<?xml version="1.0"encoding="US-ASCII"?>encoding="UTF-8"?> <!DOCTYPE rfc [ <!ENTITYRFC2119 SYSTEM "http://xml.resource.org/public/rfc/bibxml/reference.RFC.2119.xml"> <!ENTITY RFC4271 SYSTEM "http://xml.resource.org/public/rfc/bibxml/reference.RFC.4271.xml"> <!ENTITY RFC4272 SYSTEM "http://xml.resource.org/public/rfc/bibxml/reference.RFC.4272.xml"> <!ENTITY RFC4486 SYSTEM "http://xml.resource.org/public/rfc/bibxml/reference.RFC.4486.xml"> <!ENTITY RFC5065 SYSTEM "http://xml.resource.org/public/rfc/bibxml/reference.RFC.5065.xml"> <!ENTITY RFC5492 SYSTEM "http://xml.resource.org/public/rfc/bibxml/reference.RFC.5492.xml"> <!ENTITY RFC7606 SYSTEM "http://xml.resource.org/public/rfc/bibxml/reference.RFC.7606.xml"> <!ENTITY RFC7705 SYSTEM "http://xml.resource.org/public/rfc/bibxml/reference.RFC.7705.xml"> <!ENTITY RFC7908 SYSTEM "http://xml.resource.org/public/rfc/bibxml/reference.RFC.7908.xml"> <!ENTITY RFC7938 SYSTEM "http://xml.resource.org/public/rfc/bibxml/reference.RFC.7938.xml"> <!ENTITY RFC8126 SYSTEM "http://xml.resource.org/public/rfc/bibxml/reference.RFC.8126.xml">nbsp " "> <!ENTITYRFC8174 SYSTEM "http://xml.resource.org/public/rfc/bibxml/reference.RFC.8174.xml">zwsp "​"> <!ENTITYRFC8205 SYSTEM "http://xml.resource.org/public/rfc/bibxml/reference.RFC.8205.xml">nbhy "‑"> <!ENTITYnbsp " ">wj "⁠"> ]><?xml-stylesheet type='text/xsl' href='rfc2629.xslt' ?> <?rfc strict="yes" ?> <?rfc toc="yes"?> <?rfc tocdepth="4"?> <?rfc symrefs="yes"?> <?rfc sortrefs="yes" ?> <?rfc compact="yes" ?> <?rfc subcompact="no" ?><rfc xmlns:xi="http://www.w3.org/2001/XInclude" xml:lang="en" submissionType="IETF" category="std"docName="draft-ietf-idr-bgp-open-policy-24" ipr="trust200902">consensus="true" docName="draft-ietf-idr-bgp-open-policy-23" number="9234" ipr="trust200902" tocInclude="true" tocDepth="4" symRefs="true" sortRefs="true" updates="" obsoletes="" version="3"> <front> <title abbrev="Route Leak Prevention">Route Leak Prevention and DetectionusingUsing Roles in UPDATE and OPEN Messages</title> <seriesInfo name="RFC" value="9234"/> <author fullname="Alexander Azimov" initials="A." surname="Azimov"> <organization>Qrator Labs & Yandex</organization> <address> <postal> <street>Ulitsa Lva Tolstogo 16</street> <city>Moscow</city> <code>119021</code> <country>Russian Federation</country> </postal> <email>a.e.azimov@gmail.com</email> </address> </author> <author fullname="Eugene Bogomazov" initials="E." surname="Bogomazov"> <organization>Qrator Labs</organization> <address> <postal> <street>1-y Magistralnyy tupik 5A</street> <city>Moscow</city> <code>123290</code> <country>Russian Federation</country> </postal> <email>eb@qrator.net</email> </address> </author> <author fullname="Randy Bush" initials="R." surname="Bush"><organization>Internet<organization abbrev="IIJ & Arrcus">Internet Initiative Japan & Arrcus, Inc.</organization> <address> <postal> <street>5147 Crystal Springs</street> <city>Bainbridge Island</city> <region>Washington</region> <code>98110</code> <country>United States of America</country> </postal> <email>randy@psg.com</email> </address> </author> <author fullname="Keyur Patel" initials="K." surname="Patel"> <organization>Arrcus</organization> <address> <postal> <street>2077 GatewayPlace, SuitePlace</street> <street>Suite #400</street> <city>San Jose</city> <region>CA</region> <code>95119</code> <country>United States of America</country> </postal> <email>keyur@arrcus.com</email> </address> </author> <author fullname="Kotikalapudi Sriram" initials="K." surname="Sriram"> <organization abbrev="USA NIST">USA National Institute of Standards and Technology</organization> <address> <postal> <street>100 Bureau Drive</street> <city>Gaithersburg</city> <region>MD</region> <code>20899</code> <country>United States of America</country> </postal> <email>ksriram@nist.gov</email> </address> </author><date/><date year="2022" month="April" /> <area>rtg</area> <workgroup>idr</workgroup> <keyword>BGP</keyword> <keyword>Route leak</keyword> <keyword>BGP Role</keyword> <abstract> <t> Route leaks are the propagation of BGP prefixes that violate assumptions of BGP topology relationships, e.g., announcing a route learned from one transit provider to another transit provider or a lateral (i.e., non-transit) peer or announcing a route learned from one lateral peer to another lateral peer or a transit provider. These are usually the result of misconfigured or absent BGP route filtering or lack of coordination between autonomous systems (ASes). Existing approaches to leak prevention rely on marking routes by operator configuration, with no check that the configuration corresponds to that of theeBGPExternal BGP (eBGP) neighbor, or enforcementthatof the two eBGP speakersagreeagreeing on the peering relationship. This document enhances the BGP OPEN message to establish an agreement of the peering relationship on each eBGP session between autonomous systems in order to enforce appropriate configuration on both sides. Propagated routes are then marked according to the agreed relationship, allowing both prevention and detection of route leaks. </t> </abstract><note title="Requirements Language"> <t> The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in BCP 14 <xref target="RFC2119"/> <xref target="RFC8174"/> when, and only when, they appear in all capitals, as shown here. </t> </note></front> <middle> <sectiontitle="Introduction"anchor="intro"> <name>Introduction</name> <t> Route leaks are the propagation of BGP prefixes that violate assumptions of BGP topology relationships, e.g., announcing a route learned from one transit provider to another transit provider or a lateral (i.e., non-transit) peer or announcing a route learned from one lateral peer to another lateral peer or a transit provider <xref target="RFC7908"/>. These are usually the result of misconfigured or absent BGP route filtering or lack of coordination between autonomous systems (ASes). </t> <t> Existing approaches to leak prevention rely on marking routes by operator configuration, with no check that the configuration corresponds to that of the eBGP neighbor, or enforcementthatof the two eBGP speakersagreeagreeing on the relationship. This document enhances the BGP OPEN message to establish an agreement of the relationship on each eBGP session between autonomous systems in order to enforce appropriate configuration on both sides. Propagated routes are then marked according to the agreed relationship, allowing both prevention and detection of route leaks. </t> <t> This document specifies a means of replacing the operator-driven configuration-based method of route leak prevention, described above, with an in-band method for route leak prevention and detection. </t> <t> This method uses a new configuration parameter, BGP Role, which is negotiated using a BGP Role Capability in the OPEN message <xref target="RFC5492"/>. An eBGP speaker may require the use of this capability and confirmation of the BGP Role with a neighbor for the BGP OPEN to succeed. </t> <t> An optional, transitive BGP Path Attribute, calledOnly"Only to Customer(OTC),(OTC)", is specified in <xref target="prevention_attribute"/>. It prevents ASes from creating leaks and detects leaks created by the ASes in the middle of an AS path. The main focus/applicability is the Internet (IPv4 and IPv6 unicast route advertisements). </t> </section> <section> <name>Requirements Language</name> <t> The key words "<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 "<bcp14>OPTIONAL</bcp14>" in this document are to be interpreted as described in BCP 14 <xref target="RFC2119"/> <xref target="RFC8174"/> when, and only when, they appear in all capitals, as shown here. </t> </section> <sectionanchor="terminology" title="Terminology">anchor="terminology"> <name>Terminology</name> <t> The terms "local AS" and "remote AS" are used to refer to the two ends of an eBGP session. The "local AS" is the AS where the protocol action being described is to be performed, and "remote AS" is the AS at the other end of the eBGP session in consideration. </t> <t> The use of the term "route is ineligible" in this document has the same meaning as in <xref target="RFC4271"/>, i.e., "route is ineligible to be installed in Loc-RIB and will be excluded from the next phase of route selection." </t> <sectionanchor="defs" title="Peering Relationships">anchor="defs"> <name>Peering Relationships</name> <t> The terms for peering relationships defined and used in this document (see below) do not necessarily represent business relationships based on payment agreements. These terms are used to represent restrictions on BGP route propagation, sometimes known as the Gao-Rexford model <xreftarget="Gao"/>.target="GAO-REXFORD"/>. The termsProvider, Customer,"Provider", "Customer", andPeer"Peer" used here are synonymous to the terms "transit provider", "customer", and "lateral (i.e., non-transit) peer", respectively, used in <xref target="RFC7908"/>. </t> <t> The following is a list of BGP Roles for eBGP peering and the corresponding rules for route propagation:<list style="hanging"> <t hangText="Provider:"> MAY</t> <dl newline="false" spacing="normal"> <dt>Provider:</dt> <dd> <bcp14>MAY</bcp14> propagate any available route to a Customer.</t> <t hangText="Customer:"> MAY</dd> <dt>Customer:</dt> <dd> <bcp14>MAY</bcp14> propagate any route learned from a Customer, or that is locally originated, to a Provider. All other routesMUST NOT<bcp14>MUST NOT</bcp14> be propagated.</t> <t hangText="Route</dd> <dt>Route Server(RS):"> MAY(RS):</dt> <dd> <bcp14>MAY</bcp14> propagate any available route to a Route Server Client (RS-Client).</t> <t hangText="Route</dd> <dt>Route Server Client(RS-Client):"> MAY(RS-Client):</dt> <dd> <bcp14>MAY</bcp14> propagate any route learned from a Customer, or that is locally originated, to an RS. All other routesMUST NOT<bcp14>MUST NOT</bcp14> be propagated.</t> <t hangText="Peer:"> MAY</dd> <dt>Peer:</dt> <dd> <bcp14>MAY</bcp14> propagate any route learned from a Customer, or that is locally originated, to a Peer. All other routesMUST NOT<bcp14>MUST NOT</bcp14> be propagated.</t> </list> </t></dd> </dl> <t> If the local AS has one of the above Roles (in the order shown), then the corresponding peering relationship with the remote AS is Provider-to-Customer, Customer-to-Provider, RS-to-RS-Client, RS-Client-to-RS, or Peer-to-Peer (i.e., lateral peers), respectively. These are called normal peering relationships. </t> <t> If the local AS has more than one peeringroleRole with the remoteASAS, such a peering relation is calledComplex."Complex". An example is when the peering relationship is Provider-to-Customer for some prefixes while it is Peer-to-Peer for other prefixes <xreftarget="Gao"/>.target="GAO-REXFORD"/>. </t> <t> A BGP speaker may apply policy to reduce what is announced, and a recipient may apply policy to reduce the set of routes they accept. </t> <t> Violation of the route propagation rules listed above may result in route leaks <xref target="RFC7908"/>. Automatic enforcement of these rules should significantly reduce route leaks that may otherwise occur due to manual configuration mistakes. </t> <t> As specified in <xref target="prevention_attribute"/>, theOnly to Customer (OTC)OTC Attribute is used to identify all the routes in the AS that have been received from a Peer, a Provider, or an RS. </t> </section> </section> <sectionanchor="bgp_role" title="BGP Role">anchor="bgp_role"> <name>BGP Role</name> <t> The BGP Role characterizes the relationship between the eBGP speakers forming a session. One of the Roles described belowSHOULD<bcp14>SHOULD</bcp14> be configured at the local AS for each eBGP session (see definitions in <xref target="terminology"/>) based on the local AS's knowledge of its Role. The only exception is when the eBGP connection is Complex (see <xref target="considerations"/>). BGP Roles are mutually confirmed using the BGP Role Capability (described in <xref target="capability"/>) on each eBGP session. </t> <t> Allowed Roles for eBGP sessions are:<list style="symbols"> <t>Provider - the</t> <dl> <dt>Provider: </dt> <dd>the local AS is a transitProviderprovider of the remoteAS;</t> <t>Customer - theAS; </dd> <dt>Customer: </dt> <dd>the local AS is a transitCustomercustomer of the remoteAS;</t> <t>RS -AS; </dd> <dt>RS: </dt> <dd> the local AS is a Route Server (usually at an Internet exchangepoint)point), and the remote AS is itsRS-Client;</t> <t>RS-Client - theRS-Client; </dd> <dt>RS-Client: </dt> <dd>the local AS is a client of an RS and the RS is the remoteAS;</t> <t>Peer - theAS; and </dd> <dt>Peer: </dt> <dd>the local and remote ASes are Peers (i.e., have a lateral peeringrelationship).</t> </list> </t>relationship). </dd> </dl> <sectionanchor="capability" title="BGPanchor="capability"> <name>BGP RoleCapability">Capability</name> <t> The BGP Role Capability is defined as follows:<list style="symbols"> <t>Code - 9</t> <t>Length - 1 (octet)</t> <t>Value - integer</t> <dl> <dt>Code: </dt> <dd>9 </dd> <dt>Length: </dt> <dd>1 (octet) </dd> <dt>Value: </dt> <dd>integer corresponding to the speaker's BGP Role (see <xreftarget="values"/>).</t> </list> </t> <texttable anchor="values" title="Predefinedtarget="values"/>) </dd> </dl> <table anchor="values"> <name>Predefined BGP RoleValues" suppress-title="false"> <ttcol align="center">Value</ttcol> <ttcolValues</name> <thead> <tr> <th align="center">Value</th> <th align="left">Role name (for the localAS)</ttcol> <c>0</c> <c>Provider</c> <c>1</c> <c>RS</c> <c>2</c> <c>RS-Client</c> <c>3</c> <c>Customer</c> <c>4</c> <c>PeerAS)</th> </tr> </thead> <tbody> <tr> <td align="center">0</td> <td align="left">Provider</td> </tr> <tr> <td align="center">1</td> <td align="left">RS</td> </tr> <tr> <td align="center">2</td> <td align="left">RS-Client</td> </tr> <tr> <td align="center">3</td> <td align="left">Customer</td> </tr> <tr> <td align="center">4</td> <td align="left">Peer (i.e., LateralPeer)</c> <c>5-255</c> <c>Unassigned</c> </texttable>Peer)</td> </tr> <tr> <td align="center">5-255</td> <td align="left">Unassigned</td> </tr> </tbody> </table> <t> If the BGP Role is locally configured, the eBGP speakerMUST<bcp14>MUST</bcp14> advertise the BGP Role Capability in the BGP OPEN message. An eBGP speakerMUST NOT<bcp14>MUST NOT</bcp14> advertise multiple versions of the BGP Role Capability. The error handling when multiple BGP Role Capabilities are received is described in <xref target="correctness"/>. </t> </section> <sectionanchor="correctness" title="Role Correctness">anchor="correctness"> <name>Role Correctness</name> <t> <xref target="capability"/>describeddescribes how the BGP Role encodes the relationship on each eBGP session betweenautonomous systems (ASes).ASes. </t> <t> The mere receipt of the BGP Role Capability does not automatically guarantee the Role agreement between two eBGP neighbors. If the BGP Role Capability is advertised, and one is also received from the peer, the RolesMUST<bcp14>MUST</bcp14> correspond to the relationships inTable 2.<xref target="allowed"/>. If the Roles do not correspond, the BGP speakerMUST<bcp14>MUST</bcp14> reject the connection using the Role Mismatch Notification (code 2, subcodeTBD).11). </t><texttable anchor="allowed" title="Allowed<table anchor="allowed"> <name>Allowed Pairs of RoleCapabilities" suppress-title="false"> <ttcolCapabilities</name> <thead> <tr> <th align="left">Local ASRole</ttcol> <ttcolRole</th> <th align="left">Remote ASRole</ttcol> <c>Provider</c> <c>Customer</c> <c>Customer</c> <c>Provider</c> <c>RS</c> <c>RS-Client</c> <c>RS-Client</c> <c>RS</c> <c>Peer</c> <c>Peer</c> </texttable>Role</th> </tr> </thead> <tbody> <tr> <td align="left">Provider</td> <td align="left">Customer</td> </tr> <tr> <td align="left">Customer</td> <td align="left">Provider</td> </tr> <tr> <td align="left">RS</td> <td align="left">RS-Client</td> </tr> <tr> <td align="left">RS-Client</td> <td align="left">RS</td> </tr> <tr> <td align="left">Peer</td> <td align="left">Peer</td> </tr> </tbody> </table> <t> For backward compatibility, if the BGP Role Capability is sent but one is not received, the BGP SpeakerSHOULD<bcp14>SHOULD</bcp14> ignore the absence of the BGP Role Capability and proceed with session establishment. The locally configured BGP Role is used for the procedures described in <xref target="prevention_attribute"/>. </t> <t> An operator may choose to apply a "strict mode" in which the receipt of a BGP Role Capability from the remote AS is required. When operating in the "strict mode", if the BGP Role Capability issent,sent but one is not received,thenthe connection is rejected using the Role Mismatch Notification (code 2, subcodeTBD).11). See comments in <xref target="Security"/>. </t> <t> If an eBGP speaker receives multiple but identical BGP Role Capabilities with the same value in each, then the speaker considers them to be a single BGP Role Capability and proceeds <xref target="RFC5492"/>. If multiple BGP Role Capabilities are received and not all of them have the same value, then the BGP speakerMUST<bcp14>MUST</bcp14> reject the connection using the Role Mismatch Notification (code 2, subcodeTBD).11). </t> <t> The BGP Role value for the local AS (in conjunction with the OTC Attribute in the received UPDATE message) is used in the route leak prevention and detection procedures described in <xref target="prevention_attribute"/>. </t> </section> </section> <sectionanchor="prevention_attribute" title="BGPanchor="prevention_attribute"> <name>BGP Only to Customer (OTC)Attribute">Attribute</name> <t> TheOnly to Customer (OTC)OTC Attribute is an optional transitivepath attributePath Attribute of the UPDATE message with Attribute Type Code 35 and a length of 4 octets. The purpose of this attribute is to enforce that once a route is sent to a Customer, a Peer, or an RS-Client (see definitions in <xref target="defs"/>), it will subsequently go only to the Customers. The attribute value is an AS number (ASN) determined by the procedures described below. </t> <t> The following ingress procedure applies to the processing of the OTC Attribute on route receipt:<list style="numbers"> <t></t> <ol spacing="normal" type="1"><li> If a route with the OTC Attribute is received from a Customer or an RS-Client, then it is a route leak andMUST<bcp14>MUST</bcp14> be considered ineligible (see <xref target="terminology"/>).</t> <t></li> <li> If a route with the OTC Attribute is received from a Peer (i.e., remote AS with a Peer Role) and the Attribute has a value that is not equal to the remote (i.e., Peer's) AS number, then it is a route leak andMUST<bcp14>MUST</bcp14> be considered ineligible.</t> <t></li> <li> If a route is received from a Provider, a Peer, orRS,an RS and the OTC Attribute is not present, then itMUST<bcp14>MUST</bcp14> be added with a value equal to the AS number of the remote AS.</t> </list> </t></li> </ol> <t> The following egress procedure applies to the processing of the OTC Attribute on route advertisement:<list style="numbers"> <t></t> <ol spacing="normal" type="1"><li> If a route is to be advertised to a Customer, a Peer, or an RS-Client (when the sender is an RS), and the OTC Attribute is not present, then when advertising the route, an OTC AttributeMUST<bcp14>MUST</bcp14> be added with a value equal to the AS number of the local AS.</t> <t></li> <li> If a route already contains the OTC Attribute, itMUST NOT<bcp14>MUST NOT</bcp14> be propagated to Providers, Peers, orRS(s). </t> </list> </t>RSes. </li> </ol> <t> The above-described procedures provide both leak prevention for the local AS and leak detection and mitigation multiple hops away. In the case of prevention at the local AS, the presence of an OTC Attribute indicates to the egress router that the route was learned from a Peer, a Provider, or an RS, and it can be advertised only to thecustomers.Customers. The same OTC Attributewhichthat is set locally also provides a way to detect route leaks by an AS multiple hops away if a route is received from a Customer, a Peer, or an RS-Client. For example, if an AS sets the OTC Attribute on a route sent to a Peer and the route is subsequently received by a compliant AS from a Customer, then the receiving AS detects (based on the presence of the OTC Attribute) that the route is a leak. </t> <t> The OTC Attribute might be set at the egress of the remote AS or at the ingress of the local AS, i.e., if the remote AS is non-compliant with this specification, then the local AS will have to set the OTC Attribute if it is absent. In both scenarios, the OTC value will be the same. This makes the scheme more robust and benefits early adopters. </t> <t> The OTC Attribute is considered malformed if the length value is not 4. An UPDATE message with a malformed OTC AttributeSHALL<bcp14>SHALL</bcp14> be handled using the approach of "treat-as-withdraw" <xref target="RFC7606"/>. </t> <t> The BGP Role negotiation andOTC Attribute basedOTC-Attribute-based procedures specified in this document areNOT RECOMMENDED<bcp14>NOT RECOMMENDED</bcp14> to be used between autonomous systems in an AS Confederation <xref target="RFC5065"/>. If an OTC Attribute is added on egress from the AS Confederation, its valueMUST<bcp14>MUST</bcp14> equal the AS Confederation Identifier. Also, on egress from the AS Confederation, an UPDATEMUST NOT<bcp14>MUST NOT</bcp14> contain an OTC Attribute with a value corresponding to any Member-AS Number other than the AS Confederation Identifier. </t> <t> The procedures specified in this document in scenarios that use private AS numbers behind an Internet-facing ASN (e.g., adata centerdata-center network <xref target="RFC7938"/> or stub customer) may be used, but any details are outside the scope of this document. On egress from the Internet-facing AS, the OTC AttributeMUST NOT<bcp14>MUST NOT</bcp14> contain a value other than the Internet-facing ASN. </t> <t> Once the OTC Attribute has been set, itMUST<bcp14>MUST</bcp14> be preserved unchanged (this also applies to an AS Confederation). </t> <t> The described ingress and egress procedures are applicable only for the address families AFI 1 (IPv4) and AFI 2 (IPv6) with SAFI 1 (unicast) in both cases andMUST NOT<bcp14>MUST NOT</bcp14> be applied to other address families by default. The operatorMUST NOT<bcp14>MUST NOT</bcp14> have the ability to modify the procedures defined in this section. </t> </section> <sectionanchor="considerations" title="Additional Considerations">anchor="considerations"> <name>Additional Considerations</name> <t> RolesMUST NOT<bcp14>MUST NOT</bcp14> be configured on an eBGP session with a Complex peering relationship. If multiple eBGP sessions can segregate the Complex peering relationship into eBGP sessions with normal peering relationships, BGP RolesSHOULD<bcp14>SHOULD</bcp14> be used on each of the resulting eBGP sessions. </t> <t> An operator may want to achieve an equivalent outcome by configuring policies on a per-prefix basis to follow the definitions of peering relations as described in <xref target="defs"/>. However, in this case, there are no in-band measures to check the correctness of the per-prefix peering configuration. </t> <t> The incorrect setting of BGP Roles and/or OTC Attributes may affect prefix propagation. Further, this document does not specify any special handling of an incorrect AS number in the OTC Attribute. </t> <t> In AS migration scenarios <xref target="RFC7705"/>, a given router may represent itself as any one of several different ASes. This should not be a problem since the egress procedures in <xref target="prevention_attribute"/> specify that the OTC Attribute is to be attached as part of route transmission. Therefore, a router is expected to set the OTC value equal to the ASN it is currently representing itself as. </t> <t>Section 6 of<xreftarget="RFC7606"/>target="RFC7606" sectionFormat="of" section="6"/> documents possible negative impacts of "treat-as-withdraw" behavior. Such negative impacts may include forwarding loops orblackholes.dropped traffic. It also discusses debugging considerations related to this behavior. </t> </section> <sectionanchor="IANA" title="IANA Considerations">anchor="IANA"> <name>IANA Considerations</name> <t> IANA has registered a new BGP Capability (<xref target="capability"/>) in the "Capability Codes"registry'sregistry within the "IETF Review" range <xref target="RFC5492"/>. The description for the new capability is "BGP Role". IANA has assigned the value9 [to be removed upon publication: https://www.iana.org/assignments/capability-codes/capability-codes.xhtml].9. This document is the reference for the new capability. </t> <t>The BGP Role capability includes a Value field, for whichIANAis requested to createhas created andmaintainnow maintains a newsub-registrysubregistry called "BGP Role Value"inwithin theCapability Codes"Capability Codes" registry.Assignments consist ofRegistrations should include aValuevalue, a role name, and acorresponding Role name. Initially, this registry isreference tobe populated withthedata contained in <xref target="values"/> founddefining document. IANA has registered the values in <xreftarget="capability"/>.target="role-table"/>. Future assignments may be made by the "IETF Review" policy as defined in <xref target="RFC8126"/>.The registry is as shown in <xref target="role-table"/>.</t><texttable anchor="role-table" title="IANA<table anchor="role-table"> <name>IANA Registry for BGPRole" suppress-title="false"> <ttcol align="center">Value</ttcol> <ttcolRole</name> <thead> <tr> <th align="center">Value</th> <th align="left">Role name (for the localAS)</ttcol> <ttcol align="center">Reference</ttcol> <c>0</c> <c>Provider</c> <c>This document</c> <c>1</c> <c>RS</c> <c>This document</c> <c>2</c> <c>RS-Client</c> <c>This document</c> <c>3</c> <c>Customer</c> <c>This document</c> <c>4</c> <c>PeerAS)</th> <th align="center">Reference</th> </tr> </thead> <tbody> <tr> <td align="center">0</td> <td align="left">Provider</td> <td align="center">This document</td> </tr> <tr> <td align="center">1</td> <td align="left">RS</td> <td align="center">This document</td> </tr> <tr> <td align="center">2</td> <td align="left">RS-Client</td> <td align="center">This document</td> </tr> <tr> <td align="center">3</td> <td align="left">Customer</td> <td align="center">This document</td> </tr> <tr> <td align="center">4</td> <td align="left">Peer (i.e., LateralPeer)</c> <c>This document</c> <c>5-255</c> <c>ToPeer)</td> <td align="center">This document</td> </tr> <tr> <td align="center">5-255</td> <td align="left">To be assigned by IETF Review</c> <c/> </texttable></td> <td align="center"/> </tr> </tbody> </table> <t> IANA has registered a new OPEN Message Error subcode namedthe"Role Mismatch" (see <xref target="correctness"/>) in theOPEN"OPEN Message Errorsubcodessubcodes" registry. IANA has assigned the value11 [to be removed upon publication: https://www.iana.org/assignments/bgp-parameters/bgp-parameters.xhtml#bgp-parameters-6].11. This document is the reference for the new subcode. </t><t> Due<t>Due to improper use of the values 8, 9, and10 in the OPEN Message Error subcodes registry, this document requested IANA to mark these values as "Deprecated".10, IANA has marked values 8-10 as "Deprecated" in theOPEN"OPEN Message Errorsubcodessubcodes" registry. This document is listed as thereference. </t>reference.</t> <t> IANA has also registered a newpath attributePath Attribute named "Only to Customer (OTC)" (see <xref target="prevention_attribute"/>) in the "BGP Path Attributes" registry. IANA has assigned code value35 [To be removed upon publication: http://www.iana.org/assignments/bgp-parameters/bgp-parameters.xhtml#bgp-parameters-2].35. This document is the reference for the new attribute. </t> </section> <sectionanchor="Security" title="Security Considerations">anchor="Security"> <name>Security Considerations</name> <t> The security considerations of BGP (as specified in <xref target="RFC4271"/> and <xref target="RFC4272"/>) apply. </t> <t> This document proposes a mechanismusingthat uses the BGP Role for the prevention and detection of route leaks that are the result of BGP policy misconfiguration. A misconfiguration of the BGP Role may affect prefix propagation. For example, if a downstream (i.e., towards a Customer) peering link were misconfigured with a Provider or Peer Role,this willit would limit the number of prefixes that can be advertised in this direction. On the other hand, if an upstream provider were misconfigured (by a local AS) with the Customer Role,thisit may result in propagating routes that are received from other Providers or Peers. But the BGP Role negotiation and the resulting confirmation of Roles make such misconfigurations unlikely. </t> <t> Setting the strict mode of operation for BGP Role negotiation as the default may result in a situation where the eBGP session will not come up after a software update. Implementations with such default behavior are strongly discouraged. </t> <t> Removing the OTC Attribute or changing its value can limit the opportunity for route leak detection. Such activity can be done on purpose as part of an on-path attack. For example, an AS can remove the OTC Attribute on a received route and then leak the route to its transit provider. This kind of threat is not new inBGPBGP, and it may affect any Attribute(Note:(note that BGPsec <xref target="RFC8205"/> offers protection only for the AS_PATH Attribute). </t> <t> Adding an OTC Attribute when the route is advertised from Customer to Provider will limit the propagation of the route. Such a route may be considered as ineligible by the immediate Provider or its Peers orupper layerupper-layer Providers. This kind of OTC Attribute addition is unlikely to happen on the Provider side because it will limit the traffic volume towards its Customer. On the Customer side, adding an OTC Attribute fortraffic engineeringtraffic-engineering purposes is also discouraged because it will limit route propagation in an unpredictable way. </t> </section> </middle> <back><references title="Normative References"> &RFC2119; &RFC4271; &RFC5065; &RFC5492; &RFC7606; &RFC7908; &RFC8126; &RFC8174;<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.4271.xml"/> <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.5065.xml"/> <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.5492.xml"/> <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.7606.xml"/> <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.7908.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.8174.xml"/> </references><references title="Informative References"> &RFC8205; &RFC4272; &RFC7938; &RFC7705;<references> <name>Informative References</name> <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.8205.xml"/> <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.4272.xml"/> <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.7938.xml"/> <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.7705.xml"/> <referenceanchor="Gao"anchor="GAO-REXFORD" target="https://ieeexplore.ieee.org/document/974523"> <front> <title>Stable Internet routing without global coordination</title> <author initials="L." surname="Gao"> </author> <author initials="J." surname="Rexford"> </author> <datemonth='December' year='2001' />month="December" year="2001"/> </front><seriesInfo name='' value='IEEE/ACM<refcontent>IEEE/ACM Transactions on Networking, Volume 9, Issue 6,pp 689-692, DOI 10.1109/90.974523' />pp. 689-692 </refcontent> <seriesInfo name="DOI" value="10.1109/90.974523"/> </reference> </references> </references> <sectiontitle="Acknowledgments" numbered="no">numbered="false"> <name>Acknowledgments</name> <t> The authors wish to thankAlvaro Retana, Bruno Decraene, Jeff Haas, John Scudder, Sue Hares, Ben Maddison, Andrei Robachevsky, Daniel Ginsburg, Ruediger Volk, Pavel Lunin, Gyan Mishra, and Ignas Bagdonas<contact fullname="Alvaro Retana"/>, <contact fullname="Bruno Decraene"/>, <contact fullname="Jeff Haas"/>, <contact fullname="John Scudder"/>, <contact fullname="Sue Hares"/>, <contact fullname="Ben Maddison"/>, <contact fullname="Andrei Robachevsky"/>, <contact fullname="Daniel Ginsburg"/>, <contact fullname="Ruediger Volk"/>, <contact fullname="Pavel Lunin"/>, <contact fullname="Gyan Mishra"/>, and <contact fullname="Ignas Bagdonas"/> forreview,their reviews, comments, and suggestions during the course of this work. Thanks are also due to many IESG reviewers whose comments greatly helped improve the clarity, accuracy, and presentation in the document. </t> </section> <sectiontitle="Contributors" numbered="no"> <figure><artwork><![CDATA[ Brian Dickson Independent Email: brian.peter.dickson@gmail.com Doug Montgomery USAnumbered="false"> <name>Contributors</name> <author fullname="Brian Dickson" initials="B" surname="Dickson"> <organization>Independent</organization> <address> <email>brian.peter.dickson@gmail.com</email> </address> </author> <author fullname="Doug Montgomery" initials="D" surname="Montgomery"> <organization>USA National Institute of Standards andTechnology Email: dougm@nist.gov ]]></artwork></figure>Technology</organization> <address> <email>dougm@nist.gov</email> </address> </author> </section> </back> </rfc>