUT requestMUST NOT<bcp14>MUST NOT</bcp14> be relayed by a DOTS gateway. The PUT request used for DOTS heartbeatMUST NOT<bcp14>MUST NOT</bcp14> have a 'cuid','cdid,''cdid', or 'mid' Uri-Path.</t><t><figure anchor="hbreq" title="PUT<figure anchor="hbreq"> <name>PUT to Check Peer DOTS Agentis Responding"> <artwork><![CDATA[Is Responding</name> <sourcecode><![CDATA[ Header: PUT (Code=0.03) Uri-Path: ".well-known" Uri-Path: "dots" Uri-Path: "hb" Content-Format: "application/dots+cbor" { "ietf-dots-signal-channel:heartbeat": { "peer-hb-status": true } }]]></artwork> </figure></t>]]></sourcecode> </figure> <t>The mandatory 'peer-hb-status' attribute is set to 'true' (or 'false') toindicatesindicate that a DOTS agent is (or is not) receiving heartbeat messages from its peer in the last (2 *heartbeat-interval)'heartbeat-interval') period. Such information can be used by a peer DOTS agent to detect or confirm connectivity issues and react accordingly. For example, if a DOTS client receives a 2.04 response for its heartbeat messages but no server-initiated heartbeat messages, the DOTS client sets 'peer-hb-status' to 'false'. The DOTS server then will needthento try another strategy for sending the heartbeats (e.g., adjust the heartbeat interval or send a server-initiated heartbeat immediately after receiving a client-initiated heartbeat message).</t><t><figure anchor="hbrep" title="Response<figure anchor="hbrep"> <name>Response to a DOTS HeartbeatRequest"> <artwork><![CDATA[Request</name> <sourcecode><![CDATA[ Header: (Code=2.04)]]></artwork> </figure></t>]]></sourcecode> </figure> <t>DOTS serversMAY<bcp14>MAY</bcp14> trigger their heartbeat requests immediately after receiving heartbeat probes from peer DOTS clients. As a reminder, it is the responsibility of DOTS clients to ensure that on-path translators/firewalls are maintaining a binding so that the same external IP address and/or port number is retained for the DOTS signal channel session.</t> <t>Under normal traffic conditions (i.e., no attack is ongoing), if a DOTS agent does not receive any response from the peer DOTS agent for 'missing-hb-allowed' number of consecutive heartbeat messages, it concludes that the DOTS signal channel session is disconnected. The DOTS clientMUST<bcp14>MUST</bcp14> then try tore-establishreestablish the DOTS signal channel session, preferably by resuming the (D)TLSsession.<list style="empty"> <t hangText="Note 4:">Note:session.</t> <aside> <t>Note: If a new DOTS signal channel session cannot be established, the DOTS clientSHOULD NOT<bcp14>SHOULD NOT</bcp14> retry to establish the DOTS signal channel session more frequently than every 300 seconds (5 minutes) andMUST NOT<bcp14>MUST NOT</bcp14> retry more frequently than every 60 seconds (1 minute). It is recommended that DOTS clients support the means to alert administrators about the failure to establish a (D)TLS session.</t></list></t></aside> <t>In case of a massive DDoS attack that saturates the incoming link(s) to the DOTS client, all traffic from the DOTS server to the DOTS client will likely be dropped, although the DOTS server receives heartbeat requests in addition to DOTS messages sent by the DOTS client. In this scenario, DOTS clientsMUST<bcp14>MUST</bcp14> behave differently to handle message transmission and DOTS signal channel session liveliness during link saturation:</t><t><list style="empty"><ul empty="true" spacing="normal"> <li> <t>The DOTS clientMUST NOT<bcp14>MUST NOT</bcp14> consider the DOTS signal channel session terminated even after a maximum 'missing-hb-allowed' threshold is reached. The DOTS clientSHOULD<bcp14>SHOULD</bcp14> keep on using the current DOTS signal channel session to send heartbeat requests over it, so that the DOTS server knows the DOTS client has not disconnected the DOTS signal channel session.<vspace blankLines="1" />After</t> <t>After the maximum 'missing-hb-allowed' threshold is reached, the DOTS clientSHOULD<bcp14>SHOULD</bcp14> try to establish a new DOTS signal channel session. The DOTS clientSHOULD<bcp14>SHOULD</bcp14> send mitigation requests over the current DOTS signal channel session and, in parallel, send the mitigation requests over the new DOTS signal channel session. This may be handled, for example, by resumption of the (D)TLS session or using 0-RTT mode in DTLS 1.3 to piggyback the mitigation request in the ClientHello message.</t><t><vspace blankLines="1" />As<t>As soon as the link is no longer saturated, if traffic from the DOTS server reaches the DOTS client over the current DOTS signal channel session, the DOTS client can stop the new DOTS signal channel session attempt or if a new DOTS signal channel session is successful then disconnect the current DOTS signal channel session.</t></list></t></li> </ul> <t>If the DOTS server receives traffic from the peer DOTS client (e.g., peer DOTSclient initiatedclient-initiated heartbeats) but the maximum 'missing-hb-allowed' threshold is reached, the DOTS serverMUST NOT<bcp14>MUST NOT</bcp14> consider the DOTS signal channel session disconnected. The DOTS serverMUST<bcp14>MUST</bcp14> keep on using the current DOTS signal channel session so that the DOTS client can send mitigation requests over the current DOTS signal channel session. In this case, the DOTS server can identify that the DOTS client is under attack and that the inbound link to the DOTS client (domain) is saturated. Furthermore, if the DOTS server does not receive a mitigation request from the DOTS client, it implies that the DOTS client has not detected the attack or, if an attack mitigation is in progress, it implies that the applied DDoS mitigation actions are not yeteffective to handleeffectively handling the DDoS attack volume.</t> <t>If the DOTS server does not receive any traffic from the peer DOTS client during the time span required to exhaust the maximum 'missing-hb-allowed' threshold, the DOTS server concludes the session is disconnected. The DOTS server can then triggerpre-configuredpreconfigured mitigation requests for this DOTS client (if any).</t> <t>In DOTS over TCP, the sender of a DOTS heartbeat message has to allow up to 'heartbeat-interval' seconds when waiting for a heartbeat reply. When a failure is detected by a DOTS client, it proceeds with the sessionrecoveryrecovery, following the same approach as the one used for unreliable transports.</t> </section> </section> <section anchor="YANG"title="DOTSnumbered="true" toc="default"> <name>DOTS Signal Channel YANGModules">Modules</name> <t>This document defines a YANG<xref target="RFC7950"></xref>module <xref target="RFC7950" format="default"/> for DOTS mitigation scope, DOTS signal channel session configuration data, DOTS redirection signaling, and DOTS heartbeats.</t> <t>This YANG module (ietf-dots-signal-channel) defines the DOTS client interaction with the DOTS server as seen by the DOTS client. A DOTS server is allowed to update the non-configurable 'ro' entities in the responses. This YANG module is not intended to be used via NETCONF/RESTCONF for DOTS server management purposes; such a module is out of the scope of this document. It serves only to provide a data model and encoding, but not a management data model.</t> <t>A companion YANG module is defined to include a collection of types defined by IANA: "iana-dots-signal-channel" (<xreftarget="iana-yang"></xref>).</t>target="iana-yang" format="default"/>).</t> <sectiontitle="Tree Structure">numbered="true" toc="default"> <name>Tree Structure</name> <t>This document defines the YANG module "ietf-dots-signal-channel" (<xreftarget="yrequest"></xref>),target="yrequest" format="default"/>), which has the following tree structure. A DOTS signal message can be a mitigation, a configuration, a redirect, or a heartbeat message.</t><t><figure> <artwork><![CDATA[module:<sourcecode type="yangtree"><![CDATA[ module: ietf-dots-signal-channel +--rw dots-signal +--rw (message-type)? +--:(mitigation-scope) | +--rw scope* [cuid mid] | +--rw cdid? string | +--rw cuid string | +--rw mid uint32 | +--rw target-prefix* inet:ip-prefix | +--rw target-port-range* [lower-port] | | +--rw lower-port inet:port-number | | +--rw upper-port? inet:port-number | +--rw target-protocol* uint8 | +--rw target-fqdn* inet:domain-name | +--rw target-uri* inet:uri | +--rw alias-name* string | +--rw lifetime? int32 | +--rw trigger-mitigation? boolean | +--ro mitigation-start? uint64 | +--ro status? iana-signal:status | +--ro conflict-information | | +--ro conflict-status? iana-signal:conflict-status | | +--ro conflict-cause? iana-signal:conflict-cause | | +--ro retry-timer? uint32 | | +--ro conflict-scope | | +--ro target-prefix* inet:ip-prefix | | +--ro target-port-range* [lower-port] | | | +--ro lower-port inet:port-number | | | +--ro upper-port? inet:port-number | | +--ro target-protocol* uint8 | | +--ro target-fqdn* inet:domain-name | | +--ro target-uri* inet:uri | | +--ro alias-name* string | | +--ro acl-list* [acl-name] | | | +--ro acl-name | | | | -> /ietf-data:dots-data/dots-client/acls/ | | | | acl/name | | | +--ro acl-type? | | | -> /ietf-data:dots-data/dots-client/acls/ | | | acl/type | | +--ro mid? -> ../../../mid | +--ro bytes-dropped? yang:zero-based-counter64 | +--ro bps-dropped? yang:gauge64 | +--ro pkts-dropped? yang:zero-based-counter64 | +--ro pps-dropped? yang:gauge64 | +--rw attack-status? iana-signal:attack-status +--:(signal-config) | +--rw sid uint32 | +--rw mitigating-config | | +--rw heartbeat-interval | | | +--ro max-value? uint16 | | | +--ro min-value? uint16 | | | +--rw current-value? uint16 | | +--rw missing-hb-allowed | | | +--ro max-value? uint16 | | | +--ro min-value? uint16 | | | +--rw current-value? uint16 | | +--rw probing-rate | | | +--ro max-value? uint16 | | | +--ro min-value? uint16 | | | +--rw current-value? uint16 | | +--rw max-retransmit | | | +--ro max-value? uint16 | | | +--ro min-value? uint16 | | | +--rw current-value? uint16 | | +--rw ack-timeout | | | +--ro max-value-decimal? decimal64 | | | +--ro min-value-decimal? decimal64 | | | +--rw current-value-decimal? decimal64 | | +--rw ack-random-factor | | +--ro max-value-decimal? decimal64 | | +--ro min-value-decimal? decimal64 | | +--rw current-value-decimal? decimal64 | +--rw idle-config | +--rw heartbeat-interval | | +--ro max-value? uint16 | | +--ro min-value? uint16 | | +--rw current-value? uint16 | +--rw missing-hb-allowed | | +--ro max-value? uint16 | | +--ro min-value? uint16 | | +--rw current-value? uint16 | +--rw probing-rate | | +--ro max-value? uint16 | | +--ro min-value? uint16 | | +--rw current-value? uint16 | +--rw max-retransmit | | +--ro max-value? uint16 | | +--ro min-value? uint16 | | +--rw current-value? uint16 | +--rw ack-timeout | | +--ro max-value-decimal? decimal64 | | +--ro min-value-decimal? decimal64 | | +--rw current-value-decimal? decimal64 | +--rw ack-random-factor | +--ro max-value-decimal? decimal64 | +--ro min-value-decimal? decimal64 | +--rw current-value-decimal? decimal64 +--:(redirected-signal) | +--ro alt-server string | +--ro alt-server-record* inet:ip-address +--:(heartbeat) +--rw peer-hb-status boolean]]></artwork> </figure></t>]]></sourcecode> </section> <section anchor="iana-yang"title="IANAnumbered="true" toc="default"> <name>IANA DOTS Signal Channel YANGModule"> <t><figure> <artwork><![CDATA[<CODE BEGINS> file "iana-dots-signal-channel@2019-01-17.yang"Module</name> <sourcecode name="iana-dots-signal-channel@2020-05-28.yang" type="yang" markers="true"><![CDATA[ module iana-dots-signal-channel { yang-version 1.1; namespace "urn:ietf:params:xml:ns:yang:iana-dots-signal-channel"; prefix iana-signal; organization "IANA"; contact "Internet Assigned Numbers Authority Postal: ICANN 12025 Waterfront Drive, Suite 300 Los Angeles, CA 90094-2536 United States of America Tel: +1 310 301 5800 <mailto:iana@iana.org>"; description "This module contains a collection of YANG data types defined by IANA and used for DOTS signal channel protocol. Copyright (c)20192020 IETF Trust and the persons identified as authors of the code. All rights reserved. Redistribution and use in source and binary forms, with or without modification, is permitted pursuant to, and subject to the license terms contained in, the Simplified BSD License set forth in Section 4.c of the IETF Trust's Legal Provisions Relating to IETF Documents (http://trustee.ietf.org/license-info). This version of this YANG module is part of RFCXXXX;8782; see the RFC itself for full legal notices."; revision2019-01-172020-05-28 { description "Initial revision."; reference "RFCXXXX:8782: Distributed Denial-of-Service Open Threat Signaling (DOTS) Signal Channel Specification"; } typedef status { type enumeration { enum attack-mitigation-in-progress { value 1; description "Attack mitigation setup is in progress (e.g., changing the network path tore-routereroute the inbound traffic to DOTS mitigator)."; } enum attack-successfully-mitigated { value 2; description "Attack is being successfully mitigated (e.g., traffic is redirected to a DDoS mitigator and attack traffic is dropped or blackholed)."; } enum attack-stopped { value 3; description "Attack has stopped and the DOTS client can withdraw the mitigation request."; } enum attack-exceeded-capability { value 4; description "Attack has exceeded the mitigation provider capability."; } enum dots-client-withdrawn-mitigation { value 5; description "DOTS client has withdrawn the mitigation request and the mitigation is active but terminating."; } enum attack-mitigation-terminated { value 6; description "Attack mitigation is now terminated."; } enum attack-mitigation-withdrawn { value 7; description "Attack mitigation is withdrawn."; } enum attack-mitigation-signal-loss { value 8; description "Attack mitigation will be triggered for the mitigation request only when the DOTS signal channel session is lost."; } } description "Enumeration for status reported by the DOTS server."; } typedef conflict-status { type enumeration { enum request-inactive-other-active { value 1; description "DOTS Server has detected conflicting mitigation requests from different DOTS clients. This mitigation request is currently inactive until the conflicts are resolved. Another mitigation request is active."; } enum request-active { value 2; description "DOTS Server has detected conflicting mitigation requests from different DOTS clients. This mitigation request is currently active."; } enum all-requests-inactive { value 3; description "DOTS Server has detected conflicting mitigation requests from different DOTS clients. All conflicting mitigation requests are inactive."; } } description "Enumeration for conflict status."; } typedef conflict-cause { type enumeration { enum overlapping-targets { value 1; description "Overlapping targets. conflict-scope provides more details about the exact conflict."; } enum conflict-with-acceptlist { value 2; description "Conflicts with an existing accept-list. This code is returned when the DDoS mitigation detects that some of the source addresses/prefixes listed in the accept-list ACLs are actually attacking the target."; } enum cuid-collision { value 3; description "Conflicts with the cuid used by another DOTS client."; } } description "Enumeration for conflict causes."; } typedef attack-status { type enumeration { enum under-attack { value 1; description "The DOTS client determines that it is still under attack."; } enum attack-successfully-mitigated { value 2; description "The DOTS client determines that the attack is successfully mitigated."; } } description "Enumeration for attack status codes."; } }<CODE ENDS>]]></artwork> </figure></t>]]></sourcecode> </section> <section anchor="yrequest"title="IETFnumbered="true" toc="default"> <name>IETF DOTS Signal Channel YANGModule">Module</name> <t>This module uses the common YANG types defined in <xreftarget="RFC6991"></xref>target="RFC6991" format="default"/> and types defined in <xreftarget="I-D.ietf-dots-data-channel"></xref>.</t> <t><figure> <artwork><![CDATA[<CODE BEGINS> file "ietf-dots-signal-channel@2019-11-13.yang"target="RFC8783" format="default"/>.</t> <sourcecode name="ietf-dots-signal-channel@2020-05-28.yang" type="yang" markers="true"><![CDATA[ module ietf-dots-signal-channel { yang-version 1.1; namespace "urn:ietf:params:xml:ns:yang:ietf-dots-signal-channel"; prefix signal; import ietf-inet-types { prefix inet; reference "Section 4 of RFC 6991"; } import ietf-yang-types { prefix yang; reference "Section 3 of RFC 6991"; } import ietf-dots-data-channel { prefix ietf-data; reference "RFCYYYY:8783: Distributed Denial-of-Service Open Threat Signaling (DOTS) Data Channel Specification"; } import iana-dots-signal-channel { prefix iana-signal; } organization "IETF DDoS Open Threat Signaling (DOTS) Working Group"; contact "WG Web: <https://datatracker.ietf.org/wg/dots/> WG List: <mailto:dots@ietf.org> Editor: Konda, TirumaleswarReddyReddy.K <mailto:TirumaleswarReddy_Konda@McAfee.com> Editor: Mohamed Boucadair <mailto:mohamed.boucadair@orange.com> Author: Prashanth Patil <mailto:praspati@cisco.com> Author: Andrew Mortensen <mailto:amortensen@arbor.net> Author: Nik Teague<mailto:nteague@verisign.com>";<mailto:nteague@ironmountain.co.uk>"; description "This module contains YANG definition for the signaling messages exchanged between a DOTS client and a DOTS server. Copyright (c)20192020 IETF Trust and the persons identified as authors of the code. All rights reserved. Redistribution and use in source and binary forms, with or without modification, is permitted pursuant to, and subject to the license terms contained in, the Simplified BSD License set forth in Section 4.c of the IETF Trust's Legal Provisions Relating to IETF Documents (http://trustee.ietf.org/license-info). This version of this YANG module is part of RFCXXXX;8782; see the RFC itself for full legal notices."; revision2019-11-132020-05-28 { description "Initial revision."; reference "RFCXXXX:8782: Distributed Denial-of-Service Open Threat Signaling (DOTS) Signal Channel Specification"; } /* * Groupings */ grouping mitigation-scope { description "Specifies the scope of the mitigation request."; list scope { key "cuid mid"; description "The scope of the request."; leaf cdid { type string; description "The cdid should be included by a server-domain DOTS gateway to propagate the client domain identification information from the gateway'sclient-facing-sideclient-facing side to the gateway'sserver-facing-side,server-facing side, and from the gateway'sserver-facing-sideserver-facing side to the DOTS server. It may be used by the final DOTS server for policy enforcement purposes."; } leaf cuid { type string; description "A unique identifier that is generated by a DOTS client to prevent request collisions. It is expected that the cuid will remain consistent throughout the lifetime of the DOTS client."; } leaf mid { type uint32; description "Mitigation request identifier. This identifier must be unique for each mitigation request bound to the DOTS client."; } uses ietf-data:target; leaf-list alias-name { type string; description "An alias name that points to a resource."; } leaf lifetime { type int32; units "seconds"; default "3600"; description "Indicates the lifetime of the mitigation request. A lifetime of '0' in a mitigation request is an invalid value. A lifetime of negative one (-1) indicates indefinite lifetime for the mitigation request."; } leaf trigger-mitigation { type boolean; default "true"; description "If set to 'false', DDoS mitigation will not be triggered unless the DOTS signal channel session is lost."; } leaf mitigation-start { type uint64; config false; description "Mitigation start time is represented in seconds relative to 1970-01-01T00:00:00Z in UTC time."; } leaf status { type iana-signal:status; config false; description "Indicates the status of a mitigation request. It must be included in responses only."; } container conflict-information { config false; description "Indicates that a conflict is detected. Must only be used for responses."; leaf conflict-status { type iana-signal:conflict-status; description "Indicates the conflict status."; } leaf conflict-cause { type iana-signal:conflict-cause; description "Indicates the cause of the conflict."; } leaf retry-timer { type uint32; units "seconds"; description "The DOTS client must notre-sendresend the same request that has a conflict before the expiry of this timer."; } container conflict-scope { description "Provides more information about the conflict scope."; uses ietf-data:target { when"../conflict-cause"/dots-signal/scope/conflict-information/" + "conflict-cause = 'overlapping-targets'"; } leaf-list alias-name { when "../../conflict-cause = 'overlapping-targets'"; type string; description "Conflicting alias-name."; } list acl-list { when "../../conflict-cause = 'conflict-with-acceptlist'"; key "acl-name"; description "List of conflicting ACLs as defined in the DOTS data channel. These ACLs are uniquely defined by cuid and acl-name."; leaf acl-name { type leafref { path "/ietf-data:dots-data/ietf-data:dots-client/" + "ietf-data:acls/ietf-data:acl/ietf-data:name"; } description "Reference to the conflicting ACL name bound to a DOTS client."; } leaf acl-type { type leafref { path "/ietf-data:dots-data/ietf-data:dots-client/" + "ietf-data:acls/ietf-data:acl/ietf-data:type"; } description "Reference to the conflicting ACL type bound to a DOTS client."; } } leaf mid { when "../../conflict-cause = 'overlapping-targets'"; type leafref { path "../../../mid"; } description "Reference to the conflicting 'mid' bound to the same DOTS client."; } } } leaf bytes-dropped { type yang:zero-based-counter64; units "bytes"; config false; description "The total dropped byte count for the mitigation request since the attack mitigationiswas triggered. The count wraps around when it reaches the maximum value of counter64 for dropped bytes."; } leaf bps-dropped { type yang:gauge64; config false; description "The average number of dropped bits per second for the mitigation request since the attack mitigationiswas triggered. This should be over five-minute intervals (that is, measuring bytes into five-minute buckets and then averaging these buckets over the time since the mitigation was triggered)."; } leaf pkts-dropped { type yang:zero-based-counter64; config false; description "The total number of dropped packet count for the mitigation request since the attack mitigationiswas triggered. The count wraps around when it reaches the maximum value of counter64 for dropped packets."; } leaf pps-dropped { type yang:gauge64; config false; description "The average number of dropped packets per second for the mitigation request since the attack mitigationiswas triggered. This should be over five-minute intervals (that is, measuring packets into five-minute buckets and then averaging these buckets over the time since the mitigation was triggered)."; } leaf attack-status { type iana-signal:attack-status; description "Indicates the status of an attack as seen by the DOTS client."; } } } grouping config-parameters { description "Subset of DOTS signal channel session configuration."; container heartbeat-interval { description "DOTS agents regularly send heartbeats to each other after mutual authentication is successfully completed in order to keep the DOTS signal channel open."; leaf max-value { type uint16; units "seconds"; config false; description "Maximum acceptable heartbeat-interval value."; } leaf min-value { type uint16; units "seconds"; config false; description "Minimum acceptable heartbeat-interval value."; } leaf current-value { type uint16; units "seconds"; default "30"; description "Current heartbeat-interval value. '0' means that heartbeat mechanism is deactivated."; } } container missing-hb-allowed { description "Maximum number of missing heartbeats allowed."; leaf max-value { type uint16; config false; description "Maximum acceptable missing-hb-allowed value."; } leaf min-value { type uint16; config false; description "Minimum acceptable missing-hb-allowed value."; } leaf current-value { type uint16; default "15"; description "Current missing-hb-allowed value."; } } container probing-rate { description "The limit for sendingnon-confirmableNon-confirmable messages with no response."; leaf max-value { type uint16; units "byte/second"; config false; description "Maximum acceptable probing-rate value."; } leaf min-value { type uint16; units "byte/second"; config false; description "Minimum acceptable probing-rate value."; } leaf current-value { type uint16; units "byte/second"; default "5"; description "Current probing-rate value."; } } container max-retransmit { description "Maximum number of retransmissions of a Confirmable message."; leaf max-value { type uint16; config false; description "Maximum acceptable max-retransmit value."; } leaf min-value { type uint16; config false; description "Minimum acceptable max-retransmit value."; } leaf current-value { type uint16; default "3"; description "Current max-retransmit value."; } } container ack-timeout { description "Initial retransmission timeout value."; leaf max-value-decimal { type decimal64 { fraction-digits 2; } units "seconds"; config false; description "Maximum ack-timeout value."; } leaf min-value-decimal { type decimal64 { fraction-digits 2; } units "seconds"; config false; description "Minimum ack-timeout value."; } leaf current-value-decimal { type decimal64 { fraction-digits 2; } units "seconds"; default "2"; description "Current ack-timeout value."; } } container ack-random-factor { description "Random factor used to influence the timing of retransmissions."; leaf max-value-decimal { type decimal64 { fraction-digits 2; } config false; description "Maximum acceptable ack-random-factor value."; } leaf min-value-decimal { type decimal64 { fraction-digits 2; } config false; description "Minimum acceptable ack-random-factor value."; } leaf current-value-decimal { type decimal64 { fraction-digits 2; } default "1.5"; description "Current ack-random-factor value."; } } } grouping signal-config { description "DOTS signal channel session configuration."; leaf sid { type uint32; mandatory true; description "An identifier for the DOTS signal channel session configuration data."; } container mitigating-config { description "Configuration parameters to use when a mitigation is active."; uses config-parameters; } container idle-config { description "Configuration parameters to use when no mitigation is active."; uses config-parameters; } } grouping redirected-signal { description "Grouping for the redirected signaling."; leaf alt-server { type string; config false; mandatory true; description "FQDN of an alternate server."; } leaf-list alt-server-record { type inet:ip-address; config false; description "List of records for the alternate server."; } } /* * Main Container for DOTS Signal Channel */ container dots-signal { description "Main container for DOTS signal message. A DOTS signal message can be a mitigation, a configuration, or a redirected signal message."; choice message-type { description "Can be a mitigation, a configuration, or a redirect message."; case mitigation-scope { description "Mitigation scope of a mitigation message."; uses mitigation-scope; } case signal-config { description "Configuration message."; uses signal-config; } case redirected-signal { description "Redirected signaling."; uses redirected-signal; } case heartbeat { description "DOTS heartbeats."; leaf peer-hb-status { type boolean; mandatory true; description "Indicates whether a DOTS agent receives heartbeats from its peer. The value is set to 'true' if the DOTS agent is receiving heartbeat messages from its peer."; } } } } }<CODE ENDS>]]></artwork> </figure></t>]]></sourcecode> </section> </section> <section anchor="mapping"title="YANG/JSONnumbered="true" toc="default"> <name>YANG/JSON Mapping Parameters toCBOR">CBOR</name> <t>All parameters in the payload of the DOTS signal channelMUST<bcp14>MUST</bcp14> be mapped to CBOR types as shown inTable 4<xref target="cbor-key-values" format="default"/> and are assigned an integer key to save space.<list style="symbols"> <t>Note:</t> <ul empty="true" spacing="normal"> <li>Note: Implementers must check that the mapping output provided by their YANG-to-CBOR encoding schemes is aligned with the content ofTable 4.<xref target="cbor-key-values" format="default"/>. For example, some CBOR and JSON types for enumerations and the 64-bit quantities can differ depending on the encoderused.</t> </list></t>used.</li> </ul> <t>The CBOR key values are divided into two types: comprehension-required and comprehension-optional. DOTS agents can safely ignore comprehension-optional values they don't understand, but they cannot successfully process a request if it contains comprehension-required values that are not understood. The 4.00 responseSHOULD<bcp14>SHOULD</bcp14> include a diagnostic payload describing the unknown comprehension-required CBOR key values. The initial set of CBOR key values defined in this specification are of type comprehension-required.</t><t><figure> <artwork><![CDATA[ +----------------------+-------------+-----+---------------+--------+ | Parameter Name | YANG | CBOR| CBOR Major | JSON | | | Type |<table anchor="cbor-key-values"> <name>CBOR Key| Type & |Values Used in DOTS Signal Channel Messages & Their Mappings to JSON and YANG</name> <thead> <tr> <th>Parameter Name</th> <th>YANG Type</th> <th>CBOR Key</th> <th>CBOR Major Type| | | | | Information | | +----------------------+-------------+-----+---------------+--------+ | ietf-dots-signal-cha | | | | | | nnel:mitigation-scope| container | 1 | 5 map | Object | | scope | list | 2 | 4 array | Array | | cdid | string | 3 | 3& Information</th> <th>JSON Type</th> </tr> </thead> <tbody> <tr> <td><t>ietf-dots-signal-<br/>channel:mitigation-scope</t></td> <td>container</td> <td>1</td> <td>5 map</td> <td>Object</td> </tr> <tr> <td>scope</td> <td>list</td> <td>2</td> <td>4 array</td> <td>Array</td> </tr> <tr> <td>cdid</td> <td>string</td> <td>3</td> <td>3 textstring | String | | cuid | string | 4 | 3string</td> <td>String</td> </tr> <tr> <td>cuid</td> <td>string</td> <td>4</td> <td>3 textstring | String | | mid | uint32 | 5 | 0 unsigned | Number | | target-prefix | leaf-list | 6 | 4 array | Array | | | inet: | | | | | | ip-prefix | | 3string</td> <td>String</td> </tr> <tr> <td>mid</td> <td>uint32</td> <td>5</td> <td>0 unsigned</td> <td>Number</td> </tr> <tr> <td rowspan="2">target-prefix</td> <td>leaf-list</td> <td>6</td> <td>4 array</td> <td>Array</td> </tr> <tr> <td>inet:ip-prefix</td> <td/> <td>3 textstring | String | | target-port-range | list | 7 | 4 array | Array | | lower-port | inet: | | | | | | port-number| 8 | 0 unsigned | Number | | upper-port | inet: | | | | | | port-number| 9 | 0 unsigned | Number | | target-protocol | leaf-list | 10 |string</td> <td>String</td> </tr> <tr> <td>target-port-range</td> <td>list</td> <td>7</td> <td>4 array</td> <td>Array</td> </tr> <tr> <td>lower-port</td> <td>inet:port-number</td> <td>8</td> <td>0 unsigned</td> <td>Number</td> </tr> <tr> <td>upper-port</td> <td>inet:port-number</td> <td>9</td> <td>0 unsigned</td> <td>Number</td> </tr> <tr> <td rowspan="2">target-protocol</td> <td>leaf-list</td> <td>10</td> <td>4 array</td> <td>Array</td> </tr> <tr> <td>uint8</td> <td/> <td>0 unsigned</td> <td>Number</td> </tr> <tr> <td rowspan="2">target-fqdn</td> <td>leaf-list</td> <td>11</td> <td>4 array</td> <td>Array</td> </tr> <tr> <td>inet:domain-name</td> <td/> <td>3 text string</td> <td>String</td> </tr> <tr> <td rowspan="2">target-uri</td> <td>leaf-list</td> <td>12</td> <td>4 array</td> <td>Array</td> </tr> <tr> <td>inet:uri</td> <td/> <td>3 text string</td> <td>String</td> </tr> <tr> <td rowspan="2">alias-name</td> <td>leaf-list</td> <td>13</td> <td>4 array</td> <td>Array</td> </tr> <tr> <td>string</td> <td/> <td>3 text string</td> <td>String</td> </tr> <tr> <td rowspan="2">lifetime</td> <td rowspan="2">int32</td> <td rowspan="2">14</td> <td>0 unsigned</td> <td>Number</td> </tr> <tr> <td>1 negative</td> <td>Number</td> </tr> <tr> <td>mitigation-start</td> <td>uint64</td> <td>15</td> <td>0 unsigned</td> <td>String</td> </tr> <tr> <td>status</td> <td>enumeration</td> <td>16</td> <td>0 unsigned</td> <td>String</td> </tr> <tr> <td>conflict-information</td> <td>container</td> <td>17</td> <td>5 map</td> <td>Object</td> </tr> <tr> <td>conflict-status</td> <td>enumeration</td> <td>18</td> <td>0 unsigned</td> <td>String</td> </tr> <tr> <td>conflict-cause</td> <td>enumeration</td> <td>19</td> <td>0 unsigned</td> <td>String</td> </tr> <tr> <td>retry-timer</td> <td>uint32</td> <td>20</td> <td>0 unsigned</td> <td>String</td> </tr> <tr> <td>conflict-scope</td> <td>container</td> <td>21</td> <td>5 map</td> <td>Object</td> </tr> <tr> <td>acl-list</td> <td>list</td> <td>22</td> <td>4 array</td> <td>Array</td> </tr> <tr> <td>acl-name</td> <td>leafref</td> <td>23</td> <td>3 text string</td> <td>String</td> </tr> <tr> <td>acl-type</td> <td>leafref</td> <td>24</td> <td>3 text string</td> <td>String</td> </tr> <tr> <td>bytes-dropped</td> <td><t>yang:zero-based-<br/>counter64</t></td> <td>25</td> <td>0 unsigned</td> <td>String</td> </tr> <tr> <td>bps-dropped</td> <td>yang:gauge64</td> <td>26</td> <td>0 unsigned</td> <td>String</td> </tr> <tr> <td>pkts-dropped</td> <td><t>yang:zero-based-<br/>counter64</t></td> <td>27</td> <td>0 unsigned</td> <td>String</td> </tr> <tr> <td>pps-dropped</td> <td>yang:gauge64</td> <td>28</td> <td>0 unsigned</td> <td>String</td> </tr> <tr> <td>attack-status</td> <td>enumeration</td> <td>29</td> <td>0 unsigned</td> <td>String</td> </tr> <tr> <td><t>ietf-dots-signal-<br/>channel:signal-config</t></td> <td>container</td> <td>30</td> <td>5 map</td> <td>Object</td> </tr> <tr> <td>sid</td> <td>uint32</td> <td>31</td> <td>0 unsigned</td> <td>Number</td> </tr> <tr> <td>mitigating-config</td> <td>container</td> <td>32</td> <td>5 map</td> <td>Object</td> </tr> <tr> <td>heartbeat-interval</td> <td>container</td> <td>33</td> <td>5 map</td> <td>Object</td> </tr> <tr> <td>max-value</td> <td>uint16</td> <td>34</td> <td>0 unsigned</td> <td>Number</td> </tr> <tr> <td>min-value</td> <td>uint16</td> <td>35</td> <td>0 unsigned</td> <td>Number</td> </tr> <tr> <td>current-value</td> <td>uint16</td> <td>36</td> <td>0 unsigned</td> <td>Number</td> </tr> <tr> <td>missing-hb-allowed</td> <td>container</td> <td>37</td> <td>5 map</td> <td>Object</td> </tr> <tr> <td>max-retransmit</td> <td>container</td> <td>38</td> <td>5 map</td> <td>Object</td> </tr> <tr> <td>ack-timeout</td> <td>container</td> <td>39</td> <td>5 map</td> <td>Object</td> </tr> <tr> <td>ack-random-factor</td> <td>container</td> <td>40</td> <td>5 map</td> <td>Object</td> </tr> <tr> <td>max-value-decimal</td> <td>decimal64</td> <td>41</td> <td>6 tag 4array | Array | | | uint8 | | 0 unsigned | Number | | target-fqdn | leaf-list | 11 |[-2, integer]</td> <td>String</td> </tr> <tr> <td>min-value-decimal</td> <td>decimal64</td> <td>42</td> <td>6 tag 4array | Array | | | inet: | | | | | | domain-name| | 3 text string | String | | target-uri | leaf-list | 12 |[-2, integer]</td> <td>String</td> </tr> <tr> <td>current-value-decimal</td> <td>decimal64</td> <td>43</td> <td>6 tag 4array | Array | | | inet:uri | | 3[-2, integer]</td> <td>String</td> </tr> <tr> <td>idle-config</td> <td>container</td> <td>44</td> <td>5 map</td> <td>Object</td> </tr> <tr> <td rowspan="2">trigger-mitigation</td> <td rowspan="2">boolean</td> <td rowspan="2">45</td> <td>7 bits 20</td> <td>False</td> </tr> <tr> <td>7 bits 21</td> <td>True</td> </tr> <tr> <td><t>ietf-dots-signal-<br/>channel:redirected-signal</t></td> <td>container</td> <td>46</td> <td>5 map</td> <td>Object</td> </tr> <tr> <td>alt-server</td> <td>string</td> <td>47</td> <td>3 textstring | String | | alias-name | leaf-list | 13 | 4 array | Array | | | string | | 3string</td> <td>String</td> </tr> <tr> <td rowspan="2">alt-server-record</td> <td>leaf-list</td> <td>48</td> <td>4 array</td> <td>Array</td> </tr> <tr> <td>inet:ip-address</td> <td/> <td>3 textstring | String | | lifetime | int32 | 14 | 0 unsigned | Number | | | | | 1 negative | Number | | mitigation-start | uint64 | 15 | 0 unsigned | String | | status | enumeration | 16 | 0 unsigned | String | | conflict-information | container | 17 | 5 map | Object | | conflict-status | enumeration | 18 | 0 unsigned | String | | conflict-cause | enumeration | 19 | 0 unsigned | String | | retry-timer | uint32 | 20 | 0 unsigned | Number | | conflict-scope | container | 21 | 5 map | Object | | acl-list | list | 22 | 4 array | Array | | acl-name | leafref | 23 | 3 text string | String | | acl-type | leafref | 24 | 3 text string | String | | bytes-dropped | yang:zero- | | | | | | based- | | | | | | counter64 | 25 | 0 unsigned | String | | bps-dropped | yang:gauge64| 26 | 0 unsigned | String | | pkts-dropped | yang:zero- | | | | | | based- | | | | | | counter64 | 27 | 0 unsigned | String | | pps-dropped | yang:gauge64| 28 | 0 unsigned | String | | attack-status | enumeration | 29 | 0 unsigned | String | | ietf-dots-signal- | | | | | | channel:signal-config| container | 30 | 5 map | Object | | sid | uint32 | 31 | 0 unsigned | Number | | mitigating-config | container | 32 | 5 map | Object | | heartbeat-interval | container | 33 | 5 map | Object | | max-value | uint16 | 34 | 0 unsigned | Number | | min-value | uint16 | 35 | 0 unsigned | Number | | current-value | uint16 | 36 | 0 unsigned | Number | | missing-hb-allowed | container | 37 | 5 map | Object | | max-retransmit | container | 38 | 5 map | Object | | ack-timeout | container | 39 | 5 map | Object | | ack-random-factor | container | 40 | 5 map | Object | | max-value-decimal | decimal64 | 41 | 6 tag 4 | | | | | | [-2, integer]| String | | min-value-decimal | decimal64 | 42 | 6 tag 4 | | | | | | [-2, integer]| String | | current-value-decimal| decimal64 | 43 | 6 tag 4 | | | | | | [-2, integer]| String | | idle-config | container | 44 | 5 map | Object | | trigger-mitigation | boolean | 45 | 7 bits 20 | False | | | | | 7 bits 21 | True | | ietf-dots-signal-cha | | | | | |nnel:redirected-signal| container | 46 | 5 map | Object | | alt-server | string | 47 | 3 text string | String | | alt-server-record | leaf-list | 48 | 4 array | Array | | | inet: | | | | | | ip-address | | 3 text string | String | | ietf-dots-signal-cha | | | | | | nnel:heartbeat | container | 49 | 5 map | Object | | probing-rate | container | 50 | 5 map | Object | | peer-hb-status | boolean | 51 | 7 bits 20 | False | | | | | 7 bits 21 | True | +----------------------+-------------+-----+---------------+--------+ Table 4: CBOR Key Values Used in DOTS Signal Channel Messages & Their Mappings to JSON and YANG]]></artwork> </figure></t> </section> <section anchor="profile" title="(D)TLS Protocol Profile and Performance Considerations"> <section title="(D)TLS Protocol Profile"> <t>This section defines the (D)TLS protocol profile of DOTS signal channel over (D)TLS and DOTS data channel over TLS.</t> <t>There are known attacks on (D)TLS, such as man-in-the-middle and protocol downgrade attacks. These are general attacks on (D)TLS and, as such, they are not specific to DOTS over (D)TLS; refer to the (D)TLS RFCs for discussion of these security issues. DOTS agents MUST adhere to the (D)TLS implementation recommendations and security considerations of <xref target="RFC7525"></xref> except with respect to (D)TLS version. Since DOTS signal channel encryption relying upon (D)TLS is virtually a green-field deployment, DOTS agents MUST implement only (D)TLS 1.2 or later.</t> <t>When a DOTS client is configured with a domain name of the DOTS server, and connects to its configured DOTS server, the server may present it with a PKIX certificate. In order to ensure proper authentication, a DOTS client MUST verify the entire certification path per <xref target="RFC5280"></xref>. Additionally, the DOTS client MUST use <xref target="RFC6125"></xref> validation techniques to compare the domain name with the certificate provided. Certification authorities that issue DOTS server certificates SHOULD support the DNS-ID and SRV-ID identifier types. DOTS server SHOULD prefer the use of DNS-ID and SRV-ID over CN-ID identifier types in certificate requests (as described in Section 2.3 of <xref target="RFC6125"></xref>) and the wildcard character '*' SHOULD NOT be included in the presented identifier. DOTS doesn't use URI-IDs for server identity verification.</t> <t>A key challenge to deploying DOTS is the provisioning of DOTS clients, including the distribution of keying material to DOTS clients to enable the required mutual authentication of DOTS agents. Enrollment over Secure Transport (EST) <xref target="RFC7030"></xref> defines a method of certificate enrollment by which domains operating DOTS servers may provide DOTS clients with all the necessary cryptographic keying material, including a private key and a certificate to authenticate themselves. One deployment option is DOTS clients behave as EST clients for certificate enrollment from an EST server provisioned by the mitigation provider. This document does not specify which EST or other mechanism the DOTS client uses to achieve initial enrollment.</t> <t>The Server Name Indication (SNI) extension <xref target="RFC6066"></xref> defines a mechanism for a client to tell a (D)TLS server the name of the server it wants to contact. This is a useful extension for hosting environments where multiple virtual servers are reachable over a single IP address. The DOTS client may or may not know if it is interacting with a DOTS server in a virtual server hosting environment, so the DOTS client SHOULD include the DOTS server FQDN in the SNI extension.</t> <t>Implementations compliant with this profile MUST implement all of the following items:</t> <t><list style="symbols"> <t>DTLS record replay detection (Section 3.3 of <xref target="RFC6347"></xref>) or an equivalent mechanism to protect against replay attacks.</t> <t>DTLS session resumption without server-side state to resume session and convey the DOTS signal.</t> <t>At least one of raw public keys <xref target="RFC7250"></xref> or PSK handshake <xref target="RFC4279"></xref> with (EC)DHE key exchange which reduces the size of the ServerHello, and can be used by DOTS agents that cannot obtain certificates.</t> </list></t> <t>Implementations compliant with this profile SHOULD implement all of the following items to reduce the delay required to deliver a DOTS signal channel message:</t> <t><list style="symbols"> <t>TLS False Start <xref target="RFC7918"></xref> which reduces round-trips by allowing the TLS client's second flight of messages (ChangeCipherSpec) to also contain the DOTS signal. TLS False Start is formally defined for use with TLS, but the same technique is applicable to DTLS as well.</t> <t>Cached Information Extension <xref target="RFC7924"></xref> which avoids transmitting the server's certificate and certificate chain if the client has cached that information from a previous TLS handshake.</t> </list></t> <t>Compared to UDP, DOTS signal channel over TCP requires an additional round-trip time (RTT) of latency to establish a TCP connection. DOTS implementations are encouraged to implement TCP Fast Open <xref target="RFC7413"></xref> to eliminate that RTT.</t> </section> <section anchor="DTLS" title="(D)TLS 1.3 Considerations"> <t>TLS 1.3 provides critical latency improvements for connection establishment over TLS 1.2. The DTLS 1.3 protocol <xref target="I-D.ietf-tls-dtls13"></xref> is based upon the TLS 1.3 protocol and provides equivalent security guarantees. (D)TLS 1.3 provides two basic handshake modes the DOTS signal channel can take advantage of:</t> <t><list style="symbols"> <t>A full handshake mode in which a DOTS client can send a DOTS mitigation request message after one round trip and the DOTS server immediately responds with a DOTS mitigation response. This assumes no packet loss is experienced.</t> <t>0-RTT mode in which the DOTS client can authenticate itself and send DOTS mitigation request messages in the first message, thus reducing handshake latency. 0-RTT only works if the DOTS client has previously communicated with that DOTS server, which is very likely with the DOTS signal channel. <vspace blankLines="1" />The DOTS client has to establish a (D)TLS session with the DOTS server during 'idle' time and share a PSK. <vspace blankLines="1" />During a DDoS attack, the DOTS client can use the (D)TLS session to convey the DOTS mitigation request message and, if there is no response from the server after multiple retries, the DOTS client can resume the (D)TLS session in 0-RTT mode using PSK. <vspace blankLines="1" />DOTS servers that support (D)TLS 1.3 MAY allow DOTS clients to send early data (0-RTT). DOTS clients MUST NOT send "CoAP Ping" as early data; such messages MUST be rejected by DOTS servers. Section 8 of <xref target="RFC8446"></xref> discusses some mechanisms to implement to limit the impact of replay attacks on 0-RTT data. If the DOTS server accepts 0-RTT, it MUST implement one of these mechanisms to prevent replay at the TLS layer. A DOTS server can reject 0-RTT by sending a TLS HelloRetryRequest. <vspace blankLines="1" />The DOTS signal channel messages sent as early data by the DOTS client are idempotent requests. As a reminder, the Message ID (Section 3 of <xref target="RFC7252"></xref>) is changed each time a new CoAP request is sent, and the Token (Section 5.3.1 of <xref target="RFC7252"></xref>) is randomized in each CoAP request. The DOTS server(s) MUST use the Message ID and the Token in the DOTS signal channel message to detect replay of early data at the application layer, and accept 0-RTT data at most once from the same DOTS client. This anti-replay defense requires sharing the Message ID and the Token in the 0-RTT data between DOTS servers in the DOTS server domain. DOTS servers do not rely on transport coordinates to identify DOTS peers. As specified in <xref target="post"></xref>, DOTS servers couple the DOTS signal channel sessions using the DOTS client identity and optionally the 'cdid' parameter value. Furthermore, 'mid' value is monotonically increased by the DOTS client for each mitigation request, attackers replaying mitigation requests with lower numeric 'mid' values and overlapping scopes with mitigation requests having higher numeric 'mid' values will be rejected systematically by the DOTS server. Likewise, 'sid' value is monotonically increased by the DOTS client for each configuration request (<xref target="convey"></xref>), attackers replaying configuration requests with lower numeric 'sid' values will be rejected by the DOTS server if it maintains a higher numeric 'sid' value for this DOTS client. <vspace blankLines="1" />Owing to the aforementioned protections, all DOTS signal channel requests are safe to transmit in TLS 1.3 as early data. Refer to <xref target="I-D.boucadair-dots-earlydata"></xref> for more details. <vspace blankLines="1" />A simplified TLS 1.3 handshake with 0-RTT DOTS mitigation request message exchange is shown in <xref target="Figure24"></xref>.<figure anchor="Figure24" title="A Simplified TLS 1.3 Handshake with 0-RTT"> <artwork align="left"><![CDATA[ DOTS Client DOTS Server ClientHello (0-RTT DOTS signal message) --------> ServerHello {EncryptedExtensions} {Finished} <-------- [DOTS signal message] (end_of_early_data) {Finished} --------> [DOTS signal message] <-------> [DOTS signal message] Note that: () Indicates messages protected 0-RTT keys {} Indicates messages protected using handshake keys [] Indicates messages protected using 1-RTT keys]]></artwork> </figure></t> </list></t> </section> <section anchor="mtu" title="DTLS MTU and Fragmentation"> <t>To avoid DOTS signal message fragmentation and the subsequent decreased probability of message delivery, DOTS agents MUST ensure that the DTLS record fit within a single datagram. As a reminder, DTLS handles fragmentation and reassembly only for handshake messages and not for the application data (Section 4.1.1 of <xref target="RFC6347"></xref>). If the PMTU cannot be discovered, DOTS agents MUST assume a PMTU of 1280 bytes, as IPv6 requires that every link in the Internet have an MTU of 1280 octets or greater as specified in <xref target="RFC8200"></xref>. If IPv4 support on legacy or otherwise unusual networks is a consideration and the PMTU is unknown, DOTS implementations MAY assume on a PMTU of 576 bytes for IPv4 datagrams, as every IPv4 host must be capable of receiving a packet whose length is equal to 576 bytes as discussed in <xref target="RFC0791"></xref> and <xref target="RFC1122"></xref>.</t> <t>The DOTS client must consider the amount of record expansion expected by the DTLS processing when calculating the size of CoAP message that fits within the path MTU. Path MTU MUST be greater than or equal to [CoAP message size + DTLS 1.2 overhead of 13 octets + authentication overhead of the negotiated DTLS cipher suite + block padding] (Section 4.1.1.1 of <xref target="RFC6347"></xref>). If the total request size exceeds the path MTU then the DOTS client MUST split the DOTS signal into separate messages; for example, the list of addresses in the 'target-prefix' parameter could be split into multiple lists and each list conveyed in a new PUT request.</t> <t>Implementation Note: DOTS choice of message size parameters works well with IPv6 and with most of today's IPv4 paths. However, with IPv4, it is harder to safely make sure that there is no IP fragmentation. If the IPv4 path MTU is unknown, implementations may want to limit themselves to more conservative IPv4 datagram sizes such as 576 bytes, as per <xref target="RFC0791"></xref>.</t> </section> </section> <section anchor="mutauth" title="Mutual Authentication of DOTS Agents & Authorization of DOTS Clients"> <t>(D)TLS based upon client certificate can be used for mutual authentication between DOTS agents. If, for example, a DOTS gateway is involved, DOTS clients and DOTS gateways must perform mutual authentication; only authorized DOTS clients are allowed to send DOTS signals to a DOTS gateway. The DOTS gateway and the DOTS server must perform mutual authentication; a DOTS server only allows DOTS signal channel messages from an authorized DOTS gateway, thereby creating a two-link chain of transitive authentication between the DOTS client and the DOTS server.</t> <t>The DOTS server should support certificate-based client authentication. The DOTS client should respond to the DOTS server's TLS CertificateRequest message with the PKIX certificate held by the DOTS client. DOTS client certificate validation must be performed as per <xref target="RFC5280"></xref> and the DOTS client certificate must conform to the <xref target="RFC5280"></xref> certificate profile. If a DOTS client does not support TLS client certificate authentication, it must support pre-shared key based or raw public key based client authentication.</t> <t><figure anchor="Figure12" title="Example of Authentication and Authorization of DOTS Agents"> <artwork align="center"><![CDATA[ +---------------------------------------------+ | example.com domain +---------+ | | | AAA | | | +---------------+ | Server | | | | Application | +------+--+ | | | server +<---------------+ ^ | | | (DOTS client) | | | | | +---------------+ | | | | V V | example.net domain | +-----+----+--+ | +---------------+ | +--------------+ | | | | | | | Guest +<----x---->+ DOTS +<------>+ DOTS | | | (DOTS client)| | gateway | | | server | | +--------------+ | | | | | | +----+--------+ | +---------------+ | ^ | | | | | +----------------+ | | | | DDoS detector | | | | | (DOTS client) +<-------------+ | | +----------------+ | +---------------------------------------------+ ]]></artwork> </figure></t> <t>In the example depicted in <xref target="Figure12"></xref>, the DOTS gateway and DOTS clients within the 'example.com' domain mutually authenticate. After the DOTS gateway validates the identity of a DOTS client, it communicates with the AAA server in the 'example.com' domain to determine if the DOTS client is authorized to request DDoS mitigation. If the DOTS client is not authorized, a 4.01 (Unauthorized) is returned in the response to the DOTS client. In this example, the DOTS gateway only allows the application server and DDoS attack detector to request DDoS mitigation, but does not permit the user of type 'guest' to request DDoS mitigation.</t> <t>Also, DOTS gateways and servers located in different domains must perform mutual authentication (e.g., using certificates). A DOTS server will only allow a DOTS gateway with a certificate for a particular domain to request mitigation for that domain. In reference to <xref target="Figure12"></xref>, the DOTS server only allows the DOTS gateway to request mitigation for 'example.com' domain and not for other domains.</t> </section> <section anchor="IANA" title="IANA Considerations"> <t></t> <section anchor="port" title="DOTS Signal Channel UDP and TCP Port Number"> <t>IANA is requested to assign the port number TBD to the DOTS signal channel protocol for both UDP and TCP from the "Service Name and Transport Protocol Port Number Registry" available at https://www.iana.org/assignments/service-names-port-numbers/service-names-port-numbers.xhtml.</t> <t>The assignment of port number 4646 is strongly suggested, as 4646 is the ASCII decimal value for ".." (DOTS).</t> </section> <section anchor="uri" title="Well-Known 'dots' URI"> <t>This document requests IANA to register the 'dots' well-known URI (Table 5) in the Well-Known URIs registry (https://www.iana.org/assignments/well-known-uris/well-known-uris.xhtml) as defined by <xref target="RFC8615"></xref>:<figure> <artwork><![CDATA[ +----------+----------------+---------------------+-----------------+ | URI | Change | Specification | Related | | suffix | controller | document(s) | information | +----------+----------------+---------------------+-----------------+ | dots | IETF | [RFCXXXX] | None | +----------+----------------+---------------------+-----------------+ Table 5: 'dots' well-known URI]]></artwork> </figure></t> </section> <section anchor="MediaReg" title="Media Type Registration"> <t>This document requests IANA to register the <spanx style="verb">application/dots+cbor</spanx> media type in the "Media Types" registry <xref target="IANA.MediaTypes"></xref> in the manner described in <xref target="RFC6838"></xref>, which can be used to indicate that the content is a DOTS signal channel object: <?rfc subcompact="yes"?><list style="symbols"> <t>Type name: application</t> <t>Subtype name: dots+cbor</t> <t>Required parameters: N/A</t> <t>Optional parameters: N/A</t> <t>Encoding considerations: binary</t> <t>Security considerations: See the Security Considerations section of [RFCXXXX]</t> <t>Interoperability considerations: N/A</t> <t>Published specification: [RFCXXXX]</t> <t>Applications that use this media type: DOTS agents sending DOTS messages over CoAP over (D)TLS.</t> <t>Fragment identifier considerations: N/A</t> <t>Additional information:<list style="empty"> <t>Magic number(s): N/A</t> <t>File extension(s): N/A</t> <t>Macintosh file type code(s): N/A</t> </list> <vspace /></t> <t>Person & email address to contact for further information: <vspace /> IESG, iesg@ietf.org</t> <t>Intended usage: COMMON</t> <t>Restrictions on usage: none</t> <t>Author: See Authors' Addresses section.</t> <t>Change controller: IESG</t> <t>Provisional registration? No</t> </list></t> <?rfc subcompact="no"?> </section> <section anchor="IANACoAPContentFormatRegistration" title="CoAP Content-Formats Registration"> <t>This document requests IANA to register the CoAP Content-Format ID for the "application/dots+cbor" media type in the "CoAP Content-Formats" registry <xref target="IANA.CoAP.Content-Formats"></xref> (0-255 range):<?rfc subcompact="yes"?></t> <t><list style="symbols"> <t>Media Type: application/dots+cbor</t> <t>Encoding: -</t> <t>Id: TBD1</t> <t>Reference: [RFCXXXX]</t> </list></t> <?rfc subcompact="no"?> </section> <section anchor="IANACBORTagAssignment" title="CBOR Tag Registration"> <t>This section defines the DOTS CBOR tag as another means for applications to declare that a CBOR data structure is a DOTS signal channel object. Its use is optional and is intended for use in cases in which this information would not otherwise be known. DOTS CBOR tag is not required for DOTS signal channel protocol version specified in this document. If present, the DOTS tag MUST prefix a DOTS signal channel object.</t> <t>This document requests IANA to register the DOTS signal channel CBOR tag in the "CBOR Tags" registry <xref target="IANA.CBOR.Tags"></xref> using the 24-255 range:<?rfc subcompact="yes"?></t> <t><list style="symbols"> <t>CBOR Tag: TBD2 (please assign the same value as the Content-Format)</t> <t>Data Item: DDoS Open Threat Signaling (DOTS) signal channel object</t> <t>Semantics: DDoS Open Threat Signaling (DOTS) signal channel object, as defined in [RFCXXXX]</t> <t>Description of Semantics: [RFCXXXX]</t> </list></t> <?rfc subcompact="no"?> </section> <section anchor="reg" title="DOTS Signal Channel Protocol Registry"> <t>The document requests IANA to create a new registry, entitled "DOTS Signal Channel Registry". The following sections define sub-registries.</t> <section anchor="map" title="DOTS Signal Channel CBOR Key Values Sub-Registry"> <t>The document requests IANA to create a new sub-registry, entitled "DOTS Signal Channel CBOR Key Values".</t> <t>The structure of this sub-registry is provided in <xref target="format"></xref>. <xref target="initial"></xref> provides how the registry is initially populated with the values in Table 4.</t> <section anchor="format" title="Registration Template"> <t><list style="hanging"> <t hangText="Parameter name:"><vspace />Parameter name as used in the DOTS signal channel.</t> <t hangText="CBOR Key Value:"><vspace />Key value for the parameter. The key value MUST be an integer in the 1-65535 range. The key values of the comprehension-required range (0x0001 - 0x3FFF) and of the comprehension-optional range (0x8000 - 0xBFFF) are assigned by IETF Review (Section 4.8 of <xref target="RFC8126"></xref>). The key values of the comprehension-optional range (0x4000 - 0x7FFF) are assigned by Specification Required (Section 4.6 of <xref target="RFC8126"></xref>) and of the comprehension-optional range (0xC000 - 0xFFFF) are reserved for Private Use (Section 4.1 of <xref target="RFC8126"></xref>).<vspace blankLines="1" />Registration requests for the 0x4000 - 0x7FFF range are evaluated after a three-week review period on the dots-signal-reg-review@ietf.org mailing list, on the advice of one or more Designated Experts. However, to allow for the allocation of values prior to publication, the Designated Experts may approve registration once they are satisfied that such a specification will be published. New registration requests should be sent in the form of an email to the review mailing list; the request should use an appropriate subject (e.g., "Request to register CBOR Key Value for DOTS: example"). IANA will only accept new registrations from the Designated Experts, and will check that review was requested on the mailing list in accordance with these procedures.<vspace blankLines="1" />Within the review period, the Designated Experts will either approve or deny the registration request, communicating this decision to the review list and IANA. Denials should include an explanation and, if applicable, suggestions as to how to make the request successful. Registration requests that are undetermined for a period longer than 21 days can be brought to the IESG's attention (using the iesg@ietf.org mailing list) for resolution.<vspace blankLines="1" />Criteria that should be applied by the Designated Experts includes determining whether the proposed registration duplicates existing functionality, whether it is likely to be of general applicability or whether it is useful only for a single use case, and whether the registration description is clear. IANA must only accept registry updates to the 0x4000 - 0x7FFF range from the Designated Experts and should direct all requests for registration to the review mailing list. It is suggested that multiple Designated Experts be appointed. In cases where a registration decision could be perceived as creating a conflict of interest for a particular Expert, that Expert should defer to the judgment of the other Experts.</t> <t hangText="CBOR Major Type:"><vspace />CBOR Major type and optional tag for the parameter.</t> <t hangText="Change Controller:"><vspace />For Standards Track RFCs, list the "IESG". For others, give the name of the responsible party. Other details (e.g., email address) may also be included.</t> <t hangText="Specification Document(s):"><vspace />Reference to the document or documents that specify the parameter, preferably including URIs that can be used to retrieve copies of the documents. An indication of the relevant sections may also be included but is not required.</t> </list></t> </section> <section anchor="initial" title="Initial Sub-Registry Content"> <t><figure> <artwork><![CDATA[ +----------------------+-------+-------+------------+---------------+ | Parameter Name | CBOR | CBOR | Change | Specification | | | Key | Major | Controller | Document(s) | | | Value | Type | | | +----------------------+-------+-------+------------+---------------+ | ietf-dots-signal-chan| 1 | 5 | IESG | [RFCXXXX] | | nel:mitigation-scope | | | | | | scope | 2 | 4 | IESG | [RFCXXXX] | | cdid | 3 | 3 | IESG | [RFCXXXX] | | cuid | 4 | 3 | IESG | [RFCXXXX] | | mid | 5 | 0 | IESG | [RFCXXXX] | | target-prefix | 6 | 4 | IESG | [RFCXXXX] | | target-port-range | 7 | 4 | IESG | [RFCXXXX] | | lower-port | 8 | 0 | IESG | [RFCXXXX] | | upper-port | 9 | 0 | IESG | [RFCXXXX] | | target-protocol | 10 | 4 | IESG | [RFCXXXX] | | target-fqdn | 11 | 4 | IESG | [RFCXXXX] | | target-uri | 12 | 4 | IESG | [RFCXXXX] | | alias-name | 13 | 4 | IESG | [RFCXXXX] | | lifetime | 14 | 0/1 | IESG | [RFCXXXX] | | mitigation-start | 15 | 0 | IESG | [RFCXXXX] | | status | 16 | 0 | IESG | [RFCXXXX] | | conflict-information | 17 | 5 | IESG | [RFCXXXX] | | conflict-status | 18 | 0 | IESG | [RFCXXXX] | | conflict-cause | 19 | 0 | IESG | [RFCXXXX] | | retry-timer | 20 | 0 | IESG | [RFCXXXX] | | conflict-scope | 21 | 5 | IESG | [RFCXXXX] | | acl-list | 22 | 4 | IESG | [RFCXXXX] | | acl-name | 23 | 3 | IESG | [RFCXXXX] | | acl-type | 24 | 3 | IESG | [RFCXXXX] | | bytes-dropped | 25 | 0 | IESG | [RFCXXXX] | | bps-dropped | 26 | 0 | IESG | [RFCXXXX] | | pkts-dropped | 27 | 0 | IESG | [RFCXXXX] | | pps-dropped | 28 | 0 | IESG | [RFCXXXX] | | attack-status | 29 | 0 | IESG | [RFCXXXX] | | ietf-dots-signal- | 30 | 5 | IESG | [RFCXXXX] | | channel:signal-config| | | | | | sid | 31 | 0 | IESG | [RFCXXXX] | | mitigating-config | 32 | 5 | IESG | [RFCXXXX] | | heartbeat-interval | 33 | 5 | IESG | [RFCXXXX] | | min-value | 34 | 0 | IESG | [RFCXXXX] | | max-value | 35 | 0 | IESG | [RFCXXXX] | | current-value | 36 | 0 | IESG | [RFCXXXX] | | missing-hb-allowed | 37 | 5 | IESG | [RFCXXXX] | | max-retransmit | 38 | 5 | IESG | [RFCXXXX] | | ack-timeout | 39 | 5 | IESG | [RFCXXXX] | | ack-random-factor | 40 | 5 | IESG | [RFCXXXX] | | min-value-decimal | 41 | 6tag4 | IESG | [RFCXXXX] | | max-value-decimal | 42string</td> <td>String</td> </tr> <tr> <td><t>ietf-dots-signal-<br/>channel:heartbeat</t></td> <td>container</td> <td>49</td> <td>5 map</td> <td>Object</td> </tr> <tr> <td>probing-rate</td> <td>container</td> <td>50</td> <td>5 map</td> <td>Object</td> </tr> <tr> <td rowspan="2">peer-hb-status</td> <td rowspan="2">boolean</td> <td rowspan="2">51</td> <td>7 bits 20</td> <td>False</td> </tr> <tr> <td>7 bits 21</td> <td>True</td> </tr> </tbody> </table> </section> <section anchor="profile" numbered="true" toc="default"> <name>(D)TLS Protocol Profile and Performance Considerations</name> <section numbered="true" toc="default"> <name>(D)TLS Protocol Profile</name> <t>This section defines the (D)TLS protocol profile of DOTS signal channel over (D)TLS and DOTS data channel over TLS.</t> <t>There are known attacks on (D)TLS, such as man-in-the-middle and protocol downgrade attacks. These are general attacks on (D)TLS and, as such, they are not specific to DOTS over (D)TLS; refer to the (D)TLS RFCs for discussion of these security issues. DOTS agents <bcp14>MUST</bcp14> adhere to the (D)TLS implementation recommendations and security considerations of <xref target="RFC7525" format="default"/> except with respect to (D)TLS version. Because DOTS signal channel encryption relying upon (D)TLS is virtually a greenfield deployment, DOTS agents <bcp14>MUST</bcp14> implement only (D)TLS 1.2 or later.</t> <t>When a DOTS client is configured with a domain name of the DOTS server, and it connects to its configured DOTS server, the server may present it with a PKIX certificate. In order to ensure proper authentication, a DOTS client <bcp14>MUST</bcp14> verify the entire certification path per <xref target="RFC5280" format="default"/>. Additionally, the DOTS client <bcp14>MUST</bcp14> use <xref target="RFC6125" format="default"/> validation techniques to compare the domain name with the certificate provided. Certification authorities that issue DOTS server certificates <bcp14>SHOULD</bcp14> support the DNS-ID and SRV-ID identifier types. DOTS servers <bcp14>SHOULD</bcp14> prefer the use of DNS-ID and SRV-ID over CN-ID identifier types in certificate requests (as described in <xref target="RFC6125" section="2.3" sectionFormat="of" format="default"/>), and the wildcard character '*' <bcp14>SHOULD NOT</bcp14> be included in the presented identifier. DOTS doesn't use URI-IDs for server identity verification.</t> <t>A key challenge to deploying DOTS is the provisioning of DOTS clients, including the distribution of keying material to DOTS clients to enable the required mutual authentication of DOTS agents. Enrollment over Secure Transport (EST) <xref target="RFC7030" format="default"/> defines a method of certificate enrollment by which domains operating DOTS servers may provide DOTS clients with all the necessary cryptographic keying material, including a private key and a certificate, to authenticate themselves. One deployment option is to have DOTS clients behave as EST clients for certificate enrollment from an EST server provisioned by the mitigation provider. This document does not specify which EST or other mechanism the DOTS client uses to achieve initial enrollment.</t> <t>The Server Name Indication (SNI) extension <xref target="RFC6066" format="default"/> i defines a mechanism for a client to tell a (D)TLS server the name of the server it wants to contact. This is a useful extension for hosting environments where multiple virtual servers are reachable over a single IP address. The DOTS client may or may not know if it is interacting with a DOTS server in a virtual server hosting environment, so the DOTS client <bcp14>SHOULD</bcp14> include the DOTS server FQDN in the SNI extension.</t> <t>Implementations compliant with this profile <bcp14>MUST</bcp14> implement all of the following items:</t> <ul spacing="normal"> <li>DTLS record replay detection (<xref target="RFC6347" section="3.3" sectionFormat="of" format="default"/>) or an equivalent mechanism to protect against replay attacks.</li> <li>DTLS session resumption without server-side state to resume session and convey the DOTS signal.</li> <li>At least one of raw public keys <xref target="RFC7250" format="default"/> or PSK handshake <xref target="RFC4279" format="default"/> with (EC)DHE key exchange. This reduces the size of the ServerHello. Also, this can be used by DOTS agents that cannot obtain certificates.</li> </ul> <t>Implementations compliant with this profile <bcp14>SHOULD</bcp14> implement all of the following items to reduce the delay required to deliver a DOTS signal channel message:</t> <ul spacing="normal"> <li>TLS False Start <xref target="RFC7918" format="default"/>, which reduces round-trips by allowing the TLS client's second flight of messages (ChangeCipherSpec) to also contain the DOTS signal. TLS False Start is formally defined for use with TLS, but the same technique is applicable to DTLS as well.</li> <li>Cached Information Extension <xref target="RFC7924" format="default"/> which avoids transmitting the server's certificate and certificate chain if the client has cached that information from a previous TLS handshake.</li> </ul> <t>Compared to UDP, DOTS signal channel over TCP requires an additional round-trip time (RTT) of latency to establish a TCP connection. DOTS implementations are encouraged to implement TCP Fast Open <xref target="RFC7413" format="default"/> to eliminate that RTT.</t> </section> <section anchor="DTLS" numbered="true" toc="default"> <name>(D)TLS 1.3 Considerations</name> <t>TLS 1.3 provides critical latency improvements for connection establishment over TLS 1.2. The DTLS 1.3 protocol <xref target="I-D.ietf-tls-dtls13" format="default"/> is based upon the TLS 1.3 protocol and provides equivalent security guarantees. (D)TLS 1.3 provides two basic handshake modes the DOTS signal channel can take advantage of:</t> <ul spacing="normal"> <li> A full handshake mode in which a DOTS client can send a DOTS mitigation request message after one round trip and the DOTS server immediately responds with a DOTS mitigation response. This assumes no packet loss is experienced. </li> <li> 0-RTT mode in which the DOTS client can authenticate itself and send DOTS mitigation request messages in the first message, thus reducing handshake latency. 0-RTT only works if the DOTS client has previously communicated with that DOTS server, which is very likely with the DOTS signal channel. </li> </ul> <t>The DOTS client has to establish a (D)TLS session with the DOTS server during 'idle' time and share a PSK. </t> <t>During a DDoS attack, the DOTS client can use the (D)TLS session to convey the DOTS mitigation request message and, if there is no response from the server after multiple retries, the DOTS client can resume the (D)TLS session in 0-RTT mode using PSK. </t> <t>DOTS servers that support (D)TLS 1.3 <bcp14>MAY</bcp14> allow DOTS clients to send early data (0-RTT). DOTS clients <bcp14>MUST NOT</bcp14> send "CoAP Ping" as early data; such messages <bcp14>MUST</bcp14> be rejected by DOTS servers. <xref target="RFC8446" section="8" sectionFormat="of" format="default"/> discusses some mechanisms to implement in order to limit the impact of replay attacks on 0-RTT data. If the DOTS server accepts 0-RTT, it <bcp14>MUST</bcp14> implement one of these mechanisms to prevent replay at the TLS layer. A DOTS server can reject 0-RTT by sending a TLS HelloRetryRequest. </t> <t>The DOTS signal channel messages sent as early data by the DOTS client are idempotent requests. As a reminder, the Message ID (<xref target="RFC7252" section="3" sectionFormat="of" format="default"/>) is changed each time a new CoAP request is sent, and the Token (<xref target="RFC7252" section="5.3.1" sectionFormat="of" format="default"/>) is randomized in each CoAP request. The DOTS server(s) <bcp14>MUST</bcp14> use the Message ID and the Token in the DOTS signal channel message to detect replay of early data at the application layer and accept 0-RTT data at most once from the same DOTS client. This anti-replay defense requires sharing the Message ID and the Token in the 0-RTT data between DOTS servers in the DOTS server domain. DOTS servers do not rely on transport coordinates to identify DOTS peers. As specified in <xref target="post" format="default"/>, DOTS servers couple the DOTS signal channel sessions using the DOTS client identity and optionally the 'cdid' parameter value. Furthermore, the 'mid' value is monotonically increased by the DOTS client for each mitigation request, thus attackers that replay mitigation requests with lower numeric 'mid' values and overlapping scopes with mitigation requests having higher numeric 'mid' values will be rejected systematically by the DOTS server. Likewise, the 'sid' value is monotonically increased by the DOTS client for each configuration request (<xref target="convey" format="default"/>); attackers replaying configuration requests with lower numeric 'sid' values will be rejected by the DOTS server if it maintains a higher numeric 'sid' value for this DOTS client. </t> <t>Owing to the aforementioned protections, all DOTS signal channel requests are safe to transmit in TLS 1.3 as early data. Refer to <xref target="I-D.boucadair-dots-earlydata" format="default"/> for more details. </t> <t>A simplified TLS 1.3 handshake with 0-RTT DOTS mitigation request message exchange is shown in <xref target="Figure24" format="default"/>.</t> <figure anchor="Figure24"> <name>A Simplified TLS 1.3 Handshake with 0-RTT</name> <artwork align="left" name="" type="" alt=""><![CDATA[ DOTS Client DOTS Server ClientHello (0-RTT DOTS signal message) --------> ServerHello {EncryptedExtensions} {Finished} <-------- [DOTS signal message] (end_of_early_data) {Finished} --------> [DOTS signal message] <-------> [DOTS signal message] Note that: () Indicates messages protected 0-RTT keys {} Indicates messages protected using handshake keys [] Indicates messages protected using 1-RTT keys ]]></artwork> </figure> </section> <section anchor="mtu" numbered="true" toc="default"> <name>DTLS MTU and Fragmentation</name> <t>To avoid DOTS signal message fragmentation and the subsequent decreased probability of message delivery, DOTS agents <bcp14>MUST</bcp14> ensure that the DTLS record fits within a single datagram. As a reminder, DTLS handles fragmentation and reassembly only for handshake messages and not for the application data (<xref target="RFC6347" section="4.1.1" sectionFormat="of" format="default"/>). If the path MTU (PMTU) cannot be discovered, DOTS agents <bcp14>MUST</bcp14> assume a PMTU of 1280 bytes, as IPv6 requires that every link in the Internet have an MTU of 1280 octets or greater as specified in <xref target="RFC8200" format="default"/>. If IPv4 support on legacy or otherwise unusual networks is a consideration and the PMTU is unknown, DOTS implementations <bcp14>MAY</bcp14> assume a PMTU of 576 bytes for IPv4 datagrams, as every IPv4 host must be capable of receiving a packet whose length is equal to 576 bytes as discussed in <xref target="RFC0791" format="default"/> and <xref target="RFC1122" format="default"/>.</t> <t>The DOTS client must consider the amount of record expansion expected by the DTLS processing when calculating the size of the CoAP message that fits within the PMTU. PMTU <bcp14>MUST</bcp14> be greater than or equal to [CoAP message size + DTLS 1.2 overhead of 13 octets + authentication overhead of the negotiated DTLS cipher suite + block padding] (<xref target="RFC6347" section="4.1.1.1" sectionFormat="of" format="default"/>). If the total request size exceeds the PMTU, then the DOTS client <bcp14>MUST</bcp14> split the DOTS signal into separate messages; for example, the list of addresses in the 'target-prefix' parameter could be split into multiple lists and each list conveyed in a new PUT request.</t> <aside><t>Implementation Note: DOTS choice of message size parameters works well with IPv6 and with most of today's IPv4 paths. However, with IPv4, it is harder to safely make sure that there is no IP fragmentation. If the IPv4 PMTU is unknown, implementations may want to limit themselves to more conservative IPv4 datagram sizes such as 576 bytes, per <xref target="RFC0791" format="default"/>.</t></aside> </section> </section> <section anchor="mutauth" numbered="true" toc="default"> <name>Mutual Authentication of DOTS Agents & Authorization of DOTS Clients</name> <t>(D)TLS based upon client certificates can be used for mutual authentication between DOTS agents. If, for example, a DOTS gateway is involved, DOTS clients and DOTS gateways must perform mutual authentication; only authorized DOTS clients are allowed to send DOTS signals to a DOTS gateway. The DOTS gateway and the DOTS server must perform mutual authentication; a DOTS server only allows DOTS signal channel messages from an authorized DOTS gateway, thereby creating a two-link chain of transitive authentication between the DOTS client and the DOTS server.</t> <t>The DOTS server should support certificate-based client authentication. The DOTS client should respond to the DOTS server's TLS CertificateRequest message with the PKIX certificate held by the DOTS client. DOTS client certificate validation must be performed per <xref target="RFC5280" format="default"/>, and the DOTS client certificate must conform to the <xref target="RFC5280" format="default"/> certificate profile. If a DOTS client does not support TLS client certificate authentication, it must support client authentication based on pre-shared key or raw public key.</t> <figure anchor="Figure12"> <name>Example of Authentication and Authorization of DOTS Agents</name> <artwork align="center" name="" type="" alt=""><![CDATA[ +---------------------------------------------+ |6tag4example.com domain +---------+ |IESG|[RFCXXXX]| AAA |current-value-|43|6tag4+---------------+ |IESGServer |[RFCXXXX]| |decimal| Application | +------+--+ | | | server +<---------------+ ^ |idle-config|44|5(DOTS client) |IESG|[RFCXXXX]| |trigger-mitigation|45+---------------+ |7|IESG|[RFCXXXX]| V V |ietf-dots-signal-chan| 46example.net domain |5+-----+----+--+ |IESG+---------------+ |[RFCXXXX]+--------------+ | |nel:redirected-signal|| | | | |alt-serverGuest +<----x---->+ DOTS +<----->+ DOTS |47|3|IESG(DOTS client)| |[RFCXXXX]gateway | |alt-server-record|48server |4|IESG+--------------+ |[RFCXXXX]| |ietf-dots-signal-chan| 49|5|IESG|[RFCXXXX]+----+--------+ | +---------------+ |nel:heartbeat^ | | | | | +----------------+ |probing-rate|50|5|IESGDDoS detector |[RFCXXXX]| |peer-hb-status|51|7(DOTS client) +<-------------+ |IESG|[RFCXXXX]+----------------+ |+----------------------+-------+-------+------------+---------------+ Table 6: Initial+---------------------------------------------+ ]]></artwork> </figure> <t>In the example depicted in <xref target="Figure12" format="default"/>, the DOTS gateway and DOTS clients within the 'example.com' domain mutually authenticate. After the DOTS gateway validates the identity of a DOTS client, it communicates with the AAA server in the 'example.com' domain to determine if the DOTS client is authorized to request DDoS mitigation. If the DOTS client is not authorized, a 4.01 (Unauthorized) is returned in the response to the DOTS client. In this example, the DOTS gateway only allows the application server and DDoS attack detector to request DDoS mitigation, but does not permit the user of type 'guest' to request DDoS mitigation.</t> <t>Also, DOTS gateways and servers located in different domains must perform mutual authentication (e.g., using certificates). A DOTS server will only allow a DOTS gateway with a certificate for a particular domain to request mitigation for that domain. In reference to <xref target="Figure12" format="default"/>, the DOTS server only allows the DOTS gateway to request mitigation for the 'example.com' domain and not for other domains.</t> </section> <section anchor="IANA" numbered="true" toc="default"> <name>IANA Considerations</name> <section anchor="port" numbered="true" toc="default"> <name>DOTS Signal Channel UDP and TCP Port Number</name> <t>IANA has assigned the port number 4646 (the ASCII decimal value for ".." (DOTS)) to the DOTS signal channel protocol for both UDP and TCP from the "Service Name and Transport Protocol Port Number Registry" available at <eref target="https://www.iana.org/assignments/service-names-port-numbers/" brackets="angle"/>.</t> <ul empty="true" spacing="normal"> <li> <dl newline="false" spacing="compact"> <dt>Service Name:</dt><dd>dots-signal</dd> <dt>Port Number:</dt><dd>4646</dd> <dt>Transport Protocol:</dt><dd>TCP</dd> <dt>Description:</dt><dd>Distributed Denial-of-Service Open Threat Signaling (DOTS) Signal Channel</dd> <dt>Assignee:</dt><dd>IESG</dd> <dt>Contact:</dt><dd>IETF Chair</dd> <dt>Registration Date:</dt><dd>2020-01-16</dd> <dt>Reference:</dt><dd>[RFC8782]</dd> </dl> </li> <li> <dl newline="false" spacing="compact"> <dt>Service Name:</dt><dd>dots-signal</dd> <dt>Port Number:</dt><dd>4646</dd> <dt>Transport Protocol:</dt><dd>UDP</dd> <dt>Description:</dt><dd>Distributed Denial-of-Service Open Threat Signaling (DOTS) Signal Channel</dd> <dt>Assignee:</dt><dd>IESG</dd> <dt>Contact:</dt><dd>IETF Chair</dd> <dt>Registration Date:</dt><dd>2020-01-16</dd> <dt>Reference:</dt><dd>[RFC8782]</dd> </dl> </li> </ul> </section> <section anchor="uri" numbered="true" toc="default"> <name>Well-Known 'dots' URI</name> <t>IANA has registered the 'dots' well-known URI (<xref target="tab-dots-uri" format="default"/>) in the Well-Known URIs registry (<eref target="https://www.iana.org/assignments/well-known-uris/well-known-uris.xhtml" brackets="angle"/>) as defined by <xref target="RFC8615" format="default"/>:</t> <table anchor="tab-dots-uri"> <name>'dots' Well-Known URI</name> <thead> <tr> <th>URI Suffix</th> <th>Change Controller</th> <th>Reference</th> <th>Status</th> <th>Related information</th> </tr> </thead> <tbody> <tr> <td>dots</td> <td>IETF</td> <td>[RFC8782]</td> <td>permanent</td> <td>None</td> </tr> </tbody> </table> </section> <section anchor="MediaReg" numbered="true" toc="default"> <name>Media Type Registration</name> <t>IANA has registered the "application/dots+cbor" media type in the "Media Types" registry <xref target="IANA-MediaTypes" format="default"/> in the manner described in <xref target="RFC6838" format="default"/>, which can be used to indicate that the content is a DOTS signal channel object: </t> <t>Type name: application</t> <t>Subtype name: dots+cbor</t> <t>Required parameters: N/A</t> <t>Optional parameters: N/A</t> <t>Encoding considerations: binary</t> <t>Security considerations: See the Security Considerations section of [RFC8782]</t> <t>Interoperability considerations: N/A</t> <t>Published specification: [RFC8782]</t> <t>Applications that use this media type: DOTS agents sending DOTS messages over CoAP over (D)TLS.</t> <t>Fragment identifier considerations: N/A</t> <t>Additional information:</t> <ul empty="true" spacing="compact"> <li>Deprecated alias names for this type: N/A</li> <li>Magic number(s): N/A</li> <li>File extension(s): N/A</li> <li>Macintosh file type code(s): N/A</li> </ul> <t>Person & email address to contact for further information: IESG, iesg@ietf.org</t> <t>Intended usage: COMMON</t> <t>Restrictions on usage: none</t> <t>Author: See Authors' Addresses section.</t> <t>Change controller: IESG</t> <t>Provisional registration? No</t> </section> <section anchor="IANACoAPContentFormatRegistration" numbered="true" toc="default"> <name>CoAP Content-Formats Registration</name> <t>IANA has registered the CoAP Content-Format ID for the "application/dots+cbor" media type in the "CoAP Content-Formats" registry <xref target="IANA-CoAP-Content-Formats" format="default"/>:</t> <ul spacing="compact"> <li>Media Type: application/dots+cbor</li> <li>Encoding: -</li> <li>ID: 271</li> <li>Reference: [RFC8782]</li> </ul> </section> <section anchor="IANACBORTagAssignment" numbered="true" toc="default"> <name>CBOR Tag Registration</name> <t>This section defines the DOTS CBOR tag as another means for applications to declare that a CBOR data structure is a DOTS signal channel object. Its use is optional and is intended for use in cases in which this information would not otherwise be known. The DOTS CBOR tag is not required for DOTS signal channel protocol version specified in this document. If present, the DOTS tag <bcp14>MUST</bcp14> prefix a DOTS signal channel object.</t> <t>IANA has registered the DOTS signal channel CBOR tag in the "CBOR Tags" registry <xref target="IANA-CBOR-Tags" format="default"/>:</t> <ul spacing="compact"> <li>Tag: 271</li> <li>Data Item: DDoS Open Threat Signaling (DOTS) signal channel object</li> <li>Semantics: DDoS Open Threat Signaling (DOTS) signal channel object, as defined in [RFC8782]</li> <li>Reference: [RFC8782]</li> </ul> </section> <section anchor="reg" numbered="true" toc="default"> <name>DOTS Signal Channel Protocol Registry</name> <t>IANA has created a new registry titled the "Distributed Denial-of-Service Open Threat Signaling (DOTS) Signal Channel" registry. The following sections define subregistries.</t> <section anchor="map" numbered="true" toc="default"> <name>DOTS Signal Channel CBOR Key Values Subregistry</name> <t>IANA has created a new subregistry titled "DOTS Signal Channel CBOR Key Values".</t> <t>The structure of this subregistry is provided in <xref target="format" format="default"/>. <xref target="initial" format="default"/> provides the registry as initially populated with the values in <xref target="tab-cbor-key-reg" format="default"/>.</t> <section anchor="format" numbered="true" toc="default"> <name>Registration Template</name> <dl newline="true" spacing="normal"> <dt>Parameter name:</dt> <dd>Parameter name as used in the DOTS signal channel.</dd> <dt>CBOR Key Value:</dt> <dd> <t>Key value for the parameter. The key value <bcp14>MUST</bcp14> be an integer in the 1-65535 range. The key values of the comprehension-required range (0x0001 - 0x3FFF) and of the comprehension-optional range (0x8000 - 0xBFFF) are assigned by IETF Review (<xref target="RFC8126" section="4.8" sectionFormat="of" format="default"/>). The key values of the comprehension-optional range (0x4000 - 0x7FFF) are assigned by Specification Required (<xref target="RFC8126" section="4.6" sectionFormat="of" format="default"/>) and of the comprehension-optional range (0xC000 - 0xFFFF) are reserved for Private Use (<xref target="RFC8126" section="4.1" sectionFormat="of" format="default"/>).</t> <t>Registration requests for the 0x4000 - 0x7FFF range are evaluated after a three-week review period on the dots-signal-reg-review@ietf.org mailing list, on the advice of one or more Designated Experts. However, to allow for the allocation of values prior to publication, the Designated Experts may approve registration once they are satisfied that such a specification will be published. New registration requests should be sent in the form of an email to the review mailing list; the request should use an appropriate subject (e.g., "Request to register CBOR Key Value for DOTS: example"). IANA will only accept new registrations from the Designated Experts, and it will check that review was requested on the mailing list in accordance with these procedures.</t> <t>Within the review period, the Designated Experts will either approve or deny the registration request, communicating this decision to the review list and IANA. Denials should include an explanation and, if applicable, suggestions as to how to make the request successful. Registration requests that are undetermined for a period longer than 21 days can be brought to the IESG's attention (using the iesg@ietf.org mailing list) for resolution.</t> <t>Criteria that should be applied by the Designated Experts include determining whether the proposed registration duplicates existing functionality, whether it is likely to be of general applicability or whether it is useful only for a single use case, and whether the registration description is clear. IANA must only accept registry updates to the 0x4000 - 0x7FFF range from the Designated Experts and should direct all requests for registration to the review mailing list. It is suggested that multiple Designated Experts be appointed. In cases where a registration decision could be perceived as creating a conflict of interest for a particular Expert, that Expert should defer to the judgment of the other Experts.</t> </dd> <dt>CBOR Major Type:</dt> <dd>CBOR Major type and optional tag for the parameter.</dd> <dt>Change Controller:</dt> <dd>For Standards Track RFCs, list the "IESG". For others, give the name of the responsible party. Other details (e.g., email address) may also be included.</dd> <dt>Specification Document(s):</dt> <dd>Reference to the document or documents that specify the parameter, preferably including URIs that can be used to retrieve copies of the documents. An indication of the relevant sections may also be included but is not required.</dd> </dl> </section> <section anchor="initial" numbered="true" toc="default"> <name>Initial Subregistry Content</name> <table anchor="tab-cbor-key-reg"> <name>Initial DOTS Signal Channel CBOR Key ValuesRegistry ]]></artwork> </figure></t>Registry</name> <thead> <tr> <th>Parameter Name</th> <th>CBOR Key Value</th> <th>CBOR Major Type</th> <th>Change Controller</th> <th>Specification Document(s)</th> </tr> </thead> <tbody> <tr> <td>Reserved</td> <td>0</td> <td/> <td/> <td>[RFC8782]</td> </tr> <tr> <td><t>ietf-dots-signal-<br/>channel:mitigation-<br/>scope</t></td> <td>1</td> <td>5</td> <td>IESG</td> <td>[RFC8782]</td> </tr> <tr> <td>scope</td> <td>2</td> <td>4</td> <td>IESG</td> <td>[RFC8782]</td> </tr> <tr> <td>cdid</td> <td>3</td> <td>3</td> <td>IESG</td> <td>[RFC8782]</td> </tr> <tr> <td>cuid</td> <td>4</td> <td>3</td> <td>IESG</td> <td>[RFC8782]</td> </tr> <tr> <td>mid</td> <td>5</td> <td>0</td> <td>IESG</td> <td>[RFC8782]</td> </tr> <tr> <td>target-prefix</td> <td>6</td> <td>4</td> <td>IESG</td> <td>[RFC8782]</td> </tr> <tr> <td>target-port-range</td> <td>7</td> <td>4</td> <td>IESG</td> <td>[RFC8782]</td> </tr> <tr> <td>lower-port</td> <td>8</td> <td>0</td> <td>IESG</td> <td>[RFC8782]</td> </tr> <tr> <td>upper-port</td> <td>9</td> <td>0</td> <td>IESG</td> <td>[RFC8782]</td> </tr> <tr> <td>target-protocol</td> <td>10</td> <td>4</td> <td>IESG</td> <td>[RFC8782]</td> </tr> <tr> <td>target-fqdn</td> <td>11</td> <td>4</td> <td>IESG</td> <td>[RFC8782]</td> </tr> <tr> <td>target-uri</td> <td>12</td> <td>4</td> <td>IESG</td> <td>[RFC8782]</td> </tr> <tr> <td>alias-name</td> <td>13</td> <td>4</td> <td>IESG</td> <td>[RFC8782]</td> </tr> <tr> <td>lifetime</td> <td>14</td> <td>0/1</td> <td>IESG</td> <td>[RFC8782]</td> </tr> <tr> <td>mitigation-start</td> <td>15</td> <td>0</td> <td>IESG</td> <td>[RFC8782]</td> </tr> <tr> <td>status</td> <td>16</td> <td>0</td> <td>IESG</td> <td>[RFC8782]</td> </tr> <tr> <td>conflict-information</td> <td>17</td> <td>5</td> <td>IESG</td> <td>[RFC8782]</td> </tr> <tr> <td>conflict-status</td> <td>18</td> <td>0</td> <td>IESG</td> <td>[RFC8782]</td> </tr> <tr> <td>conflict-cause</td> <td>19</td> <td>0</td> <td>IESG</td> <td>[RFC8782]</td> </tr> <tr> <td>retry-timer</td> <td>20</td> <td>0</td> <td>IESG</td> <td>[RFC8782]</td> </tr> <tr> <td>conflict-scope</td> <td>21</td> <td>5</td> <td>IESG</td> <td>[RFC8782]</td> </tr> <tr> <td>acl-list</td> <td>22</td> <td>4</td> <td>IESG</td> <td>[RFC8782]</td> </tr> <tr> <td>acl-name</td> <td>23</td> <td>3</td> <td>IESG</td> <td>[RFC8782]</td> </tr> <tr> <td>acl-type</td> <td>24</td> <td>3</td> <td>IESG</td> <td>[RFC8782]</td> </tr> <tr> <td>bytes-dropped</td> <td>25</td> <td>0</td> <td>IESG</td> <td>[RFC8782]</td> </tr> <tr> <td>bps-dropped</td> <td>26</td> <td>0</td> <td>IESG</td> <td>[RFC8782]</td> </tr> <tr> <td>pkts-dropped</td> <td>27</td> <td>0</td> <td>IESG</td> <td>[RFC8782]</td> </tr> <tr> <td>pps-dropped</td> <td>28</td> <td>0</td> <td>IESG</td> <td>[RFC8782]</td> </tr> <tr> <td>attack-status</td> <td>29</td> <td>0</td> <td>IESG</td> <td>[RFC8782]</td> </tr> <tr> <td><t>ietf-dots-signal-<br/>channel:signal-<br/>config</t></td> <td>30</td> <td>5</td> <td>IESG</td> <td>[RFC8782]</td> </tr> <tr> <td>sid</td> <td>31</td> <td>0</td> <td>IESG</td> <td>[RFC8782]</td> </tr> <tr> <td>mitigating-config</td> <td>32</td> <td>5</td> <td>IESG</td> <td>[RFC8782]</td> </tr> <tr> <td>heartbeat-interval</td> <td>33</td> <td>5</td> <td>IESG</td> <td>[RFC8782]</td> </tr> <tr> <td>min-value</td> <td>34</td> <td>0</td> <td>IESG</td> <td>[RFC8782]</td> </tr> <tr> <td>max-value</td> <td>35</td> <td>0</td> <td>IESG</td> <td>[RFC8782]</td> </tr> <tr> <td>current-value</td> <td>36</td> <td>0</td> <td>IESG</td> <td>[RFC8782]</td> </tr> <tr> <td>missing-hb-allowed</td> <td>37</td> <td>5</td> <td>IESG</td> <td>[RFC8782]</td> </tr> <tr> <td>max-retransmit</td> <td>38</td> <td>5</td> <td>IESG</td> <td>[RFC8782]</td> </tr> <tr> <td>ack-timeout</td> <td>39</td> <td>5</td> <td>IESG</td> <td>[RFC8782]</td> </tr> <tr> <td>ack-random-factor</td> <td>40</td> <td>5</td> <td>IESG</td> <td>[RFC8782]</td> </tr> <tr> <td>min-value-decimal</td> <td>41</td> <td>6tag4</td> <td>IESG</td> <td>[RFC8782]</td> </tr> <tr> <td>max-value-decimal</td> <td>42</td> <td>6tag4</td> <td>IESG</td> <td>[RFC8782]</td> </tr> <tr> <td>current-value-decimal</td> <td>43</td> <td>6tag4</td> <td>IESG</td> <td>[RFC8782]</td> </tr> <tr> <td>idle-config</td> <td>44</td> <td>5</td> <td>IESG</td> <td>[RFC8782]</td> </tr> <tr> <td>trigger-mitigation</td> <td>45</td> <td>7</td> <td>IESG</td> <td>[RFC8782]</td> </tr> <tr> <td><t>ietf-dots-signal-<br/>channel:redirected-<br/>signal</t></td> <td>46</td> <td>5</td> <td>IESG</td> <td>[RFC8782]</td> </tr> <tr> <td>alt-server</td> <td>47</td> <td>3</td> <td>IESG</td> <td>[RFC8782]</td> </tr> <tr> <td>alt-server-record</td> <td>48</td> <td>4</td> <td>IESG</td> <td>[RFC8782]</td> </tr> <tr> <td><t>ietf-dots-signal-<br/>channel:heartbeat</t></td> <td>49</td> <td>5</td> <td>IESG</td> <td>[RFC8782]</td> </tr> <tr> <td>probing-rate</td> <td>50</td> <td>5</td> <td>IESG</td> <td>[RFC8782]</td> </tr> <tr> <td>peer-hb-status</td> <td>51</td> <td>7</td> <td>IESG</td> <td>[RFC8782]</td> </tr> <tr> <td>Unassigned</td> <td>52-49151</td> <td/> <td/> <td/> </tr> <tr> <td>Reserved for Private Use</td> <td>49152-65535</td> <td/> <td/> <td>[RFC8782]</td> </tr> </tbody> </table> </section> </section> <section anchor="sc"title="Statusnumbered="true" toc="default"> <name>Status CodesSub-Registry"> <t>The document requests IANA to createSubregistry</name> <t>IANA has created a newsub-registry, entitledsubregistry titled "DOTS Signal Channel Status Codes". Codes in this registry are used as valid values of 'status' parameter.</t> <t>The registry is initially populated with the following values:</t><texttable style="full"> <ttcol align="right">Code</ttcol> <ttcol>Label</ttcol> <ttcol align="left">Description</ttcol> <ttcol>Reference</ttcol> <c>1</c> <c>attack-mitigation-in-progress</c> <c>Attack<table align="center"> <name>Initial DOTS Signal Channel Status Codes</name> <thead> <tr> <th align="right">Code</th> <th align="left">Label</th> <th align="left">Description</th> <th align="left">Reference</th> </tr> </thead> <tbody> <tr> <td align="right"><t>0</t></td> <td align="left"><t>Reserved</t></td> <td align="left"/> <td align="left"><t>[RFC8782]</t></td> </tr> <tr> <td align="right"><t>1</t></td> <td align="left"><t>attack-mitigation-<br/>in-progress</t></td> <td align="left"><t>Attack mitigation setup is in progress (e.g., changing the network path to redirect the inbound traffic to a DOTSmitigator).</c> <c>[RFCXXXX]</c> <c>2</c> <c>attack-successfully-mitigated</c> <c>Attackmitigator).</t></td> <td align="left"><t>[RFC8782]</t></td> </tr> <tr> <td align="right"><t>2</t></td> <td align="left"><t>attack-successfully-<br/>mitigated</t></td> <td align="left"><t>Attack is being successfully mitigated (e.g., traffic is redirected to a DDoS mitigator and attack traffic isdropped).</c> <c>[RFCXXXX]</c> <c>3</c> <c>attack-stopped</c> <c>Attackdropped).</t></td> <td align="left"><t>[RFC8782]</t></td> </tr> <tr> <td align="right"><t>3</t></td> <td align="left"><t>attack-stopped</t></td> <td align="left"><t>Attack has stopped and the DOTS client can withdraw the mitigationrequest.</c> <c>[RFCXXXX]</c> <c>4</c> <c>attack-exceeded-capability</c> <c>Attackrequest.</t></td> <td align="left"><t>[RFC8782]</t></td> </tr> <tr> <td align="right"><t>4</t></td> <td align="left"><t>attack-exceeded-<br/>capability</t></td> <td align="left"><t>Attack has exceeded the mitigation providercapability.</c> <c>[RFCXXXX]</c> <c>5</c> <c>dots-client-withdrawn-mitigation</c> <c>DOTScapability.</t></td> <td align="left"><t>[RFC8782]</t></td> </tr> <tr> <td align="right"><t>5</t></td> <td align="left"><t>dots-client-<br/>withdrawn-mitigation</t></td> <td align="left"><t>DOTS client has withdrawn the mitigation request and the mitigation is active butterminating.</c> <c>[RFCXXXX]</c> <c>6</c> <c>attack-mitigation-terminated</c> <c>Attackterminating.</t></td> <td align="left"><t>[RFC8782]</t></td> </tr> <tr> <td align="right"><t>6</t></td> <td align="left"><t>attack-mitigation-<br/>terminated</t></td> <td align="left"><t>Attack mitigation is nowterminated.</c> <c>[RFCXXXX]</c> <c>7</c> <c>attack-mitigation-withdrawn</c> <c>Attack mitigation is withdrawn.</c> <c>[RFCXXXX]</c> <c>8</c> <c>attack-mitigation-signal-loss</c> <c>Attackterminated.</t></td> <td align="left"><t>[RFC8782]</t></td> </tr> <tr> <td align="right"><t>7</t></td> <td align="left"><t>attack-mitigation-<br/>withdrawn</t></td> <td align="left"><t>Attack mitigation is withdrawn.</t></td> <td align="left"><t>[RFC8782]</t></td> </tr> <tr> <td align="right"><t>8</t></td> <td align="left"><t>attack-mitigation-<br/>signal-loss</t></td> <td align="left"><t>Attack mitigation will be triggered for the mitigation request only when the DOTS signal channel session islost.</c> <c>[RFCXXXX]</c> </texttable>lost.</t></td> <td align="left"><t>[RFC8782]</t></td> </tr> <tr> <td align="right"><t>9-2147483647</t></td> <td align="left"><t>Unassigned</t></td> <td align="left"/> <td align="left"/> </tr> </tbody> </table> <t>New codes can be assigned via Standards Action <xreftarget="RFC8126"></xref>.</t>target="RFC8126" format="default"/>.</t> </section> <section anchor="cs"title="Conflictnumbered="true" toc="default"> <name>Conflict Status CodesSub-Registry"> <t>The document requests IANA to createSubregistry</name> <t>IANA has created a newsub-registry, entitledsubregistry titled "DOTS Signal Channel Conflict Status Codes". Codes in this registry are used as valid values of 'conflict-status' parameter.</t> <t>The registry is initially populated with the following values:</t><texttable> <ttcol>Code</ttcol> <ttcol>Label</ttcol> <ttcol>Description</ttcol> <ttcol>Reference</ttcol> <c>1</c> <c>request-inactive-other-active</c> <c>DOTS<table align="center"> <name>Initial DOTS Signal Channel Conflict Status Codes</name> <thead> <tr> <th align="right">Code</th> <th align="left">Label</th> <th align="left">Description</th> <th align="left">Reference</th> </tr> </thead> <tbody> <tr> <td align="right">0</td> <td align="left">Reserved</td> <td align="left"/> <td align="left">[RFC8782]</td> </tr> <tr> <td align="right">1</td> <td align="left"><t>request-inactive-<br/>other-active</t></td> <td align="left">DOTS server has detected conflicting mitigation requests from different DOTS clients. This mitigation request is currently inactive until the conflicts are resolved. Another mitigation request isactive.</c> <c>[RFCXXXX]</c> <c>2</c> <c>request-active</c> <c>DOTSactive.</td> <td align="left">[RFC8782]</td> </tr> <tr> <td align="right">2</td> <td align="left">request-active</td> <td align="left">DOTS server has detected conflicting mitigation requests from different DOTS clients. This mitigation request is currentlyactive.</c> <c>[RFCXXXX]</c> <c>3</c> <c>all-requests-inactive</c> <c>DOTSactive.</td> <td align="left">[RFC8782]</td> </tr> <tr> <td align="right">3</td> <td align="left"><t>all-requests-<br/>inactive</t></td> <td align="left">DOTS server has detected conflicting mitigation requests from different DOTS clients. All conflicting mitigation requests areinactive.</c> <c>[RFCXXXX]</c> </texttable>inactive.</td> <td align="left">[RFC8782]</td> </tr> <tr> <td align="right">4-2147483647</td> <td align="left">Unassigned</td> <td align="left"/> <td align="left"/> </tr> </tbody> </table> <t>New codes can be assigned via Standards Action <xreftarget="RFC8126"></xref>.</t>target="RFC8126" format="default"/>.</t> </section> <section anchor="cc"title="Conflictnumbered="true" toc="default"> <name>Conflict Cause CodesSub-Registry"> <t>The document requests IANA to createSubregistry</name> <t>IANA has created a newsub-registry, entitledsubregistry titled "DOTS Signal Channel Conflict Cause Codes". Codes in this registry are used as valid values of 'conflict-cause' parameter.</t> <t>The registry is initially populated with the following values:</t><texttable> <ttcol>Code</ttcol> <ttcol>Label</ttcol> <ttcol>Description</ttcol> <ttcol>Reference</ttcol> <c>1</c> <c>overlapping-targets</c> <c>Overlapping targets.</c> <c>[RFCXXXX]</c> <c>2</c> <c>conflict-with-acceptlist</c> <c>Conflicts<table align="center"> <name>Initial DOTS Signal Channel Conflict Cause Codes</name> <thead> <tr> <th align="right">Code</th> <th align="left">Label</th> <th align="left">Description</th> <th align="left">Reference</th> </tr> </thead> <tbody> <tr> <td align="right">0</td> <td align="left">Reserved</td> <td align="left"/> <td align="left">[RFC8782]</td> </tr> <tr> <td align="right">1</td> <td align="left">overlapping-targets</td> <td align="left">Overlapping targets.</td> <td align="left">[RFC8782]</td> </tr> <tr> <td align="right">2</td> <td align="left"><t>conflict-with-<br/>acceptlist</t></td> <td align="left">Conflicts with an existing accept-list. This code is returned when the DDoS mitigation detects source addresses/prefixes in the accept-listed ACLs are attacking thetarget.</c> <c>[RFCXXXX]</c> <c>3</c> <c>cuid-collision</c> <c>CUIDtarget.</td> <td align="left">[RFC8782]</td> </tr> <tr> <td align="right">3</td> <td align="left">cuid-collision</td> <td align="left">CUID Collision. This code is returned when a DOTS client uses a 'cuid' that is already used by another DOTSclient.</c> <c>[RFCXXXX]</c> </texttable>client.</td> <td align="left">[RFC8782]</td> </tr> <tr> <td align="right">4-2147483647</td> <td align="left">Unassigned</td> <td align="left"/> <td align="left"/> </tr> </tbody> </table> <t>New codes can be assigned via Standards Action <xreftarget="RFC8126"></xref>.</t>target="RFC8126" format="default"/>.</t> </section> <section anchor="as"title="Attacknumbered="true" toc="default"> <name>Attack Status CodesSub-Registry"> <t>The document requests IANA to createSubregistry</name> <t>IANA has created a newsub-registry, entitledsubregistry titled "DOTS Signal Channel Attack Status Codes". Codes in this registry are used as valid values of 'attack-status' parameter.</t> <t>The registry is initially populated with the following values:</t><texttable> <ttcol>Code</ttcol> <ttcol>Label</ttcol> <ttcol>Description</ttcol> <ttcol>Reference</ttcol> <c>1</c> <c>under-attack</c> <c>The<table align="center"> <name>Initial DOTS Signal Channel Attack Status Codes</name> <thead> <tr> <th align="right">Code</th> <th align="left">Label</th> <th align="left">Description</th> <th align="left">Reference</th> </tr> </thead> <tbody> <tr> <td align="right">0</td> <td align="left">Reserved</td> <td align="left"/> <td align="left">[RFC8782]</td> </tr> <tr> <td align="right">1</td> <td align="left">under-attack</td> <td align="left">The DOTS client determines that it is still underattack.</c> <c>[RFCXXXX]</c> <c>2</c> <c>attack-successfully-mitigated</c> <c>Theattack.</td> <td align="left">[RFC8782]</td> </tr> <tr> <td align="right">2</td> <td align="left"><t>attack-successfully-<br/>mitigated</t></td> <td align="left">The DOTS client determines that the attack is successfullymitigated.</c> <c>[RFCXXXX]</c> </texttable>mitigated.</td> <td align="left">[RFC8782]</td> </tr> <tr> <td align="right">3-2147483647</td> <td align="left">Unassigned</td> <td align="left"/> <td align="left"/> </tr> </tbody> </table> <t>New codes can be assigned via Standards Action <xreftarget="RFC8126"></xref>.</t>target="RFC8126" format="default"/>.</t> </section> </section> <section anchor="yang"title="DOTSnumbered="true" toc="default"> <name>DOTS Signal Channel YANGModules"> <t>This document requests IANA to registerModules</name> <t>IANA has registered the following URIs in the "ns" subregistry within the "IETF XML Registry" <xreftarget="RFC3688"></xref>: <figure> <artwork><![CDATA[ URI: urn:ietf:params:xml:ns:yang:ietf-dots-signal-channel Registrant Contact: The IESG. XML: N/A;target="RFC3688" format="default"/>: </t> <ul empty="true" spacing="normal"> <li> <dl newline="false" spacing="compact"> <dt>URI:</dt><dd>urn:ietf:params:xml:ns:yang:ietf-dots-signal-channel</dd> <dt>Registrant Contact:</dt><dd>The IESG.</dd> <dt>XML:</dt><dd>N/A; the requested URI is an XMLnamespace. URI: urn:ietf:params:xml:ns:yang:iana-dots-signal-channel Registrant Contact: IANA. XML: N/A;namespace.</dd> </dl> </li> <li> <dl newline="false" spacing="compact"> <dt>URI:</dt> <dd>urn:ietf:params:xml:ns:yang:iana-dots-signal-channel</dd> <dt>Registrant Contact:</dt> <dd>IANA.</dd> <dt>XML:</dt> <dd>N/A; the requested URI is an XMLnamespace. ]]></artwork> </figure>This document requests IANA to registernamespace.</dd> </dl> </li> </ul> <t>IANA has registered the following YANG modules in the "YANG Module Names" subregistry <xreftarget="RFC7950"></xref>target="RFC7950" format="default"/> within the "YANG Parameters"registry.<figure> <artwork><![CDATA[ Name: ietf-dots-signal-channel Namespace: urn:ietf:params:xml:ns:yang:ietf-dots-signal-channel Maintained by IANA: N Prefix: signal Reference: RFC XXXX Name: iana-dots-signal-channel Namespace: urn:ietf:params:xml:ns:yang:iana-dots-signal-channel Maintained by IANA: Y Prefix: iana-signal Reference: RFC XXXX ]]></artwork> </figure></t>registry.</t> <ul empty="true" spacing="normal"> <li> <dl newline="false" spacing="compact"> <dt>Name:</dt> <dd>ietf-dots-signal-channel</dd> <dt>Maintained by IANA:</dt> <dd>N</dd> <dt>Namespace:</dt> <dd>urn:ietf:params:xml:ns:yang:ietf-dots-signal-channel</dd> <dt>Prefix:</dt> <dd>signal</dd> <dt>Reference:</dt> <dd>RFC8782</dd> </dl> </li> <li> <dl newline="false" spacing="compact"> <dt>Name:</dt> <dd>iana-dots-signal-channel</dd> <dt>Maintained by IANA:</dt> <dd>Y</dd> <dt>Namespace:</dt> <dd>urn:ietf:params:xml:ns:yang:iana-dots-signal-channel</dd> <dt>Prefix:</dt> <dd>iana-signal</dd> <dt>Reference:</dt> <dd>RFC8782</dd> </dl> </li> </ul> <t>This document defines the initial version of the IANA-maintained iana-dots-signal-channel YANG module. IANAis requested to addhas added thisnote:<list style="empty"> <t>Status,note:</t> <ul empty="true" spacing="normal"> <li>Status, conflict status, conflict cause, and attack status values must not be directly added to the iana-dots-signal-channel YANG module. They must instead be respectively added to the "DOTS Status Codes", "DOTS Conflict Status Codes", "DOTS Conflict Cause Codes", and "DOTS Attack Status Codes"registries.</t> </list></t>registries.</li> </ul> <t>When a 'status', 'conflict-status', 'conflict-cause', or 'attack-status' value is respectively added to the "DOTS Status Codes", "DOTS Conflict Status Codes", "DOTS Conflict Cause Codes", or "DOTS Attack Status Codes" registry, a new "enum" statement must be added to the iana-dots-signal-channel YANG module. The following "enum" statement, and substatements thereof, should bedefined:<list hangIndent="15" style="hanging"> <t hangText=""enum":">Replicatesdefined:</t> <dl newline="false" spacing="normal" indent="15"> <dt>"enum":</dt> <dd>Replicates the label from theregistry.</t> <t hangText=""value":">Containsregistry.</dd> <dt>"value":</dt> <dd>Contains the IANA-assigned value corresponding to the 'status', 'conflict-status', 'conflict-cause', or'attack-status'.</t> <t hangText=""description":">Replicates'attack-status'.</dd> <dt>"description":</dt> <dd>Replicates the description from theregistry.</t> <t hangText=""reference":">Replicatesregistry.</dd> <dt>"reference":</dt> <dd>Replicates the reference from the registry and adds the title of thedocument.</t> </list></t>document.</dd> </dl> <t>When the iana-dots-signal-channel YANG module is updated, a new "revision" statement must be added in front of the existing revision statements.</t> <t>IANAis requested to addadded this note to "DOTS Status Codes", "DOTS Conflict Status Codes", "DOTS Conflict Cause Codes", and "DOTS Attack Status Codes" registries:</t><t><list style="empty"> <t>When<ul empty="true" spacing="normal"> <li>When this registry is modified, the YANG module iana-dots-signal-channel must be updated as defined in[RFCXXXX].</t> </list></t>[RFC8782].</li> </ul> </section> </section> <section anchor="security"title="Security Considerations">numbered="true" toc="default"> <name>Security Considerations</name> <t>High-level DOTS security considerations are documented in <xreftarget="RFC8612"></xref>target="RFC8612" format="default"/> and <xreftarget="I-D.ietf-dots-architecture"></xref>.</t>target="I-D.ietf-dots-architecture" format="default"/>.</t> <t>Authenticated encryptionMUST<bcp14>MUST</bcp14> be used for data confidentiality and message integrity. The interaction between the DOTS agents requires Datagram Transport Layer Security (DTLS) or Transport Layer Security (TLS) with a cipher suite offering confidentiality protection, and the guidance given in <xreftarget="RFC7525"></xref> MUSTtarget="RFC7525" format="default"/> <bcp14>MUST</bcp14> be followed to avoid attacks on (D)TLS. The (D)TLS protocol profile used for the DOTS signal channel is specified in <xreftarget="profile"></xref>.</t>target="profile" format="default"/>.</t> <t>If TCP is used between DOTS agents, an attacker may be able to inject RST packets, bogus application segments, etc., regardless of whether TLS authentication is used. Because the application data is TLS protected, this will not result in the application receiving bogus data, but it will constitute a DoS on the connection. This attack can be countered by usingTCP-AOTCP Authentication Option (TCP-AO) <xreftarget="RFC5925"></xref>.target="RFC5925" format="default"/>. Although not widely adopted, if TCP-AO is used, then any bogus packets injected by an attacker will be rejected by the TCP-AO integrity check and therefore will never reach the TLS layer.</t><t>An attack vector that can be achieved if<t> If the 'cuid' isguessable isguessable, a misbehaving DOTS client from within the client's domainwhich usescan use the 'cuid' of another DOTS client of the domain to delete or alter active mitigations. For this attack vector to happen, the misbehaving client needs to pass the security validation checks by the DOTS server, and eventually the checks of a client-domain DOTS gateway.</t> <t>A similar attack can be achieved by a compromised DOTS clientwhichthat can sniff the TLS 1.2 handshake, use the client certificate to identify the 'cuid' used by another DOTS client. This attack is not possible if algorithms such as version 4 Universally Unique IDentifiers (UUIDs) inSection 4.4 of<xreftarget="RFC4122"></xref>target="RFC4122" section="4.4" sectionFormat="of" format="default"/> are used to generate the 'cuid' because such UUIDs are not a deterministic function of the client certificate. Likewise, this attack is not possible with TLS 1.3 because most of the TLS handshake is encrypted and the client certificate is not visible to eavesdroppers.</t> <t>A compromised DOTS client can collude with a DDoS attacker to send mitigation request for a target resource,getsget the mitigation efficacy from the DOTS server, andconveysconvey the mitigation efficacy to the DDoS attacker to possibly change the DDoS attack strategy. Obviously, signaling an attack by the compromised DOTS client to the DOTS server will trigger attack mitigation. This attack can be prevented by monitoring and auditing DOTS clients to detect misbehavior and to deter misuse, and by only authorizing the DOTS client to request mitigation for specific target resources (e.g., an application server is authorized to request mitigation for its IPaddressesaddresses, but a DDoS mitigator can request mitigation for any target resource in the network). Furthermore, DOTS clients are typically co-located on network security services (e.g.,firewall)firewall), and a compromised security service potentially can do a lot more damage to the network.</t> <t>Rate-limiting DOTS requests, including those with new 'cuid' values, from the same DOTS clientdefendsdefend against DoS attacks that would result in varying the 'cuid' to exhaust DOTS server resources. Rate-limit policiesSHOULD<bcp14>SHOULD</bcp14> be enforced on DOTS gateways (if deployed) and DOTS servers.</t> <t>In order to prevent leaking internal information outside aclient-domain,client's domain, DOTS gateways located in theclient-domain SHOULD NOTclient domain <bcp14>SHOULD NOT</bcp14> reveal the identification information that pertains to internal DOTS clients (e.g., source IP address, client's hostname) unless explicitly configured to do so.</t> <t>DOTS serversMUST<bcp14>MUST</bcp14> verify that requesting DOTS clients are entitled to trigger actions on a given IP prefix. That is, only actions on IP resources that belong to the DOTSclient'client's domainMUST<bcp14>MUST</bcp14> be authorized by a DOTS server. The exact mechanism for the DOTS servers to validate that the target prefixes are within the scope of the DOTS client domain isdeployment-specific.</t>deployment specific.</t> <t>The presence of DOTS gateways may lead to infinite forwarding loops, which is undesirable. To prevent and detect such loops, this document uses the Hop-LimitOption.</t>option.</t> <t>When FQDNs are used as targets, the DOTS serverMUST<bcp14>MUST</bcp14> rely upon DNSprivacy enablingprivacy-enabling protocols (e.g., DNS over TLS <xreftarget="RFC7858"></xref>target="RFC7858" format="default"/> orDoHDNS over HTTPS (DoH) <xreftarget="RFC8484"></xref>)target="RFC8484" format="default"/>) to prevent eavesdroppers from possibly identifying the target resources protected by the DDoS mitigationservice, and meansservice to ensure the target FQDN resolution is authentic (e.g., DNSSEC <xreftarget="RFC4034"></xref>).</t>target="RFC4034" format="default"/>).</t> <t>CoAP-specific security considerations are discussed inSection 11 of<xreftarget="RFC7252"></xref>,target="RFC7252" section="11" sectionFormat="of" format="default"/>, while CBOR-related security considerations are discussed inSection 8 of<xreftarget="RFC7049"></xref>.</t> </section> <section anchor="contr" title="Contributors"> <t>The following individuals have contributed to this document:<list style="symbols"> <t>Jon Shallow, NCC Group, Email: jon.shallow@nccgroup.trust</t> <t>Mike Geller, Cisco Systems, Inc. 3250 Florida 33309 USA, Email: mgeller@cisco.com</t> <t>Robert Moskowitz, HTT Consulting Oak Park, MI 42837 United States, Email: rgm@htt-consult.com</t> <t>Dan Wing, Email: dwing-ietf@fuggles.com</t> </list></t> </section> <section anchor="ack" title="Acknowledgements"> <t>Thanks to Christian Jacquenet, Roland Dobbins, Roman Danyliw, Michael Richardson, Ehud Doron, Kaname Nishizuka, Dave Dolson, Liang Xia, Gilbert Clark, Xialiang Frank, Jim Schaad, Klaus Hartke, Nesredien Suleiman, Stephen Farrell, and Yoshifumi Nishida for the discussion and comments.</t> <t>The authors would like to give special thanks to Kaname Nishizuka and Jon Shallow for their efforts in implementing the protocol and performing interop testing at IETF Hackathons.</t> <t>Thanks to the core WG for the recommendations on Hop-Limit and redirect signaling.</t> <t>Special thanks to Benjamin Kaduk for the detailed AD review.</t> <t>Thanks to Alexey Melnikov, Adam Roach, Suresh Krishnan, Mirja Kühlewind, and Alissa Cooper for the review.</t> <t>Thanks to Carsten Bormann for his review of the DOTS heartbeat mechanism.</t>target="RFC7049" section="8" sectionFormat="of" format="default"/>.</t> </section> </middle> <back><references title="Normative References"> <?rfc include="reference.RFC.2119"?> <?rfc include='reference.RFC.8174'?> <?rfc include="reference.RFC.7525"?> <?rfc include="reference.RFC.6347"?> <?rfc include="reference.RFC.7252"?> <?rfc include="reference.RFC.7250"?> <?rfc include="reference.RFC.7641"?> <?rfc include="reference.RFC.8615"?> <?rfc include="reference.RFC.4279"?> <?rfc include="reference.RFC.5280"?> <?rfc include='reference.RFC.6991'?> <?rfc include='reference.RFC.5246'?> <?rfc include="reference.RFC.6125"?> <?rfc include='reference.RFC.3688'?> <?rfc include="reference.RFC.7950"?> <?rfc include='reference.RFC.8126'?> <?rfc include='reference.RFC.6066'?> <?rfc include="reference.RFC.8323"?> <?rfc include="reference.RFC.8085"?> <?rfc include="reference.RFC.7049"?> <?rfc include="reference.RFC.8446"?> <?rfc include="reference.RFC.7959"?> <?rfc include="reference.RFC.4632"?> <?rfc include="reference.RFC.7918"?> <?rfc include="reference.RFC.7924"?> <?rfc include='reference.RFC.4648'?> <?rfc include='reference.RFC.3986'?> <?rfc include='reference.RFC.8200'?> <?rfc include='reference.RFC.1122'?> <?rfc include='reference.RFC.8305'?> <?rfc include='reference.RFC.0791'?> <?rfc include='reference.I-D.ietf-core-hop-limit'?><displayreference target="I-D.ietf-dots-multihoming" to="DOTS-MH"/> <displayreference target="I-D.ietf-core-yang-cbor" to="CORE-YANG-CBOR"/> <displayreference target="I-D.ietf-core-comi" to="COMI"/> <displayreference target="I-D.ietf-dots-use-cases" to="DOTS-USE-CASES"/> <displayreference target="I-D.ietf-dots-architecture" to="DOTS-ARCH"/> <displayreference target="I-D.ietf-tls-dtls13" to="DTLS"/> <displayreference target="I-D.ietf-dots-server-discovery" to="DOTS-SERVER-DISC"/> <displayreference target="I-D.boucadair-dots-earlydata" to="DOTS-EARLYDATA"/> <references> <name>References</name> <references> <name>Normative References</name> <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.2119.xml"/> <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.8174.xml"/> <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.7525.xml"/> <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.6347.xml"/> <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.7252.xml"/> <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.7250.xml"/> <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.7641.xml"/> <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.8615.xml"/> <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.4279.xml"/> <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.5280.xml"/> <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.6991.xml"/> <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.5246.xml"/> <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.6125.xml"/> <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.3688.xml"/> <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.7950.xml"/> <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.8126.xml"/> <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.6066.xml"/> <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.8323.xml"/> <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.8085.xml"/> <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.7049.xml"/> <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.8446.xml"/> <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.7959.xml"/> <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.4632.xml"/> <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.7918.xml"/> <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.7924.xml"/> <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.4648.xml"/> <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.3986.xml"/> <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.8200.xml"/> <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.1122.xml"/> <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.8305.xml"/> <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.0791.xml"/> <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.8768.xml"/> </references><references title="Informative References"> <?rfc include="reference.RFC.4732"?> <?rfc include='reference.RFC.7951'?><references> <name>Informative References</name> <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.4732.xml"/> <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.7951.xml"/> <referenceanchor="IANA.MediaTypes"anchor="IANA-MediaTypes" target="http://www.iana.org/assignments/media-types"> <front> <title>Media Types</title> <author> <organization>IANA</organization> </author><date /></front> </reference> <referenceanchor="IANA.CoAP.Content-Formats"anchor="IANA-CoAP-Content-Formats" target="http://www.iana.org/assignments/core-parameters/core-parameters.xhtml#content-formats"> <front> <title>CoAP Content-Formats</title> <author> <organization>IANA</organization> </author><date /></front> </reference> <referenceanchor="IANA.CBOR.Tags"anchor="IANA-CBOR-Tags" target="http://www.iana.org/assignments/cbor-tags/cbor-tags.xhtml"> <front> <title>Concise Binary Object Representation (CBOR) Tags</title> <author> <organization>IANA</organization> </author> </front> </reference> <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.8499.xml"/> <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.4034.xml"/> <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.7858.xml"/> <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.8484.xml"/> <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.6234.xml"/> <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.4122.xml"/> <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.6052.xml"/> <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.7030.xml"/> <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.7452.xml"/> <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.5925.xml"/> <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.8489.xml"/> <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.4987.xml"/> <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.7413.xml"/> <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.3022.xml"/> <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.6146.xml"/> <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.6296.xml"/> <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.6724.xml"/> <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.7589.xml"/> <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.6888.xml"/> <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.4787.xml"/> <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.4340.xml"/> <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.4960.xml"/> <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.8340.xml"/> <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.6838.xml"/> <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml3/reference.I-D.ietf-dots-multihoming.xml"/> <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml3/reference.I-D.ietf-core-yang-cbor.xml"/> <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml3/reference.I-D.ietf-core-comi.xml"/> <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.8612.xml"/> <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml3/reference.I-D.ietf-dots-use-cases.xml"/> <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml3/reference.I-D.ietf-dots-architecture.xml"/> <reference anchor="RFC8783" target="https://www.rfc-editor.org/info/rfc8783"> <front> <title>Distributed Denial-of-Service Open Threat Signaling (DOTS) Data Channel Specification</title> <author initials="M" surname="Boucadair" fullname="Mohamed Boucadair" role="editor"> <organization/> </author> <author initials="T" surname="Reddy.K" fullname="Tirumaleswar Reddy.K" role="editor"> <organization/> </author> <date month="May" year="2020"/> </front> <seriesInfo name="RFC" value="8783"/> <seriesInfo name="DOI" value="10.17487/RFC8783"/> </reference> <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml3/reference.I-D.ietf-tls-dtls13.xml"/> <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml3/reference.I-D.ietf-dots-server-discovery.xml"/> <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.6887.xml"/> <reference anchor="I-D.boucadair-dots-earlydata"> <front> <title>Using Early Data in DOTS</title> <author initials="M" surname="Boucadair" fullname="Mohamed Boucadair"> <organization/> </author> <author initials="T" surname="Reddy.K" fullname="Tirumaleswar Reddy.K"> <organization/> </author> <date/>month="January" day="29" year="2019"/> </front> <seriesInfo name="Internet-Draft" value="draft-boucadair-dots-earlydata-00"/> <format type="TXT" target="http://www.ietf.org/internet-drafts/draft-boucadair-dots-earlydata-00.txt"/> </reference><?rfc include='reference.RFC.8499'?> <?rfc include='reference.RFC.4034'?> <?rfc include='reference.RFC.7858'?> <?rfc include='reference.RFC.8484'?> <?rfc include="reference.RFC.6234"?> <?rfc include='reference.RFC.4122'?> <?rfc include='reference.RFC.6052'?> <?rfc include='reference.RFC.7030'?> <?rfc include='reference.RFC.7452'?> <?rfc include="reference.RFC.5925"?> <?rfc include='reference.RFC.5389'?> <?rfc include='reference.RFC.4987'?> <?rfc include="reference.RFC.7413"?> <?rfc include='reference.RFC.3022'?> <?rfc include='reference.RFC.6146'?> <?rfc include='reference.RFC.6296'?> <?rfc include='reference.RFC.6724'?> <?rfc include="reference.RFC.7589"?> <?rfc include='reference.RFC.6888'?> <?rfc include='reference.RFC.4787'?> <?rfc include='reference.RFC.4340'?> <?rfc include='reference.RFC.4960'?> <?rfc include='reference.RFC.8340'?> <?rfc include='reference.RFC.6838'?> <?rfc include='reference.I-D.ietf-dots-multihoming'?> <?rfc include="reference.I-D.ietf-core-yang-cbor"?> <?rfc include="reference.I-D.ietf-core-comi"?> <?rfc include="reference.RFC.8612"?> <?rfc include="reference.I-D.ietf-dots-use-cases"?> <?rfc include="reference.I-D.ietf-dots-architecture"?> <?rfc include="reference.I-D.ietf-dots-data-channel" ?> <?rfc include="reference.I-D.ietf-tls-dtls13"?> <?rfc include='reference.I-D.ietf-dots-server-discovery'?> <?rfc include='reference.RFC.6887'?> <?rfc include='reference.I-D.boucadair-dots-earlydata'?><referenceanchor="proto_numbers"anchor="IANA-Proto" target="http://www.iana.org/assignments/protocol-numbers"> <front><title>IANA, "Protocol Numbers"</title><title>Protocol Numbers</title> <author><organization></organization><organization>IANA</organization> </author> <dateyear="2011" />year="2011"/> </front> </reference> </references> </references> <section anchor="motiv"title="CUID Generation">numbered="true" toc="default"> <name>CUID Generation</name> <t>The document recommends the use of SPKI to generate the 'cuid'. This design choice is motivated by the followingreasons:<list style="symbols"> <t>SPKIreasons:</t> <ul spacing="normal"> <li>SPKI is globallyunique.</t> <t>Itunique.</li> <li>It isdeterministic.</t> <t>Itdeterministic.</li> <li>It allowsto avoidthe avoidance of extra cycles that may be induced by 'cuid'collision.</t> <t>DOTScollision.</li> <li>DOTS clients do not need to store the 'cuid' in a persistentstorage.</t> <t>Itstorage.</li> <li>It allowsto detectthe detection of compromised DOTS clients that do not adhere to the 'cuid' generationalgorithm.</t> </list></t> <t></t>algorithm.</li> </ul> </section> <section anchor="ack" numbered="false" toc="default"> <name>Acknowledgements</name> <t>Thanks to <contact fullname="Christian Jacquenet"/>, <contact fullname="Roland Dobbins"/>, <contact fullname="Roman Danyliw"/>, <contact fullname="Michael Richardson"/>, <contact fullname="Ehud Doron"/>, <contact fullname="Kaname Nishizuka"/>, <contact fullname="Dave Dolson"/>, <contact fullname="Liang Xia"/>, <contact fullname="Gilbert Clark"/>, <contact fullname="Xialiang Frank"/>, <contact fullname="Jim Schaad"/>, <contact fullname="Klaus Hartke"/>, <contact fullname="Nesredien Suleiman"/>, <contact fullname="Stephen Farrell"/>, and <contact fullname="Yoshifumi Nishida"/> for the discussion and comments.</t> <t>The authors would like to give special thanks to <contact fullname="Kaname Nishizuka"/> and <contact fullname="Jon Shallow"/> for their efforts in implementing the protocol and performing interop testing at IETF Hackathons.</t> <t>Thanks to the core WG for the recommendations on Hop-Limit and redirect signaling.</t> <t>Special thanks to <contact fullname="Benjamin Kaduk"/> for the detailed AD review.</t> <t>Thanks to <contact fullname="Alexey Melnikov"/>, <contact fullname="Adam Roach"/>, <contact fullname="Suresh Krishnan"/>, <contact fullname="Mirja Kühlewind"/>, and <contact fullname="Alissa Cooper"/> for the review.</t> <t>Thanks to <contact fullname="Carsten Bormann"/> for his review of the DOTS heartbeat mechanism.</t> </section> <section anchor="contr" numbered="false" toc="default"> <name>Contributors</name> <t>The following individuals have contributed to this document:</t> <contact fullname="Jon Shallow" > <organization>NCC Group</organization> <address> <postal> <street></street> <city></city> <region></region><code></code> <country></country> </postal> <email>jon.shallow@nccgroup.trust</email> </address> </contact> <contact fullname="Mike Geller" > <organization>Cisco Systems, Inc.</organization> <address> <postal> <street></street> <city></city> <region>FL</region><code>33309</code> <country>United States of America</country> </postal> <email>mgeller@cisco.com</email> </address> </contact> <contact fullname="Robert Moskowitz" > <organization>HTT Consulting</organization> <address> <postal> <street></street> <city>Oak Park</city> <region>MI</region><code>42837</code> <country>United States of America</country> </postal> <email>rgm@htt-consult.com</email> </address> </contact> <contact fullname="Dan Wing" > <organization></organization> <address> <postal> <street></street> <city></city> <region></region><code></code> <country></country> </postal> <email>dwing-ietf@fuggles.com</email> </address> </contact> </section> </back> </rfc>