LSR Working Group                                             Louis Chan
   INTERNET-DRAFT                                               Krzysztof Szarkowicz
   Intended status: Standard Track                               Juniper Networks
   Expires: Sep 9, 2023                                          Mar 10, 2023
   
   
                 IGP extensions for Advertising Offset for Flex-Algorithm
                         draft-chan-lsr-igp-adv-offset-02.txt
   
   
   Abstract
   
      This document describes the IGP extensions to provide predictable Adjacency-SIDs
      per Flex-Algorithm [FLEXALGO] in segment routing.
   
      We propose some methods to allow the advertisement of additional TLV in IGP so that
      the Flex-Algorithm specific Adjacency-SIDs could be automatically derived.
   
      With the proposed method, the size of advertisement on per node per link basis is
      greatly reduced. Each participating router would derive the required labels
      automatically.
   
      Extensions for offset to derive Flex-Algorithm Prefix-SID is also included in the
      document.
   
   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
      http://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 Sep 9, 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 (http://trustee.ietf.org/license-info) in effect on the date of
      publication of this document.  Please review these documents carefully, as they
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      Components extracted from this document must include Simplified BSD License text as
   
   
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      described in Section 4.e of the Trust Legal Provisions and are provided without
      warranty as described in the Simplified BSD License.
   
   
   
   Table of Contents
   
   
      1. Introduction ............................................... 2
      2. Conventions used in this document .......................... 2
      3. Virtual Flex-Algorithm ..................................... 3
      4. ISIS extension ............................................. 3
         4.1. Algorithm Offset for Adj-SID .......................... 3
         4.2. Algorithm Offset for LAN based Adj-SID ................ 4
         4.3. Algorithm Offset for Prefix SID ....................... 5
      5. Compatibility .............................................. 7
      6. OSPF extension ............................................. 8
         6.1. Algorithm Offset for Adj-SID .......................... 8
         6.2. Algorithm Offset for LAN based Adj-SID ................ 9
         6.3. Algorithm Offset for Prefix SID ...................... 10
      7. Security Consideration .................................... 11
      8. References ................................................ 11
         8.1. Normative References ................................. 11
         8.2. Informative References ............................... 12
      9. Acknowledgments ........................................... 12
   
   1. Introduction
   
   
      The draft proposes methods for routers to announce Flex-Algorithm specific
      Adjacency-SID with minimal advertisement in IGP. When the other routers need a SR
      policy (aka SR-TE) or TI-LFA path, the Flex-Algorithm specific Adjacency-SID would
      be taken into the path label construction.
   
      Hence, the top most label, either node or link related, in a SR policy stack would
      be used to identify a certain Flex-Algo with full identification.
   
      In the same draft, Virtual Flex-Algorithm concept is introduced.
   
   
   
   2. Conventions used in this document
   
      The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD",
      "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be
      interpreted as described in RFC 2119 [RFC2119].
   
      In this document, these words will appear with that interpretation only when in ALL
      CAPS. Lower case uses of these words are not to be interpreted as carrying
      significance described in RFC 2119.
   
   
   
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   3. Virtual Flex-Algorithm
   
      Here in this draft, Virtual Flex-Alogrithm (VFA) is introduced. There could be
      additional virtual topology which would like to share the same Flex-Algo topology
      with same metrics and constraints, and VFA would need different Prefix-SID and Adj-
      SID for identification in the forwarding plane.
   
      It would save resource to recalculate the shared topology for different VFA.
   
      The relationship between VFA and its related Flex-Algorithm could be similar to
      VLAN and port. Or, they could be in parallel relationship.
   
      VFA would be represented in 32 bits with the minimum value of 256.
   
   4. ISIS extension
   
      With reference to RFC8667, the information could be advertised in SR-Capabilities
      sub-TLV in Section 3.
   
   4.1. Algorithm Offset for Adj-SID
   
   
       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       |    Algorithm  |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                   Virtual Flex-Algorithm                      |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |   SID/Label   |      Base offset/Index offset (variable)      ~
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      ~           Flags/ Algo/ VFA/ Base offset/ Index offset                                                                ~
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   
      where:
   
      Type:           TDB
   
      Length:          variable; multiple advertisements
   
      Flags:                1 octet field of the following flags:
   
                            0 1 2 3 4 5 6 7
                           +-+-+-+-+-+-+-+-+
                           | |B|V|L|       |
                           +-+-+-+-+-+-+-+-+
   
                     where:
   
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              B-Flag:  Backup Flag.  If set, the Adj-SID is eligible
                             for protection (e.g., using IP Fast Reroute
                             (IPFRR) or MPLS Fast Reroute (MPLS-FRR)) as
                             described in [RFC8402].
   
                     V-Flag:  Value Flag.  If set, then it carries
                              a label value. If not set, it is an index value.
   
                     L-Flag:  Local Flag.  Always set to 1
   
   
      Algorithm:              1 octet
                              Flex-Algo value is between 128 and 255.
   
      Virtual Flex-Algorithm  4 octets
                              Value 0 means that it is not VFA
                              Value >=256 means VFA identification number, and the base
                              topology is denoted by Algorithm
                              Value 128 to 255 are invalid
   
      Base Offset:        3 octets
                    Local label base for Adjacency-SIDs for given Flex-
                    Algorithm. The derived Adjacency-SID is the sum of the base
                              offset and the Algo 0 label
   
      Index Offset:          4 octets
                             If Adjacency-SID is advertised as index, this provides an
                             offset index value. The new label is sum of (SRGB base +
                             index + index offset)
   
      The format of Base Offset and Index Offset is the same as RFC8667. The choice of
      advertising Base Offset or Index Offset must match the advertisement of original
      Adjacency-SID method from the same router.
   
   4.2. Algorithm Offset for LAN based Adj-SID
   
   
          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    |   Algorithm   |
         +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
         |                   Virtual Flex-Algorithm                      |
         +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
         |                  Neighbor System-ID (ID length octets)        |
         +                               +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
         |                               |
         +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
         +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
         |        SID/Label Base Offset/Index Offset (variable)          ~
         +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
         +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
         ~ Flags/ Algo/VFA/NB Sys-ID/ SID/Label/Index Offset (variable)  ~
         +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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      where:
   
      Type:           TDB
   
      Length:          variable; multiple advertisements
   
      Flags:                 1 octet field of the following flags:
   
                            0 1 2 3 4 5 6 7
                           +-+-+-+-+-+-+-+-+
                           | |B|V|L|       |
                           +-+-+-+-+-+-+-+-+
   
                     where:
   
              B-Flag:  Backup Flag.  If set, the Adj-SID is eligible
                              for protection (e.g., using IP Fast Reroute
                              (IPFRR) or MPLS Fast Reroute (MPLS-FRR)) as
                              described in [RFC8402].
   
                     V-Flag:  Value Flag.  If set, then it carries
                              a label value. If not set, it is an index value.
   
                     L-Flag:  Local Flag.  Always set to 1
   
   
      Algorithm:              1 octet. Same as Section 4.1
   
      Virtual Flex-Algorithm  4 octets. Same as Section 4.1
   
      Neighbor System-ID:     IS-IS System-ID of length "ID Length" as
                              defined in [ISO10589].
   
      Base Offset:            3 octets. Same as Section 4.1
   
      Index Offset:           4 octets. Same as Section 4.1
   
   
   4.3. Algorithm Offset for Prefix SID
   
      Prefix-SID for Algorithm could also be generated by adding an index offset value or
      a base offset for label.
   
   
   
   
   
   
   
   
   
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      This advertisement is an sub-TLV in RFC8667 Section 2.
   
       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       |    Algorithm  |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                   Virtual Flex-Algorithm                      |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |        SID/Label Base offset/ Index offset                    ~
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      ~      Flags/ Algorithm/ VFA/ Base Offset/ Index offset         ~
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   
   
   
      Type:           TDB
   
      Length:          variable
   
      Flags:                 1 octet field of the following flags:
   
                            0 1 2 3 4 5 6 7
                           +-+-+-+-+-+-+-+-+
                           |R|N|   |V|L|   |
                           +-+-+-+-+-+-+-+-+
   
                     where:
   
                     R-Flag:  Re-advertisement Flag.  If set, then the prefix
                              to which this Prefix-SID is attached has been
                              propagated by the router from either another
                              level (i.e., from Level-1 to Level-2 or the
                              opposite) or redistribution (e.g., from another
                              protocol).
   
                     N-Flag:  Node-SID Flag.  If set, then the Prefix-SID
                              refers to the router identified by the prefix.
                              Typically, the N-Flag is set on Prefix-SIDs that
                              are attached to a router loopback address.  The
                              N-Flag is set when the Prefix-SID is a Node-SID
                              as described in [RFC8402].
   
   
                     V-Flag:  Value Flag.  If set, then it carries
                              a label value. If not set, it is an index value.
   
                     L-Flag:  Local Flag.  Always set to 0
   
      Algorithm:              1 octet
                              Flex-Algo value is between 128 and 255
   
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      Virtual Flex-Algorithm  4 octets
                              Value 0 means that it is not VFA
                              Value >=256 means VFA identification number, and the base
                              topology is denoted by Algorithm
                              Value 128 to 255 are invalid
   
   
      Base offset:            3 octets
                              Label base for Prefix-SIDs for given Algorithm
                              The derived Prefix-SID is the sum of the base
                              Offset and the Algo 0 label
   
      Index Offset:           4 octets
                              Index offset counting from Algo 0
                              The new label for Prefix is sum of (SRGB base +
                              index + index offset)
   
      The format of Base offset and Index Offset is the same as RFC8667. The choice of
      advertising Base Offset or Index Offset MUST match the advertisement of original
      Prefix-SID method from the same router.
   
   5. Compatibility
   
      For nodes that do not support Algorithm Offset for Adj-SID extension, the label
      stack could use normal Adj-SID, providing that the node still support Flex-Algo
      Prefix SID.
   
      For TI-LFA, there would be two modes of operation - loose or strict. For strict
      mode, all Adj-SID involved in TI-LFA candidate path must be derived with offset
      method.
   
      For loose mode, Adj-SID in the TI-LFA candidate path could be a mix of Adj-SID's
      with and without offset. This allows backward compatibility with routers which only
      support Flex-Algo.
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
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   6. OSPF extension
   
      The following TLVs are advertised in the Router Information Opaque LSA (defined in
      [RFC7770]).  these TLVs are applicable to both OSPFv2 and OSPFv3.
   
   6.1. Algorithm Offset for Adj-SID
   
          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     |    Reserved   |   MT-ID       |  Weight       |
         +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
         |   Algorithm   |
         +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
         |                   Virtual Flex-Algorithm                      |
         +---------------------------------------------------------------+
         |          SID/Label Offset/Index Offset (variable)             ~
         +---------------------------------------------------------------+
         ~  Flags/R/MT-ID/Algo/Weight/SID/Label/Index Offset(variable)   ~
         +---------------------------------------------------------------+
   
   
       where:
   
            Type:  TBD
   
            Length:  Variable
   
            Flags:  Single-octet field containing the following flags:
   
                   0 1 2 3 4 5 6 7
                  +-+-+-+-+-+-+-+-+
                  |B|V|L|         |
                  +-+-+-+-+-+-+-+-+
   
               where:
   
              B-Flag:  Backup Flag.  If set, the Adj-SID is eligible
                             for protection (e.g., using IP Fast Reroute
                             (IPFRR) or MPLS Fast Reroute (MPLS-FRR)) as
                             described in [RFC8402].
   
                     V-Flag:  Value Flag.  If set, then it carries
                              a label value. If not set, it is an index value.
   
                     L-Flag:  Local Flag.  Always set to 1
   
   
                 Other bits:  Reserved.  These MUST be zero when sent and are
                              ignored when received.
   
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             MT-ID:          Multi-Topology ID (as defined in [RFC4915]
   
            Weight:          Weight used for load-balancing purposes.  The use of the
                             weight is defined in [RFC8402].
   
   
         Algorithm:           1 octets
                              Flex-Algo value is between 128 and 255.
   
     Virtual Flex-Algorithm:  4 octets
                              Value 0 means that it is not VFA
                              Value >=256 means VFA identification number, and the base
                              topology is denoted by Algorithm
                              Value 128 to 255 are invalid
   
   
       Base Offset:           3 octets
                              Local label base for Adjacency-SIDs for given Flex-
                              Algorithm. The derived Adjacency-SID is the sum of the base
                              offset and the Algo 0 label
   
      Index Offset:           4 octets
                              If Adjacency-SID is advertised as index, this provides an
                              offset index value. The new label is sum of (SRGB base +
                              index + index offset)
   
      The format of Base Offset and Index Offset is the same as RFC8665 or RFC8666. The
      choice of advertising Base Offset or Index Offset must match the advertisement of
      original Adjacency-SID method from the same router.
   
   
   
   6.2. Algorithm Offset for LAN based Adj-SID
   
          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     |    Reserved   |     MT-ID     |    Weight     |
         +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
         |   Algorithm   |
         +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
         |                   Virtual Flex-Algorithm                      |
         +---------------------------------------------------------------+
         |                        Neighbor ID                            |
         +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
         |          SID/Label Offset/Index Offset (variable)             ~
         +---------------------------------------------------------------+
         ~ Flags/R/MT-ID/Weight/Algo/NHR ID/S/Lab/Index Offset(variable) ~
         +---------------------------------------------------------------+
   
      where:
   
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            Type:  TBD
   
            Length:  Variable
   
                     Flags:  Same as 6.1
   
                  Reserved:  Same as 6.1
   
             MT-ID:          Same as 6.1
   
            Weight:          Same as 6.1
   
         Algorithm:          Same as 6.1
   
      Virtual Flex-Algorithm: Same as 6.1
   
       Neighbor ID:          The Router ID of the neighbor for which the LAN
                             Adjacency SID is advertised
   
       Base offset:          Same as 6.1
      Index Offset:          Same as 6.1
   
   
   
   
   6.3. Algorithm Offset for Prefix SID
   
          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    |   Reserved    |      MT-ID    |    Algorithm  |
         +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
         |                   Virtual Flex-Algorithm                      |
         +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
         |          SID/Index Offset/Label Offset(variable)              ~
         +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
         ~     Flags/R/MT-ID/Algo/SID/Index/Label Offset(variable)       ~
         +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   
   
         where:
   
            Type:  TDB
   
            Length:  Variable
   
            Flags:  Single-octet field.  The following flags are defined:
   
                    0  1  2  3  4  5  6  7
                  +--+--+--+--+--+--+--+--+
                  |  |  |  |E |V |L |  |  |
                  +--+--+--+--+--+--+--+--+
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                     E-Flag:  Explicit Null Flag.  If set, any upstream neighbor
                              of the Prefix-SID originator MUST replace the Prefix-SID
                              with the Explicit NULL label (0 for IPv4) before
                              forwarding the packet.
   
                     V-Flag:  Value Flag.  If set, then it carries
                              a label value. If not set, it is an index value.
   
                     L-Flag:  Local Flag.  Always set to 0
   
                 Other bits:  Reserved.  These MUST be zero when sent and are
                              ignored when received.
   
   
            MT-ID:            Multi-Topology ID (as defined in [RFC4915])
   
   
        Algorithm:            1 octet
                              Flex-Algo value is between 128 and 255
   
     Virtual Flex-Algorithm:  4 octets
                              Value 0 means that it is not VFA
                              Value >=256 means VFA identification number, and the base
                              topology is denoted by Algorithm
                              Value 128 to 255 are invalid
   
       Base offset:           3 octets
                              Label base for Prefix-SIDs for given Algorithm
                              The derived Prefix-SID is the sum of the base
                              Offset and the Algo 0 label
   
      Index Offset:           4 octets
                              Index offset counting from Algo 0
                              The new label for Prefix is sum of (SRGB base +
                              index + index offset)
   
      The format of Base offset and Index Offset is the same as RFC8665 or RFC8666. The
      choice of advertising Base Offset or Index Offset MUST match the advertisement of
      original Prefix-SID method from the same router.
   
   7. Security Consideration
   
      TBD
   
   8. References
   
   8.1. Normative References
   
      [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels",
              BCP 14, RFC 2119, March 1997.
   
   
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   8.2. Informative References
   
   
      [RFC8665]     Psenak, P., Ed., Previdi, S., Ed., Filfils, 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>.
   
      [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>.
   
   
       [TI-LFA]    Litkowski, S., Bashandy, A., Filsfils, C., Francois, P.,
                    Decraene, B., and D. Voyer, "Topology Independent Fast
                    Reroute using Segment Routing",
              <https://datatracker.ietf.org/doc/html/draft-ietf-rtgwg-segment-
                    routing-ti-lfa>
   
      [FLEXAGLO]    S. Hegde, P. Psenak and etc, IGP Flexible Algorithm
                 https://datatracker.ietf.org/doc/draft-ietf-lsr-flex-algo
   
   
       [ISO10589]   International Organization for Standardization,
                    "Information technology -- Telecommunications and
                    information exchange between systems -- Intermediate
                    system to Intermediate system intra-domain routeing
                    information exchange protocol for use in conjunction with
                    the protocol for providing the connectionless-mode network
                    service (ISO 8473)", ISO/IEC 10589:2002, Second Edition,
                    November 2002.
   
   
   
   9. Acknowledgments
   
   
           The following people have contributed to this document:
               Shraddha Hegde, Juniper Networks
   
   
   
        Authors' Address
   
        Louis Chan (Editor)
           Juniper Networks Group (Hong Kong) Limited
           Suites 3001-7
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           30th Floor Tower 2
           Times Square
           1 Matheson Street
           Causeway Bay
           Hong Kong
   
           Phone: +852-38562100
           Email: louisc@juniper.net
   
   
        Krzysztof Grzegorz Szarkowicz
           Juniper Networks
           Parkring 10
           A-1010 Wien
           Austria
   
           Phone: +49 89 203012127
           Email: kszarkowicz@juniper.net
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
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