Network                                                           L. Yao
Internet-Draft                                                 P. Shaofu
Intended status: Standards Track                         ZTE Corporation
Expires: 20 February 2022                                 19 August 2021


         Advertising Segment Routing Policies Attributes in BGP
            draft-peng-idr-segment-routing-te-policy-attr-01

Abstract

   This document proposes extensions of BGP and defines some new Segment
   Types with algorithm information to meet more requirements when
   delivering SR Policy via BGP.

Status of This Memo

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   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
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   This Internet-Draft will expire on 20 February 2022.

Copyright Notice

   Copyright (c) 2021 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
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   provided without warranty as described in the Simplified BSD License.






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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Requirements Language . . . . . . . . . . . . . . . . . .   3
   2.  New Segment Types for SR-MPLS Adjacency with optional
           Algorithm . . . . . . . . . . . . . . . . . . . . . . . .   3
     2.1.  Type M: IPv4 Address + Local Interface ID with optional
           Algorithm . . . . . . . . . . . . . . . . . . . . . . . .   3
     2.2.  Type N: IPv4 Local and Remote addresses with optional
           Algorithm . . . . . . . . . . . . . . . . . . . . . . . .   4
     2.3.  Type O: IPv6 Address + Interface ID for local and remote
           pair with optional Algorithm related SID for SR MPLS  . .   5
     2.4.  Type P: IPv6 Local and Remote addresses with optional
           Algorithm for SR MPLS . . . . . . . . . . . . . . . . . .   6
   3.  New Segment Types for SID only, with optional Algorithm . . .   7
     3.1.  Type L: MPLS SID only, with optional Algorithm  . . . . .   7
     3.2.  Type Q: SRv6 SID only, with optional Algorithm  . . . . .   8
   4.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   8
   5.  Security Considerations . . . . . . . . . . . . . . . . . . .   9
   6.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   9
   7.  Normative References  . . . . . . . . . . . . . . . . . . . .   9
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  12

1.  Introduction

   Segment Routing (SR) [RFC8402] allows a headend node to steer a
   packet flow along any path.  Intermediate per-flow states are
   eliminated thanks to source routing.

   [I-D.ietf-spring-segment-routing-policy] details the concepts of SR
   Policy and steering into an SR Policy.  These apply equally to the
   MPLS and IPv6 data plane instantiations of Segment Routing with their
   respective representations of segments as SR-MPLS SID and SRv6 SID as
   described in [RFC8402].

   [I-D.ietf-idr-segment-routing-te-policy] specifies the way to use BGP
   to distribute one or more of the candidate paths of an SR Policy to
   the headend of that policy.  It defines a new BGP address family
   (SAFI), i.e., SR Policy SAFI NLRI.  In UPDATE messages of that
   address family, the NLRI identifies an SR Policy Candidate Path, and
   the attributes encode the segment lists and other details of that SR
   Policy Candidate Path. 11 Segment Types (from A to K) are defined to
   encode SR-MPLS or SRv6 segments.

   As specified in [I-D.ietf-idr-segment-routing-te-policy], the SR
   algorithm can be optionally specified for Segment Types C(IPv4 Node
   and SID), D(IPv6 Node and SID for SR-MPLS), I(IPv6 Node and SID for
   SRv6), J(IPv6 Node, index for remote and local pair, and SID for



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   SRv6), and K(IPv6 Local/Remote addresses and SID for SRv6).  That is,
   currently the algorithm can be carried along with SR-MPLS prefix SID,
   SRv6 prefix SID and SRv6 adjacency SID when delivering SR Policy via
   BGP.

   This document proposes extensions of BGP and defines some new Segment
   Types with algorithm information to meet more requirements when
   delivering SR Policy via BGP.

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.  New Segment Types for SR-MPLS Adjacency with optional Algorithm

   [I-D.ietf-lsr-algorithm-related-adjacency-sid] complements that the
   algorithm can be also included as part of an Adjacency-SID
   advertisement for SR-MPLS, in scenarios where multiple algorithm
   share the same link resource.  In this case, an SR-MPLS Policy
   advertised to the headend may also contain algorithm specific
   Adjacency-SID.

   This section defines 4 new Segment Sub-TLVs of Segment List Sub-TLV
   to provide algorithm information for SR-MPLS Adjacency-SID.

   The processing procedures for SID with algorithm specified in
   [I-D.ietf-spring-segment-routing-policy] and
   [I-D.ietf-idr-segment-routing-te-policy] are still applicable for the
   new segment types.  When the algorithm is not specified for the SID
   types above which optionally allow for it, the headend SHOULD use the
   Strict Shortest Path algorithm if available; otherwise, it SHOULD use
   the default Shortest Path algorithm.

2.1.  Type M: IPv4 Address + Local Interface ID with optional Algorithm

   The Type M Segment Sub-TLV is similar with existed Type E Segment
   Sub-TLV, it also encodes an IPv4 node address, a local interface
   Identifier (Local Interface ID) and an optional SR-MPLS SID, but with
   additional algorithm information.  The format is as follows:








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       0                   1                   2                   3
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |     Type      |   Length      |     Flags     |  SR Algorithm |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                 Local Interface ID (4 octets)                 |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                 IPv4 Node Address (4 octets)                  |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                SR-MPLS SID (optional, 4 octets)               |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                                  Figure 1

   Where:

   SR Algorithm: 1 octet specifying SR Algorithm as described in section
   3.1.1 in [RFC8402] when A-Flag as defined in section 2.4.4.2.12
   [I-D.ietf-idr-segment-routing-te-policy] is present.  SR Algorithm is
   used by SRPM as described in section 4 in
   [I-D.ietf-spring-segment-routing-policy].  When A-Flag is not
   encoded, this field SHOULD be set to zero on transmission and MUST be
   ignored on receipt.

   Other fields have the same meaning as the existing Type E Segment
   Sub-TLV.

2.2.  Type N: IPv4 Local and Remote addresses with optional Algorithm

   The Type N Segment Sub-TLV is similar with existed Type F Segment
   Sub-TLV, it also encodes an adjacency local address, an adjacency
   remote address and an optional SR-MPLS SID, but with additional
   algorithm information.  The format is as follows:


       0                   1                   2                   3
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |     Type      |   Length      |     Flags     |  SR Algorithm |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                Local IPv4 Address (4 octets)                  |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                Remote IPv4 Address  (4 octets)                |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                SR-MPLS SID (optional, 4 octets)               |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                                  Figure 2



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   Where:

   SR Algorithm: 1 octet specifying SR Algorithm as described in section
   3.1.1 in [RFC8402] when A-Flag as defined in section 2.4.4.2.12
   [I-D.ietf-idr-segment-routing-te-policy] is present.  SR Algorithm is
   used by SRPM as described in section 4 in
   [I-D.ietf-spring-segment-routing-policy].  When A-Flag is not
   encoded, this field SHOULD be set to zero on transmission and MUST be
   ignored on receipt.

   Other fields have the same meaning as existed Type F Segment Sub-TLV.

2.3.  Type O: IPv6 Address + Interface ID for local and remote pair with
      optional Algorithm related SID for SR MPLS

   The Type O Segment Sub-TLV is similar with existed Type G Segment
   Sub-TLV, it also encodes an IPv6 Link Local adjacency with IPv6 local
   node address, a local interface identifier (Local Interface ID), IPv6
   remote node address , a remote interface identifier (Remote Interface
   ID) and an optional SR-MPLS SID, but with additional algorithm
   information.  The format is as follows:


       0                   1                   2                   3
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |     Type      |   Length      |     Flags     |  SR Algorithm |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                 Local Interface ID (4 octets)                 |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      //                IPv6 Local Node Address (16 octets)          //
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                 Remote Interface ID (4 octets)                |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      //                IPv6 Remote Node Address (16 octets)         //
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                SR-MPLS SID (optional, 4 octets)               |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                                  Figure 3

   Where:









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   SR Algorithm: 1 octet specifying SR Algorithm as described in section
   3.1.1 in [RFC8402] when A-Flag as defined in section 2.4.4.2.12
   [I-D.ietf-idr-segment-routing-te-policy] is present.  SR Algorithm is
   used by SRPM as described in section 4 in
   [I-D.ietf-spring-segment-routing-policy].  When A-Flag is not
   encoded, this field SHOULD be set to zero on transmission and MUST be
   ignored on receipt.

   Other fields have the same meaning as existed Type G Segment Sub-TLV.

2.4.  Type P: IPv6 Local and Remote addresses with optional Algorithm
      for SR MPLS

   The Type P Segment Sub-TLV is similar with existed Type H Segment
   Sub-TLV, it also encodes an adjacency local address, an adjacency
   remote address and an optional SR-MPLS SID, but with additional
   algorithm information.  The format is as follows:


       0                   1                   2                   3
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |     Type      |   Length      |     Flags     |  SR Algorithm |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      //               Local IPv6 Address (16 octets)                //
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      //               Remote IPv6 Address  (16 octets)              //
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                SR-MPLS SID (optional, 4 octets)               |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


                                  Figure 4

   Where:

   SR Algorithm: 1 octet specifying SR Algorithm as described in section
   3.1.1 in [RFC8402] when A-Flag as defined in section 2.4.4.2.12
   [I-D.ietf-idr-segment-routing-te-policy] is present.  SR Algorithm is
   used by SRPM as described in section 4 in
   [I-D.ietf-spring-segment-routing-policy].  When A-Flag is not
   encoded, this field SHOULD be set to zero on transmission and MUST be
   ignored on receipt.

   Other fields have the same meaning as existed Type H Segment Sub-TLV.






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3.  New Segment Types for SID only, with optional Algorithm

   Segment Sub-TLV for Type A defined in section 2.4.4.2.1
   [I-D.ietf-idr-segment-routing-te-policy] carries only the SID
   information in the form of MPLS Label.  Segment Sub-TLV for Type B
   defined in section 2.4.4.2.2 [I-D.ietf-idr-segment-routing-te-policy]
   carries only the SID information in the form of IPv6 address.

   If the algorithm information is carried along with the SIDs, it's
   useful in the scenarios below:

   Scenario 1: The algorithm may be optionally provided to the headend
   for verification purposes.  The headend can check if the SID value
   and the related algorithm received can be found in its SR-DB if
   requested to do so.

   Scenario 2: The headend may not know about the SID-related algorithm
   especially in the inter-domain scenario.  Providing the algorithm
   information benefits troubleshooting and network management.

   This section defines 2 new Segment Sub-TLVs of Segment List Sub-TLV
   to provide algorithm information for SR-MPLS/SRv6 SID.

3.1.  Type L: MPLS SID only, with optional Algorithm

   The Type L Segment Sub-TLV is similar with the Type A Segment Sub-
   TLV, it also encodes a single SR-MPLS SID, but with additional
   algorithm information.  The format is as follows:


       0                   1                   2                   3
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |     Type      |   Length      |     Flags     |  SR Algorithm |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |          Label                        | TC  |S|       TTL     |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                                  Figure 5

   Where:

   SR Algorithm: 1 octet specifying SR Algorithm as described in section
   3.1.1 in [RFC8402] when A-Flag as defined in section 2.4.4.2.12
   [I-D.ietf-idr-segment-routing-te-policy] is present.  When A-Flag is
   not encoded, this field SHOULD be set to zero on transmission and
   MUST be ignored on receipt.




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   Other fields have the same meaning as Type A Segment Sub-TLV.

3.2.  Type Q: SRv6 SID only, with optional Algorithm

   The Type Q Segment Sub-TLV is similar with existed Type B Segment
   Sub-TLV, it also encodes a single SRv6 SID, but with additional
   algorithm, endpoint behavior and SID strucutre information.  The
   format is as follows:


       0                   1                   2                   3
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |     Type      |   Length      |     Flags     |  SR Algorithm |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      //                       SRv6 SID (16 octets)                  //
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      //     SRv6 Endpoint Behavior and SID Structure (optional)     //
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


                                  Figure 6

   Where:

   Type: TBD

   Length is variable.

   SR Algorithm: 1 octet specifying SR Algorithm as described in section
   3.1.1 in [RFC8402] when A-Flag as defined in section 2.4.4.2.12
   [I-D.ietf-idr-segment-routing-te-policy] is present.  When A-Flag is
   not encoded, this field SHOULD be set to zero on transmission and
   MUST be ignored on receipt.

   Other fields have the same meaning as the Type B Segment Sub-TLV.

4.  IANA Considerations

   This document requests codepoint allocations for new Segment Sub-TLVs
   in the "SR Policy List Sub-TLVs" registry.










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Value  Description                                          Reference
------------------------------------------------------------------------
TBD1  Type L MPLS Algorithm related SID sub-TLV            This document
TBD2  Type M IPv4 Node, index and Algorithm related        This document
      SID sub-TLV
TBD3  Type N IPv4 Local/Remote addresses and Algorithm     This document
      related SID sub-TLV
TBD4  Type O IPv6 Node, index for remote and local pair    This document
      and Algorithm related SID for SR-MPLS sub-TLV
TBD5  Type P IPv6 Local/Remote addresses and Algorithm     This document
      related SID sub-TLV
TBD6  Type Q SRv6 Algorithm related SID sub-TLV            This document


                               Figure 7

5.  Security Considerations

   Procedures and protocol extensions defined in this document do not
   affect the security considerations discussed in
   [I-D.ietf-idr-segment-routing-te-policy].

6.  Acknowledgements

   TBD

7.  Normative References

   [I-D.ietf-idr-bgp-ls-segment-routing-ext]
              Previdi, S., Talaulikar, K., Filsfils, C., Gredler, H.,
              and M. Chen, "Border Gateway Protocol - Link State (BGP-
              LS) Extensions for Segment Routing", Work in Progress,
              Internet-Draft, draft-ietf-idr-bgp-ls-segment-routing-ext-
              18, 15 April 2021, <https://www.ietf.org/archive/id/draft-
              ietf-idr-bgp-ls-segment-routing-ext-18.txt>.

   [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-08, 8 June 2021,
              <https://www.ietf.org/archive/id/draft-ietf-idr-bgpls-
              srv6-ext-08.txt>.

   [I-D.ietf-idr-segment-routing-te-policy]
              Previdi, S., Filsfils, C., Talaulikar, K., Mattes, P.,
              Rosen, E., Jain, D., and S. Lin, "Advertising Segment
              Routing Policies in BGP", Work in Progress, Internet-



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              Draft, draft-ietf-idr-segment-routing-te-policy-13, 7 June
              2021, <https://www.ietf.org/archive/id/draft-ietf-idr-
              segment-routing-te-policy-13.txt>.

   [I-D.ietf-lsr-algorithm-related-adjacency-sid]
              Peng, S., Chen, R., Talaulikar, K., and P. Psenak,
              "Algorithm Related IGP-Adjacency SID Advertisement", Work
              in Progress, Internet-Draft, draft-ietf-lsr-algorithm-
              related-adjacency-sid-00, 10 June 2021,
              <https://www.ietf.org/archive/id/draft-ietf-lsr-algorithm-
              related-adjacency-sid-00.txt>.

   [I-D.ietf-lsr-flex-algo]
              Psenak, P., Hegde, S., Filsfils, C., Talaulikar, K., and
              A. Gulko, "IGP Flexible Algorithm", Work in Progress,
              Internet-Draft, draft-ietf-lsr-flex-algo-17, 6 July 2021,
              <https://www.ietf.org/archive/id/draft-ietf-lsr-flex-algo-
              17.txt>.

   [I-D.ietf-lsr-isis-srv6-extensions]
              Psenak, P., Filsfils, C., Bashandy, A., Decraene, B., and
              Z. Hu, "IS-IS Extensions to Support Segment Routing over
              IPv6 Dataplane", Work in Progress, Internet-Draft, draft-
              ietf-lsr-isis-srv6-extensions-17, 18 June 2021,
              <https://www.ietf.org/archive/id/draft-ietf-lsr-isis-srv6-
              extensions-17.txt>.

   [I-D.ietf-lsr-ospfv3-srv6-extensions]
              Li, Z., Hu, Z., Cheng, D., Talaulikar, K., and P. Psenak,
              "OSPFv3 Extensions for SRv6", Work in Progress, Internet-
              Draft, draft-ietf-lsr-ospfv3-srv6-extensions-02, 15
              February 2021, <https://www.ietf.org/archive/id/draft-
              ietf-lsr-ospfv3-srv6-extensions-02.txt>.

   [I-D.ietf-spring-segment-routing-policy]
              Filsfils, C., Talaulikar, K., Voyer, D., Bogdanov, A., and
              P. Mattes, "Segment Routing Policy Architecture", Work in
              Progress, Internet-Draft, draft-ietf-spring-segment-
              routing-policy-13, 28 May 2021,
              <https://www.ietf.org/archive/id/draft-ietf-spring-
              segment-routing-policy-13.txt>.










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   [I-D.ietf-spring-srv6-network-programming]
              Filsfils, C., Garvia, P. C., Leddy, J., Voyer, D.,
              Matsushima, S., and Z. Li, "Segment Routing over IPv6
              (SRv6) Network Programming", Work in Progress, Internet-
              Draft, draft-ietf-spring-srv6-network-programming-28, 29
              December 2020, <https://www.ietf.org/archive/id/draft-
              ietf-spring-srv6-network-programming-28.txt>.

   [I-D.peng-lsr-algorithm-related-adjacency-sid]
              Peng, S., Chen, R., Talaulikar, K., and P. Psenak,
              "Algorithm Related IGP-Adjacency SID Advertisement", Work
              in Progress, Internet-Draft, draft-peng-lsr-algorithm-
              related-adjacency-sid-03, 17 May 2021,
              <https://www.ietf.org/archive/id/draft-peng-lsr-algorithm-
              related-adjacency-sid-03.txt>.

   [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>.

   [RFC8200]  Deering, S. and R. Hinden, "Internet Protocol, Version 6
              (IPv6) Specification", STD 86, RFC 8200,
              DOI 10.17487/RFC8200, July 2017,
              <https://www.rfc-editor.org/info/rfc8200>.

   [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>.

   [RFC8660]  Bashandy, A., Ed., Filsfils, C., Ed., Previdi, S.,
              Decraene, B., Litkowski, S., and R. Shakir, "Segment
              Routing with the MPLS Data Plane", RFC 8660,
              DOI 10.17487/RFC8660, December 2019,
              <https://www.rfc-editor.org/info/rfc8660>.

   [RFC8665]  Psenak, P., Ed., Previdi, S., Ed., Filsfils, C., Gredler,
              H., Shakir, R., Henderickx, W., and J. Tantsura, "OSPF
              Extensions for Segment Routing", RFC 8665,
              DOI 10.17487/RFC8665, December 2019,
              <https://www.rfc-editor.org/info/rfc8665>.





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   [RFC8666]  Psenak, P., Ed. and S. Previdi, Ed., "OSPFv3 Extensions
              for Segment Routing", RFC 8666, DOI 10.17487/RFC8666,
              December 2019, <https://www.rfc-editor.org/info/rfc8666>.

   [RFC8667]  Previdi, S., Ed., Ginsberg, L., Ed., Filsfils, C.,
              Bashandy, A., Gredler, H., and B. Decraene, "IS-IS
              Extensions for Segment Routing", RFC 8667,
              DOI 10.17487/RFC8667, December 2019,
              <https://www.rfc-editor.org/info/rfc8667>.

   [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>.

Authors' Addresses

   Liu Yao
   ZTE Corporation
   China

   Email: liu.yao71@zte.com.cn


   Peng Shaofu
   ZTE Corporation
   China

   Email: peng.shaofu@zte.com.cn






















Yao & Shaofu            Expires 20 February 2022               [Page 12]