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Versions: (draft-gredler-idr-bgp-ls-segment-routing-ext) 00 01 02 03 04 05 06 07 08 09 10 11

Inter-Domain Routing                                     S. Previdi, Ed.
Internet-Draft
Intended status: Standards Track                           K. Talaulikar
Expires: April 13, 2019                                      C. Filsfils
                                                     Cisco Systems, Inc.
                                                              H. Gredler
                                                            RtBrick Inc.
                                                                 M. Chen
                                                     Huawei Technologies
                                                        October 10, 2018


             BGP Link-State extensions for Segment Routing
              draft-ietf-idr-bgp-ls-segment-routing-ext-09

Abstract

   Segment Routing (SR) allows for a flexible definition of end-to-end
   paths by encoding paths as sequences of topological sub-paths, called
   "segments".  These segments are advertised by routing protocols e.g.
   by the link state routing protocols (IS-IS, OSPFv2 and OSPFv3) within
   IGP topologies.

   This draft defines extensions to the BGP Link-state address-family in
   order to carry segment routing information via BGP.

Requirements Language

   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].

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 April 13, 2019.



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Copyright Notice

   Copyright (c) 2018 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 and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as 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  . . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  BGP-LS Extensions for Segment Routing . . . . . . . . . . . .   5
     2.1.  Node Attributes TLVs  . . . . . . . . . . . . . . . . . .   5
       2.1.1.  SID/Label Sub-TLV . . . . . . . . . . . . . . . . . .   6
       2.1.2.  SR-Capabilities TLV . . . . . . . . . . . . . . . . .   7
       2.1.3.  SR-Algorithm TLV  . . . . . . . . . . . . . . . . . .   8
       2.1.4.  SR Local Block TLV  . . . . . . . . . . . . . . . . .   8
       2.1.5.  SRMS Preference TLV . . . . . . . . . . . . . . . . .   9
     2.2.  Link Attribute TLVs . . . . . . . . . . . . . . . . . . .  10
       2.2.1.  Adjacency SID TLV . . . . . . . . . . . . . . . . . .  11
       2.2.2.  LAN Adjacency SID TLV . . . . . . . . . . . . . . . .  12
       2.2.3.  L2 Bundle Member  . . . . . . . . . . . . . . . . . .  13
     2.3.  Prefix Attribute TLVs . . . . . . . . . . . . . . . . . .  14
       2.3.1.  Prefix-SID TLV  . . . . . . . . . . . . . . . . . . .  15
       2.3.2.  Prefix Attribute Flags TLV  . . . . . . . . . . . . .  16
       2.3.3.  Source Router Identifier (Source Router-ID) TLV . . .  17
       2.3.4.  Range TLV . . . . . . . . . . . . . . . . . . . . . .  17
     2.4.  Equivalent IS-IS Segment Routing TLVs/Sub-TLVs  . . . . .  19
     2.5.  Equivalent OSPFv2/OSPFv3 Segment Routing TLVs/Sub-TLVs  .  20
   3.  Implementation Status . . . . . . . . . . . . . . . . . . . .  21
   4.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  21
     4.1.  TLV/Sub-TLV Code Points Summary . . . . . . . . . . . . .  21
   5.  Manageability Considerations  . . . . . . . . . . . . . . . .  22
     5.1.  Operational Considerations  . . . . . . . . . . . . . . .  22
     5.2.  Management Considerations . . . . . . . . . . . . . . . .  22
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .  23
   7.  Contributors  . . . . . . . . . . . . . . . . . . . . . . . .  23
   8.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  23
   9.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  23
     9.1.  Normative References  . . . . . . . . . . . . . . . . . .  23
     9.2.  Informative References  . . . . . . . . . . . . . . . . .  25



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     9.3.  URIs  . . . . . . . . . . . . . . . . . . . . . . . . . .  25
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  27

1.  Introduction

   Segment Routing (SR) allows for a flexible definition of end-to-end
   paths by combining sub-paths called "segments".  A segment can
   represent any instruction, topological or service-based.  A segment
   can have a local semantic to an SR node or global within a domain.
   Within IGP topologies an SR path is encoded as a sequence of
   topological sub-paths, called "IGP segments".  These segments are
   advertised by the link-state routing protocols (IS-IS, OSPFv2 and
   OSPFv3).

   Two types of IGP segments are defined, Prefix segments and Adjacency
   segments.  Prefix segments, by default, represent an ECMP-aware
   shortest-path to a prefix, as per the state of the IGP topology.
   Adjacency segments represent a hop over a specific adjacency between
   two nodes in the IGP.  A prefix segment is typically a multi-hop path
   while an adjacency segment, in most of the cases, is a one-hop path.
   [RFC8402].

   When Segment Routing is enabled in a IGP domain, segments are
   advertised in the form of Segment Identifiers (SIDs).  The IGP link-
   state routing protocols have been extended to advertise SIDs and
   other SR-related information.  IGP extensions are described in: IS-IS
   [I-D.ietf-isis-segment-routing-extensions], OSPFv2
   [I-D.ietf-ospf-segment-routing-extensions] and OSPFv3
   [I-D.ietf-ospf-ospfv3-segment-routing-extensions].  Using these
   extensions, Segment Routing can be enabled within an IGP domain.





















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                           +------------+
                           |  Consumer  |
                           +------------+
                                 ^
                                 |
                                 v
                       +-------------------+
                       |    BGP Speaker    |         +-----------+
                       | (Route-Reflector) |         | Consumer  |
                       +-------------------+         +-----------+
                             ^   ^   ^                       ^
                             |   |   |                       |
             +---------------+   |   +-------------------+   |
             |                   |                       |   |
             v                   v                       v   v
       +-----------+       +-----------+             +-----------+
       |    BGP    |       |    BGP    |             |    BGP    |
       |  Speaker  |       |  Speaker  |    . . .    |  Speaker  |
       +-----------+       +-----------+             +-----------+
             ^                   ^                         ^
             |                   |                         |
            IGP                 IGP                       IGP

                   Figure 1: Link State info collection

   Segment Routing (SR) allows advertisement of single or multi-hop
   paths.  The flooding scope for the IGP extensions for Segment routing
   is IGP area-wide.  Consequently, the contents of a Link State
   Database (LSDB) or a Traffic Engineering Database (TED) has the scope
   of an IGP area and therefore, by using the IGP alone it is not enough
   to construct segments across multiple IGP Area or AS boundaries.

   In order to address the need for applications that require
   topological visibility across IGP areas, or even across Autonomous
   Systems (AS), the BGP-LS address-family/sub-address-family have been
   defined to allow BGP to carry Link-State information.  The BGP
   Network Layer Reachability Information (NLRI) encoding format for
   BGP-LS and a new BGP Path Attribute called the BGP-LS attribute are
   defined in [RFC7752].  The identifying key of each Link-State object,
   namely a node, link, or prefix, is encoded in the NLRI and the
   properties of the object are encoded in the BGP-LS attribute.
   Figure 1 describes a typical deployment scenario.  In each IGP area,
   one or more nodes are configured with BGP-LS.  These BGP speakers
   form an IBGP mesh by connecting to one or more route-reflectors.
   This way, all BGP speakers (specifically the route-reflectors) obtain
   Link-State information from all IGP areas (and from other ASes from
   EBGP peers).  An external component connects to the route-reflector




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   to obtain this information (perhaps moderated by a policy regarding
   what information is or isn't advertised to the external component).

   This document describes extensions to BGP-LS to advertise the SR
   information.  An external component (e.g., a controller) then can
   collect SR information from across an SR domain and construct the
   end-to-end path (with its associated SIDs) that need to be applied to
   an incoming packet to achieve the desired end-to-end forwarding.
   Here the SR domain is defined as a single administrative domain that
   may be comprised of a single AS or multiple ASes under consolidated
   global SID administration.

2.  BGP-LS Extensions for Segment Routing

   This document defines SR extensions to BGP-LS and specifies the TLVs
   and sub-TLVs for advertising SR information.  Section 2.4 and
   Section 2.5 illustrates the equivalent TLVs and sub-TLVs in IS-IS,
   OSPFv2 and OSPFv3 protocols.

   BGP-LS [RFC7752] defines the BGP-LS NLRI that can be a Node NLRI, a
   Link NLRI or a Prefix NLRI.  The corresponding BGP-LS attribute is a
   Node Attribute, a Link Attribute or a Prefix Attribute.  BGP-LS
   [RFC7752] defines the TLVs that map link-state information to BGP-LS
   NLRI and the BGP-LS attribute.  This document adds additional BGP-LS
   attribute TLVs in order to encode SR information.

   Some of the TLVs defined in this document contain fields (e.g. flags)
   whose semantics need to be interpreted accordingly to the respective
   underlying IS-IS, OSPFv2 or OSPFv3 protocol.  The receiver of the
   BGP-LS update for any of the NLRIs MUST check the Protocol-ID of the
   NLRI and refer to the underlying protocol specification in order to
   parse such fields.  The individual field descriptions in the sub-
   sections below point to the relevant underlying protocol
   specifications for such fields.

2.1.  Node Attributes TLVs

   The following Node Attribute TLVs are defined:













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              +-----------------+----------+---------------+
              | Description     | Length   |       Section |
              +-----------------+----------+---------------+
              | SID/Label       | variable | Section 2.1.1 |
              | SR Capabilities | variable | Section 2.1.2 |
              | SR Algorithm    | variable | Section 2.1.3 |
              | SR Local Block  | variable | Section 2.1.4 |
              | SRMS Preference | variable | Section 2.1.5 |
              +-----------------+----------+---------------+

                       Table 1: Node Attribute TLVs

   These TLVs can ONLY be added to the Node Attribute associated with
   the Node NLRI that originates the corresponding underlying IGP TLV/
   sub-TLV described below.

2.1.1.  SID/Label Sub-TLV

   The SID/Label TLV is used as sub-TLV by the SR-Capabilities
   (Section 2.1.2) and SRLB (Section 2.1.4) TLVs and has the following
   format:

    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             |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                      SID/Label (variable)                     |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   where:

      Type: TBD, see Section 4.

      Length: Variable, 3 or 4.

      SID/Label: If length is set to 3, then the 20 rightmost bits
      represent a label (the total TLV size is 7).  If length is set to
      4, then the value represents a 32 bit SID (the total TLV size is
      8).

      The receiving router MUST ignore the SID/Label sub-TLV if the
      length is other then 3 or 4.








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2.1.2.  SR-Capabilities TLV

   The SR-Capabilities TLV is used in order to advertise the node's SR
   Capabilities including its Segment Routing Global Base (SRGB)
   range(s).  In the case of IS-IS, the capabilities also include the
   IPv4 and IPv6 support for SR-MPLS forwarding plane.  This information
   is derived from the protocol specific advertisements.

   o  IS-IS, as defined by the SR-Capabilities sub-TLV in
      [I-D.ietf-isis-segment-routing-extensions].

   o  OSPFv2/OSPFv3, as defined by the SID/Label Range TLV in
      [I-D.ietf-ospf-segment-routing-extensions] and
      [I-D.ietf-ospf-ospfv3-segment-routing-extensions].

   The SR Capabilities TLV has following format:

    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    |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                  Range Size                   |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   //                SID/Label sub-TLV (variable)                 //
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

      Type: TBD, see Section 4.

      Length: Variable.

      Flags: 1 octet of flags as defined in
      [I-D.ietf-isis-segment-routing-extensions].

      Reserved: 1 octet that SHOULD be set to 0 and MUST be ignored on
      receipt.

      One or more entries, each of which have the following format:

         Range Size: 3 octet value indicating the number of labels in
         the range.

         SID/Label sub-TLV (as defined in Section 2.1.1) which encodes
         the first label in the range.



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2.1.3.  SR-Algorithm TLV

   The SR-Algorithm TLV is used in order to advertise the SR Algorithms
   supported by the node.  This information is derived from the protocol
   specific advertisements.

   o  IS-IS, as defined by the SR-Algorithm sub-TLV in
      [I-D.ietf-isis-segment-routing-extensions].

   o  OSPFv2/OSPFv3, as defined by the SR-Algorithm TLV in
      [I-D.ietf-ospf-segment-routing-extensions] and
      [I-D.ietf-ospf-ospfv3-segment-routing-extensions].

   The SR-Algorithm TLV has the following format:

    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             |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |  Algorithm 1  |  Algorithm... |  Algorithm N |                |
   +-                                                             -+
   |                                                               |
   +                                                               +

   where:

      Type: TBD, see Section 4.

      Length: Variable.

      Algorithm: 1 octet identifying the algorithm.

2.1.4.  SR Local Block TLV

   The SR Local Block (SRLB) TLV contains the range(s) of labels the
   node has reserved for local SIDs.  Local SIDs are used, e.g., in IGP
   (IS-IS, OSPF) for Adjacency-SIDs, and may also be allocated by
   components other than IGP protocols.  As an example, an application
   or a controller may instruct a node to allocate a specific local SID.
   Therefore, in order for such applications or controllers to know the
   range of local SIDs available, it is required that the node
   advertises its SRLB.

   This information is derived from the protocol specific
   advertisements.





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   o  IS-IS, as defined by the SR Local Block sub-TLV in
      [I-D.ietf-isis-segment-routing-extensions].

   o  OSPFv2/OSPFv3, as defined by the SR Local Block TLV in
      [I-D.ietf-ospf-segment-routing-extensions] and
      [I-D.ietf-ospf-ospfv3-segment-routing-extensions].

   The SRLB TLV has the following format:

    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    |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                  Range Size                   |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   //                SID/Label sub-TLV (variable)                 //
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

      Type: TBD, see Section 4.

      Length: Variable.

      Flags: 1 octet of flags.  None are defined at this stage.

      Reserved: 1 octet that SHOULD be set to 0 and MUST be ignored on
      receipt.

      One or more entries, each of which have the following format:

         Range Size: 3 octet value indicating the number of labels in
         the range.

         SID/Label sub-TLV (as defined in Section 2.1.1) which encodes
         the first label in the range.

2.1.5.  SRMS Preference TLV

   The Segment Routing Mapping Server (SRMS) Preference TLV is used in
   order to associate a preference with SRMS advertisements from a
   particular source.  [I-D.ietf-spring-segment-routing-ldp-interop]
   specifies the SRMS functionality along with SRMS preference of the
   node advertising the SRMS Prefix-to-SID Mapping ranges.




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   This information is derived from the protocol specific
   advertisements.

   o  IS-IS, as defined by the SRMS Preference sub-TLV in
      [I-D.ietf-isis-segment-routing-extensions].

   o  OSPFv2/OSPFv3, as defined by the SRMS Preference TLV in
      [I-D.ietf-ospf-segment-routing-extensions] and
      [I-D.ietf-ospf-ospfv3-segment-routing-extensions].

   The SRMS Preference TLV has following format:

    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             |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | Preference    |
   +-+-+-+-+-+-+-+-+

      Type: TBD, see Section 4.

      Length: 1.

      Preference: 1 octet.  Unsigned 8 bit SRMS preference.

   The use of the SRMS Preference TLV is defined in
   [I-D.ietf-isis-segment-routing-extensions],
   [I-D.ietf-ospf-segment-routing-extensions] and
   [I-D.ietf-ospf-ospfv3-segment-routing-extensions].

2.2.  Link Attribute TLVs

   The following Link Attribute TLVs are are defined:

   +----------------------------------------+----------+---------------+
   | Description                            |   Length |       Section |
   +----------------------------------------+----------+---------------+
   | Adjacency Segment Identifier (Adj-SID) | variable | Section 2.2.1 |
   | TLV                                    |          |               |
   | LAN Adjacency Segment Identifier (Adj- | variable | Section 2.2.2 |
   | SID) TLV                               |          |               |
   | L2 Bundle Member TLV                   | variable | Section 2.2.3 |
   +----------------------------------------+----------+---------------+

                       Table 2: Link Attribute TLVs





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   These TLVs can ONLY be added to the Link Attribute associated with
   the link whose local node originates the corresponding underlying IGP
   TLV/sub-TLV described below.

   For a LAN, normally a node only announces its adjacency to the IS-IS
   pseudo-node (or the equivalent OSPF Designated and Backup Designated
   Routers)[I-D.ietf-isis-segment-routing-extensions].  The LAN
   Adjacency Segment TLV allows a node to announce adjacencies to all
   other nodes attached to the LAN in a single instance of the BGP-LS
   Link NLRI.  Without this TLV, the corresponding BGP-LS link NLRI
   would need to be originated for each additional adjacency in order to
   advertise the SR TLVs for these neighbor adjacencies.

2.2.1.  Adjacency SID TLV

   The Adjacency SID (Adj-SID) TLV has the following format:

    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         |     Weight    |             Reserved          |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                   SID/Label/Index (variable)                  |
   +---------------------------------------------------------------+

   where:

      Type: TBD, see Section 4.

      Length: Variable, 7 or 8 depending on Label or Index encoding of
      the SID

      Flags. 1 octet field of following flags as defined in
      [I-D.ietf-isis-segment-routing-extensions],
      [I-D.ietf-ospf-segment-routing-extensions] and
      [I-D.ietf-ospf-ospfv3-segment-routing-extensions].

      Weight: Weight used for load-balancing purposes.

      Reserved: 2 octets that SHOULD be set to 0 and MUST be ignored on
      receipt.

      SID/Index/Label: Label or index value depending on the flags
      setting as defined in [I-D.ietf-isis-segment-routing-extensions],
      [I-D.ietf-ospf-segment-routing-extensions] and
      [I-D.ietf-ospf-ospfv3-segment-routing-extensions].



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2.2.2.  LAN Adjacency SID TLV

   The LAN Adjacency SID (LAN-Adj-SID-SID) TLV has the following format:

    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     |     Weight    |            Reserved           |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |             OSPF Neighbor ID / IS-IS System-ID                |
   +                               +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                    SID/Label/Index (variable)                 |
   +---------------------------------------------------------------+

   where:

      Type: TBD, see Section 4.

      Length: Variable.  For IS-IS it would be 13 or 14 depending on
      Label or Index encoding of the SID.  For OSPF it would be 11 or 12
      depending on Label or Index encoding of the SID.

      Flags. 1 octet field of following flags as defined in
      [I-D.ietf-isis-segment-routing-extensions],
      [I-D.ietf-ospf-segment-routing-extensions] and
      [I-D.ietf-ospf-ospfv3-segment-routing-extensions].

      Weight: Weight used for load-balancing purposes.

      Reserved: 2 octets that SHOULD be set to 0 and MUST be ignored on
      receipt.

      SID/Index/Label: Label or index value depending on the flags
      setting as defined in [I-D.ietf-isis-segment-routing-extensions],
      [I-D.ietf-ospf-segment-routing-extensions] and
      [I-D.ietf-ospf-ospfv3-segment-routing-extensions].







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2.2.3.  L2 Bundle Member

   The L2 Bundle Member Attribute TLV identifies an L2 Bundle Member
   link which in turn is associated with a parent L3 link.  The L3 link
   is described by the Link NLRI defined in [RFC7752] and the L2 Bundle
   Member Attribute TLV is associated with the Link NLRI.  The TLV MAY
   include sub-TLVs which describe attributes associated with the bundle
   member.  The identified bundle member represents a unidirectional
   path from the originating router to the neighbor specified in the
   parent L3 Link.  Multiple L2 Bundle Member Attribute TLVs MAY be
   associated with a Link NLRI.

   The L2 Bundle Member Attribute TLV has the following format:

    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               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                     L2 Bundle Member Descriptor               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   //                  Link attribute sub-TLVs(variable)          //
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   where:

      Type: TBD, see Section 4.

      Length: Variable.

      L2 Bundle Member Descriptor: A Link Local Identifier as defined in
      [RFC4202].

   Link attributes for L2 Bundle Member Links are advertised as sub-TLVs
   of the L2Bundle Member Attribute TLV.  The sub-TLVs are identical to
   existing BGP-LS TLVs as identified in the table below.












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   +-----------+----------------------------+--------------------------+
   |  TLV Code | Description                | Reference Document       |
   |   Point   |                            |                          |
   +-----------+----------------------------+--------------------------+
   |    1088   | Administrative group       | [RFC7752]                |
   |           | (color)                    |                          |
   |    1089   | Maximum link bandwidth     | [RFC7752]                |
   |    1090   | Max. reservable link       | [RFC7752]                |
   |           | bandwidth                  |                          |
   |    1091   | Unreserved bandwidth       | [RFC7752]                |
   |    1092   | TE default metric          | [RFC7752]                |
   |    1093   | Link protection type       | [RFC7752]                |
   |    1099   | Adjacency Segment          | Section 2.2.1            |
   |           | Identifier (Adj-SID) TLV   |                          |
   |    1100   | LAN Adjacency Segment      | Section 2.2.2            |
   |           | Identifier (Adj-SID) TLV   |                          |
   |    1104   | Unidirectional link delay  | [I-D.ietf-idr-te-pm-bgp] |
   |    1105   | Min/Max Unidirectional     | [I-D.ietf-idr-te-pm-bgp] |
   |           | link delay                 |                          |
   |    1106   | Min/Max Unidirectional     | [I-D.ietf-idr-te-pm-bgp] |
   |           | link delay                 |                          |
   |    1107   | Unidirectional packet loss | [I-D.ietf-idr-te-pm-bgp] |
   |    1108   | Unidirectional residual    | [I-D.ietf-idr-te-pm-bgp] |
   |           | bandwidth                  |                          |
   |    1109   | Unidirectional available   | [I-D.ietf-idr-te-pm-bgp] |
   |           | bandwidth                  |                          |
   |    1110   | Unidirectional bandwidth   | [I-D.ietf-idr-te-pm-bgp] |
   |           | utilization                |                          |
   +-----------+----------------------------+--------------------------+

               Table 3: L2 Bundle Member Link Attribute TLVs

2.3.  Prefix Attribute TLVs

   The following Prefix Attribute TLVs are defined:

           +------------------------+----------+---------------+
           | Description            |   Length | Section       |
           +------------------------+----------+---------------+
           | Prefix SID             | variable | Section 2.3.1 |
           | Range                  | variable | Section 2.3.4 |
           | Prefix Attribute Flags | variable | Section 2.3.2 |
           | Source Router-ID       | variable | Section 2.3.3 |
           +------------------------+----------+---------------+

                      Table 4: Prefix Attribute TLVs





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   These TLVs can ONLY be added to the Prefix Attribute associated with
   the prefix whose local node originates the corresponding underlying
   IGP TLV/sub-TLV described below.

2.3.1.  Prefix-SID TLV

   The Prefix-SID TLV is used in order to advertise information related
   to a Prefix-SID.  This information is originated in:

   o  IS-IS, as defined by the Prefix-SID TLV in
      [I-D.ietf-isis-segment-routing-extensions].

   o  OSPFv2 and OSPFv3, as defined by the Prefix-SID TLV in
      [I-D.ietf-ospf-segment-routing-extensions] and
      [I-D.ietf-ospf-ospfv3-segment-routing-extensions] respectively.

   The Prefix-SID has the following format:

    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   |           Reserved            |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                       SID/Index/Label (variable)              |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   where:

      Type: TBD, see Section 4.

      Length: Variable, 7 or 8 depending on Label or Index encoding of
      the SID

      Flags: 1 octet value which sould be parsed as:

      *  IS-IS Prefix-SID flags are defined in
         [I-D.ietf-isis-segment-routing-extensions] section 2.1.

      *  OSPFv2 Prefix-SID flags are defined in
         [I-D.ietf-ospf-segment-routing-extensions] section 5.

      *  OSPFv3 Prefix-SID flags are defined in
         [I-D.ietf-ospf-segment-routing-extensions] section 5.

      Algorithm: 1 octet value identify the algorithm.




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      Reserved: 2 octets that SHOULD be set to 0 and MUST be ignored on
      receipt.

      SID/Index/Label:

      *  IS-IS: Label or index value as defined in
         [I-D.ietf-isis-segment-routing-extensions],

      *  OSPFv2: Label or index value as defined in
         [I-D.ietf-ospf-segment-routing-extensions],

      *  OSPFv3: Label or index value as defined in
         [I-D.ietf-ospf-ospfv3-segment-routing-extensions],

2.3.2.  Prefix Attribute Flags TLV

   The Prefix Attribute Flags TLV carries IPv4/IPv6 prefix attribute
   flags information.  These flags are defined for OSPFv2 in [RFC7684],
   for OSPFv3 in [RFC5340] and for IS-IS in [RFC7794].

   The Prefix Attribute Flags TLV has the following format:

    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 (variable)                      //
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   where:

      Type: TBD, see Section 4.

      Length: variable.

      Flags: a variable length flag field (according to the length
      field).  Flags are routing protocol specific and are to be parsed
      as below:

      *  IS-IS flags are defined in [RFC7794]

      *  OSPFv2 flags are defined in [RFC7684]

      *  OSPFv3 flags map to the Prefix Options field defined in
         [RFC7794] and extended via [RFC8362]





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2.3.3.  Source Router Identifier (Source Router-ID) TLV

   The Source Router-ID TLV contains the IPv4 or IPv6 Router-ID of the
   originator of the Prefix.  For IS-IS protocol this is as defined in
   [RFC7794].  The Source Router-ID TLV may be used to carry the OSPF
   Router-ID of the prefix originator.

   The Source Router-ID TLV has the following format:

    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             |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   //                  4 or 6 octet Router-ID                     //
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   where:

      Type: TBD, see Section 4.

      Length: 4 or 16.

      IPv4/IPv6 Address: 4 octet IPv4 address or 16 octet IPv6 address.

2.3.4.  Range TLV

   The range TLV is used in order to advertise a range of prefix-to-SID
   mappings as part of the Segment Routing Mapping Server functionality
   [I-D.ietf-spring-segment-routing-ldp-interop], as defined in the
   respective underlying IGP SR extensions
   [I-D.ietf-ospf-segment-routing-extensions],
   [I-D.ietf-ospf-ospfv3-segment-routing-extensions] and
   [I-D.ietf-isis-segment-routing-extensions].  The Prefix-NLRI to which
   the Range TLV is attached MUST be advertised as a non-routing prefix
   where no IGP metric TLV (TLV 1095) is attached.

   The format of the Range TLV 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     | Reserved      |             Range Size        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   //                          sub-TLVs                           //
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   where:

                        Figure 2: Range TLV format

      Type: TBD, see Section 4.

      Length: variable

      Flags: as defined in [I-D.ietf-ospf-segment-routing-extensions],
      [I-D.ietf-ospf-ospfv3-segment-routing-extensions] and
      [I-D.ietf-isis-segment-routing-extensions].

      Reserved: 1 octet that SHOULD be set to 0 and MUST be ignored on
      receipt.

      Range Size: 2 octets as defined in
      [I-D.ietf-ospf-segment-routing-extensions].

   Within the Range TLV, the prefix-to-SID mappings are advertised using
   sub-TLVs as below:

   Range TLV
      Prefix-SID TLV (used as a sub-TLV in this context)

   where:

   o  The Range TLV is defined in Section 2.3.4.

   o  The Prefix-SID TLV (used as sub-TLV in this context) is defined in
      Section 2.3.1.

2.3.4.1.  Advertisement Procedure for OSPF

   The OSPFv2/OSPFv3 Extended Prefix Range TLV is encoded in the Range
   TLV.  The flags of the Range TLV have the semantic mapped to the
   definition in [I-D.ietf-ospf-segment-routing-extensions] section 4 or
   [I-D.ietf-ospf-ospfv3-segment-routing-extensions] section 4.




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   Then the prefix-to-SID mapping from the OSPF Prefix SID sub-TLV is
   encoded using the BGP-LS Prefix-SID TLV as defined in Section 2.3.1
   with the flags set according to the definition in
   [I-D.ietf-ospf-segment-routing-extensions] section 5 or
   [I-D.ietf-ospf-ospfv3-segment-routing-extensions] section 5.

2.3.4.2.  Advertisement Procedure for IS-IS

   The IS-IS SID/Label Binding TLV, when used to signal mapping server
   label bindings, is encoded in the Range TLV.  The flags of the Range
   TLV have the sematic mapped to the definition in
   [I-D.ietf-isis-segment-routing-extensions] section 2.4.1.

   Then the prefix-to-SID mappings from the IS-IS Prefix SID sub-TLV is
   encoded using the BGP-LS Prefix-SID TLV as defined in Section 2.3.1
   with the flags set according to the definition in
   [I-D.ietf-isis-segment-routing-extensions] section 2.4.4.1.

2.4.  Equivalent IS-IS Segment Routing TLVs/Sub-TLVs

   This section illustrate the IS-IS Segment Routing Extensions TLVs and
   sub-TLVs mapped to the ones defined in this document.

   The following table, illustrates for each BGP-LS TLV, its equivalence
   in IS-IS.

   +---------------------------------------+----------+----------------+
   | Description                           | Length   | IS-IS TLV/sub- |
   |                                       |          | TLV            |
   +---------------------------------------+----------+----------------+
   | SR Capabilities                       | variable | 2 [1]          |
   | SR Algorithm                          | variable | 19 [2]         |
   | SR Local Block                        | variable | 22 [3]         |
   | SRMS Preference                       | 1        | 19 [4]         |
   | Adjacency Segment Identifier (Adj-    | variable | 31 [5]         |
   | SID)                                  |          |                |
   | LAN Adjacency Segment Identifier      | variable | 32 [6]         |
   | (LAN-Adj-SID)                         |          |                |
   | Prefix SID                            | variable | 3 [7]          |
   | Range                                 | variable | 149 [8]        |
   | SID/Label TLV                         | variable | 1 [9]          |
   | Prefix Attribute Flags                | variable | 4 [10]         |
   | Source Router ID                      | variable | 11/12 [11]     |
   | L2 Bundle Member TLV                  | variable | 25 [12]        |
   +---------------------------------------+----------+----------------+

          Table 5: IS-IS Segment Routing Extensions TLVs/Sub-TLVs




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2.5.  Equivalent OSPFv2/OSPFv3 Segment Routing TLVs/Sub-TLVs

   This section illustrate the OSPFv2 and OSPFv3 Segment Routing
   Extensions TLVs and sub-TLVs mapped to the ones defined in this
   document.

   The following table, illustrates for each BGP-LS TLV, its equivalence
   in OSPFv2 and OSPFv3.

   +-------------------------------------+----------+------------------+
   | Description                         | Length   | OSPFv2 TLV/sub-  |
   |                                     |          | TLV              |
   +-------------------------------------+----------+------------------+
   | SR Capabilities                     | variable | 9 [13]           |
   | SR Algorithm                        | variable | 8 [14]           |
   | SR Local Block                      | variable | 14 [15]          |
   | SRMS Preference                     | 1        | 15 [16]          |
   | Adjacency Segment Identifier (Adj-  | variable | 2 [17]           |
   | SID)                                |          |                  |
   | LAN Adjacency Segment Identifier    | variable | 3 [18]           |
   | (Adj-SID)                           |          |                  |
   | Prefix SID                          | variable | 2 [19]           |
   | Range                               | variable | 2 [20]           |
   | SID/Label TLV                       | variable | 1 [21]           |
   | Prefix Attribute Flags              | variable | 4 [22]           |
   +-------------------------------------+----------+------------------+

          Table 6: OSPF Segment Routing Extensions TLVs/Sub-TLVs

   +-------------------------------------+----------+------------------+
   | Description                         | Length   | OSPFv3 TLV/sub-  |
   |                                     |          | TLV              |
   +-------------------------------------+----------+------------------+
   | SR Capabilities                     | variable | 9 [23]           |
   | SR Algorithm                        | variable | 8 [24]           |
   | SR Local Block                      | variable | 14 [25]          |
   | SRMS Preference                     | 1        | 15 [26]          |
   | Adjacency Segment Identifier (Adj-  | variable | 5 [27]           |
   | SID)                                |          |                  |
   | LAN Adjacency Segment Identifier    | variable | 6 [28]           |
   | (Adj-SID)                           |          |                  |
   | Prefix SID                          | variable | 4 [29]           |
   | Range                               | variable | 9 [30]           |
   | SID/Label TLV                       | variable | 7 [31]           |
   | Prefix Attribute Flags              | variable | 4 [32]           |
   +-------------------------------------+----------+------------------+

         Table 7: OSPFv3 Segment Routing Extensions TLVs/Sub-TLVs



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3.  Implementation Status

   Note to RFC Editor: Please remove this section prior to publication,
   as well as the reference to RFC 7942.

   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
   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".

   Several early implementations exist and will be reported in detail in
   a forthcoming version of this document.  For purposes of early
   interoperability testing, when no FCFS code point was available,
   implementations have made use of the values described in Table 8.

   It will ease implementation interoperability and deployment if the
   value could be preserved also due to the large amount of codepoints
   this draft requires.  However, when IANA-assigned values are
   available, implementations will be updated to use them.

4.  IANA Considerations

   This document requests assigning code-points from the registry "BGP-
   LS Node Descriptor, Link Descriptor, Prefix Descriptor, and Attribute
   TLVs" based on table Table 8.  The column "IS-IS TLV/Sub-TLV" defined
   in the registry does not require any value and should be left empty.

4.1.  TLV/Sub-TLV Code Points Summary

   This section contains the global table of all TLVs/sub-TLVs defined
   in this document.





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   +-------------+-------------------------------------+---------------+
   |   TLV Code  | Description                         |     Reference |
   |    Point    |                                     |               |
   +-------------+-------------------------------------+---------------+
   |     1034    | SR Capabilities                     | Section 2.1.2 |
   |     1035    | SR Algorithm                        | Section 2.1.3 |
   |     1036    | SR Local Block                      | Section 2.1.4 |
   |     1037    | SRMS Preference                     | Section 2.1.5 |
   |     1099    | Adjacency Segment Identifier (Adj-  | Section 2.2.1 |
   |             | SID) TLV                            |               |
   |     1100    | LAN Adjacency Segment Identifier    | Section 2.2.2 |
   |             | (Adj-SID) TLV                       |               |
   |     1158    | Prefix SID                          | Section 2.3.1 |
   |     1159    | Range                               | Section 2.3.4 |
   |     1161    | SID/Label TLV                       | Section 2.1.1 |
   |     1170    | Prefix Attribute Flags              | Section 2.3.2 |
   |     1171    | Source Router-ID                    | Section 2.3.3 |
   |     1172    | L2 Bundle Member TLV                | Section 2.2.3 |
   +-------------+-------------------------------------+---------------+

             Table 8: Summary Table of TLV/Sub-TLV Codepoints

5.  Manageability Considerations

   This section is structured as recommended in [RFC5706].

   The new protocol extensions introduced in this document augment the
   existing IGP topology information that was distributed via [RFC7752].
   Procedures and protocol extensions defined in this document do not
   affect the BGP protocol operations and management other than as
   discussed in the Manageability Considerations section of [RFC7752].
   Specifically, the malformed NLRIs attribute tests for syntactic
   checks in the Fault Management section of [RFC7752] now encompass the
   new TLVs for the BGP-LS NLRI in this document.  The semantic or
   content checking for the TLVs specified in this document and their
   association with the BGP-LS NLRI types or their BGP-LS Attribute is
   left to the consumer of the BGP-LS information (e.g. an application
   or a controller) and not the BGP protocol.

5.1.  Operational Considerations

   No additional operation considerations are defined in this document.

5.2.  Management Considerations

   No additional management considerations are defined in this document.





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6.  Security Considerations

   The new protocol extensions introduced in this document augment the
   existing IGP topology information that was distributed via [RFC7752].
   Procedures and protocol extensions defined in this document do not
   affect the BGP security model other than as discussed in the Security
   Considerations section of [RFC7752].

7.  Contributors

   The following people have substantially contributed to the editing of
   this document:

   Peter Psenak
   Cisco Systems
   Email: ppsenak@cisco.com

   Les Ginsberg
   Cisco Systems
   Email: ginsberg@cisco.com

   Acee Lindem
   Cisco Systems
   Email: acee@cisco.com

   Saikat Ray
   Individual
   Email: raysaikat@gmail.com

   Jeff Tantsura
   Nuage Networks
   Email: jefftant.ietf@gmail.com

8.  Acknowledgements

   The authors would like to thank Jeffrey Haas and Aijun Wang for their
   review of this document and their comments.

9.  References

9.1.  Normative References

   [I-D.ietf-idr-te-pm-bgp]
              Ginsberg, L., Previdi, S., Wu, Q., Tantsura, J., and C.
              Filsfils, "BGP-LS Advertisement of IGP Traffic Engineering
              Performance Metric Extensions", draft-ietf-idr-te-pm-
              bgp-13 (work in progress), October 2018.




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   [I-D.ietf-isis-segment-routing-extensions]
              Previdi, S., Ginsberg, L., Filsfils, C., Bashandy, A.,
              Gredler, H., Litkowski, S., Decraene, B., and J. Tantsura,
              "IS-IS Extensions for Segment Routing", draft-ietf-isis-
              segment-routing-extensions-19 (work in progress), July
              2018.

   [I-D.ietf-ospf-ospfv3-segment-routing-extensions]
              Psenak, P., Filsfils, C., Previdi, S., Gredler, H.,
              Shakir, R., Henderickx, W., and J. Tantsura, "OSPFv3
              Extensions for Segment Routing", draft-ietf-ospf-ospfv3-
              segment-routing-extensions-15 (work in progress), August
              2018.

   [I-D.ietf-ospf-segment-routing-extensions]
              Psenak, P., Previdi, S., Filsfils, C., Gredler, H.,
              Shakir, R., Henderickx, W., and J. Tantsura, "OSPF
              Extensions for Segment Routing", draft-ietf-ospf-segment-
              routing-extensions-25 (work in progress), April 2018.

   [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>.

   [RFC4202]  Kompella, K., Ed. and Y. Rekhter, Ed., "Routing Extensions
              in Support of Generalized Multi-Protocol Label Switching
              (GMPLS)", RFC 4202, DOI 10.17487/RFC4202, October 2005,
              <https://www.rfc-editor.org/info/rfc4202>.

   [RFC5340]  Coltun, R., Ferguson, D., Moy, J., and A. Lindem, "OSPF
              for IPv6", RFC 5340, DOI 10.17487/RFC5340, July 2008,
              <https://www.rfc-editor.org/info/rfc5340>.

   [RFC7684]  Psenak, P., Gredler, H., Shakir, R., Henderickx, W.,
              Tantsura, J., and A. Lindem, "OSPFv2 Prefix/Link Attribute
              Advertisement", RFC 7684, DOI 10.17487/RFC7684, November
              2015, <https://www.rfc-editor.org/info/rfc7684>.

   [RFC7752]  Gredler, H., Ed., Medved, J., Previdi, S., Farrel, A., and
              S. Ray, "North-Bound Distribution of Link-State and
              Traffic Engineering (TE) Information Using BGP", RFC 7752,
              DOI 10.17487/RFC7752, March 2016,
              <https://www.rfc-editor.org/info/rfc7752>.







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   [RFC7794]  Ginsberg, L., Ed., Decraene, B., Previdi, S., Xu, X., and
              U. Chunduri, "IS-IS Prefix Attributes for Extended IPv4
              and IPv6 Reachability", RFC 7794, DOI 10.17487/RFC7794,
              March 2016, <https://www.rfc-editor.org/info/rfc7794>.

   [RFC8362]  Lindem, A., Roy, A., Goethals, D., Reddy Vallem, V., and
              F. Baker, "OSPFv3 Link State Advertisement (LSA)
              Extensibility", RFC 8362, DOI 10.17487/RFC8362, April
              2018, <https://www.rfc-editor.org/info/rfc8362>.

9.2.  Informative References

   [I-D.ietf-spring-segment-routing-ldp-interop]
              Bashandy, A., Filsfils, C., Previdi, S., Decraene, B., and
              S. Litkowski, "Segment Routing interworking with LDP",
              draft-ietf-spring-segment-routing-ldp-interop-15 (work in
              progress), September 2018.

   [RFC5706]  Harrington, D., "Guidelines for Considering Operations and
              Management of New Protocols and Protocol Extensions",
              RFC 5706, DOI 10.17487/RFC5706, November 2009,
              <https://www.rfc-editor.org/info/rfc5706>.

   [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>.

   [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>.

9.3.  URIs

   [1] http://tools.ietf.org/html/draft-ietf-isis-segment-routing-
       extensions-16#section-3.1

   [2] http://tools.ietf.org/html/draft-ietf-isis-segment-routing-
       extensions-16#section-3.2

   [3] http://tools.ietf.org/html/draft-ietf-isis-segment-routing-
       extensions-16#section-3.3

   [4] http://tools.ietf.org/html/draft-ietf-isis-segment-routing-
       extensions-05#section-3.2





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   [5] http://tools.ietf.org/html/draft-ietf-isis-segment-routing-
       extensions-16#section-2.2.1

   [6] http://tools.ietf.org/html/draft-ietf-isis-segment-routing-
       extensions-16#section-2.2.2

   [7] http://tools.ietf.org/html/draft-ietf-isis-segment-routing-
       extensions-16#section-2.1

   [8] http://tools.ietf.org/html/draft-ietf-isis-segment-routing-
       extensions-16#section-2.4

   [9] http://tools.ietf.org/html/draft-ietf-isis-segment-routing-
       extensions-16#section-2.3

   [10] http://tools.ietf.org/html/RFC7794

   [11] http://tools.ietf.org/html/RFC7794

   [12] http://tools.ietf.org/html/draft-ietf-isis-l2bundles-07

   [13] http://tools.ietf.org/html/draft-ietf-ospf-segment-routing-
        extensions-25#section-3.2

   [14] http://tools.ietf.org/html/draft-ietf-ospf-segment-routing-
        extensions-25#section-3.1

   [15] http://tools.ietf.org/html/draft-ietf-ospf-segment-routing-
        extensions-25#section-3.3

   [16] http://tools.ietf.org/html/draft-ietf-ospf-segment-routing-
        extensions-25#section-3.4

   [17] http://tools.ietf.org/html/draft-ietf-ospf-segment-routing-
        extensions-25#section-6.1

   [18] http://tools.ietf.org/html/draft-ietf-ospf-segment-routing-
        extensions-25#section-6.2

   [19] http://tools.ietf.org/html/draft-ietf-ospf-segment-routing-
        extensions-25#section-5

   [20] http://tools.ietf.org/html/draft-ietf-ospf-segment-routing-
        extensions-25#section-4

   [21] http://tools.ietf.org/html/draft-ietf-ospf-segment-routing-
        extensions-25#section-2.1




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   [22] http://tools.ietf.org/html/RFC7684#section-2.1

   [23] http://tools.ietf.org/html/draft-ietf-ospf-ospfv3-segment-
        routing-extensions-12#section-3.2

   [24] http://tools.ietf.org/html/draft-ietf-ospf-ospfv3-segment-
        routing-extensions-12#section-3.1

   [25] http://tools.ietf.org/html/draft-ietf-ospf-ospfv3-segment-
        routing-extensions-12#section-3.3

   [26] http://tools.ietf.org/html/draft-ietf-ospf-ospfv3-segment-
        routing-extensions-12#section-3.4

   [27] http://tools.ietf.org/html/draft-ietf-ospf-ospfv3-segment-
        routing-extensions-12#section-6.1

   [28] http://tools.ietf.org/html/draft-ietf-ospf-ospfv3-segment-
        routing-extensions-12#section-6.2

   [29] http://tools.ietf.org/html/draft-ietf-ospf-ospfv3-segment-
        routing-extensions-12#section-5

   [30] http://tools.ietf.org/html/draft-ietf-ospf-ospfv3-segment-
        routing-extensions-12#section-4

   [31] http://tools.ietf.org/html/draft-ietf-ospf-ospfv3-segment-
        routing-extensions-12#section-2.1

   [32] http://tools.ietf.org/html/RFC8362#section-3.1

Authors' Addresses

   Stefano Previdi (editor)
   Via Del Serafico, 200
   Rome  00142
   Italy

   Email: stefano@previdi.net


   Ketan Talaulikar
   Cisco Systems, Inc.
   S.No. 154/6, Phase I, Hinjawadi
   Pune  411 057
   India

   Email: ketant@cisco.com



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   Clarence Filsfils
   Cisco Systems, Inc.
   Brussels
   Belgium

   Email: cfilsfil@cisco.com


   Hannes Gredler
   RtBrick Inc.

   Email: hannes@rtbrick.com


   Mach(Guoyi) Chen
   Huawei Technologies
   Huawei Building, No. 156 Beiqing Rd.
   Beijing  100095
   China

   Email: mach.chen@huawei.com






























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