<?xml version='1.0' encoding='utf-8'?> encoding='UTF-8'?>

<!-- [rfced] Because this document updates RFC 8059, please
review the errata reported for RFC 8059
(https://www.rfc-editor.org/errata_search.php?rfc=8059).  We do not believe any are applicable to this document, but we would appreciate confirmation that this is correct.
-->

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<rfc xmlns:xi="http://www.w3.org/2001/XInclude" category="exp" docName="draft-ietf-pim-jp-extensions-lisp-09" number="9798" consensus="true" ipr="trust200902" obsoletes="" updates="8059" submissionType="IETF" xml:lang="en" tocInclude="true" tocDepth="4" symRefs="true" sortRefs="true" version="3">

 <front>
   <title abbrev="PIM Join Attributes for LISP Mcast"> PIM Multicast">PIM Join/Prune Attributes for LISP Locator/ID Separation Protocol (LISP) Environments using Using Underlay Multicast
   </title> Multicast</title>
    <seriesInfo name="Internet-Draft" value="draft-ietf-pim-jp-extensions-lisp-09"/> name="RFC" value="9798"/>

   <author fullname="Vengada Prasad Govindan" initials="V" surname="Govindan">
      <organization>Cisco</organization>
      <address>
        <email>venggovi@cisco.com</email>
     </address>
    </author>

   <author fullname="Stig Venaas" initials="S" surname="Venaas">
      <organization>Cisco</organization>
      <address>
        <email>svenaas@cisco.com</email>
     </address>
    </author>

    <date year="2025"/> year="2025" month="May"/>

    <area>RTG</area>
    <workgroup>pim</workgroup>

<!-- If the month and year are both specified and are the current ones, xml2rfc will fill
        in the current day for you. If only the current year is specified, xml2rfc will fill [rfced] Please insert any keywords (beyond those that appear in
the current day and month for you. If the year is not the current one, it is
	 necessary to specify at least a month (xml2rfc assumes day="1" if not specified for the
	 purpose of calculating the expiry date).  With drafts it is normally sufficient to
	 specify just the year. -->

   <!-- Meta-data Declarations -->

   <area>Routing</area>
    <workgroup>Internet Engineering Task Force</workgroup>
    <!-- WG name at the upperleft corner of the doc,
        IETF is fine title) for individual submissions.
	 If this element is not present, the default is "Network Working Group",
        which is used by the RFC Editor as a nod to the history of the IETF. -->

   <keyword>template</keyword>
    <!-- Keywords will be incorporated into HTML output
        files in a meta tag but they have no effect use on text or nroff
        output. If you submit your draft to the RFC Editor, the
        keywords will be used for the search engine. https://www.rfc-editor.org/search. -->

<keyword>example</keyword>

   <abstract>
	   <t>This document specifies an update to the PIM Receiver RLOC Join/Prune attribute that supports the
   construction of multicast distribution trees where the source and
   receivers are located in different Locator/ID Separation Protocol
   (LISP) sites and are connected using underlay IP Multicast.  This attribute allows the receiver site to signal
   the underlay multicast group to the control plane of the root Ingress Tunnel Router (ITR). This document updates RFC 8059.

     </t>
    </abstract>
  </front>
  <middle>
    <section numbered="true" toc="default">
      <name>Introduction</name>
      <t>
	      The construction of multicast distribution trees where the root and
   receivers are located in different LISP sites <xref target="RFC9300" format="default"/> is defined in
    <xref target="RFC6831" format="default"/>.</t>
	    <t>

<!-- [rfced] [RFC6831] appears to use the terms "(S-EID,G)" and "(S-RLOC,G)" rather
than "(root-EID, G)" and "(root-RLOC, G)". This is clarified later in the paragraph, but perhaps the sentences should be closer together and the original term defined in RFC 6831 should be noted first.

Original:
   [RFC6831] specifies that (root-EID, G) data packets are to be LISP-
   encapsulated into (root-RLOC, G) multicast packets. ... We use the term
   root-EID or root-RLOC to refer to the source of the multicast tree
   rooted at the EID or RLOC.

Perhaps:
   [RFC6831] specifies that (EID, G) data packets are to be LISP-
   encapsulated into (RLOC, G) multicast packets. In this document,
   we use the term root-EID or root-RLOC to refer to the source
   of the multicast tree rooted at the EID or RLOC. ...
-->
<!-- [rfced] Seemingly, the text points readers to RFCs 6831 and 9300 for definitions of EID and RLOC.  Please review.

Original (both from the Introduction):
   Please refer to Section 3 of [RFC6831] for the
   definition of the terms EID and RLOC.

   ...

   This document uses terminology defined in [RFC9300], such as EID,
   RLOC, ITR, and ETR.
-->

	<xref target="RFC6831" format="default"/> specifies that (root-EID, G) data packets are to be LISP-
		encapsulated LISP-encapsulated into (root-RLOC, G) multicast packets. <xref target="RFC8059" format="default"/>
                defines PIM Join/Prune attribute extensions to construct multicast distribution trees.
		Please refer to Section 3 of <xref target="RFC6831" format="default"/> sectionFormat="of" section="3"/> for the definition of the terms EID Endpoint ID (EID) and RLOC. Routing Locator (RLOC). We use the term root-EID or root-RLOC to refer to the source of the multicast tree rooted at the EID or RLOC.
	This document extends the Receiver ETR RLOC PIM Join/Prune attribute <xref target="RFC8059" format="default"/>
                to facilitate the
		construction of underlay multicast trees for (root-RLOC, G).
	    </t>
	    <t>
		    Specifically, the assignment of the underlay multicast group needs to be done in consonance with
		    the downstream xTR Tunnel Router (xTR) nodes needed to avoid unnecessary replication or traffic hairpinning.
	    </t>
	    <t> Since the Receiver RLOC Attribute defined in <xref target="RFC8059" format="default"/> only
		    addresses the Ingress Replication case, an extension of this document extends the scope of that PIM Join/Prune attribute is defined by this draft to include
		    scenarios where the underlay uses Multicast transport. The scope extension proposed here complies
		    with the base specification <xref target="RFC5384" format="default"/>.
           </t>
      <t>This document uses terminology defined in <xref target="RFC9300" format="default"/>, such as EID,
   RLOC, ITR, and ETR.  </t>

         <section>

        <name>Requirements Language</name>

        <t>The

        <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 BCP&nbsp;14 <xref target="RFC2119"/> <xref
    target="RFC8174"/> when, and only when, they appear in all capitals, as
    shown here.</t> here.
        </t>
      </section>

    </section>

    <section title="The case

    <section>
      <name>The Case for extending Extending the Received ETR RLOC Attribute of RFC 8059"> 8059</name>
	    <t>When LISP based LISP-based Multicast trees are constructed using IP Multicast in the underlay, the mapping between
		    the overlay group address and the underlay group address becomes a crucial engineering decision: decision.

    </t>
    <section title="Flexible mapping
    <section>
      <name>Flexible Mapping of overlay Overlay to underlay group ranges:"> Underlay Group Ranges</name>
		 <t> Three distinct types of overlay to underlay group mappings are possible: Many to one </t>
<ul>
<li>Many-to-one mapping: Many (root-EID, G) flows originating from an RLOC can be mapped to a single underlay multicast (root-RLOC, G-u) flow.  One to many  </li>
<li>One-to-many mapping: Conversely  a single same overlay flow can be mapped to two or more flows, flows -- e.g., (root-RLOC, G-u1) and (root-RLOC, G-u2) -- to cater to the requirements of downstream xTR nodes.  One to one nodes.</li>
<li>One-to-one mapping: Every (root-EID, G) flow is mapped to a unique (root-RLOC, G-u) flow. </t> </li>
</ul>
	 </section>

		 <section title="Multicast

	 <section>
	   <name>Multicast Address Range constraints:"> Constraints</name>
			 <t>	    Under certain conditions, different subsets of xTRs subscribing to the same overlay
				 multicast stream may be constrained to use distinct underlay multicast mapping ranges. </t>
			 <t>
                    This introduces a trade-off between replication overhead and the flexibility of
				 address range assignment, which may be necessary in specific use-cases use cases like Proxy Tunnel Routers or when using nodes with limited hardware resources as explained below: below. </t>
         <dl newline="true" spacing="normal" indent="2">
		 <dt>
<!-- [rfced] Is (PxTR) the same as the site border node?

Original:
   Inter-site Proxy Tunnel Routers (PxTR):</dt>
        <dd> (PxTR):
     When multiple LISP sites are interconnected through a LISP-based
     transit, the site border node (PxTR) connects the site-facing
     interfaces with the external LISP core.

Perhaps:
   Inter-site Proxy Tunnel Routers (PxTR):
     When multiple LISP sites are interconnected through a LISP-based
     transit, the site border node (i.e., PxTR) connects the site-facing
     interfaces with the external LISP core.
-->
	   <dt>Inter-site Proxy Tunnel Routers (PxTR):</dt>
           <dd>When multiple LISP sites are interconnected through a
           LISP-based transit, the site border node (PxTR) connects the
           site-facing interfaces with the external LISP core. In such cases,
           different ranges of multicast group addresses may be used for
           constructing (S-RLOC, G) trees within the LISP site and in the
           external LISP core. This distinction is desirable for various
           operational reasons reasons.
         </dd>
	 <dt> Hardware
	 <dt>Hardware resource restrictions:</dt>
          <dd> Platform
         <dd>Platform limitations may necessitate engineering decisions to
         restrict multicast address ranges in the underlay due to hardware
         resource constraints. </dd>
         </dl>

	 </section>
    </section>

<section title="Updates

<section>
  <name>Updates to RFC 8059">
    <section title="Scope"> 8059</name>
    <section>
      <name>Scope</name>
      <t>No changes are proposed to the syntax or semantics of the Transport
      Attribute defined in <xref target="RFC8059" format="default">RFC 8059</xref>.</t> format="default"/>.</t>
      <t> The scope of the updates to <xref target="RFC8059" format="default">RFC 8059</xref>
      format="default"/> is limited to the case where the "Transport" field of
      the Transport Attribute is set to zero (Multicast) only. </t>
    </section>
    <section title="Receiver
    <section>
      <name>Receiver ETR RLOC Attribute</name>
<!-- [rfced] For clarity, we suggest including a section number (at minimum) and/or the text being replaced.  For example:

Original:
   The definition of the "Receiver RLOC" field of the Receiver ETR RLOC Attribute">
   attribute RFC 8059 [RFC8059] is updated as follows:

   Receiver RLOC:
    The RLOC address on which the receiver ETR wishes to receive the
    encapsulated flow.  A unicast IP Receiver RLOC address is used for
    unicast-encapsulated flows.  Alternately, a multicast IP Receiver
    RLOC address is used for for multicast-encapsulated flows.  A
    multicast IP address MUST be used only when the underlay network of
    the LISP core supports IP Multicast transport.

Suggested:
   The definition of the "Receiver RLOC" field of the Receiver ETR RLOC
   attribute (see Section 5.1 of [RFC8059]) is updated as follows:

OLD:
   Receiver RLOC:   The RLOC address on which the receiver ETR wishes to
      receiver the unicast-encapsulated flow.

NEW:
   Receiver RLOC:
    The RLOC address on which the receiver ETR wishes to receive the
    encapsulated flow.  A unicast IP Receiver RLOC address is used for
    unicast-encapsulated flows.  Alternately, a multicast IP Receiver
    RLOC address is used for multicast-encapsulated flows.  A
    multicast IP address MUST be used only when the underlay network of
    the LISP core supports IP Multicast transport.
-->

      <t>The definition of the "Receiver RLOC" field of the Receiver ETR RLOC
      attribute <xref target="RFC8059" format="default">RFC 8059</xref> format="default"/> is
      updated as follows:</t>
<blockquote>
         <dl newline="true" spacing="normal" indent="1"> spacing="normal">
	 <dt> Receiver RLOC:</dt>
          <dd> The RLOC address on which the receiver ETR wishes to receive the
           encapsulated flow. A unicast IP Receiver RLOC address is used for unicast-encapsulated flows.
           Alternately, a multicast IP Receiver RLOC address is used for for multicast-encapsulated flows.
           A multicast IP address MUST <bcp14>MUST</bcp14> be used only when the underlay network of the LISP core supports
           IP Multicast transport.</dd>
	 </dl>
</blockquote>
	 <t> The definitions of the other fields of the Receiver ETR RLOC Attribute remain unchanged. </t>
	 <t> When the ITR needs to track the list of ETRs from which the PIM joins are received, the ITR MUST <bcp14>MUST</bcp14> use the source IP address field of the incoming PIM Join/Prune message. The source IP address of the PIM Join/Prune MUST <bcp14>MUST</bcp14> be an ETR RLOC IP address.</t>
<!--
	%<t>The root ITR MUST also discard all affected Join/Prune sources if the Transport Attribute value is set to any value other than zero and the Address field of the Receiver RLOC contains a multicast IP address.  </t> -->
    </section>
<section title="Using
<section>
  <name>Using the Receiver RLOC Attribute"> Attribute</name>
	<t>When the ETR determines to use the multicast underlay:</t>
	<ul>
		<li>It chooses an underlay multicast group that it can join. This is a matter of local decision, which is beyond the scope of this document.</li>
		<li>It identifies the upstream LISP site where the underlay multicast tree needs to be rooted.</li>
		<li>It constructs the PIM Join/Prune message as specified in <xref target="RFC8059" format="default">RFC 8059</xref>. format="default"/>. Only the Receiver RLOC attribute is encoded as above. </li>
	</ul><t></t>
	<t>When the ITR receives a PIM Join/Prune message: </t>
	<ul>
<!-- [rfced] [RFC6831] uses the term "outgoing interface list" and "OIF-list"; we do not see use the term "OutgoingInterfaceList".  Please review.

Original:
   *  It allocates a new entry in the OutgoingInterfaceList RFC 6831
      [RFC6831] for every unique underlay multicast mapping.
-->
		<li>It allocates a new entry in the OutgoingInterfaceList <xref target="RFC6831" format="default">RFC 6831</xref> format="default"/>  for every unique underlay multicast mapping. </li>
		<li>The ITR MAY <bcp14>MAY</bcp14> apply local policy to perform any kind of rate-limiting on the number of copies it needs to make in the underlay. Such actions are beyond the scope of this document.</li>
	</ul><t></t>

</section>
</section>

   <!-- Possibly a 'Contributors' section ... -->

   <section anchor="Acknowledgements" numbered="true" toc="default">
      <name>Acknowledgements</name>
	   <t>
	   The authors would like to thank Dino Farinacci, Victor Moreno, Alvaro Retana, Aswin Kuppusami, Joe Clarke and Peter Yee for their valuable comments. The authors also thank Sankaralingam T and Amit Kumar for their contributions to the document. The authors thank Gunter van de Velde for his valuable comments.
	   </t>
   </section>

   <section anchor="IANA" numbered="true" toc="default">
      <name>IANA Considerations</name>
      <t>No new requests to IANA.</t>
<t>This document has no IANA actions.</t>
    </section>
    <section anchor="Security" numbered="true" toc="default">
      <name>Security Considerations</name>
      <t>
	      An attack vector arises where an attacker sends numerous PIM Join messages with different group addresses. This could interfere with legitimate multicast traffic if the group addresses overlap. Additionally, resource exhaustion may occur if replication is requested for a large number of groups, potentially resulting in significant resource consumption.
To mitigate these risks, PIM authentication mechanisms <xref target="RFC5796" format="default">RFC 5796</xref> format="default"/> could be employed to validate join requests. Furthermore, implementations may consider explicit tracking mechanisms to manage joins more effectively. Configurable controls could be introduced, allowing for a maximum permissible number of groups for each ETR RLOC used as the source of overlay joins. These controls would limit the impact of such attacks and ensure that resource allocation is managed appropriately.

     </t>
    </section>
  </middle>
  <!--  *****BACK MATTER ***** -->

 <back>
    <references>
      <name>Normative References</name>
      <xi:include href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.2119.xml"/>
      <xi:include href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.5384.xml"/>
      <xi:include href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.9300.xml"/>
      <xi:include href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.5796.xml"/>
      <xi:include href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.6831.xml"/>
      <xi:include href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.8059.xml"/>
      <xi:include href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.8174.xml"/>
    </references>

   <section anchor="Acknowledgements" numbered="false" toc="default">
      <name>Acknowledgements</name>
      <t>The authors would like to thank <contact fullname="Dino Farinacci"/>,
      <contact fullname="Victor Moreno"/>, <contact fullname="Alvaro
      Retana"/>, <contact fullname="Aswin Kuppusami"/>, <contact fullname="Joe
      Clarke"/>, and <contact fullname="Peter Yee"/> for their valuable
      comments. The authors also thank <contact fullname="Sankaralingam T"/>
      and <contact fullname="Amit Kumar"/> for their contributions to the
      document. The authors thank <contact fullname="Gunter Van de Velde"/>
      for his valuable comments.</t>
   </section>
<!-- References split into informative [rfced] Throughout the text, the following terminology appears to be used
inconsistently. Please review these occurrences and let us know if/how they
may be made consistent.

Multicast vs multicast

Note that we expanded the following abbreviations and normative let us know if any updates are required.

Routing Locator (RLOC)
Tunnel Router (xTR)
-->

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and use "ampersand character"RFC2629; here (as shown)
    2. simply use a PI "less than character"?rfc include="reference.RFC.2119.xml"?> here
       (for I-Ds: include="reference.I-D.narten-iana-considerations-rfc2434bis.xml")

    Both let us know if any changes are cited textually needed.  Updates of this nature typically
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    If you use the PI option, xml2rfc will, by default, try to find included files more precise language, which is helpful for readers.

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    directory particular, but this should
still be reviewed as the including file. You can also define the XML_LIBRARY environment variable
    with a value containing a set of directories to search.  These can be either in the local
    filing system or remote ones accessed by http (http://domain/dir/... ).-->

    <references title="Normative References">
      <?rfc include="reference.RFC.2119.xml" ?>
      <?rfc include="reference.RFC.5384.xml" ?>
      <?rfc include="reference.RFC.9300.xml" ?>
      <?rfc include="reference.RFC.5796.xml" ?>
      <?rfc include="reference.RFC.6831.xml" ?>
      <?rfc include="reference.RFC.8059.xml" ?>
      <?rfc include="reference.RFC.8174.xml" ?>
    </references>
    <!-- Change Log

v00 2020-12-10  GVP   Initial version best practice.
-->

 </back>
</rfc>