Compressed SRv6 Segment List Encoding in SRH
draft-ietf-spring-srv6-srh-compression-04
The information below is for an old version of the document.
| Document | Type |
This is an older version of an Internet-Draft whose latest revision state is "Active".
|
|
|---|---|---|---|
| Authors | Weiqiang Cheng , Clarence Filsfils , Zhenbin Li , Bruno Decraene , Francois Clad | ||
| Last updated | 2023-03-31 | ||
| Replaces | draft-filsfilscheng-spring-srv6-srh-compression | ||
| RFC stream | Internet Engineering Task Force (IETF) | ||
| Formats | |||
| Reviews |
SECDIR Early Review due 2024-04-19
Incomplete
OPSDIR Early Review due 2024-04-19
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RTGDIR Early Review due 2024-04-19
Incomplete
INTDIR Early Review due 2024-04-19
Incomplete
|
||
| Additional resources | Mailing list discussion | ||
| Stream | WG state | WG Document | |
| Document shepherd | (None) | ||
| IESG | IESG state | I-D Exists | |
| Consensus boilerplate | Yes | ||
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| Send notices to | (None) |
draft-ietf-spring-srv6-srh-compression-04
SPRING W. Cheng, Ed.
Internet-Draft China Mobile
Intended status: Standards Track C. Filsfils
Expires: 2 October 2023 Cisco Systems, Inc.
Z. Li
Huawei Technologies
B. Decraene
Orange
F. Clad, Ed.
Cisco Systems, Inc.
31 March 2023
Compressed SRv6 Segment List Encoding in SRH
draft-ietf-spring-srv6-srh-compression-04
Abstract
This document specifies new flavors for the SR endpoint behaviors
defined in RFC 8986, which enable a compressed SRv6 Segment-List
encoding in the Segment Routing Header (SRH).
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on 2 October 2023.
Copyright Notice
Copyright (c) 2023 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents (https://trustee.ietf.org/
license-info) in effect on the date of publication of this document.
Please review these documents carefully, as they describe your rights
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and restrictions with respect to this document. Code Components
extracted from this document must include Revised BSD License text as
described in Section 4.e of the Trust Legal Provisions and are
provided without warranty as described in the Revised BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4
2.1. Requirements Language . . . . . . . . . . . . . . . . . . 4
3. Basic Concepts . . . . . . . . . . . . . . . . . . . . . . . 4
4. SR Endpoint Flavors . . . . . . . . . . . . . . . . . . . . . 5
4.1. NEXT-C-SID Flavor . . . . . . . . . . . . . . . . . . . . 6
4.1.1. End with NEXT-C-SID . . . . . . . . . . . . . . . . . 6
4.1.2. End.X with NEXT-C-SID . . . . . . . . . . . . . . . . 7
4.1.3. End.T with NEXT-C-SID . . . . . . . . . . . . . . . . 8
4.1.4. End.B6.Encaps with NEXT-C-SID . . . . . . . . . . . . 8
4.1.5. End.B6.Encaps.Red with NEXT-C-SID . . . . . . . . . . 9
4.1.6. End.BM with NEXT-C-SID . . . . . . . . . . . . . . . 9
4.1.7. Combination with PSP, USP and USD flavors . . . . . . 9
4.2. REPLACE-C-SID Flavor . . . . . . . . . . . . . . . . . . 9
4.2.1. End with REPLACE-C-SID . . . . . . . . . . . . . . . 10
4.2.2. End.X with REPLACE-C-SID . . . . . . . . . . . . . . 12
4.2.3. End.T with REPLACE-C-SID . . . . . . . . . . . . . . 12
4.2.4. End.B6.Encaps with REPLACE-C-SID . . . . . . . . . . 12
4.2.5. End.B6.Encaps.Red with REPLACE-C-SID . . . . . . . . 13
4.2.6. End.BM with REPLACE-C-SID . . . . . . . . . . . . . . 13
4.2.7. End.DX and End.DT with REPLACE-C-SID . . . . . . . . 13
4.2.8. Combination with PSP, USP, and USD flavors . . . . . 14
5. C-SID Allocation . . . . . . . . . . . . . . . . . . . . . . 14
5.1. Global C-SID . . . . . . . . . . . . . . . . . . . . . . 15
5.2. Local C-SID . . . . . . . . . . . . . . . . . . . . . . . 15
6. C-SID and Locator-Block Length . . . . . . . . . . . . . . . 15
6.1. C-SID Length . . . . . . . . . . . . . . . . . . . . . . 15
6.2. Locator-Block Length . . . . . . . . . . . . . . . . . . 16
6.3. GIB/LIB Usage . . . . . . . . . . . . . . . . . . . . . . 16
6.4. Recommended Installation of C-SIDs in FIB . . . . . . . . 17
7. SR Source Node . . . . . . . . . . . . . . . . . . . . . . . 18
7.1. Rules for NEXT-C-SID flavor uncompressed SID lists . . . 20
7.2. Rules for REPLACE-C-SID flavor uncompressed SID lists . . 21
8. Inter Routing Domains with the End.XPS behavior . . . . . . . 21
9. Control Plane . . . . . . . . . . . . . . . . . . . . . . . . 23
10. Operational Considerations . . . . . . . . . . . . . . . . . 24
10.1. Ping a SID without a Segment List . . . . . . . . . . . 24
10.2. Ping a SID via a Segment List . . . . . . . . . . . . . 24
10.3. ICMP Error Processing . . . . . . . . . . . . . . . . . 24
11. Illustrations . . . . . . . . . . . . . . . . . . . . . . . . 25
12. Deployment Model . . . . . . . . . . . . . . . . . . . . . . 25
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13. Implementation Status . . . . . . . . . . . . . . . . . . . . 25
13.1. Cisco Systems . . . . . . . . . . . . . . . . . . . . . 26
13.2. Huawei Technologies . . . . . . . . . . . . . . . . . . 26
13.3. Nokia . . . . . . . . . . . . . . . . . . . . . . . . . 27
13.4. Arrcus . . . . . . . . . . . . . . . . . . . . . . . . . 28
13.5. Marvell . . . . . . . . . . . . . . . . . . . . . . . . 28
13.6. Broadcom . . . . . . . . . . . . . . . . . . . . . . . . 28
13.7. ZTE Corporation . . . . . . . . . . . . . . . . . . . . 29
13.8. New H3C Technologies . . . . . . . . . . . . . . . . . . 29
13.9. Ruijie Network . . . . . . . . . . . . . . . . . . . . . 30
13.10. Open Source . . . . . . . . . . . . . . . . . . . . . . 30
13.11. Interoperability Report . . . . . . . . . . . . . . . . 30
14. Security Considerations . . . . . . . . . . . . . . . . . . . 32
15. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 32
15.1. SRv6 Endpoint Behaviors . . . . . . . . . . . . . . . . 32
16. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 35
17. References . . . . . . . . . . . . . . . . . . . . . . . . . 35
17.1. Normative References . . . . . . . . . . . . . . . . . . 35
17.2. Informative References . . . . . . . . . . . . . . . . . 36
Appendix A. Open Issues . . . . . . . . . . . . . . . . . . . . 39
Appendix B. Complete pseudocodes . . . . . . . . . . . . . . . . 40
B.1. End with NEXT-C-SID . . . . . . . . . . . . . . . . . . . 40
B.2. End with REPLACE-C-SID . . . . . . . . . . . . . . . . . 42
Contributors . . . . . . . . . . . . . . . . . . . . . . . . . . 44
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 45
1. Introduction
The Segment Routing (SR) architecture and SR for IPv6 (SRv6) are
defined in [RFC8402].
SRv6 Network Programming [RFC8986] defines a framework to build a
network program with topological and service segments (also referred
to by their segment identifier (SID)) carried in a Segment Routing
header (SRH) [RFC8754].
This document specifies new flavors to the SR endpoint behaviors
defined in Section 4 of [RFC8986]. These flavors enable a compressed
encoding of the SRv6 Segment-List in the SRH and therefore address
the requirements described in
[I-D.srcompdt-spring-compression-requirement].
The flavors defined in this document leverage the SRv6 data plane
defined in [RFC8754] and [RFC8986], and are compatible with the SRv6
control plane extensions for IS-IS [RFC9352], OSPF
[I-D.ietf-lsr-ospfv3-srv6-extensions], and BGP [RFC9252].
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2. Terminology
This document leverages the terms defined in [RFC8402], [RFC8754],
and [RFC8986]. The reader is assumed to be familiar with this
terminology.
This document introduces the following new terms:
* Locator-Block: The SRv6 SID block (IPv6 prefix allocated for SRv6
SIDs by the operator) of an SRv6 SID Locator, as defined in
Section 3.1 of [RFC8986].
* Locator-Node: The identifier of the parent node instantiating a
SID in an SRv6 SID Locator, as defined in Section 3.1 of
[RFC8986].
* Compressed-SID (C-SID): The Locator-Node and Function bits of a
SID that supports compressed encoding of SIDs.
* C-SID container: A 128-bit container holding a list of C-SIDs.
* C-SID sequence: A group of one or more consecutive C-SID
containers in a segment list.
* Uncompressed SID sequence: A group of one or more uncompressed
SIDs in a segment list.
* Compressed Segment List encoding: A segment list encoding that
reduces the packet header length thanks to one or more C-SID
sequences. A compressed Segment List encoding may contain any
number of uncompressed SID sequences.
2.1. Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in BCP
14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.
3. Basic Concepts
In an SRv6 domain, the SIDs are allocated from a particular IPv6
prefix: the Locator-Block. All SRv6 SIDs instantiated from the same
Locator-Block share the same most significant bits.
When the combined length of the SRv6 SID Locator, Function, and
Argument is smaller than 128 bits, the trailing bits are set to zero.
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When a sequence of consecutive SIDs in a Segment List shares a common
Locator-Block, a compressed Segment-List encoding can optimize the
packet header length by avoiding the repetition of the Locator-Block
and trailing bits with each individual SID.
The compressed Segment List encoding is fully compliant with the
specifications in [RFC8402], [RFC8754], and [RFC8986]. Efficient
encoding is achieved by combining a compressed Segment List encoding
logic on the SR policy headend with new flavors of the base SRv6
endpoint behaviors that decode this compressed encoding.
A Segment List can be encoded in the packet header using any
combination of compressed and uncompressed sequences. The C-SID
sequences leverage the flavors defined in this document, while the
uncompressed sequences use behaviors and flavors defined in other
documents, such as [RFC8986]. An SR Policy headend constructs and
compresses the SID-list depending on the capabilities of each SR
endpoint node that the packet should traverse, as well as its own
compression capabilities.
It is expected that compressed encoding flavors be available on
devices with limited packet manipulation capabilities, such as legacy
ASICs.
The compressed Segment List encoding supports any Locator-Block
allocation. While other options are supported and may provide higher
efficiency, each routing domain can be allocated a /48 prefix from a
global IPv6 block (see Section 6.2).
4. SR Endpoint Flavors
This section defines several options to achieve compressed Segment
List encoding in the form of two new flavors for the End, End.X,
End.T, End.B6.Encaps, End.B6.Encaps.Red, and End.BM behaviors of
[RFC8986]. These flavors could also be combined with behaviors
defined in other documents.
The compressed encoding can be achieved by leveraging any of these SR
endpoint flavors. The NEXT-C-SID flavor and the REPLACE-C-SID flavor
expose the same high-level behavior in their use of the SID argument
to determine the next segment to be processed, but they have
different low-level characteristics that can make one more or less
efficient than the other for a particular SRv6 deployment.
It is RECOMMENDED, for ease of operation, that a single compressed
encoding flavor be used in a given SRv6 domain. However, in a multi-
domain deployment, different flavors can be used in different
domains.
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Both flavors leverage the following variables:
* Variable LBL is the Locator-Block length of the SID.
* Variable LNFL is the sum of the Locator-Node and the Function
lengths of the SID. It is also referred to as C-SID length.
* Variable AL is the Argument length of the SID.
4.1. NEXT-C-SID Flavor
A SID instantiated with the NEXT-C-SID flavor takes an argument that
carries the remaining C-SIDs in the current C-SID container.
The length AL of the argument is equal to 128-LBL-LNFL.
An SR segment endpoint node instantiating a SID with the NEXT-C-SID
flavor MUST accept any argument value for that SID.
+------------------------------------------------------------------+
| Locator-Block |Loc-Node| Argument |
| |Function| |
+------------------------------------------------------------------+
<-------- LBL ---------> < LNFL > <------------- AL ------------->
Figure 1: Example of a NEXT-C-SID flavored SID structure using a
48-bit Locator-Block, 16-bit combined locator and function, and
64-bit argument
4.1.1. End with NEXT-C-SID
When processing an IPv6 packet that matches a FIB entry locally
instantiated as an End SID with the NEXT-C-SID flavor, the procedure
described in Section 4.1 of [RFC8986] is executed with the following
modifications.
The below pseudocode is inserted between lines S01 and S02 of the SRH
processing in Section 4.1 of [RFC8986], and a second time before line
S01 of the upper-layer header processing in Section 4.1.1 of
[RFC8986], or prior to processing any extension header other than
Hop-by-Hop or Destination Option.
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S01. If (DA.Argument != 0) {
S02. If (IPv6 Hop Limit <= 1) {
S03. Send an ICMP Time Exceeded message to the Source Address,
Code 0 (Hop limit exceeded in transit),
interrupt packet processing and discard the packet.
S04. }
S05. Copy the value of DA.Argument into the bits [LBL..(LBL+AL-1)]
of the Destination Address.
S06. Set the bits [(LBL+AL)..127] of the Destination Address to
zero.
S07. Decrement Hop Limit by 1.
S08. Submit the packet to the egress IPv6 FIB lookup for
transmission to the next destination.
S09. }
Notes:
* DA.Argument identifies the bits [(LBL+LNFL)..127] in the
Destination Address of the IPv6 header.
* The value in the Segments Left field of the SRH is not modified
when DA.Argument in the received packet has a non-zero value.
A rendering of the complete pseudocode is provided in Appendix B.1.
4.1.2. End.X with NEXT-C-SID
When processing an IPv6 packet that matches a FIB entry locally
instantiated as an End.X SID with the NEXT-C-SID flavor, the
procedure described in Section 4.2 of [RFC8986] is executed with the
following modifications.
The pseudocode in Section 4.1.1 of this document is modified by
replacing line S08 as shown below.
S08. Submit the packet to the IPv6 module for transmission to the
new destination via a member of J.
The resulting pseudocode is inserted between lines S01 and S02 of the
SRH processing in Section 4.2 of [RFC8986], and a second time before
line S01 of the upper-layer header processing in Section 4.1.1 of
[RFC8986], or prior to processing any extension header other than
Hop-by-Hop or Destination Option.
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4.1.3. End.T with NEXT-C-SID
When processing an IPv6 packet that matches a FIB entry locally
instantiated as an End.T SID with the NEXT-C-SID flavor, the
procedure described in Section 4.3 of [RFC8986] is executed with the
following modifications.
The pseudocode in Section 4.1.1 of this document is modified by
replacing line S08 as shown below.
S08.1. Set the packet's associated FIB table to T.
S08.2. Submit the packet to the egress IPv6 FIB lookup for
transmission to the new destination.
The resulting pseudocode is inserted between lines S01 and S02 of the
SRH processing in Section 4.3 of [RFC8986], and a second time before
line S01 of the upper-layer header processing in Section 4.1.1 of
[RFC8986], or prior to processing any extension header other than
Hop-by-Hop or Destination Option.
4.1.4. End.B6.Encaps with NEXT-C-SID
When processing an IPv6 packet that matches a FIB entry locally
instantiated as an End.B6.Encaps SID with the NEXT-C-SID flavor, the
procedure described in Section 4.13 of [RFC8986] is executed with the
following modifications.
The pseudocode in Section 4.1.1 of this document is modified by
replacing line S08 as shown below.
S08.1. Push a new IPv6 header with its own SRH containing B.
S08.2. Set the outer IPv6 SA to A.
S08.3. Set the outer IPv6 DA to the first SID of B.
S08.4. Set the outer Payload Length, Traffic Class, Flow Label,
Hop Limit, and Next Header fields.
S08.5. Submit the packet to the egress IPv6 FIB lookup for
transmission to the next destination.
The resulting pseudocode is inserted between lines S01 and S02 of the
SRH processing in Section 4.13 of [RFC8986], and a second time before
line S01 of the upper-layer header processing in Section 4.1.1 of
[RFC8986], or prior to processing any extension header other than
Hop-by-Hop or Destination Option.
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4.1.5. End.B6.Encaps.Red with NEXT-C-SID
When processing an IPv6 packet that matches a FIB entry locally
instantiated as an End.B6.Encaps.Red SID with the NEXT-C-SID flavor,
the procedure described in Section 4.14 of [RFC8986] is executed with
the same modifications as in Section 4.1.4 of this document.
4.1.6. End.BM with NEXT-C-SID
When processing an IPv6 packet that matches a FIB entry locally
instantiated as an End.BM SID with the NEXT-C-SID flavor, the
procedure described in Section 4.15 of [RFC8986] is executed with the
following modifications.
The pseudocode in Section 4.1.1 of this document is modified by
replacing line S08 as shown below.
S08.1. Push the MPLS label stack for B.
S08.2. Submit the packet to the MPLS engine for transmission.
The resulting pseudocode is inserted between lines S01 and S02 of the
SRH processing in Section 4.15 of [RFC8986], and a second time before
line S01 of the upper-layer header processing in Section 4.1.1 of
[RFC8986], or prior to processing any extension header other than
Hop-by-Hop or Destination Option.
4.1.7. Combination with PSP, USP and USD flavors
PSP: The PSP flavor defined in Section 4.16.1 of [RFC8986] is
unchanged when combined with the NEXT-C-SID flavor.
USP: The USP flavor defined in Section 4.16.2 of [RFC8986] is
unchanged when combined with the NEXT-C-SID flavor.
USD: The USD flavor is unchanged when combined with the NEXT-C-SID
flavor. The pseudocodes defined in Section 4.1.1, Section 4.1.2, and
Section 4.1.3 of this document are inserted at the beginning of the
modified upper-layer header processing defined in Section 4.16.3 of
[RFC8986] for End, End.X, and End.T, respectively.
4.2. REPLACE-C-SID Flavor
A SID instantiated with the REPLACE-C-SID flavor takes an argument
that indicates the index of the next C-SID in the appropriate C-SID
container.
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The length AL of the argument is equal to 128-LBL-LNFL. The index
value is encoded in the least significant ceil(log_2(128/LNFL)) bits
of the argument field.
+-------------------------------------------------------------------+
| Locator-Block | Locator-Node | Argument |
| | + Function | |
+-------------------------------------------------------------------+
<-------- LBL ---------> <---- LNFL ----> <--------- AL ---------->
Figure 2: Example of a REPLACE-C-SID flavored SID structure using
a 48-bit Locator-Block, 32-bit combined locator and function, and
48-bit argument
4.2.1. End with REPLACE-C-SID
When processing an IPv6 packet that matches a FIB entry locally
instantiated as an End SID with the REPLACE-C-SID flavor, the SRH
processing described in Section 4.1 of [RFC8986] is executed with the
following modifications.
Line S02 of SRH processing in Section 4.1 of [RFC8986] is replaced as
follows.
S02. If (Segments Left == 0 and (DA.Arg.Index == 0 or
Segment List[0][DA.Arg.Index-1] == 0)) {
Lines S09 to S16 are replaced by the following pseudo code.
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S09. If (DA.Arg.Index != 0) {
S10. If ((Last Entry > max_LE) or (Segments Left > Last Entry)) {
S11. Send an ICMP Parameter Problem to the Source Address,
Code 0 (Erroneous header field encountered),
Pointer set to the Segments Left field,
interrupt packet processing and discard the packet.
S12. }
S13. Decrement DA.Arg.Index by 1.
S14. If (Segment List[Segments Left][DA.Arg.Index] == 0) {
S15. Decrement Segments Left by 1.
S16. Decrement IPv6 Hop Limit by 1.
S17. Update IPv6 DA with Segment List[Segments Left]
S18. Submit the packet to the egress IPv6 FIB lookup for
transmission to the new destination.
S19. }
S20. } Else {
S21. If((Last Entry > max_LE) or (Segments Left > Last Entry+1)){
S22. Send an ICMP Parameter Problem to the Source Address,
Code 0 (Erroneous header field encountered),
Pointer set to the Segments Left field,
interrupt packet processing and discard the packet.
S23. }
S24. Decrement Segments Left by 1.
S25. Set DA.Arg.Index to (128/NF - 1).
S26. }
S27. Decrement IPv6 Hop Limit by 1.
S28. Write Segment List[Segments Left][DA.Arg.Index] into the bits
[B..B+NF-1] of the Destination Address of the IPv6 header.
S29. Submit the packet to the egress IPv6 FIB lookup for
transmission to the new destination.
S30. }
Notes:
* DA.Arg.Index identifies the bits [(128-ceil(log_2(128/
LNFL)))..127] in the Destination Address of the IPv6 header.
* Segment List[Segments Left][DA.Arg.Index] identifies the bits
[DA.Arg.Index*LNFL..(DA.Arg.Index+1)*LNFL-1] in the SRH Segment
List entry at index Segments Left.
The upper-layer header processing described in Section 4.1.1 of
[RFC8986] is unchanged.
A rendering of the complete pseudocode is provided in Appendix B.2.
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4.2.2. End.X with REPLACE-C-SID
When processing an IPv6 packet that matches a FIB entry locally
instantiated as an End.X SID with the REPLACE-C-SID flavor, the
procedure described in Section 4.2 of [RFC8986] is executed with the
following modifications.
The pseudocode in Section 4.2.1 of this document is modified by
replacing line S18 and S29 as shown below.
S01. Submit the packet to the IPv6 module for transmission to the
new destination via a member of J.
The SRH processing in Section 4.2 of [RFC8986] is replaced with the
resulting pseudocode. The upper-layer header processing is
unchanged.
4.2.3. End.T with REPLACE-C-SID
When processing an IPv6 packet that matches a FIB entry locally
instantiated as an End.T SID with the REPLACE-C-SID flavor, the
procedure described in Section 4.3 of [RFC8986] is executed with the
following modifications.
The pseudocode in Section 4.2.1 of this document is modified by
replacing line S18 and S29 as shown below.
S01. Set the packet's associated FIB table to T.
S02. Submit the packet to the egress IPv6 FIB lookup for
transmission to the new destination.
The SRH processing in Section 4.3 of [RFC8986] is replaced with the
resulting pseudocode. The upper-layer header processing is
unchanged.
4.2.4. End.B6.Encaps with REPLACE-C-SID
When processing an IPv6 packet that matches a FIB entry locally
instantiated as an End.B6.Encaps SID with the REPLACE-C-SID flavor,
the procedure described in Section 4.13 of [RFC8986] is executed with
the following modifications.
The pseudocode in Section 4.2.1 of this document is modified by
replacing line S18 and S29 as shown below.
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S01. Push a new IPv6 header with its own SRH containing B.
S02. Set the outer IPv6 SA to A.
S03. Set the outer IPv6 DA to the first SID of B.
S04. Set the outer Payload Length, Traffic Class, Flow Label,
Hop Limit, and Next Header fields.
S05. Submit the packet to the egress IPv6 FIB lookup for
transmission to the next destination.
The SRH processing in Section 4.13 of [RFC8986] is replaced with the
resulting pseudocode. The upper-layer header processing is
unchanged.
4.2.5. End.B6.Encaps.Red with REPLACE-C-SID
When processing an IPv6 packet that matches a FIB entry locally
instantiated as an End.B6.Encaps.Red SID with the REPLACE-C-SID
flavor, the procedure described in Section 4.14 of [RFC8986] is
executed with the same modifications as in Section 4.2.4 of this
document.
4.2.6. End.BM with REPLACE-C-SID
When processing an IPv6 packet that matches a FIB entry locally
instantiated as an End.BM SID with the REPLACE-C-SID flavor, the
procedure described in Section 4.15 of [RFC8986] is executed with the
following modifications.
The pseudocode in Section 4.2.1 of this document is modified by
replacing line S18 and S29 as shown below.
S01. Push the MPLS label stack for B.
S02. Submit the packet to the MPLS engine for transmission.
The SRH processing in Section 4.15 of [RFC8986] is replaced with the
resulting pseudocode. The upper-layer header processing is
unchanged.
4.2.7. End.DX and End.DT with REPLACE-C-SID
New behaviors of End.DX6, End.DX4, End.DT6, End.DT4, End.DT46,
End.DX2, End.DX2V, End.DX2U, or End.DX2M [RFC8986] with REPLACE-C-SID
flavor are also defined in this draft. These new behaviors can be
used to indicate the capability of compression of Node and SID, which
are requried in path computation and compressed SID list encoding.
As per Section 6.4, when allocating a C-SID value from a Local
Identifiers Block (LIB), an extra prefix of
Locator_block:FunctionID::/LBL+FL is required on the Segment Endpoint
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node to support LIB matching in forwarding. The new behaviors with
REPLACE-C-SID flavor explicitly require the node to do so in SID
initiation.
When processing an IPv6 packet that matches a FIB entry locally
instantiated as an End.DX6, End.DX4, End.DT6, End.DT4, End.DT46,
End.DX2, End.DX2V, End.DT2U or End.DT2M SID with the REPLACE-C-SID
flavor, the procedures described in [RFC8986] are executed. For
End.DT2M with REPLACE-C-SID flavor, the Arg.FE2 is a 16-bit value
located in the least significant [(128-ceil(log_2(128/
LNFL)))-16..(128-ceil(log_2(128/LNFL)))-1] bits of the argument.
4.2.8. Combination with PSP, USP, and USD flavors
PSP: When combined with the REPLACE-C-SID flavor, the additional PSP
flavor instructions defined in Section 4.16.1.2 of [RFC8986] are
inserted after line S17 and S28 of the pseudocode in Section 4.2.1,
and the first line of the inserted instructions after S28 is modified
as follows.
S28.1. If (Segments Left == 0 and (DA.Arg.Index == 0 or
Segment List[0][DA.Arg.Index-1] == 0)) {
Note:
* Segment List[Segments Left][DA.Arg.Index-1] identifies the bits
[(DA.Arg.Index-1)*LNFL..DA.Arg.Index*LNFL-1] in the SRH Segment
List entry at index Segments Left.
USP: When combined with the REPLACE-C-SID flavor, the line S03 of the
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].
Note that S03 is shown in the complete pseudocode in Appendix B.2.
USD: The USD flavor defined in Section 4.16.3 of [RFC8986] is
unchanged when combined with the REPLACE-C-SID flavor.
5. C-SID Allocation
The C-SID value of 0 is RESERVED. It is used to indicate the end of
a C-SID container.
In order to efficiently manage the C-SID numbering space, it may be
beneficial to divide it into two non-overlapping sub-spaces: a Global
Identifiers Block (GIB) and a Local Identifiers Block (LIB).
* The GIB is the pool of C-SID values available for global
allocation.
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* The LIB is the pool of C-SID values available for local
allocation.
The concept of LIB is applicable to SRv6 and specifically to its
NEXT-C-SID and REPLACE-C-SID flavors. The shorter the C-SID, the
more benefit the LIB brings.
The opportunity to use these sup-spaces, their size, and their C-SID
allocation policy depends on the C-SID length relative to the size of
the network (e.g., number of nodes, links, service routes). Some
guidelines for a typical deployment scenario are provided in
Section 6.3.
5.1. Global C-SID
A C-SID from the GIB.
A Global C-SID typically identifies a shortest path to a node in the
SRv6 domain. An IP route is advertised by the parent node to each of
its global C-SIDs, under the associated Locator-Block. The parent
node executes a variant of the End behavior.
A node can have multiple global C-SIDs under the same Locator-Block
(e.g., one per IGP flexible algorithm). Multiple nodes may share the
same global C-SID (anycast).
5.2. Local C-SID
A C-SID from the LIB.
A local C-SID may identify a cross-connect to a direct neighbor over
a specific interface or a VPN context.
No IP route is advertised by a parent node for its local C-SIDs.
If N1 and N2 are two different physical nodes of the SRv6 domain and
I is a local C-SID value, then N1 and N2 may bind two different
behaviors to I.
6. C-SID and Locator-Block Length
6.1. C-SID Length
The NEXT-C-SID flavor supports both 16- and 32-bit C-SID lengths. A
C-SID length of 16-bit is RECOMMENDED.
The REPLACE-C-SID flavor supports both 16- and 32-bit C-SID lengths.
A C-SID length of 32-bit is RECOMMENDED.
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6.2. Locator-Block Length
The RECOMMENDED Locator-Block sizes for the NEXT-C-SID flavor are 16,
32, or 48 bits. The smaller the block, the higher the compression
efficiency.
The RECOMMENDED Locator-Block size for the REPLACE-C-SID flavor can
be 48, 56, 64, 72, or 80 bits, depending on the needs of the
operator.
6.3. GIB/LIB Usage
GIB and LIB usage is a local implementation and/or configuration
decision, however, some guidelines for determining usage for specific
SID behaviors and recommendations are provided.
The GIB number space is shared among all segment endpoint nodes using
SRv6 locators under a Block space. The more SIDs assigned from this
space, per node, the faster it is exhausted. Therefore its use is
prioritized for SIDs that identify a node, like End behavior SIDs.
The LIB number space is unique per node. Each node is able to fully
utilize the entire LIB number space without consideration of
assignments at other nodes. Therefore its use is prioritized for
SIDs that identify services (of which there may be many) at nodes,
like cross-connects, adjacencies, etc.
While a longer C-SID length permits more flexibility in which SID
behaviors may be assigned from the GIB, it also reduces compression.
Given the previous Locator-Block and C-SID length recommendations,
the following GIB/LIB usage is RECOMMENDED:
* NEXT-C-SID:
- GIB: End
- LIB: End.X, End.T, End.DT4/6/46/2U/2M, End.DX4/6/2/2V
(including large-scale pseudowire), End.B6.Encaps,
End.B6.Encaps.Red, End.BM
* REPLACE-C-SID:
- GIB: End, End.X, End.T, End.DT4/6/46/2U/2M, End.DX4/6/2/2V,
End.B6.Encaps, End.B6.Encaps.Red, End.BM
- LIB: End.DX2/2V for large-scale pseudowire
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6.4. Recommended Installation of C-SIDs in FIB
An SR segment endpoint node instantiating a NEXT-C-SID or REPLACE-
C-SID flavored SID should install the corresponding FIB entry to
match only the locator and function parts of the SID (i.e., with a
prefix length of LBL + LNL + FL).
In addition, an SR segment endpoint node instantiating NEXT-C-SID
flavored SIDs from both GIB and LIB may install combined "Global +
Local" FIB entries to match a sequence of global and local C-SIDs in
a single LPM lookup.
For example, let us consider an SR segment endpoint node 10
instantiating the following two NEXT-C-SID flavored SIDs according to
the C-SID length, Locator-Block length, and GIB/LIB recommendations
in this section.
* 2001:db8:b1:10:: from GIB with Locator-Block length (LBL) = 48,
Locator-Node length (LNL) = 16, Function length (FL) = 0, Argument
length (AL) = 64, and bound to the End behavior with the NEXT-
C-SID flavor.
* 2001:db8:b1:f123:: from LIB with Locator-Block length (LBL) = 48,
Locator-Node length (LNL) = 0, Function length (FL) = 16, Argument
length (AL) = 64, and bound to the End.X behavior for its local
IGP adjacency 123 with the NEXT-C-SID flavor.
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-C-SID flavor.
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
NEXT-C-SID flavor.
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
the NEXT-C-SID flavor.
As another example, let us consider an SR segment endpoint node 20
instantiating the following two REPLACE-C-SID flavored SIDs according
to the C-SID length, Locator-Block length, and GIB/LIB
recommendations in this section.
* 2001:db8:b2:20:1:: from GIB with Locator-Block length (LBL) = 48,
Locator-Node length (LNL) = 16, Function length (FL) = 16,
Argument length (AL) = 48, and bound to the End behavior with the
REPLACE-C-SID flavor.
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* 2001:db8:b2:20:123:: from GIB with Locator-Block length (LBL) =
48, Locator-Node length (LNL) = 16, Function length (FL) = 16,
Argument length (AL) = 48, and bound to the End.X behavior for its
local IGP adjacency 123 with the REPLACE-C-SID flavor.
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-C-SID
flavor.
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
the REPLACE-C-SID flavor.
7. SR Source Node
An SR source node MAY compress a segment list when it includes NEXT-
C-SID or REPLACE-C-SID flavor SIDs.
If an SR source node chooses to compress the segment list, one method
is described below for illustrative purposes. Any other method,
resulting in a path equivalent to the original segment list, is
compliant.
For a series of NEXT-C-SID flavor SIDs in the uncompressed segment
list, an SR source node compresses an uncompressed segment list to a
compressed segment list as follows.
1. Initialize a C-SID container as the first segment in the
uncompressed segment list, with all argument bits set to 0, and
the remaining capacity to AL
2. For each subsequent segment in the uncompressed segment list
1. If the current segment Locator-Block matches that of the
C-SID container and the current segment LNFL is lower than or
equal to the remaining capacity
1. Copy the current segment Locator-Node and Function to the
most significant remaining argument bits of the C-SID
container, and decrement the remaining capacity by LNFL
2. Else
1. Push the C-SID container onto the compressed segment list
2. Initialize a C-SID container as the current segment in
the uncompressed segment list, with all argument bits set
to 0, and the remaining capacity to AL
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3. Push the C-SID container onto the compressed segment list
For a series of REPLACE-C-SID flavor SIDs in the uncompressed segment
list, the first segment is not compressed. The SR source then
initializes an empty C-SID container with all bits set to 0 and
inserts consecutive C-SIDs from the uncompressed segment list into
the container. When the container is full, it is pushed on the
compressed segment list and a new container is initialized.
Regardless of how an SR Policy compressed SID list is produced, it is
encoded in the IPv6 header and optional SRH as described in
Section 4.1 and 4.1.1 of [RFC8754]. The text is reproduced below for
reference.
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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 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 omitted.
When needed, the SRH is created as follows:
The Next Header and Hdr Ext Len fields are set as specified in
[RFC8200].
The Routing Type field is set to 4.
The DA of the packet is set with the value of the first segment.
The first element of the SRH Segment List is the ultimate segment.
The second element is the penultimate segment, and so on.
The Segments Left field is set to n-1, where n is the number of
elements in the SR Policy.
The Last Entry field is set to n-1, where n is the number of
elements in the SR Policy.
TLVs (including HMAC) may be set according to their specification.
The packet is forwarded toward the packet's Destination Address
(the first segment).
When a source does not require the entire SID list to be preserved
in the SRH, a reduced SRH may be used.
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
header), and the Last Entry field is set to n-2, where n is the
number of elements in the SR Policy.
7.1. Rules for NEXT-C-SID flavor uncompressed SID lists
1. If a Destination Option header would follow an SRH with a segment
list of more than one segment compressed as a single NEXT-C-SID
container, the SR source MUST NOT omit the SRH.
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2. When the Segment List entry in the SRH is a C-SID container
representing more than one segment, the PSP operation is
performed at the segment preceding this C-SID container in the
segment list. If the PSP behavior should instead be performed at
the penultimate segment along the path, the SR source MUST NOT
compress the ultimate segment of the segment list into a C-SID
container.
3. If a Destination Option header would follow an SRH with a last
Segment List entry being a NEXT-C-SID container representing more
than one segment, the SR source node MUST ensure that the PSP
operation is not performed before the penultimate segment
endpoint node along the path.
7.2. Rules for REPLACE-C-SID flavor uncompressed SID lists
1. All REPLACE-C-SID flavor SIDs in a series MUST share the same
Locator-Block length (LBL) and the same combined Locator-Node and
Function length (LNFL). An uncompressed SID list may contain any
number of such series.
2. A series of REPLACE-C-SID flavor SIDs MUST contain at least two
elements.
3. End of a C-SID sequence can be indicated by:
* a SID without REPLACE-C-SID flavor (e.g., End, End.X or NEXT-
C-SID flavor End, End.X SID) regardless of the index of the
C-SID in the container. The SID MUST have the same Locator-
Block and LNFL length as the preceding REPLACE-C-SID flavor
SID.
* a SID with REPLACE-C-SID flavor when the index of the C-SID is
greater than 0.
The length of a C-SID is determined by its behavior and LNFL.
8. Inter Routing Domains with the End.XPS behavior
The End.XPS behavior described in this section is OPTIONAL.
Some SRv6 traffic may need to cross multiple routing domains, such as
different Autonomous Systems (ASes) or different routing areas.
Different routing domains may use different addressing schema and
Locator-Blocks.
This section defines an optional solution and SID behavior allowing
for the use of different Locator-Blocks between routing domains.
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The solution requires a new SID behavior, called "Endpoint with
cross-connect to an array of layer-3 adjacencies and SRv6 Prefix
Swap" (End.XPS for short) allowing for this transition of Locator-
Block between two routing domains.
End.XPS is a variant of End.X, performing both "End.X Layer-3 Cross-
Connect" and the translation of the Locator-Block between the two
routing domains.
The processing takes as an additional parameter the prefix B2/m
corresponding the Locator-Block in the second domain. This parameter
is a property of the (received) SID and is given as a result of the
lookup on the IPv6 destination address which identifies the SRv6 SID
and its properties.
The End.XPS behavior is compatible with the NEXT-C-SID and REPLACE-
C-SID flavors described in this document.
When a router R receives a packet whose IPv6 DA matches a local
End.XPS SID with the NEXT-C-SID flavor, that is associated with a set
J of one or more Layer-3 adjacencies and the Locator-Block B2/m of
the neighbor routing domain, R processes the packet as follows.
1. If (DA.Argument != 0) {
2. Write B2 into the most significant bits of the Destination
Address of the IPv6 header.
3. Write DA.Argument into the bits [m..(m+AL-1)] of the
Destination Address of the IPv6 header.
4. Set the bits [(m+AL)..127] of the Destination Address
of the IPv6 header to zero.
5. } Else {
6. Decrement Segments Left by 1.
7. Copy Segment List[Segments Left] from the SRH to the
Destination Address of the IPv6 header.
8. }
9. Submit the packet to the IPv6 module for transmission to the
new destination via a member of J.
When a router R receives a packet whose IPv6 DA matches a local
End.XPS SID with the REPLACE-C-SID flavor, that is associated with a
set J of one or more Layer-3 adjacencies and the Locator-Block B2/m
of the neighbor routing domain, R processes the packet as follows.
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1. If (DA.Arg.Index != 0) {
2. Decrement DA.Arg.Index by 1.
3. } Else {
4. Decrement Segments Left by 1.
5. Set DA.Arg.Index to (128/LNFL - 1).
6. }
7. Write B2 into the most significant bits of the Destination
Address of the IPv6 header.
8. Write Segment List[Segments Left][DA.Arg.Index] into the bits
[m..m+LNFL-1] of the Destination Address of the IPv6 header.
9. Write DA.Arg.Index into the bits [m+LNFL..m+LNFL+AL-1] of the
Destination Address of the IPv6 header.
10. Set the bits [(m+LNFL+AL)..127] of the Destination Address
of the IPv6 header to zero.
11. Submit the packet to the IPv6 module for transmission to the
new destination via a member of J.
Note: the way the Locator-Block B2 of the next routing domain is
known is out of scope of this document. As examples, it could be
learnt via configuration, or using a signaling protocol either with
the peer domain or with a central controller (e.g. Path Computation
Element (PCE)).
When End.XPS SID behavior is used, the restriction on the C-SID
length for the REPLACE-C-SID flavor is relaxed and becomes: all SID
the are part of a C-SID sequence *within a domain* MUST have the same
C-SID length LNFL.
9. Control Plane
This document does not require any new extensions to routing
protocols.
Section 8 of [RFC8986] provides an overview of the control plane
protocols used for signaling of the SRv6 SIDs introduced by that
document. The SRv6 SIDs introduced by this document are advertised
using the same SRv6 extensions for various routing protocols, such as
* IS-IS [RFC9352]
* OSPFv3 [I-D.ietf-lsr-ospfv3-srv6-extensions]
* BGP [RFC9252], [I-D.ietf-idr-bgpls-srv6-ext],
[I-D.ietf-idr-segment-routing-te-policy],
[I-D.ietf-idr-bgp-ls-sr-policy]
* PCEP [I-D.ietf-pce-segment-routing-ipv6]
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Signaling the SRv6 SID Structure is REQUIRED for all the SIDs
introduced in this document. It is used by an SR source node to
compress a segment list as described in Section 7.
For a segment list computed by a controller and signaled to an SR
source node (e.g., via BGP [I-D.ietf-idr-segment-routing-te-policy]
or PCEP [I-D.ietf-pce-segment-routing-ipv6]), the controller provides
the ordered segment list comprising the individual SIDs (i.e.,
without any compression) to the SR source node. The SR source node
may then compress the segment list as described in Section 7.
10. Operational Considerations
10.1. Ping a SID without a Segment List
An SR source node may ping a routable SRv6 SID by sending an ICMPv6
echo request packet destined to the SRv6 SID, as illustrated in
Appendix A.1.2 of [RFC9259].
When the SRv6 SID in the destination address of the ICMPv6 echo
request is one of the SID flavors defined in this document, the SR
source node MUST set the arguments of the SID to 0.
10.2. Ping a SID via a Segment List
An SR source node may ping a routable or non-routable SRv6 SID via a
segment list as illustrated in Appendix A.1.2 of [RFC9259].
Regardless of the behavior of the SIDs in the SID list, the SR source
node computes the ICMP echo request checksum using the ultimate
segment in the segment list, i.e., the IPv6 destination address as it
is expected to appear at the ultimate destination of the packet.
10.3. ICMP Error Processing
When an IPv6 node encounters an error while processing a packet, it
may report that error by sending an IPv6 error message to the packet
source with an enclosed copy of the invoking packet. For the source
of an invoking packet to process the ICMP error message, the ultimate
destination address of the IPv6 header may be required.
Section 5.4 of [RFC8754] defines the logic that an SR source node
should follow to determine the ultimate destination of an invoking
packet containing an SRH.
For an SR source node that supports the compressed segment list
encoding defined in this document, the logic to determine the
ultimate destination is generalized as follows.
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* If the destination address of the invoking IPv6 packet matches a
known SRv6 SID, modify the invoking IPv6 packet by applying the
SID behavior associated with the matched SRv6 SID;
* Repeat until the application of the SID behavior would result in
the processing of the upper-layer header.
The destination address of the resulting IPv6 packet may be used as
the ultimate destination of the invoking IPv6 packet.
Since the SR source node that needs to determine the ultimate
destination is the same node that originally built the segment list
in the invoking packet, it is able to perform this operation for all
the SIDs in the packet.
11. Illustrations
Illustrations for the functionalities defined in this document are
provided in [I-D.clad-spring-srv6-srh-compression-illus].
12. Deployment Model
Section 5 of [RFC8754] defines the intra-SR-domain deployment model
and associated security procedures.
The same deployment model applies to the SIDs defined in this
document.
13. Implementation Status
This section is to be removed before publishing as an RFC.
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
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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]).
13.1. Cisco Systems
Cisco Systems reported the following implementations of the SR
endpoint node NEXT-C-SID flavor (Section 4.1) and the SR source node
efficient SID-list encoding (Section 7) for NEXT-C-SID flavored 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-C-SID flavor.
This report was last updated on January 11, 2023.
13.2. Huawei Technologies
Huawei Technologies reported the following implementations of the SR
endpoint node REPLACE-C-SID flavor (Section 4.2) for REPLACE-C-SID
flavored SIDs. These are used as part of its SRv6 TI-LFA, micro-loop
avoidance, and traffic engineering functionalities.
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* 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-C-SID flavor.
This report was last updated on January 11, 2023.
13.3. Nokia
Nokia reported the following implementations ([IMPL-NOKIA-20.10]) of
the SR endpoint node NEXT-C-SID flavor (Section 4.1) for NEXT-C-SID
flavored SIDs. 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-C-SID flavor.
This report was last updated on February 3, 2023.
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13.4. Arrcus
Arrcus reported the following implementations of the SR endpoint node
NEXT-C-SID flavor (Section 4.1) for NEXT-C-SID flavoured SIDs. 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-C-SID flavor.
This report was last updated on March 11, 2023.
13.5. Marvell
Marvell reported support in the Marvell Prestera Packet Processor for
the SR endpoint node NEXT-C-SID flavor (Section 4.1) for NEXT-C-SID
flavored SIDs and SR endpoint node REPLACE-C-SID flavor (Section 4.2)
for REPLACE-C-SID flavored SIDs.
This report was last updated on February 15, 2023.
13.6. Broadcom
Broadcom reported the following implementations of the SR endpoint
node NEXT-C-SID flavor (Section 4.1) for NEXT-C-SID flavored SIDs and
SR endpoint node REPLACE-C-SID flavor (Section 4.2) for REPLACE-C-SID
flavored SIDs. 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
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* 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-C-SID and REPLACE-C-SID flavors.
For 78900 (Tomahawk) series-related support, please contact the
Broadcom team.
This report was last updated on February 21, 2023.
13.7. ZTE Corporation
ZTE Corporation reported the following implementations of the SR
endpoint node REPLACE-C-SID flavor (Section 4.2) for REPLACE-C-SID
flavored SIDs. 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.
13.8. New H3C Technologies
New H3C Technologies reported the following implementations of the SR
endpoint node REPLACE-C-SID flavor (Section 4.2) for REPLACE-C-SID
flavored SIDs. 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.
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13.9. Ruijie Network
Ruijie Network reported the following implementations of the SR
endpoint node REPLACE-C-SID flavor (Section 4.2) for REPLACE-C-SID
flavored SIDs. 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.
13.10. Open Source
The authors found the following open source implementations of the SR
endpoint node NEXT-C-SID 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
endpoint node REPLACE-C-SID 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.
13.11. Interoperability Report
In November 2020, China Mobile successfully validated multiple
interoperable implementations of the NEXT-C-SID and REPLACE-C-SID
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
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* 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-C-SID flavor, and End behavior with REPLACE-C-SID
flavor. The variant being used at each segment endpoint 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-
C-SID flavor
* S3 is associated with the regular End behavior (no flavor)
* S4, S5, and S6 are associated with the End behavior with the NEXT-
C-SID flavor
* The SR source node imposes a compressed segment list encoding of 3
SIDs.
*Scenario 2:*
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* S1, S2..., S6 are associated with the End behavior with the NEXT-
C-SID 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-C-SID flavor
* The SR source node imposes a compressed segment list encoding of 3
SIDs.
14. Security Considerations
The security requirements and mechanisms described in [RFC8402] and
[RFC8754] also apply to this document.
This document does not introduce any new security considerations.
15. IANA Considerations
15.1. SRv6 Endpoint Behaviors
This I-D. requests IANA to make the following registrations from the
"SRv6 Endpoint Behaviors" sub-registry under the top-level "Segment
Routing" registry (https://www.iana.org/assignments/segment-
routing/):
+=======+=========================================+===========+
| Value | Description | Reference |
+=======+=========================================+===========+
| 43 | End with NEXT-CSID | This I-D. |
+-------+-----------------------------------------+-----------+
| 44 | End with NEXT-CSID & PSP | This I-D. |
+-------+-----------------------------------------+-----------+
| 45 | End with NEXT-CSID & USP | This I-D. |
+-------+-----------------------------------------+-----------+
| 46 | End with NEXT-CSID, PSP & USP | This I-D. |
+-------+-----------------------------------------+-----------+
| 47 | End with NEXT-CSID & USD | This I-D. |
+-------+-----------------------------------------+-----------+
| 48 | End with NEXT-CSID, PSP & USD | This I-D. |
+-------+-----------------------------------------+-----------+
| 49 | End with NEXT-CSID, USP & USD | This I-D. |
+-------+-----------------------------------------+-----------+
| 50 | End with NEXT-CSID, PSP, USP & USD | This I-D. |
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+-------+-----------------------------------------+-----------+
| 52 | End.X with NEXT-CSID | This I-D. |
+-------+-----------------------------------------+-----------+
| 53 | End.X with NEXT-CSID & PSP | This I-D. |
+-------+-----------------------------------------+-----------+
| 54 | End.X with NEXT-CSID & USP | This I-D. |
+-------+-----------------------------------------+-----------+
| 55 | End.X with NEXT-CSID, PSP & USP | This I-D. |
+-------+-----------------------------------------+-----------+
| 56 | End.X with NEXT-CSID & USD | This I-D. |
+-------+-----------------------------------------+-----------+
| 57 | End.X with NEXT-CSID, PSP & USD | This I-D. |
+-------+-----------------------------------------+-----------+
| 58 | End.X with NEXT-CSID, USP & USD | This I-D. |
+-------+-----------------------------------------+-----------+
| 59 | End.X with NEXT-CSID, PSP, USP & USD | This I-D. |
+-------+-----------------------------------------+-----------+
| TBA | End.T with NEXT-CSID | This I-D. |
+-------+-----------------------------------------+-----------+
| TBA | End.T with NEXT-CSID & PSP | This I-D. |
+-------+-----------------------------------------+-----------+
| TBA | End.T with NEXT-CSID & USP | This I-D. |
+-------+-----------------------------------------+-----------+
| TBA | End.T with NEXT-CSID, PSP & USP | This I-D. |
+-------+-----------------------------------------+-----------+
| TBA | End.T with NEXT-CSID & USD | This I-D. |
+-------+-----------------------------------------+-----------+
| TBA | End.T with NEXT-CSID, PSP & USD | This I-D. |
+-------+-----------------------------------------+-----------+
| TBA | End.T with NEXT-CSID, USP & USD | This I-D. |
+-------+-----------------------------------------+-----------+
| TBA | End.T with NEXT-CSID, PSP, USP & USD | This I-D. |
+-------+-----------------------------------------+-----------+
| TBA | End.B6.Encaps with NEXT-CSID | This I-D. |
+-------+-----------------------------------------+-----------+
| TBA | End.B6.Encaps.Red with NEXT-CSID | This I-D. |
+-------+-----------------------------------------+-----------+
| TBA | End.BM with NEXT-CSID | This I-D. |
+-------+-----------------------------------------+-----------+
| 101 | End with REPLACE-CSID | This I-D. |
+-------+-----------------------------------------+-----------+
| 102 | End with REPLACE-CSID & PSP | This I-D. |
+-------+-----------------------------------------+-----------+
| 103 | End with REPLACE-CSID & USP | This I-D. |
+-------+-----------------------------------------+-----------+
| 104 | End with REPLACE-CSID, PSP & USP | This I-D. |
+-------+-----------------------------------------+-----------+
| 105 | End.X with REPLACE-CSID | This I-D. |
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+-------+-----------------------------------------+-----------+
| 106 | End.X with REPLACE-CSID & PSP | This I-D. |
+-------+-----------------------------------------+-----------+
| 107 | End.X with REPLACE-CSID & USP | This I-D. |
+-------+-----------------------------------------+-----------+
| 108 | End.X with REPLACE-CSID, PSP & USP | This I-D. |
+-------+-----------------------------------------+-----------+
| 109 | End.T with REPLACE-CSID | This I-D. |
+-------+-----------------------------------------+-----------+
| 110 | End.T with REPLACE-CSID & PSP | This I-D. |
+-------+-----------------------------------------+-----------+
| 111 | End.T with REPLACE-CSID & USP | This I-D. |
+-------+-----------------------------------------+-----------+
| 112 | End.T with REPLACE-CSID, PSP & USP | This I-D. |
+-------+-----------------------------------------+-----------+
| 114 | End.B6.Encaps with REPLACE-CSID | This I-D. |
+-------+-----------------------------------------+-----------+
| 115 | End.BM with REPLACE-CSID | This I-D. |
+-------+-----------------------------------------+-----------+
| 116 | End.DX6 with REPLACE-CSID | This I-D. |
+-------+-----------------------------------------+-----------+
| 117 | End.DX4 with REPLACE-CSID | This I-D. |
+-------+-----------------------------------------+-----------+
| 118 | End.DT6 with REPLACE-CSID | This I-D. |
+-------+-----------------------------------------+-----------+
| 119 | End.DT4 with REPLACE-CSID | This I-D. |
+-------+-----------------------------------------+-----------+
| 120 | End.DT46 with REPLACE-CSID | This I-D. |
+-------+-----------------------------------------+-----------+
| 121 | End.DX2 with REPLACE-CSID | This I-D. |
+-------+-----------------------------------------+-----------+
| 122 | End.DX2V with REPLACE-CSID | This I-D. |
+-------+-----------------------------------------+-----------+
| 123 | End.DX2U with REPLACE-CSID | This I-D. |
+-------+-----------------------------------------+-----------+
| 124 | End.DT2M with REPLACE-CSID | This I-D. |
+-------+-----------------------------------------+-----------+
| 127 | End.B6.Encaps.Red with REPLACE-CSID | This I-D. |
+-------+-----------------------------------------+-----------+
| 128 | End with REPLACE-CSID & USD | This I-D. |
+-------+-----------------------------------------+-----------+
| 129 | End with REPLACE-CSID, PSP & USD | This I-D. |
+-------+-----------------------------------------+-----------+
| 130 | End with REPLACE-CSID, USP & USD | This I-D. |
+-------+-----------------------------------------+-----------+
| 131 | End with REPLACE-CSID, PSP, USP & USD | This I-D. |
+-------+-----------------------------------------+-----------+
| 132 | End.X with REPLACE-CSID & USD | This I-D. |
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+-------+-----------------------------------------+-----------+
| 133 | End.X with REPLACE-CSID, PSP & USD | This I-D. |
+-------+-----------------------------------------+-----------+
| 134 | End.X with REPLACE-CSID, USP & USD | This I-D. |
+-------+-----------------------------------------+-----------+
| 135 | End.X with REPLACE-CSID, PSP, USP & USD | This I-D. |
+-------+-----------------------------------------+-----------+
| 136 | End.T with REPLACE-CSID & USD | This I-D. |
+-------+-----------------------------------------+-----------+
| 137 | End.T with REPLACE-CSID, PSP & USD | This I-D. |
+-------+-----------------------------------------+-----------+
| 138 | End.T with REPLACE-CSID, USP & USD | This I-D. |
+-------+-----------------------------------------+-----------+
| 139 | End.T with REPLACE-CSID, PSP, USP & USD | This I-D. |
+-------+-----------------------------------------+-----------+
Table 1: Registration List
16. Acknowledgements
The authors would like to thank Kamran Raza, Xing Jiang, YuanChao Su,
Han Li, Yisong Liu, and Martin Vigoureux for their insightful
feedback and suggestions.
17. References
17.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>.
[RFC8402] Filsfils, C., Ed., Previdi, S., Ed., Ginsberg, L.,
Decraene, B., Litkowski, S., and R. Shakir, "Segment
Routing Architecture", RFC 8402, DOI 10.17487/RFC8402,
July 2018, <https://www.rfc-editor.org/info/rfc8402>.
[RFC8754] Filsfils, C., Ed., Dukes, D., Ed., Previdi, S., Leddy, J.,
Matsushima, S., and D. Voyer, "IPv6 Segment Routing Header
(SRH)", RFC 8754, DOI 10.17487/RFC8754, March 2020,
<https://www.rfc-editor.org/info/rfc8754>.
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[RFC8986] Filsfils, C., Ed., Camarillo, P., Ed., Leddy, J., Voyer,
D., Matsushima, S., and Z. Li, "Segment Routing over IPv6
(SRv6) Network Programming", RFC 8986,
DOI 10.17487/RFC8986, February 2021,
<https://www.rfc-editor.org/info/rfc8986>.
17.2. Informative References
[EMAIL1] "SPRING chairs email on the adoption of draft-
filsfilscheng-spring-srv6-srh-compression-02", October
2021, <https://mailarchive.ietf.org/arch/msg/spring/
VjVIxo7fZFhsIHJ5wFQXIBvvtNM/>.
[EMAIL2] "SPRING chairs email on working group process", February
2022, <https://mailarchive.ietf.org/arch/msg/spring/
vCc9Ckvwu5HA-RCleV712dsA5OA/>.
[I-D.clad-spring-srv6-srh-compression-illus]
Clad, F. and D. Dukes, "Illustrations for Compressed SRv6
Segment List Encoding in SRH", Work in Progress, Internet-
Draft, draft-clad-spring-srv6-srh-compression-illus-02, 24
October 2022, <https://datatracker.ietf.org/doc/html/
draft-clad-spring-srv6-srh-compression-illus-02>.
[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-00, 9 March 2023,
<https://datatracker.ietf.org/doc/html/draft-ietf-idr-bgp-
ls-sr-policy-00>.
[I-D.ietf-idr-bgpls-srv6-ext]
Dawra, G., Filsfils, C., Talaulikar, K., Chen, M.,
Bernier, D., and B. Decraene, "BGP Link State Extensions
for SRv6", Work in Progress, Internet-Draft, draft-ietf-
idr-bgpls-srv6-ext-14, 17 February 2023,
<https://datatracker.ietf.org/doc/html/draft-ietf-idr-
bgpls-srv6-ext-14>.
[I-D.ietf-idr-segment-routing-te-policy]
Previdi, S., Filsfils, C., Talaulikar, K., Mattes, P.,
Jain, D., and S. Lin, "Advertising Segment Routing
Policies in BGP", Work in Progress, Internet-Draft, draft-
ietf-idr-segment-routing-te-policy-20, 27 July 2022,
<https://datatracker.ietf.org/doc/html/draft-ietf-idr-
segment-routing-te-policy-20>.
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[I-D.ietf-lsr-ospfv3-srv6-extensions]
Li, Z., Hu, Z., Talaulikar, K., and P. Psenak, "OSPFv3
Extensions for SRv6", Work in Progress, Internet-Draft,
draft-ietf-lsr-ospfv3-srv6-extensions-09, 14 January 2023,
<https://datatracker.ietf.org/doc/html/draft-ietf-lsr-
ospfv3-srv6-extensions-09>.
[I-D.ietf-pce-segment-routing-ipv6]
Li, C., Negi, M. S., Sivabalan, S., Koldychev, M.,
Kaladharan, P., and Y. Zhu, "Path Computation Element
Communication Protocol (PCEP) Extensions for Segment
Routing leveraging the IPv6 dataplane", Work in Progress,
Internet-Draft, draft-ietf-pce-segment-routing-ipv6-16, 6
March 2023, <https://datatracker.ietf.org/doc/html/draft-
ietf-pce-segment-routing-ipv6-16>.
[I-D.srcompdt-spring-compression-requirement]
Cheng, W., Xie, C., Bonica, R., Dukes, D., Li, C., Peng,
S., and W. Henderickx, "Compressed SRv6 SID List
Requirements", Work in Progress, Internet-Draft, draft-
srcompdt-spring-compression-requirement-07, 11 July 2021,
<https://datatracker.ietf.org/doc/html/draft-srcompdt-
spring-compression-requirement-07>.
[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>.
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[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-C-SID 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>.
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[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>.
[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,
B., Zhuang, S., and J. Rabadan, "BGP Overlay Services
Based on Segment Routing over IPv6 (SRv6)", RFC 9252,
DOI 10.17487/RFC9252, July 2022,
<https://www.rfc-editor.org/info/rfc9252>.
[RFC9259] Ali, Z., Filsfils, C., Matsushima, S., Voyer, D., and M.
Chen, "Operations, Administration, and Maintenance (OAM)
in Segment Routing over IPv6 (SRv6)", RFC 9259,
DOI 10.17487/RFC9259, June 2022,
<https://www.rfc-editor.org/info/rfc9259>.
[RFC9352] Psenak, P., Ed., Filsfils, C., Bashandy, A., Decraene, B.,
and Z. Hu, "IS-IS Extensions to Support Segment Routing
over the IPv6 Data Plane", RFC 9352, DOI 10.17487/RFC9352,
February 2023, <https://www.rfc-editor.org/info/rfc9352>.
[SPRING-WG-POLICIES]
SPRING Working Group Chairs, "SPRING Working Group
Policies", 14 October 2022,
<https://wiki.ietf.org/en/group/spring/WG_Policies>.
Appendix A. Open Issues
This section is to be removed before publishing as an RFC.
This section was added as requested by the SPRING chair in [EMAIL1].
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Issues raised during and after the adoption call for this draft are
tracked in an issue tracker. The remainder of this section
identifies the most significant open issues, from the adoption call,
for the working group to keep track of.
As a reminder to those reading this section, this document is a work
in progress, and subject to change by the working group. As noted at
the front of this document, "It is inappropriate to use Internet-
Drafts as reference material"
* Given that the working group has said that it wants to standardize
one data plane solution, and given that the document contains
multiple SRv6 EndPoint behaviors that some WG members have stated
are multiple data plane solutions, the working group will address
whether this is valid and coherent with its one data plane
solution objective.
* As reminded in the conclusion of the adoption call, this document
is subject to the policy announced by the SPRING chairs in
[EMAIL2]. In particular, this means that this document can not go
to WG last call until 6man completes handling of an Internet Draft
that deals with the relationship of C-SIDs to RFC 4291. It is
hoped and expected that said resolution will be a WG last call and
document approval in 6man of a document providing for the way that
C-SIDs use the IPv6 destination address field.
Appendix B. Complete pseudocodes
The content of this section is purely informative rendering of the
pseudocodes of [RFC8986] with the modifications in this document.
This rendering may not be used as a reference.
B.1. End with NEXT-C-SID
When processing the SRH of a packet matching a FIB entry locally
instantiated as an End SID with the NEXT-C-SID flavor:
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S01. If (DA.Argument != 0) {
S02. If (IPv6 Hop Limit <= 1) {
S03. Send an ICMP Time Exceeded message to the Source Address
with Code 0 (Hop limit exceeded in transit),
interrupt packet processing, and discard the packet.
S04. }
S05. Copy the value of DA.Argument into the bits [LBL..(LBL+AL-1)]
of the Destination Address.
S06. Set the bits [(LBL+AL)..127] of the Destination Address to
zero.
S07. Decrement IPv6 Hop Limit by 1.
S08. Submit the packet to the egress IPv6 FIB lookup for
transmission to the next destination.
S9. }
S10. If (Segments Left == 0) {
S11. Stop processing the SRH, and proceed to process the next
header in the packet, whose type is identified by
the Next Header field in the routing header.
S12. }
S13. If (IPv6 Hop Limit <= 1) {
S14. Send an ICMP Time Exceeded message to the Source Address
with Code 0 (Hop limit exceeded in transit),
interrupt packet processing, and discard the packet.
S15. }
S16. max_LE = (Hdr Ext Len / 2) - 1
S17. If ((Last Entry > max_LE) or (Segments Left > Last Entry+1)) {
S18. Send an ICMP Parameter Problem to the Source Address
with Code 0 (Erroneous header field encountered)
and Pointer set to the Segments Left field,
interrupt packet processing, and discard the packet.
S19. }
S20. Decrement IPv6 Hop Limit by 1.
S21. Decrement Segments Left by 1.
S22. Update IPv6 DA with Segment List[Segments Left].
S23. Submit the packet to the egress IPv6 FIB lookup for
transmission to the new destination.
Before processing the Upper-Layer header or any IPv6 extension header
other than Hop-by-Hop or Destination Option of a packet matching a
FIB entry locally instantiated as an End SID with the NEXT-C-SID
flavor:
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S01. If (DA.Argument != 0) {
S02. If (IPv6 Hop Limit <= 1) {
S03. Send an ICMP Time Exceeded message to the Source Address,
Code 0 (Hop limit exceeded in transit),
interrupt packet processing and discard the packet.
S04. }
S05. Copy the value of DA.Argument into the bits [LBL..(LBL+AL-1)]
of the Destination Address.
S06. Set the bits [(LBL+AL)..127] of the Destination Address to
zero.
S07. Decrement Hop Limit by 1.
S08. Submit the packet to the egress IPv6 FIB lookup for
transmission to the next destination.
S09. }
When processing the Upper-Layer header of a packet matching a FIB
entry locally instantiated as an End SID with the NEXT-C-SID flavor:
S01. If (Upper-Layer header type is allowed by local configuration) {
S02. Proceed to process the Upper-Layer header
S03. } Else {
S04. Send an ICMP Parameter Problem to the Source Address
with Code 4 (SR Upper-layer Header Error)
and Pointer set to the offset of the Upper-Layer header,
interrupt packet processing, and discard the packet.
S05. }
B.2. End with REPLACE-C-SID
When processing the SRH of a packet matching a FIB entry locally
instantiated as an End SID with the REPLACE-C-SID flavor:
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S01. When an SRH is processed {
S02. If (Segments Left == 0 and (DA.Arg.Index == 0 or
Segment List[0][DA.Arg.Index-1] == 0)) {
S03. Stop processing the SRH, and proceed to process the next
header in the packet, whose type is identified by
the Next Header field in the routing header.
S04. }
S05. If (IPv6 Hop Limit <= 1) {
S06. Send an ICMP Time Exceeded message to the Source Address,
Code 0 (Hop limit exceeded in transit),
interrupt packet processing and discard the packet.
S07. }
S08. max_LE = (Hdr Ext Len / 2) - 1
S09. If (DA.Arg.Index != 0) {
S10. If ((Last Entry > max_LE) or (Segments Left > Last Entry)) {
S11. Send an ICMP Parameter Problem to the Source Address,
Code 0 (Erroneous header field encountered),
Pointer set to the Segments Left field,
interrupt packet processing and discard the packet.
S12. }
S13. Decrement DA.Arg.Index by 1.
S14. If (Segment List[Segments Left][DA.Arg.Index] == 0) {
S15. Decrement Segments Left by 1.
S16. Decrement IPv6 Hop Limit by 1.
S17. Update IPv6 DA with Segment List[Segments Left]
S18. Submit the packet to the egress IPv6 FIB lookup for
transmission to the new destination.
S19. }
S20. } Else {
S21. If((Last Entry > max_LE) or (Segments Left > Last Entry+1)){
S22. Send an ICMP Parameter Problem to the Source Address,
Code 0 (Erroneous header field encountered),
Pointer set to the Segments Left field,
interrupt packet processing and discard the packet.
S23. }
S24. Decrement Segments Left by 1.
S25. Set DA.Arg.Index to (128/NF - 1).
S26. }
S27. Decrement IPv6 Hop Limit by 1.
S28. Write Segment List[Segments Left][DA.Arg.Index] into the bits
[B..B+NF-1] of the Destination Address of the IPv6 header.
S29. Submit the packet to the egress IPv6 FIB lookup for
transmission to the new destination.
S30. }
When processing the Upper-Layer header of a packet matching a FIB
entry locally instantiated as an End SID with the REPLACE-C-SID
flavor:
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S01. If (Upper-Layer header type is allowed by local configuration) {
S02. Proceed to process the Upper-Layer header
S03. } Else {
S04. Send an ICMP Parameter Problem to the Source Address
with Code 4 (SR Upper-layer Header Error)
and Pointer set to the offset of the Upper-Layer header,
interrupt packet processing, and discard the packet.
S05. }
Contributors
Liu Aihua
ZTE Corporation
China
Email: liu.aihua@zte.com.cn
Dennis Cai
Alibaba
United States of America
Email: d.cai@alibaba-inc.com
Darren Dukes
Cisco Systems, Inc.
Canada
Email: ddukes@cisco.com
James N Guichard
Futurewei Technologies Ltd.
United States of America
Email: james.n.guichard@futurewei.com
Cheng Li
Huawei Technologies
China
Email: c.l@huawei.com
Robert Raszuk
NTT Network Innovations
United States of America
Email: robert@raszuk.net
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Ketan Talaulikar
Cisco Systems, Inc.
India
Email: ketant.ietf@gmail.com
Daniel Voyer
Bell Canada
Canada
Email: daniel.voyer@bell.ca
Shay Zadok
Broadcom
Israel
Email: shay.zadok@broadcom.com
Authors' Addresses
Weiqiang Cheng (editor)
China Mobile
China
Email: chengweiqiang@chinamobile.com
Clarence Filsfils
Cisco Systems, Inc.
Belgium
Email: cf@cisco.com
Zhenbin Li
Huawei Technologies
China
Email: lizhenbin@huawei.com
Bruno Decraene
Orange
France
Email: bruno.decraene@orange.com
Francois Clad (editor)
Cisco Systems, Inc.
France
Email: fclad@cisco.com
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