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Versions: 00 01 02

Inter-Domain Routing                                       K. Talaulikar
Internet-Draft                                               C. Filsfils
Intended status: Standards Track                                K. Swamy
Expires: September 10, 2019                                Cisco Systems
                                                                S. Zandi
                                                                G. Dawra
                                                                LinkedIn
                                                              M. Durrani
                                                                 Equinix
                                                           March 9, 2019


             BGP Link-State Extensions for BGP-only Fabric
               draft-ketant-idr-bgp-ls-bgp-only-fabric-02

Abstract

   BGP is used as the only routing protocol in some networks today.  In
   such networks, it is useful to get a detailed view of the nodes and
   underlying links in the topology along with their attributes similar
   to one available when using link state routing protocols.  Such a
   view of a BGP-only fabric enables use cases like traffic engineering
   and forwarding of services along paths other than the BGP best path
   selection.

   This document defines extensions to the BGP Link-state address-family
   (BGP-LS) and the procedures for advertisement of the topology in a
   BGP-only network.  It also describes a specific use-case for traffic
   engineering based on Segment Routing.

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



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   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 September 10, 2019.

Copyright Notice

   Copyright (c) 2019 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 Routing in the Fabric . . . . . . . . . . . . . . . . . .   3
   3.  Topology Collection Mechanism . . . . . . . . . . . . . . . .   4
     3.1.  Peering Models  . . . . . . . . . . . . . . . . . . . . .   5
   4.  Advertising BGP-only Network Topology . . . . . . . . . . . .   6
     4.1.  Node Advertisements . . . . . . . . . . . . . . . . . . .   6
     4.2.  Link Advertisements . . . . . . . . . . . . . . . . . . .   7
     4.3.  Prefix Advertisements . . . . . . . . . . . . . . . . . .  10
     4.4.  TE Policy Advertisements  . . . . . . . . . . . . . . . .  12
   5.  Procedures  . . . . . . . . . . . . . . . . . . . . . . . . .  13
     5.1.  Advertisement of Router's Node Attributes . . . . . . . .  13
     5.2.  Advertisement of Router's Local Links Attributes  . . . .  15
     5.3.  Advertisement of Router's Prefix Attributes . . . . . . .  17
     5.4.  Advertisement of Router's TE Policy Attributes  . . . . .  17
   6.  Usage of BGP Topology . . . . . . . . . . . . . . . . . . . .  18
     6.1.  Topology View for Monitoring  . . . . . . . . . . . . . .  18
     6.2.  SR-TE in BGP Networks . . . . . . . . . . . . . . . . . .  18
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  20
   8.  Manageability Considerations  . . . . . . . . . . . . . . . .  21
     8.1.  Operational Considerations  . . . . . . . . . . . . . . .  21
       8.1.1.  Operations  . . . . . . . . . . . . . . . . . . . . .  21
   9.  Security Considerations . . . . . . . . . . . . . . . . . . .  21
   10. Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  21
   11. References  . . . . . . . . . . . . . . . . . . . . . . . . .  21
     11.1.  Normative References . . . . . . . . . . . . . . . . . .  21
     11.2.  Informative References . . . . . . . . . . . . . . . . .  23



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   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  25

1.  Introduction

   Network operators are going for a BGP-only routing protocol for
   certain networks like Massively Scaled Data Centers (MSDCs).
   [RFC7938] describes the requirement, design and operational aspects
   for use of BGP as the only routing protocol in MSDCs.  The underlying
   link and topology information between BGP routers is hidden or
   abstracted in this design from the underlay routing for improving
   scalability and stability in a large scale network.  On the flip
   side, there is no detailed topology view similar to one available in
   form of the Traffic Engineering (TE) Database (TED) when running link
   state routing protocols like OSPF [RFC2328] with extensions specified
   in [RFC3630].

   BGP Link-State (BGP-LS)[RFC7752] enables advertisement of a link
   state topology via BGP that can be consumed by a controller or in
   general any software component to get a complete topology view of the
   network.  BGP-LS extensions for advertisement of a BGP topology for
   the Egress Peer Engineering (EPE) use-case
   [I-D.ietf-spring-segment-routing-central-epe] are specified in
   [I-D.ietf-idr-bgpls-segment-routing-epe].  This document leverages
   the BGP-LS TLVs defined for BGP-LS EPE and other BGP-LS documents and
   specifies the procedures for advertising the underlying topology in a
   more generic BGP-only fabric use-case.

   This document specifies the operations and procedures when using the
   design involving BGP use for hop-by-hop routing between directly
   connected network nodes (refer [RFC7938] for details).

2.  BGP Routing in the Fabric

   This document does not change base BGP routing protocol operations in
   the fabric that provides routing using the BGP best path selection
   process [RFC4271] .

   The applicability of this specification is limited to those
   deployments where BGP is used as hop-by-hop routing protocol between
   directly connected nodes in the fabric.  While a data-center design
   [RFC7938] is used as a reference, the topology advertisement and its
   use for computation may also apply to other networks with BGP-only
   fabric or to BGP-only portions of a larger network topology.

   BGP hop-by-hop routing can be setup using EBGP single-hop sessions
   over individual links between directly connected routers using their
   link addresses for peering as described in [RFC7938].  In such a
   design, the neighbors' link addresses may be provisioned for peering



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   and the EBGP session operating directly over the link performs the
   monitoring of the neighbor on that link.  A variation of this design
   would be that the EBGP session is setup between directly connected
   routers using their loopback sessions.  The mechanisms for discovery
   of the neighbor's link addresses and their monitoring on a per link
   basis are outside the scope of this document.
   [I-D.xu-idr-neighbor-autodiscovery] describes one such mechanism and
   the same may be also realized by other means.

   Though this document uses the EBGP based design as a reference, it
   does not preclude other alternate designs using IBGP.

3.  Topology Collection Mechanism

   BGP-LS [RFC7752] has been defined to allow BGP to convey topology
   information in the form of Link-State objects - node, link and
   prefix.  The properties of each of these objects are encoded using
   BGP-LS Attribute TLVs.  Applications need a topological view and
   visibility even for networks where BGP is the only routing protocol.
   In such networks, each BGP router advertises its local information
   which includes its node, links and prefix attributes via BGP-LS.

   Figure 1 describes a typical deployment scenario.  Every BGP router
   in the network is enabled for BGP-LS and forms BGP-LS sessions with
   one or more centralized BGP-LS speakers over which it sends its local
   topology information.  Each BGP router MAY also receive the topology
   information from all other BGP routers via these centralized BGP-LS
   speakers.  This way, any BGP router (as also the centralized BGP-LS
   speakers) MAY obtain aggregated Link-State information for the entire
   BGP network.  An external component (e.g. a controller) can obtain
   this information from the centralized BGP-LS speakers or directly by
   doing BGP-LS peering to the BGP routers.  An internal software
   component on any of the BGP routers (e.g.  TE module) can also
   receive the entire BGP network topology information from its local
   BGP process.
















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                  +------------+
                  | Controller |
                  +------------+
                        ^
                        |
                        v
               +-------------------+
               |  BGP-LS Speaker   |       +------------+
               |  (Centralized)    |       | Controller |
               +-------------------+       +------------+
                     ^   ^   ^                   ^
                     |   |   |                   |
         +-----------+   |   +---------------+   |
         |               |                   |   |
         v               v                   v   v
    +-----------+    +-----------+         +-----------+    +----------+
    |    BGP    |    |    BGP    |         |    BGP    |<-->| Local    |
    |  Router   |    |  Router   |  . . .  |  Router   |    | Consumer |
    +-----------+    +-----------+         +-----------+    +----------+
         ^                ^                    ^
         |                |                    |
     Local Info       Local Info            Local Info
    (node & links)  (node & links)         (node & links)

                   Figure 1: Link State info collection

3.1.  Peering Models

   The peering model described above relies on the base BGP IPv4 or IPv6
   routing underlay (e.g. as described in [RFC7938]) or any other
   mechanism for reachability for the BGP-LS session establishment with
   the centralized BGP speakers.  A variation of this model would be to
   setup reachability to the centralized BGP speakers (or controller)
   over the out of band management network, where available, and for
   each BGP router in the fabric use the same for the BGP-LS session
   establishment with the centralized BGP speakers.  This variation
   removes the dependency between the topology learning via BGP-LS from
   the base best effort reachability over the BGP routing in the fabric.

   Another alternate design would be to enable BGP-LS as well on the hop
   by hop EBGP sessions in the underlay as described in [RFC7938].  This
   approach results in the topology information being flooded via BGP-LS
   hop-by-hop along the BGP routers in the network.  Other peering
   designs for BGP-LS sessions may also be possible and they are not
   precluded by this document.






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4.  Advertising BGP-only Network Topology

   This section specifies the BGP-LS TLVs and sub-TLVs and their use for
   advertising the topology of a BGP-only network in the form of BGP-LS
   Node, Link and Prefix NLRIs.

   BGP-LS [RFC7752] defines the BGP-LS NLRI types (i.e.  Node NLRI, Link
   NLRI and Prefix NLRI) along with their corresponding BGP-LS Attribute
   (i.e.  Node Attribute, Link Attribute or Prefix Attribute) and the
   TLVs that map to the respective NLRI and Attribute for each type.

   [I-D.ietf-idr-bgpls-segment-routing-epe] specifies the BGP Protocol
   ID to be used for signaling BGP EPE information and the same is used
   for advertising of BGP topology.

   [I-D.ietf-idr-te-lsp-distribution] defines the BGP-LS NLRI that can
   be used to advertise the RSVP-TE or Segment Routing (SR) policies
   instantiated on a BGP Router head-end along with their corresponding
   BGP-LS Attribute TLVs to advertise their properties and state.

   The following sub-sections specify the use of these encodings by a
   router running BGP protocol.

4.1.  Node Advertisements

   [RFC7752] defines Node NLRI Type and the Node Descriptor TLVs 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
    +-+-+-+-+-+-+-+-+
    |  Protocol-ID  |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                           Identifier                          |
    |                            (64 bits)                          |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    //                Local Node Descriptors (variable)            //
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


   [I-D.ietf-idr-bgpls-segment-routing-epe] introduces additional Node
   Descriptor TLVs for BGP protocol that are required to be used.

   The following Node Descriptors TLVs MUST appear in the Node NLRI as
   Local Node Descriptors:

   o  BGP Router-ID, which contains the BGP Identifier of the
      originating BGP router



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   o  Autonomous System Number, which contains the advertising router
      ASN.

   The BGP-LS Attribute associated with the Node NLRI MAY include the
   following TLVs that are defined in respective documents to signal the
   router properties and capabilities (Section 5.1 defines the
   procedures for their advertisements):

   +--------+--------------+-------------------------------------------+
   |  TLV   | Description  | Reference Document                        |
   |  Code  |              |                                           |
   | Point  |              |                                           |
   +--------+--------------+-------------------------------------------+
   |  1026  | Node Name    | [RFC7752]                                 |
   |  1028  | IPv4 TE      | [RFC7752]                                 |
   |        | Router-ID    |                                           |
   |  1029  | IPv6 TE      | [RFC7752]                                 |
   |        | Router-ID    |                                           |
   |  1161  | SID/Label    | [I-D.ietf-idr-bgp-ls-segment-routing-ext] |
   |  1034  | SRGB &       | [I-D.ietf-idr-bgp-ls-segment-routing-ext] |
   |        | Capabilities |                                           |
   |  1035  | SR Algorithm | [I-D.ietf-idr-bgp-ls-segment-routing-ext] |
   |  1036  | SR Local     | [I-D.ietf-idr-bgp-ls-segment-routing-ext] |
   |        | Block        |                                           |
   |  266   | Node MSD     | [I-D.ietf-idr-bgp-ls-segment-routing-msd] |
   |  TBD   | Flex         | [I-D.ketant-idr-bgp-ls-flex-algo]         |
   |        | Algorithm    |                                           |
   |        | Definition   |                                           |
   +--------+--------------+-------------------------------------------+

                       Table 1: Node Attribute TLVs

   The above list of TLVs is not exhaustive but indicative as of the
   time of writing of this document.

4.2.  Link Advertisements

   [RFC7752] defines Link NLRI Type and its Node and Link Descriptor
   TLVs 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
    +-+-+-+-+-+-+-+-+
    |  Protocol-ID  |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                           Identifier                          |
    |                            (64 bits)                          |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    //               Local Node Descriptors (variable)             //
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    //               Remote Node Descriptors (variable)            //
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    //                  Link Descriptors (variable)                //
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


   The following Node Descriptors TLVs MUST appear in the Link NLRI as
   Local Node Descriptors:

   o  BGP Router-ID, which contains the BGP Identifier of the
      originating BGP router

   o  Autonomous System Number, which contains the advertising router
      ASN.

   The following Node Descriptors TLVs MUST appear in the Link NLRI as
   Remote Node Descriptors:

   o  BGP Router-ID, which contains the BGP Identifier of the peer BGP
      router

   o  Autonomous System Number, which contains the peer ASN.

   The following Link Descriptors TLVs MUST appear in the Link NLRI as
   Link Descriptors:

   o  Link Local/Remote Identifiers containing the 4-octet Link Local
      Identifier followed by the 4-octet Link Remote Identifier.  The
      value 0 MUST be used for the Link Remote Identifier when the value
      is unknown.

   In addition, the following Link Descriptors TLVs SHOULD appear in the
   Link NLRI as Link Descriptors based on the address family used for
   setting up the BGP Peering or the addresses configured on the links:

   o  IPv4 Interface Address contains the address of the local interface
      through which the BGP session is established using IPv4 address.




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   o  IPv6 Interface Address contains the address of the local interface
      through which the BGP session is established using IPv6 address.

   o  IPv4 Neighbor Address contains the IPv4 address of the peer
      interface used by the BGP session establishment using IPv4
      address.

   o  IPv6 Neighbor Address contains the IPv6 address of the peer
      interface used by the BGP session establishment using IPv6
      address.

   The BGP-LS Attribute associated with the Link NLRI MAY include the
   following TLVs that are defined in respective documents to signal the
   router's local links' properties and capabilities (Section 5.2
   defines the procedures for their advertisements) :




































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   +------+----------------+-------------------------------------------+
   | TLV  | Description    | Reference Document                        |
   | Code |                |                                           |
   | Poin |                |                                           |
   |  t   |                |                                           |
   +------+----------------+-------------------------------------------+
   | 1088 | Administrative | [RFC7752]                                 |
   |      | group (color)  |                                           |
   | 1173 | Extended       | [I-D.ietf-idr-eag-distribution]           |
   |      | Administrative |                                           |
   |      | group (color)  |                                           |
   | 1089 | Maximum link   | [RFC7752]                                 |
   |      | bandwidth      |                                           |
   | 1092 | TE Default     | [RFC7752]                                 |
   |      | Metric         |                                           |
   | 1096 | SRLG           | [RFC7752]                                 |
   | 1098 | Link Name      | [RFC7752]                                 |
   | 267  | Link MSD       | [I-D.ietf-idr-bgp-ls-segment-routing-msd] |
   | 1172 | L2 Bundle      | [I-D.ietf-idr-bgp-ls-segment-routing-ext] |
   |      | Member         |                                           |
   | 1104 | Unidirectional | [I-D.ietf-idr-te-pm-bgp]                  |
   |      | link delay     |                                           |
   | 1105 | Min/Max        | [I-D.ietf-idr-te-pm-bgp]                  |
   |      | Unidirectional |                                           |
   |      | link delay     |                                           |
   | 1106 | Min/Max        | [I-D.ietf-idr-te-pm-bgp]                  |
   |      | Unidirectional |                                           |
   |      | link delay     |                                           |
   | 1107 | Unidirectional | [I-D.ietf-idr-te-pm-bgp]                  |
   |      | packet loss    |                                           |
   | 1101 | EPE Peer Node  | [I-D.ietf-idr-bgpls-segment-routing-epe]  |
   |      | SID            |                                           |
   | 1102 | EPE Peer Adj   | [I-D.ietf-idr-bgpls-segment-routing-epe]  |
   |      | SID            |                                           |
   | 1103 | EPE Peer Set   | [I-D.ietf-idr-bgpls-segment-routing-epe]  |
   |      | SID            |                                           |
   +------+----------------+-------------------------------------------+

                       Table 2: Link Attribute TLVs

   The above list of TLVs is not exhaustive but indicative as of the
   time of writing of this document.

4.3.  Prefix Advertisements

   [RFC7752] defines Prefix NLRI Type and its Node and Prefix Descriptor
   TLVs 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
    +-+-+-+-+-+-+-+-+
    |  Protocol-ID  |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                           Identifier                          |
    |                            (64 bits)                          |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    //              Local Node Descriptors (variable)              //
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    //                Prefix Descriptors (variable)                //
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


   The following Node Descriptors TLVs MUST appear in the Prefix NLRI as
   Local Node Descriptors:

   o  BGP Router-ID, which contains the BGP Identifier of the
      originating BGP router

   o  Autonomous System Number, which contains the advertising router
      ASN.

   The Prefix Descriptor MUST contain the IP Reachability information
   TLV to identify the prefix.

   This document defines a new BGP Route Type TLV that MUST be included
   in the Prefix Descriptor when the BGP node advertises the Prefix
   NLRI.  The format of this TLV 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            |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |  Route Type   |
    +-+-+-+-+-+-+-+-+


   Where:

      Type: 2 octet field with value TBD, see Section 7.

      Length: 2 octet field with value set to 1.

      Route Type: one octet with the following values defined:





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    +-----+---------------+------------------------------------------+
    |Value|     Type      |      Description                         |
    +-----+---------------+------------------------------------------+
    |  1  | Local         | Local interface prefix e.g. Loopback     |
    |  2  | Attached      | Directly attached node's prefix e.g host |
    |  3  | External BGP  | Prefix learnt via EBGP                   |
    |  4  | Internal BGP  | Prefix learnt via IBGP                   |
    |  5  | Redistributed | Prefix redistributed into BGP            |
    +-------+-------------+------------------------------------------+


                         Figure 2: BGP Route Types

   The BGP-LS Attribute associated with the Prefix NLRI MAY include the
   following TLVs that are defined in respective documents to signal the
   router's own prefix properties and capabilities (Section 5.3 defines
   the procedures for their advertisements):

   +---------+-------------+-------------------------------------------+
   |   TLV   | Description | Reference Document                        |
   |   Code  |             |                                           |
   |  Point  |             |                                           |
   +---------+-------------+-------------------------------------------+
   |   1155  | Prefix      | [RFC7752]                                 |
   |         | Metric      |                                           |
   |   1158  | Prefix SID  | [I-D.ietf-idr-bgp-ls-segment-routing-ext] |
   +---------+-------------+-------------------------------------------+

                      Table 3: Prefix Attribute TLVs

   The above list of TLVs is not exhaustive but indicative as of the
   time of writing of this document.

4.4.  TE Policy Advertisements

   [I-D.ietf-idr-te-lsp-distribution] defines TE Policy NLRI Type and
   its Headend Node and TE Policy Descriptor TLVs 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
    +-+-+-+-+-+-+-+-+
    |  Protocol-ID  |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                        Identifier                             |
    |                        (64 bits)                              |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    //                Headend (Node Descriptors)                   //
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    //                TE Policy Descriptors (variable)             //
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


   The Node Descriptors TLVs are the same as specified in Section 4.1.
   The semantics for the TE Policy Descriptor TLVs and the TLVs
   associated with the BGP-LS Attribute are used as specified in
   [I-D.ietf-idr-te-lsp-distribution].

5.  Procedures

   In a network where BGP is the only routing protocol, the BGP-LS
   session is used to advertise the necessary information about the
   local node properties, its local links' properties and where
   necessary the prefix's owned by the node.  TE Policies, that are
   instantiated on the local node (i.e. when it is the head-end for the
   policy), along with their properties are also advertised via the BGP-
   LS session.  This information, once collected across all BGP routers
   in the network, provides a complete topology view of the network.
   Many of these attributes are not part of the base BGP protocol
   operations and are either configured or provided by other components
   on the router.  BGP-LS performs the role of collecting this
   information and propagating it across the BGP network.

   The following sections describe the procedures for the propagation of
   the BGP-LS NLRIs on a BGP router into the BGP-LS session.  These
   procedures for propagation of BGP topology information via BGP-LS
   SHOULD be applied only in deployments and use-cases where necessary
   and SHOULD NOT be applied in every BGP deployment when BGP-LS is
   enabled.  Implementations MAY provide a configuration option to
   enable these procedures in required deployments.

5.1.  Advertisement of Router's Node Attributes

   Advertisement of the Node NLRI via BGP-LS by each BGP router in a
   BGP-only network enables the discovery of all the router nodes in the
   topology.  The Node NLRI MUST be generated by a BGP router only for




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   itself and even when there are no attributes to be advertised along
   with it.

   The Node attributes defined currently related to Segment Routing (SR)
   [RFC8402] have been described in Table 1 and are to be advertised
   when SR is enabled.  This includes:

   o  All SR enabled routers support the default SR algorithm 0 and MUST
      advertise it in the SR Algorithm TLV.  Other algorithms (including
      Flexible Algorithm [I-D.ietf-lsr-flex-algo]) SHOULD be advertised
      when supported.

   o  The Segment Routing Global Block (SRGB) provisioned on the router
      which is used by BGP Prefix SIDs [I-D.ietf-idr-bgp-prefix-sid] and
      other SR control plane protocols on the router MUST be advertised.
      The value for Flags field in the TLV is not defined for BGP
      protocol and MUST be set to 0 by the originator and ignored by
      receivers.

   o  The Segment Routing Local Block (SRLB) provisioned on the router
      which MAY be used by BGP EPE SIDs
      [I-D.ietf-idr-bgpls-segment-routing-epe] SHOULD be advertised.
      The value for Flags field in the TLV is not defined for BGP
      protocol and MUST be set to 0 by the originator and ignored by
      receivers.

   o  The Node level MSD provides the Node's capabilities for SR SID
      operations and SHOULD be advertised.

   o  When the router supports SR Flexible Algorithms and is provisioned
      with the Flexible Algorithm Definition (FAD), then it MUST
      advertise the same.

   The Node Name Attribute SHOULD be advertised when available.

   This document introduces some of the TE concepts into BGP-only
   networks.  Provisioning of TE Router-ID with a unique address
   normally associated with a loopback interface on the router enables
   TE use-cases for both IPv4 and IPv6 SHOULD be supported.  The BGP
   Router-ID along with the ASN also provides the capability for
   uniquely identifying a BGP router in the network.

   Other Node Attributes applicable to a BGP Router may also be included
   and this document does not describe the exhaustive list.







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5.2.  Advertisement of Router's Local Links Attributes

   Each BGP router in a BGP-only network also advertises its local links
   using the Link NLRIs thru BGP-LS.  The Link NLRI for a given link
   between two BGP routers is advertised as uni-directional logical
   "half-link" and its link descriptors allow the correlation between
   the two NLRIs "half-links" originated by the peering routers to
   describe the bi-directional logical link and its attributes on both
   routers.

   The discovery of all the links and their local and remote identifiers
   in a BGP-only network relies on the design that uses EBGP sessions
   over each interconnecting link using the link IP addresses (refer
   [RFC7938]).  In this case, a Link NLRI MUST be generated by a BGP
   router for each of its local link regardless of whether it has any
   link attributes to be advertised for it.

   When doing EBGP multi-hop sessions between directly connected BGP
   routers, the underlying link information would need to learn by some
   discovery protocol or provisioning entity.  The mechanisms to learn
   the underlying link information for BGP-LS advertisements are outside
   the scope of this document.  However, to provide a true link topology
   picture, the advertisement of underlying links is RECOMMENDED for
   most use-cases instead of a single EBGP peering representation of a
   link between the routers using their loopback addresses.

   The Link NLRI represents an adjacency between BGP routers and its
   association with the underlying Layer 3 link.  When the underlying
   Layer 3 link or the BGP session on top of it goes down, the Link NLRI
   MUST be withdrawn by the BGP router.  The monitoring of links,
   detecting of their failures and notification to BGP may be performed
   using mechanisms like BFD.  This enables faster detection of failures
   and verification of the underlying links.

   Advertisement of the Link NLRIs via BGP-LS by each BGP router in a
   BGP-only network enables the discovery of all the active links in the
   topology.

   TE attributes for links have been traditionally associated with Link
   State Routing protocols.  However, with the ability to discover the
   link topology via BGP-LS as specified in this document, the TE
   attributes and their principles can also be applied to a network
   running BGP alone.  The TE attributes for a link have been described
   in Table 2 and MAY be advertised when TE use-cases are enabled.  This
   includes:

   o  The maximum bandwidth of a link is its protocol independent
      attribute and SHOULD be advertised.



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   o  TE concepts of Administrative Groups (also known as affinities)
      and Shared Risk Link Groups (SRLGs) MAY be provisioned locally on
      links and then MUST be advertised.

   o  The BGP base protocol does not operate with link metrics, however,
      a TE metric concept can be introduced in a BGP only network as
      well for TE use-cases.  Implementations MAY provide the ability to
      provision TE metric value for a link for BGP use including a
      different default value for it.  The TE metric attribute SHOULD be
      advertised for each link when configured and its default value is
      taken as 100.  When not advertised for a link, implementations who
      intend to use the TE metric MUST assume the value to be 100.

   o  The delay and loss TE metrics for links are measured via MPLS
      Performance Monitoring [RFC6374] and their measurement mechanism
      over a link are independent of the routing protocol.  The same
      mechanism MAY be enabled in BGP-only networks and their values
      advertised via BGP-LS.

   The Link attributes defined currently related to the Segment Routing
   feature BGP EPE [I-D.ietf-idr-bgpls-segment-routing-epe] have been
   described in Table 2 and are to be advertised when SR use-cases are
   enabled.  This includes:

   o  The BGP Peering SIDs provide a functionality similar to Adjacency-
      SID (refer [RFC8402]) in BGP-only networks.  Implementations
      SHOULD allocate the BGP Peer-Adjacency SID for all its links and
      the BGP Peer-Node SID for all its peer routers.  Implementations
      MAY allocate the BGP Peer-Set SID based on local configuration.

   o  The Link level MSD provides the per link capabilities for SR SID
      operations and SHOULD be advertised when the router links have
      differing capabilities.

   The use of Layer 3 bundle links which comprise of multiple layer 2
   member links are often used in BGP networks.  When BGP session is
   configured over such a layer 3 link, the link attributes of the
   underlying layer 2 links MAY be advertised individually using the L2
   Bundle Member TLV.  The applicable attributes for the L2 links are
   described in [I-D.ietf-idr-bgp-ls-segment-routing-ext].

   The Link Name Attribute MAY be advertised when available.

   Other Link Attributes applicable to a BGP Router may also be included
   and this document does not describe the exhaustive list.






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5.3.  Advertisement of Router's Prefix Attributes

   Advertisement of the Prefix NLRI via BGP-LS may be required only in
   specific use-cases.  Since the base BGP protocol along with its
   extensions already signals Prefix reachability via different NLRIs,
   there is no necessity to duplicate the information via BGP-LS
   session.  However, for specific use-cases related to SR Traffic
   Engineering (SR-TE), it is required for each router to advertise it's
   Prefix SID(s) (refer [RFC8402]) that can be used to direct traffic
   via specific BGP routers.  Advertising such BGP Prefix SID for every
   BGP router provides this key attribute via BGP-LS and avoids the
   requirement for the consumer of the topology information (e.g. a
   controller or local TE process) to tap into other BGP NLRI
   information.

   Advertisement of the Prefix NLRI via BGP-LS MUST be done for its
   locally configured prefixes (e.g. its loopback interface address) and
   when BGP is advertising the BGP Prefix SID
   ([I-D.ietf-idr-bgp-prefix-sid]) for it.  The advertisement of the
   Prefix NLRI via BGP-LS for other prefixes learnt by the router MAY be
   done based on the specific use-case requirement and the BGP Route
   Type as described in Figure 2 indicates the type of route being
   advertised.

   The Prefix attributes defined currently related to SR [RFC8402] have
   been described in Table 3 and MAY be advertised when SR is enabled.
   This includes:

   o  The Prefix SID TLV is included with the SID advertised as the
      index to be consistent with the Label-Index TLV of BGP Prefix SID
      attribute.  The default algorithm is MUST be set to 0 by the
      originator except in the case where a local prefix is associated
      with a specific SR Algorithm.  The flags are defined as the most
      significant 8 bits of the 16 bit field defined for Label-Index TLV
      in [I-D.ietf-idr-bgp-prefix-sid].

   o  For certain SR-TE uses, the Prefix Metric value MAY be included
      and it is set based on the SR-TE computation based on the link-
      state topology learnt via BGP-LS.

   Other Prefix Attributes applicable may also be included and this
   document does not describe the exhaustive list.

5.4.  Advertisement of Router's TE Policy Attributes

   TE Policies that are setup using RSVP-TE or SR-TE mechanisms MAY be
   instantiated on a BGP router.  One use-case that results in such SR
   Policy instantiation on a BGP router is described later in this



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   document in Section 6.2.  Advertising such TE Policies instantiated
   for every BGP router as head-end via BGP-LS provides the consumer of
   the topology information (e.g. a controller or local TE process) a
   policy view of the BGP fabric as well.

   The procedures for advertisement of the TE Policy NLRI via BGP-LS
   MUST be done only for its locally instantiated TE Policies and as
   specified in [I-D.ietf-idr-te-lsp-distribution]).  Implementation MAY
   provide configuration options to control the specific set of TE
   Policies that are to be advertised from the local node.

6.  Usage of BGP Topology

   This section describes some of the use-cases for the building of the
   BGP topology information as specified in this document and leveraging
   it for enabling new functionality.

6.1.  Topology View for Monitoring

   The BGP-LS advertisement of the BGP topology as specified in this
   document provides a live topology view of the BGP network for an
   application or controller that is monitoring the network.  The
   topology view is from the BGP protocol perspective and includes the
   underlying links as well that aids in network monitoring as well as
   diagnostics use-cases.  BGP-LS is the de-facto protocol for
   northbound propagation of network topology related information for
   most IGP networks and extending this capability for BGP-only networks
   allows existing controllers and applications to consume the
   information with some incremental BGP protocol awareness.

6.2.  SR-TE in BGP Networks

   The SR-TE use-case for BGP builds on top of functionality specified
   in [I-D.ietf-idr-bgp-prefix-sid] and also described in
   [I-D.ietf-spring-segment-routing-msdc].The BGP SR Prefix SID
   signaled, provides the basic connectivity between all BGP routers
   using their loopback addresses.  This provides the basic best-effort
   paths in the network using the base BGP decision process that is
   unchanged.  BGP and other overlay routes and services recurse on top
   of these loopback addresses of the egress nodes and the forwarding is
   done via the BGP SR Prefix SID labels in the underlay.  While this
   version of the document focuses on the examples with MPLS dataplane
   instantiation for SR, the same is applicable for the IPv6 dataplane
   instantiation (SRv6) as well.

   SR-TE for BGP provides underlay paths through the network for the
   overlay routes and services with specific SLA requirements and use-




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   cases like path disjointness, low latency paths, inclusion or
   exclusion and other TE considerations.

   [I-D.ietf-spring-segment-routing-policy] specifies the SR-TE
   architecture and the SR Policy construct.
   [I-D.ietf-idr-segment-routing-te-policy] describes the extensions to
   BGP for signaling of SR Policies from a controller to the SR-TE
   headend BGP router.  BGP-LS has been extended to allow signaling of
   the SR Policies from SR-TE head-end to controllers via
   [I-D.ietf-idr-te-lsp-distribution] which allows the controllers to
   learn the state of SR Policies instantiated on routers in the
   network.  This document completes the missing piece that is related
   to getting the BGP topology information from all the routers to a
   controller as well the local SRTE process on each router for their
   path computation requirements.

   The signaling of SR Polices from controller to SR-TE headend and
   reporting of the state back to the controller can also be done using
   PCEP ([I-D.ietf-pce-segment-routing], [RFC8281], [RFC8231]).
   However, the BGP topology learning via BGP-LS which is specified in
   this document is also required for the deployments that uses PCEP in
   the BGP-only network.

   The topology collected via BGP-LS in a BGP-only fabric in a Segment
   Routing deployment comprise of:

   o  The properties of every BGP router node and the Prefix SIDs to
      reach that node.

   o  The properties of all the links between the BGP routers and the
      Peer-Adjacency-SIDs (and other EPE SIDs) corresponding to them
      that allow directing traffic over specific links and/or to
      specific neighbors.

   o  The properties and state of the SR Policies instantiatied on each
      of the BGP routers along with their end points, their properties
      and most importantly the Binding SID to steer traffic into the SR
      Policies.

   This topology information allows a computation node to build SR
   Policies for services over the BGP fabric for a given traffic
   engineering objective at any given node.

   The topology of the BGP fabric is advertised to a centralized
   controller or application for use-cases that need a centralized
   computation of SR Policy which can then be signaled to the SR-TE
   head-end node via PCEP or BGP-SRTE.  The topology may also be
   distributed to any node in the BGP fabric to be used by its local SR-



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   TE process to perform path computation for its own SR Policies for
   use-cases that are addressed by local computation.

   A high level summary of the key topology information advertised via
   BGP-LS by BGP routers can be used for TE computations as follows

   o  The BGP SR Prefix SIDs and the BGP EPE Peering Adjacency SIDs
      provide the equivalent of the IGP Prefix and Adjacency SIDs and
      can be used to direct traffic to a specific BGP router and over a
      specific BGP peer session or link respectively.  Traffic for the
      BGP SR Prefix SIDs follow the path computed by the BGP decision
      process.

   o  The TE metric can be used to tailor the choice of specific paths
      in the network for SR-TE.

   o  The TE administrative group (also known as affinities) and SRLG
      attributes can be configured over links to enable computation of
      paths with inclusion and exclusion of specific links or paths that
      are mutually disjoint.

   o  The enabling of link delay and loss measurements and their
      advertisements can help monitoring the link quality and carve out
      paths based on latency and other SLA requirements.

   o  The signaling of the Node and Link MSD allows controllers to
      instantiate SR Policies based on the capability of the routers.

   This section attempts to highlight and describe at a high level some
   of the possible SR-TE solutions and use-cases in a BGP-only network.
   The actual SR-TE computation and algorithms are outside the scope of
   this document.

7.  IANA Considerations

   IANA maintains a registry called "Border Gateway Protocol - Link
   State (BGP-LS) Parameters" with a sub-registry called "Node Anchor,
   Link Descriptor and Link Attribute TLVs".

   The following TLV codepoints are suggested (to be assigned by IANA):

   +----------+----------------------------------------+---------------+
   | TLV Code |             Description                | Value defined |
   |  Point   |                                        |       in      |
   +----------+----------------------------------------+---------------+
   |   TBD    |   BGP Route Type TLV                   | this document |
   +----------+----------------------------------------+---------------+




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8.  Manageability Considerations

   This section is structured as recommended in [RFC5706].

8.1.  Operational Considerations

8.1.1.  Operations

   Existing BGP and BGP-LS operational procedures apply.  No additional
   operation procedures are defined in this document.

9.  Security Considerations

   Procedures and protocol extensions defined in this document do not
   affect the BGP security model.  See the 'Security Considerations'
   section of [RFC4271] for a discussion of BGP security.  Also refer to
   [RFC4272] and [RFC6952] for analysis of security issues for BGP.

10.  Acknowledgements

   The authors would like to thank Bruno Decraene for his review and
   comments on this document.

11.  References

11.1.  Normative References

   [I-D.ietf-idr-bgp-ls-segment-routing-ext]
              Previdi, S., Talaulikar, K., Filsfils, C., Gredler, H.,
              and M. Chen, "BGP Link-State extensions for Segment
              Routing", draft-ietf-idr-bgp-ls-segment-routing-ext-12
              (work in progress), March 2019.

   [I-D.ietf-idr-bgp-ls-segment-routing-msd]
              Tantsura, J., Chunduri, U., Mirsky, G., Sivabalan, S., and
              N. Triantafillis, "Signaling MSD (Maximum SID Depth) using
              Border Gateway Protocol Link-State", draft-ietf-idr-bgp-
              ls-segment-routing-msd-04 (work in progress), February
              2019.

   [I-D.ietf-idr-bgp-prefix-sid]
              Previdi, S., Filsfils, C., Lindem, A., Sreekantiah, A.,
              and H. Gredler, "Segment Routing Prefix SID extensions for
              BGP", draft-ietf-idr-bgp-prefix-sid-27 (work in progress),
              June 2018.






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   [I-D.ietf-idr-bgpls-segment-routing-epe]
              Previdi, S., Talaulikar, K., Filsfils, C., Patel, K., Ray,
              S., and J. Dong, "BGP-LS extensions for Segment Routing
              BGP Egress Peer Engineering", draft-ietf-idr-bgpls-
              segment-routing-epe-17 (work in progress), October 2018.

   [I-D.ietf-idr-eag-distribution]
              Wang, Z., Wu, Q., and J. Tantsura, "Distribution of MPLS-
              TE Extended admin Group Using BGP", draft-ietf-idr-eag-
              distribution-08 (work in progress), October 2018.

   [I-D.ietf-idr-te-lsp-distribution]
              Previdi, S., Talaulikar, K., Dong, J., Chen, M., Gredler,
              H., and J. Tantsura, "Distribution of Traffic Engineering
              (TE) Policies and State using BGP-LS", draft-ietf-idr-te-
              lsp-distribution-10 (work in progress), February 2019.

   [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-18 (work in progress), December 2018.

   [I-D.ietf-lsr-flex-algo]
              Psenak, P., Hegde, S., Filsfils, C., Talaulikar, K., and
              A. Gulko, "IGP Flexible Algorithm", draft-ietf-lsr-flex-
              algo-01 (work in progress), November 2018.

   [I-D.ketant-idr-bgp-ls-flex-algo]
              Talaulikar, K., Psenak, P., Zandi, S., and G. Dawra,
              "Flexible Algorithm Definition Advertisement with BGP
              Link-State", draft-ketant-idr-bgp-ls-flex-algo-01 (work in
              progress), February 2019.

   [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>.

   [RFC4271]  Rekhter, Y., Ed., Li, T., Ed., and S. Hares, Ed., "A
              Border Gateway Protocol 4 (BGP-4)", RFC 4271,
              DOI 10.17487/RFC4271, January 2006,
              <https://www.rfc-editor.org/info/rfc4271>.








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   [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>.

11.2.  Informative References

   [I-D.ietf-idr-segment-routing-te-policy]
              Previdi, S., Filsfils, C., Jain, D., Mattes, P., Rosen,
              E., and S. Lin, "Advertising Segment Routing Policies in
              BGP", draft-ietf-idr-segment-routing-te-policy-05 (work in
              progress), November 2018.

   [I-D.ietf-pce-segment-routing]
              Sivabalan, S., Filsfils, C., Tantsura, J., Henderickx, W.,
              and J. Hardwick, "PCEP Extensions for Segment Routing",
              draft-ietf-pce-segment-routing-16 (work in progress),
              March 2019.

   [I-D.ietf-spring-segment-routing-central-epe]
              Filsfils, C., Previdi, S., Dawra, G., Aries, E., and D.
              Afanasiev, "Segment Routing Centralized BGP Egress Peer
              Engineering", draft-ietf-spring-segment-routing-central-
              epe-10 (work in progress), December 2017.

   [I-D.ietf-spring-segment-routing-msdc]
              Filsfils, C., Previdi, S., Dawra, G., Aries, E., and P.
              Lapukhov, "BGP-Prefix Segment in large-scale data
              centers", draft-ietf-spring-segment-routing-msdc-11 (work
              in progress), November 2018.

   [I-D.ietf-spring-segment-routing-policy]
              Filsfils, C., Sivabalan, S., daniel.voyer@bell.ca, d.,
              bogdanov@google.com, b., and P. Mattes, "Segment Routing
              Policy Architecture", draft-ietf-spring-segment-routing-
              policy-02 (work in progress), October 2018.

   [I-D.xu-idr-neighbor-autodiscovery]
              Xu, X., Talaulikar, K., Bi, K., Tantsura, J., and N.
              Triantafillis, "BGP Neighbor Discovery", draft-xu-idr-
              neighbor-autodiscovery-10 (work in progress), October
              2018.

   [RFC2328]  Moy, J., "OSPF Version 2", STD 54, RFC 2328,
              DOI 10.17487/RFC2328, April 1998,
              <https://www.rfc-editor.org/info/rfc2328>.




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   [RFC3630]  Katz, D., Kompella, K., and D. Yeung, "Traffic Engineering
              (TE) Extensions to OSPF Version 2", RFC 3630,
              DOI 10.17487/RFC3630, September 2003,
              <https://www.rfc-editor.org/info/rfc3630>.

   [RFC4272]  Murphy, S., "BGP Security Vulnerabilities Analysis",
              RFC 4272, DOI 10.17487/RFC4272, January 2006,
              <https://www.rfc-editor.org/info/rfc4272>.

   [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>.

   [RFC6374]  Frost, D. and S. Bryant, "Packet Loss and Delay
              Measurement for MPLS Networks", RFC 6374,
              DOI 10.17487/RFC6374, September 2011,
              <https://www.rfc-editor.org/info/rfc6374>.

   [RFC6952]  Jethanandani, M., Patel, K., and L. Zheng, "Analysis of
              BGP, LDP, PCEP, and MSDP Issues According to the Keying
              and Authentication for Routing Protocols (KARP) Design
              Guide", RFC 6952, DOI 10.17487/RFC6952, May 2013,
              <https://www.rfc-editor.org/info/rfc6952>.

   [RFC7938]  Lapukhov, P., Premji, A., and J. Mitchell, Ed., "Use of
              BGP for Routing in Large-Scale Data Centers", RFC 7938,
              DOI 10.17487/RFC7938, August 2016,
              <https://www.rfc-editor.org/info/rfc7938>.

   [RFC8231]  Crabbe, E., Minei, I., Medved, J., and R. Varga, "Path
              Computation Element Communication Protocol (PCEP)
              Extensions for Stateful PCE", RFC 8231,
              DOI 10.17487/RFC8231, September 2017,
              <https://www.rfc-editor.org/info/rfc8231>.

   [RFC8281]  Crabbe, E., Minei, I., Sivabalan, S., and R. Varga, "Path
              Computation Element Communication Protocol (PCEP)
              Extensions for PCE-Initiated LSP Setup in a Stateful PCE
              Model", RFC 8281, DOI 10.17487/RFC8281, December 2017,
              <https://www.rfc-editor.org/info/rfc8281>.

   [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>.





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Internet-Draft         BGP LS for BGP-only Fabric             March 2019


Authors' Addresses

   Ketan Talaulikar
   Cisco Systems
   Pune  411057
   India

   Email: ketant@cisco.com


   Clarence Filsfils
   Cisco Systems
   Brussels
   Belgium

   Email: cfilsfil@cisco.com


   Krishna Swamy
   Cisco Systems
   San Jose
   USA

   Email: kriswamy@cisco.com


   Shawn Zandi
   LinkedIn
   USA

   Email: szandi@linkedin.com


   Gaurav Dawra
   LinkedIn
   USA

   Email: gdawra.ietf@gmail.com


   Muhammad Durrani
   Equinix
   USA

   Email: mdurrani@equinix.com






Talaulikar, et al.     Expires September 10, 2019              [Page 25]


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