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Versions: 00 01 02 03 draft-ietf-idr-bgpls-segment-routing-epe

Network Working Group                                    S. Previdi, Ed.
Internet-Draft                                               C. Filsfils
Intended status: Standards Track                     Cisco Systems, Inc.
Expires: October 29, 2015                                         S. Ray
                                                  Individual Contributor
                                                                K. Patel
                                                     Cisco Systems, Inc.
                                                                 J. Dong
                                                                 M. Chen
                                                     Huawei Technologies
                                                          April 27, 2015


       Segment Routing Egress Peer Engineering BGP-LS Extensions
             draft-previdi-idr-bgpls-segment-routing-epe-03

Abstract

   Segment Routing (SR) leverages source routing.  A node steers a
   packet through a controlled set of instructions, called segments, by
   prepending the packet with an SR header.  A segment can represent any
   instruction, topological or service-based.  SR allows to enforce a
   flow through any topological path and service chain while maintaining
   per-flow state only at the ingress node of the SR domain.

   The Segment Routing architecture can be directly applied to the MPLS
   dataplane with no change on the forwarding plane.  It requires minor
   extension to the existing link-state routing protocols.

   This document outline a BGP-LS extension for exporting BGP egress
   point topology information (including its peers, interfaces and
   peering ASs) in a way that is exploitable in order to compute
   efficient Egress Point Engineering policies and strategies.

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




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   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at http://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on October 29, 2015.

Copyright Notice

   Copyright (c) 2015 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they 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.  Segment Routing Documents . . . . . . . . . . . . . . . . . .   3
   3.  BGP Peering Segments  . . . . . . . . . . . . . . . . . . . .   3
   4.  Link NLRI for EPE Connectivity Description  . . . . . . . . .   4
     4.1.  BGP Router ID and Member ASN  . . . . . . . . . . . . . .   5
     4.2.  EPE Node Descriptors  . . . . . . . . . . . . . . . . . .   5
     4.3.  Link Attributes . . . . . . . . . . . . . . . . . . . . .   6
   5.  Peer Node and Peer Adjacency Segments . . . . . . . . . . . .   7
     5.1.  Peer Node Segment . . . . . . . . . . . . . . . . . . . .   7
     5.2.  Peer Adjacency Segment  . . . . . . . . . . . . . . . . .   9
     5.3.  Peer Set Segment  . . . . . . . . . . . . . . . . . . . .  10
   6.  Illustration  . . . . . . . . . . . . . . . . . . . . . . . .  10
     6.1.  Reference Diagram . . . . . . . . . . . . . . . . . . . .  10
       6.1.1.  Peer Node Segment for Node D  . . . . . . . . . . . .  12
       6.1.2.  Peer Node Segment for Node H  . . . . . . . . . . . .  12
       6.1.3.  Peer Node Segment for Node E  . . . . . . . . . . . .  12
       6.1.4.  Peer Adj Segment for Node E, Link 1 . . . . . . . . .  13
       6.1.5.  Peer Adj Segment for Node E, Link 2 . . . . . . . . .  13
   7.  BGP-LS EPE TLV/Sub-TLV Code Points Summary  . . . . . . . . .  14
   8.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  14
   9.  Manageability Considerations  . . . . . . . . . . . . . . . .  14



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   10. Security Considerations . . . . . . . . . . . . . . . . . . .  14
   11. Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  15
   12. References  . . . . . . . . . . . . . . . . . . . . . . . . .  15
     12.1.  Normative References . . . . . . . . . . . . . . . . . .  15
     12.2.  Informative References . . . . . . . . . . . . . . . . .  15
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  16

1.  Introduction

   Segment Routing (SR) leverages source routing.  A node steers a
   packet through a controlled set of instructions, called segments, by
   prepending the packet with an SR header.  A segment can represent any
   instruction, topological or service-based.  SR allows to enforce a
   flow through any topological path and service chain while maintaining
   per-flow state only at the ingress node of the SR domain.

   The Segment Routing architecture can be directly applied to the MPLS
   dataplane with no change on the forwarding plane.  It requires minor
   extension to the existing link-state routing protocols.

   This document outline a BGP-LS extension for exporting BGP egress
   point topology information (including its peers, interfaces and
   peering ASs) in a way that is exploitable in order to compute
   efficient Egress Point Engineering policies and strategies.

   This document defines new types of segments: a Peer Node segment
   describing the BGP session between two nodes; a Peer Adjacency
   Segment describing the link (one or more) that is used by the BGP
   session; the Peer Set Segment describing an arbitrary set of sessions
   or links between the local BGP node and its peers.

2.  Segment Routing Documents

   The main reference for this document is the SR architecture defined
   in [I-D.ietf-spring-segment-routing].

   The Segment Routing Egress Peer Engineering architecture is described
   in [I-D.filsfils-spring-segment-routing-central-epe].

3.  BGP Peering Segments

   As defined in [draft-filsfils-spring-segment-routing-epe], an EPE
   enabled Egress PE node MAY advertise segments corresponding to its
   attached peers.  These segments are called BGP peering segments or
   BGP Peering SIDs.  They enable the expression of source-routed inter-
   domain paths.





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   An ingress border router of an AS may compose a list of segments to
   steer a flow along a selected path within the AS, towards a selected
   egress border router C of the AS and through a specific peer.  At
   minimum, a BGP Peering Engineering policy applied at an ingress PE
   involves two segments: the Node SID of the chosen egress PE and then
   the BGP Peering Segment for the chosen egress PE peer or peering
   interface.

   This document defines the BGP EPE Peering Segments: Peer Node, Peer
   Adjacency and Peer Set.

   Each BGP session MUST be described by a Peer Node Segment.  The
   description of the BGP session MAY be augmented by additional
   Adjacency Segments.  Finally, each Peer Node Segment and Peer
   Adjacency Segment MAY be part of the same group/set so to be able to
   group EPE resources under a common Peer-Set Segment Identifier (SID).

   Therefore, when the extensions defined in this document are applied
   to the use case defined in
   [I-D.filsfils-spring-segment-routing-central-epe]:

   o  One Peer Node Segment MUST be present.

   o  One or more Peer Adjacency Segments MAY be present.

   o  Each of the Peer Node and Peer Adjacency Segment MAY use the same
      Peer-Set.

4.  Link NLRI for EPE Connectivity Description

   This section describes the NLRI used for describing the connectivity
   of the BGP Egress router.  The connectivity is based on links and
   remote peers/ASs and therefore the existing Link-Type NLRI (defined
   in [I-D.ietf-idr-ls-distribution]) is used.  A new Protocol ID is
   used (codepoint to be assigned by IANA, suggested value 7).

   The use of a new Protocol-ID allows separation and differentiation
   between the NLRIs carrying BGP-EPE descriptors from the NLRIs
   carrying IGP link-state information as defined
   in[I-D.ietf-idr-ls-distribution].  The Link NLRI Type uses
   descriptors and attributes already defined in
   [I-D.ietf-idr-ls-distribution] in addition to new TLVs defined in the
   following sections of this document.

   The format of the Link NLRI Type 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
   +-+-+-+-+-+-+-+-+
   |  Protocol-ID  |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                           Identifier                          |
   |                            (64 bits)                          |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   //      Local Node Descriptors                                 //
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   //      Remote Node Descriptors                                //
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   //      Link Descriptors                                       //
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

      Node Descriptors and Link Descriptors are defined in
      [I-D.ietf-idr-ls-distribution].

4.1.  BGP Router ID and Member ASN

   Two new Node Descriptors Sub-TLVs are defined in this document:

   o  BGP Router Identifier (BGP Router-ID):

         Type: TBA (suggested value 516).

         Length: 4 octets

         Value: 4 octet unsigned integer representing the BGP Identifier
         as defined in [RFC4271] and [RFC6286].

   o  Confederation Member ASN (Member-ASN)

         Type: TBA (suggested value 517).

         Length: 4 octets

         Value: 4 octet unsigned integer representing the Member ASN
         inside the Confederation.[RFC5065].

4.2.  EPE Node Descriptors

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

   o  BGP Router ID, which contains the BGP Identifier of the local BGP
      EPE node.




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   o  Autonomous System Number, which contains the local ASN or local
      confederation identifier (ASN) if confederations are used.

   o  BGP-LS Identifier.

   The following Node Descriptors Sub-TLVs MAY appear in the Link NLRI
   as Local Node Descriptors:

   o  Member-ASN, which contains the ASN of the confederation member
      (when BGP confederations are used).

   o  Node Descriptors as defined in [I-D.ietf-idr-ls-distribution].

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

   o  BGP Router ID, which contains the BGP Identifier of the peer node.

   o  Autonomous System Number, which contains the peer ASN or the peer
      confederation identifier (ASN), if confederations are used.

   The following Node Descriptors Sub-TLVs MAY appear in the Link NLRI
   as Remote Node Descriptors:

   o  Member-ASN, which contains the ASN of the confederation member
      (when BGP confederations are used).

   o  Node Descriptors as defined in defined in
      [I-D.ietf-idr-ls-distribution].

4.3.  Link Attributes

   The following BGP-LS Link attributes TLVs are used with the Link
   NLRI:

   +----------+--------------------------+----------+
   | TLV Code | Description              |   Length |
   |  Point   |                          |          |
   +----------+--------------------------+----------+
   |    1099  | Adjacency-Segment        | variable |
   |          | Identifier (Adj-SID)     |          |
   |    TBA   | Peer-Segment Identifier  | variable |
   |          | (Peer-SID)               |          |
   |    TBA   | Peer-Set-SID             | variable |
   +----------+--------------------------+----------+






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   Adj-SID is defined in
   [I-D.gredler-idr-bgp-ls-segment-routing-extension] and the same
   format is used for the Peer-SID and Peer-Set-SID TLVs.

   Peer-SID and Peer-Set SID are two new sub-TLVs with the same format
   as the Adj-SID and whose codepoints are to be assigned by IANA:

      Peer-SID: SID representing the peer of the BGP session.  The
      format is the same as defined for the Adj-SID in
      [I-D.gredler-idr-bgp-ls-segment-routing-extension].  Suggested
      codepoint value: 1036

      Peer-Set-SID: the SID representing the group the peer is part of.
      The format is the same as defined for the Adj-SID in
      [I-D.gredler-idr-bgp-ls-segment-routing-extension].  Suggested
      codepoint value: 1037

   The value of the Adj-SID, Peer-SID and Peer-Set-SID Sub-TLVs SHOULD
   be persistent across router restart.

   The Peer-SID MUST be present when BGP-LS is used for the use case
   described in [I-D.filsfils-spring-segment-routing-central-epe] and
   MAY be omitted for other use cases.

   The Adj-SID and Peer-Set-SID SubTLVs MAY be present when BGP-LS is
   used for the use case described in
   [I-D.filsfils-spring-segment-routing-central-epe] and MAY be omitted
   for other use cases.

   In addition, BGP-LS Nodes and Link Attributes, as defined in
   [I-D.ietf-idr-ls-distribution]MAY be inserted in order to advertise
   the characteristics of the link.

5.  Peer Node and Peer Adjacency Segments

   In this section the following Peer Segments are defined:

      Peer Node Segment (Peer Node SID)

      Peer Adjacency Segment (Peer Adj SID)

      Peer Set Segment (Peer Set SID)

5.1.  Peer Node Segment

   The Peer Node Segment describes the BGP session peer (neighbor).  It
   MUST be present when describing an EPE topology as defined in
   [I-D.filsfils-spring-segment-routing-central-epe].  The Peer Node



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   Segment is encoded within the BGP-LS Link NLRI specified in
   Section 4.

   The Peer Node Segment is a local segment.  At the BGP node
   advertising it, its semantic is:

   o  SR header operation: NEXT (as defined in
      [I-D.ietf-spring-segment-routing]).

   o  Next-Hop: the connected peering node to which the segment is
      related.

   The Peer Node Segment is advertised with a Link NLRI, where:

   o  Local Node Descriptors contains

     Local BGP Router ID of the EPE enabled egress PE.
     Local ASN.
     BGP-LS Identifier.

   o  Remote Node Descriptors contains

     Peer BGP Router ID (i.e.: the peer BGP ID used in the BGP session).
     Peer ASN.

   o  Link Descriptors Sub-TLVs, as defined in
      [I-D.ietf-idr-ls-distribution], contain the addresses used by the
      BGP session:

      *  IPv4 Interface Address (Sub-TLV 259) contains the BGP session
         IPv4 local address.

      *  IPv4 Neighbor Address (Sub-TLV 260) contains the BGP session
         IPv4 peer address.

      *  IPv6 Interface Address (Sub-TLV 261) contains the BGP session
         IPv6 local address.

      *  IPv6 Neighbor Address (Sub-TLV 262) contains the BGP session
         IPv6 peer address.

   o  Link Attribute contains the Peer-SID TLV as defined in
      Section 4.3.

   o  In addition, BGP-LS Link Attributes, as defined in
      [I-D.ietf-idr-ls-distribution], MAY be inserted in order to
      advertise the characteristics of the link.




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5.2.  Peer Adjacency Segment

   The Peer Adjacency Segment is a local segment.  At the BGP node
   advertising it, its semantic is:

   o  SR header operation: NEXT (as defined in
      [I-D.ietf-spring-segment-routing]).

   o  Next-Hop: the interface peer address.

   The Peer Adjacency Segment is advertised with a Link NLRI, where:

   o  Local Node Descriptors contains

     Local BGP Router ID of the EPE enabled egress PE.
     Local ASN.
     BGP-LS Identifier.

   o  Remote Node Descriptors contains

     Peer BGP Router ID (i.e.: the peer BGP ID used in the BGP session).
     Peer ASN.

   o  Link Descriptors Sub-TLVs, as defined in
      [I-D.ietf-idr-ls-distribution], contain the addresses used by the
      BGP session:

      *  IPv4 Interface Address (Sub-TLV 259) contains the IPv4 address
         of the local interface used by the BGP session.

      *  IPv4 Neighbor Address (Sub-TLV 260) contains the IPv4 address
         of the peer interface used by the BGP session.

      *  IPv6 Interface Address (Sub-TLV 261) contains the IPv6 address
         of the local interface used by the BGP session.

      *  IPv6 Neighbor Address (Sub-TLV 262) contains the IPv6 address
         of the peer interface used by the BGP session.

   o  Link attribute used with the Peer Adjacency SID contains the Adj-
      SID TLV as defined in Section 4.3.

   In addition, BGP-LS Link Attributes, as defined in
   [I-D.ietf-idr-ls-distribution], MAY be inserted in order to advertise
   the characteristics of the link.






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5.3.  Peer Set Segment

   The Peer Set Segment is a local segment.  At the BGP node advertising
   it, its semantic is:

   o  SR header operation: NEXT (as defined in
      [I-D.ietf-spring-segment-routing]).

   o  Next-Hop: load balance across any connected interface to any peer
      in the related set.

   The Peer Set Segment is advertised within a Link NLRI (describing a
   Peer Node Segment or a Peer Adjacency segment) as a BGP-LS attribute.

   The Peer Set Attribute contains the Peer-Set-SID TLV, defined in
   Section 4.3 identifying the set of which the Peer Node Segment or
   Peer Adjacency Segment is a member.

6.  Illustration

6.1.  Reference Diagram

   The following reference diagram is used throughout this document.
   The solution is described for IPv4 with MPLS-based segments.

                    +------+
                    |      |
                +---D      F
   +---------+ /    | AS 2 |\  +------+
   |    X    |/     +------+ \ |   Z  |---L/8
   A         C---+            \|      |
   |         |\\  \  +------+ /| AS 4 |---M/8
   |   AS1   | \\  +-H      |/ +------+
   |         |  \\   |      G
   +----P----+   +===E AS 3 |
        |             +--Q---+
        |                |
        +----------------+

                        Figure 1: Reference Diagram

   IPv4 addressing:

   o  C's interface to D: 1.0.1.1/24, D's interface: 1.0.1.2/24

   o  C's interface to H: 1.0.2.1/24, H's interface: 1.0.2.2/24

   o  C's upper interface to E: 1.0.3.1/24, E's interface: 1.0.3.2/24



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   o  C's lower interface to E: 1.0.4.1/24, E's interface: 1.0.4.2/24

   o  Loopback of E used for eBGP multi-hop peering to C: 1.0.5.2/32

   o  C's loopback is 3.3.3.3/32 with SID 64

   BGP Router-IDs are C, D, H and E.

   o  C's BGP Router-ID: 3.3.3.3

   o  D's BGP Router-ID: 4.4.4.4

   o  E's BGP Router-ID: 5.5.5.5

   o  H's BGP Router-ID: 6.6.6.6

   C's BGP peering:

   o  Single-hop eBGP peering with neighbor 1.0.1.2 (D)

   o  Single-hop eBGP peering with neighbor 1.0.2.2 (H)

   o  Multi-hop eBGP peering with E on ip address 1.0.5.2 (E)

   C's resolution of the multi-hop eBGP session to E:

   o  Static route 1.0.5.2/32 via 1.0.3.2

   o  Static route 1.0.5.2/32 via 1.0.4.2

   Node C configuration is such that:

   o  A Peer Node segment is allocated to each peer (D, H and E).

   o  An Adjacency segment is defined for each recursing interface to a
      multi-hop peer (CE upper and lower interfaces).

   o  A Peer Set segment is defined to include all peers in AS3 (peers H
      and E).

   Local BGP-LS Identifier in router C is set to 10000.

   The Link NLRI Type is used in order to encode C's connectivity. the
   Link NLRI uses the new Protocol-ID value (to be assigned by IANA).







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6.1.1.  Peer Node Segment for Node D

   Descriptors:

   o  Local Node Descriptors (BGP Router-ID, local ASN, BGP-LS
      Identifier): 3.3.3.3 , AS1, 10000

   o  Remote Node Descriptors (BGP Router-ID, peer ASN): 4.4.4.4, AS2

   o  Link Descriptors (BGP session IPv4 local address, BGP session IPv4
      neighbor address): 1.0.1.1, 1.0.1.2

   Attributes:

   o  Peer-SID: 1012

   o  Link Attributes: see section 3.3.2 of
      [I-D.ietf-idr-ls-distribution]

6.1.2.  Peer Node Segment for Node H

   Descriptors:

   o  Local Node Descriptors (BGP Router-ID, ASN, BGPL Identifier):
      3.3.3.3 , AS1, 10000

   o  Remote Node Descriptors (BGP Router-ID ASN): 6.6.6.6, AS3

   o  Link Descriptors (BGP session IPv4 local address, BGP session IPv4
      peer address): 1.0.2.1, 1.0.2.2

   Attributes:

   o  Peer-SID: 1022

   o  Peer-Set-SID: 1060

   o  Link Attributes: see section 3.3.2 of
      [I-D.ietf-idr-ls-distribution]

6.1.3.  Peer Node Segment for Node E

   Descriptors:

   o  Local Node Descriptors (BGP Router-ID, ASN, BGP-LS Identifier):
      3.3.3.3 , AS1, 10000

   o  Remote Node Descriptors (BGP Router-ID, ASN): 5.5.5.5, AS3



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   o  Link Descriptors (BGP session IPv4 local address, BGP session IPv4
      peer address): 3.3.3.3, 1.0.5.2

   Attributes:

   o  Peer-SID: 1052

   o  Peer-Set-SID: 1060

6.1.4.  Peer Adj Segment for Node E, Link 1

   Descriptors:

   o  Local Node Descriptors (BGP Router-ID, ASN, BGP-LS Identifier):
      3.3.3.3 , AS1, 10000

   o  Remote Node Descriptors (BGP Router-ID, ASN): 5.5.5.5, AS3

   o  Link Descriptors (IPv4 local interface address, IPv4 peer
      interface address): 1.0.3.1 , 1.0.3.2

   Attributes:

   o  Adj-SID: 1032

   o  LinkAttributes: see section 3.3.2 of
      [I-D.ietf-idr-ls-distribution]

6.1.5.  Peer Adj Segment for Node E, Link 2

   Descriptors:

   o  Local Node Descriptors (BGP Router-ID, ASN, BGP-LS Identifier):
      3.3.3.3 , AS1, 10000

   o  Remote Node Descriptors (BGP Router-ID, ASN): 5.5.5.5, AS3

   o  Link Descriptors (IPv4 local interface address, IPv4 peer
      interface address): 1.0.4.1 , 1.0.4.2

   Attributes:

   o  Adj-SID: 1042

   o  LinkAttributes: see section 3.3.2 of
      [I-D.ietf-idr-ls-distribution]





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7.  BGP-LS EPE TLV/Sub-TLV Code Points Summary

   The following table contains the TLVs/Sub-TLVs defined in this
   document.

     +---------------------+--------------------------+-------------+
     | Suggested Codepoint | Description              | Defined in: |
     +---------------------+--------------------------+-------------+
     |          7          | Protocol-ID              | Section 4   |
     |         516         | BGP Router ID            | Section 4.1 |
     |         517         | BGP Confederation Member | Section 4.1 |
     |         1036        | Peer-SID                 | Section 4.3 |
     |         1037        | Peer-Set-SID             | Section 4.3 |
     +---------------------+--------------------------+-------------+

              Table 1: Summary Table of BGP-LS EPE Codepoints

8.  IANA Considerations

   This document defines:

      Two new Node Descriptors Sub-TLVs: BGP-Router-ID and BGP
      Confederation Member.

      A new Protocol-ID for EPE: BGP-EPE.

      Two new BGP-LS Attribute Sub-TLVs: the Peer-SID and the Peer-Set-
      SID.

   The codepoints are to be assigned by IANA.

9.  Manageability Considerations

   TBD

10.  Security Considerations

   [I-D.ietf-idr-ls-distribution] defines BGP-LS NLRIs to which the
   extensions defined in this document apply.

   The Security Section of [I-D.ietf-idr-ls-distribution] also applies
   to the:

      new Node Descriptors Sub-TLVs: BGP-Router ID and BGP Confederation
      Member;

      Peer-SID and Peer-Set-SID attributes




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   defined in this document.

11.  Acknowledgements

   The authors would like to thank Acee Lindem, Jakob Heitz, Howard Yang
   and Hannes Gredler for their feedback and comments.

12.  References

12.1.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

   [RFC4271]  Rekhter, Y., Li, T., and S. Hares, "A Border Gateway
              Protocol 4 (BGP-4)", RFC 4271, January 2006.

   [RFC5065]  Traina, P., McPherson, D., and J. Scudder, "Autonomous
              System Confederations for BGP", RFC 5065, August 2007.

   [RFC6286]  Chen, E. and J. Yuan, "Autonomous-System-Wide Unique BGP
              Identifier for BGP-4", RFC 6286, June 2011.

12.2.  Informative References

   [I-D.filsfils-spring-segment-routing-central-epe]
              Filsfils, C., Previdi, S., Patel, K., Aries, E.,
              shaw@fb.com, s., Ginsburg, D., and D. Afanasiev, "Segment
              Routing Centralized Egress Peer Engineering", draft-
              filsfils-spring-segment-routing-central-epe-03 (work in
              progress), January 2015.

   [I-D.gredler-idr-bgp-ls-segment-routing-extension]
              Gredler, H., Ray, S., Previdi, S., Filsfils, C., Chen, M.,
              and J. Tantsura, "BGP Link-State extensions for Segment
              Routing", draft-gredler-idr-bgp-ls-segment-routing-
              extension-02 (work in progress), October 2014.

   [I-D.ietf-idr-ls-distribution]
              Gredler, H., Medved, J., Previdi, S., Farrel, A., and S.
              Ray, "North-Bound Distribution of Link-State and TE
              Information using BGP", draft-ietf-idr-ls-distribution-10
              (work in progress), January 2015.








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   [I-D.ietf-spring-segment-routing]
              Filsfils, C., Previdi, S., Bashandy, A., Decraene, B.,
              Litkowski, S., Horneffer, M., Shakir, R., Tantsura, J.,
              and E. Crabbe, "Segment Routing Architecture", draft-ietf-
              spring-segment-routing-01 (work in progress), February
              2015.

Authors' Addresses

   Stefano Previdi (editor)
   Cisco Systems, Inc.
   Via Del Serafico, 200
   Rome  00142
   Italy

   Email: sprevidi@cisco.com


   Clarence Filsfils
   Cisco Systems, Inc.
   Brussels
   BE

   Email: cfilsfil@cisco.com


   Saikat Ray
   Individual Contributor

   Email: raysaikat@gmail.com


   Keyur Patel
   Cisco Systems, Inc.
   170, West Tasman Drive
   San Jose, CA  95134
   US

   Email: keyupate@cisco.com


   Jie Dong
   Huawei Technologies
   Huawei Campus, No. 156 Beiqing Rd.
   Beijing  100095
   China

   Email: jie.dong@huawei.com



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

   Email: mach.chen@huawei.com












































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