<?xml version='1.0' encoding='utf-8'?>
<?xml-stylesheet type='text/xsl' href='rfc2629.xslt' ?>
<!-- <xi:strict="yes" ?>
<xi:compact="yes" ?>
<xi:subcompact="no" ?>  --> version="1.0" encoding="UTF-8"?>

<!DOCTYPE rfc [
 <!ENTITY nbsp    "&#160;">
 <!ENTITY zwsp   "&#8203;">
 <!ENTITY nbhy   "&#8209;">
 <!ENTITY wj     "&#8288;">
]>

<rfc	xmlns:xi="http://www.w3.org/2001/XInclude"
	submissionType="IRTF"
	category="exp"
	consensus="true"
	docName="draft-irtf-icnrg-icnping-12"
	number="9508"
	ipr="trust200902"
	obsoletes=""
	updates=""
	submissionType="IRTF"
	xml:lang="en"
	tocInclude="true"
	tocDepth="4"
	symRefs="true"
	sortRefs="true"
	version="3">

  <front>
    <title abbrev="ICN Ping">ICN Ping">Information-Centric Networking (ICN) Ping Protocol Specification</title>

    <seriesInfo name="Internet-Draft" value="draft-irtf-icnrg-icnping-12"/> name="RFC" value="9508"/>
    <author fullname="Spyridon Mastorakis" initials="S" surname="Mastorakis">
      <organization>University of Notre Dame</organization>
      <address>
        <postal>
          <street/>
          <city>South Bend</city>
          <region>IN</region>
          <code/>
          <country>US</country>
          <country>United States of America</country>
        </postal>
        <email>smastor2@nd.edu</email>
      </address>

    </author>

    <author fullname="Dave Oran" initials="D" surname="Oran">
      <organization>Network Systems Research and Design</organization>
      <address>
        <postal>
          <street/>
          <city>Cambridge</city>
          <region>MA</region>
          <code/>
          <country>US</country>
          <country>United States of America</country>
        </postal>
        <email>daveoran@orandom.net</email>
      </address>
    </author>

    <author fullname="Jim Gibson" initials="J" surname="Gibson">
      <organization>Unaffiliated</organization>
      <address>
        <postal>
          <street/>
          <city>Belmont</city>
          <region>MA</region>
          <code/>
          <country>US</country>
          <country>United States of America</country>
        </postal>
        <email>jcgibson61@gmail.com</email>
      </address>
    </author>

    <author fullname="Ilya Moiseenko" initials="I" surname="Moiseenko">
      <organization>Apple Inc</organization> Inc.</organization>
      <address>
        <postal>
          <street/>
          <city>Cupertino</city>
          <region>CA</region>
          <code/>
          <country>US</country>
          <country>United States of America</country>
        </postal>
        <email>iliamo@mailbox.org</email>
        <!-- uri and facsimile elements may also be added -->
      </address>
    </author>

    <author fullname="Ralph Droms" initials="R" surname="Droms">
      <organization>Unaffiliated</organization>
      <address>
        <postal>
          <street/>
          <city>Hopkinton</city>
          <region>MA</region>
          <code/>
          <country>US</country>
          <country>United States of America</country>
        </postal>
        <email>rdroms.ietf@gmail.com</email>
      </address>

    </author>

    <date year="2023"/>

    <!-- Meta-data Declarations -->

    <area>IRTF</area>
    <workgroup>ICNRG</workgroup> year="2024" month="March" />

    <workgroup>Information-Centric Networking</workgroup>

    <keyword>ICN</keyword>
    <keyword>Network Management</keyword>

    <abstract>
      <t>This document presents the design of an ICN Information-Centric Networking (ICN) Ping protocol. It includes the operations of both the client and the forwarder.</t>
      <t>This document is a product of the Information-Centric Networking Research Group (ICNRG) of the IRTF.</t>
    </abstract>
  </front>

  <middle>
    <section numbered="true" toc="default">
      <name>Introduction</name>
      <t>Ascertaining data plane reachability to a destination and taking
        coarse performance measurements of round trip time Round-Trip Time (RTT) are fundamental
        facilities for network administration and troubleshooting.  In IP,
        where routing and forwarding are based on IP addresses, ICMP echo Echo
        Request and ICMP echo response Echo Reply packets are the protocol mechanisms used for this
        purpose, generally exercised through the familiar ping utility. In
	ICN,
        Information-Centric Networking (ICN), where routing and forwarding are based on name prefixes, the
        ability to ascertain the reachability of names is required.</t>

      <t> This document proposes protocol mechanisms for a ping equivalent in
        ICN networks (<xref target="RFC8609">CCNx</xref> target="RFC8609">Content-Centric Networking (CCNx)</xref> and <xref target="NDNTLV">NDN</xref>) networks. target="NDNTLV">Named Data Networking (NDN)</xref>). A non-normative appendix section (<xref target="app-additional"/>) suggests useful properties for an ICN
	ping
        Ping client application, analogous to IP ping, that originates echo requests Echo Requests
        and processes echo replies.</t> Echo Replies.</t>

        <t> In order to carry out meaningful experimentation and deployment of ICN
                protocols, new tools analogous to ping and traceroute used for
   TCP/IP are needed to manage and debug the operation of ICN
   architectures and
		protocols are needed analogous to ping and traceroute used for TCP/IP. protocols.
                This document describes the design of a management and debugging protocol
                analogous to the ping protocol of TCP/IP, which TCP/IP; this new management and debugging protocol will aid
                the experimental deployment of ICN protocols. As the community continues its
                experimentation with ICN architectures and protocols, the design of ICN Ping
                might change accordingly. ICN Ping is designed as a "first line of defense"
                tool to troubleshoot ICN architectures and protocols. As such, this document is
                classified as an experimental Experimental RFC.
Note that a measurement application is needed to make proper use of ICN Ping in order to compute various statistics, such as the variance, average, maximum maximum, and minimum RTT values as well as Round-Trip Time (RTT) values, variance in RTTs, and loss rates.</t>

        <t>This document is not an Internet Standards Track specification; it is
			published for examination, experimental implementation, and evaluation.
			This document defines an Experimental Protocol for the Internet
			community. This document is a product of the Internet Research Task
			Force (IRTF). The IRTF publishes the results of Internet-related
			research and development activities. These results might not be
			suitable for deployment. This RFC represents the consensus of the Information-Centric Networking Research Group (ICNRG) of the Internet Research Task Force (IRTF). Documents approved for publication by
			the IRSG are not candidates for any level of Internet Standard; see
			Section 2 of RFC 7841.</t> (IRTF).</t>

      <section numbered="true" toc="default">
        <name>Requirements Language</name>
         <t>The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
        "SHOULD", "SHOULD 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 BCP&nbsp;14
         <xref target="RFC2119"/> <xref target="RFC8174"/> when, and only
         when, they appear in all capitals, as shown here.</t>
      </section>

      <section numbered="true" toc="default">
        <name>Terminology</name>
        <t>This specification uses the terminology defined in <xref target="RFC8793"/>. To aid the understanding of readers, reader, we additionally define the following terms:</t>
        <ul>
            <li>Producer's name: The
        <dl spacing="normal">
            <dt>Producer's Name:</dt><dd>The name prefix that a request must carry in order to reach a producer over an ICN network.</li>
            <li>Named Data: A network.</dd>
            <dt>Named Data:</dt><dd>A synonym for a content object.</li>
            <li>Round Trip Content Object.</dd>
            <dt>Round-Trip Time (RTT): The (RTT):</dt><dd>The time between sending a request for a specific piece of named data and receiving the corresponding piece of named data.</li>
            <li>Sender: An data.</dd>
            <dt>Sender:</dt><dd>An entity that sends a request for named data or a piece of named data.</li>
            <li>Name data.</dd>
            <dt>Name of a sender: An Sender:</dt><dd>An alias of a producer's name.</li>
            <li>Border forwarder: The name.</dd>
            <dt>Border Forwarder:</dt><dd>The forwarder that is the border of a network region where a producer's name is directly routable (i.e., the producer's name is present in the FIB of forwarders within this network region).</li>
        </ul> region).</dd>
        </dl>
      </section>
    </section>
    <section numbered="true" toc="default">
      <name>Background on IP-Based Ping Operation</name>
      <t>In IP-based ping, an IP address is specified by the user either directly, directly or via
            translation of a domain name through DNS. The ping client application
            sends a number of ICMP Echo Request packets with the specified IP
            address as the IP destination address and an IP address from the client's host
            as the IP source address.</t>
      <t>Each ICMP Echo Request is forwarded across
            the network based on its destination IP address. If it eventually reaches the
            destination, the destination responds by sending back an ICMP Echo Reply
            packet to the IP source address from the ICMP Echo Request.</t>
      <t>If an ICMP Echo Request does not reach the destination or the
            Echo reply Reply is lost, the ping client times out. Any ICMP error messages,
            such as "no route to destination", messages
            generated by in response to the ICMP Echo Request message message, such as "No route to destination", are returned to the client and reported.</t>
    </section>
    <section numbered="true" toc="default">
      <name>Ping Functionality Challenges and Opportunities in ICN</name>
      <t> In ICN, the communication paradigm is based exclusively on named
      objects. An Interest message is forwarded across the network based on the name prefix that it carries.
      Eventually, a content object Content Object is retrieved either from either a producer
      application or some forwarder's Content Store (CS).</t>
      <t>IP-based ping was built as an add-on measurement and debugging tool on top of an already existing already-existing network architecture. In ICN, we have the opportunity to incorporate diagnostic
      mechanisms directly in the network layer protocol, and hopefully network-layer protocol and, hopefully, provide more powerful
      diagnostic capability than can be realized through the layered ICMP Echo approach.</t>
      <t>An ICN network differs from an IP network in at least 4 four important ways:</t> ways (four of which are as follows):</t>
      <ul spacing="normal">
        <li>IP identifies interfaces to an IP network with a fixed-length
              address,
              address and delivers IP packets to one or more of these interfaces. ICN
              identifies units of data in the network with a variable length variable-length name
              consisting of a hierarchical list of name components.</li>
        <li>An IP-based network depends on the IP packets having source IP  addresses that are used as the destination address for replies. On the other hand, ICN Interests do not have source addresses addresses, and they are forwarded based on names, which do not refer to a unique end-point. endpoint. Data packets follow the reverse path of the Interests based on hop-by-hop state
              created during Interest forwarding.</li>
        <li>An IP network supports multi-path, single destination, single-destination, stateless packet
              forwarding and delivery via unicast, unicast; a limited form of
              multi-destination selected delivery with anycast, anycast; and group-based
              multi-destination delivery via multicast. In contrast, ICN supports
              multi-path and multi-destination stateful Interest forwarding and
              multi-destination delivery of named data.  This single
              forwarding semantic subsumes the functions of unicast, anycast, and
              multicast.  As a result, consecutive (or retransmitted) ICN Interest
              messages may be forwarded through an ICN network along different
              paths,
              paths and may be forwarded to different data sources (e.g., end-node
              applications,
              applications and in-network storage) holding a copy of the
              requested unit of data.  This can lead to a significant variance in
              round-trip times, which
              RTTs; such variance, while resulting in a more robust overall forwarding architecture, has implications for a network
              troubleshooting mechanism like ping.</li>
        <li>In the case of multiple Interests with the same name arriving
              at a forwarder, a number of Interests may be aggregated in a common Pending
              Interest Table (PIT) entry and only one of them forwarded onward. Depending on the lifetime of a PIT entry,
              the round-trip time RTT of an Interest-Data exchange might significantly vary significantly
              (e.g., it might be shorter than the full round-trip time RTT to reach the
              original content producer). To this end, the round-trip time RTT experienced
              by consumers might also vary.</li>
      </ul>

      <t>These differences introduce new challenges, new opportunities opportunities, and new
      requirements in regarding the design of an ICN ping Ping protocol. Following this communication
      model, a ping client should be able to express ping echo requests Ping Echo Requests
      with some name prefix and receive responses.</t>
      <t>Our goals are the following:</t> as follows:</t>
      <ul spacing="normal">
        <li>Test the reachability and the operational state of an ICN forwarder.</li>
        <li>Test the reachability of a producer or a data repository (in the sense of whether
        Interests for a prefix that it serves can be forwarded to it) it), and discover the
        forwarder with local connectivity to (an instance of) this producer or repository.</li>
        <li>Test whether a specific named object is cached in some on-path CS
                                        (e.g., a video segment with a the name "/video/_seq=1”), "/video/_seq=1"),
        and, if so, return the administrative name of the corresponding forwarder
        (e.g., a forwarder with an the administrative name "/ISP/forwarder1”).</li> "/ISP&wj;/forwarder1").</li>
        <li>Perform some simple network performance measurements, such as RTT and loss rate.</li>
      </ul>

      <t>To this end, a ping name can represent:</t>
      <ul spacing="normal">
        <li>An administrative name that has been assigned to a forwarder.</li>
        <li>A name that includes an application's namespace as a prefix.</li>
        <li>A named object that might reside in some in-network storage.</li>
      </ul>

      <t>In order to provide stable and reliable diagnostics, it is desirable that the packet encoding of a ping echo request Ping Echo Request enable the forwarders to distinguish a ping from a normal Interest, while also allowing for
      forwarding behavior to be diverging as similar little as possible to that of from the forwarding behavior for an Interest packet. In the same way, the encoding of a ping echo reply Ping Echo Reply should allow for forwarder minimize any processing as close as possible to that used differences from those employed for a data
      packets.</t> packet by the forwarders.</t>

      <t>The ping protocol should also enable relatively robust round-trip time RTT
      measurements. To this end, it is valuable to have a mechanism to steer
      consecutive ping echo requests Ping Echo Requests for the same name towards an individual path. Such a capability was initially published in  <xref target="PATHSTEERING" format="default"/> and has been specified for CCNx and NDN in <xref target="I-D.irtf-icnrg-pathsteering"/>.</t>

      <t>It is also important, in target="RFC9531"/>.</t>

      <t>In the case of ping echo requests Ping Echo Requests for the same name from different sources sources, it is also important to have a mechanism to avoid those requests being aggregated in the PIT. To this end, we need some encoding in the ping echo requests Ping Echo Requests
      to make each request for a common name unique, hence avoiding PIT aggregation and
      further enabling the exact match of a response with a particular ping packet. However, avoiding PIT aggregation could lead to PIT DoS attacks.</t>
    </section>

    <section numbered="true" toc="default">
      <name>ICN Ping Echo CCNx Packet Formats</name>
      <t>In this section, we describe the Echo Packet Format packet formats according to the
      CCNx packet format <xref target="RFC8569" format="default"/>, where
      messages exist within outermost containments (packets).
      Specifically, we specify propose two types
      of ping packets, packets: an echo request Echo Request and an echo reply packet type.</t> Echo Reply.</t>
      <section numbered="true" toc="default">
        <name>ICN Ping Echo Request CCNx Packet Format</name>
        <t>The format of the ping echo request Ping Echo Request packet is presented below:</t>

        <figure align="center" anchor="ping-packet">
        <name>Echo Request CCNx Packet Format</name>
        <artwork align="left" name="" type="" alt=""><![CDATA[
  0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
 +---------------+---------------+---------------+---------------+
 |               |               |                               |
 |    Version    |PT_ECHO_REQUEST|         PacketLength          |
 |               |               |                               |
 +---------------+---------------+---------------+---------------+
 |               |               |               |               |
 |    HopLimit   |    Reserved   |     Flags     |  HeaderLength |
 |               |               |               |               |
 +---------------+---------------+---------------+---------------+
 /                                                               /
 /                   Path label Label TLV                              /
 /                                                               /
 +---------------+---------------+---------------+---------------+
 |                                                               |
 |                   Echo Request Message TLVs                   |
 |                                                               |
 +---------------+---------------+---------------+---------------+
]]></artwork>
        </figure>

        <t>The existing packet header fields have the same definition as the header fields of a CCNx Interest packet. The value of the packet type field is <em>PT_ECHO_REQUEST</em>. See &nbsp;See <xref target="IANA"/> for the value assignments.</t> assignment.</t>

        <t>Compared to the typical format of a CCNx packet header from <xref target="RFC8569" target="RFC8609" format="default"/>, in order to enable path steering of Echo Requests, there is an a new optional fixed header Path label TLV as specified in section 3.1 of <xref target="I-D.irtf-icnrg-pathsteering"/>
added to the packet header:</t>

 <ul>
  <li>A Path Steering hop-by-hop header TLV, which is constructed hop by hop in the Ping Echo Reply and included in the Ping Echo Request to steer consecutive requests expressed by a client towards a common forwarding path or different forwarding paths. The Path Label TLV is specified in <xref target="RFC9531" sectionFormat="of"/>.</li>
 </ul>

        <t>The message format of an echo request Echo Request is presented below:</t>

        <figure align="center" anchor="echo-request">
        <name>Echo Request Message Format</name>

        <artwork align="left" name="" type="" alt=""><![CDATA[
  0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
 +---------------+---------------+---------------+---------------+
 |                               |                               |
 |        MessageType = 0x0005 0x05     |          MessageLength        |
 |                               |                               |
 +---------------+---------------+---------------+---------------+
 |                                                               |
 |                           Name TLV                            |
 |                                                               |
 +---------------+---------------+---------------+---------------+
]]></artwork>
       </figure>

        <t>The echo request Echo Request message is of type T_DISCOVERY. The Name TLV
       has the structure described in <xref target="RFC8609"/>.
       The name consists of the prefix that we would like to ping appended with
       a nonce typed name segment (T_NONCE) as its last segment. The nonce can be encoded as a base64-encoded string with the URL-safe alphabet as defined in Section 5 of <xref target="RFC4648"/>, target="RFC4648" sectionFormat="of" section="5"/>, with padding omitted. See <xref target="IANA"/> for the value assigned to this name segment type. The value of this TLV is a 64-bit nonce.
       The purpose of the nonce is to avoid Interest aggregation and allow client matching of replies with requests. As described below, the nonce is ignored for CS checking.</t>

       <figure align="center">
       <name>T_NONCE Name Segment TLV for Echo Request messages</name> Messages</name>
        <artwork align="left" name="" type="" alt=""><![CDATA[
  0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
 +---------------+---------------+---------------+---------------+
 |                               |                               |
 |        T_NONCE_Type           |       T_NONCE_Length = 8      |
 |                               |                               |
 +---------------+---------------+---------------+---------------+
 |                                                               |
 |                                                               |
 |                                                               |
 |                         T_NONCE_Value                         |
 |                                                               |
 |                                                               |
 +---------------+---------------+---------------+---------------+
]]></artwork>
      </figure>

      </section>
      <!-- This PI places the pagebreak correctly (before the section title) in the text output. -->

    <section anchor="CCNxReply" numbered="true" toc="default">
        <name>Ping
        <name>ICN Ping Echo Reply CCNx Packet Format</name>
        <t>The format of a ping echo reply Ping Echo Reply packet is presented below:</t>

        <figure align="center">
        <name>Echo Reply CCNx Packet Format</name>
        <artwork align="left" name="" type="" alt=""><![CDATA[
  0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
 +---------------+---------------+---------------+---------------+
 |               |               |                               |
 |    Version    | PT_ECHO_REPLY |         PacketLength          |
 |               |               |                               |
 +---------------+---------------+---------------+---------------+
 |                               |               |               |
 |            Reserved           |     Flags     | HeaderLength  |
 |                               |               |               |
 +---------------+---------------+---------------+---------------+
 /                                                               /
 /                        Path label Label TLV                         /
 /                                                               /
 +---------------+---------------+---------------+---------------+
 |                                                               |
 |                    Echo Reply Message TLVs                    |
 |                                                               |
 +---------------+---------------+---------------+---------------+
]]></artwork>
        </figure>

        <t>The header of an echo reply Echo Reply consists of the header fields of a CCNx Content
       Object and a hop-by-hop Path label Label TLV. The value of the packet type
       field is PT_ECHO_REPLY. See <xref target="IANA"/> for the value assignments. assignment.
       The Path label Label header TLV from section 3.1 of <xref target="I-D.irtf-icnrg-pathsteering"/> (<xref target="RFC9531" sectionFormat="of" section="3.1"/>)
       is as defined for the echo request Echo Request packet.</t>

        <t>A ping echo reply Ping Echo Reply message is of type T_OBJECT, T_OBJECT and contains a Name TLV
       (name of the corresponding echo request), Echo Request), a PayloadType TLV TLV, and an
       ExpiryTime TLV with a value of 0 to indicate that echo replies Echo Replies must
       not be returned from network caches.</t>

       <figure align="center">
       <name>Echo Reply Message Format</name>
        <artwork align="left" name="" type="" alt=""><![CDATA[
  0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
 +---------------+---------------+---------------+---------------+
 |                               |                               |
 |        MessageType = 0x0005 0x06     |          MessageLength        |
 |                               |                               |
 +---------------+---------------+---------------+---------------+
 |                                                               |
 |                           Name TLV                            |
 |                                                               |
 +---------------+---------------+---------------+---------------+
 |                                                               |
 |                       PayloadType TLV                         |
 |                                                               |
 +---------------+---------------+---------------+---------------+
 |                                                               |
 |                       ExpiryTime TLV                          |
 |                                                               |
 +---------------+---------------+---------------+---------------+
]]></artwork>
        </figure>

        <t>The PayloadType TLV is presented below. It is of type T_PAYLOADTYPE_DATA, and
       the data schema consists of 3 TLVs: 1) the three TLVs:</t>
        <ol type="%d)">
         <li>the name of the sender of this reply
       (with the same structure as a CCNx Name TLV), 2) the TLV),</li>
         <li>the sender's signature of
       their own name (with the same structure as a CCNx ValidationPayload TLV),
       3) a and</li>
         <li>a TLV with a return code to indicate what led to the generation of this reply
       (i.e., the existence of a local application, a CS hit hit, or a match with a forwarder's
       administrative name as specified in <xref target="forwarder" format="default"/>).</t> format="default"/>).</li>
	</ol>

       <figure align="center">
       <name>Echo Reply Message PayloadType TLV Format</name>
        <artwork align="left" name="" type="" alt=""><![CDATA[
  0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
 +---------------+---------------+---------------+---------------+
 |                               |                               |
 |       T_PAYLOADTYPE_DATA      |             Length            |
 |                               |                               |
 +---------------+---------------+---------------+---------------+
 /                                                               /
 /                      Sender's Name TLV                        /
 /                                                               /
 +---------------+---------------+---------------+---------------+
 /                                                               /
 /                    Sender's Signature TLV                     /
 /                                                               /
 +---------------+---------------+---------------+---------------+
 /                                                               /
 /                     Echo Reply Code                           /
 /                                                               /
 +---------------+---------------+---------------+---------------+
]]></artwork>
        </figure>

        <t>The goal of including the name of the sender in the echo reply Echo Reply is to enable the
      user to reach this entity directly to ask for further management/administrative
      information using generic Interest-Data exchanges or by employing a more comprehensive management tool tool, such as <xref target="RFC9344">CCNinfo</xref> target="RFC9344">CCNinfo</xref>,
      after a successful verification of the sender's name.</t>
        <t>The types of the Echo Reply Code field are the following:</t>
        <ul as follows:</t>
        <dl spacing="normal">
          <li>T_ECHO_RETURN_FORWARDER: Indicates
          <dt>T_ECHO_RETURN_FORWARDER:</dt><dd>Indicates that the target name matched the administrative name of a forwarder.</li>
          <li>T_ECHO_RETURN_APPLICATION: Indicates forwarder.</dd>
          <dt>T_ECHO_RETURN_APPLICATION:</dt><dd>Indicates that the target name matched a prefix served by an application.</li>
          <li>T_ECHO_RETURN_OBJECT: Indicates application.</dd>
          <dt>T_ECHO_RETURN_OBJECT:</dt><dd>Indicates that the target name matched the name of an object in a forwarder's CS.</li>
        </ul> CS.</dd>
        </dl>
      </section>
    </section>

    <section numbered="true" toc="default">
      <name>ICN Ping Echo NDN Packet Formats</name>
      <t>In this section, we present the ICN Ping Echo Request and Reply Format packet formats according to the NDN packet format specification
    <xref target="NDNTLV" format="default"/>.</t>
      <section numbered="true" toc="default">
        <name>ICN Ping Echo Request NDN Packet Format</name>
        <t>An echo request Echo Request is encoded as an NDN Interest packet. Its format is the following:</t> as follows:</t>

        <figure align="center">
        <name>Echo Request NDN Packet Format</name>
        <artwork align="left" name="" type="" alt=""><![CDATA[
        EchoRequest = INTEREST-TYPE TLV-LENGTH
              Name
                          MustBeFresh
                          Nonce
                          ApplicationParameters?
]]></artwork>
        </figure>

        <t>The name field of an echo request Echo Request consists of the name prefix to be pinged, a nonce value (it can be the value of the Nonce field) field), and the suffix "ping" to denote that this Interest is a ping request (added as a KeywordNameComponent). KeywordNameComponent <xref target="NDNTLV"/>). When the "ApplicationParameters" element is present, a parametersSha256DigestComponent ParametersSha256DigestComponent (<xref target="forwarder"/>) is added as the last name segment.</t>

        <t>An echo request MAY Echo Request <bcp14>MAY</bcp14> carry a Path label Label TLV in the <xref target="NDNLPv2">NDN Link Adaptation Protocol</xref> as specified in <xref target="I-D.irtf-icnrg-pathsteering"/>.</t> target="RFC9531"/>.</t>

        <t>Since the NDN packet format does not provide a mechanism to prevent the network from caching specific data packets, we use the MustBeFresh element TLV for echo requests Echo Requests (in combination with a Freshness Period FreshnessPeriod TLV of with a value of 1 for echo replies) Echo Replies) to avoid fetching cached echo replies Echo Replies with an expired freshness period <xref target="REALTIME" format="default"/>.</t>
      </section>

      <section numbered="true" toc="default">
        <name>Ping
        <name>ICN Ping Echo Reply NDN Packet Format</name>
        <t>An echo reply Echo Reply is encoded as an NDN Data packet. Its format is the following:</t> as follows:</t>

        <figure align="center">
        <name>Echo Reply NDN Packet Format</name>
        <artwork align="left" name="" type="" alt=""><![CDATA[
        EchoReply = DATA-TLV TLV-LENGTH
                        Name
                        MetaInfo
                        Content
                        Signature
]]></artwork>
        </figure>

        <t>An echo reply MAY contain Echo Reply <bcp14>MAY</bcp14> carry a Path label Label TLV in the <xref target="NDNLPv2">NDN Link Adaptation Protocol</xref> as specified in <xref target="I-D.irtf-icnrg-pathsteering"/>, target="RFC9531"/>, since it might be modified in a hop-by-hop fashion by the forwarders along the reverse path.</t>

        <t>The name of an echo reply Echo Reply is the name of the corresponding echo request, Echo Request while the format of the MetaInfo field is the following:</t> as follows:</t>

      <figure align="center">
      <name>MetaInfo TLV</name>
        <artwork align="left" name="" type="" alt=""><![CDATA[
      MetaInfo = META-INFO-TYPE TLV-LENGTH
                     ContentType
                     FreshnessPeriod
]]></artwork>
        </figure>

        <t>The value of the ContentType TLV is 0. The value of the
      FreshnessPeriod TLV is 1, so that the replies are treated as stale data (almost instantly) as they are received by a forwarder.</t>

        <t>The content of an echo reply Echo Reply consists of the following 2 two TLVs: Sender's name Name
      (with a structure similar as to an NDN Name TLV) and Echo Reply Code. There is no need to have a separate TLV for the sender's signature in the content of the reply, since every NDN data Data packet carries the signature of the data producer.</t>

      <t>The Echo Reply Code TLV format is the following as follows (with the values specified in
      <xref target="CCNxReply" format="default"/>):</t>

      <figure align="center">
      <name>Echo Reply Code TLV</name>
        <artwork align="left" name="" type="" alt=""><![CDATA[
        EchoReplyCode = ECHOREPLYCODE-TLV-TYPE TLV-LENGTH 2*OCTET
]]></artwork>
        </figure>

      </section>
    </section>

    <section anchor="forwarder" numbered="true" toc="default">
      <name>Forwarder Handling</name>
      <t>We present the workflow of the forwarder's operation in <xref target="forwarder-operation"/>. target="forwarder-operation"/> below. When a forwarder receives an echo request, Echo Request, it first extracts the message's base name (i.e., the request name with the Nonce name segment excluded as well as the suffix "ping" and the ParametersSha256DigestComponent in the case of an echo request Echo Request with the NDN packet format).</t>

      <t>In some cases, the forwarder originates an echo reply, Echo Reply,
        sending the reply downstream through the face on which the
	echo request
        Echo Request was received. This echo reply Echo Reply includes the forwarder's
        own name and signature and the appropriate echo reply code Echo Reply Code based on the condition that
        triggered the reply generation. generation of the reply. It also includes a Path label Label TLV, initially containing a
        null value (since the echo reply Echo Reply originator did does not
        forward the request and, thus, and thus does not make a path choice).</t>
      <t>The forwarder generates and returns an echo reply Echo Reply in the
        following cases:</t>
      <ul spacing="normal">
        <li>Assuming that a forwarder has been given one or more administrative names,
           the echo request Echo Request base name exactly matches any of the forwarder's
           administrative name(s).</li> names.</li>
        <li>The echo request's Echo Request's base name exactly matches the name of a content-object Content Object
           residing in the forwarder's CS (unless the ping client application
           has chosen not to receive replies due to CS hits as specified in
           <xref target="app-additional" format="default"/>).</li>
        <li>The echo request Echo Request base name matches (in a Longest Name Prefix Match (LNPM) manner) a FIB
           entry with an outgoing face referring to a local application.</li>
      </ul>
      <t>If none of the conditions to reply for replying to the echo request Echo Request are met, the
        forwarder will attempt to forward the echo request Echo Request upstream based on the path
	steering Path
        Steering value (if present), the results of the
        FIB LPM LNPM lookup and PIT creation (based creation. These lookups are based on the name including the nonce typed name segment Nonce and the suffix "ping" as name segments of the Name in the case of an echo request Echo Request with the NDN packet format). format. If no valid next-hop next hop is found, an
        InterestReturn is sent downstream indicating "no route" "No Route" (as with a failed attempt to
        forward an ordinary Interest).</t>
      <t>A received echo reply Echo Reply will be matched to an existing PIT entry as usual. On
        the reverse path, the path steering Path Steering TLV of an echo reply Echo Reply will be updated
        by each forwarder to encode its next-hop choice. When included in subsequent
	echo requests,
        Echo Requests, this  Path label Label TLV allows the forwarders to steer
        the echo requests Echo Requests along the same path.</t>
      <figure align="center" anchor="forwarder-operation">
      <name>Forwarder Operation</name>
            <artwork><![CDATA[
------------------------------------------------------------------------
                              FORWARD PATH
------------------------------------------------------------------------

Request +------+  +-----+  +-----+(path label)  +--------+(match)Request
------> |Admin |->| CS  |->| PIT | ------------>| Label  |------------->
        | Name |  +-----+  +-----+              | Lookup |
        |Lookup|     |       | \ (no path label)+--------+
        +------+     |       |  \                |\(path label mismatch)
Reply       |        |       |   \               | \
  <---------+        |       v    \              |  \
  (base matches      |   aggregate \             |   \
   admin name)       |              \            |    \
                     | (base         \           |     +------+ Request
             Reply   |  matches       +----------|---->| FIB  | ------->
           <---------+  cached object)           |     +------+
                                                 |  (no   |  | (base
  Interest-Return
  InterestReturn (NACK)                          v  route)|  | matches
  <----------------------------------------------+<-------+  | local app
  <----------------------------------------------------------+ face)
  Reply

------------------------------------------------------------------------
                              REVERSE PATH
------------------------------------------------------------------------

Interest-return(NACK)

InterestReturn (NACK) +-----+ (update path label) Interest-Return(NACK) InterestReturn (NACK)
<---------------------|     |<-----------------------------------------
                      |     |
Reply  +------+       | PIT |  (update path label)                Reply
<------|  CS  |<------|     |<-----------------------------------------
       +------+       |     |
                      +-----+
                         |
                         | (no match)
                         v
]]></artwork>
          </figure>

    </section>

    <section anchor="local" numbered="true" toc="default">
      <name>Protocol Operation For Locally-Scoped for Locally Scoped Namespaces</name>
      <t>In this section, we elaborate on 2 two alternative design approaches in cases that where
        the pinged prefix corresponds to a locally-scoped locally scoped namespace not directly routable from the
        client's local network.</t>
      <t>The first approach leverages the NDN Link Object <xref target="SNAMP" format="default"/>.
        Specifically, the ping client attaches to the expressed request a LINK Link Object that
        contains a number of routable name prefixes, based on which the request can be forwarded
        until it reaches a network region where the request name itself is
        routable. A LINK Link Object is created and signed by a data producer allowed to
        publish data under a locally-scoped locally scoped namespace. The way that a client retrieves a LINK Link Object
        depends on various network design factors and is out of the scope of for this document.</t>
      <t> At the current draft.</t>
      <t>Based time of this writing, and based on the current usage of the LINK Link Object
 by the NDN team, team <xref target="NDNLPv2"/>, a forwarder at the border of the region
 where an Interest name becomes routable must remove the LINK Link Object
 from incoming Interests. The Interest state maintained along the entire forwarding path is based on the
        Interest name regardless of whether it was forwarded based on its name or a routable prefix in the
	LINK
        Link Object.</t>
      <t>The second approach is based on prepending a routable prefix to the locally-scoped locally scoped
        name. The resulting prefix will be the name of the echo requests Echo Requests expressed by the client.
        In this way, a request will be forwarded based on the routable
        part of its name. When it reaches the network region where the original locally-scoped locally scoped
        name is routable, the border forwarder rewrites the request name and deletes
        its routable part. There are two conditions for a forwarder to perform this rewriting operation
        on a request: 1) the request:</t>
        <ol type="%d)">
         <li>the routable part of the request name
        matches a routable name of the network region adjacent to the forwarder (assuming that a forwarder is aware of
        those names) and 2) the names), and</li>
         <li>the remaining part of the request name is routable across the
        network region of this forwarder.</t> forwarder.</li>
	</ol>
    <t>The state maintained along the path, path depends on whether the request is traversing the portion of the network where the locally-scoped locally scoped name is not routable, is routable. In this case, the forwarding can be based entirely on the routable prefix along with locally scoped name. However, where a portion of the locally-scoped prefix. Within path lies outside the network region that where the locally-scoped prefix locally scoped name is routable, the state is based only on it. To ensure that the generated replies
	reach the ping client, the border forwarder router has also to rewrite the name of a reply and prepend the routable prefix of the corresponding echo request.</t> request to ensure that the generated replies will reach the client.</t>
    </section>
    <section numbered="true" toc="default">
      <name>Security Considerations</name>
      <t>A reflection attack could be mounted by a compromised forwarder in the case of an echo reply Echo Reply with the CCNx packet format
      if that forwarder includes in the reply the name of a victim forwarder.
      This could convince a client to direct the future administrative traffic
      towards the victim. To foil such reflection attacks, the forwarder that generates a reply
      must sign the name included in the payload. In this way, the client is able to verify that the
      included name is legitimate and refers to the forwarder that generated the reply.
      Alternatively, the forwarder could include in the reply payload their routable
      prefix(es) encoded as a signed NDN Link Object <xref target="SNAMP" format="default"/>.</t>

      <t>Interest flooding attack amplification is possible in the case of the second approach to deal for dealing
      with locally-scoped locally scoped namespaces as described in <xref target="local" format="default"/>. To eliminate such amplification,
      a border forwarder will have to maintain extra state in order to prepend the correct routable prefix
      to the name of an outgoing reply, since the forwarder might be attached to
      multiple network regions (reachable under different prefixes) or a network region attached to this
      forwarder might be reachable under multiple routable prefixes.</t>

                        <t>Another example of an attack could be the ICN equivalent of port knocking, where an attacker
                                tries to discover certain forwarder implementations for the purpose of exploiting potential vulnerabilities.</t>
    </section>

        <section anchor="IANA" numbered="true" toc="default"><name>IANA Considerations</name>
                <t>IANA will assign has assigned 0x05 to "PT_ECHO_REQUEST" and 0x06 to "PT_ECHO_REPLY" in the CCNx "CCNx Packet Types Types" registry established by <xref target="RFC8609"/>.</t>

                <t>IANA will assign has assigned 0x0003 to "T_NONCE" in the "CCNx Name Segment Type IANA Registry for CCNx Types" registry established by <xref target="RFC8609"/>.</t>

                <t> IANA will create an "Echo has created a new registry called "CCNx Echo Reply Code" registry. Codes". The registration procedure is
  Specification Required <xref target="RFC8126"/>. In this registry, IANA will assign has assigned 0x01 to "T_ECHO_RETURN_FORWARDER", 0x02 to "T_ECHO_RETURN_APPLICATION", and 0x03 to "T_ECHO_RETURN_OBJECT" in the "Echo Reply Code" registry. </t>
		</section>

    <section anchor="Acknowledgements" numbered="true" toc="default">
      <name>Acknowledgements</name>
      <t>The authors would like to thank Mark Stapp for the fruitful discussion on the objectives
       of the ICN ping protocol.</t> "T_ECHO_RETURN_OBJECT".</t>
                </section>
  </middle>

<back>

  <references><name>References</name>
    <references><name>Normative References</name>
        <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.2119.xml"/> href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.2119.xml"/>
        <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.8174.xml"/> href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.8174.xml"/>
        <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.8569.xml"/> href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.8569.xml"/>
        <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.8609.xml"/> href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.8609.xml"/>
        <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.8793.xml"/> href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.8793.xml"/>
    </references>

    <references><name>Informative References</name>
        <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.9344.xml"/> href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.8126.xml"/>
        <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.4648.xml"/> href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.9344.xml"/>
        <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml3/reference.I-D.irtf-icnrg-pathsteering.xml"/> href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.4648.xml"/>

<!-- draft-irtf-icnrg-pathsteering (RFC-to-be 9531)
 "Long way" to fix author initials -->
<reference anchor="RFC9531" target="https://www.rfc-editor.org/info/rfc9531">
  <front>
    <title>Path Steering in Content-Centric Networking (CCNx) and Named Data
Networking (NDN)</title>
    <author fullname="Ilya Moiseenko" initials="I." surname="Moiseenko">
      <organization>Apple, Inc.</organization>
    </author>
    <author fullname="David R. Oran" initials="D." surname="Oran">
      <organization>Network Systems Research and Design</organization>
    </author>
    <date month="March" year="2024"/>
  </front>
  <seriesInfo name="RFC" value="9531"/>
  <seriesInfo name="DOI" value="10.17487/RFC9531"/>
</reference>

        <reference anchor="NDNTLV" target="https://named-data.net/doc/NDN-packet-spec/current/">
          <front>
            <title>NDN Packet Format Specification.</title>
            <author surname="NDN Project Team">
              <organization/> Specification</title>
            <author>
              <organization>NDN project team</organization>
            </author>
            <date year="2021"/> month="February" year="2024"/>
          </front>
        </reference>

        <reference anchor="SNAMP"> anchor="SNAMP" target="https://ieeexplore.ieee.org/abstract/document/7179398">
          <front>
            <title>SNAMP: Secure namespace mapping to scale NDN forwarding</title>
            <author initials="A" fullname="Alexander Afanasyev" surname="Afanasyev">
              <organization/>
            </author>
            <author surname="et al"> initials="C" fullname="Cheng Yi" surname="Yi">
              <organization/>
            </author>
            <author initials="L" fullname="Lan Wang" surname="Wang">
              <organization/>
            </author>
            <author initials="B" fullname="Beichuan Zhang" surname="Zhang">
              <organization/>
            </author>
            <author initials="L" fullname="Lixia Zhang" surname="Zhang">
              <organization/>
            </author>
            <date month="April" year="2015"/>
          </front>
          <refcontent>2015 IEEE Conference on Computer Communications Workshops (INFOCOM WKSHPS), Hong Kong, China, pp. 281-286</refcontent>
         <seriesInfo name="DOI" value="10.1109/INFCOMW.2015.7179398"/>
        </reference>

        <reference anchor="PATHSTEERING"> anchor="PATHSTEERING" target="https://dl.acm.org/doi/10.1145/3125719.3125721">
          <front>
            <title>Path switching in content centric and named data networks</title>
            <author initials="I" surname="Moiseenko">
              <organization/>
            </author>
            <author initials="D" surname="Oran">
              <organization/>
            </author>
            <date month="September" year="2017"/>
          </front>
          <refcontent>in
          <refcontent>ICN '17: Proceedings of the 4th ACM Conference on Information-Centric Networking</refcontent> Networking, pp. 66-76</refcontent>
         <seriesInfo name="DOI" value="10.1145/3125719.3125721"/>
        </reference>

        <reference anchor="REALTIME"> anchor="REALTIME" target="https://ieeexplore.ieee.org/document/8605992">
          <front>
            <title>Real-Time Data Retrieval in Named Data Networking</title>
            <author initials="S" surname="Mastorakis">
              <organization/>
            </author>
            <author initials="P" surname="Gusev">
              <organization/>
            </author>
            <author initials="A" surname="Afanasyev">
              <organization/>
            </author>
            <author initials="L" surname="Zhang">
              <organization/>
            </author>
            <date year="2017"/> month="August" year="2018"/>
          </front>
          <refcontent>in Proceedings of the
          <refcontent>2018 1st IEEE International Conference on Hot Topics in Information-Centric Networking</refcontent> Networking (HotICN), Shenzhen, China, pp. 61-66</refcontent>
         <seriesInfo name="DOI" value="10.1109/HOTICN.2018.8605992"/>
        </reference>

        <reference anchor="NDNLPv2" target="https://redmine.named-data.net/projects/nfd/wiki/NDNLPv2">
           <front>
             <title>Named
             <title>NDNLPv2: Named Data Networking Link Adaptation Protocol v2</title>
             <author surname="NDN team"/>
             <date>various</date>
             <author>
              <organization>NDN team</organization>
             </author>
             <date year="2023" month="February"></date>
           </front>
        </reference>
    </references>
  </references>

    <section anchor="app-additional" numbered="true" toc="default">
      <name>Ping Client Application (Consumer) Operation</name>
      <t>This section is an informative appendix regarding the proposed ping client
      operation.</t>
      <t>The ping client application is responsible for generating echo requests Echo Requests for
     prefixes provided by users.</t>
      <t>When generating a series of echo requests Echo Requests for a specific name, the first
       echo request
       Echo Request will typically not include a Path label Label TLV, since no TLV value
       is known. After an echo reply Echo Reply containing a Path label Label TLV is received, each
       subsequent echo request Echo Request can include the received path steering Path Steering value
       in the Path label Label header TLV to drive the requests towards a common path
       as part of checking network performance. To discover more paths, a client can
       omit the path steering Path Steering TLV in future requests. Moreover, for each new ping echo
       request, Ping Echo
       Request, the client has to generate a new nonce and record the time that the
       request was expressed. It will also set the lifetime of an echo request, Echo Request,
       which will have identical semantics identical to the lifetime of an Interest.</t>
      <t>Further, the client application might not wish to receive echo replies Echo Replies due to
      CS hits. A mechanism to achieve that in CCNx would be to use a Content Object Hash
      Restriction TLV with a value of 0 in the payload of an echo request Echo Request message. In NDN,
      the exclude filter selector can be used.</t>
      <t>When it receives an echo reply, Echo Reply, the client would typically match the reply to a sent
      request and compute the round-trip time RTT of the request. It should parse the
      Path label Label value and decode the reply's payload to parse
      the
      the sender's name and signature. The client should verify that both
      the received message and the forwarder's name have been signed by the
      key of the forwarder, whose name is included in the payload of the reply (by
      fetching this forwarder's public key and verifying the contained signature). The client
      can also decode the Echo Reply Code TLV to understand the condition that triggered
      the generation of the reply.</t>
      <t>In the case that an echo reply Echo Reply is not received for a request within a certain
      time interval (lifetime of the request), the client should time-out time out and send a new
      request with a new nonce value up to some maximum number of requests
      to be sent specified by the user.</t>
    </section>

    <!-- Change Log
v03 2021-10-25 DRO   Update references
v08 2023-04-20 DRO	 Keepalive + update Spiros' author info
 -->
    <section anchor="Acknowledgements" numbered="false" toc="default">
      <name>Acknowledgements</name>
      <t>The authors would like to thank <contact fullname="Mark Stapp"/> for the fruitful discussion on the objectives
       of the ICN Ping protocol.</t>
    </section>
  </back>
</rfc>