draft-ietf-lsr-isis-srv6-extensions-14.txt   draft-ietf-lsr-isis-srv6-extensions-15.txt 
Networking Working Group P. Psenak, Ed. Networking Working Group P. Psenak, Ed.
Internet-Draft C. Filsfils Internet-Draft C. Filsfils
Updates: 7370 (if approved) Cisco Systems Updates: 7370 (if approved) Cisco Systems
Intended status: Standards Track A. Bashandy Intended status: Standards Track A. Bashandy
Expires: October 24, 2021 Individual Expires: November 22, 2021 Individual
B. Decraene B. Decraene
Orange Orange
Z. Hu Z. Hu
Huawei Technologies Huawei Technologies
April 22, 2021 May 21, 2021
IS-IS Extension to Support Segment Routing over IPv6 Dataplane IS-IS Extensions to Support Segment Routing over IPv6 Dataplane
draft-ietf-lsr-isis-srv6-extensions-14 draft-ietf-lsr-isis-srv6-extensions-15
Abstract Abstract
The Segment Routing (SR) allows for a flexible definition of end-to- The Segment Routing (SR) architecture allows flexible definition of
end paths by encoding paths as sequences of topological sub-paths, the end-to-end path by encoding it as a sequence of topological
called "segments". Segment routing architecture can be implemented elements called "segments". It can be implemented over the MPLS or
over an MPLS data plane as well as an IPv6 data plane. This document the IPv6 data plane. This document describes the IS-IS extensions
describes the IS-IS extensions required to support Segment Routing required to support Segment Routing over the IPv6 data plane.
over an IPv6 data plane.
This documents updates RFC 7370 by modifying an existing registry. This document updates RFC 7370 by modifying an existing registry.
Requirements Language 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 BCP
14 [RFC2119] [RFC8174] when, and only when, they appear in all 14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here. capitals, as shown here.
Status of This Memo Status of This Memo
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Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/. Drafts is at https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on October 24, 2021. This Internet-Draft will expire on November 22, 2021.
Copyright Notice Copyright Notice
Copyright (c) 2021 IETF Trust and the persons identified as the Copyright (c) 2021 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
(https://trustee.ietf.org/license-info) in effect on the date of (https://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents publication of this document. Please review these documents
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to this document. Code Components extracted from this document must to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License. described in the Simplified BSD License.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. SRv6 Capabilities sub-TLV . . . . . . . . . . . . . . . . . . 4 2. SRv6 Capabilities sub-TLV . . . . . . . . . . . . . . . . . . 4
3. Advertising Supported Algorithms . . . . . . . . . . . . . . 4 3. Advertising Supported Algorithms . . . . . . . . . . . . . . 4
4. Advertising Maximum SRv6 SID Depths . . . . . . . . . . . . . 4 4. Advertising Maximum SRv6 SID Depths . . . . . . . . . . . . . 5
4.1. Maximum Segments Left MSD Type . . . . . . . . . . . . . 5 4.1. Maximum Segments Left MSD Type . . . . . . . . . . . . . 5
4.2. Maximum End Pop MSD Type . . . . . . . . . . . . . . . . 5 4.2. Maximum End Pop MSD Type . . . . . . . . . . . . . . . . 5
4.3. Maximum H.Encaps MSD Type . . . . . . . . . . . . . . . . 5 4.3. Maximum H.Encaps MSD Type . . . . . . . . . . . . . . . . 5
4.4. Maximum End D MSD Type . . . . . . . . . . . . . . . . . 6 4.4. Maximum End D MSD Type . . . . . . . . . . . . . . . . . 6
5. SRv6 SIDs and Reachability . . . . . . . . . . . . . . . . . 6 5. SRv6 SIDs and Reachability . . . . . . . . . . . . . . . . . 6
6. Advertising Anycast Property . . . . . . . . . . . . . . . . 7 6. Advertising Anycast Property . . . . . . . . . . . . . . . . 7
7. Advertising Locators and End SIDs . . . . . . . . . . . . . . 8 7. Advertising Locators and End SIDs . . . . . . . . . . . . . . 8
7.1. SRv6 Locator TLV Format . . . . . . . . . . . . . . . . . 9 7.1. SRv6 Locator TLV Format . . . . . . . . . . . . . . . . . 9
7.2. SRv6 End SID sub-TLV . . . . . . . . . . . . . . . . . . 10 7.2. SRv6 End SID sub-TLV . . . . . . . . . . . . . . . . . . 10
8. Advertising SRv6 Adjacency SIDs . . . . . . . . . . . . . . . 12 8. Advertising SRv6 Adjacency SIDs . . . . . . . . . . . . . . . 12
8.1. SRv6 End.X SID sub-TLV . . . . . . . . . . . . . . . . . 12 8.1. SRv6 End.X SID sub-TLV . . . . . . . . . . . . . . . . . 12
8.2. SRv6 LAN End.X SID sub-TLV . . . . . . . . . . . . . . . 14 8.2. SRv6 LAN End.X SID sub-TLV . . . . . . . . . . . . . . . 14
9. SRv6 SID Structure Sub-Sub-TLV . . . . . . . . . . . . . . . 16 9. SRv6 SID Structure Sub-Sub-TLV . . . . . . . . . . . . . . . 16
10. Advertising Endpoint Behaviors . . . . . . . . . . . . . . . 17 10. Advertising Endpoint Behaviors . . . . . . . . . . . . . . . 17
11. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 17 11. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 18
11.1. SRv6 Locator TLV . . . . . . . . . . . . . . . . . . . . 17 11.1. SRv6 Locator TLV . . . . . . . . . . . . . . . . . . . . 18
11.1.1. SRv6 End SID sub-TLV . . . . . . . . . . . . . . . . 18 11.1.1. SRv6 End SID sub-TLV . . . . . . . . . . . . . . . . 18
11.1.2. Revised sub-TLV table . . . . . . . . . . . . . . . 18 11.1.2. Revised sub-TLV table . . . . . . . . . . . . . . . 18
11.2. SRv6 Capabilities sub-TLV . . . . . . . . . . . . . . . 19 11.2. SRv6 Capabilities sub-TLV . . . . . . . . . . . . . . . 19
11.3. SRv6 End.X SID and SRv6 LAN End.X SID sub-TLVs . . . . . 19 11.3. Sub-Sub-TLVs of the SRv6 Capability sub-TLV . . . . . . 19
11.4. MSD Types . . . . . . . . . . . . . . . . . . . . . . . 20 11.4. SRv6 End.X SID and SRv6 LAN End.X SID sub-TLVs . . . . . 19
11.5. Sub-Sub-TLVs for SID Sub-TLVs . . . . . . . . . . . . . 20 11.5. MSD Types . . . . . . . . . . . . . . . . . . . . . . . 20
11.6. Prefix Attribute Flags Sub-TLV . . . . . . . . . . . . . 21 11.6. Sub-Sub-TLVs for SID Sub-TLVs . . . . . . . . . . . . . 20
11.7. ISIS SRv6 Capabilities sub-TLV Flags Registry . . . . . 21 11.7. Prefix Attribute Flags Sub-TLV . . . . . . . . . . . . . 21
11.8. ISIS SRv6 Locator TLV Flags Registry . . . . . . . . . . 21 11.8. ISIS SRv6 Capabilities sub-TLV Flags Registry . . . . . 21
11.9. ISIS SRv6 End SID sub-TLV Flags Registry . . . . . . . . 22 11.9. ISIS SRv6 Locator TLV Flags Registry . . . . . . . . . . 21
11.10. ISIS SRv6 End.X SID and LAN End.X SID sub-TLVs Flags 11.10. ISIS SRv6 End SID sub-TLV Flags Registry . . . . . . . . 22
11.11. ISIS SRv6 End.X SID and LAN End.X SID sub-TLVs Flags
Registry . . . . . . . . . . . . . . . . . . . . . . . . 22 Registry . . . . . . . . . . . . . . . . . . . . . . . . 22
12. Security Considerations . . . . . . . . . . . . . . . . . . . 23 12. Security Considerations . . . . . . . . . . . . . . . . . . . 23
13. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 23 13. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 23
14. References . . . . . . . . . . . . . . . . . . . . . . . . . 24 14. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 24
14.1. Normative References . . . . . . . . . . . . . . . . . . 24 15. References . . . . . . . . . . . . . . . . . . . . . . . . . 25
14.2. Informative References . . . . . . . . . . . . . . . . . 27 15.1. Normative References . . . . . . . . . . . . . . . . . . 25
15.2. Informative References . . . . . . . . . . . . . . . . . 27
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 27 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 27
1. Introduction 1. Introduction
With Segment Routing (SR) [RFC8402], a node steers a packet through With Segment Routing (SR) [RFC8402], a node steers a packet through
an ordered list of instructions, called segments. an ordered list of instructions, called segments.
Segments are identified through Segment Identifiers (SIDs). Segments are identified through Segment Identifiers (SIDs).
Segment Routing can be directly instantiated on the IPv6 data plane Segment Routing can be directly instantiated on the IPv6 data plane
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describes how any behavior can be bound to a SID and how any network describes how any behavior can be bound to a SID and how any network
program can be expressed as a combination of SIDs. program can be expressed as a combination of SIDs.
This document specifies IS-IS extensions that allow the IS-IS This document specifies IS-IS extensions that allow the IS-IS
protocol to encode some of these SIDs and their behaviors. protocol to encode some of these SIDs and their behaviors.
Familiarity with the network programming paradigm [RFC8986] is Familiarity with the network programming paradigm [RFC8986] is
necessary to understand the extensions specified in this document. necessary to understand the extensions specified in this document.
The new SRv6 Locator top level TLV announces SRv6 locators - a form The new SRv6 Locator top level TLV announces SRv6 locators - a form
of summary address for the set of topology/algorithm specific SIDs of summary address for the set of topology/algorithm-specific SIDs
instantiated at the node. instantiated at the node.
The SRv6 Capabilities sub-TLV announces the ability to support SRv6. The SRv6 Capabilities sub-TLV announces the ability to support SRv6.
Several new sub-TLVs are defined to advertise various SRv6 Maximum Several new sub-TLVs are defined to advertise various SRv6 Maximum
SID Depths. SID Depths.
The SRv6 End SID sub-TLV, the SRv6 End.X SID sub-TLV, and the SRv6 The SRv6 End SID sub-TLV, the SRv6 End.X SID sub-TLV, and the SRv6
LAN End.X SID sub-TLV are used to advertise which SIDs are LAN End.X SID sub-TLV are used to advertise which SIDs are
instantiated at a node and what Endpoint behavior is bound to each instantiated at a node and what Endpoint behavior is bound to each
instantiated SID. instantiated SID.
This documents updates [RFC7370] by modifying an existing registry This document updates [RFC7370] by modifying an existing registry
(Section 11.1.2). (Section 11.1.2).
2. SRv6 Capabilities sub-TLV 2. SRv6 Capabilities sub-TLV
A node indicates that it supports the SR Segment Endpoint Node A node indicates that it supports the SR Segment Endpoint Node
functionality as specified in [RFC8754] by advertising a new SRv6 functionality as specified in [RFC8754] by advertising a new SRv6
Capabilities sub-TLV of the router capabilities TLV [RFC7981]. Capabilities sub-TLV of the router capabilities TLV [RFC7981].
The SRv6 Capabilities sub-TLV may contain optional sub-sub-TLVs. No The SRv6 Capabilities sub-TLV may contain optional sub-sub-TLVs. No
sub-sub-TLVs are currently defined. sub-sub-TLVs are currently defined.
The SRv6 Capabilities sub-TLV has the following format: The SRv6 Capabilities sub-TLV has the following format:
0 1 2 3 0 1 2 3
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 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length | Flags | | Type | Length | Flags |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| optional sub-sub-TLVs... | optional sub-sub-TLVs...
Type: 25 Type: 25
Length: 2 + length of sub-sub-TLVs Length: 2 + length of sub-sub-TLVs
Flags: 2 octets The following flags are defined: Flags: 2 octets The following flags are defined:
0 1 0 1
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |O| | | |O| Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
where: where:
O-flag: If set, the router supports use of the O-bit O-flag: If set, the router supports use of the O-bit
in the Segment Routing Header (SRH) as defined in in the Segment Routing Header (SRH) as defined in
[I-D.ietf-6man-spring-srv6-oam]. [I-D.ietf-6man-spring-srv6-oam].
The remaining bits, including bit 0, are reserved for future use. They MUST be
set to zero on transmission and MUST be ignored on receipt.
3. Advertising Supported Algorithms 3. Advertising Supported Algorithms
An SRv6 capable router indicates supported algorithm(s) by An SRv6 capable router indicates supported algorithm(s) by
advertising the SR Algorithm sub-TLV as defined in [RFC8667]. advertising the Segment Routing Algorithm sub-TLV as defined in
[RFC8667].
4. Advertising Maximum SRv6 SID Depths 4. Advertising Maximum SRv6 SID Depths
[RFC8491] defines the means to advertise node/link specific values [RFC8491] defines the means to advertise node/link specific values
for Maximum SID Depths (MSD) of various types. Node MSDs are for Maximum SID Depths (MSD) of various types. Node MSDs are
advertised in a sub-TLV of the Router Capabilities TLV [RFC7981]. advertised in a sub-TLV of the Router Capabilities TLV [RFC7981].
Link MSDs are advertised in a sub-TLV of TLVs 22, 23, 25, 141, 222,
Link MSDs are advertised in a sub-TLV of TLVs 22, 23, 141, 222, and and 223.
223.
This document defines the relevant SRv6 MSDs and requests MSD type This document defines the relevant SRv6 MSDs and requests MSD type
assignments in the MSD Types registry created by [RFC8491]. assignments in the MSD Types registry created by [RFC8491].
4.1. Maximum Segments Left MSD Type 4.1. Maximum Segments Left MSD Type
The Maximum Segments Left MSD Type signals the maximum value of the The Maximum Segments Left MSD Type signals the maximum value of the
"Segments Left" field [RFC8754] in the SRH of a received packet "Segments Left" field [RFC8754] in the SRH of a received packet
before applying the Endpoint behavior associated with a SID. before applying the Endpoint behavior associated with a SID.
SRH Max Segments Left Type: 41 SRH Max Segments Left Type: 41
If no value is advertised the supported value is 0. If no value is advertised, the supported value is 0.
4.2. Maximum End Pop MSD Type 4.2. Maximum End Pop MSD Type
The Maximum End Pop MSD Type signals the maximum number of SIDs in The Maximum End Pop MSD Type signals the maximum number of SIDs in
the SRH to which the router can apply "Penultimate Segment Pop of the the SRH to which the router can apply "Penultimate Segment Pop of the
SRH" or "Ultimate Segment Pop of the SRH" behavior, as defined in SRH" or "Ultimate Segment Pop of the SRH" behavior, as defined in
[RFC8986] flavors. [RFC8986] flavors.
SRH Max End Pop Type: 42 SRH Max End Pop Type: 42
If the advertised value is zero or no value is advertised If the advertised value is zero or no value is advertised,
then the router cannot apply PSP or USP flavors. then the router cannot apply PSP or USP flavors.
4.3. Maximum H.Encaps MSD Type 4.3. Maximum H.Encaps MSD Type
The Maximum H.Encaps MSD Type signals the maximum number of SIDs that The Maximum H.Encaps MSD Type signals the maximum number of SIDs that
can be added as part of the "H.Encaps" behavior as defined in can be added to the Segment List of an SRH as part of the "H.Encaps"
[RFC8986]. behavior as defined in [RFC8986].
SRH Max H.encaps Type: 44 SRH Max H.encaps Type: 44
If the advertised value is zero or no value is advertised then the If the advertised value is zero or no value is advertised, then the
headend can apply an SR Policy that only contains one segment, without headend can apply an SR Policy that only contains one segment, without
inserting any SRH header. inserting any SRH header.
A non-zero SRH Max H.encaps MSD indicates that the headend can insert A non-zero SRH Max H.encaps MSD indicates that the headend can insert
an SRH up to the advertised value. an SRH up to the advertised number of SIDs.
4.4. Maximum End D MSD Type 4.4. Maximum End D MSD Type
The Maximum End D MSD Type specifies the maximum number of SIDs The Maximum End D MSD Type specifies the maximum number of SIDs
present in an SRH when performing decapsulation. These includes, but present in an SRH when performing decapsulation. As specified in
not limited to, End.DX6, End.DT4, End.DT46, End with USD, End.X with [RFC8986] the permitted SID types include, but are not limited to
USD as defined in [RFC8986]. End.DX6, End.DT4, End.DT46, End with USD, End.X with USD.
SRH Max End D Type: 45 SRH Max End D Type: 45
If the advertised value is zero or no value is advertised If the advertised value is zero or no value is advertised
then the router cannot apply any behavior that results in then the router cannot apply any behavior that results in
decapsulation and forwarding of the inner packet if the decapsulation and forwarding of the inner packet if the
other IPv6 header contains an SRH. outer IPv6 header contains an SRH.
5. SRv6 SIDs and Reachability 5. SRv6 SIDs and Reachability
As discussed in [RFC8986], an SRv6 Segment Identifier (SID) is 128 As discussed in [RFC8986], an SRv6 Segment Identifier (SID) is 128
bits and consists of Locator, Function and Argument parts. bits and consists of Locator, Function and Argument parts.
A node is provisioned with topology/algorithm specific locators for A node is provisioned with topology/algorithm specific locators for
each of the topology/algorithm pairs supported by that node. Each each of the topology/algorithm pairs supported by that node. Each
locator is a covering prefix for all SIDs provisioned on that node locator is a covering prefix for all SIDs provisioned on that node
which have the matching topology/algorithm. which have the matching topology/algorithm.
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advertised in the SRv6 Locator TLV, the calculation of its advertised in the SRv6 Locator TLV, the calculation of its
reachability and the installation in the forwarding plane follows the reachability and the installation in the forwarding plane follows the
process defined for the Prefix Reachability TLV 236 [RFC5308], or TLV process defined for the Prefix Reachability TLV 236 [RFC5308], or TLV
237 [RFC5120]. 237 [RFC5120].
Locators associated with algorithm 0 and 1 (for all supported Locators associated with algorithm 0 and 1 (for all supported
topologies) SHOULD be advertised in a Prefix Reachability TLV (236 or topologies) SHOULD be advertised in a Prefix Reachability TLV (236 or
237) so that legacy routers (i.e., routers which do not support SRv6) 237) so that legacy routers (i.e., routers which do not support SRv6)
will install a forwarding entry for algorithm 0 and 1 SRv6 traffic. will install a forwarding entry for algorithm 0 and 1 SRv6 traffic.
In cases where a locator advertisement is received in both a Prefix In cases where the same prefix, with the same prefix-length, Multi
Reachability TLV and an SRv6 Locator TLV - (e.g. prefix, prefix- Topology ID (MT ID), and algorithm is received in both a Prefix
length, MTID all being equal and Algorithm being 0 in Locator TLV), Reachability TLV and an SRv6 Locator TLV, the Prefix Reachability
In case where the same prefix, with the same prefix-length, MTID, and advertisement MUST be preferred when installing entries in the
algorithm is received in both a Prefix Reachability TLV and an SRv6 forwarding plane. This is to prevent inconsistent forwarding entries
Locator TLV, the Prefix Reachability advertisement MUST be preferred between SRv6 capable and SRv6 incapable routers. Such preference of
when installing entries in the forwarding plane. This is to prevent Prefix Reachability advertisement does not have any impact on the
inconsistent forwarding entries between SRv6 capable and SRv6 rest of the data advertised in the SRv6 Locator TLV.
incapable routers. Such preference of Prefix Reachability
advertisement does not have any impact on the rest of the data
advertised in the SRv6 Locator TLV.
Locators associated with Flexible Algorithms (see Section 4 of Locators associated with Flexible Algorithms (see Section 4 of
[I-D.ietf-lsr-flex-algo]) SHOULD NOT be advertised in Prefix [I-D.ietf-lsr-flex-algo]) SHOULD NOT be advertised in Prefix
Reachability TLVs (236 or 237). Advertising the Flexible Algorithm Reachability TLVs (236 or 237). Advertising the Flexible Algorithm
locator in regular Prefix Reachability TLV (236 or 237) would make locator in regular Prefix Reachability TLV (236 or 237) would make
the forwarding for it to follow algo 0 path. the forwarding for it to follow algo 0 path.
SRv6 SIDs are advertised as sub-TLVs in the SRv6 Locator TLV except SRv6 SIDs are advertised as sub-TLVs in the SRv6 Locator TLV except
for SRv6 SIDs which are associated with a specific Neighbor/Link and for SRv6 SIDs which are associated with a specific Neighbor/Link and
are therefore advertised as sub-TLVs in TLVs 22, 23, 222, 223, and are therefore advertised as sub-TLVs in TLVs 22, 23, 25, 141, 222,
141. and 223.
SRv6 SIDs received from other nodes are not directly routable and SRv6 SIDs received from other nodes are not directly routable and
MUST NOT be installed in the forwarding plane. Reachability to SRv6 MUST NOT be installed in the forwarding plane. Reachability to SRv6
SIDs depends upon the existence of a covering locator. SIDs depends upon the existence of a covering locator.
Adherence to the rules defined in this section will assure that SRv6 Adherence to the rules defined in this section will assure that SRv6
SIDs associated with a supported topology/algorithm pair will be SIDs associated with a supported topology/algorithm pair will be
forwarded correctly, while SRv6 SIDs associated with an unsupported forwarded correctly, while SRv6 SIDs associated with an unsupported
topology/algorithm pair will be dropped. NOTE: The drop behavior topology/algorithm pair will be dropped. NOTE: The drop behavior
depends on the absence of a default/summary route covering a given depends on the absence of a default/summary route covering a given
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receiving routers MUST ignore the N-flag. receiving routers MUST ignore the N-flag.
The same prefix/SRv6 Locator can be advertised by multiple routers. The same prefix/SRv6 Locator can be advertised by multiple routers.
If at least one of them sets the A-Flag in its advertisement, the If at least one of them sets the A-Flag in its advertisement, the
prefix/SRv6 Locator SHOULD be considered as anycast. prefix/SRv6 Locator SHOULD be considered as anycast.
A prefix/SRv6 Locator that is advertised by a single node and without A prefix/SRv6 Locator that is advertised by a single node and without
an A-Flag is considered node specific. an A-Flag is considered node specific.
All the nodes advertising the same anycast locator MUST instantiate All the nodes advertising the same anycast locator MUST instantiate
the exact same set of SIDs under such anycast locator. Failure to do the exact same set of SIDs under that anycast locator. Failure to do
so may result in traffic being black-holed or mis-routed. so may result in traffic being black-holed or mis-routed.
The Prefix Attribute Flags Sub-TLV can be carried in the SRv6 Locator The Prefix Attribute Flags Sub-TLV can be carried in the SRv6 Locator
TLV as well as the Prefix Reachability TLVs. When a router TLV as well as the Prefix Reachability TLVs. When a router
originates both the Prefix Reachability TLV and the SRv6 Locator TLV originates both the Prefix Reachability TLV and the SRv6 Locator TLV
for a given prefix, and the router is originating the Prefix for a given prefix, and the router is originating the Prefix
Attribute Flags Sub-TLV in one of the TLVs, the router SHOULD Attribute Flags Sub-TLV in one of the TLVs, the router SHOULD
advertise the same flags in the Prefix Attribute Flags Sub-TLV in advertise the same flags in the Prefix Attribute Flags Sub-TLV in
both TLVs. However, unlike TLVs 236 [RFC5308] and 237 [RFC5120] the both TLVs. However, unlike TLVs 236 [RFC5308] and 237 [RFC5120] the
X-flag in the Prefix Attributes Flags sub-TLV is valid when sent in X-flag in the Prefix Attributes Flags sub-TLV is valid when sent in
the SRv6 Locator TLV. The state of the X-flag in the Prefix the SRv6 Locator TLV. The state of the X-flag in the Prefix
Attributes Flags sub-TLV when included in the Locator TLV MUST match Attributes Flags sub-TLV when included in the Locator TLV MUST match
the setting of the embedded "X-bit" in any advertisement of the same the setting of the embedded "X-bit" in any advertisement for the same
prefix in TLVs 236 [RFC5308] and 237 [RFC5120]. In case of any prefix in TLVs 236 [RFC5308] and 237 [RFC5120]. In case of any
inconsistency between the Prefix Attribute Flags advertised in the inconsistency between the Prefix Attribute Flags advertised in the
Locator TLV and in the Prefix Reachability TLV, the ones advertised Locator TLV and in the Prefix Reachability TLV, the ones advertised
in Prefix Reachability TLV MUST be preferred. in Prefix Reachability TLV MUST be preferred.
7. Advertising Locators and End SIDs 7. Advertising Locators and End SIDs
The SRv6 Locator TLV is introduced to advertise SRv6 Locators and End The SRv6 Locator TLV is introduced to advertise SRv6 Locators and End
SIDs associated with each locator. SIDs associated with each locator.
skipping to change at page 9, line 14 skipping to change at page 9, line 14
7.1. SRv6 Locator TLV Format 7.1. SRv6 Locator TLV Format
The SRv6 Locator TLV has the following format: The SRv6 Locator TLV has the following format:
0 1 2 3 0 1 2 3
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 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length |R|R|R|R| MT ID | | Type | Length |R|R|R|R| MT ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Locator Entries . . . |
Type: 27 Type: 27
Length: variable. Length: variable.
R bits: reserved for future use. They MUST be R bits: reserved for future use. They MUST be set to zero on
set to zero on transmission and MUST be ignored on receipt. transmission and MUST be ignored on receipt.
MT ID: Multitopology Identifier as defined in [RFC5120]. MT ID: Multitopology Identifier as defined in [RFC5120]. Note
Note that the value 0 is legal. that the value 0 is legal.
Followed by one or more locator entries of the form: Followed by one or more locator entries of the form:
0 1 2 3 0 1 2 3
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 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Metric | | Metric |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Flags | Algorithm | | Flags | Algorithm |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Loc Size | Locator (variable)... | Loc Size | Locator (variable)...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sub-TLV-len | Sub-TLVs (variable) . . . | | Sub-TLV-len | Sub-TLVs (variable) . . . |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Metric: 4 octets. As described in [RFC5305]. Metric: 4 octets. As described in Section 4 of [RFC5305].
Flags: 1 octet. The following flags are defined Flags: 1 octet. The following flags are defined:
0 0
0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7
+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+
|D| Reserved | |D| Reserved |
+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+
where: D-flag: Same as described in section 4.1. of [RFC5305].
D-flag: Same as described in section 4.1. of [RFC5305].
The remaining bits are reserved for future use. They MUST be The remaining bits are reserved for future use. They MUST be
set to zero on transmission and MUST be ignored on receipt. set to zero on transmission and MUST be ignored on receipt.
Algorithm: 1 octet. As defined in [RFC8665]. Algorithm: 1 octet. As defined in IGP Algorithm Types registry
[RFC8665].
Loc-Size: 1 octet. Number of bits in the SRv6 Locator field. Loc-Size: 1 octet. Number of bits in the SRv6 Locator field.
MUST be from the range (1 - 128). The TLV MUST be ignored if MUST be from the range (1 - 128). The TLV MUST be ignored if the
the Loc-Size is outside of this range. Loc-Size is outside this range.
Locator: 1-16 octets. This field encodes the advertised SRv6 Locator: 1-16 octets. This field encodes the advertised SRv6
Locator. The Locator is encoded in the minimal number of Locator. The Locator is encoded in the minimal number of octets
octets for the given number of bits. Trailing bits MUST be set for the given number of bits. Trailing bits MUST be set to zero
to zero and ignored when received. and ignored when received.
Sub-TLV-length: 1 octet. Number of octets used by sub-TLVs Sub-TLV-length: 1 octet. Number of octets used by sub-TLVs.
Optional sub-TLVs: Sub-TLVs 1, 2, 4, 5, 11, 12 are allowed. Optional sub-TLVs: Supported sub-TLVs are specified in
Any other Sub-TLVs MUST be ignored. Section 11.1.2. Any Sub-TLV that is not allowed in the SRv6
Locator TLV MUST be ignored.
Prefix Attribute Flags Sub-TLV [RFC7794] SHOULD be included in the
Locator TLV.
Prefix Attribute Flags Sub-TLV MUST be included in the the Locator
TLV when it is leaked upwards in the hierarchy or originated as a
result of the redistribution from another protocol or another ISIS
instance. If the Prefix Attribute Flags Sub-TLV is not included in
these cases, receivers will be unable to determine the correct source
of the advertisement. The receivers will be unable to detect the
violation.
7.2. SRv6 End SID sub-TLV 7.2. SRv6 End SID sub-TLV
The SRv6 End SID sub-TLV is introduced to advertise SRv6 Segment The SRv6 End SID sub-TLV is introduced to advertise SRv6 Segment
Identifiers (SID) with Endpoint behaviors which do not require a Identifiers (SID) with Endpoint behaviors which do not require a
particular neighbor in order to be correctly applied. SRv6 SIDs particular neighbor in order to be correctly applied. SRv6 SIDs
associated with a neighbor are advertised using the sub-TLVs defined associated with a neighbor are advertised using the sub-TLVs defined
in Section 8. in Section 8.
Supported behavior values together with parent TLVs in which they Supported behavior values, together with parent TLVs in which they
area advertised are specified in Section 10 of this document. Please are advertised, are specified in Section 10 of this document. Please
note that not all behaviors defined in [RFC8986] are defined in this note that not all behaviors defined in [RFC8986] are defined in this
document, e.g. END.T is not. document, e.g. END.T is not.
This new sub-TLV is advertised in the SRv6 Locator TLV defined in the This new sub-TLV is advertised in the SRv6 Locator TLV defined in the
previous section. SRv6 End SIDs inherit the topology/algorithm from previous section. SRv6 End SIDs inherit the topology/algorithm from
the parent locator. the parent locator.
The SRv6 End SID sub-TLV has the following format: The SRv6 End SID sub-TLV has the following format:
0 1 2 3 0 1 2 3
skipping to change at page 11, line 27 skipping to change at page 11, line 29
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| SID (cont . . .) | | SID (cont . . .) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Sub-sub-TLV-len| Sub-sub-TLVs (variable) . . . | |Sub-sub-TLV-len| Sub-sub-TLVs (variable) . . . |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type: 5. Type: 5.
Length: variable. Length: variable.
Flags: 1 octet. No flags are currently defined. Flags: 1 octet. No flags are currently defined. All bits are
reserved for future use. They MUST be set to zero on transmission
and MUST be ignored on receipt.
Endpoint Behavior: 2 octets, as defined in [RFC8986]. Supported Endpoint Behavior: 2 octets, as defined in [RFC8986]. Supported
behavior values for this sub-TLV are defined in Section 10 of this behavior values for this sub-TLV are defined in Section 10 of this
document. Unsupported or unrecognized behavior values are ignored document. Unsupported or unrecognized behavior values are ignored
by the receiver. by the receiver.
SID: 16 octets. This field encodes the advertised SRv6 SID. SID: 16 octets. This field encodes the advertised SRv6 SID.
Sub-sub-TLV-length: 1 octet. Number of octets used by sub-sub- Sub-sub-TLV-length: 1 octet. Number of octets used by sub-sub-
TLVs. TLVs.
Optional Sub-sub-TLVs. Optional Sub-sub-TLVs: Supported Sub-sub-TLVs are specified in
Section 11.6. Any Sub-sub-TLV that is not allowed in SRv6 End SID
sub-TLV MUST be ignored.
The SRv6 End SID MUST be a subnet of the associated Locator. SRv6 The SRv6 End SID MUST be allocated from its associated locator. SRv6
End SIDs which are not a subnet of the associated locator MUST be End SIDs that are not allocated from the associated locator MUST be
ignored. ignored.
Multiple SRv6 End SIDs MAY be associated with the same locator. In Multiple SRv6 End SIDs MAY be associated with the same locator. In
cases where the number of SRv6 End SID sub-TLVs exceeds the capacity cases where the number of SRv6 End SID sub-TLVs exceeds the capacity
of a single TLV, multiple Locator TLVs for the same locator MAY be of a single TLV, multiple Locator TLVs for the same locator MAY be
advertised. For a given MTID/Locator the algorithm MUST be the same advertised. For a given MTID/Locator the algorithm MUST be the same
in all TLVs. If this restriction is not met all TLVs for that MTID/ in all TLVs. If this restriction is not met all TLVs for that MTID/
Locator MUST be ignored. Locator MUST be ignored.
8. Advertising SRv6 Adjacency SIDs 8. Advertising SRv6 Adjacency SIDs
Certain SRv6 Endpoint behaviors [RFC8986] are associated with a Certain SRv6 Endpoint behaviors [RFC8986] are associated with a
particular adjacency. particular adjacency.
This document defines two new sub-TLVs of TLV 22, 23, 222, 223, and This document defines two new sub-TLVs of TLV 22, 23, 25, 141, 222,
141 - namely "SRv6 End.X SID sub-TLVs" and "SRv6 LAN End.X SID sub- and 223 - namely "SRv6 End.X SID sub-TLVs" and "SRv6 LAN End.X SID
TLVs". sub-TLVs".
IS-IS Neighbor advertisements are topology specific - but not IS-IS Neighbor advertisements are topology specific - but not
algorithm specific. SIDs advertised in SRv6 End.X SID and SRv6 LAN algorithm specific. SIDs advertised in SRv6 End.X SID and SRv6 LAN
End.X SID sub-TLVs therefore inherit the topology from the associated End.X SID sub-TLVs therefore inherit the topology from the associated
neighbor advertisement, but the algorithm is specified in the neighbor advertisement, but the algorithm is specified in the
individual SID. individual SID.
All SIDs advertised in SRv6 End.X SID and SRv6 LAN End.X SID sub-TLVs All SIDs advertised in SRv6 End.X SID and SRv6 LAN End.X SID sub-TLVs
MUST be a subnet of a Locator with matching topology and algorithm MUST be a subnet of a Locator with matching topology and algorithm
which is advertised by the same node in an SRv6 Locator TLV. SIDs which is advertised by the same node in an SRv6 Locator TLV. SIDs
skipping to change at page 13, line 39 skipping to change at page 13, line 39
Flags: 1 octet. Flags: 1 octet.
0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7
+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+
|B|S|P|Reserved | |B|S|P|Reserved |
+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+
where: where:
B-Flag: Backup flag. If set, the SID is eligible for B-Flag: Backup flag. If set, the SID is eligible for
protection (e.g., using IPFRR) as described in [RFC8355]. protection, e.g., using IP Fast Re-route (IPFRR) [RFC5286], as
described in [RFC8355].
S-Flag. Set flag. When set, the S-Flag indicates that the SID S-Flag. Set flag. When set, the S-Flag indicates that the SID
refers to a set of adjacencies (and therefore MAY be assigned refers to a set of adjacencies (and therefore MAY be assigned
to other adjacencies as well). to other adjacencies as well).
P-Flag. Persistent flag. When set, the P-Flag indicates that P-Flag. Persistent flag. When set, the P-Flag indicates that
the SID is persistently allocated, i.e., the SID value remains the SID is persistently allocated, i.e., the SID value remains
consistent across router restart and/or interface flap. consistent across router restart and/or interface flap.
Reserved bits: MUST be zero when originated and ignored when Reserved bits: MUST be zero when originated and MUST be ignored
received. when received.
Algorithm: 1 octet. As defined in [RFC8665]. Algorithm: 1 octet. As defined in IGP Algorithm Types registry
[RFC8665].
Weight: 1 octet. The value represents the weight of the SID for Weight: 1 octet. The value represents the weight of the SID for
the purpose of load balancing. The use of the weight is defined the purpose of load balancing. The use of the weight is defined
in [RFC8402]. in [RFC8402].
Endpoint Behavior: 2 octets. As defined in [RFC8986]. Supported Endpoint Behavior: 2 octets. As defined in [RFC8986]. Supported
behavior values for this sub-TLV are defined in Section 10 of this behavior values for this sub-TLV are defined in Section 10 of this
document. Unsupported or unrecognized behavior values are ignored document. Unsupported or unrecognized behavior values are ignored
by the receiver. by the receiver.
SID: 16 octets. This field encodes the advertised SRv6 SID. SID: 16 octets. This field encodes the advertised SRv6 SID.
Sub-sub-TLV-length: 1 octet. Number of octets used by sub-sub- Sub-sub-TLV-length: 1 octet. Number of octets used by sub-sub-
TLVs. TLVs.
Optional Sub-sub-TLVs: Supported Sub-sub-TLVs are specified in
Section 11.6. Any Sub-sub-TLV that is not allowed in SRv6 End.X
SID sub-TLV MUST be ignored.
Note that multiple TLVs for the same neighbor may be required in Note that multiple TLVs for the same neighbor may be required in
order to advertise all of the SRv6 SIDs associated with that order to advertise all the SRv6 SIDs associated with that neighbor.
neighbor.
8.2. SRv6 LAN End.X SID sub-TLV 8.2. SRv6 LAN End.X SID sub-TLV
This sub-TLV is used to advertise an SRv6 SID associated with a LAN This sub-TLV is used to advertise an SRv6 SID associated with a LAN
adjacency. Since the parent TLV is advertising an adjacency to the adjacency. Since the parent TLV is advertising an adjacency to the
Designated Intermediate System (DIS) for the LAN, it is necessary to Designated Intermediate System (DIS) for the LAN, it is necessary to
include the System ID of the physical neighbor on the LAN with which include the System ID of the physical neighbor on the LAN with which
the SRv6 SID is associated. Given that a large number of neighbors the SRv6 SID is associated. Given that many neighbors may exist on a
may exist on a given LAN a large number of SRv6 LAN END.X SID sub- given LAN, multiple SRv6 LAN END.X SID sub-TLVs may be associated
TLVs may be associated with the same LAN. Note that multiple TLVs with the same LAN. Note that multiple TLVs for the same DIS neighbor
for the same DIS neighbor may be required in order to advertise all may be required in order to advertise all the SRv6 SIDs associated
of the SRv6 SIDs associated with that neighbor. with that neighbor.
The SRv6 LAN End.X SID sub-TLV has the following format: The SRv6 LAN End.X SID sub-TLV has the following format:
0 1 2 3 0 1 2 3
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 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length | | | Type | Length | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |
| Neighbor System-ID (ID length octets) | | Neighbor System-ID (ID length octets) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
skipping to change at page 15, line 45 skipping to change at page 15, line 45
0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7
+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+
|B|S|P|Reserved | |B|S|P|Reserved |
+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+
where B,S, and P flags are as described in Section 8.1. where B,S, and P flags are as described in Section 8.1.
Reserved bits MUST be zero when originated and MUST be ignored Reserved bits MUST be zero when originated and MUST be ignored
when received. when received.
Algorithm: 1 octet. As defined in [RFC8665]. Algorithm: 1 octet. As defined in IGP Algorithm Types registry
[RFC8665].
Weight: 1 octet. The value represents the weight of the SID for Weight: 1 octet. The value represents the weight of the SID for
the purpose of load balancing. The use of the weight is defined the purpose of load balancing. The use of the weight is defined
in [RFC8402]. in [RFC8402].
Endpoint Behavior: 2 octets. As defined in [RFC8986]. Supported Endpoint Behavior: 2 octets. As defined in [RFC8986]. Supported
behavior values for this sub-TLV are defined in Section 10 of this behavior values for this sub-TLV are defined in Section 10 of this
document. Unsupported or unrecognized behavior values are ignored document. Unsupported or unrecognized behavior values are ignored
by the receiver. by the receiver.
SID: 16 octets. This field encodes the advertised SRv6 SID. SID: 16 octets. This field encodes the advertised SRv6 SID.
Sub-sub-TLV-length: 1 octet. Number of octets used by sub-sub- Sub-sub-TLV-length: 1 octet. Number of octets used by sub-sub-
TLVs. TLVs.
Optional Sub-sub-TLVs: Supported Sub-sub-TLVs are specified in
Section 11.6. Any Sub-sub-TLV that is not allowed in SRv6 LAN
End.X SID sub-TLV MUST be ignored.
Note that multiple TLVs for the same neighbor, on the same LAN, may
be required in order to advertise all the SRv6 SIDs associated with
that neighbor.
9. SRv6 SID Structure Sub-Sub-TLV 9. SRv6 SID Structure Sub-Sub-TLV
SRv6 SID Structure Sub-Sub-TLV is an optional Sub-Sub-TLV of: SRv6 SID Structure Sub-Sub-TLV is an optional Sub-Sub-TLV of:
SRv6 End SID Sub-TLV (Section 7.2) SRv6 End SID Sub-TLV (Section 7.2)
SRv6 End.X SID Sub-TLV (Section 8.1) SRv6 End.X SID Sub-TLV (Section 8.1)
SRv6 LAN End.X SID Sub-TLV (Section 8.2) SRv6 LAN End.X SID Sub-TLV (Section 8.2)
SRv6 SID Structure Sub-Sub-TLV is used to advertise the as defined in SRv6 SID Structure Sub-Sub-TLV is used to advertise the structure of
[RFC8986]. It has the following format: the SRv6 SID as defined in [RFC8986]. It has the following format:
0 1 2 3 0 1 2 3
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 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length | | Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LB Length | LN Length | Fun. Length | Arg. Length | | LB Length | LN Length | Fun. Length | Arg. Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
where: where:
skipping to change at page 17, line 6 skipping to change at page 17, line 18
Fun. Length: 1 octet. SRv6 SID Function length in bits. Fun. Length: 1 octet. SRv6 SID Function length in bits.
Arg. Length: 1 octet. SRv6 SID Arguments length in bits. Arg. Length: 1 octet. SRv6 SID Arguments length in bits.
ISIS SRv6 SID Structure Sub-Sub-TLV MUST NOT appear more than once in ISIS SRv6 SID Structure Sub-Sub-TLV MUST NOT appear more than once in
its parent Sub-TLV. If it appears more than once in its parent Sub- its parent Sub-TLV. If it appears more than once in its parent Sub-
TLV, the parent Sub-TLV MUST be ignored by the receiver. TLV, the parent Sub-TLV MUST be ignored by the receiver.
The sum of all four sizes advertised in ISIS SRv6 SID Structure Sub- The sum of all four sizes advertised in ISIS SRv6 SID Structure Sub-
Sub-TLV MUST be lower or equal to 128 bits. If the sum of all four Sub-TLV MUST be less than or equal to 128 bits. If the sum of all
sizes advertised in the ISIS SRv6 SID Structure Sub-Sub-TLV is larger four sizes advertised in the ISIS SRv6 SID Structure Sub-Sub-TLV is
than 128 bits, the parent Sub-TLV MUST be ignored by the receiver. larger than 128 bits, the parent Sub-TLV MUST be ignored by the
receiver.
The SRv6 SID Structure Sub-Sub-TLV indicates the structure of the SID The SRv6 SID Structure Sub-Sub-TLV indicates the structure of the SID
associated with it. It's usage is outside of the scope of this associated with it. Its usage is outside the scope of this document.
document.
10. Advertising Endpoint Behaviors 10. Advertising Endpoint Behaviors
Endpoint behaviors are defined in [RFC8986]. The codepoints for the Endpoint behaviors are defined in [RFC8986]. The codepoints for the
Endpoint behaviors are defined in the "SRv6 Endpoint Behaviors" Endpoint behaviors are defined in the "SRv6 Endpoint Behaviors"
registry defined in [RFC8986]. If this behavior is advertised it registry defined in [RFC8986]. If a behavior is advertised it MUST
MUST only be advertised in the TLV[s] as indicated by "Y" in the only be advertised in the TLV[s] as indicated by "Y" in the table
table below, and MUST NOT be advertised in the TLV[s] as indicated by below, and MUST NOT be advertised in the TLV[s] as indicated by "N"
"N" in the table below. in the table below.
Endpoint |Endpoint | End | End.X | Lan End.X | Endpoint |Endpoint | End | End.X | Lan End.X |
Behavior |Behavior Codepoint| SID | SID | SID | Behavior |Behavior Codepoint| SID | SID | SID |
----------------------|------------------|-----|-------|-----------| ----------------------|------------------|-----|-------|-----------|
End (PSP, USP, USD)| 1-4, 28-31 | Y | N | N | End (PSP, USP, USD)| 1-4, 28-31 | Y | N | N |
----------------------|------------------|-----|-------|-----------| ----------------------|------------------|-----|-------|-----------|
End.X (PSP, USP, USD)| 5-8, 32-35 | N | Y | Y | End.X (PSP, USP, USD)| 5-8, 32-35 | N | Y | Y |
----------------------|------------------|-----|-------|-----------| ----------------------|------------------|-----|-------|-----------|
End.DX6 | 16 | N | Y | Y | End.DX6 | 16 | N | Y | Y |
----------------------|------------------|-----|-------|-----------| ----------------------|------------------|-----|-------|-----------|
skipping to change at page 17, line 43 skipping to change at page 18, line 8
----------------------|------------------|-----|-------|-----------| ----------------------|------------------|-----|-------|-----------|
End.DT6 | 18 | Y | N | N | End.DT6 | 18 | Y | N | N |
----------------------|------------------|-----|-------|-----------| ----------------------|------------------|-----|-------|-----------|
End.DT4 | 19 | Y | N | N | End.DT4 | 19 | Y | N | N |
----------------------|------------------|-----|-------|-----------| ----------------------|------------------|-----|-------|-----------|
End.DT46 | 20 | Y | N | N | End.DT46 | 20 | Y | N | N |
11. IANA Considerations 11. IANA Considerations
This document requests allocation for the following TLVs, sub-TLVs, This document requests allocation for the following TLVs, sub-TLVs,
and sub-sub-TLVs as well updating the ISIS TLV registry and defining and sub-sub-TLVs as well as updating the ISIS TLV registry and
a new registry. defining new registries.
11.1. SRv6 Locator TLV 11.1. SRv6 Locator TLV
This document makes the following registrations in the the IS-IS TLV This document makes the following registrations in the IS-IS TLV
Codepoints registry. Codepoints registry.
Type Description IIH LSP SNP Purge Type Description IIH LSP SNP Purge
---- --------------------- --- --- --- ----- ---- --------------------- --- --- --- -----
27 SRv6 Locator TLV n y n n 27 SRv6 Locator TLV n y n n
11.1.1. SRv6 End SID sub-TLV 11.1.1. SRv6 End SID sub-TLV
The SRv6 Locator TLV shares sub-TLV space with TLVs 135, 235, 236 and The SRv6 Locator TLV shares sub-TLV space with TLVs 135, 235, 236 and
237. This document updates the "Sub-TLVs for TLVs 135, 235, 236, and 237. This document updates the "Sub-TLVs for TLVs 135, 235, 236, and
skipping to change at page 19, line 28 skipping to change at page 19, line 30
This document makes the following registrations in the "Sub-TLVs for This document makes the following registrations in the "Sub-TLVs for
TLV 242 (IS-IS Router CAPABILITY TLV)": TLV 242 (IS-IS Router CAPABILITY TLV)":
Type: 25 Type: 25
Description: SRv6 Capabilities sub-TLV. Description: SRv6 Capabilities sub-TLV.
Reference: This document (Section 2). Reference: This document (Section 2).
This document requests the creation of a new IANA managed registry, 11.3. Sub-Sub-TLVs of the SRv6 Capability sub-TLV
under "IS-IS TLV Codepoints" registry - sub-sub-TLVs of the SRv6
Capability sub-TLV. The registration procedure is "Expert Review" as This document requests a new IANA registry be created under the IS-IS
defined in [RFC8126]. Guidance for the Designated Experts is TLV Codepoints Registry to control the assignment of sub-TLV types
provided in the [RFC7370]. Suggested registry name is "sub-sub-TLVs for the SRv6 Capability sub-TLV specified in this document -
for SRv6 Capability sub-TLV". No sub-sub-TLVs are defined by this Section 2. The suggested name of the new registry is "sub-sub-TLVs
document except for the reserved value. of the SRv6 Capability sub-TLV". The registration procedure is
"Expert Review" as defined in [RFC8126]. Guidance for the Designated
Experts is provided in the [RFC7370]. No sub-sub-TLVs are defined by
this document except for the reserved value.
0: Reserved 0: Reserved
1-255: Unassigned 1-255: Unassigned
11.3. SRv6 End.X SID and SRv6 LAN End.X SID sub-TLVs 11.4. SRv6 End.X SID and SRv6 LAN End.X SID sub-TLVs
This document makes the following registrations in the "Sub-TLVs for This document makes the following registrations in the "Sub-TLVs for
TLVs 22, 23, 25, 141, 222, and 223 (Extended IS reachability, IS TLVs 22, 23, 25, 141, 222, and 223 (Extended IS reachability, IS
Neighbor Attribute, L2 Bundle Member Attributes, inter-AS Neighbor Attribute, L2 Bundle Member Attributes, inter-AS
reachability information, MT-ISN, and MT IS Neighbor Attribute TLVs)" reachability information, MT-ISN, and MT IS Neighbor Attribute TLVs)"
registry: registry:
Type: 43 Type: 43
Description: SRv6 End.X SID sub-TLV. Description: SRv6 End.X SID sub-TLV.
skipping to change at page 20, line 16 skipping to change at page 20, line 22
Description: SRv6 LAN End.X SID sub-TLV. Description: SRv6 LAN End.X SID sub-TLV.
Reference: This document (Section 8.2). Reference: This document (Section 8.2).
Type 22 23 25 141 222 223 Type 22 23 25 141 222 223
43 y y y y y y 43 y y y y y y
44 y y y y y y 44 y y y y y y
11.4. MSD Types 11.5. MSD Types
This document makes the following registrations in the IGP MSD-Types This document makes the following registrations in the IGP MSD-Types
registry: registry:
Value Name Reference Value Name Reference
------------------ ------------------
41 SRH Max SL [This Document] 41 SRH Max SL [This Document]
42 SRH Max End Pop [This Document] 42 SRH Max End Pop [This Document]
44 SRH Max H.encaps [This Document] 44 SRH Max H.encaps [This Document]
45 SRH Max End D [This Document] 45 SRH Max End D [This Document]
11.5. Sub-Sub-TLVs for SID Sub-TLVs 11.6. Sub-Sub-TLVs for SID Sub-TLVs
This document requests a new IANA registry be created under the IS-IS This document requests a new IANA registry be created under the IS-IS
TLV Codepoints Registry to control the assignment of sub-TLV types TLV Codepoints Registry to control the assignment of sub-TLV types
for the SID Sub-TLVs specified in this document - Section 7.2, for the SID Sub-TLVs specified in this document - Section 7.2,
Section 8.1, Section 8.2. The suggested name of the new registry is Section 8.1, Section 8.2. The suggested name of the new registry is
"sub-sub-TLVs for SRv6 End SID (5) (sub-TLV of TLVs 27, 135, 235, 236 "sub-sub-TLVs for SRv6 End SID (5) (sub-TLV of TLVs 27, 135, 235, 236
and 237) and SRv6 End.X SID (43)/SRv6 LAN End.X SID (44) (Sub-TLVs and 237) and SRv6 End.X SID (43)/SRv6 LAN End.X SID (44) (Sub-TLVs
for TLVs 22, 23, 25, 141, 222, and 223)". The registration procedure for TLVs 22, 23, 25, 141, 222, and 223)". The registration procedure
is "Expert Review" as defined in [RFC8126]. Guidance for the is "Expert Review" as defined in [RFC8126]. Guidance for the
Designated Experts is provided in [RFC7370]. The following Designated Experts is provided in [RFC7370]. The following
skipping to change at page 21, line 16 skipping to change at page 21, line 16
Reference Reference
--------------------------------------------------------- ---------------------------------------------------------
0 Reserved 0 Reserved
1 SRv6 SID Structure Sub-Sub-TLV [This Document] 1 SRv6 SID Structure Sub-Sub-TLV [This Document]
2-255 Unassigned 2-255 Unassigned
Type 5 43 44 Type 5 43 44
1 y y y 1 y y y
11.6. Prefix Attribute Flags Sub-TLV 11.7. Prefix Attribute Flags Sub-TLV
This document adds a new bit in the "Bit Values for Prefix Attribute This document adds a new bit in the "Bit Values for Prefix Attribute
Flags Sub-TLV" registry: Flags Sub-TLV" registry:
Bit #: 4 Bit #: 4
Description: Anycast Flag (A-flag) Description: Anycast Flag (A-flag)
Reference: This document (Section 6). Reference: This document (Section 6).
11.7. ISIS SRv6 Capabilities sub-TLV Flags Registry 11.8. ISIS SRv6 Capabilities sub-TLV Flags Registry
This document requests a new IANA registry be created under the IS-IS This document requests a new IANA registry be created under the IS-IS
TLV Codepoints Registry to control the assignment of bits in the TLV Codepoints Registry to control the assignment of bits 0 to 15 in
Flags field of the ISIS SRv6 Capabilities sub-TLV specified in this the Flags field of the ISIS SRv6 Capabilities sub-TLV specified in
document (Section 2). The suggested name of the new registry is this document (Section 2). The suggested name of the new registry is
"ISIS SRv6 Capabilities sub-TLV Flags". The registration procedure "ISIS SRv6 Capabilities sub-TLV Flags". The registration procedure
is "Expert Review" as defined in [RFC8126]. Guidance for the is "Expert Review" as defined in [RFC8126]. Guidance for the
Designated Experts is provided in [RFC7370]. The following Designated Experts is provided in [RFC7370]. The following
assignments are made by this document: assignments are made by this document:
Bit #: 1 Bit #: 1
Description: O-flag Description: O-flag
Reference: This document (Section 2). Reference: This document (Section 2).
11.8. ISIS SRv6 Locator TLV Flags Registry 11.9. ISIS SRv6 Locator TLV Flags Registry
This document requests a new IANA registry be created under the IS-IS This document requests a new IANA registry be created under the IS-IS
TLV Codepoints Registry to control the assignment of bits in the TLV Codepoints Registry to control the assignment of bits 0 to 7 in
Flags field of the ISIS SRv6 SRv6 Locator TLV specified in this the Flags field of the ISIS SRv6 Locator TLV specified in this
document (Section 7.1). The suggested name of the new registry is document (Section 7.1). The suggested name of the new registry is
"ISIS SRv6 Locator TLV Flags". The registration procedure is "Expert "ISIS SRv6 Locator TLV Flags". The registration procedure is "Expert
Review" as defined in [RFC8126]. Guidance for the Designated Experts Review" as defined in [RFC8126]. Guidance for the Designated Experts
is provided in [RFC7370]. The following assignments are made by this is provided in [RFC7370]. The following assignments are made by this
document: document:
Bit #: 0 Bit #: 0
Description: D-flag Description: D-flag
Reference: This document (Section 7.1). Reference: This document (Section 7.1).
11.9. ISIS SRv6 End SID sub-TLV Flags Registry 11.10. ISIS SRv6 End SID sub-TLV Flags Registry
This document requests a new IANA registry be created under the IS-IS This document requests a new IANA registry be created under the IS-IS
TLV Codepoints Registry to control the assignment of bits in the TLV Codepoints Registry to control the assignment of bits 0 to 7 in
Flags field of the ISIS SRv6 End SID sub-TLV specified in this the Flags field of the ISIS SRv6 End SID sub-TLV specified in this
document (Section 7.2). The suggested name of the new registry is document (Section 7.2). The suggested name of the new registry is
"ISIS SRv6 End SID sub-TLV Flags". The registration procedure is "ISIS SRv6 End SID sub-TLV Flags". The registration procedure is
"Expert Review" as defined in [RFC8126]. Guidance for the Designated "Expert Review" as defined in [RFC8126]. Guidance for the Designated
Experts is provided in [RFC7370]. No assignments are made by this Experts is provided in [RFC7370]. No assignments are made by this
document. document.
11.10. ISIS SRv6 End.X SID and LAN End.X SID sub-TLVs Flags Registry 11.11. ISIS SRv6 End.X SID and LAN End.X SID sub-TLVs Flags Registry
This document requests a new IANA registry be created under the IS-IS This document requests a new IANA registry be created under the IS-IS
TLV Codepoints Registry to control the assignment of bits in the TLV Codepoints Registry to control the assignment of bits 0 to 7 in
Flags field of the ISIS SRv6 End.X SID and LAN End.X SID sub-TLVs the Flags field of the ISIS SRv6 End.X SID and LAN End.X SID sub-TLVs
(Section 8.1 and Section 8.2). The suggested name of the new (Section 8.1 and Section 8.2). The suggested name of the new
registry is "ISIS SRv6 End.X SID and LAN End.X SID sub-TLVs Flags". registry is "ISIS SRv6 End.X SID and LAN End.X SID sub-TLVs Flags".
The registration procedure is "Expert Review" as defined in The registration procedure is "Expert Review" as defined in
[RFC8126]. Guidance for the Designated Experts is provided in [RFC8126]. Guidance for the Designated Experts is provided in
[RFC7370]. The following assignments are made by this document: [RFC7370]. The following assignments are made by this document:
Bit #: 0 Bit #: 0
Description: B-flag Description: B-flag
skipping to change at page 23, line 22 skipping to change at page 23, line 22
deployments, the stronger authentication mechanisms defined in the deployments, the stronger authentication mechanisms defined in the
aforementioned documents SHOULD be used. aforementioned documents SHOULD be used.
This document describes the IS-IS extensions required to support This document describes the IS-IS extensions required to support
Segment Routing over an IPv6 data plane. The security considerations Segment Routing over an IPv6 data plane. The security considerations
for Segment Routing are discussed in [RFC8402]. [RFC8986] defines for Segment Routing are discussed in [RFC8402]. [RFC8986] defines
the SRv6 Network Programming concept and specifies the main Segment the SRv6 Network Programming concept and specifies the main Segment
Routing behaviors to enable the creation of interoperable overlays; Routing behaviors to enable the creation of interoperable overlays;
the security considerations from that document apply too. the security considerations from that document apply too.
The advertisement of an incorrect MSD value may have negative The advertisement for an incorrect MSD value may have negative
consequences, see [RFC8491] for additional considerations. consequences, see [RFC8491] for additional considerations.
Security concerns associated with the setting of the O-flag are
described in [I-D.ietf-6man-spring-srv6-oam].
Security concerns associated with the usage of Flex-Algorithms are
described in [I-D.ietf-lsr-flex-algo]).
13. Contributors 13. Contributors
The following people gave a substantial contribution to the content The following people gave a substantial contribution to the content
of this document and should be considered as co-authors: of this document and should be considered as co-authors:
Stefano Previdi Stefano Previdi
Huawei Technologies Huawei Technologies
Email: stefano@previdi.net Email: stefano@previdi.net
Paul Wells Paul Wells
skipping to change at page 24, line 44 skipping to change at page 24, line 44
Robert Hanzl Robert Hanzl
Cisco Systems Cisco Systems
Millenium Plaza Building, V Celnici 10, Prague 1, Millenium Plaza Building, V Celnici 10, Prague 1,
Prague, Czech Republic Prague, Czech Republic
Email rhanzl@cisco.com Email rhanzl@cisco.com
Ketan Talaulikar Ketan Talaulikar
Cisco Systems, Inc. Cisco Systems, Inc.
Email: ketant@cisco.com Email: ketant@cisco.com
14. References 14. Acknowledgments
14.1. Normative References Thanks to Christian Hopps for his review comments and shepherd work.
Thanks to Alvaro Retana and John Scudder for AD review and comments.
15. References
15.1. Normative References
[I-D.ietf-6man-spring-srv6-oam] [I-D.ietf-6man-spring-srv6-oam]
Ali, Z., Filsfils, C., Matsushima, S., Voyer, D., and M. Ali, Z., Filsfils, C., Matsushima, S., Voyer, D., and M.
Chen, "Operations, Administration, and Maintenance (OAM) Chen, "Operations, Administration, and Maintenance (OAM)
in Segment Routing Networks with IPv6 Data plane (SRv6)", in Segment Routing Networks with IPv6 Data plane (SRv6)",
draft-ietf-6man-spring-srv6-oam-08 (work in progress), draft-ietf-6man-spring-srv6-oam-10 (work in progress),
October 2020. April 2021.
[I-D.ietf-lsr-flex-algo] [I-D.ietf-lsr-flex-algo]
Psenak, P., Hegde, S., Filsfils, C., Talaulikar, K., and Psenak, P., Hegde, S., Filsfils, C., Talaulikar, K., and
A. Gulko, "IGP Flexible Algorithm", draft-ietf-lsr-flex- A. Gulko, "IGP Flexible Algorithm", draft-ietf-lsr-flex-
algo-13 (work in progress), October 2020. algo-15 (work in progress), April 2021.
[ISO10589] [ISO10589]
International Organization for Standardization, International Organization for Standardization,
"Intermediate system to Intermediate system intra-domain "Intermediate system to Intermediate system intra-domain
routeing information exchange protocol for use in routeing information exchange protocol for use in
conjunction with the protocol for providing the conjunction with the protocol for providing the
connectionless-mode Network Service (ISO 8473)", Nov 2002. connectionless-mode Network Service (ISO 8473)", Nov 2002.
[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,
skipping to change at page 27, line 5 skipping to change at page 27, line 11
Matsushima, S., and D. Voyer, "IPv6 Segment Routing Header Matsushima, S., and D. Voyer, "IPv6 Segment Routing Header
(SRH)", RFC 8754, DOI 10.17487/RFC8754, March 2020, (SRH)", RFC 8754, DOI 10.17487/RFC8754, March 2020,
<https://www.rfc-editor.org/info/rfc8754>. <https://www.rfc-editor.org/info/rfc8754>.
[RFC8986] Filsfils, C., Ed., Camarillo, P., Ed., Leddy, J., Voyer, [RFC8986] Filsfils, C., Ed., Camarillo, P., Ed., Leddy, J., Voyer,
D., Matsushima, S., and Z. Li, "Segment Routing over IPv6 D., Matsushima, S., and Z. Li, "Segment Routing over IPv6
(SRv6) Network Programming", RFC 8986, (SRv6) Network Programming", RFC 8986,
DOI 10.17487/RFC8986, February 2021, DOI 10.17487/RFC8986, February 2021,
<https://www.rfc-editor.org/info/rfc8986>. <https://www.rfc-editor.org/info/rfc8986>.
14.2. Informative References 15.2. Informative References
[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>.
[RFC5304] Li, T. and R. Atkinson, "IS-IS Cryptographic [RFC5304] Li, T. and R. Atkinson, "IS-IS Cryptographic
Authentication", RFC 5304, DOI 10.17487/RFC5304, October Authentication", RFC 5304, DOI 10.17487/RFC5304, October
2008, <https://www.rfc-editor.org/info/rfc5304>. 2008, <https://www.rfc-editor.org/info/rfc5304>.
[RFC5310] Bhatia, M., Manral, V., Li, T., Atkinson, R., White, R., [RFC5310] Bhatia, M., Manral, V., Li, T., Atkinson, R., White, R.,
and M. Fanto, "IS-IS Generic Cryptographic and M. Fanto, "IS-IS Generic Cryptographic
Authentication", RFC 5310, DOI 10.17487/RFC5310, February Authentication", RFC 5310, DOI 10.17487/RFC5310, February
2009, <https://www.rfc-editor.org/info/rfc5310>. 2009, <https://www.rfc-editor.org/info/rfc5310>.
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