rfc9800.original   rfc9800.txt 
SPRING W. Cheng, Ed. Internet Engineering Task Force (IETF) W. Cheng, Ed.
Internet-Draft China Mobile Request for Comments: 9800 China Mobile
Updates: 8754 (if approved) C. Filsfils Updates: 8754 C. Filsfils
Intended status: Standards Track Cisco Systems, Inc. Category: Standards Track Cisco Systems, Inc.
Expires: 10 August 2025 Z. Li ISSN: 2070-1721 Z. Li
Huawei Technologies Huawei Technologies
B. Decraene B. Decraene
Orange Orange
F. Clad, Ed. F. Clad, Ed.
Cisco Systems, Inc. Cisco Systems, Inc.
6 February 2025 June 2025
Compressed SRv6 Segment List Encoding (CSID) Compressed SRv6 Segment List Encoding (CSID)
draft-ietf-spring-srv6-srh-compression-23
Abstract Abstract
Segment Routing over IPv6 (SRv6) is the instantiation of Segment Segment Routing over IPv6 (SRv6) is the instantiation of Segment
Routing (SR) on the IPv6 dataplane. This document specifies new Routing (SR) on the IPv6 data plane. This document specifies new
flavors for the SRv6 endpoint behaviors defined in RFC 8986, which flavors for the SRv6 endpoint behaviors defined in RFC 8986, which
enable the compression of an SRv6 segment list. Such compression enable the compression of an SRv6 segment list. Such compression
significantly reduces the size of the SRv6 encapsulation needed to significantly reduces the size of the SRv6 encapsulation needed to
steer packets over long segment lists. steer packets over long segment lists.
This document updates RFC 8754 by allowing a Segment List entry in This document updates RFC 8754 by allowing a Segment List entry in
the Segment Routing Header (SRH) to be either an IPv6 address, as the Segment Routing Header (SRH) to be either an IPv6 address, as
specified in RFC 8754, or a REPLACE-CSID container in packed format, specified in RFC 8754, or a REPLACE-CSID container in packed format,
as specified in this document. as specified in this document.
Status of This Memo Status of This Memo
This Internet-Draft is submitted in full conformance with the This is an Internet Standards Track document.
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
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Internet-Drafts are draft documents valid for a maximum of six months This document is a product of the Internet Engineering Task Force
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Internet Standards is available in Section 2 of RFC 7841.
This Internet-Draft will expire on 10 August 2025. Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
https://www.rfc-editor.org/info/rfc9800.
Copyright Notice Copyright Notice
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Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 4 1. Introduction
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4 2. Terminology
2.1. Requirements Language . . . . . . . . . . . . . . . . . . 6 2.1. Requirements Language
3. Basic Concepts . . . . . . . . . . . . . . . . . . . . . . . 6 3. Basic Concepts
4. SR Segment Endpoint Flavors . . . . . . . . . . . . . . . . . 6 4. SR Segment Endpoint Flavors
4.1. NEXT-CSID Flavor . . . . . . . . . . . . . . . . . . . . 8 4.1. NEXT-CSID Flavor
4.1.1. End with NEXT-CSID . . . . . . . . . . . . . . . . . 10 4.1.1. End with NEXT-CSID
4.1.2. End.X with NEXT-CSID . . . . . . . . . . . . . . . . 11 4.1.2. End.X with NEXT-CSID
4.1.3. End.T with NEXT-CSID . . . . . . . . . . . . . . . . 12 4.1.3. End.T with NEXT-CSID
4.1.4. End.B6.Encaps with NEXT-CSID . . . . . . . . . . . . 12 4.1.4. End.B6.Encaps with NEXT-CSID
4.1.5. End.B6.Encaps.Red with NEXT-CSID . . . . . . . . . . 13 4.1.5. End.B6.Encaps.Red with NEXT-CSID
4.1.6. End.BM with NEXT-CSID . . . . . . . . . . . . . . . . 13 4.1.6. End.BM with NEXT-CSID
4.1.7. Combination with PSP, USP and USD flavors . . . . . . 14 4.1.7. Combination with PSP, USP, and USD Flavors
4.2. REPLACE-CSID Flavor . . . . . . . . . . . . . . . . . . . 14 4.2. REPLACE-CSID Flavor
4.2.1. End with REPLACE-CSID . . . . . . . . . . . . . . . . 19 4.2.1. End with REPLACE-CSID
4.2.2. End.X with REPLACE-CSID . . . . . . . . . . . . . . . 21 4.2.2. End.X with REPLACE-CSID
4.2.3. End.T with REPLACE-CSID . . . . . . . . . . . . . . . 21 4.2.3. End.T with REPLACE-CSID
4.2.4. End.B6.Encaps with REPLACE-CSID . . . . . . . . . . . 22 4.2.4. End.B6.Encaps with REPLACE-CSID
4.2.5. End.B6.Encaps.Red with REPLACE-CSID . . . . . . . . . 22 4.2.5. End.B6.Encaps.Red with REPLACE-CSID
4.2.6. End.BM with REPLACE-CSID . . . . . . . . . . . . . . 23 4.2.6. End.BM with REPLACE-CSID
4.2.7. End.DX and End.DT with REPLACE-CSID . . . . . . . . . 23 4.2.7. End.DX and End.DT with REPLACE-CSID
4.2.8. Combination with PSP, USP, and USD flavors . . . . . 24 4.2.8. Combination with PSP, USP, and USD Flavors
5. CSID Allocation . . . . . . . . . . . . . . . . . . . . . . . 24 5. CSID Allocation
5.1. Global CSID . . . . . . . . . . . . . . . . . . . . . . . 25 5.1. Global CSID
5.2. Local CSID . . . . . . . . . . . . . . . . . . . . . . . 25 5.2. Local CSID
5.3. Recommended Installation of CSIDs in FIB . . . . . . . . 25 5.3. Recommended Installation of CSIDs in FIB
6. SR Source Node . . . . . . . . . . . . . . . . . . . . . . . 27 6. SR Source Node
6.1. SID Validation for Compression . . . . . . . . . . . . . 27 6.1. SID Validation for Compression
6.2. Segment List Compression . . . . . . . . . . . . . . . . 27 6.2. Segment List Compression
6.3. Rules for segment lists containing NEXT-CSID flavor 6.3. Rules for Segment Lists Containing NEXT-CSID Flavor SIDs
SIDs . . . . . . . . . . . . . . . . . . . . . . . . . . 31 6.4. Rules for Segment Lists Containing REPLACE-CSID Flavor SIDs
6.5. Upper-Layer Checksums
6.4. Rules for segment lists containing REPLACE-CSID flavor 7. Inter-Domain Compression
SIDs . . . . . . . . . . . . . . . . . . . . . . . . . . 32 7.1. End.LBS: Locator-Block Swap
6.5. Upper-Layer Checksums . . . . . . . . . . . . . . . . . . 33 7.1.1. End.LBS with NEXT-CSID
7. Inter-Domain Compression . . . . . . . . . . . . . . . . . . 33 7.1.2. End.LBS with REPLACE-CSID
7.1. End.LBS: Locator-Block Swap . . . . . . . . . . . . . . . 33 7.2. End.XLBS: L3 Cross-Connect and Locator-Block Swap
7.1.1. End.LBS with NEXT-CSID . . . . . . . . . . . . . . . 34 7.2.1. End.XLBS with NEXT-CSID
7.1.2. End.LBS with REPLACE-CSID . . . . . . . . . . . . . . 34 7.2.2. End.XLBS with REPLACE-CSID
7.2. End.XLBS: L3 Cross-Connect and Locator-Block Swap . . . . 35 8. Control Plane
7.2.1. End.XLBS with NEXT-CSID . . . . . . . . . . . . . . . 35 9. Operational Considerations
7.2.2. End.XLBS with REPLACE-CSID . . . . . . . . . . . . . 36 9.1. Flavor, Block, and CSID Length
8. Control Plane . . . . . . . . . . . . . . . . . . . . . . . . 36 9.2. GIB/LIB Usage
9. Operational Considerations . . . . . . . . . . . . . . . . . 38 9.3. Pinging a SID
9.1. Flavor, Block, and CSID Length . . . . . . . . . . . . . 38 9.4. ICMP Error Processing
9.2. GIB/LIB Usage . . . . . . . . . . . . . . . . . . . . . . 38 10. Applicability to Other SRv6 Endpoint Behaviors
9.3. Pinging a SID . . . . . . . . . . . . . . . . . . . . . . 39 11. Security Considerations
9.4. ICMP Error Processing . . . . . . . . . . . . . . . . . . 40 12. IANA Considerations
10. Implementation Status . . . . . . . . . . . . . . . . . . . . 41 12.1. SRv6 Endpoint Behaviors
10.1. Cisco Systems . . . . . . . . . . . . . . . . . . . . . 41 13. References
10.2. Huawei Technologies . . . . . . . . . . . . . . . . . . 42 13.1. Normative References
10.3. Nokia . . . . . . . . . . . . . . . . . . . . . . . . . 43 13.2. Informative References
10.4. Arrcus . . . . . . . . . . . . . . . . . . . . . . . . . 43 Appendix A. Complete Pseudocodes
10.5. Juniper Networks . . . . . . . . . . . . . . . . . . . . 44 A.1. End with NEXT-CSID
10.6. Marvell . . . . . . . . . . . . . . . . . . . . . . . . 44 A.2. End.X with NEXT-CSID
10.7. Broadcom . . . . . . . . . . . . . . . . . . . . . . . . 44 A.3. End.T with NEXT-CSID
10.8. ZTE Corporation . . . . . . . . . . . . . . . . . . . . 45 A.4. End.B6.Encaps with NEXT-CSID
10.9. New H3C Technologies . . . . . . . . . . . . . . . . . . 45 A.5. End.BM with NEXT-CSID
10.10. Ruijie Network . . . . . . . . . . . . . . . . . . . . . 45 A.6. End with REPLACE-CSID
10.11. Ciena . . . . . . . . . . . . . . . . . . . . . . . . . 46 A.7. End.X with REPLACE-CSID
10.12. Centec . . . . . . . . . . . . . . . . . . . . . . . . . 46 A.8. End.T with REPLACE-CSID
10.13. Open-Source . . . . . . . . . . . . . . . . . . . . . . 46 A.9. End.B6.Encaps with REPLACE-CSID
10.14. Interoperability Reports . . . . . . . . . . . . . . . . 47 A.10. End.BM with REPLACE-CSID
10.14.1. EANTC 2024 . . . . . . . . . . . . . . . . . . . . 47 Acknowledgements
10.14.2. Bell Canada / Ciena 2023 . . . . . . . . . . . . . 47 Contributors
10.14.3. EANTC 2023 . . . . . . . . . . . . . . . . . . . . 47 Authors' Addresses
10.14.4. China Mobile 2020 . . . . . . . . . . . . . . . . . 48
11. Applicability to other SRv6 Endpoint Behaviors . . . . . . . 49
12. Security Considerations . . . . . . . . . . . . . . . . . . . 49
13. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 50
13.1. SRv6 Endpoint Behaviors . . . . . . . . . . . . . . . . 51
14. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 54
15. References . . . . . . . . . . . . . . . . . . . . . . . . . 54
15.1. Normative References . . . . . . . . . . . . . . . . . . 54
15.2. Informative References . . . . . . . . . . . . . . . . . 55
Appendix A. Complete pseudocodes . . . . . . . . . . . . . . . . 58
A.1. End with NEXT-CSID . . . . . . . . . . . . . . . . . . . 58
A.2. End.X with NEXT-CSID . . . . . . . . . . . . . . . . . . 60
A.3. End.T with NEXT-CSID . . . . . . . . . . . . . . . . . . 62
A.4. End.B6.Encaps with NEXT-CSID . . . . . . . . . . . . . . 64
A.5. End.BM with NEXT-CSID . . . . . . . . . . . . . . . . . . 66
A.6. End with REPLACE-CSID . . . . . . . . . . . . . . . . . . 68
A.7. End.X with REPLACE-CSID . . . . . . . . . . . . . . . . . 70
A.8. End.T with REPLACE-CSID . . . . . . . . . . . . . . . . . 72
A.9. End.B6.Encaps with REPLACE-CSID . . . . . . . . . . . . . 74
A.10. End.BM with REPLACE-CSID . . . . . . . . . . . . . . . . 75
Contributors . . . . . . . . . . . . . . . . . . . . . . . . . . 77
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 78
1. Introduction 1. Introduction
The Segment Routing (SR) architecture [RFC8402] describes two data The Segment Routing (SR) architecture [RFC8402] describes two data
plane instantiations of SR: SR over MPLS (SR-MPLS) and SR over IPv6 plane instantiations of SR: SR over MPLS (SR-MPLS) and SR over IPv6
(SRv6). (SRv6).
SRv6 Network Programming [RFC8986] builds upon the IPv6 Segment SRv6 Network Programming [RFC8986] builds upon the IPv6 Segment
Routing Header (SRH) [RFC8754] to define a framework for constructing Routing Header (SRH) [RFC8754] to define a framework for constructing
a network program with topological and service segments. a network program with topological and service segments.
Some SRv6 applications such as strict path traffic engineering may Some SRv6 applications, such as strict path traffic engineering, may
require long segment lists. Compressing the encoding of these long require long segment lists. Compressing the encoding of these long
segment lists in the packet header can significantly reduce the segment lists in the packet header can significantly reduce the
header size. This document specifies new flavors to the SRv6 header size. This document specifies new flavors to the SRv6
endpoint behaviors defined in [RFC8986] that enable a compressed endpoint behaviors defined in [RFC8986] that enable a compressed
encoding of the SRv6 segment list. This document also specifies new encoding of the SRv6 segment list. This document also specifies new
SRv6 endpoint behaviors to preserve the compression efficiency in SRv6 endpoint behaviors to preserve the compression efficiency in
multi-domain environments. multi-domain environments.
The SRv6 endpoint behaviors defined in this document leverage the The SRv6 endpoint behaviors defined in this document leverage the
SRv6 data plane defined in [RFC8754] and [RFC8986], and are SRv6 data plane defined in [RFC8754] and [RFC8986]; the behaviors are
compatible with the SRv6 control plane extensions for IS-IS compatible with the SRv6 control plane extensions for IS-IS
[RFC9352], OSPF [RFC9513], and BGP [RFC9252]. [RFC9352], OSPF [RFC9513], and BGP [RFC9252].
This document updates [RFC8754] by allowing a Segment List entry in This document updates [RFC8754] by allowing a Segment List entry in
the SRH to be either an IPv6 address, as specified in [RFC8754], or a the SRH to be either an IPv6 address, as specified in [RFC8754], or a
REPLACE-CSID container in packed format, as specified in Section 4.2. REPLACE-CSID container in packed format, as specified in Section 4.2.
2. Terminology 2. Terminology
This document leverages the terms defined in [RFC8402], [RFC8754], This document leverages the terms defined in [RFC8402], [RFC8754],
and [RFC8986], in particular segment, segment list, Segment and [RFC8986], in particular segment, segment list, Segment
Identifier (SID), SID list, SR policy, prefix segment, adjacency Identifier (SID), SID list, SR policy, prefix segment, adjacency
segment, SRH, SR domain, SR source node, SR segment endpoint node, segment, SRH, SR domain, SR source node, SR segment endpoint node,
transit node, SRv6 endpoint behavior, flavor, SID block, locator, transit node, SRv6 endpoint behavior, flavor, SID block, locator,
function, and argument. The reader is assumed to be familiar with function, and argument. The reader is assumed to be familiar with
this terminology. this terminology.
This document introduces the following new terms: This document introduces the following new terms:
* Locator-Block: The most significant bits of a SID locator that Locator-Block: The most significant bits of a SID locator that
represent the SRv6 SID block. The Locator-Block is referred to as represent the SRv6 SID block. The Locator-Block is referred to as
"B" in Section 3.1 of [RFC8986]. "B" in Section 3.1 of [RFC8986].
* Locator-Node: The least significant bits of a SID locator that Locator-Node: The least significant bits of a SID locator that
identify the SR segment endpoint node instantiating the SID. The identify the SR segment endpoint node instantiating the SID. The
Locator-Node is referred to as "N" in Section 3.1 of [RFC8986]. Locator-Node is referred to as "N" in Section 3.1 of [RFC8986].
* Compressed-SID (CSID): A compressed encoding of a SID. The CSID Compressed-SID (CSID): A compressed encoding of a SID. The CSID
includes the Locator-Node and Function bits of the SID being includes the Locator-Node and Function bits of the SID being
compressed. If either constituent of the SID is empty (zero compressed. If either constituent of the SID is empty (zero
length), then the same applies to its CSID encoding. length), then the same applies to its CSID encoding.
* CSID container: A 128-bit IPv6 address that functions as a CSID container: A 128-bit IPv6 address that functions as a container
container holding a list of one or more CSIDs, and the Argument holding a list of one or more CSIDs and the Argument (if any) of
(if any) of the last CSID. the last CSID.
* CSID sequence: A group of one or more consecutive SID list entries CSID sequence: A group of one or more consecutive SID list entries
encoding the common Locator-Block and at least one CSID container. encoding the common Locator-Block and at least one CSID container.
* Compressed SID list: A segment list encoding that reduces the Compressed SID list: A segment list encoding that reduces the packet
packet header length thanks to one or more CSID sequences. A header length thanks to one or more CSID sequences. A compressed
compressed SID list also contains zero, one, or more uncompressed SID list also contains zero, one, or more uncompressed SIDs.
SIDs.
* Global Identifiers Block (GIB): The pool of CSID values available Global Identifiers Block (GIB): The pool of CSID values available
for global allocation. for global allocation.
* Local Identifiers Block (LIB): The pool of CSID values available Local Identifiers Block (LIB): The pool of CSID values available for
for local allocation. local allocation.
In this document, the length of each constituent part of a SID is In this document, the length of each constituent part of a SID is
referred to as follows. referred to as follows:
* LBL is the Locator-Block length of the SID. * LBL is the Locator-Block length of the SID.
* LNL is the Locator-Node length of the SID. * LNL is the Locator-Node length of the SID.
* FL is the Function length of the SID. * FL is the Function length of the SID.
* AL is the Argument length of the SID. * AL is the Argument length of the SID.
In addition, the Locator-Node and Function length (LNFL) is the sum In addition, the Locator-Node and Function length (LNFL) is the sum
of the Locator-Node length and the Function length of the SID. It is of the Locator-Node length and the Function length of the SID. It is
also referred to as the CSID length. also referred to as the "CSID length".
2.1. Requirements Language 2.1. Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in BCP "OPTIONAL" in this document are to be interpreted as described in
14 [RFC2119] [RFC8174] when, and only when, they appear in all BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here. capitals, as shown here.
3. Basic Concepts 3. Basic Concepts
In an SR domain, all SRv6 SIDs instantiated from the same Locator- In an SR domain, all SRv6 SIDs instantiated from the same Locator-
Block share the same most significant bits. In addition, when the Block share the same most significant bits. In addition, when the
combined length of the SRv6 SID Locator, Function, and Argument is combined length of the SRv6 SID Locator, Function, and Argument is
smaller than 128 bits, the least significant bits of the SID are smaller than 128 bits, the least significant bits of the SID are
padded with zeros. The compressed segment list encoding seeks to padded with zeros. The compressed segment list encoding seeks to
decrease the packet header length by avoiding the repetition of the decrease the packet header length by avoiding the repetition of the
same Locator-Block and reducing the use of padding bits. same Locator-Block and reducing the use of padding bits.
Building upon and fully compatible with the mechanisms specified in Building upon, and fully compatible with, the mechanisms specified in
[RFC8754] and [RFC8986], the compressed segment list encoding [RFC8754] and [RFC8986], the compressed segment list encoding
leverages a SID list compression logic at the SR source node (see leverages a SID list compression logic at the SR source node (see
Section 6) in combination with new flavors of the SRv6 endpoint Section 6) in combination with new flavors of the SRv6 endpoint
behaviors that process the compressed SID list (see Section 4). behaviors that process the compressed SID list (see Section 4).
An SR source node constructs and compresses the SID list depending on An SR source node constructs and compresses the SID list depending on
the SIDs instantiated on each SR segment endpoint node that the the SIDs instantiated on each SR segment endpoint node that the
packet is intended to traverse, as well as its own compression packet is intended to traverse, as well as its own compression
capabilities. The resulting compressed SID list is a combination of capabilities. The resulting compressed SID list is a combination of
CSID sequences, for the SIDs that the SR source node was able to CSID sequences, for the SIDs that the SR source node was able to
compress, and uncompressed SIDs, which could not be compressed. In compress, and uncompressed SIDs, which could not be compressed. In
case the SR source node is able to compress all the SIDs in the SID case the SR source node is able to compress all the SIDs in the SID
list, the compressed SID list comprises only CSID sequences (one or list, the compressed SID list comprises only CSID sequences (one or
more), and no uncompressed SIDs. Conversely, the compressed SID list more) and no uncompressed SIDs. Conversely, the compressed SID list
comprises only uncompressed SIDs when the SR source is unable to comprises only uncompressed SIDs when the SR source is unable to
compress any of the constituent SIDs. compress any of the constituent SIDs.
4. SR Segment Endpoint Flavors 4. SR Segment Endpoint Flavors
This section defines two SR segment endpoint flavors, NEXT-CSID and This section defines two SR segment endpoint flavors: NEXT-CSID and
REPLACE-CSID, for the End, End.X, End.T, End.B6.Encaps, REPLACE-CSID, for the End, End.X, End.T, End.B6.Encaps,
End.B6.Encaps.Red, and End.BM behaviors of [RFC8986]. End.B6.Encaps.Red, and End.BM behaviors of [RFC8986].
This section also defines a REPLACE-CSID flavor for the End.DX6, This section also defines a REPLACE-CSID flavor for the End.DX6,
End.DX4, End.DT6, End.DT4, End.DT46, End.DX2, End.DX2V, End.DT2U, and End.DX4, End.DT6, End.DT4, End.DT46, End.DX2, End.DX2V, End.DT2U, and
End.DT2M behaviors of [RFC8986]. A counterpart NEXT-CSID flavor is End.DT2M behaviors of [RFC8986]. A counterpart NEXT-CSID flavor is
not defined for these behaviors: since any SID can be the last not defined for these behaviors. Any SID can be the last element of
element of a CSID sequence compressed using the NEXT-CSID flavor (see a CSID sequence compressed using the NEXT-CSID flavor (see
Section 4.1) and the aforementioned SRv6 endpoint behaviors are Section 4.1) and the aforementioned SRv6 endpoint behaviors are
always in the last position in a SID list, there is no need for any always in the last position in a SID list; thus, there is no need for
modification of the behaviors defined in [RFC8986]. any modification of the behaviors defined in [RFC8986].
Future documents may extend the applicability of the NEXT-CSID and Future documents may extend the applicability of the NEXT-CSID and
REPLACE-CSID flavors to other SRv6 endpoint behaviors (see REPLACE-CSID flavors to other SRv6 endpoint behaviors (see
Section 11). Section 10).
The use of these flavors, either individually or in combination, The use of these flavors, either individually or in combination,
enables the compressed segment list encoding. enables the compressed segment list encoding.
The NEXT-CSID flavor and the REPLACE-CSID flavor both leverage the The NEXT-CSID flavor and the REPLACE-CSID flavor both leverage the
SID Argument to determine the next SID to be processed, but employ SID Argument to determine the next SID to be processed, but employ
different SID list compression schemes. With the NEXT-CSID flavor, different SID list compression schemes. With the NEXT-CSID flavor,
each CSID container is a fully formed SRv6 SID with the common each CSID container is a fully formed SRv6 SID with the common
Locator-Block for all the CSIDs in the CSID container, a Locator-Node Locator-Block for all the CSIDs in the CSID container, a Locator-
and Function that are those of the first CSID, and an Argument Node, and Function that are those of the first CSID, and an Argument
carrying the subsequent CSIDs. With the REPLACE-CSID flavor, only carrying the subsequent CSIDs. With the REPLACE-CSID flavor, only
the first element in a CSID sequence is a fully formed SRv6 SID. It the first element in a CSID sequence is a fully formed SRv6 SID. It
has the common Locator-Block for all the CSIDs in the CSID sequence, has the common Locator-Block for all the CSIDs in the CSID sequence,
and a Locator-Node and Function that are those of the first CSID. and a Locator-Node and Function that are those of the first CSID.
The remaining elements in the CSID sequence are CSID containers The remaining elements in the CSID sequence are CSID containers
carrying the subsequent CSIDs without the Locator-Block. carrying the subsequent CSIDs without the Locator-Block.
Regardless of which flavor is used, the IPv6 address carried in the Regardless of which flavor is used, the IPv6 address carried in the
Destination Address field of the IPv6 header is a valid SRv6 SID Destination Address field of the IPv6 header is a valid SRv6 SID
conforming to [RFC9602]. conforming to [RFC9602].
In the remainder of this document, the term "a SID of this document" In the remainder of this document, the term "a SID of this document"
refers to any End, End.X, End.T, End.B6.Encaps, End.B6.Encaps.Red, or refers to any End, End.X, End.T, End.B6.Encaps, End.B6.Encaps.Red, or
End.BM SID with the NEXT-CSID or the REPLACE-CSID flavor, and with End.BM SID with the NEXT-CSID or the REPLACE-CSID flavor and with any
any combination of Penultimate Segment Pop (PSP), Ultimate Segment combination of Penultimate Segment Pop (PSP), Ultimate Segment Pop
Pop (USP), and Ultimate Segment Decapsulation (USD) flavor, or any (USP), and Ultimate Segment Decapsulation (USD) flavor, or any
End.DX6, End.DX4, End.DT6, End.DT4, End.DT46, End.DX2, End.DX2V, End.DX6, End.DX4, End.DT6, End.DT4, End.DT46, End.DX2, End.DX2V,
End.DT2U, or End.DT2M with the REPLACE-CSID flavor. All the SRv6 End.DT2U, or End.DT2M with the REPLACE-CSID flavor. All the SRv6
endpoint behaviors introduced in this document are listed in Table 1 endpoint behaviors introduced in this document are listed in Table 1.
at the end of the document.
In the remainder of this document, the terms "NEXT-CSID flavor SID" In the remainder of this document, the terms "NEXT-CSID flavor SID"
and "REPLACE-CSID flavor SID" refer to any SID of this document with and "REPLACE-CSID flavor SID" refer to any SID of this document with
the NEXT-CSID flavor and with the REPLACE-CSID flavor, respectively. the NEXT-CSID flavor and with the REPLACE-CSID flavor, respectively.
4.1. NEXT-CSID Flavor 4.1. NEXT-CSID Flavor
A CSID sequence compressed using the mechanism of the NEXT-CSID A CSID sequence compressed using the mechanism of the NEXT-CSID
flavor comprises one or more CSID containers. Each CSID container is flavor comprises one or more CSID containers. Each CSID container is
a fully formed 128-bit SID structured as shown in Figure 1. It a fully formed 128-bit SID structured as shown in Figure 1. It
carries a Locator-Block followed by a series of CSIDs. The Locator- carries a Locator-Block followed by a series of CSIDs. The Locator-
Node and Function of the CSID container are those of the first CSID, Node and Function of the CSID container are those of the first CSID,
and its Argument is the contiguous series of subsequent CSIDs. The and its Argument is the contiguous series of subsequent CSIDs. The
second CSID is encoded in the most significant bits of the CSID second CSID is encoded in the most significant bits of the CSID
container Argument, the third CSID is encoded in the bits of the container Argument. The third CSID is encoded in the bits of the
Argument that immediately follow the second CSID, and so on. When Argument that immediately follow the second CSID, and so on. When
all CSIDs have the same length, a CSID container can carry up to K all CSIDs have the same length, a CSID container can carry up to K
CSIDs, where K is computed as floor((128-LBL)/LNFL) (floor(x) is the CSIDs, where K is computed as floor((128-LBL)/LNFL) (floor(x) is the
greatest integer less than or equal to x [GKP94]). Each CSID greatest integer less than or equal to x [GKP94]). Each CSID
container for NEXT-CSID is independent, such that contiguous CSID container for NEXT-CSID is independent, such that contiguous CSID
containers in a CSID sequence can be considered as separate CSID containers in a CSID sequence can be considered to be separate CSID
sequences. sequences.
When a CSID sequence compressed using the NEXT-CSID flavor comprises When a CSID sequence compressed using the NEXT-CSID flavor comprises
at least two CSIDs, the last CSID in the sequence is not required to at least two CSIDs, the last CSID in the sequence is not required to
have the NEXT-CSID flavor. It can be bound to any SRv6 endpoint have the NEXT-CSID flavor. It can be bound to any SRv6 endpoint
behavior, including [RFC8986] behaviors and REPLACE-CSID flavor, as behavior, including [RFC8986] behaviors and REPLACE-CSID flavor, as
long as the updated destination address resulting from the processing long as the updated destination address resulting from the processing
of the previous CSID in the sequence is a valid form for that last of the previous CSID in the sequence is a valid form for that last
SID. Line S12 of the first pseudocode in Section 6.2 provides SID. Line S12 of the first pseudocode in Section 6.2 provides
sufficient conditions to ensure this property. sufficient conditions to ensure this property.
+------------------------------------------------------------------+ +------------------------------------------------------------------+
| Locator-Block |Loc-Node| Argument | | Locator-Block |Loc-Node| Argument |
| |Function| | | |Function| |
+------------------------------------------------------------------+ +------------------------------------------------------------------+
<----------------------> <------> <------------------------------> <----------------------> <------> <------------------------------>
LBL LNFL AL LBL LNFL AL
Figure 1: Structure of a NEXT-CSID flavor SID (scaled for a Figure 1: Structure of a NEXT-CSID Flavor SID (Scaled for a
48-bit Locator- Block, 16-bit combined Locator-Node and Function, 48-Bit Locator- Block, 16-Bit Combined Locator-Node and Function,
and 64-bit Argument) and 64-Bit Argument)
Figure 2 illustrates a compressed SID list as could be produced by an Figure 2 illustrates a compressed SID list as could be produced by an
SR source node steering a packet into an SR policy with a SID list of SR source node steering a packet into an SR policy with a SID list of
eight NEXT-CSID flavor SIDs. All SIDs in this example have a 48-bit eight NEXT-CSID flavor SIDs. All SIDs in this example have a 48-bit
Locator-Block, 16-bit combined Locator-Node and Function, and 64-bit Locator-Block, 16-bit combined Locator-Node and Function, and 64-bit
Argument. The SR source node compresses the SR policy SID list as a Argument. The SR source node compresses the SR policy SID list as a
compressed SID list of two CSID containers. The first CSID container compressed SID list of two CSID containers. The first CSID container
carries a Locator-Block and the first five CSIDs. The second CSID carries a Locator-Block and the first five CSIDs. The second CSID
container carries a Locator-Block and the sixth, seventh, and eighth container carries a Locator-Block and the sixth, seventh, and eighth
CSIDs. Since the SR source node does not use the second CSID CSIDs. Since the SR source node does not use the second CSID
container at full capacity, it sets the 32 least significant bits to container at full capacity, it sets the 32 least significant bits to
zero. The SR source node sets the IPv6 Destination Address (DA) with zero. The SR source node sets the IPv6 Destination Address (DA) with
the value of the first CSID container and the first element of the the value of the first CSID container and the first element of the
SRH Segment List with the value of the second CSID container. SRH Segment List with the value of the second CSID container.
Without reduced SRH (Section 4.1.1 of [RFC8754]), the SR source node Without reduced SRH (see Section 4.1.1 of [RFC8754]), the SR source
also writes the first CSID container as the second element of the SRH node also writes the first CSID container as the second element of
Segment List. the SRH Segment List.
Note that the CSIDs within a given CSID container appear in forward Note that the CSIDs within a given CSID container appear in forward
order to leverage the longest-prefix match IP forwarding, while the order to leverage the longest-prefix match IP forwarding, while the
entries in the SRH Segment List appear in reversed order of their entries in the SRH Segment List appear in reversed order of their
processing, as specified in Section 4.1 of [RFC8754]. processing, as specified in Section 4.1 of [RFC8754].
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | | |
+ Locator-Block +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + Locator-Block +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | 1st CSID | | | 1st CSID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 2nd CSID | 3rd CSID | | 2nd CSID | 3rd CSID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 4th CSID | 5th CSID | | 4th CSID | 5th CSID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
First CSID container First CSID Container
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | | |
+ Locator-Block +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + Locator-Block +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | 6th CSID | | | 6th CSID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 7th CSID | 8th CSID | | 7th CSID | 8th CSID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 0 | | 0 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Second CSID container Second CSID Container
Figure 2: Compressed SID list of eight NEXT-CSID flavor SIDs with Figure 2: Compressed SID List of Eight NEXT-CSID Flavor SIDs with
a 48-bit Locator-Block, 16-bit combined Locator-Node and a 48-Bit Locator-Block, 16-Bit Combined Locator-Node and
Function, and 64-bit Argument Function, and 64-Bit Argument
An implementation MUST support a 32-bit Locator-Block length (LBL) An implementation MUST support a 32-bit Locator-Block length (LBL)
and a 16-bit CSID length (LNFL) for NEXT-CSID flavor SIDs, and MAY and a 16-bit CSID length (LNFL) for NEXT-CSID flavor SIDs, and it MAY
support any additional Locator-Block and CSID length. support any additional Locator-Block and CSID length.
The Argument length (AL) for NEXT-CSID flavor SIDs is equal to 128- The Argument length (AL) for NEXT-CSID flavor SIDs is equal to 128-
LBL-LNFL. LBL-LNFL.
When processing an IPv6 packet that matches a Forwarding Information When processing an IPv6 packet that matches a Forwarding Information
Base (FIB) entry locally instantiated as a SID with the NEXT-CSID Base (FIB) entry locally instantiated as a SID with the NEXT-CSID
flavor, the SR segment endpoint node applies the procedure specified flavor, the SR segment endpoint node applies the procedure specified
in the following subsection that corresponds to the SID behavior. If in the following subsection that corresponds to the SID behavior. If
the SID also has the PSP, USP, or USD flavor, the procedure is the SID also has the PSP, USP, or USD flavor, the procedure is
skipping to change at page 14, line 18 skipping to change at line 582
| Note: the variable B is defined in Section 4.15 of [RFC8986]. | Note: the variable B is defined in Section 4.15 of [RFC8986].
The resulting pseudocode is inserted between lines S01 and S02 of the The resulting pseudocode is inserted between lines S01 and S02 of the
SRH processing in Section 4.15 of [RFC8986]. In addition, this SRH processing in Section 4.15 of [RFC8986]. In addition, this
pseudocode is executed before processing any extension header that is pseudocode is executed before processing any extension header that is
not an SRH, a Hop-by-Hop header or a Destination Options header, or not an SRH, a Hop-by-Hop header or a Destination Options header, or
before processing the upper-layer header, whichever comes first. before processing the upper-layer header, whichever comes first.
A rendering of the complete pseudocode is provided in Appendix A.5. A rendering of the complete pseudocode is provided in Appendix A.5.
4.1.7. Combination with PSP, USP and USD flavors 4.1.7. Combination with PSP, USP, and USD Flavors
PSP: The PSP flavor defined in Section 4.16.1 of [RFC8986] is PSP: The PSP flavor defined in Section 4.16.1 of [RFC8986] is
unchanged when combined with the NEXT-CSID flavor. unchanged when combined with the NEXT-CSID flavor.
USP: The USP flavor defined in Section 4.16.2 of [RFC8986] is USP: The USP flavor defined in Section 4.16.2 of [RFC8986] is
unchanged when combined with the NEXT-CSID flavor. unchanged when combined with the NEXT-CSID flavor.
USD: The USP flavor defined in Section 4.16.3 of [RFC8986] is USD: The USP flavor defined in Section 4.16.3 of [RFC8986] is
unchanged when combined with the NEXT-CSID flavor. unchanged when combined with the NEXT-CSID flavor.
4.2. REPLACE-CSID Flavor 4.2. REPLACE-CSID Flavor
A CSID sequence compressed using the mechanism of the REPLACE-CSID A CSID sequence compressed using the mechanism of the REPLACE-CSID
flavor starts with a CSID container in fully formed 128-bit SID flavor starts with a CSID container in fully formed 128-bit SID
format. The Locator-Block of this SID is the common Locator-Block format. The Locator-Block of this SID is the common Locator-Block
for all the CSIDs in the CSID sequence, its Locator-Node and Function for all the CSIDs in the CSID sequence, its Locator-Node and Function
are those of the first CSID, and its Argument carries the index of are those of the first CSID, and its Argument carries the index of
the current CSID in the current CSID container. The Argument value the current CSID in the current CSID container. The Argument value
is initially 0. When more segments are present in the segment list, is initially 0. When more segments are present in the segment list,
skipping to change at page 14, line 51 skipping to change at line 615
K "positions" of LNFL bits, where K is computed as floor(128/LNFL). K "positions" of LNFL bits, where K is computed as floor(128/LNFL).
If LNFL does not divide into 128 perfectly, a zero pad is added in If LNFL does not divide into 128 perfectly, a zero pad is added in
the least significant bits of the CSID container to fill the bits the least significant bits of the CSID container to fill the bits
left over. The second CSID in the CSID sequence is encoded in the left over. The second CSID in the CSID sequence is encoded in the
least significant bit position of the first CSID container in packed least significant bit position of the first CSID container in packed
format (position K-1), the third CSID is encoded in position K-2, and format (position K-1), the third CSID is encoded in position K-2, and
so on. so on.
The last CSID in the CSID sequence is not required to have the The last CSID in the CSID sequence is not required to have the
REPLACE-CSID flavor. It can be bound to any SRv6 endpoint behavior, REPLACE-CSID flavor. It can be bound to any SRv6 endpoint behavior,
including [RFC8986] behaviors and NEXT-CSID flavor, as long as it including the behaviors described in [RFC8986] and NEXT-CSID flavor,
meets the conditions defined in Section 6. as long as it meets the conditions defined in Section 6.
The structure of a SID with the REPLACE-CSID flavor is shown in The structure of a SID with the REPLACE-CSID flavor is shown in
Figure 3. The same structure is also that of the CSID container for Figure 3. The same structure is also that of the CSID container for
REPLACE-CSID in fully formed 128-bit SID format. REPLACE-CSID in fully formed 128-bit SID format.
+-------------------------------------------------------------------+ +-------------------------------------------------------------------+
| Locator-Block | Locator-Node | Argument | | Locator-Block | Locator-Node | Argument |
| | + Function | | | | + Function | |
+-------------------------------------------------------------------+ +-------------------------------------------------------------------+
<----------------------> <--------------> <-----------------------> <----------------------> <--------------> <----------------------->
LBL LNFL AL LBL LNFL AL
Figure 3: Structure of a REPLACE-CSID flavor SID (scaled for a Figure 3: Structure of a REPLACE-CSID Flavor SID (Scaled for a
48-bit Locator- Block, 32-bit combined Locator-Node and Function, 48-Bit Locator- Block, 32-Bit Combined Locator-Node and Function,
and 48-bit Argument) and 48-Bit Argument)
The structure of a CSID container for REPLACE-CSID in packed format The structure of a CSID container for REPLACE-CSID in packed format
is shown in Figure 4. is shown in Figure 4.
+-------------------------------------------------------------------+ +-------------------------------------------------------------------+
| Fourth CSID | Third CSID | Second CSID | First CSID | | Fourth CSID | Third CSID | Second CSID | First CSID |
| (position 0) | (position 1) | (position 2) | (position 3) | | (position 0) | (position 1) | (position 2) | (position 3) |
+-------------------------------------------------------------------+ +-------------------------------------------------------------------+
<--------------> <--------------> <--------------> <--------------> <--------------> <--------------> <--------------> <-------------->
LNFL LNFL LNFL LNFL LNFL LNFL LNFL LNFL
Figure 4: Structure of a CSID container for REPLACE-CSID using a Figure 4: Structure of a CSID Container for REPLACE-CSID Using a
32-bit CSID length (K = 4) 32-Bit CSID Length (K = 4)
Figure 5 illustrates a compressed SID list as could be produced by an Figure 5 illustrates a compressed SID list as could be produced by an
SR source node steering a packet into an SR policy SID list of seven SR source node steering a packet into an SR policy SID list of seven
REPLACE-CSID flavor SIDs. All SIDs in this example have a 48-bit REPLACE-CSID flavor SIDs. All SIDs in this example have a 48-bit
Locator-Block, 32-bit combined Locator-Node and Function, and 48-bit Locator-Block, 32-bit combined Locator-Node and Function, and 48-bit
Argument. The SR source node compresses the SR policy SID list as a Argument. The SR source node compresses the SR policy SID list as a
compressed SID list of three CSID containers. The first CSID compressed SID list of three CSID containers. The first CSID
container is in fully formed 128-bit SID format. It carries a container is in fully formed 128-bit SID format. It carries a
Locator-Block, the first CSID, and the argument value zero. The Locator-Block, the first CSID, and the argument value zero. The
second and third CSID containers are in packed format. The second second and third CSID containers are in packed format. The second
skipping to change at page 17, line 16 skipping to change at line 679
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | | |
+ Locator-Block +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + Locator-Block +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | 1st CSID | | | 1st CSID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 1st CSID continued | | | 1st CSID continued | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 0 + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 0 +
| | | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
First CSID container First CSID Container
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 5th CSID | | 5th CSID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 4th CSID | | 4th CSID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 3rd CSID | | 3rd CSID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 2nd CSID | | 2nd CSID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Second CSID container Second CSID Container
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | | |
+ 0 + + 0 +
| | | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 7th CSID | | 7th CSID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 6th CSID | | 6th CSID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Third CSID container Third CSID Container
Figure 5: Compressed SID list of seven REPLACE-CSID flavor SIDs Figure 5: Compressed SID List of Seven REPLACE-CSID Flavor SIDs
with a 48-bit Locator-Block, 32-bit combined Locator-Node and with a 48-Bit Locator-Block, 32-Bit Combined Locator-Node and
Function, and 48-bit Argument Function, and 48-Bit Argument
This document updates [RFC8754] by allowing each entry in the SRH This document updates [RFC8754] by allowing each entry in the SRH
Segment List to be either an IPv6 address or a REPLACE-CSID container Segment List to be either an IPv6 address or a REPLACE-CSID container
in packed format. The SRv6 endpoint behaviors specified herein in packed format. The SRv6 endpoint behaviors specified herein
ensure that this entry is never copied as is to the IPv6 header and ensure that this entry is never copied as is to the IPv6 header and
that the Destination Address field of the IPv6 header is always a that the Destination Address field of the IPv6 header is always a
valid SRv6 SID conforming to [RFC9602]. valid SRv6 SID conforming to [RFC9602].
The REPLACE-CSID flavor SIDs support any Locator-Block length (LBL), The REPLACE-CSID flavor SIDs support any Locator-Block length (LBL),
depending on the needs of the operator, as long as it does not exceed depending on the needs of the operator, as long as it does not exceed
skipping to change at page 23, line 47 skipping to change at line 966
These SIDs differ from those defined in [RFC8986] by the presence of These SIDs differ from those defined in [RFC8986] by the presence of
an Argument as part of the SID structure. The Argument value is an Argument as part of the SID structure. The Argument value is
ignored by the SR segment endpoint node. ignored by the SR segment endpoint node.
When processing an IPv6 packet that matches a FIB entry locally When processing an IPv6 packet that matches a FIB entry locally
instantiated as an End.DT2M SID with the REPLACE-CSID flavor, the instantiated as an End.DT2M SID with the REPLACE-CSID flavor, the
procedure described in Section 4.12 of [RFC8986] is executed with the procedure described in Section 4.12 of [RFC8986] is executed with the
following modification. following modification.
For any End.DT2M SID with the REPLACE-CSID flavor, the value of For any End.DT2M SID with the REPLACE-CSID flavor, the value of
Arg.FE2 is 16-bit long. The SR segment endpoint node obtains the Arg.FE2 is 16 bits long. The SR segment endpoint node obtains the
value Arg.FE2 from the 16 most significant bits of DA.Argument if value Arg.FE2 from the 16 most significant bits of DA.Argument if
DA.Arg.Index is zero, or from the 16 least significant bits of the DA.Arg.Index is zero or from the 16 least significant bits of the
next position in the current CSID container (Segment List[Segments next position in the current CSID container (Segment List[Segments
Left][DA.Arg.Index-1]) otherwise (DA.Arg.Index is non-zero). Left][DA.Arg.Index-1]) otherwise (DA.Arg.Index is non-zero).
4.2.8. Combination with PSP, USP, and USD flavors 4.2.8. Combination with PSP, USP, and USD Flavors
PSP: When combined with the REPLACE-CSID flavor, the additional PSP PSP: When combined with the REPLACE-CSID flavor, the additional PSP
flavor instructions defined in Section 4.16.1.2 of [RFC8986] are flavor instructions defined in Section 4.16.1.2 of [RFC8986] are
inserted after lines R09 and R20 of the pseudocode in Section 4.2.1, inserted after lines R09 and R20 of the pseudocode in Section 4.2.1,
and the first line of the inserted instructions after R20 is modified and the first line of the inserted instructions after R20 is modified
as follows. as follows.
R20.1. If (Segments Left == 0 and (DA.Arg.Index == 0 or R20.1. If (Segments Left == 0 and (DA.Arg.Index == 0 or
Segment List[0][DA.Arg.Index-1] == 0)) { Segment List[0][DA.Arg.Index-1] == 0)) {
| Note: Segment List[Segments Left][DA.Arg.Index-1] identifies | Note: Segment List[Segments Left][DA.Arg.Index-1] identifies
| the value contained in the bits [(DA.Arg.Index- | the value contained in the bits [(DA.Arg.Index-
| 1)*LNFL..DA.Arg.Index*LNFL-1] in the SRH Segment List entry at | 1)*LNFL..DA.Arg.Index*LNFL-1] in the SRH Segment List entry at
| index Segments Left. | index Segments Left.
USP: When combined with the REPLACE-CSID flavor, the line S03 of the USP: When combined with the REPLACE-CSID flavor, the line S03 of the
pseudocode in Section 4.2.1 are substituted by the USP flavor pseudocode in Section 4.2.1 are substituted by the USP flavor
instructions S03.1 to S03.4 defined in Section 4.16.2 of [RFC8986]. instructions S03.1 to S03.4 defined in Section 4.16.2 of
Note that S03 is shown in the complete pseudocode in Appendix A.6. [RFC8986]. Note that S03 is shown in the complete pseudocode in
Appendix A.6.
USD: The USD flavor defined in Section 4.16.3 of [RFC8986] is USD: The USD flavor defined in Section 4.16.3 of [RFC8986] is
unchanged when combined with the REPLACE-CSID flavor. unchanged when combined with the REPLACE-CSID flavor.
5. CSID Allocation 5. CSID Allocation
The CSID value of 0 is reserved. It is used to indicate the end of a The CSID value of 0 is reserved. It is used to indicate the end of a
CSID container. CSID container.
In order to efficiently manage the CSID numbering space, a deployment In order to efficiently manage the CSID numbering space, a deployment
may divide it into two non-overlapping sub-spaces: a Global may divide it into two non-overlapping sub-spaces: a Global
Identifiers Block (GIB) and a Local Identifiers Block (LIB). Identifiers Block (GIB) and a Local Identifiers Block (LIB).
skipping to change at page 25, line 29 skipping to change at line 1045
A local CSID is a CSID allocated from the LIB. A local CSID is a CSID allocated from the LIB.
A local CSID identifies a segment defined at the node level and A local CSID identifies a segment defined at the node level and
within the scope of a particular Locator-Block. The tuple (Locator- within the scope of a particular Locator-Block. The tuple (Locator-
Block, CSID) identifies a different segment on each node of the SR Block, CSID) identifies a different segment on each node of the SR
domain. A typical example is a non-routed Adjacency segment bound to domain. A typical example is a non-routed Adjacency segment bound to
the End.X behavior. the End.X behavior.
Let N1 and N2 be two different physical nodes of the SR domain and I Let N1 and N2 be two different physical nodes of the SR domain and I
a local CSID value, N1 may allocate value I to SID S1 and N2 may a local CSID value: N1 may allocate value I to SID S1 and N2 may
allocate the same value I to SID S2. allocate the same value I to SID S2.
5.3. Recommended Installation of CSIDs in FIB 5.3. Recommended Installation of CSIDs in FIB
Section 4.3 of [RFC8754] defines how an SR segment endpoint node Section 4.3 of [RFC8754] defines how an SR segment endpoint node
identifies a locally instantiated SRv6 SID. To ensure that any valid identifies a locally instantiated SRv6 SID. To ensure that any valid
argument value is accepted, an SR segment endpoint node instantiating argument value is accepted, an SR segment endpoint node instantiating
a NEXT-CSID or REPLACE-CSID flavor SID should install a corresponding a NEXT-CSID or REPLACE-CSID flavor SID should install a corresponding
FIB entry that matches only the Locator and Function parts of the SID FIB entry that matches only the Locator and Function parts of the SID
(i.e., with a prefix length of LBL + LNL + FL). (i.e., with a prefix length of LBL + LNL + FL).
In addition, an SR segment endpoint node instantiating NEXT-CSID In addition, an SR segment endpoint node instantiating NEXT-CSID
flavor SIDs from both GIB and LIB may install combined "Global + flavor SIDs from both the GIB and LIB may install combined "Global +
Local" FIB entries to match a sequence of global and local CSIDs in a Local" FIB entries to match a sequence of global and local CSIDs in a
single longest prefix match (LPM) lookup. single longest-prefix match (LPM) lookup.
For example, let us consider an SR segment endpoint node 10 For example, let us consider an SR segment endpoint node 10
instantiating the following two NEXT-CSID flavor SIDs according to instantiating the following two NEXT-CSID flavor SIDs according to
the CSID length, Locator-Block length, and GIB/LIB recommendations in the CSID length, Locator-Block length, and GIB/LIB recommendations in
this section. this section.
* The SID 2001:db8:b1:10:: bound to the End behavior with the NEXT- * The SID 2001:db8:b1:10:: bound to the End behavior with the NEXT-
CSID flavor is instantiated from GIB with CSID flavor is instantiated from GIB with:
- Locator-Block length (LBL) = 48 (Locator-Block value - Locator-Block length (LBL) = 48 (Locator-Block value
0x20010db800b1), 0x20010db800b1),
- Locator-Node length (LNL) = 16 (Locator-Node value 0x0010), - Locator-Node length (LNL) = 16 (Locator-Node value 0x0010),
- Function length (FL) = 0, and - Function length (FL) = 0, and
- Argument length (AL) = 64. - Argument length (AL) = 64.
* The SID 2001:db8:b1:f123:: bound to the End.X behavior for its * The SID 2001:db8:b1:f123:: bound to the End.X behavior for its
local IGP adjacency 123 with the NEXT-CSID flavor is instantiated local IGP adjacency 123 with the NEXT-CSID flavor is instantiated
from LIB with from LIB with:
- Locator-Block length (LBL) = 48 (Locator-Block value - Locator-Block length (LBL) = 48 (Locator-Block value
0x20010db800b1), 0x20010db800b1),
- Locator-Node length (LNL) = 0, - Locator-Node length (LNL) = 0,
- Function length (FL) = 16 (Function value 0xf123), and - Function length (FL) = 16 (Function value 0xf123), and
- Argument length (AL) = 64. - Argument length (AL) = 64.
For SID 2001:db8:b1:10::, Node 10 would install the FIB entry For SID 2001:db8:b1:10::, Node 10 would install the FIB entry
2001:db8:b1:10::/64 bound the End SID with the NEXT-CSID flavor. 2001:db8:b1:10::/64 bound to the End SID with the NEXT-CSID flavor.
For SID 2001:db8:b1:f123::, Node 10 would install the FIB entry For SID 2001:db8:b1:f123::, Node 10 would install the FIB entry
2001:db8:b1:f123::/64 bound the End.X SID for adjacency 123 with the 2001:db8:b1:f123::/64 bound to the End.X SID for adjacency 123 with
NEXT-CSID flavor. the NEXT-CSID flavor.
In addition, Node 10 may also install the combined FIB entry In addition, Node 10 may also install the combined FIB entry
2001:db8:b1:10:f123::/80 bound the End.X SID for adjacency 123 with 2001:db8:b1:10:f123::/80 bound to the End.X SID for adjacency 123
the NEXT-CSID flavor. with the NEXT-CSID flavor.
As another example, let us consider an SR segment endpoint node 20 As another example, let us consider an SR segment endpoint node 20
instantiating the following two REPLACE-CSID flavor SIDs according to instantiating the following two REPLACE-CSID flavor SIDs according to
the CSID length, Locator-Block length, and GIB/LIB recommendations in the CSID length, Locator-Block length, and GIB/LIB recommendations in
this section. this section.
* 2001:db8:b2:20:1:: from GIB with Locator-Block length (LBL) = 48, * 2001:db8:b2:20:1:: from GIB with Locator-Block length (LBL) = 48,
Locator-Node length (LNL) = 16, Function length (FL) = 16, Locator-Node length (LNL) = 16, Function length (FL) = 16,
Argument length (AL) = 48, and bound to the End behavior with the Argument length (AL) = 48, and bound to the End behavior with the
REPLACE-CSID flavor. REPLACE-CSID flavor.
* 2001:db8:b2:20:123:: from GIB with Locator-Block length (LBL) = * 2001:db8:b2:20:123:: from GIB with Locator-Block length (LBL) =
48, Locator-Node length (LNL) = 16, Function length (FL) = 16, 48, Locator-Node length (LNL) = 16, Function length (FL) = 16,
Argument length (AL) = 48, and bound to the End.X behavior for its Argument length (AL) = 48, and bound to the End.X behavior for its
local IGP adjacency 123 with the REPLACE-CSID flavor. local IGP adjacency 123 with the REPLACE-CSID flavor.
For SID 2001:db8:b2:20:1::, Node 20 would install the FIB entry For SID 2001:db8:b2:20:1::, Node 20 would install the FIB entry
2001:db8:b2:20:1::/80 bound the End SID with the REPLACE-CSID flavor. 2001:db8:b2:20:1::/80 bound to the End SID with the REPLACE-CSID
flavor.
For SID 2001:db8:b2:20:123::, Node 20 would install the FIB entry For SID 2001:db8:b2:20:123::, Node 20 would install the FIB entry
2001:db8:b2:20:123::/80 bound the End.X SID for adjacency 123 with 2001:db8:b2:20:123::/80 bound to the End.X SID for adjacency 123 with
the REPLACE-CSID flavor. the REPLACE-CSID flavor.
6. SR Source Node 6. SR Source Node
An SR source node may learn from a control plane protocol (see An SR source node may learn from a control plane protocol (see
Section 8) or local configuration the SIDs that it can use in a Section 8) or local configuration the SIDs that it can use in a
segment list, along with their respective SRv6 endpoint behavior, segment list, along with their respective SRv6 endpoint behavior,
structure, and any other relevant attribute (e.g., the set of L3 structure, and any other relevant attribute (e.g., the set of L3
adjacencies associated with an End.X SID). adjacencies associated with an End.X SID).
6.1. SID Validation for Compression 6.1. SID Validation for Compression
As part of the compression process or as a preliminary step, the SR As part of the compression process or as a preliminary step, the SR
source node MUST validate the SID structure of each SID of this source node MUST validate the SID structure of each SID of this
document in the segment list. The SR source node does so regardless document in the segment list. The SR source node does so regardless
of whether the segment list is explicitly configured, locally of whether the segment list is explicitly configured, locally
computed, or advertised by a controller (e.g., via BGP computed, or advertised by a controller (e.g., via BGP [SR-BGP] or
[I-D.ietf-idr-sr-policy-safi] or PCEP [RFC9603]). PCEP [RFC9603]).
A SID structure is valid for compression if it meets all the A SID structure is valid for compression if it meets all the
following conditions. following conditions:
* The Locator-Block length is not 0. * The Locator-Block length is not 0.
* The sum of the Locator-Node length and Function length is not 0. * The sum of the Locator-Node length and Function length is not 0.
* The Argument length is equal to 128-LBL-LNL-FL. * The Argument length is equal to 128-LBL-LNL-FL.
When compressing a SID list, the SR source node MUST treat an invalid When compressing a SID list, the SR source node MUST treat an invalid
SID structure as unknown. A SID with an unknown SID structure is SID structure as unknown. A SID with an unknown SID structure is not
incompressible. compressible.
Section 8 discusses how the SIDs of this document and their structure Section 8 discusses how the SIDs of this document and their structure
can be advertised to the SR source node through various control plane can be advertised to the SR source node through various control plane
protocols. The SID structure may also be learned through protocols. The SID structure may also be learned through
configuration or other management protocols. The details of such configuration or other management protocols. The details of such
mechanisms are outside the scope of this document. mechanisms are outside the scope of this document.
6.2. Segment List Compression 6.2. Segment List Compression
An SR source node MAY compress a SID list when it includes NEXT-CSID An SR source node MAY compress a SID list when it includes NEXT-CSID
and/or REPLACE-CSID flavor SIDs to reduce the packet header length. and/or REPLACE-CSID flavor SIDs to reduce the packet header length.
It is out of the scope of this document to describe the mechanism It is out of the scope of this document to describe the mechanism
through which an uncompressed SID list is derived, since such through which an uncompressed SID list is derived, since such a
mechanism may include a wide range of considerations independent of mechanism may include a wide range of considerations independent of
compression (e.g., minimizing a specific metric, excluding certain compression (e.g., minimizing a specific metric, excluding certain
links, or providing a loop-free fast-reroute path). As a general links, or providing a loop-free fast-reroute path). As general
guidance for implementation or future specification, such a mechanism guidance for implementation or future specification, such a mechanism
should aim to select the combination of SIDs that would result in the should aim to select the combination of SIDs that would result in the
shortest compressed SID list. For example, by selecting a CSID shortest compressed SID list. For example, by selecting a CSID
flavor SID over an equivalent non-CSID flavor SID or by consistently flavor SID over an equivalent non-CSID flavor SID or by consistently
selecting SIDs of the same CSID flavor within each routing domain. selecting SIDs of the same CSID flavor within each routing domain.
The SID list that the SR source node pushes onto the packet MUST The SID list that the SR source node pushes onto the packet MUST
comply with the rules in Section 6.3 and Section 6.4 and express the comply with the rules in Sections 6.3 and 6.4 and express the same
same list of segments as the original SID list. If these rules are list of segments as the original SID list. If these rules are not
not followed, the packet may get dropped or misrouted. followed, the packet may get dropped or misrouted.
If an SR source node chooses to compress the SID list, one method is If an SR source node chooses to compress the SID list, one method is
described below for illustrative purposes. Any other method described below for illustrative purposes. Any other method
producing a compressed SID list of equal or shorter length than the producing a compressed SID list of equal or shorter length than the
uncompressed SID list MAY be used. uncompressed SID list MAY be used.
This method walks the uncompressed SID list and compresses each This method walks the uncompressed SID list and compresses each
series of consecutive NEXT-CSID flavor SIDs and each series of series of consecutive NEXT-CSID flavor SIDs and each series of
consecutive REPLACE-CSID flavor SIDs. consecutive REPLACE-CSID flavor SIDs.
* When the compression method encounters a series of one or more * When the compression method encounters a series of one or more
consecutive compressible NEXT-CSID flavor SIDs, it compresses the consecutive compressible NEXT-CSID flavor SIDs, it compresses the
series as follows. A SID with the NEXT-CSID flavor is series as follows. A SID with the NEXT-CSID flavor is
compressible if its structure is known to the SR source node and compressible if its structure is known to the SR source node and
its Argument value is 0. its Argument value is 0.
S01. Initialize a NEXT-CSID container equal to the first SID in the S01. Initialize a NEXT-CSID container equal to the first SID in the
series, and initialize the remaining capacity of the CSID series and initialize the remaining capacity of the CSID
container to the AL of that SID container to the AL of that SID
S02. For each subsequent SID in the series { S02. For each subsequent SID in the series {
S03. If the current SID Locator-Block matches that of the CSID S03. If the current SID Locator-Block matches that of the CSID
container and the current SID LNFL is lower than or equal to container and the current SID LNFL is lower than or equal to
the remaining capacity of the NEXT-CSID container { the remaining capacity of the NEXT-CSID container {
S04. Copy the current SID Locator-Node and Function to the most S04. Copy the current SID Locator-Node and Function to the most
significant remaining Argument bits of the NEXT-CSID significant remaining Argument bits of the NEXT-CSID
container and decrement the remaining capacity by LNFL container and decrement the remaining capacity by LNFL
S05. } Else { S05. } Else {
S06. Push the NEXT-CSID container onto the compressed SID list S06. Push the NEXT-CSID container onto the compressed SID list
S07. Initialize a new NEXT-CSID container equal to the current S07. Initialize a new NEXT-CSID container equal to the current
SID in the series, and initialize the remaining capacity SID in the series and initialize the remaining capacity
of the NEXT-CSID container to the AL of that SID of the NEXT-CSID container to the AL of that SID
S08. } // End If S08. } // End If
S09. } // End For S09. } // End For
S10. If at least one SID remains in the uncompressed SID list S10. If at least one SID remains in the uncompressed SID list
(following the series of compressible NEXT-CSID flavor SIDs){ (following the series of compressible NEXT-CSID flavor SIDs){
S11. Set S to the next SID in the uncompressed SID list S11. Set S to the next SID in the uncompressed SID list
S12. If S is advertised with a SID structure, and the Locator-Block S12. If S is advertised with a SID structure, and the Locator-Block
of S matches that of the NEXT-CSID container, and the sum of of S matches that of the NEXT-CSID container, and the sum of
the Locator-Node, Function, and Argument length of S is the Locator-Node, Function, and Argument length of S is
lower than or equal to the remaining capacity of the CSID lower than or equal to the remaining capacity of the CSID
container { container {
S13. Copy the Locator-Node, Function, and Argument of S to the S13. Copy the Locator-Node, Function, and Argument of S to the
most significant remaining Argument bits of the CSID most significant remaining Argument bits of the CSID
container container
S14. } // End If S14. } // End If
S15. } // End If S15. } // End If
S16. Push the NEXT-CSID container onto the compressed SID list S16. Push the NEXT-CSID container onto the compressed SID list
* When the compression method encounters a series of REPLACE-CSID * When the compression method encounters a series of REPLACE-CSID
flavor SIDs of the same CSID length in the uncompressed SID list, flavor SIDs of the same CSID length in the uncompressed SID list,
it compresses the series as per the following high-level pseudo it compresses the series as per the following high-level pseudo
code. A compression checking function ComCheck(F, S) is defined code. A compression checking function ComCheck(F, S) is defined
to check if two SIDs F and S share the same SID structure and to check if two SIDs F and S share the same SID structure and
Locator-Block value, and if S has either no Argument or an Locator-Block value, and if S has either no Argument or an
Argument with value 0. If the check passes, then ComCheck(F,S) Argument with value 0. If the check passes, then ComCheck(F,S)
returns true. returns true.
S01. Initialize a REPLACE-CSID container in full SID format equal to S01. Initialize a REPLACE-CSID container in full SID format equal to
the first SID in the series the first SID in the series
S02. Push the REPLACE-CSID container onto the compressed SID list S02. Push the REPLACE-CSID container onto the compressed SID list
S03. Initialize a new REPLACE-CSID container in packed format if S03. Initialize a new REPLACE-CSID container in packed format if
there are more than one SIDs, and initialize the remaining there are more than one SIDs and initialize the remaining
capacity of the REPLACE-CSID container to 128 bits capacity of the REPLACE-CSID container to 128 bits
S04. For each subsequent SID in the uncompressed SID list { S04. For each subsequent SID in the uncompressed SID list {
S05. Set S to the current SID in the uncompressed SID list S05. Set S to the current SID in the uncompressed SID list
S06. If ComCheck(First SID, S) { S06. If ComCheck(First SID, S) {
S07. If the LNFL of S is lower than or equal to S07. If the LNFL of S is lower than or equal to
the remaining capacity of the REPLACE-CSID container { the remaining capacity of the REPLACE-CSID container {
S08. Copy the Locator-Node and Function of S to the least S08. Copy the Locator-Node and Function of S to the least
significant remaining bits of the REPLACE-CSID container significant remaining bits of the REPLACE-CSID container
and decrement the remaining capacity by LNFL // Note and decrement the remaining capacity by LNFL // Note
S09. } Else { S09. } Else {
S10. Push the REPLACE-CSID container onto the compressed SID S10. Push the REPLACE-CSID container onto the compressed SID
list list
S11. Initialize a new REPLACE-CSID container in packed format S11. Initialize a new REPLACE-CSID container in packed format
with all bits set to 0 with all bits set to 0
S12. Copy the Locator-Node and Function of S to the least S12. Copy the Locator-Node and Function of S to the least
significant remaining bits of the REPLACE-CSID container significant remaining bits of the REPLACE-CSID container
and decrement the remaining capacity by LNFL // Note and decrement the remaining capacity by LNFL // Note
S13. } S13. }
S14. If S is not a REPLACE-CSID flavor SID, then break S14. If S is not a REPLACE-CSID flavor SID, then break
S15. } Else { S15. } Else {
S16. Break S16. Break
S17. } // End If S17. } // End If
S18. } // End For S18. } // End For
S19. Push the REPLACE-CSID container (if it is not empty) onto the S19. Push the REPLACE-CSID container (if it is not empty) onto the
compressed SID list compressed SID list
| Note: When the last CSID is an End.DT2M SID with the REPLACE- | Note: When the last CSID is an End.DT2M SID with the REPLACE-
| CSID flavor, if there is 0 or at least two CSID positions left | CSID flavor, if there are 0 or at least two CSID positions left
| in the current REPLACE-CSID container, the CSID is encoded as | in the current REPLACE-CSID container, the CSID is encoded as
| described above and the value of the Arg.FE2 argument is placed | described above and the value of the Arg.FE2 argument is placed
| in the 16 least significant bits of the next CSID position. | in the 16 least significant bits of the next CSID position.
| Otherwise (if there is only one CSID position left in the | Otherwise (if there is only one CSID position left in the
| current REPLACE-CSID container), the current REPLACE-CSID | current REPLACE-CSID container), the current REPLACE-CSID
| container is pushed onto the SID list (the value of the CSID | container is pushed onto the SID list (the value of the CSID
| position 0 remains zero) and the End.DT2M SID with the REPLACE- | position 0 remains zero) and the End.DT2M SID with the REPLACE-
| CSID flavor is encoded in full SID format with the value of the | CSID flavor is encoded in full SID format with the value of the
| Arg.FE2 argument in the 16 most significant bits of the SID | Arg.FE2 argument in the 16 most significant bits of the SID
| Argument. | Argument.
* In all remaining cases (i.e., when the compression method In all remaining cases (i.e., when the compression method encounters
encounters a SID in the uncompressed SID list that is not handled a SID in the uncompressed SID list that is not handled by any of the
by any of the previous subroutines), it pushes this SID as is onto previous subroutines), it pushes this SID as is onto the compressed
the compressed SID list. SID list.
Regardless of how a compressed SID list is produced, the SR source Regardless of how a compressed SID list is produced, the SR source
node writes it in the IPv6 packet as described in Sections 4.1 and node writes it in the IPv6 packet as described in Sections 4.1 and
4.1.1 of [RFC8754]. The text is reproduced below for reference. 4.1.1 of [RFC8754]. The text is reproduced below for reference.
| A source node steers a packet into an SR Policy. If the SR Policy | A source node steers a packet into an SR Policy. If the SR Policy
| results in a Segment List containing a single segment, and there | results in a Segment List containing a single segment, and there
| is no need to add information to the SRH flag or add TLV; the DA | is no need to add information to the SRH flag or add TLV; the DA
| is set to the single Segment List entry, and the SRH MAY be | is set to the single Segment List entry, and the SRH MAY be
| omitted. | omitted.
skipping to change at page 31, line 46 skipping to change at line 1329
| (the first segment). | (the first segment).
| |
| When a source does not require the entire SID list to be preserved | When a source does not require the entire SID list to be preserved
| in the SRH, a reduced SRH may be used. | in the SRH, a reduced SRH may be used.
| |
| A reduced SRH does not contain the first segment of the related SR | A reduced SRH does not contain the first segment of the related SR
| Policy (the first segment is the one already in the DA of the IPv6 | Policy (the first segment is the one already in the DA of the IPv6
| header), and the Last Entry field is set to n-2, where n is the | header), and the Last Entry field is set to n-2, where n is the
| number of elements in the SR Policy. | number of elements in the SR Policy.
6.3. Rules for segment lists containing NEXT-CSID flavor SIDs 6.3. Rules for Segment Lists Containing NEXT-CSID Flavor SIDs
1. If a Destination Options header would follow an SRH with a 1. If a Destination Options header would follow an SRH with a
segment list of more than one segment compressed as a single segment list of more than one segment compressed as a single
NEXT-CSID container, the SR source node MUST NOT omit the SRH. NEXT-CSID container, the SR source node MUST NOT omit the SRH.
2. When the last Segment List entry (index 0) in the SRH is a NEXT- 2. When the last Segment List entry (index 0) in the SRH is a NEXT-
CSID container representing more than one segment and the segment CSID container representing more than one segment and the segment
S preceding the first segment of this NEXT-CSID container in the S preceding the first segment of this NEXT-CSID container in the
segment list has the PSP flavor, then the PSP operation is segment list has the PSP flavor, then the PSP operation is
performed at the SR segment endpoint node of S. If the PSP performed at the SR segment endpoint node of S. If the PSP
skipping to change at page 32, line 24 skipping to change at line 1354
3. If a Destination Options header would follow an SRH with a last 3. If a Destination Options header would follow an SRH with a last
Segment List entry being a NEXT-CSID container representing more Segment List entry being a NEXT-CSID container representing more
than one segment, the SR source node MUST ensure that the PSP than one segment, the SR source node MUST ensure that the PSP
operation is not performed before the penultimate SR segment operation is not performed before the penultimate SR segment
endpoint node along the path. endpoint node along the path.
4. When the Argument of a NEXT-CSID container is not used to full 4. When the Argument of a NEXT-CSID container is not used to full
capacity, the remaining least significant bits of that Argument capacity, the remaining least significant bits of that Argument
MUST be set to 0. MUST be set to 0.
6.4. Rules for segment lists containing REPLACE-CSID flavor SIDs 6.4. Rules for Segment Lists Containing REPLACE-CSID Flavor SIDs
1. All SIDs compressed in a REPLACE-CSID sequence MUST share the 1. All SIDs compressed in a REPLACE-CSID sequence MUST share the
same Locator-Block and the same compression scheme. same Locator-Block and the same compression scheme.
2. All SIDs except the last one in a CSID sequence for REPLACE-CSID 2. All SIDs except the last one in a CSID sequence for REPLACE-CSID
MUST have the REPLACE-CSID flavor. If the last REPLACE-CSID MUST have the REPLACE-CSID flavor. If the last REPLACE-CSID
container is fully filled (i.e., the last CSID is at position 0 container is fully filled (i.e., the last CSID is at position 0
in the REPLACE-CSID container) and the last SID in the CSID in the REPLACE-CSID container) and the last SID in the CSID
sequence is not the last segment in the segment list, the last sequence is not the last segment in the segment list, the last
SID in the CSID sequence MUST NOT have the REPLACE-CSID flavor. SID in the CSID sequence MUST NOT have the REPLACE-CSID flavor.
3. When a REPLACE-CSID flavor CSID is present as the last SID in a 3. When a REPLACE-CSID flavor CSID is present as the last SID in a
container that is not the last Segment List entry (index 0) in container that is not the last Segment List entry (index 0) in
the SRH, the next element in the SID list MUST be a REPLACE-CSID the SRH, the next element in the SID list MUST be a REPLACE-CSID
container in packed format carrying at least one CSID. container in packed format carrying at least one CSID.
The SR source node determines the compression scheme of REPLACE-CSID The SR source node determines the compression scheme of REPLACE-CSID
flavor SIDs as follows. flavor SIDs as follows.
When receiving a SID advertisement for a REPLACE-CSID flavor SID with When receiving a SID advertisement for a REPLACE-CSID flavor SID with
LNL=16, FL=0, AL=128-LBL-LNFL, and the value of the Argument is all LNL=16, FL=0, AL=128-LBL-LNFL, and all zeros as the value of the
0, the SR source node marks both the SID and its locator as using Argument, the SR source node marks both the SID and its locator as
16-bit compression. All other SIDs allocated from this locator with using 16-bit compression. All other SIDs allocated from this locator
LNL=16, FL=16, AL=128-LBL-LNFL, and the value of the Argument is all with LNL=16, FL=16, AL=128-LBL-LNFL, and all zeros as the value of
0 are also marked as using 16-bit compression. When receiving a SID the Argument are also marked as using 16-bit compression. When
advertisement for a REPLACE-CSID flavor SID with LNFL=32, AL=128-LBL- receiving a SID advertisement for a REPLACE-CSID flavor SID with
LNFL, and the value of the Argument is all 0, the SR source node LNFL=32, AL=128-LBL-LNFL, and all zeros as the value of the Argument,
marks both the SID and its locator as using 32-bit compression. the SR source node marks both the SID and its locator as using 32-bit
compression.
6.5. Upper-Layer Checksums 6.5. Upper-Layer Checksums
The Destination Address used in the IPv6 pseudo-header (Section 8.1 The Destination Address used in the IPv6 pseudo-header (Section 8.1
of [RFC8200]) is that of the ultimate destination. of [RFC8200]) is that of the ultimate destination.
At the SR source node, that address will be the Destination Address At the SR source node, that address will be the Destination Address
as it is expected to be received by the ultimate destination. When as it is expected to be received by the ultimate destination. When
the last element in the compressed SID list is a CSID container, this the last element in the compressed SID list is a CSID container, this
address can be obtained from the last element in the uncompressed SID address can be obtained from the last element in the uncompressed SID
list or by repeatedly applying the segment behavior as described in list or by repeatedly applying the segment behavior as described in
Section 9.4. This applies regardless of whether an SRH is present in Section 9.4. This applies regardless of whether an SRH is present in
the IPv6 packet or omitted. the IPv6 packet or is omitted.
At the ultimate destination(s), that address will be in the At the ultimate destination(s), that address will be in the
Destination Address field of the IPv6 header. Destination Address field of the IPv6 header.
7. Inter-Domain Compression 7. Inter-Domain Compression
Some SRv6 traffic may need to cross multiple routing domains, such as Some SRv6 traffic may need to cross multiple routing domains, such as
different Autonomous Systems (ASes) or different routing areas within different Autonomous Systems (ASes) or different routing areas within
an SR domain. Different routing domains may use different addressing an SR domain. Different routing domains may use different addressing
schema and Locator-Blocks. schema and Locator-Blocks.
skipping to change at page 34, line 10 skipping to change at line 1438
behavior with the REPLACE-CSID flavor. behavior with the REPLACE-CSID flavor.
An End.LBS SID is used to transition to a new Locator-Block when the An End.LBS SID is used to transition to a new Locator-Block when the
routing domain boundary is on the SR segment endpoint node. routing domain boundary is on the SR segment endpoint node.
Each instance of an End.LBS SID is associated with a target Locator- Each instance of an End.LBS SID is associated with a target Locator-
Block B2/m, where B2 is an IPv6 address prefix and m is the Block B2/m, where B2 is an IPv6 address prefix and m is the
associated prefix length. The original and target Locator-Blocks can associated prefix length. The original and target Locator-Blocks can
have different prefix lengths as long as the new Destination Address have different prefix lengths as long as the new Destination Address
formed by combining the target Locator-Block with the Locator-Node, formed by combining the target Locator-Block with the Locator-Node,
Function, and Argument as described in the pseudocodes of Function, and Argument as described in the pseudocode of Sections
Section 7.1.1 and Section 7.1.2 is a valid IPv6 address. The target 7.1.1 and 7.1.2 is a valid IPv6 address. The target Locator-Block is
Locator-Block is a local property of the End.LBS SID on the SR a local property of the End.LBS SID on the SR segment endpoint node.
segment endpoint node.
| Note: a local SID property is an attribute associated with the | Note: a local SID property is an attribute associated with the
| SID when it is instantiated on the SR segment endpoint node. | SID when it is instantiated on the SR segment endpoint node.
| When the SR segment endpoint node identifies the destination | When the SR segment endpoint node identifies the destination
| address of a received packet as a locally instantiated SID, it | address of a received packet as a locally instantiated SID, it
| also retrieves any local property associated with this SID. | also retrieves any local property associated with this SID.
| Other examples of local SID properties include the set of L3 | Other examples of local SID properties include the set of L3
| adjacencies of an End.X SID (Section 4.2 of [RFC8986]) and the | adjacencies of an End.X SID (Section 4.1 of [RFC8986]) and the
| lookup table of an End.DT6 SID (Section 4.6 of [RFC8986]). | lookup table of an End.DT6 SID (Section 4.6 of [RFC8986]).
The means by which an SR source node learns the target Locator-Block The means by which an SR source node learns the target Locator-Block
associated with an End.LBS SID are outside the scope of this associated with an End.LBS SID are outside the scope of this
document. As examples, it could be learned via configuration or document. As examples, it could be learned via configuration or
signaled by a controller. signaled by a controller.
7.1.1. End.LBS with NEXT-CSID 7.1.1. End.LBS with NEXT-CSID
When processing an IPv6 packet that matches a FIB entry locally When processing an IPv6 packet that matches a FIB entry locally
skipping to change at page 35, line 28 skipping to change at line 1499
An End.XLBS SID is used to transition to a new Locator-Block when the An End.XLBS SID is used to transition to a new Locator-Block when the
routing domain boundary is on a link adjacent to the SR segment routing domain boundary is on a link adjacent to the SR segment
endpoint node. endpoint node.
Each instance of an End.XLBS SID is associated with a target Locator- Each instance of an End.XLBS SID is associated with a target Locator-
Block B2/m and a set, J, of one or more L3 adjacencies. The original Block B2/m and a set, J, of one or more L3 adjacencies. The original
and target Locator-Blocks can have different prefix lengths as long and target Locator-Blocks can have different prefix lengths as long
as the new Destination Address formed by combining the target as the new Destination Address formed by combining the target
Locator-Block with the Locator-Node, Function, and Argument as Locator-Block with the Locator-Node, Function, and Argument as
described in the pseudocodes of Section 7.2.1 and Section 7.2.2 is a described in the pseudocode of Sections 7.2.1 and 7.2.2 is a valid
valid IPv6 address. The target Locator-Block and set of adjacencies IPv6 address. The target Locator-Block and set of adjacencies are
are local properties of the End.XLBS SID on the SR segment endpoint local properties of the End.XLBS SID on the SR segment endpoint node.
node.
The means by which an SR source node learns the target Locator-Block The means by which an SR source node learns the target Locator-Block
associated with an End.XLBS SID are outside the scope of this associated with an End.XLBS SID are outside the scope of this
document. As examples, it could be learned via configuration or document. As examples, it could be learned via configuration or
signaled by a controller. signaled by a controller.
7.2.1. End.XLBS with NEXT-CSID 7.2.1. End.XLBS with NEXT-CSID
When processing an IPv6 packet that matches a FIB entry locally When processing an IPv6 packet that matches a FIB entry locally
instantiated as an End.XLBS SID with the NEXT-CSID flavor and instantiated as an End.XLBS SID with the NEXT-CSID flavor and
skipping to change at page 36, line 30 skipping to change at line 1546
8. Control Plane 8. Control Plane
Section 8 of [RFC8986] provides an overview of the control plane Section 8 of [RFC8986] provides an overview of the control plane
protocols used for signaling of the SRv6 endpoint behaviors protocols used for signaling of the SRv6 endpoint behaviors
introduced by that document, including the base SRv6 endpoint introduced by that document, including the base SRv6 endpoint
behaviors that are extended in the present document. behaviors that are extended in the present document.
The CSID-flavored behaviors introduced by this document are The CSID-flavored behaviors introduced by this document are
advertised in the same manner as their base SRv6 endpoint behaviors advertised in the same manner as their base SRv6 endpoint behaviors
using the SRv6 extensions for various routing protocols, such as using the SRv6 extensions for various routing protocols, such as:
* IS-IS [RFC9352] * IS-IS [RFC9352]
* OSPFv3 [RFC9513] * OSPFv3 [RFC9513]
* BGP [RFC9252], [RFC9514], [I-D.ietf-idr-sr-policy-safi] * BGP [RFC9252], [RFC9514], [SR-BGP]
* BGP-LS [I-D.ietf-idr-bgp-ls-sr-policy] * BGP-LS [BGP-LS-SR]
* PCEP [RFC9603] * PCEP [RFC9603]
The SR segment endpoint node MUST set the SID Argument bits to 0 when The SR segment endpoint node MUST set the SID Argument bits to 0 when
advertising a locally instantiated SID of this document in the advertising a locally instantiated SID of this document in the
routing protocol (e.g., IS-IS [RFC9352], OSPF [RFC9513], or BGP-LS routing protocol (e.g., IS-IS [RFC9352], OSPF [RFC9513], or BGP-LS
[RFC9514]). [RFC9514]).
Signaling the SRv6 SID Structure is REQUIRED for all the SIDs Signaling the SRv6 SID Structure is REQUIRED for all the SIDs
introduced in this document. It is used by an SR source node to introduced in this document. It is used by an SR source node to
skipping to change at page 37, line 26 skipping to change at line 1584
* Locator-Node length: 16 * Locator-Node length: 16
* Function length: 16 * Function length: 16
* Argument length: 48 (= 128-48-16-16) * Argument length: 48 (= 128-48-16-16)
A local CSID may be advertised in the control plane individually and/ A local CSID may be advertised in the control plane individually and/
or in combination with a global CSID instantiated on the same SR or in combination with a global CSID instantiated on the same SR
segment endpoint node, with the End behavior, and the same Locator- segment endpoint node, with the End behavior, and the same Locator-
Block and flavor as the local CSID. A combined global and local CSID Block and flavor as the local CSID. A combined global and local CSID
is advertised as follows. is advertised as follows:
* The SID Locator-Block is that shared by the global and local CSIDs * The SID Locator-Block is that shared by the global and local CSIDs
* The SID Locator-Node is that of global CSID * The SID Locator-Node is that of global CSID
* The SID Function is that of the local CSID * The SID Function is that of the local CSID
* The SID Argument length is equal to 128-LBL-LNL-FL and the SID * The SID Argument length is equal to 128-LBL-LNL-FL and the SID
Argument value is 0 Argument value is 0
* All other attributes of the SID (e.g., SRv6 endpoint behavior or * All other attributes of the SID (e.g., SRv6 endpoint behavior or
algorithm) are those of the local CSID algorithm) are those of the local CSID
The local CSID combined advertisement is needed in particular for The local CSID-combined advertisement is needed in particular for
control plane protocols mandating that the SID is a subnet of a control plane protocols mandating that the SID is a subnet of a
locator advertised in the same protocol (e.g., Section 8 of [RFC9352] locator advertised in the same protocol (e.g., Section 8 of [RFC9352]
and Section 9 of [RFC9513] for advertising Adjacency SIDs in IS-IS and Section 9 of [RFC9513] for advertising Adjacency SIDs in IS-IS
and OSPFv3, respectively). and OSPFv3, respectively).
For a segment list computed by a controller and signaled to an SR For a segment list computed by a controller and signaled to an SR
source node (e.g., via BGP [I-D.ietf-idr-sr-policy-safi] or PCEP source node (e.g., via BGP [SR-BGP] or PCEP [RFC9603]), the
[RFC9603]), the controller provides the ordered segment list controller provides the ordered segment list comprising the
comprising the uncompressed SIDs, with their respective behavior and uncompressed SIDs, with their respective behavior and structure, to
structure, to the SR source node. The SR source node may then the SR source node. The SR source node may then compress the SID
compress the SID list as described in Section 6. list as described in Section 6.
When a node that does not support this specification receives an When a node that does not support this specification receives an
advertisement of a SID of this document, it handles it as described advertisement of a SID of this document, it handles it as described
in the corresponding control plane specification (e.g., Sections 7.2, in the corresponding control plane specification (e.g., Sections 7.2,
8.1, and 8.2 of [RFC9352], Sections 8, 9.1, and 9.2 of [RFC9513], and 8.1, and 8.2 of [RFC9352], Sections 8, 9.1, and 9.2 of [RFC9513], and
Section 3.1 of [RFC9252]). Section 3.1 of [RFC9252]).
9. Operational Considerations 9. Operational Considerations
9.1. Flavor, Block, and CSID Length 9.1. Flavor, Block, and CSID Length
SRv6 is intended for use in a variety of networks that require SRv6 is intended for use in a variety of networks that require
different prefix lengths and SID numbering spaces. Each of the two different prefix lengths and SID numbering spaces. Each of the two
flavors introduced in this document comes with its own flavors introduced in this document comes with its own
recommendations for Locator-Block and CSID length, as specified in recommendations for Locator-Block and CSID length, as specified in
Section 4.1 and Section 4.2. These flavors are best suited for Sections 4.1 and 4.2. These flavors are best suited for different
different environments, depending on the requirements of the network. environments, depending on the requirements of the network. For
For instance, larger CSID lengths may be more suitable for networks instance, larger CSID lengths may be more suitable for networks
requiring ample SID numbering space, while smaller CSID lengths are requiring ample SID numbering space, while smaller CSID lengths are
better for compression efficiency. The two compression flavors allow better for compression efficiency. The two compression flavors allow
the compressed segment list encoding to adapt to a range of the compressed segment list encoding to adapt to a range of
requirements, with support for multiple compression levels. Network requirements, with support for multiple compression levels. Network
operators can choose the flavor that best suits their use case, operators can choose the flavor that best suits their use case,
deployment design, and network scale. deployment design, and network scale.
Both CSID flavors can coexist in the same SR domain, on the same SR Both CSID flavors can coexist in the same SR domain, on the same SR
segment endpoint node, and even in the same segment list. However, segment endpoint node, and even in the same segment list. However,
operators should generally avoid instantiating SIDs of different CSID operators should generally avoid instantiating SIDs of different CSID
flavors within the same routing domain or Locator-Block since these flavors within the same routing domain or Locator-Block since these
SIDs have different length and allocation recommendations (see SIDs have different length and allocation recommendations (see
Section 4.1, Section 4.2, and Section 9.2). In a multi-domain Sections 4.1, 4.2, and 9.2). In a multi-domain deployment, different
deployment, different flavors may be used in different routing flavors may be used in different routing domains of the SR domain.
domains of the SR domain.
A deployment should use consistent Locator-Block lengths and CSID A deployment should use consistent Locator-Block lengths and CSID
lengths for all SIDs within a routing domain. Heterogeneous lengths, lengths for all SIDs within a routing domain. Heterogeneous lengths,
while possible, may impact the compression efficiency. while possible, may impact the compression efficiency.
The compressed segment list encoding works with various Locator-Block The compressed segment list encoding works with various Locator-Block
allocations. For example, each routing domain within the SR domain allocations. For example, each routing domain within the SR domain
can be allocated a /48 Locator-Block from a global IPv6 block can be allocated a /48 Locator-Block from a global IPv6 block
available to the operator, or from a prefix allocated to SRv6 SIDs as available to the operator or from a prefix allocated to SRv6 SIDs as
discussed in Section 5 of [RFC9602]. discussed in Section 5 of [RFC9602].
9.2. GIB/LIB Usage 9.2. GIB/LIB Usage
GIB and LIB usage is a local implementation and/or configuration GIB and LIB usage is a local implementation and/or configuration
decision, however, some guidelines for determining usage for specific decision; however, some guidelines for determining usage for specific
SRv6 endpoint behaviors and recommendations are provided. SRv6 endpoint behaviors and recommendations are provided.
The GIB number space is shared among all SR segment endpoint nodes The GIB number space is shared among all SR segment endpoint nodes
using SRv6 locators under a Locator-Block space. The more SIDs using SRv6 locators under a Locator-Block space. The more SIDs
assigned from this space, per node, the faster it is exhausted. assigned from this space, per node, the faster it is exhausted.
Therefore, its use is prioritized for global segments, such as SIDs Therefore, its use is prioritized for global segments, such as SIDs
that identify a node. that identify a node.
The LIB number space is unique per node. Each node can fully utilize The LIB number space is unique per node. Each node can fully utilize
the entire LIB number space without consideration of assignments at the entire LIB number space without consideration for assignments at
other nodes. Therefore, its use is prioritized for local segments, other nodes. Therefore, its use is prioritized for local segments,
such as SIDs that identify services (of which there may be many) at such as SIDs that identify services (of which there may be many) at
nodes, cross-connects, or adjacencies. nodes, cross-connects, or adjacencies.
While a longer CSID length permits more flexibility in which SRv6 While a longer CSID length permits more flexibility in which SRv6
endpoint behaviors may be assigned from the GIB; it also reduces the endpoint behaviors may be assigned from the GIB, it also reduces the
compression efficiency. compression efficiency.
Given the previous Locator-Block and CSID length recommendations, the Given the previous Locator-Block and CSID length recommendations, the
following GIB/LIB usage is recommended: following GIB/LIB usage is recommended:
* NEXT-CSID: * NEXT-CSID:
- GIB: End - GIB: End
- LIB: End.X, End.T, End.DT4/6/46/2U/2M, End.DX4/6/2/2V - LIB: End.X, End.T, End.DT4/6/46/2U/2M, End.DX4/6/2/2V
skipping to change at page 39, line 46 skipping to change at line 1700
- LIB: End.DX2/2V for large-scale pseudowire - LIB: End.DX2/2V for large-scale pseudowire
Any other allocation is possible but may lead to a suboptimal use of Any other allocation is possible but may lead to a suboptimal use of
the CSID numbering space. the CSID numbering space.
9.3. Pinging a SID 9.3. Pinging a SID
An SR source node may ping an SRv6 SID by sending an ICMPv6 echo An SR source node may ping an SRv6 SID by sending an ICMPv6 echo
request packet destined to the SRv6 SID. The SR source node may ping request packet destined to the SRv6 SID. The SR source node may ping
the target SID with a SID list comprising only that target SID, or the target SID with a SID list comprising only that target SID or
with a longer one that comprises two or more SIDs. In that case, the with a longer one that comprises two or more SIDs. In that case, the
target SID is the last element in the SID list. This operation is target SID is the last element in the SID list. This operation is
illustrated in Appendix A.1.2 of [RFC9259]. illustrated in Appendix A.1.2 of [RFC9259].
When pinging a SID of this document the SR source node MUST construct When pinging a SID of this document, the SR source node MUST
the IPv6 packet as described in Section 6, including computing the construct the IPv6 packet as described in Section 6, including
ICMPv6 checksum as described in Section 6.5. computing the ICMPv6 checksum as described in Section 6.5.
In particular, when pinging a SID of this document with a SID list In particular, when pinging a SID of this document with a SID list
comprising only the target SID, the SR source node places the SID comprising only the target SID, the SR source node places the SID
with Argument value 0 in the destination address of the ICMPv6 echo with Argument value 0 in the destination address of the ICMPv6 echo
request and computes the ICMPv6 checksum using this SID as the request and computes the ICMPv6 checksum using this SID as the
destination address in the IPv6 pseudo-header. The Argument value 0 destination address in the IPv6 pseudo-header. The Argument value 0
allows the SID SR segment endpoint node (Section 4) to identify allows the SID SR segment endpoint node (Section 4) to identify
itself as the ultimate destination of the packet and process the itself as the ultimate destination of the packet and process the
ICMPv6 payload. Therefore, any existing IPv6 ping implementation can ICMPv6 payload. Therefore, any existing IPv6 ping implementation can
originate ICMP echo requests to a NEXT-CSID or REPLACE-CSID flavor originate ICMP echo requests to a NEXT-CSID or REPLACE-CSID flavor
skipping to change at page 41, line 5 skipping to change at line 1752
result in the processing of the upper-layer header. result in the processing of the upper-layer header.
The destination address of the resulting IPv6 packet may be used as The destination address of the resulting IPv6 packet may be used as
the ultimate destination of the invoking IPv6 packet. the ultimate destination of the invoking IPv6 packet.
Since the SR source node that needs to determine the ultimate Since the SR source node that needs to determine the ultimate
destination is the same node that originally built the SID list in destination is the same node that originally built the SID list in
the invoking packet, it can perform this operation for all the SIDs the invoking packet, it can perform this operation for all the SIDs
in the packet. in the packet.
10. Implementation Status 10. Applicability to Other SRv6 Endpoint Behaviors
This section is to be removed before publishing as an RFC.
RFC-Editor: Please clean up the references cited by this section
before publication.
This section records the status of known implementations of the
protocol defined by this specification at the time of posting of this
Internet-Draft, and is based on a proposal described in [RFC7942].
The description of implementations in this section is intended to
assist the IETF in its decision processes in progressing drafts to
RFCs. Please note that the listing of any individual implementation
here does not imply endorsement by the IETF. Furthermore, no effort
has been spent to verify the information presented here that was
supplied by IETF contributors. This is not intended as, and must not
be construed to be, a catalog of available implementations or their
features. Readers are advised to note that other implementations may
exist.
According to [RFC7942], "this will allow reviewers and working groups
to assign due consideration to documents that have the benefit of
running code, which may serve as evidence of valuable experimentation
and feedback that have made the implemented protocols more mature.
It is up to the individual working groups to use this information as
they see fit".
This section is provided in compliance with the SPRING working group
policies ([SPRING-WG-POLICIES]).
10.1. Cisco Systems
Cisco Systems reported the following implementations of the SR
segment endpoint node NEXT-CSID flavor (Section 4.1) and the SR
source node efficient SID list encoding (Section 6) for NEXT-CSID
flavor SIDs. These are used as part of its SRv6 TI-LFA, micro-loop
avoidance, and traffic engineering functionalities.
* Cisco NCS 540 Series routers running IOS XR 7.3.x or above
[IMPL-CISCO-NCS540]
* Cisco NCS 560 Series routers running IOS XR 7.6.x or above
[IMPL-CISCO-NCS560]
* Cisco NCS 5500 Series routers running IOS XR 7.3.x or above
[IMPL-CISCO-NCS5500]
* Cisco NCS 5700 Series routers running IOS XR 7.5.x or above
[IMPL-CISCO-NCS5700]
* Cisco 8000 Series routers running IOS XR 7.5.x or above
[IMPL-CISCO-8000]
* Cisco ASR 9000 Series routers running IOS XR 7.5.x or above
[IMPL-CISCO-ASR9000]
At the time of this report, all the implementations listed above are
in production and follow the specification in the latest version of
this document, including all the "MUST" and "SHOULD" clauses for the
NEXT-CSID flavor.
This report was last updated on January 11, 2023.
10.2. Huawei Technologies
Huawei Technologies reported the following implementations of the SR
segment endpoint node REPLACE-CSID flavor (Section 4.2). These are
used as part of its SRv6 TI-LFA, micro-loop avoidance, and traffic
engineering functionalities.
* Huawei ATN8XX,ATN910C,ATN980B routers running VRPV800R021C00 or
above.
* Huawei CX600-M2 routers running VRPV800R021C00 or above.
* Huawei NE40E,ME60-X1X2,ME60-X3X8X16 routers running VRPV800R021C00
or above.
* Huawei NE5000E,NE9000 routers running VRPV800R021C00 or above.
* Huawei NCE-IP Controller running V1R21C00 or above.
At the time of this report, all the implementations listed above are
in production and follow the specification in the latest version of
this document, including all the "MUST" and "SHOULD" clauses for the
REPLACE-CSID flavor.
This report was last updated on January 11, 2023.
10.3. Nokia
Nokia reported the following implementations ([IMPL-NOKIA-20.10]) of
the SR segment endpoint node NEXT-CSID flavor (Section 4.1). These
are used as part of its shortest path forwarding (in algorithm 0 and
Flex-Algo), remote and TI-LFA repair tunnel, and Traffic Engineering
functionalities.
* Nokia 7950 XRS 20/20e routers running SROS Release 22.10 or above
* Nokia 7750 SR-12e routers running SROS Release 22.10 or above
* Nokia 7750 SR-7/12 routers running SROS Release 22.10 or above
* Nokia 7750 SR-7s/14s routers running SROS Release 22.10 or above
* Nokia 7750 SR-1/1s/2s routers running SROS Release 22.10 or above
At the time of this report, all the implementations listed above are
in production and follow the specification in the latest version of
this document, including all the "MUST" and "SHOULD" clauses for the
NEXT-CSID flavor.
This report was last updated on February 3, 2023.
10.4. Arrcus
Arrcus reported the following implementations of the SR segment
endpoint node NEXT-CSID flavor (Section 4.1). These are used as part
of its SRv6 shortest path forwarding (in algorithm 0 and Flex-Algo),
TI-LFA, micro-loop avoidance and Traffic Engineering functionalities.
* Arrcus running on Ufi Space routers S9510-28DC, S9710-76D,
S9600-30DX and S9700-23D with ArcOS v5.2.1 or above
* Arrcus running n Ufi Space routers S9600-72XC and S9700-53DX with
ArcOS v5.1.1D or above
* Arrcus running on Quanta router IXA and IXAE with ArcOS v5.1.1D or
above
At the time of this report, all the implementations listed above are
in production and follow the specification in the latest version of
this document, including all the "MUST" and "SHOULD" clauses for the
NEXT-CSID flavor.
This report was last updated on March 11, 2023.
10.5. Juniper Networks
Juniper Networks reported the following implementations of the SR
segment endpoint node NEXT-CSID flavor (Section 4.1). These are used
as part of its SRv6 shortest path forwarding (in algorithm 0 and
Flex-Algo), TI-LFA, micro-loop avoidance, and Traffic Engineering
functionalities.
Juniper release 23.3 onwards supports this functionality.
At the time of this report, all the implementations listed above are
in development and follow the specification in the latest version of
this document, including all the "MUST" and "SHOULD" clauses for the
NEXT-CSID flavor.
This report was last updated on May 30, 2023.
10.6. Marvell
Marvell reported support in the Marvell Prestera Packet Processor for
the SR segment endpoint node NEXT-CSID flavor (Section 4.1) and
REPLACE-CSID flavor (Section 4.2).
This report was last updated on February 15, 2023.
10.7. Broadcom
Broadcom reported the following implementations of the SR segment
endpoint node NEXT-CSID flavor (Section 4.1) and REPLACE-CSID flavor
(Section 4.2). These are used as part of its SRv6 TI-LFA, micro-loop
avoidance, and traffic engineering functionalities. All
implementation of the following list is in general availability for
customers using BCM SDK 6.5.26 or above.
* 88850 (Jericho2c+) series
* 88690 (Jericho2) series
* 88800 (Jericho2c) series
* 88480 (Qunran2a) series
* 88280 (Qunran2u) series
* 88295 (Qunran2n) series
* 88830 (Jericho2x) series
At the time of this report, all the implementations listed above are
in production and follow the specification in the latest version of
this document, including all the "MUST" and "SHOULD" clauses for the
NEXT-CSID and REPLACE-CSID flavors.
For 78900 (Tomahawk) series-related support, please contact the
Broadcom team.
This report was last updated on February 21, 2023.
10.8. ZTE Corporation
ZTE Corporation reported the following implementations of the SR
segment endpoint node REPLACE-CSID flavor (Section 4.2). These are
used as part of its SRv6 TI-LFA, micro-loop avoidance, and traffic
engineering functionalities.
* ZTE M6000-18S(BRAS), M6000-8S Plus(BRAS) routers running
V5.00.10.09 or above.
* ZTE M6000-18S(SR), M6000-8S Plus(SR) routers running V5.00.10.80
or above.
* ZTE T8000-18 routers running V5.00.10.07 or above.
This report was last updated on March 29, 2023.
10.9. New H3C Technologies
New H3C Technologies reported the following implementations of the SR
segment endpoint node REPLACE-CSID flavor (Section 4.2). These are
used as part of its SRv6 TI-LFA, micro-loop avoidance, and traffic
engineering functionalities.
* H3C CR16000-F, SR8800-X routers running Version 7.1.075 or above.
* H3C CR18000, CR19000 routers running Version 7.1.071 or above.
This report was last updated on March 29, 2023.
10.10. Ruijie Network
Ruijie Network reported the following implementations of the SR
segment endpoint node REPLACE-CSID flavor (Section 4.2). These are
used as part of its SRv6 TI-LFA, micro-loop avoidance, and traffic
engineering functionalities.
* RUIJIE RG-N8018-R, RG-N8010-R routers running N8000-R_RGOS
12.8(3)B0801 or above.
This report was last updated on March 29, 2023.
10.11. Ciena
Ciena reported the following implementations of the SR segment
endpoint node NEXT-CSID flavor (Section 4.1). These are used as part
of its shortest path forwarding (in algorithm 0 and Flex-Algo),
remote and TI-LFA repair tunnel, and Traffic Engineering
functionalities.
The following platforms support implementation of the above.
* Ciena 5162, 5164, 5166, 5168 routers running SAOS 10.10 or above
* Ciena 8110, 8112, 8190 routers running SAOS 10.10 or above
At the time of this report, all the implementations listed above are
in production and follow the specification in the latest version of
this document, including all the "MUST" and "SHOULD" clauses for the
NEXT-CSID flavor.
This report was last updated on February 6, 2024.
10.12. Centec
Centec reported the following implementations of the SR segment
endpoint node REPLACE-CSID flavor (Section 4.2). These are used as
part of its SRv6 TI-LFA, micro-loop avoidance, and traffic
engineering functionalities. All implementation of the following
list is in general availability for customers using Centec SDK 5.6.8
or above.
* CTC7132 (TsingMa) Series
* CTC8180 (TsingMa.MX) Series
This report was last updated on February 14, 2024.
10.13. Open-Source
The authors found the following open-source implementations of the SR
segment endpoint node NEXT-CSID flavor (Section 4.1).
* The Linux kernel, version 6.1 [IMPL-OSS-LINUX]
* The Software for Open Networking in the Cloud (SONiC), version
202212 [IMPL-OSS-SONIC], and Switch Abstraction Interface (SAI),
version 1.9.0 [IMPL-OSS-SAI]
* The Vector Packet Processor (VPP), version 20.05 [IMPL-OSS-VPP]
* A generic P4 implementation [IMPL-OSS-P4]
The authors found the following open-source implementations of the SR
segment endpoint node REPLACE-CSID flavor (Section 4.2).
* ONOS and P4 Programmable Switch based [IMPL-OSS-ONOS]
* Open SRv6 Project [IMPL-OSS-OPEN-SRV6]
This section was last updated on January 11, 2023.
10.14. Interoperability Reports
10.14.1. EANTC 2024
In April 2024, the European Advanced Networking Test Center (EANTC)
successfully validated multiple implementations of SRv6 NEXT-CSID
flavor (a.k.a., SRv6 uSID) [EANTC-24].
The participating vendors included Arista, Ciena, Cisco, Ericsson,
H3C, Huawei, Juniper, Keysight, Nokia, and ZTE.
10.14.2. Bell Canada / Ciena 2023
Bell Canada is currently evaluating interoperability between Ciena
and Cisco implementations of the NEXT-CSID flavor defined in this
document. Further information will be added to this section when the
evaluation is complete.
10.14.3. EANTC 2023
In April 2023, the European Advanced Networking Test Center (EANTC)
successfully validated multiple implementations of SRv6 NEXT-CSID
flavor (a.k.a., SRv6 uSID) [EANTC-23].
The participating vendors included Arista, Arrcus, Cisco, Huawei,
Juniper, Keysight, Nokia, and Spirent.
10.14.4. China Mobile 2020
In November 2020, China Mobile successfully validated multiple
interoperable implementations of the NEXT-CSID and REPLACE-CSID
flavors defined in this document.
This testing covered two different implementations of the SRv6
endpoint flavors defined in this document:
* Hardware implementation in Cisco ASR 9000 running IOS XR
* Software implementation in Cisco IOS XRv9000 virtual appliance
* Hardware implementation in Huawei NE40E and NE5000E running VRP
The interoperability testing consisted of a packet flow sent by an SR
source node N0 via an SR traffic engineering policy with a segment
list <S1, S2, S3, S4, S5, S6, S7>, where S1..S7 are SIDs instantiated
on SR segment endpoint nodes N1..N7, respectively.
N0 --- N1 --- N2 --- N3 --- N4 --- N5 --- N6 --- N7
(S1) (S2) (S3) (S4) (S5) (S6) (S7)
* N0 is a generic packet generator.
* N1, N2, and N3 are Huawei routers.
* N4, N5, and N6 are Cisco routers.
* N7 is a generic traffic generator acting as a packet receiver.
The SR source node N0 steers the packets onto the SR policy by
setting the IPv6 destination address and creating an SRH (as
described in Section 4.1 of [RFC8754]) using a compressed segment
list encoding. The length of the compressed segment list encoding
varies for each scenario.
All SR segment endpoint nodes execute a variant of the End behavior:
regular End behavior (as defined in Section 4.1 of [RFC8986]), End
behavior with NEXT-CSID flavor, and End behavior with REPLACE-CSID
flavor. The variant being used at each SR segment endpoint node
varies for each scenario.
The interoperability was validated for the following scenarios:
*Scenario 1:*
* S1 and S2 are associated with the End behavior with the REPLACE-
CSID flavor
* S3 is associated with the regular End behavior (no flavor)
* S4, S5, and S6 are associated with the End behavior with the NEXT-
CSID flavor
* The SR source node imposes a compressed segment list encoding of 3
SIDs.
*Scenario 2:*
* S1, S2..., S6 are associated with the End behavior with the NEXT-
CSID flavor
* The SR source node imposes a compressed segment list encoding of 2
SIDs.
*Scenario 3:*
* S1, S2..., S6 are associated with the End behavior with the
REPLACE-CSID flavor
* The SR source node imposes a compressed segment list encoding of 3
SIDs.
11. Applicability to other SRv6 Endpoint Behaviors
Future documents may extend the applicability of the NEXT-CSID and Future documents may extend the applicability of the NEXT-CSID and
REPLACE-CSID flavors to other SRv6 endpoint behaviors. REPLACE-CSID flavors to other SRv6 endpoint behaviors.
For an SRv6 endpoint behavior that can be used before the last For an SRv6 endpoint behavior that can be used before the last
position of a segment list, a CSID flavor is defined by reproducing position of a segment list, a CSID flavor is defined by reproducing
the same logic as described in Section 4.1 and Section 4.2 of this the same logic as described in Sections 4.1 and 4.2 to determine the
document to determine the next SID in the SID list. next SID in the SID list.
12. Security Considerations 11. Security Considerations
Section 8 of [RFC8402] discusses the security considerations for Section 8 of [RFC8402] discusses the security considerations for
Segment Routing. Segment Routing.
Section 5 of [RFC8754] describes the intra-SR-domain deployment model Section 5 of [RFC8754] describes the intra-SR-domain deployment model
and how to secure it. Section 7 of [RFC8754] describes the threats and how to secure it. Section 7 of [RFC8754] describes the threats
applicable to SRv6 and how to mitigate them. applicable to SRv6 and how to mitigate them.
Section 9 of [RFC8986] discusses the security considerations Section 9 of [RFC8986] discusses the security considerations
applicable to the SRv6 network programming framework, as well as the applicable to the SRv6 network programming framework, as well as the
SR source node and SR segment endpoint node behaviors that it SR source node and SR segment endpoint node behaviors that it
defines. defines.
This document introduces two new flavors for some of the SRv6 This document introduces two new flavors, NEXT-CSID and REPLACE-CSID,
endpoint behaviors defined in [RFC8986] and a method by which an SR for some of the SRv6 endpoint behaviors defined in [RFC8986] and a
source node may leverage the SIDs of these flavors to produce a method by which an SR source node may leverage the SIDs of these
compressed segment list encoding. flavors to produce a compressed segment list encoding.
This document also introduces two new SRv6 endpoint behaviors, This document also introduces two new SRv6 endpoint behaviors,
End.LBS and End.XLBS, to preserve the efficiency of CSID compression End.LBS and End.XLBS, to preserve the efficiency of CSID compression
in multi-domain environments. in multi-domain environments.
An SR source node constructs an IPv6 packet with a compressed segment An SR source node constructs an IPv6 packet with a compressed segment
list encoding as defined in Sections 3.1 and 4.1 of [RFC8754] and list encoding as defined in Sections 3.1 and 4.1 of [RFC8754] and
Section 5 of [RFC8986]. The paths that an SR source node may enforce Section 5 of [RFC8986]. The paths that an SR source node may enforce
using a compressed segment list encoding are the same, from a using a compressed segment list encoding are the same, from a
topology and service perspective, as those that an SR source node topology and service perspective, as those that an SR source node
could enforce using the SIDs of [RFC8986]. could enforce using the SIDs of [RFC8986].
An SR segment endpoint node processes an IPv6 packet matching a An SR segment endpoint node processes an IPv6 packet matching a
locally instantiated SID as defined in [RFC8986], with the pseudocode locally instantiated SID as defined in [RFC8986], with the pseudocode
modifications in Section 4 of this document. These modifications modifications in Section 4 of this document. These modifications
change how the SR segment endpoint node determines the next SID in change how the SR segment endpoint node determines the next SID in
the packet, but not the semantic of either the active or the next the packet but not the semantic of either the active or the next SID.
SID. For example, an adjacency segment instantiated with the End.X For example, an adjacency segment instantiated with the End.X
behavior remains an adjacency segment regardless of whether it uses behavior remains an adjacency segment regardless of whether it uses
the base End.X behavior defined in Section 4.2 of [RFC8986] or a CSID the base End.X behavior defined in Section 4.2 of [RFC8986] or a CSID
flavor of that behavior. This document does not introduce any new flavor of that behavior. This document does not introduce any new
SID semantic. SID semantic.
Any other transit node processes the packet as described in Any other transit node processes the packet as described in
Section 4.2 of [RFC8754]. Section 4.2 of [RFC8754].
This document defines a new method of encoding the SIDs inside a SID This document defines a new method of encoding the SIDs inside a SID
list at the SR source node (Section 6) and decoding them at the SR list at the SR source node (Section 6) and decoding them at the SR
segment endpoint node (Section 4 and Section 7), but it does not segment endpoint node (see Sections 4 and 7), but it does not change
change how the SID list itself is encoded in the IPv6 packet nor the how the SID list itself is encoded in the IPv6 packet nor the
semantic of any segment that it comprises. Therefore, this document semantic of any segment that it comprises. Therefore, this document
is subject to the same security considerations that are discussed in is subject to the same security considerations that are discussed in
[RFC8402], [RFC8754], and [RFC8986]. [RFC8402], [RFC8754], and [RFC8986].
13. IANA Considerations 12. IANA Considerations
13.1. SRv6 Endpoint Behaviors
This I-D. requests the IANA to update the reference of the following 12.1. SRv6 Endpoint Behaviors
registrations from the "SRv6 Endpoint Behaviors" registry under the
top-level "Segment Routing" registry-group IANA has updated the reference of the following registrations from
(https://www.iana.org/assignments/segment-routing/) with the RFC the "SRv6 Endpoint Behaviors" registry under the "Segment Routing"
number of this document once it is published, and transfer change registry group (<https://www.iana.org/assignments/segment-routing/>)
control to the IETF. to point to this document and transfer change control to the IETF.
+=======+=========================================+===========+ +=======+=========================================+===========+
| Value | Description | Reference | | Value | Description | Reference |
+=======+=========================================+===========+ +=======+=========================================+===========+
| 43 | End with NEXT-CSID | This I-D. | | 43 | End with NEXT-CSID | RFC 9800 |
+-------+-----------------------------------------+-----------+ +-------+-----------------------------------------+-----------+
| 44 | End with NEXT-CSID & PSP | This I-D. | | 44 | End with NEXT-CSID & PSP | RFC 9800 |
+-------+-----------------------------------------+-----------+ +-------+-----------------------------------------+-----------+
| 45 | End with NEXT-CSID & USP | This I-D. | | 45 | End with NEXT-CSID & USP | RFC 9800 |
+-------+-----------------------------------------+-----------+ +-------+-----------------------------------------+-----------+
| 46 | End with NEXT-CSID, PSP & USP | This I-D. | | 46 | End with NEXT-CSID, PSP & USP | RFC 9800 |
+-------+-----------------------------------------+-----------+ +-------+-----------------------------------------+-----------+
| 47 | End with NEXT-CSID & USD | This I-D. | | 47 | End with NEXT-CSID & USD | RFC 9800 |
+-------+-----------------------------------------+-----------+ +-------+-----------------------------------------+-----------+
| 48 | End with NEXT-CSID, PSP & USD | This I-D. | | 48 | End with NEXT-CSID, PSP & USD | RFC 9800 |
+-------+-----------------------------------------+-----------+ +-------+-----------------------------------------+-----------+
| 49 | End with NEXT-CSID, USP & USD | This I-D. | | 49 | End with NEXT-CSID, USP & USD | RFC 9800 |
+-------+-----------------------------------------+-----------+ +-------+-----------------------------------------+-----------+
| 50 | End with NEXT-CSID, PSP, USP & USD | This I-D. | | 50 | End with NEXT-CSID, PSP, USP & USD | RFC 9800 |
+-------+-----------------------------------------+-----------+ +-------+-----------------------------------------+-----------+
| 52 | End.X with NEXT-CSID | This I-D. | | 52 | End.X with NEXT-CSID | RFC 9800 |
+-------+-----------------------------------------+-----------+ +-------+-----------------------------------------+-----------+
| 53 | End.X with NEXT-CSID & PSP | This I-D. | | 53 | End.X with NEXT-CSID & PSP | RFC 9800 |
+-------+-----------------------------------------+-----------+ +-------+-----------------------------------------+-----------+
| 54 | End.X with NEXT-CSID & USP | This I-D. | | 54 | End.X with NEXT-CSID & USP | RFC 9800 |
+-------+-----------------------------------------+-----------+ +-------+-----------------------------------------+-----------+
| 55 | End.X with NEXT-CSID, PSP & USP | This I-D. | | 55 | End.X with NEXT-CSID, PSP & USP | RFC 9800 |
+-------+-----------------------------------------+-----------+ +-------+-----------------------------------------+-----------+
| 56 | End.X with NEXT-CSID & USD | This I-D. | | 56 | End.X with NEXT-CSID & USD | RFC 9800 |
+-------+-----------------------------------------+-----------+ +-------+-----------------------------------------+-----------+
| 57 | End.X with NEXT-CSID, PSP & USD | This I-D. | | 57 | End.X with NEXT-CSID, PSP & USD | RFC 9800 |
+-------+-----------------------------------------+-----------+ +-------+-----------------------------------------+-----------+
| 58 | End.X with NEXT-CSID, USP & USD | This I-D. | | 58 | End.X with NEXT-CSID, USP & USD | RFC 9800 |
+-------+-----------------------------------------+-----------+ +-------+-----------------------------------------+-----------+
| 59 | End.X with NEXT-CSID, PSP, USP & USD | This I-D. | | 59 | End.X with NEXT-CSID, PSP, USP & USD | RFC 9800 |
+-------+-----------------------------------------+-----------+ +-------+-----------------------------------------+-----------+
| 85 | End.T with NEXT-CSID | This I-D. | | 85 | End.T with NEXT-CSID | RFC 9800 |
+-------+-----------------------------------------+-----------+ +-------+-----------------------------------------+-----------+
| 86 | End.T with NEXT-CSID & PSP | This I-D. | | 86 | End.T with NEXT-CSID & PSP | RFC 9800 |
+-------+-----------------------------------------+-----------+ +-------+-----------------------------------------+-----------+
| 87 | End.T with NEXT-CSID & USP | This I-D. | | 87 | End.T with NEXT-CSID & USP | RFC 9800 |
+-------+-----------------------------------------+-----------+ +-------+-----------------------------------------+-----------+
| 88 | End.T with NEXT-CSID, PSP & USP | This I-D. | | 88 | End.T with NEXT-CSID, PSP & USP | RFC 9800 |
+-------+-----------------------------------------+-----------+ +-------+-----------------------------------------+-----------+
| 89 | End.T with NEXT-CSID & USD | This I-D. | | 89 | End.T with NEXT-CSID & USD | RFC 9800 |
+-------+-----------------------------------------+-----------+ +-------+-----------------------------------------+-----------+
| 90 | End.T with NEXT-CSID, PSP & USD | This I-D. | | 90 | End.T with NEXT-CSID, PSP & USD | RFC 9800 |
+-------+-----------------------------------------+-----------+ +-------+-----------------------------------------+-----------+
| 91 | End.T with NEXT-CSID, USP & USD | This I-D. | | 91 | End.T with NEXT-CSID, USP & USD | RFC 9800 |
+-------+-----------------------------------------+-----------+ +-------+-----------------------------------------+-----------+
| 92 | End.T with NEXT-CSID, PSP, USP & USD | This I-D. | | 92 | End.T with NEXT-CSID, PSP, USP & USD | RFC 9800 |
+-------+-----------------------------------------+-----------+ +-------+-----------------------------------------+-----------+
| 93 | End.B6.Encaps with NEXT-CSID | This I-D. | | 93 | End.B6.Encaps with NEXT-CSID | RFC 9800 |
+-------+-----------------------------------------+-----------+ +-------+-----------------------------------------+-----------+
| 94 | End.B6.Encaps.Red with NEXT-CSID | This I-D. | | 94 | End.B6.Encaps.Red with NEXT-CSID | RFC 9800 |
+-------+-----------------------------------------+-----------+ +-------+-----------------------------------------+-----------+
| 95 | End.BM with NEXT-CSID | This I-D. | | 95 | End.BM with NEXT-CSID | RFC 9800 |
+-------+-----------------------------------------+-----------+ +-------+-----------------------------------------+-----------+
| 96 | End.LBS with NEXT-CSID | This I-D. | | 96 | End.LBS with NEXT-CSID | RFC 9800 |
+-------+-----------------------------------------+-----------+ +-------+-----------------------------------------+-----------+
| 97 | End.XLBS with NEXT-CSID | This I-D. | | 97 | End.XLBS with NEXT-CSID | RFC 9800 |
+-------+-----------------------------------------+-----------+ +-------+-----------------------------------------+-----------+
| 101 | End with REPLACE-CSID | This I-D. | | 101 | End with REPLACE-CSID | RFC 9800 |
+-------+-----------------------------------------+-----------+ +-------+-----------------------------------------+-----------+
| 102 | End with REPLACE-CSID & PSP | This I-D. | | 102 | End with REPLACE-CSID & PSP | RFC 9800 |
+-------+-----------------------------------------+-----------+ +-------+-----------------------------------------+-----------+
| 103 | End with REPLACE-CSID & USP | This I-D. | | 103 | End with REPLACE-CSID & USP | RFC 9800 |
+-------+-----------------------------------------+-----------+ +-------+-----------------------------------------+-----------+
| 104 | End with REPLACE-CSID, PSP & USP | This I-D. | | 104 | End with REPLACE-CSID, PSP & USP | RFC 9800 |
+-------+-----------------------------------------+-----------+ +-------+-----------------------------------------+-----------+
| 105 | End.X with REPLACE-CSID | This I-D. | | 105 | End.X with REPLACE-CSID | RFC 9800 |
+-------+-----------------------------------------+-----------+ +-------+-----------------------------------------+-----------+
| 106 | End.X with REPLACE-CSID & PSP | This I-D. | | 106 | End.X with REPLACE-CSID & PSP | RFC 9800 |
+-------+-----------------------------------------+-----------+ +-------+-----------------------------------------+-----------+
| 107 | End.X with REPLACE-CSID & USP | This I-D. | | 107 | End.X with REPLACE-CSID & USP | RFC 9800 |
+-------+-----------------------------------------+-----------+ +-------+-----------------------------------------+-----------+
| 108 | End.X with REPLACE-CSID, PSP & USP | This I-D. | | 108 | End.X with REPLACE-CSID, PSP & USP | RFC 9800 |
+-------+-----------------------------------------+-----------+ +-------+-----------------------------------------+-----------+
| 109 | End.T with REPLACE-CSID | This I-D. | | 109 | End.T with REPLACE-CSID | RFC 9800 |
+-------+-----------------------------------------+-----------+ +-------+-----------------------------------------+-----------+
| 110 | End.T with REPLACE-CSID & PSP | This I-D. | | 110 | End.T with REPLACE-CSID & PSP | RFC 9800 |
+-------+-----------------------------------------+-----------+ +-------+-----------------------------------------+-----------+
| 111 | End.T with REPLACE-CSID & USP | This I-D. | | 111 | End.T with REPLACE-CSID & USP | RFC 9800 |
+-------+-----------------------------------------+-----------+ +-------+-----------------------------------------+-----------+
| 112 | End.T with REPLACE-CSID, PSP & USP | This I-D. | | 112 | End.T with REPLACE-CSID, PSP & USP | RFC 9800 |
+-------+-----------------------------------------+-----------+ +-------+-----------------------------------------+-----------+
| 114 | End.B6.Encaps with REPLACE-CSID | This I-D. | | 114 | End.B6.Encaps with REPLACE-CSID | RFC 9800 |
+-------+-----------------------------------------+-----------+ +-------+-----------------------------------------+-----------+
| 115 | End.BM with REPLACE-CSID | This I-D. | | 115 | End.BM with REPLACE-CSID | RFC 9800 |
+-------+-----------------------------------------+-----------+ +-------+-----------------------------------------+-----------+
| 116 | End.DX6 with REPLACE-CSID | This I-D. | | 116 | End.DX6 with REPLACE-CSID | RFC 9800 |
+-------+-----------------------------------------+-----------+ +-------+-----------------------------------------+-----------+
| 117 | End.DX4 with REPLACE-CSID | This I-D. | | 117 | End.DX4 with REPLACE-CSID | RFC 9800 |
+-------+-----------------------------------------+-----------+ +-------+-----------------------------------------+-----------+
| 118 | End.DT6 with REPLACE-CSID | This I-D. | | 118 | End.DT6 with REPLACE-CSID | RFC 9800 |
+-------+-----------------------------------------+-----------+ +-------+-----------------------------------------+-----------+
| 119 | End.DT4 with REPLACE-CSID | This I-D. | | 119 | End.DT4 with REPLACE-CSID | RFC 9800 |
+-------+-----------------------------------------+-----------+ +-------+-----------------------------------------+-----------+
| 120 | End.DT46 with REPLACE-CSID | This I-D. | | 120 | End.DT46 with REPLACE-CSID | RFC 9800 |
+-------+-----------------------------------------+-----------+ +-------+-----------------------------------------+-----------+
| 121 | End.DX2 with REPLACE-CSID | This I-D. | | 121 | End.DX2 with REPLACE-CSID | RFC 9800 |
+-------+-----------------------------------------+-----------+ +-------+-----------------------------------------+-----------+
| 122 | End.DX2V with REPLACE-CSID | This I-D. | | 122 | End.DX2V with REPLACE-CSID | RFC 9800 |
+-------+-----------------------------------------+-----------+ +-------+-----------------------------------------+-----------+
| 123 | End.DT2U with REPLACE-CSID | This I-D. | | 123 | End.DT2U with REPLACE-CSID | RFC 9800 |
+-------+-----------------------------------------+-----------+ +-------+-----------------------------------------+-----------+
| 124 | End.DT2M with REPLACE-CSID | This I-D. | | 124 | End.DT2M with REPLACE-CSID | RFC 9800 |
+-------+-----------------------------------------+-----------+ +-------+-----------------------------------------+-----------+
| 127 | End.B6.Encaps.Red with REPLACE-CSID | This I-D. | | 127 | End.B6.Encaps.Red with REPLACE-CSID | RFC 9800 |
+-------+-----------------------------------------+-----------+ +-------+-----------------------------------------+-----------+
| 128 | End with REPLACE-CSID & USD | This I-D. | | 128 | End with REPLACE-CSID & USD | RFC 9800 |
+-------+-----------------------------------------+-----------+ +-------+-----------------------------------------+-----------+
| 129 | End with REPLACE-CSID, PSP & USD | This I-D. | | 129 | End with REPLACE-CSID, PSP & USD | RFC 9800 |
+-------+-----------------------------------------+-----------+ +-------+-----------------------------------------+-----------+
| 130 | End with REPLACE-CSID, USP & USD | This I-D. | | 130 | End with REPLACE-CSID, USP & USD | RFC 9800 |
+-------+-----------------------------------------+-----------+ +-------+-----------------------------------------+-----------+
| 131 | End with REPLACE-CSID, PSP, USP & USD | This I-D. | | 131 | End with REPLACE-CSID, PSP, USP & USD | RFC 9800 |
+-------+-----------------------------------------+-----------+ +-------+-----------------------------------------+-----------+
| 132 | End.X with REPLACE-CSID & USD | This I-D. | | 132 | End.X with REPLACE-CSID & USD | RFC 9800 |
+-------+-----------------------------------------+-----------+ +-------+-----------------------------------------+-----------+
| 133 | End.X with REPLACE-CSID, PSP & USD | This I-D. | | 133 | End.X with REPLACE-CSID, PSP & USD | RFC 9800 |
+-------+-----------------------------------------+-----------+ +-------+-----------------------------------------+-----------+
| 134 | End.X with REPLACE-CSID, USP & USD | This I-D. | | 134 | End.X with REPLACE-CSID, USP & USD | RFC 9800 |
+-------+-----------------------------------------+-----------+ +-------+-----------------------------------------+-----------+
| 135 | End.X with REPLACE-CSID, PSP, USP & USD | This I-D. | | 135 | End.X with REPLACE-CSID, PSP, USP & USD | RFC 9800 |
+-------+-----------------------------------------+-----------+ +-------+-----------------------------------------+-----------+
| 136 | End.T with REPLACE-CSID & USD | This I-D. | | 136 | End.T with REPLACE-CSID & USD | RFC 9800 |
+-------+-----------------------------------------+-----------+ +-------+-----------------------------------------+-----------+
| 137 | End.T with REPLACE-CSID, PSP & USD | This I-D. | | 137 | End.T with REPLACE-CSID, PSP & USD | RFC 9800 |
+-------+-----------------------------------------+-----------+ +-------+-----------------------------------------+-----------+
| 138 | End.T with REPLACE-CSID, USP & USD | This I-D. | | 138 | End.T with REPLACE-CSID, USP & USD | RFC 9800 |
+-------+-----------------------------------------+-----------+ +-------+-----------------------------------------+-----------+
| 139 | End.T with REPLACE-CSID, PSP, USP & USD | This I-D. | | 139 | End.T with REPLACE-CSID, PSP, USP & USD | RFC 9800 |
+-------+-----------------------------------------+-----------+ +-------+-----------------------------------------+-----------+
| 140 | End.LBS with REPLACE-CSID | This I-D. | | 140 | End.LBS with REPLACE-CSID | RFC 9800 |
+-------+-----------------------------------------+-----------+ +-------+-----------------------------------------+-----------+
| 141 | End.XLBS with REPLACE-CSID | This I-D. | | 141 | End.XLBS with REPLACE-CSID | RFC 9800 |
+-------+-----------------------------------------+-----------+ +-------+-----------------------------------------+-----------+
Table 1: Registration List Table 1: SRv6 Endpoint Behaviors Registration List
14. Acknowledgements
The authors would like to thank Kamran Raza, Xing Jiang, YuanChao Su,
Han Li, Yisong Liu, Martin Vigoureux, Joel Halpern, and Tal Mizrahi
for their insightful feedback and suggestions.
The authors would also like to thank Andrew Alston, Linda Dunbar,
Adrian Farrel, Boris Hassanov, Alvaro Retana, and Gunter Van de Velde
for their thorough review of this document.
15. References 13. References
15.1. Normative References 13.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997, DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>. <https://www.rfc-editor.org/info/rfc2119>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>. May 2017, <https://www.rfc-editor.org/info/rfc8174>.
skipping to change at page 55, line 5 skipping to change at line 1997
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>.
15.2. Informative References 13.2. Informative References
[EANTC-23] European Advanced Networking Test Center (EANTC), "Multi-
Vendor MPLS SDN Interoperability Test Report 2023", 18
April 2023, <https://eantc.de/wp-content/uploads/2023/04/
EANTC-InteropTest2023-TestReport.pdf>.
[EANTC-24] European Advanced Networking Test Center (EANTC), "Multi- [BGP-LS-SR]
Vendor MPLS SDN Interoperability Test Report 2024", April Previdi, S., Talaulikar, K., Ed., Dong, J., Gredler, H.,
2024, <https://eantc.de/wp-content/uploads/2023/12/EANTC- and J. Tantsura, "Advertisement of Segment Routing
MPLSSDNInterop2024-TestReport-v1.3.pdf>. Policies using BGP Link-State", Work in Progress,
Internet-Draft, draft-ietf-idr-bgp-ls-sr-policy-17, 6
March 2025, <https://datatracker.ietf.org/doc/html/draft-
ietf-idr-bgp-ls-sr-policy-17>.
[GKP94] Graham, R., Knuth, D., and O. Patashnik, "Concrete [GKP94] Graham, R., Knuth, D., and O. Patashnik, "Concrete
Mathematics: A Foundation for Computer Science", Mathematics: A Foundation for Computer Science",
ISBN 9780201558029, 1994. ISBN 9780201558029, 1994.
[I-D.ietf-idr-bgp-ls-sr-policy]
Previdi, S., Talaulikar, K., Dong, J., Gredler, H., and J.
Tantsura, "Advertisement of Segment Routing Policies using
BGP Link-State", Work in Progress, Internet-Draft, draft-
ietf-idr-bgp-ls-sr-policy-10, 9 December 2024,
<https://datatracker.ietf.org/doc/html/draft-ietf-idr-bgp-
ls-sr-policy-10>.
[I-D.ietf-idr-sr-policy-safi]
Previdi, S., Filsfils, C., Talaulikar, K., Mattes, P., and
D. Jain, "Advertising Segment Routing Policies in BGP",
Work in Progress, Internet-Draft, draft-ietf-idr-sr-
policy-safi-11, 31 January 2025,
<https://datatracker.ietf.org/api/v1/doc/document/draft-
ietf-idr-sr-policy-safi/>.
[IMPL-CISCO-8000]
Cisco Systems, "Segment Routing Configuration Guide for
Cisco 8000 Series Routers", 4 November 2022,
<https://www.cisco.com/c/en/us/td/docs/iosxr/cisco8000/
segment-routing/75x/b-segment-routing-cg-cisco8000-75x/
configuring-segment-routing-over-ipv6-srv6-micro-
sids.html>.
[IMPL-CISCO-ASR9000]
Cisco Systems, "Segment Routing Configuration Guide for
Cisco ASR 9000 Series Routers", 6 November 2022,
<https://www.cisco.com/c/en/us/td/docs/routers/asr9000/
software/asr9k-r7-5/segment-routing/configuration/guide/b-
segment-routing-cg-asr9000-75x/configure-srv6-micro-
sid.html>.
[IMPL-CISCO-NCS540]
Cisco Systems, "Segment Routing Configuration Guide for
Cisco NCS 540 Series Routers", 2 November 2022,
<https://www.cisco.com/c/en/us/td/docs/iosxr/ncs5xx/
segment-routing/73x/b-segment-routing-cg-73x-ncs540/
configure-srv6.html>.
[IMPL-CISCO-NCS5500]
Cisco Systems, "Segment Routing Configuration Guide for
Cisco NCS 5500 Series Routers", 6 November 2022,
<https://www.cisco.com/c/en/us/td/docs/iosxr/ncs5500/
segment-routing/73x/b-segment-routing-cg-ncs5500-73x/
configure-srv6-micro-sid.html>.
[IMPL-CISCO-NCS560]
Cisco Systems, "Segment Routing Configuration Guide for
Cisco NCS 560 Series Routers", 14 October 2022,
<https://www.cisco.com/c/en/us/td/docs/iosxr/ncs560/
segment-routing/76x/b-segment-routing-cg-76x-ncs560/m-
configure-srv6-usid-ncs5xx.html>.
[IMPL-CISCO-NCS5700]
Cisco Systems, "Segment Routing Configuration Guide for
Cisco NCS 5700 Series Routers", 6 November 2022,
<https://www.cisco.com/c/en/us/td/docs/iosxr/ncs5500/
segment-routing/75x/b-segment-routing-cg-ncs5500-75x/
configure-srv6-micro-sid.html>.
[IMPL-NOKIA-20.10]
Nokia, "Segment Routing and PCE User Guide", December
2022, <https://documentation.nokia.com/sr/22-
10/books/Segment%20Routing%20and%20PCE%20User%20Guide/
segment-rout-with-ipv6-data-plane-srv6.html>.
[IMPL-OSS-LINUX]
Abeni, P., "Add NEXT-CSID support for SRv6 End behavior",
20 September 2022,
<https://git.kernel.org/pub/scm/linux/kernel/git/netdev/
net-next.git/
commit/?id=cec9d59e89362809f17f2d854faf52966216da13>.
[IMPL-OSS-ONOS]
Open Networking Foundation, "Stratum CMCC G-SRv6 Project",
24 March 2021,
<https://wiki.opennetworking.org/display/COM/
Stratum+CMCC+G-SRv6+Project>.
[IMPL-OSS-OPEN-SRV6]
"Open SRv6 Project", n.d.,
<http://opensrv6.org.cn/en/srv6-2/>.
[IMPL-OSS-P4]
Salsano, S. and A. Tulumello, "SRv6 uSID (micro SID)
implementation on P4", 3 January 2021,
<https://github.com/netgroup/p4-srv6-usid>.
[IMPL-OSS-SAI]
Agrawal, A., "Added new behaviors to support uSID
instruction", 8 June 2021,
<https://github.com/opencomputeproject/SAI/pull/1231/
commits/02e58d95ad966ca9efc24eb9e0c0fa10b21de2a4>.
[IMPL-OSS-SONIC]
Shah, S. and R. Sudarshan, "SONiC uSID", 21 August 2022,
<https://github.com/sonic-net/SONiC/blob/master/doc/srv6/
SRv6_uSID.md>.
[IMPL-OSS-VPP]
FD.io, "Srv6 cli reference", n.d., <https://s3-
docs.fd.io/vpp/23.02/cli-reference/clis/
clicmd_src_vnet_srv6.html>.
[RFC4786] Abley, J. and K. Lindqvist, "Operation of Anycast [RFC4786] Abley, J. and K. Lindqvist, "Operation of Anycast
Services", BCP 126, RFC 4786, DOI 10.17487/RFC4786, Services", BCP 126, RFC 4786, DOI 10.17487/RFC4786,
December 2006, <https://www.rfc-editor.org/info/rfc4786>. December 2006, <https://www.rfc-editor.org/info/rfc4786>.
[RFC7942] Sheffer, Y. and A. Farrel, "Improving Awareness of Running
Code: The Implementation Status Section", BCP 205,
RFC 7942, DOI 10.17487/RFC7942, July 2016,
<https://www.rfc-editor.org/info/rfc7942>.
[RFC9252] Dawra, G., Ed., Talaulikar, K., Ed., Raszuk, R., Decraene, [RFC9252] Dawra, G., Ed., Talaulikar, K., Ed., Raszuk, R., Decraene,
B., Zhuang, S., and J. Rabadan, "BGP Overlay Services B., Zhuang, S., and J. Rabadan, "BGP Overlay Services
Based on Segment Routing over IPv6 (SRv6)", RFC 9252, Based on Segment Routing over IPv6 (SRv6)", RFC 9252,
DOI 10.17487/RFC9252, July 2022, DOI 10.17487/RFC9252, July 2022,
<https://www.rfc-editor.org/info/rfc9252>. <https://www.rfc-editor.org/info/rfc9252>.
[RFC9259] Ali, Z., Filsfils, C., Matsushima, S., Voyer, D., and M. [RFC9259] 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 over IPv6 (SRv6)", RFC 9259, in Segment Routing over IPv6 (SRv6)", RFC 9259,
DOI 10.17487/RFC9259, June 2022, DOI 10.17487/RFC9259, June 2022,
skipping to change at page 58, line 37 skipping to change at line 2059
Identifiers in the IPv6 Addressing Architecture", Identifiers in the IPv6 Addressing Architecture",
RFC 9602, DOI 10.17487/RFC9602, October 2024, RFC 9602, DOI 10.17487/RFC9602, October 2024,
<https://www.rfc-editor.org/info/rfc9602>. <https://www.rfc-editor.org/info/rfc9602>.
[RFC9603] Li, C., Ed., Kaladharan, P., Sivabalan, S., Koldychev, M., [RFC9603] Li, C., Ed., Kaladharan, P., Sivabalan, S., Koldychev, M.,
and Y. Zhu, "Path Computation Element Communication and Y. Zhu, "Path Computation Element Communication
Protocol (PCEP) Extensions for IPv6 Segment Routing", Protocol (PCEP) Extensions for IPv6 Segment Routing",
RFC 9603, DOI 10.17487/RFC9603, July 2024, RFC 9603, DOI 10.17487/RFC9603, July 2024,
<https://www.rfc-editor.org/info/rfc9603>. <https://www.rfc-editor.org/info/rfc9603>.
[SPRING-WG-POLICIES] [SR-BGP] Previdi, S., Filsfils, C., Talaulikar, K., Ed., Mattes,
SPRING Working Group Chairs, "SPRING Working Group P., and D. Jain, "Advertising Segment Routing Policies in
Policies", 14 October 2022, BGP", Work in Progress, Internet-Draft, draft-ietf-idr-sr-
<https://wiki.ietf.org/en/group/spring/WG_Policies>. policy-safi-13, 6 February 2025,
<https://datatracker.ietf.org/doc/html/draft-ietf-idr-sr-
policy-safi-13>.
Appendix A. Complete pseudocodes Appendix A. Complete Pseudocodes
The content of this section is purely informative rendering of the The content of this section is purely informative rendering of the
pseudocodes of [RFC8986] with the modifications in this document. pseudocodes of [RFC8986] with the modifications in this document.
This rendering may not be used as a reference. This rendering may not be used as a reference.
A.1. End with NEXT-CSID A.1. End with NEXT-CSID
When processing the SRH of a packet matching a FIB entry locally When processing the SRH of a packet matching a FIB entry locally
instantiated as an End SID with the NEXT-CSID flavor: instantiated as an End SID with the NEXT-CSID flavor:
skipping to change at page 59, line 20 skipping to change at line 2092
N04. } N04. }
N05. Copy DA.Argument into the bits [LBL..(LBL+AL-1)] of the N05. Copy DA.Argument into the bits [LBL..(LBL+AL-1)] of the
Destination Address. Destination Address.
N06. Set the bits [(LBL+AL)..127] of the Destination Address to N06. Set the bits [(LBL+AL)..127] of the Destination Address to
zero. zero.
N07. Decrement IPv6 Hop Limit by 1. N07. Decrement IPv6 Hop Limit by 1.
N08. Submit the packet to the egress IPv6 FIB lookup for N08. Submit the packet to the egress IPv6 FIB lookup for
transmission to the next destination. transmission to the next destination.
N09. } N09. }
S02. If (Segments Left == 0) { S02. If (Segments Left == 0) {
S03. Stop processing the SRH, and proceed to process the next S03. Stop processing the SRH and proceed to process the next
header in the packet, whose type is identified by header in the packet, whose type is identified by
the Next Header field in the routing header. the Next Header field in the routing header.
S04. } S04. }
S05. If (IPv6 Hop Limit <= 1) { S05. If (IPv6 Hop Limit <= 1) {
S06. Send an ICMP Time Exceeded message to the Source Address S06. Send an ICMP Time Exceeded message to the Source Address
with Code 0 (Hop limit exceeded in transit), with Code 0 (Hop limit exceeded in transit),
interrupt packet processing, and discard the packet. interrupt packet processing, and discard the packet.
S07. } S07. }
S08. max_LE = (Hdr Ext Len / 2) - 1 S08. max_LE = (Hdr Ext Len / 2) - 1
S09. If ((Last Entry > max_LE) or (Segments Left > Last Entry+1)) { S09. If ((Last Entry > max_LE) or (Segments Left > Last Entry+1)) {
skipping to change at page 61, line 20 skipping to change at line 2166
N04. } N04. }
N05. Copy DA.Argument into the bits [LBL..(LBL+AL-1)] of the N05. Copy DA.Argument into the bits [LBL..(LBL+AL-1)] of the
Destination Address. Destination Address.
N06. Set the bits [(LBL+AL)..127] of the Destination Address to N06. Set the bits [(LBL+AL)..127] of the Destination Address to
zero. zero.
N07. Decrement IPv6 Hop Limit by 1. N07. Decrement IPv6 Hop Limit by 1.
N08. Submit the packet to the IPv6 module for transmission to the N08. Submit the packet to the IPv6 module for transmission to the
new destination via a member of J. new destination via a member of J.
N09. } N09. }
S02. If (Segments Left == 0) { S02. If (Segments Left == 0) {
S03. Stop processing the SRH, and proceed to process the next S03. Stop processing the SRH and proceed to process the next
header in the packet, whose type is identified by header in the packet, whose type is identified by
the Next Header field in the routing header. the Next Header field in the routing header.
S04. } S04. }
S05. If (IPv6 Hop Limit <= 1) { S05. If (IPv6 Hop Limit <= 1) {
S06. Send an ICMP Time Exceeded message to the Source Address S06. Send an ICMP Time Exceeded message to the Source Address
with Code 0 (Hop limit exceeded in transit), with Code 0 (Hop limit exceeded in transit),
interrupt packet processing, and discard the packet. interrupt packet processing, and discard the packet.
S07. } S07. }
S08. max_LE = (Hdr Ext Len / 2) - 1 S08. max_LE = (Hdr Ext Len / 2) - 1
S09. If ((Last Entry > max_LE) or (Segments Left > Last Entry+1)) { S09. If ((Last Entry > max_LE) or (Segments Left > Last Entry+1)) {
skipping to change at page 63, line 21 skipping to change at line 2241
N05. Copy DA.Argument into the bits [LBL..(LBL+AL-1)] of the N05. Copy DA.Argument into the bits [LBL..(LBL+AL-1)] of the
Destination Address. Destination Address.
N06. Set the bits [(LBL+AL)..127] of the Destination Address to N06. Set the bits [(LBL+AL)..127] of the Destination Address to
zero. zero.
N07. Decrement IPv6 Hop Limit by 1. N07. Decrement IPv6 Hop Limit by 1.
N08.1. Set the packet's associated FIB table to T. N08.1. Set the packet's associated FIB table to T.
N08.2. Submit the packet to the egress IPv6 FIB lookup for N08.2. Submit the packet to the egress IPv6 FIB lookup for
transmission to the new destination. transmission to the new destination.
N09. } N09. }
S02. If (Segments Left == 0) { S02. If (Segments Left == 0) {
S03. Stop processing the SRH, and proceed to process the next S03. Stop processing the SRH and proceed to process the next
header in the packet, whose type is identified by header in the packet, whose type is identified by
the Next Header field in the routing header. the Next Header field in the routing header.
S04. } S04. }
S05. If (IPv6 Hop Limit <= 1) { S05. If (IPv6 Hop Limit <= 1) {
S06. Send an ICMP Time Exceeded message to the Source Address S06. Send an ICMP Time Exceeded message to the Source Address
with Code 0 (Hop limit exceeded in transit), with Code 0 (Hop limit exceeded in transit),
interrupt packet processing, and discard the packet. interrupt packet processing, and discard the packet.
S07. } S07. }
S08. max_LE = (Hdr Ext Len / 2) - 1 S08. max_LE = (Hdr Ext Len / 2) - 1
S09. If ((Last Entry > max_LE) or (Segments Left > Last Entry+1)) { S09. If ((Last Entry > max_LE) or (Segments Left > Last Entry+1)) {
skipping to change at page 65, line 25 skipping to change at line 2322
N07. Decrement IPv6 Hop Limit by 1. N07. Decrement IPv6 Hop Limit by 1.
N08.1. Push a new IPv6 header with its own SRH containing B. N08.1. Push a new IPv6 header with its own SRH containing B.
N08.2. Set the outer IPv6 SA to A. N08.2. Set the outer IPv6 SA to A.
N08.3. Set the outer IPv6 DA to the first SID of B. N08.3. Set the outer IPv6 DA to the first SID of B.
N08.4. Set the outer Payload Length, Traffic Class, Flow Label, N08.4. Set the outer Payload Length, Traffic Class, Flow Label,
Hop Limit, and Next Header fields. Hop Limit, and Next Header fields.
N08.5. Submit the packet to the egress IPv6 FIB lookup for N08.5. Submit the packet to the egress IPv6 FIB lookup for
transmission to the next destination. transmission to the next destination.
N09. } N09. }
S02. If (Segments Left == 0) { S02. If (Segments Left == 0) {
S03. Stop processing the SRH, and proceed to process the next S03. Stop processing the SRH and proceed to process the next
header in the packet, whose type is identified by header in the packet, whose type is identified by
the Next Header field in the routing header. the Next Header field in the routing header.
S04. } S04. }
S05. If (IPv6 Hop Limit <= 1) { S05. If (IPv6 Hop Limit <= 1) {
S06. Send an ICMP Time Exceeded message to the Source Address S06. Send an ICMP Time Exceeded message to the Source Address
with Code 0 (Hop limit exceeded in transit), with Code 0 (Hop limit exceeded in transit),
interrupt packet processing, and discard the packet. interrupt packet processing, and discard the packet.
S07. } S07. }
S08. max_LE = (Hdr Ext Len / 2) - 1 S08. max_LE = (Hdr Ext Len / 2) - 1
S09. If ((Last Entry > max_LE) or (Segments Left > Last Entry+1)) { S09. If ((Last Entry > max_LE) or (Segments Left > Last Entry+1)) {
skipping to change at page 67, line 20 skipping to change at line 2407
N04. } N04. }
N05. Copy DA.Argument into the bits [LBL..(LBL+AL-1)] of the N05. Copy DA.Argument into the bits [LBL..(LBL+AL-1)] of the
Destination Address. Destination Address.
N06. Set the bits [(LBL+AL)..127] of the Destination Address to N06. Set the bits [(LBL+AL)..127] of the Destination Address to
zero. zero.
N07. Decrement IPv6 Hop Limit by 1. N07. Decrement IPv6 Hop Limit by 1.
N08.1. Push the MPLS label stack for B. N08.1. Push the MPLS label stack for B.
N08.2. Submit the packet to the MPLS engine for transmission. N08.2. Submit the packet to the MPLS engine for transmission.
N09. } N09. }
S02. If (Segments Left == 0) { S02. If (Segments Left == 0) {
S03. Stop processing the SRH, and proceed to process the next S03. Stop processing the SRH and proceed to process the next
header in the packet, whose type is identified by header in the packet, whose type is identified by
the Next Header field in the routing header. the Next Header field in the routing header.
S04. } S04. }
S05. If (IPv6 Hop Limit <= 1) { S05. If (IPv6 Hop Limit <= 1) {
S06. Send an ICMP Time Exceeded message to the Source Address S06. Send an ICMP Time Exceeded message to the Source Address
with Code 0 (Hop limit exceeded in transit), with Code 0 (Hop limit exceeded in transit),
interrupt packet processing, and discard the packet. interrupt packet processing, and discard the packet.
S07. } S07. }
S08. max_LE = (Hdr Ext Len / 2) - 1 S08. max_LE = (Hdr Ext Len / 2) - 1
S09. If ((Last Entry > max_LE) or (Segments Left > Last Entry+1)) { S09. If ((Last Entry > max_LE) or (Segments Left > Last Entry+1)) {
skipping to change at page 69, line 8 skipping to change at line 2470
S05. } S05. }
A.6. End with REPLACE-CSID A.6. End with REPLACE-CSID
When processing the SRH of a packet matching a FIB entry locally When processing the SRH of a packet matching a FIB entry locally
instantiated as an End SID with the REPLACE-CSID flavor: instantiated as an End SID with the REPLACE-CSID flavor:
S01. When an SRH is processed { S01. When an SRH is processed {
S02. If (Segments Left == 0 and (DA.Arg.Index == 0 or S02. If (Segments Left == 0 and (DA.Arg.Index == 0 or
Segment List[0][DA.Arg.Index-1] == 0)) { Segment List[0][DA.Arg.Index-1] == 0)) {
S03. Stop processing the SRH, and proceed to process the next S03. Stop processing the SRH and proceed to process the next
header in the packet, whose type is identified by header in the packet, whose type is identified by
the Next Header field in the routing header. the Next Header field in the routing header.
S04. } S04. }
S05. If (IPv6 Hop Limit <= 1) { S05. If (IPv6 Hop Limit <= 1) {
S06. Send an ICMP Time Exceeded message to the Source Address, S06. Send an ICMP Time Exceeded message to the Source Address,
Code 0 (Hop limit exceeded in transit), Code 0 (Hop limit exceeded in transit),
interrupt packet processing and discard the packet. interrupt packet processing and discard the packet.
S07. } S07. }
S08. max_LE = (Hdr Ext Len / 2) - 1 S08. max_LE = (Hdr Ext Len / 2) - 1
R01. If (DA.Arg.Index != 0) { R01. If (DA.Arg.Index != 0) {
skipping to change at page 71, line 8 skipping to change at line 2534
S05. } S05. }
A.7. End.X with REPLACE-CSID A.7. End.X with REPLACE-CSID
When processing the SRH of a packet matching a FIB entry locally When processing the SRH of a packet matching a FIB entry locally
instantiated as an End.X SID with the REPLACE-CSID flavor: instantiated as an End.X SID with the REPLACE-CSID flavor:
S01. When an SRH is processed { S01. When an SRH is processed {
S02. If (Segments Left == 0 and (DA.Arg.Index == 0 or S02. If (Segments Left == 0 and (DA.Arg.Index == 0 or
Segment List[0][DA.Arg.Index-1] == 0)) { Segment List[0][DA.Arg.Index-1] == 0)) {
S03. Stop processing the SRH, and proceed to process the next S03. Stop processing the SRH and proceed to process the next
header in the packet, whose type is identified by header in the packet, whose type is identified by
the Next Header field in the routing header. the Next Header field in the routing header.
S04. } S04. }
S05. If (IPv6 Hop Limit <= 1) { S05. If (IPv6 Hop Limit <= 1) {
S06. Send an ICMP Time Exceeded message to the Source Address, S06. Send an ICMP Time Exceeded message to the Source Address,
Code 0 (Hop limit exceeded in transit), Code 0 (Hop limit exceeded in transit),
interrupt packet processing and discard the packet. interrupt packet processing and discard the packet.
S07. } S07. }
S08. max_LE = (Hdr Ext Len / 2) - 1 S08. max_LE = (Hdr Ext Len / 2) - 1
R01. If (DA.Arg.Index != 0) { R01. If (DA.Arg.Index != 0) {
skipping to change at page 73, line 8 skipping to change at line 2598
S05. } S05. }
A.8. End.T with REPLACE-CSID A.8. End.T with REPLACE-CSID
When processing the SRH of a packet matching a FIB entry locally When processing the SRH of a packet matching a FIB entry locally
instantiated as an End.T SID with the REPLACE-CSID flavor: instantiated as an End.T SID with the REPLACE-CSID flavor:
S01. When an SRH is processed { S01. When an SRH is processed {
S02. If (Segments Left == 0 and (DA.Arg.Index == 0 or S02. If (Segments Left == 0 and (DA.Arg.Index == 0 or
Segment List[0][DA.Arg.Index-1] == 0)) { Segment List[0][DA.Arg.Index-1] == 0)) {
S03. Stop processing the SRH, and proceed to process the next S03. Stop processing the SRH and proceed to process the next
header in the packet, whose type is identified by header in the packet, whose type is identified by
the Next Header field in the routing header. the Next Header field in the routing header.
S04. } S04. }
S05. If (IPv6 Hop Limit <= 1) { S05. If (IPv6 Hop Limit <= 1) {
S06. Send an ICMP Time Exceeded message to the Source Address, S06. Send an ICMP Time Exceeded message to the Source Address,
Code 0 (Hop limit exceeded in transit), Code 0 (Hop limit exceeded in transit),
interrupt packet processing and discard the packet. interrupt packet processing and discard the packet.
S07. } S07. }
S08. max_LE = (Hdr Ext Len / 2) - 1 S08. max_LE = (Hdr Ext Len / 2) - 1
R01. If (DA.Arg.Index != 0) { R01. If (DA.Arg.Index != 0) {
skipping to change at page 74, line 25 skipping to change at line 2664
S05. } S05. }
A.9. End.B6.Encaps with REPLACE-CSID A.9. End.B6.Encaps with REPLACE-CSID
When processing the SRH of a packet matching a FIB entry locally When processing the SRH of a packet matching a FIB entry locally
instantiated as an End.B6.Encaps SID with the REPLACE-CSID flavor: instantiated as an End.B6.Encaps SID with the REPLACE-CSID flavor:
S01. When an SRH is processed { S01. When an SRH is processed {
S02. If (Segments Left == 0 and (DA.Arg.Index == 0 or S02. If (Segments Left == 0 and (DA.Arg.Index == 0 or
Segment List[0][DA.Arg.Index-1] == 0)) { Segment List[0][DA.Arg.Index-1] == 0)) {
S03. Stop processing the SRH, and proceed to process the next S03. Stop processing the SRH and proceed to process the next
header in the packet, whose type is identified by header in the packet, whose type is identified by
the Next Header field in the routing header. the Next Header field in the routing header.
S04. } S04. }
S05. If (IPv6 Hop Limit <= 1) { S05. If (IPv6 Hop Limit <= 1) {
S06. Send an ICMP Time Exceeded message to the Source Address, S06. Send an ICMP Time Exceeded message to the Source Address,
Code 0 (Hop limit exceeded in transit), Code 0 (Hop limit exceeded in transit),
interrupt packet processing and discard the packet. interrupt packet processing and discard the packet.
S07. } S07. }
S08. max_LE = (Hdr Ext Len / 2) - 1 S08. max_LE = (Hdr Ext Len / 2) - 1
R01. If (DA.Arg.Index != 0) { R01. If (DA.Arg.Index != 0) {
skipping to change at page 76, line 8 skipping to change at line 2738
S05. } S05. }
A.10. End.BM with REPLACE-CSID A.10. End.BM with REPLACE-CSID
When processing the SRH of a packet matching a FIB entry locally When processing the SRH of a packet matching a FIB entry locally
instantiated as an End.BM SID with the REPLACE-CSID flavor: instantiated as an End.BM SID with the REPLACE-CSID flavor:
S01. When an SRH is processed { S01. When an SRH is processed {
S02. If (Segments Left == 0 and (DA.Arg.Index == 0 or S02. If (Segments Left == 0 and (DA.Arg.Index == 0 or
Segment List[0][DA.Arg.Index-1] == 0)) { Segment List[0][DA.Arg.Index-1] == 0)) {
S03. Stop processing the SRH, and proceed to process the next S03. Stop processing the SRH and proceed to process the next
header in the packet, whose type is identified by header in the packet, whose type is identified by
the Next Header field in the routing header. the Next Header field in the routing header.
S04. } S04. }
S05. If (IPv6 Hop Limit <= 1) { S05. If (IPv6 Hop Limit <= 1) {
S06. Send an ICMP Time Exceeded message to the Source Address, S06. Send an ICMP Time Exceeded message to the Source Address,
Code 0 (Hop limit exceeded in transit), Code 0 (Hop limit exceeded in transit),
interrupt packet processing and discard the packet. interrupt packet processing and discard the packet.
S07. } S07. }
S08. max_LE = (Hdr Ext Len / 2) - 1 S08. max_LE = (Hdr Ext Len / 2) - 1
R01. If (DA.Arg.Index != 0) { R01. If (DA.Arg.Index != 0) {
skipping to change at page 77, line 4 skipping to change at line 2780
R16. Decrement Segments Left by 1. R16. Decrement Segments Left by 1.
R17. Set DA.Arg.Index to (128/LNFL - 1). R17. Set DA.Arg.Index to (128/LNFL - 1).
R18. } R18. }
R19. Decrement IPv6 Hop Limit by 1. R19. Decrement IPv6 Hop Limit by 1.
R20. Write Segment List[Segments Left][DA.Arg.Index] into the bits R20. Write Segment List[Segments Left][DA.Arg.Index] into the bits
[LBL..LBL+LNFL-1] of the Destination Address of the IPv6 [LBL..LBL+LNFL-1] of the Destination Address of the IPv6
header. header.
R21.1. Push the MPLS label stack for B. R21.1. Push the MPLS label stack for B.
R21.2. Submit the packet to the MPLS engine for transmission. R21.2. Submit the packet to the MPLS engine for transmission.
S16. } S16. }
When processing the Upper-Layer header of a packet matching a FIB When processing the Upper-Layer header of a packet matching a FIB
entry locally instantiated as an End.BM SID with the REPLACE-CSID entry locally instantiated as an End.BM SID with the REPLACE-CSID
flavor: flavor:
S01. If (Upper-Layer header type is allowed by local configuration) { S01. If (Upper-Layer header type is allowed by local configuration) {
S02. Proceed to process the Upper-Layer header S02. Proceed to process the Upper-Layer header
S03. } Else { S03. } Else {
S04. Send an ICMP Parameter Problem to the Source Address S04. Send an ICMP Parameter Problem to the Source Address
with Code 4 (SR Upper-layer Header Error) with Code 4 (SR Upper-layer Header Error)
and Pointer set to the offset of the Upper-Layer header, and Pointer set to the offset of the Upper-Layer header,
interrupt packet processing, and discard the packet. interrupt packet processing, and discard the packet.
S05. } S05. }
Acknowledgements
The authors would like to thank Kamran Raza, Xing Jiang, YuanChao Su,
Han Li, Yisong Liu, Martin Vigoureux, Joel Halpern, and Tal Mizrahi
for their insightful feedback and suggestions.
The authors would also like to thank Andrew Alston, Linda Dunbar,
Adrian Farrel, Boris Hassanov, Alvaro Retana, and Gunter Van de Velde
for their thorough review of this document.
Contributors Contributors
Liu Aihua Liu Aihua
ZTE Corporation ZTE Corporation
China China
Email: liu.aihua@zte.com.cn Email: liu.aihua@zte.com.cn
Dennis Cai Dennis Cai
Alibaba Alibaba
United States of America United States of America
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