SRv6 NET-PGM extension: Compressed BSID Insertion
draft-chen-spring-srv6-compressed-bsid-insertion-03
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| Document | Type | Active Internet-Draft (individual) | |
|---|---|---|---|
| Authors | Ran Chen , Detao Zhao | ||
| Last updated | 2026-08-24 | ||
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draft-chen-spring-srv6-compressed-bsid-insertion-03
SPRING R. Chen
Internet-Draft D. Zhao
Intended status: Standards Track ZTE Corporation
Expires: 25 February 2027 24 August 2026
SRv6 NET-PGM extension: Compressed BSID Insertion
draft-chen-spring-srv6-compressed-bsid-insertion-03
Abstract
The End.B6.Insert and End.B6.Insert.Red SHOULD support the NEXT-CSID
flavor either individually or in combinations. This document defines
the SRH processing of the End.B6.Insert and End.B6.Insert.Red with
NEXT-CSID.
Status of This Memo
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provisions of BCP 78 and BCP 79.
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material or to cite them other than as "work in progress."
This Internet-Draft will expire on 25 February 2027.
Copyright Notice
Copyright (c) 2026 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/
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Please review these documents carefully, as they describe your rights
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provided without warranty as described in the Revised BSD License.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Requirements Language . . . . . . . . . . . . . . . . . . 2
2. SRv6 endpoint behaviors . . . . . . . . . . . . . . . . . . . 2
2.1. End.B6.Insert with NEXT-CSID . . . . . . . . . . . . . . 3
2.2. End.B6.Insert red with NEXT-CSID . . . . . . . . . . . . 5
3. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6
4. Security Considerations . . . . . . . . . . . . . . . . . . . 6
5. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 6
6. Normative References . . . . . . . . . . . . . . . . . . . . 6
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 7
1. Introduction
[I-D.filsfils-spring-srv6-net-pgm-insertion] extends the SRv6 Network
Programming [RFC8986] model with new endpoint and transit behaviors
enabling the insertion of an SRH after the outer IPv6 header of the
SR domain, called End.B6.Insert and End.B6.Insert.Red.
[RFC9800] specifies the new flavors to the SR segment endpoint
behaviors defined in [RFC8986] that enable a compressed encoding of
the SRv6 segment list. One of the flavor is the NEXT-CSID flavor.
With the NEXT-CSID flavor, each C-SID container is a fully formed
SRv6 SID with the common Locator-Block for all the C-SIDs in the
C-SID container, a Locator-Node and Function that are those of the
first C-SID, and an Argument carrying the subsequent C-SIDs.
The End.B6.Insert and End.B6.Insert.Red SHOULD support the NEXT-CSID
flavor either individually or in combinations. This document defines
the SRH processing of the End.B6.Insert and End.B6.Insert.Red with
NEXT-CSID.
1.1. 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.
2. SRv6 endpoint behaviors
This section defines the SRH processing of the End.B6.Insert and
End.B6.Insert.Red with NEXT-CSID.
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2.1. End.B6.Insert with NEXT-CSID
End.B6.Insert with NEXT-CSID: Endpoint bound to an SRv6 policy. The
"Endpoint bound to an SRv6 Policy" is a variant of the End behavior.
When N receives a packet whose IPv6 DA is S and S matching a FIB
entry locally instantiated as an End.B6.Insert SID with NEXT-CSID,
does:
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N01. If (DA.Argument!= 0) {
N02. If (IPv6 Hop Limit <= 1) {
N03. Send an ICMP Time Exceeded message to the Source
Address, Code 0 (Hop limit exceeded in transit),
interrupt packet processing and discard the packet.
N04. }
N05. Copy DA.Argument into the bits [LBL..(LBL+AL-1)]
of the Destination Address.
N06. Set the bits [(LBL+AL)..127] of the Destination
Address to zero.
N07. Decrement IPv6 Hop Limit by 1.
N08.1.Insert a new SRH in between the IPv6 Header and
the received SRH containing the list of segments of B.
N08.2. Set the new SRH[0] to the IPv6 DA .
N08.3. Set the IPv6 DA to the first segment of B.
N08.4. Submit the packet to the egress IPv6 FIB lookup for
transmission to the next destination.
N09. }
S02. If (Segments Left == 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
with 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 ((Last Entry > max_LE)or(Segments Left > Last Entry+1)){
S10. 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.
S11. }
S12. Decrement IPv6 Hop Limit by 1.
S13. Decrement Segments Left by 1.
S14. Update IPv6 DA with Segment List[Segments Left].
S15. Insert a new SRH in between the IPv6 Header and the received
SRH containing the list of segments of B.
S16. Set the IPv6 DA to the first SID of B.
S17. Submit the packet to the egress IPv6 FIB lookup for
transmission to the new destination.
S18. }
Examples:
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uBSID is an End.B6.Insert with NEXT-CSID SID, and the
corresponding segment-list is <fc00:2024:uSID20::,fc00:2024:uSID21>.
case1, uBSID is the non-last SID of the container:
Node N receives a packet:
IPv6：SA = 2024::1, DA=FC00:2024:uBSID:uSID2:uSID3
:uSID4::uSID5:uSID6::
SRH1:(FC00:2024:uSID7:uSID8::,FC00:2024:uBSID:uSID2
:uSID3:uSID4:uSID5:uSID6::;SL=1)
After the End.B6.Insert with NEXT-CSID behavior,
the packet looks like:
IPv6：SA = 2024::1, DA=FC00:2024:uSID20:uSID21::
SRH2:(FC00:2024:uSID2:uSID3:uSID4::uSID5:uSID6::,
FC00:2024:uSID20:uSID21::;SL=1)
SRH1:(FC00:2024:uSID7:uSID8::,
FC00:2024:uBSID:uSID2:uSID3:uSID4:uSID5:uSID6::;SL=1)
case2, uBSID is the last SID of the C-SID container:
Node N receives a packet:
IPv6：SA = 2024::1, DA=FC00:2024:uBSID::
SRH1:(FC00:2024:uSID7:uSID8::,
FC00:2024:uSID2:uSID3:uSID4:uSID5:uSID6:uBSID::;SL=1)
After the End.B6.Insert with NEXT-CSID behavior,
the packet looks like:
IPv6：SA = 2024::1, DA=FC00:2024:uSID20:uSID21::
SRH2:(FC00:2024:uSID20:uSID21::;SL=0);SRH2 may be omit
SRH1:(FC00:2024:uSID7:uSID8::,
FC00:2024:uSID2:uSID3:uSID4:uSID5:uSID6:uBSID::;SL=1)
case3, uBSID is in the last of the C-SID container of the SRH:
Node N receives a packet:
IPv6：SA = 2024::1, DA=FC00:2024:uBSID:uSID7:uSID8::
SRH1:(FC00:2024:uBSID:uSID7:uSID8::,
FC00:2024:uSID1:uSID2:uSID3:uSID4:uSID5:uSID6::;SL=0)
After the End.B6.Insert with NEXT-CSID behavior,
the packet looks like:
IPv6：SA = 2024::1, DA=FC00:2024:uSID20:uSID21::
SRH2:(FC00:2024:uSID7:uSID8::,FC00:2024:uSID20:uSID21::;SL=1)
SRH1:(FC00:2024:uBSID:uSID7:uSID8::,
FC00:2024:uSID1:uSID2:uSID3:uSID4:uSID5:uSID6::;SL=0)
2.2. End.B6.Insert red with NEXT-CSID
This is an optimization of the End.B6.Insert with NEXT-CSID behavior.
End.B6.Insert.Red with NEXT-CSID reduces the size of the new SRH by
one SID by avoiding the insertion of the first SID in the pushed SRH.
In this way, the first SID is only written in the DA and the packet
is forwarded according to it.
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The new SRH is created as described in Section 4.1.1 of [RFC8754].
3. IANA Considerations
The document defines two new SRv6 Endpoint behaviors called
End.B6.Insert with NEXT-CSID and End.B6.Insert.Red with NEXT-CSID.
This document requests the IANA to allocate, within the "SRv6
Endpoint Behaviors" sub-registry belonging to the top-level "Segment-
Routing" registry, the following allocations:
Value Endpoint Behavior Reference
--------------------------------------------------------------------
188 End.B6.Insert with NEXT-CSID This document
189 End.B6.Insert.Red with NEXT-CSID This document
Figure 1
4. Security Considerations
The security requirements and mechanisms described in [RFC8402],
[RFC8754] and [RFC8986] also apply to this document, and this
document does not introduce any new security considerations.
5. Acknowledgements
TBD.
6. Normative References
[I-D.filsfils-spring-srv6-net-pgm-insertion]
Filsfils, C., Camarillo, P., Leddy, J., Voyer, D.,
Matsushima, S., and Z. Li, "SRv6 NET-PGM extension:
Insertion", Work in Progress, Internet-Draft, draft-
filsfils-spring-srv6-net-pgm-insertion-09, 16 August 2023,
<https://datatracker.ietf.org/doc/html/draft-filsfils-
spring-srv6-net-pgm-insertion-09>.
[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>.
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[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>.
[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>.
[RFC9800] Cheng, W., Ed., Filsfils, C., Li, Z., Decraene, B., and F.
Clad, Ed., "Compressed SRv6 Segment List Encoding",
RFC 9800, DOI 10.17487/RFC9800, June 2025,
<https://www.rfc-editor.org/info/rfc9800>.
Authors' Addresses
Ran Chen
ZTE Corporation
Nanjing
China
Email: chen.ran@zte.com.cn
Detao Zhao
ZTE Corporation
Nanjing
China
Email: zhao.detao@zte.com.cn
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