wdiff rfc9860.original rfc9860.txt

PIM Working Group

Internet Engineering Task Force (IETF) Y. Liu
Internet-Draft
Request for Comments: 9860 China Mobile
Intended status:
Category: Informational M. McBride
Expires: 9 October 2025
ISSN: 2070-1721 Futurewei
Z. Zhang
ZTE
J. Xie
Huawei
C. Lin
New H3C Technologies
7 April
September 2025

Multicast-only

Multicast-Only Fast Reroute (MoFRR) Based on Topology Independent Loop-free Loop-
Free Alternate (TI-LFA) Fast Reroute
draft-ietf-pim-mofrr-tilfa-14

Abstract

This document specifies the use of Topology Independent Loop-Free
Alternate (TI-LFA) mechanisms with Multicast Only Multicast-only Fast ReRoute Reroute
(MoFRR) for Protocol Independent Multicast (PIM). The TI-LFA
provides fast reroute Fast Reroute (FRR) protection for unicast traffic in IP
networks by precomputing backup paths that avoid potential failures.
By integrating TI-LFA with MoFRR, this document extends the benefits
of
fast reroute FRR mechanisms to multicast traffic, enabling enhanced resilience
and minimized packet loss in multicast networks. The document
outlines an optional approach to implement TI-LFA in conjunction with
MoFRR for PIM, ensuring that multicast traffic is rapidly rerouted in
the event of a failure.

Status of This Memo

This Internet-Draft document is submitted in full conformance with the
provisions of BCP 78 and BCP 79.

Internet-Drafts are working documents not an Internet Standards Track specification; it is
published for informational purposes.

This document is a product of the Internet Engineering Task Force
(IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list It represents the consensus of current Internet-
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Internet-Drafts are draft the IETF community. It has
received public review and has been approved for publication by the
Internet Engineering Steering Group (IESG). Not all documents valid
approved by the IESG are candidates for a maximum any level of six months Internet
Standard; see Section 2 of RFC 7841.

Information about the current status of this document, any errata,
and how to provide feedback on it may be updated, replaced, or obsoleted by other documents obtained at any
time. It is inappropriate to use Internet-Drafts as reference
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This Internet-Draft will expire on 9 October 2025.
https://www.rfc-editor.org/info/rfc9860.

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Table of Contents

1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3
2. Problem Statement . . . . . . . . . . . . . . . . . . . . . . 4
2.1. LFA for MoFRR . . . . . . . . . . . . . . . . . . . . . . 4
2.2. TI-LFA for MoFRR . . . . . . . . . . . . . . . . . . . . 5
3. A Solution . . . . . . . . . . . . . . . . . . . . . . . . . 5
3.1. Overview . . . . . . . . . . . . . . . . . . . . . . . . 6
3.2. Procedure . . . . . . . . . . . . . . . . . . . . . . . . 7
4. Illustration . . . . . . . . . . . . . . . . . . . . . . . . 7
5. Management and Operational Considerations . . . . . . . . . . 11
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 11
7. Security Considerations . . . . . . . . . . . . . . . . . . . 11
8. References . . . . . . . . . . . . . . . . . . . . . . . . . 13
8.1. Normative References . . . . . . . . . . . . . . . . . . 13
8.2. Informative References . . . . . . . . . . . . . . . . . 15
Contributors . . . . . . . . . . . . . . . . . . . . . . . . . . 15
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 15

1. Introduction

Multicast-only Fast Reroute (MoFRR), as defined in [RFC7431], offers
a mechanism to reduce multicast packet loss in the event of node or
link failures by introducing simple enhancements to multicast routing
protocols, such as Protocol Independent Multicast (PIM) [RFC7761].
However, the [RFC7431] MoFRR mechanism, which selects the secondary
multicast next-hop next hop based solely on the loop-free alternate fast
reroute Loop-Free Alternate (LFA) FRR
defined in [RFC7431], has limitations in certain multicast deployment
scenarios (see Section 2).

This document introduces a new mechanism for MoFRR using FRR for
Topology Independent Loop-Free Alternate (TI-LFA)
[I-D.ietf-rtgwg-segment-routing-ti-lfa] fast reroute. [RFC9855]. Unlike
conventional methods, TI-LFA is independent of network topology,
enabling broader coverage across diverse network environments. This
mechanism is applicable to PIM networks,including networks, including cases where PIM
operates natively over IP in Segment Routing (SR) networks.

The TI-LFA mechanism is designed for standard link-state Interior
Gateway Protocol (IGP) shortest path and SR scenarios. For each
destination advertised by the IGP in a network, TI-LFA pre-installs a
backup forwarding entry for the protected destination, which is ready
to be activated upon the detection of a link failure used to reach
that destination. This document leverages the backup path computed
by TI-
LFA TI-LFA through the IGP as a secondary Upstream Multicast Hop (UMH)
for PIM. By sending PIM secondary Join messages hop by hop on the
TI-LFA backup path, a fast reroute FRR backup path can be created for PIM
multicast.

The techniques described in this document are limited to protecting
links and nodes within a link-state IGP area. Protecting domain exit
routers and/or links attached to other routing domains is beyond the
scope of this document. All the Segment Identifiers (SIDs) required
are contained within the Link State Database (LSDB) of the IGP.

The approach does not alter the existing management and operation of
LFA, RLFA, TI-LFA, and TI-LFA Remote LFA (RLFA) [RFC7916] [RFC8102]
[I-D.ietf-rtgwg-segment-routing-ti-lfa]. [RFC9855].
Additionally, during post-
failure post-failure reconvergence, micro-loops
[RFC5715] may form due to transient forwarding inconsistencies across
routers. PIM micro-loop prevention is out of scope for this
document.

Note that this document introduces an optional approach for backup
Join paths, designed to enhance the protection scope of existing
multicast systems. It is fully compatible with current protocol
implementations and does not necessitate any changes to the protocols
or forwarding functions on intermediate nodes. All nodes along the
backup Join paths must support the RPF Reverse Path Forwarding (RPF)
Vector attribute Attribute as defined in [RFC5496] and [RFC7891]. If there is
a choice between vector and non-vector Join messages on the
intermediate nodes, the non-vector option should be prioritized,
which implies that protection paths will remain inactive. This
document does not modify the handling of conflicts in PIM Join
messages. For guidance on conflicts in Join attributes, please refer
to Section 3.3.3 of [RFC5384].

1.1. Terminology

This document utilizes the terminology as defined in [RFC7431] and
incorporates the concepts established in [RFC7490]. The definitions
of individual terms are not reiterated within this document.

2. Problem Statement

2.1. LFA for MoFRR

Section 3 of [RFC7431] specifies that a secondary UMH in PIM for
MoFRR is a Loop-Free Alternate (LFA). However, the conventional LFA
mechanism requires that at least one neighbor's next-hop next hop to the
destination node is a loop-free next-hop. next hop. Due to existing
limitations of the LFA mechanism in network deployments, such as
topology dependency and incomplete destination coverage, the LFA
mechanism can only be deployed in certain network topology
environments. In specific network topologies, the secondary UMH
cannot be computed in PIM for MoFRR, preventing PIM from establishing
a standby multicast tree tree, and thus from implementing preventing the implementation of
MoFRR protection. Consequently, the [RFC7431] MoFRR functionality in
PIM is applicable only in network topologies where LFA is feasible.

The limitations of the [RFC7431] MoFRR applicability can be
illustrated using the example network depicted in Figure 1. In this
example, the metric of the R1-R4 link is 20, the metric of the R5-R6
link is 100, and the metrics of the other links are 10. All link
metrics are bidirectional.

For multicast source S1 and receiver R, the primary path of the PIM
Join packet is R3->R2->R1, and the secondary path is R3->R4->R1,
which corresponds to the LFA path of unicast routing. In this
scenario, the [RFC7431] MoFRR operates effectively.

For multicast source S2 and receiver R, the primary path of the PIM
Join packet is R3->R2. However, an LFA does not exist. If R3 sends
the packet to R4, R4 will forward it back to R3 because the IGP
shortest path from R4 to R1 is R4->R3->R2. In this case, the
[RFC7431] MoFRR cannot calculate a secondary UMH. Similarly, for
multicast source S3 and receiver R, the [RFC7431] MoFRR mechanism is
ineffective.

10 20
[S1]----(R1)-------------(R4)
| |
| |
|10 |10
10 | |
[S2]----(R2)-------------(R3)----[R]
| 10 | 10
| |
|10 |10
10 | |
[S3]----(R5)-----(R6)----(R7)
100 10

Figure 1: Example Network Topology

2.2. TI-LFA for MoFRR

The alternate path provided by the TI-LFA mechanism is represented as
a Segment List, which includes the NodeSID of the P-space node and
the Adjacency SIDs of the links between the P-space and Q-space
nodes. When a remote PQ node exists in both P-space and Q-space, the
Segment List requires only the PQ node's NodeSID.

PIM can look up the corresponding node node's IP address in the unicast
route base according to the NodeSID and the IP addresses of the
endpoints of the corresponding link in the unicast route base
according to the Adjacency SIDs. However, multicast protocol packets
cannot be directly forwarded along the path of the Segment List.

To establish a standby multicast tree, PIM Join messages need to be
transmitted hop-by-hop. hop by hop. However, not all nodes and links on the
unicast alternate path are included in the Segment List. If PIM
protocol packets are transmitted solely in unicast mode, they
effectively traverse the unicast tunnel like unicast traffic and do
not pass through the intermediate nodes of the tunnel. Consequently,
the intermediate nodes on the alternate path cannot forward multicast
traffic because they lack PIM state entries. PIM must create entries
on each device hop-by-hop, hop by hop, generating an incoming interface and an
outgoing interface list, to form a complete end-to- end end-to-end multicast tree
for forwarding multicast traffic. Therefore, simply sending PIM Join
packets using the Segment List, as done with unicast traffic, is
insufficient to establish a standby multicast tree.

3. A Solution

3.1. Overview

A secondary UMH serves as a candidate next-hop next hop that can be used to
reach the root of a multicast tree. In this document, the secondary
UMH is derived from unicast routing, utilizing the Segment List
computed by TI-LFA.

The path information from the Segment List is incorporated into the
PIM packets to guide hop-by-hop RPF selection. The IP address
corresponding to the Node SID can be used as the segmented root node,
while the IP addresses of the interfaces at both endpoints of the
link associated with the Adjacency SID can be used as the local
upstream interface and upstream neighbor.

[RFC5496] defines the PIM RPF Vector attribute, Attribute, which can carry the
node's IP address corresponding to the Node SID. Additionally,
[RFC7891] defines the explicit Explicit RPF Vector, which can carry the peer's
IP address corresponding to the Adjacency SID.

For instance, in the network illustrated in Figure 1, the secondary
path for the PIM Join packet towards multicast source S2 cannot be
computed by [RFC7431] MoFRR, as previously described. Using TI-LFA,
R3 sends the packet to R4 while including an RPF Vector that contains
the IP address of R1, which serves as R3's PQ node for the protected
R3-R2 link. R4 then forwards the packet to R1 via the R1- R4 R1-R4 link
according to the unicast route associated with the RPF Vector. R1
subsequently forwards the packet to R2, thus establishing the
secondary path R3->R4->R1->R2.

Additionally, for multicast source S3 and receiver R, the primary
path of the PIM Join packet is R3->R2->R5. Using TI-LFA, R3 sends
the PIM Join packet to R7 while including two RPF Vectors:

* The first RPF Vector contains the IP address of R6, which serves
as R3's P-node for the protected R3-R2 link.

* The second RPF Vector contains the interface IP addresses of R6
and R5, which serve as R3's Q-node for the protected R3-R2 link.

The first RPF Vector guides the PIM Join path through R3->R7->R6,
while the second RPF Vector guides the PIM Join path through R6->R5,
thereby establishing the secondary path R3->R7->R6->R5.

This document leverages the above RPF Vector standards, obviating the
need for PIM protocol extensions. This approach allows the
establishment of a standby multicast tree based on the Segment List
calculated by TI-LFA, thereby providing comprehensive MoFRR
protection for multicast services across diverse network
environments.

3.2. Procedure

Consider a Segment List calculated by TI-LFA as (NodeSID(A),
AdjSID(A-B)). Node A belongs to the P-space, and node B belongs to
the Q-space. The IP address corresponding to NodeSID(A) can be
retrieved from the local link-state database LSDB of the IGP and assumed to be IP-a.
Similarly, the IP addresses of the two endpoints of the link
corresponding to AdjSID(A-B) can also be retrieved from the local link-state database
LSDB and assumed to be IP-La and IP-Lb.

Within the PIM process, IP-a is treated as the standard RPF Vector
Attribute and added to the PIM Join packet. IP-La is considered the
local address of the incoming interface, and IP-Lb is regarded as the
address of the upstream neighbor. Consequently, IP-Lb can be
included in the PIM Join packet as the explicit Explicit RPF Vector Attribute.

The PIM protocol initially selects the RPF incoming interface and
upstream neighbor towards IP-a and proceeds hop-by-hop hop by hop to establish
the PIM standby multicast tree until reaching node A. At node A, IP-
Lb is treated as the PIM upstream neighbor. Node A identifies the
incoming interface in the unicast routing table based on IP-Lb, and
IP-Lb is used as the RPF upstream address for the PIM Join packet
directed towards node B.

Upon receiving the PIM Join packet at node B, the PIM protocol,
finding no additional RPF Vector Attributes, selects the RPF incoming
interface and upstream neighbor towards the multicast source
directly. The protocol, then, protocol then continues hop-by-hop hop by hop to establish the
PIM standby multicast tree, extending to the router directly
connected to the source.

When a remote PQ node exists in both P-space and Q-space, the
processing can be simplified to involve only Node node A.

4. Illustration

This section provides an illustration of MoFRR based on TI-LFA. The
example topology is depicted in Figure 2. The metric for the R3-R4
link is 100, while the metrics for the other links are 10. All link
metrics are bidirectional.

<-----Primary Path--- (S,G) Join

[S]---(R1)---(R2)******(R6)-------[R]
| |
<--- | | |
| | | |
| | (R5) |
| | | |
| | | |
| | | |
| (R3)------(R4) |
| |
--Secondary Path--

Figure 2: Example Topology

The IP addresses and SIDs involved in the MoFRR calculation are
configured as follows:

IPv4 Data Plane (MPLS-SR [RFC8660]) data plane (SR-MPLS [RFC8660]):

Node IP Address Node SID
R4 IP4-R4 Label-R4

Link IP Address Adjacency SID
R3->R4 IP4-R3-R4 Label-R3-R4
R4->R3 IP4-R4-R3 Label-R4-R3

IPv6 Data Plane data plane (SRv6 [RFC8986]) [RFC8986]):

Node IP Address Node SID (End)
R4 IP6-R4 SID-R4

Link IP Address Adjacency SID (End.X)
R3->R4 IP6-R3-R4 SID-R3-R4
R4->R3 IP6-R4-R3 SID-R4-R3

The primary path of the PIM Join packet is R6->R2->R1, and the
secondary path is R6->R5->R4->R3->R2->R1. However, the traditional
LFA does not function properly for the secondary path because the
shortest path to R2 from R5 (or from R4) still traverses the R6-R2
link. In this scenario, R6 must calculate the secondary UMH using
the proposed MoFRR method based on TI-LFA.

According to the TI-LFA algorithm, the P-space and Q-space are
illustrated in Figure 3. The TI-LFA repair path consists of the Node
SID of R4 and the Adjacency SID of R4->R3. On the MPLS-SR Segment Routing
over MPLS (SR-MPLS) data plane, the repair segment list is (Label-R4,
Label-R4-R3). On the
SRv6 Segment Routing over IPv6 (SRv6) data plane,
the repair segment list is (SID-R4, SID-R4-R3).

........
. .
[S]---(R1)---(R2)******(R6)---[R]
. | . |
. | . +++|++++
. | . + | +
. | . + (R5) +
. | . + | +
. | . + | +
. | . + | +
. (R3)------(R4) +
. . + +
........ ++++++++
Q-Space P-Space

Figure 3: P-Space and Q-Space

In the PIM process, the IP addresses associated with the repair
segment list are retrieved from the IGP link-state database. LSDB.

On the IPv4 data plane, the Node SID Label-R4 corresponds to IP4-R4,
which will be carried in the RPF Vector Attribute. The Adjacency SID
Label-R4-R3 corresponds to the local address IP4-R4-R3 and the remote
peer address IP4-R3-R4, with IP4-R3-R4 carried in the Explicit RPF
Vector Attribute.

On the IPv6 data plane, the End SID SID-R4 corresponds to IP6-R4,
which will be carried in the RPF Vector Attribute. The End.X SID
SID-R4-R3 corresponds to the local address IP6-R4-R3 and the remote
peer address IP6-R3-R4, with IP6-R3-R4 carried in the Explicit RPF
Vector Attribute.

Subsequently, R6 installs the secondary UMH using these RPF Vectors.

R6----->R5---->R4------------>R3----->R2---->R1

Figure 4: Forwarding PIM Join Packet along Along Secondary Path (IPv4)

On the IPv4 data plane, the forwarding of the PIM Join packet along
the secondary path is shown in Figure 4.

R6 inserts two RPF Vector Attributes in the PIM Join packet: IP4-R4
of Type 0 (RPF Vector Attribute) and IP4-R3-R4 of Type 4 (Explicit
RPF Vector Attribute). R6 then forwards the packet along the
secondary path.

When R5 receives the packet, it performs a unicast route lookup of
the first RPF Vector IP4-R4 and sends the packet to R4.

R4, being the owner of IP4-R4, removes the first RPF Vector from the
packet and forwards it according to the next RPF Vector. R4 sends
the packet to R3 based on the next RPF Vector IP4-R3-R4, as its PIM
neighbor R3 corresponds to IP4-R3-R4.

When R3 receives the packet, as the owner of IP4-R3-R4, it removes
the RPF Vector. The packet, now devoid of RPF Vectors, is forwarded
to the source through R3->R2->R1 based on unicast routes.

After the PIM Join packet reaches R1, a secondary multicast tree,
R1->R2->R3->R4->R5->R6, is established hop-by-hop hop by hop for (S, G) using
MoFRR based on TI-LFA.

R6----->R5---->R4------------>R3----->R2---->R1

Figure 5: Forwarding PIM Join Packet along Along Secondary Path (IPv6)

On the IPv6 data plane, the forwarding of the PIM Join packet along
the secondary path is illustrated in Figure 5. The procedure is
analogous to that of the IPv4 data plane.

When a remote PQ node exists in both P-space and Q-space, the
processing can be simplified to involve only the PQ node. In this
case, only a single RPF Vector needs to be carried, and all other
processing steps remain unchanged.

5. Management and Operational Considerations

The management of the proposed approach is consistent with [RFC7916].
But,
However, in the operation of this approach, the node on the backup
Join paths must have an independent configuration strategy for
installing RPF Vector Attributes in the PIM Join packet and
controlling the sending of this PIM Join messages. message.

All nodes on the backup Join paths must be able to parse the PIM Join
message with the RPF Vector attribute. Attribute. If the nodes do not
understand the RPF Vector attribute Attribute in the PIM Join packet, then it
must discard the RPF Vector attribute Attribute because failing to remove the
RPF Vectors could cause upstream nodes to send the Join back toward towards
these nodes causing loops.

If an administrator is manually specifying the path that the Join
messages need to be sent on, it is recommended that the administrator
computes the path to include nodes that support the Explicit RPF
Vector and check that the state is created correctly on each node
along the path. Tools like mtrace Mtrace [RFC8487] can be used for
debugging and to ensure that the Join state is setup set up correctly.

6. IANA Considerations

This document has no IANA actions.

7. Security Considerations

This document does not introduce additional security concerns. It
does not change the security properties of PIM. For general PIM-SM PIM -
Sparse Mode (PIM-SM) protocol security considerations, see [RFC7761].
The security considerations of LFA, R-LFA, RLFA, and MoFRR described in
[RFC5286], [RFC7490], and [RFC7431] should apply to this document.

When deploying TI-LFA, packets may be sent over nodes and links they
were not transported through before, potentially raising the
following security issues:

1. Spoofing and False Route Advertisements false route advertisements

* Dependencies of LFA/R-LFA/TI-LFA LFA/RLFA/TI-LFA on Routing Information routing information

- LFAs depend on accurate routing information to determine
alternate paths. If an attacker can inject false routing
information (e.g., by spoofing link-state advertisements),
it could cause the network to select suboptimal or
malicious paths for LFAs.

- R-LFA RLFA and TI-LFA also depend on accurate routing
information, particularly for determining the tunneling
paths or explicit paths. False route advertisements could
mislead the network into using insecure or compromised
paths.

2. On-path Attacks attacks

* Use of Alternate Paths alternate paths

- By rerouting traffic through alternate paths, especially
those that traverse multiple hops (as in R-LFA RLFA and TI-LFA),
the risk of On-path on-path attacks increases if any of the
intermediate routers on the alternate path is are compromised.

- TI-LFA, which uses explicit paths, might expose traffic to
routers that were not originally part of the primary path,
potentially allowing for interception or alteration of the
traffic.

3. Confidentiality and Integrity integrity

* Traffic Encapsulation encapsulation

- R-LFA RLFA and TI-LFA involve encapsulating traffic, which may
expose it to vulnerabilities if the encapsulation
mechanisms are not secure. For instance, if IPsec or
another secure encapsulation method is not used, an
attacker might be able to intercept or alter the traffic in
transit.

* Protection of Explicit Paths explicit paths

- TI-LFA relies on explicit paths that are typically defined
using segment routing. SR. If these paths are not properly protected, an
attacker could manipulate the segment list to reroute
traffic through malicious nodes.

4. Increased Attack Surface attack surface

* Extended Topology topology

- By introducing LFA, R-LFA, RLFA, and TI-LFA, the network increases
its reliance on additional routers and links, thereby
expanding the potential attack surface. Compromise of any
router in these alternate paths could expose traffic to
unauthorized access or disruption.

To address security issues #1 1 and #2 2 mentioned above, control plane
protocols need to provide security protection. To mitigate the risks
associated with false route advertisements and On-path on-path attacks, it is
recommended to use secure routing protocols (e.g., OSPFv3 with IPsec,
ISIS
IS-IS HMAC-SHA256, or PIM with IPsec) that provide authentication and
integrity protection for routing updates.

To address security issues #3 3 and #4 4 mentioned above, these mechanisms
need to run within a trusted network. The security of LFA, R-LFA, RLFA, and
TI-LFA mechanisms heavily relies on the trustworthiness of the
underlying routing infrastructure. As the solution described in the
document is based on Segment Routing SR technology, readers should be aware of the
security considerations related to this technology ([RFC8402]) (see [RFC8402])
and its data plane instantiations ([RFC8660], (see [RFC8660], [RFC8754], and
[RFC8986]).

8. References

8.1. Normative References

[I-D.ietf-rtgwg-segment-routing-ti-lfa]

[RFC9855] Bashandy, A., Litkowski, S., Filsfils, C., Francois, P.,
Decraene, B., and D. Voyer, "Topology Independent Fast
Reroute using Using Segment Routing", Work in Progress,
Internet-Draft, draft-ietf-rtgwg-segment-routing-ti-lfa-
21, 12 February RFC 9855,
DOI 10.17487/RFC9855, September 2025,
<https://datatracker.ietf.org/doc/html/draft-ietf-rtgwg-
segment-routing-ti-lfa-21>.
<https://www.rfc-editor.org/info/rfc9855>.

[RFC5286] Atlas, A., Ed. and A. Zinin, Ed., "Basic Specification for
IP Fast Reroute: Loop-Free Alternates", RFC 5286,
DOI 10.17487/RFC5286, September 2008,
<https://www.rfc-editor.org/info/rfc5286>.

[RFC5384] Boers, A., Wijnands, I., and E. Rosen, "The Protocol
Independent Multicast (PIM) Join Attribute Format",
RFC 5384, DOI 10.17487/RFC5384, November 2008,
<https://www.rfc-editor.org/info/rfc5384>.

[RFC5496] Wijnands, IJ., Boers, A., and E. Rosen, "The Reverse Path
Forwarding (RPF) Vector TLV", RFC 5496,
DOI 10.17487/RFC5496, March 2009,
<https://www.rfc-editor.org/info/rfc5496>.

[RFC7431] Karan, A., Filsfils, C., Wijnands, IJ., Ed., and B.
Decraene, "Multicast-Only Fast Reroute", RFC 7431,
DOI 10.17487/RFC7431, August 2015,
<https://www.rfc-editor.org/info/rfc7431>.

[RFC7490] Bryant, S., Filsfils, C., Previdi, S., Shand, M., and N.
So, "Remote Loop-Free Alternate (LFA) Fast Reroute (FRR)",
RFC 7490, DOI 10.17487/RFC7490, April 2015,
<https://www.rfc-editor.org/info/rfc7490>.

[RFC7761] Fenner, B., Handley, M., Holbrook, H., Kouvelas, I.,
Parekh, R., Zhang, Z., and L. Zheng, "Protocol Independent
Multicast - Sparse Mode (PIM-SM): Protocol Specification
(Revised)", STD 83, RFC 7761, DOI 10.17487/RFC7761, March
2016, <https://www.rfc-editor.org/info/rfc7761>.

[RFC7891] Asghar, J., Wijnands, IJ., Ed., Krishnaswamy, S., Karan,
A., and V. Arya, "Explicit Reverse Path Forwarding (RPF)
Vector", RFC 7891, DOI 10.17487/RFC7891, June 2016,
<https://www.rfc-editor.org/info/rfc7891>.

[RFC7916] Litkowski, S., Ed., Decraene, B., Filsfils, C., Raza, K.,
Horneffer, M., and P. Sarkar, "Operational Management of
Loop-Free Alternates", RFC 7916, DOI 10.17487/RFC7916,
July 2016, <https://www.rfc-editor.org/info/rfc7916>.

[RFC8402] Filsfils, C., Ed., Previdi, S., Ed., Ginsberg, L.,
Decraene, B., Litkowski, S., and R. Shakir, "Segment
Routing Architecture", RFC 8402, DOI 10.17487/RFC8402,
July 2018, <https://www.rfc-editor.org/info/rfc8402>.

[RFC8660] Bashandy, A., Ed., Filsfils, C., Ed., Previdi, S.,
Decraene, B., Litkowski, S., and R. Shakir, "Segment
Routing with the MPLS Data Plane", RFC 8660,
DOI 10.17487/RFC8660, December 2019,
<https://www.rfc-editor.org/info/rfc8660>.

[RFC8754] Filsfils, C., Ed., Dukes, D., Ed., Previdi, S., Leddy, J.,
Matsushima, S., and D. Voyer, "IPv6 Segment Routing Header
(SRH)", RFC 8754, DOI 10.17487/RFC8754, March 2020,
<https://www.rfc-editor.org/info/rfc8754>.

[RFC8986] Filsfils, C., Ed., Camarillo, P., Ed., Leddy, J., Voyer,
D., Matsushima, S., and Z. Li, "Segment Routing over IPv6
(SRv6) Network Programming", RFC 8986,
DOI 10.17487/RFC8986, February 2021,
<https://www.rfc-editor.org/info/rfc8986>.

8.2. Informative References

[RFC5715] Shand, M. and S. Bryant, "A Framework for Loop-Free
Convergence", RFC 5715, DOI 10.17487/RFC5715, January
2010, <https://www.rfc-editor.org/info/rfc5715>.

[RFC8102] Sarkar, P., Ed., Hegde, S., Bowers, C., Gredler, H., and
S. Litkowski, "Remote-LFA Node Protection and
Manageability", RFC 8102, DOI 10.17487/RFC8102, March
2017, <https://www.rfc-editor.org/info/rfc8102>.

[RFC8487] Asaeda, H., Meyer, K., and W. Lee, Ed., "Mtrace Version 2:
Traceroute Facility for IP Multicast", RFC 8487,
DOI 10.17487/RFC8487, October 2018,
<https://www.rfc-editor.org/info/rfc8487>.

Contributors

Mengxiao Chen
New H3C Technologies
China
Email: chen.mengxiao@h3c.com

Authors' Addresses

Yisong Liu
China Mobile
China
Email: liuyisong@chinamobile.com

Mike McBride
Futurewei Inc.
USA
United States of America
Email: michael.mcbride@futurewei.com

Zheng(Sandy) Zhang
ZTE Corporation
China
Email: zzhang_ietf@hotmail.com

Jingrong Xie
Huawei Technologies
China
Email: xiejingrong@huawei.com

Changwang Lin
New H3C Technologies
China
Email: linchangwang.04414@h3c.com