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
	skipping to change at page 2, line 4 ¶		skipping to change at page 2, line 4 ¶
	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
	skipping to change at page 2, line 26 ¶		skipping to change at page 2, line 26 ¶
	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
	skipping to change at page 3, line 36 ¶		skipping to change at page 3, line 38 ¶
	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.
	skipping to change at page 6, line 44 ¶		skipping to change at page 6, line 44 ¶
	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
	skipping to change at page 8, line 26 ¶		skipping to change at page 8, line 26 ¶
	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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