



SPRING                                                           R. Chen
Internet-Draft                                                   D. Zhao
Intended status: Standards Track                         ZTE Corporation
Expires: 31 July 2026                                    27 January 2026


           SRv6 NET-PGM extension: Compressed BSID Insertion
          draft-chen-spring-srv6-compressed-bsid-insertion-02

Abstract

   The End.B6.Insert and End.B6.Insert.Red SHOULD support the NEXT-C-SID
   flavor either individually or in combinations.  This document defines
   the SRH processing of the End.B6.Insert and End.B6.Insert.Red with
   NEXT-C-SID flavor.

Status of This Memo

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   provisions of BCP 78 and BCP 79.

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   This Internet-Draft will expire on 31 July 2026.

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   Copyright (c) 2026 IETF Trust and the persons identified as the
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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-C-SID flavor  . . . . . . . . . .   3
     2.2.  End.B6.Insert red with NEXT-C-SID flavor  . . . . . . . .   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-C-SID flavor.
   With the NEXT-C-SID 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-C-SID
   flavor either individually or in combinations.  This document defines
   the SRH processing of the End.B6.Insert and End.B6.Insert.Red with
   NEXT-C-SID flavor.

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-C-SID flavor.






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2.1.  End.B6.Insert with NEXT-C-SID flavor

   End.B6.Insert with NEXT-C-SID: 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-C-SID
   Flavor, 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-C-SID Flavor 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-C-SID Flavor 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-C-SID Flavor 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-C-SID Flavor 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-C-SID flavor

   This is an optimization of the End.B6.Insert with NEXT-C-SID flavor
   behavior.







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   End.B6.Insert.Red with NEXT-C-SID flavor 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.

   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-C-SID flavor and End.B6.Insert.Red with NEXT-
   C-SID flavor.

   This document requests the IANA to allocate, within the "SRv6
   Endpoint Behaviors" sub-registry belonging to the top-level "Segment-
   routing with IPv6 dataplane (SRv6) Parameters" registry, the
   following allocations:

   Value                Endpoint Behavior              Reference
   ------------------------------------------------------------------
   TBD1     End.B6.Insert with NEXT-C-SID flavor      This document
   TBD2     End.B6.Insert.Red with NEXT-C-SID flavor  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>.







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   [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>.

   [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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