rfc9798.original   rfc9798.txt 
Internet Engineering Task Force V. Govindan Internet Engineering Task Force (IETF) V. Govindan
Internet-Draft S. Venaas Request for Comments: 9798 S. Venaas
Updates: 8059 (if approved) Cisco Updates: 8059 Cisco
Intended status: Experimental 21 February 2025 Category: Experimental May 2025
Expires: 25 August 2025 ISSN: 2070-1721
PIM Join/Prune Attributes for LISP Environments using Underlay Multicast PIM Join/Prune Attributes for Locator/ID Separation Protocol (LISP)
draft-ietf-pim-jp-extensions-lisp-09 Environments Using Underlay Multicast
Abstract Abstract
This document specifies an update to the PIM Receiver RLOC Join/Prune This document specifies an update to the PIM Receiver RLOC Join/Prune
attribute that supports the construction of multicast distribution attribute that supports the construction of multicast distribution
trees where the source and receivers are located in different trees where the source and receivers are located in different
Locator/ID Separation Protocol (LISP) sites and are connected using Locator/ID Separation Protocol (LISP) sites and are connected using
underlay IP Multicast. This attribute allows the receiver site to underlay IP Multicast. This attribute allows the receiver site to
signal the underlay multicast group to the control plane of the root signal the underlay multicast group to the control plane of the root
Ingress Tunnel Router (ITR). This document updates RFC 8059. Ingress Tunnel Router (ITR). This document updates RFC 8059.
Status of This Memo Status of This Memo
This Internet-Draft is submitted in full conformance with the This document is not an Internet Standards Track specification; it is
provisions of BCP 78 and BCP 79. published for examination, experimental implementation, and
evaluation.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months This document defines an Experimental Protocol for the Internet
and may be updated, replaced, or obsoleted by other documents at any community. This document is a product of the Internet Engineering
time. It is inappropriate to use Internet-Drafts as reference Task Force (IETF). It represents the consensus of the IETF
material or to cite them other than as "work in progress." community. It has received public review and has been approved for
publication by the Internet Engineering Steering Group (IESG). Not
all documents approved by the IESG are candidates for any level of
Internet Standard; see Section 2 of RFC 7841.
This Internet-Draft will expire on 25 August 2025. Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
https://www.rfc-editor.org/info/rfc9798.
Copyright Notice Copyright Notice
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Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1. Introduction
1.1. Requirements Language . . . . . . . . . . . . . . . . . . 3 1.1. Requirements Language
2. The case for extending the Received ETR RLOC Attribute of RFC 2. The Case for Extending the Received ETR RLOC Attribute of RFC
8059 . . . . . . . . . . . . . . . . . . . . . . . . . . 3 8059
2.1. Flexible mapping of overlay to underlay group ranges: . . 3 2.1. Flexible Mapping of Overlay to Underlay Group Ranges
2.2. Multicast Address Range constraints: . . . . . . . . . . 3 2.2. Multicast Address Range Constraints
3. Updates to RFC 8059 . . . . . . . . . . . . . . . . . . . . . 4 3. Updates to RFC 8059
3.1. Scope . . . . . . . . . . . . . . . . . . . . . . . . . . 4 3.1. Scope
3.2. Receiver ETR RLOC Attribute . . . . . . . . . . . . . . . 4 3.2. Receiver ETR RLOC Attribute
3.3. Using the Receiver RLOC Attribute . . . . . . . . . . . . 4 3.3. Using the Receiver RLOC Attribute
4. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 5 4. IANA Considerations
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5 5. Security Considerations
6. Security Considerations . . . . . . . . . . . . . . . . . . . 5 6. Normative References
7. Normative References . . . . . . . . . . . . . . . . . . . . 6 Acknowledgements
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 6 Authors' Addresses
1. Introduction 1. Introduction
The construction of multicast distribution trees where the root and The construction of multicast distribution trees where the root and
receivers are located in different LISP sites [RFC9300] is defined in receivers are located in different LISP sites [RFC9300] is defined in
[RFC6831]. [RFC6831].
[RFC6831] specifies that (root-EID, G) data packets are to be LISP- [RFC6831] specifies that (root-EID, G) data packets are to be LISP-
encapsulated into (root-RLOC, G) multicast packets. [RFC8059] encapsulated into (root-RLOC, G) multicast packets. [RFC8059]
defines PIM Join/Prune attribute extensions to construct multicast defines PIM Join/Prune attribute extensions to construct multicast
distribution trees. Please refer to Section 3 of [RFC6831] for the distribution trees. Please refer to Section 3 of [RFC6831] for the
definition of the terms EID and RLOC. We use the term root-EID or definition of the terms Endpoint ID (EID) and Routing Locator (RLOC).
root-RLOC to refer to the source of the multicast tree rooted at the We use the term root-EID or root-RLOC to refer to the source of the
EID or RLOC. This document extends the Receiver ETR RLOC PIM Join/ multicast tree rooted at the EID or RLOC. This document extends the
Prune attribute [RFC8059] to facilitate the construction of underlay Receiver ETR RLOC PIM Join/Prune attribute [RFC8059] to facilitate
multicast trees for (root-RLOC, G). the construction of underlay multicast trees for (root-RLOC, G).
Specifically, the assignment of the underlay multicast group needs to Specifically, the assignment of the underlay multicast group needs to
be done in consonance with the downstream xTR nodes needed to avoid be done in consonance with the downstream Tunnel Router (xTR) nodes
unnecessary replication or traffic hairpinning. needed to avoid unnecessary replication or traffic hairpinning.
Since the Receiver RLOC Attribute defined in [RFC8059] only addresses Since the Receiver RLOC Attribute defined in [RFC8059] only addresses
the Ingress Replication case, an extension of the scope of that PIM the Ingress Replication case, this document extends the scope of that
Join/Prune attribute is defined by this draft to include scenarios PIM Join/Prune attribute to include scenarios where the underlay uses
where the underlay uses Multicast transport. The scope extension Multicast transport. The scope extension complies with the base
proposed here complies with the base specification [RFC5384]. specification [RFC5384].
This document uses terminology defined in [RFC9300], such as EID, This document uses terminology defined in [RFC9300], such as EID,
RLOC, ITR, and ETR. RLOC, ITR, and ETR.
1.1. Requirements Language 1.1. Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in BCP "OPTIONAL" in this document are to be interpreted as described in
14 [RFC2119] [RFC8174] when, and only when, they appear in all BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here. capitals, as shown here.
2. The case for extending the Received ETR RLOC Attribute of RFC 8059 2. The Case for Extending the Received ETR RLOC Attribute of RFC 8059
When LISP based Multicast trees are constructed using IP Multicast in When LISP-based Multicast trees are constructed using IP Multicast in
the underlay, the mapping between the overlay group address and the the underlay, the mapping between the overlay group address and the
underlay group address becomes a crucial engineering decision: underlay group address becomes a crucial engineering decision.
2.1. Flexible mapping of overlay to underlay group ranges: 2.1. Flexible Mapping of Overlay to Underlay Group Ranges
Three distinct types of overlay to underlay group mappings are Three distinct types of overlay to underlay group mappings are
possible: Many to one mapping: Many (root-EID, G) flows originating possible:
from an RLOC can be mapped to a single underlay multicast (root-RLOC,
G-u) flow. One to many mapping: Conversely a single same overlay
flow can be mapped to two or more flows, e.g., (root-RLOC, G-u1) and
(root-RLOC, G-u2) to cater to the requirements of downstream xTR
nodes. One to one mapping: Every (root-EID, G) flow is mapped to a
unique (root-RLOC, G-u) flow.
2.2. Multicast Address Range constraints: * 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 mapping: Conversely a single same overlay flow can be
mapped to two or more flows -- e.g., (root-RLOC, G-u1) and (root-
RLOC, G-u2) -- to cater to the requirements of downstream xTR
nodes.
* One-to-one mapping: Every (root-EID, G) flow is mapped to a unique
(root-RLOC, G-u) flow.
2.2. Multicast Address Range Constraints
Under certain conditions, different subsets of xTRs subscribing to Under certain conditions, different subsets of xTRs subscribing to
the same overlay multicast stream may be constrained to use distinct the same overlay multicast stream may be constrained to use distinct
underlay multicast mapping ranges. underlay multicast mapping ranges.
This introduces a trade-off between replication overhead and the This introduces a trade-off between replication overhead and the
flexibility of address range assignment, which may be necessary in flexibility of address range assignment, which may be necessary in
specific use-cases like Proxy Tunnel Routers or when using nodes with specific use cases like Proxy Tunnel Routers or when using nodes with
limited hardware resources as explained below: limited hardware resources as explained below.
Inter-site Proxy Tunnel Routers (PxTR): Inter-site Proxy Tunnel Routers (PxTR):
When multiple LISP sites are interconnected through a LISP-based When multiple LISP sites are interconnected through a LISP-based
transit, the site border node (PxTR) connects the site-facing transit, the site border node (PxTR) connects the site-facing
interfaces with the external LISP core. In such cases, different interfaces with the external LISP core. In such cases, different
ranges of multicast group addresses may be used for constructing ranges of multicast group addresses may be used for constructing
(S-RLOC, G) trees within the LISP site and in the external LISP (S-RLOC, G) trees within the LISP site and in the external LISP
core. This distinction is desirable for various operational core. This distinction is desirable for various operational
reasons reasons.
Hardware resource restrictions: Hardware resource restrictions:
Platform limitations may necessitate engineering decisions to Platform limitations may necessitate engineering decisions to
restrict multicast address ranges in the underlay due to hardware restrict multicast address ranges in the underlay due to hardware
resource constraints. resource constraints.
3. Updates to RFC 8059 3. Updates to RFC 8059
3.1. Scope 3.1. Scope
No changes are proposed to the syntax or semantics of the Transport No changes are proposed to the syntax or semantics of the Transport
Attribute defined in RFC 8059 [RFC8059]. Attribute defined in [RFC8059].
The scope of the updates to RFC 8059 [RFC8059] is limited to the case The scope of the updates to [RFC8059] is limited to the case where
where the "Transport" field of the Transport Attribute is set to zero the "Transport" field of the Transport Attribute is set to zero
(Multicast) only. (Multicast) only.
3.2. Receiver ETR RLOC Attribute 3.2. Receiver ETR RLOC Attribute
The definition of the "Receiver RLOC" field of the Receiver ETR RLOC The definition of the "Receiver RLOC" field of the Receiver ETR RLOC
attribute RFC 8059 [RFC8059] is updated as follows: attribute [RFC8059] is updated as follows:
Receiver RLOC: | Receiver RLOC:
The RLOC address on which the receiver ETR wishes to receive the | The RLOC address on which the receiver ETR wishes to receive
encapsulated flow. A unicast IP Receiver RLOC address is used for | the encapsulated flow. A unicast IP Receiver RLOC address is
unicast-encapsulated flows. Alternately, a multicast IP Receiver | used for unicast-encapsulated flows. Alternately, a multicast
RLOC address is used for for multicast-encapsulated flows. A | IP Receiver RLOC address is used for for multicast-encapsulated
multicast IP address MUST be used only when the underlay network of | flows. A multicast IP address MUST be used only when the
the LISP core supports IP Multicast transport. | underlay network of the LISP core supports IP Multicast
| transport.
The definitions of the other fields of the Receiver ETR RLOC The definitions of the other fields of the Receiver ETR RLOC
Attribute remain unchanged. Attribute remain unchanged.
When the ITR needs to track the list of ETRs from which the PIM joins When the ITR needs to track the list of ETRs from which the PIM joins
are received, the ITR MUST use the source IP address field of the are received, the ITR MUST use the source IP address field of the
incoming PIM Join/Prune message. The source IP address of the PIM incoming PIM Join/Prune message. The source IP address of the PIM
Join/Prune MUST be an ETR RLOC IP address. Join/Prune MUST be an ETR RLOC IP address.
3.3. Using the Receiver RLOC Attribute 3.3. Using the Receiver RLOC Attribute
When the ETR determines to use the multicast underlay: When the ETR determines to use the multicast underlay:
* It chooses an underlay multicast group that it can join. This is * It chooses an underlay multicast group that it can join. This is
a matter of local decision, beyond the scope of this document. a matter of local decision, which is beyond the scope of this
document.
* It identifies the upstream LISP site where the underlay multicast * It identifies the upstream LISP site where the underlay multicast
tree needs to be rooted. tree needs to be rooted.
* It constructs the PIM Join/Prune message as specified in RFC 8059 * It constructs the PIM Join/Prune message as specified in
[RFC8059]. Only the Receiver RLOC attribute is encoded as above. [RFC8059]. Only the Receiver RLOC attribute is encoded as above.
When the ITR receives a PIM Join/Prune message: When the ITR receives a PIM Join/Prune message:
* It allocates a new entry in the OutgoingInterfaceList RFC 6831 * It allocates a new entry in the OutgoingInterfaceList [RFC6831]
[RFC6831] for every unique underlay multicast mapping. for every unique underlay multicast mapping.
* The ITR MAY apply local policy to perform any kind of rate- * The ITR MAY apply local policy to perform any kind of rate-
limiting on the number of copies it needs to make in the underlay. limiting on the number of copies it needs to make in the underlay.
Such actions are beyond the scope of this document. Such actions are beyond the scope of this document.
4. Acknowledgements 4. IANA Considerations
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.
5. IANA Considerations
No new requests to IANA. This document has no IANA actions.
6. Security Considerations 5. Security Considerations
An attack vector arises where an attacker sends numerous PIM Join An attack vector arises where an attacker sends numerous PIM Join
messages with different group addresses. This could interfere with messages with different group addresses. This could interfere with
legitimate multicast traffic if the group addresses overlap. legitimate multicast traffic if the group addresses overlap.
Additionally, resource exhaustion may occur if replication is Additionally, resource exhaustion may occur if replication is
requested for a large number of groups, potentially resulting in requested for a large number of groups, potentially resulting in
significant resource consumption. To mitigate these risks, PIM significant resource consumption. To mitigate these risks, PIM
authentication mechanisms RFC 5796 [RFC5796] could be employed to authentication mechanisms [RFC5796] could be employed to validate
validate join requests. Furthermore, implementations may consider join requests. Furthermore, implementations may consider explicit
explicit tracking mechanisms to manage joins more effectively. tracking mechanisms to manage joins more effectively. Configurable
Configurable controls could be introduced, allowing for a maximum controls could be introduced, allowing for a maximum permissible
permissible number of groups for each ETR RLOC used as the source of number of groups for each ETR RLOC used as the source of overlay
overlay joins. These controls would limit the impact of such attacks joins. These controls would limit the impact of such attacks and
and ensure that resource allocation is managed appropriately. ensure that resource allocation is managed appropriately.
7. Normative References 6. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997, DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>. <https://www.rfc-editor.org/info/rfc2119>.
[RFC5384] Boers, A., Wijnands, I., and E. Rosen, "The Protocol [RFC5384] Boers, A., Wijnands, I., and E. Rosen, "The Protocol
Independent Multicast (PIM) Join Attribute Format", Independent Multicast (PIM) Join Attribute Format",
RFC 5384, DOI 10.17487/RFC5384, November 2008, RFC 5384, DOI 10.17487/RFC5384, November 2008,
<https://www.rfc-editor.org/info/rfc5384>. <https://www.rfc-editor.org/info/rfc5384>.
skipping to change at page 6, line 42 skipping to change at line 270
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>. May 2017, <https://www.rfc-editor.org/info/rfc8174>.
[RFC9300] Farinacci, D., Fuller, V., Meyer, D., Lewis, D., and A. [RFC9300] Farinacci, D., Fuller, V., Meyer, D., Lewis, D., and A.
Cabellos, Ed., "The Locator/ID Separation Protocol Cabellos, Ed., "The Locator/ID Separation Protocol
(LISP)", RFC 9300, DOI 10.17487/RFC9300, October 2022, (LISP)", RFC 9300, DOI 10.17487/RFC9300, October 2022,
<https://www.rfc-editor.org/info/rfc9300>. <https://www.rfc-editor.org/info/rfc9300>.
Acknowledgements
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.
Authors' Addresses Authors' Addresses
Vengada Prasad Govindan Vengada Prasad Govindan
Cisco Cisco
Email: venggovi@cisco.com Email: venggovi@cisco.com
Stig Venaas Stig Venaas
Cisco Cisco
Email: svenaas@cisco.com Email: svenaas@cisco.com
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