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Versions: (draft-previdi-idr-bgpls-segment-routing-epe) 00 01 02 03 04 05 06 07 08 09 10 11 12

Network Working Group                                    S. Previdi, Ed.
Internet-Draft                                               C. Filsfils
Intended status: Standards Track                     Cisco Systems, Inc.
Expires: October 30, 2017                                       K. Patel
                                                            Arrcus, Inc.
                                                                  S. Ray
                                                  Individual Contributor
                                                                 J. Dong
                                                     Huawei Technologies
                                                          April 28, 2017


   BGP-LS extensions for Segment Routing BGP Egress Peer Engineering
              draft-ietf-idr-bgpls-segment-routing-epe-12

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 peering
   node topology information (including its peers, interfaces and
   peering ASs) in a way that is exploitable in order to compute
   efficient BGP Peering 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
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at http://datatracker.ietf.org/drafts/current/.



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   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
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   This Internet-Draft will expire on October 30, 2017.

Copyright Notice

   Copyright (c) 2017 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
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   publication of this document.  Please review these documents
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   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  . . . . . . . . . . . . . . . . . . . .   4
   4.  Link NLRI for BGP-EPE Connectivity Description  . . . . . . .   5
     4.1.  BGP Router ID and Member ASN  . . . . . . . . . . . . . .   5
     4.2.  Mandatory BGP-EPE Node Descriptors  . . . . . . . . . . .   6
     4.3.  Optional BGP-EPE Node Descriptors . . . . . . . . . . . .   7
     4.4.  Link Attributes . . . . . . . . . . . . . . . . . . . . .   7
   5.  Peer-Node and Peer-Adj SIDs . . . . . . . . . . . . . . . . .   9
     5.1.  Peer-Node-SID . . . . . . . . . . . . . . . . . . . . . .  10
     5.2.  Peer-Adj-SID  . . . . . . . . . . . . . . . . . . . . . .  11
     5.3.  Peer-Set-SID  . . . . . . . . . . . . . . . . . . . . . .  12
   6.  Illustration  . . . . . . . . . . . . . . . . . . . . . . . .  12
     6.1.  Reference Diagram . . . . . . . . . . . . . . . . . . . .  12
     6.2.  Peer-Node-SID for Node D  . . . . . . . . . . . . . . . .  14
     6.3.  Peer-Node-SID for Node F  . . . . . . . . . . . . . . . .  15
     6.4.  Peer-Node-SID for Node E  . . . . . . . . . . . . . . . .  15
     6.5.  Peer-Adj-SID for Node E, Link 1 . . . . . . . . . . . . .  15
     6.6.  Peer-Adj-SID for Node E, Link 2 . . . . . . . . . . . . .  16
   7.  Implementation Status . . . . . . . . . . . . . . . . . . . .  16
   8.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  17
     8.1.  New BGP-LS Protocol-ID  . . . . . . . . . . . . . . . . .  17
     8.2.  Node Descriptors and Link Attribute TLVs  . . . . . . . .  18
   9.  Manageability Considerations  . . . . . . . . . . . . . . . .  18



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   10. Security Considerations . . . . . . . . . . . . . . . . . . .  19
   11. Contributors  . . . . . . . . . . . . . . . . . . . . . . . .  19
   12. Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  19
   13. References  . . . . . . . . . . . . . . . . . . . . . . . . .  19
     13.1.  Normative References . . . . . . . . . . . . . . . . . .  19
     13.2.  Informative References . . . . . . . . . . . . . . . . .  20
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  21

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 with segment identifiers
   (SID).  A SID 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 peering
   node topology information (including its peers, interfaces and
   peering ASs) in a way that is exploitable in order to compute
   efficient BGP Egress Peer Engineering (BGP-EPE) policies and
   strategies.

   This document defines the BGP-LS extensions required to support the
   Peer Node SID describing the BGP session between two nodes, the Peer
   Adjacency SID describing the link (one or more) that is used by the
   BGP session and the Peer Set SID describing an arbitrary set of
   sessions or links between the local BGP node and its peers.  These
   SIDs represent the segments defined in
   [I-D.ietf-spring-segment-routing-central-epe].

   While an egress point topology usually refers to eBGP sessions
   between external peers, there's nothing in the extensions defined in
   this document that would prevent the use of these extensions in the
   context of iBGP sessions.

2.  Segment Routing Documents

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






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   The Segment Routing BGP Egress Peer Engineering (BGP-EPE)
   architecture is described in
   [I-D.ietf-spring-segment-routing-central-epe].

3.  BGP Peering Segments

   As defined in [I-D.ietf-spring-segment-routing-central-epe], a BGP-
   EPE enabled Egress PE node MAY advertise SIDs corresponding to its
   attached peers.  These SIDs are called BGP peering segments or BGP
   Peering SIDs.  In case of eBGP, they enable the expression of source-
   routed inter-domain paths.

   An ingress border router of an AS may compose a list of SIDs 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-EPE policy applied at an ingress PE involves two SIDs: the Node
   SID of the chosen egress PE and then the BGP Peering SID for the
   chosen egress PE peer or peering interface.

   This document defines the BGP-LS extensions for the BGP-EPE Peering
   SIDs:

   o  Peer Node Segment (Peer-Node-SID)

   o  Peer Adjacency Segment (Peer-Adj-SID)

   o  Peer Set Segment (Peer-Set-SID)

   that have been defined in
   [I-D.ietf-spring-segment-routing-central-epe].

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

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

   o  One Peer-Node-SID MUST be present.

   o  One or more Peer-Adj-SID MAY be present.

   o  Each of the Peer-Node-SID Peer-Adj-SID MAY use the same Peer-Set-
      SID.




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   While an egress point topology usually refers to eBGP sessions
   between external peers, there's nothing in the extensions defined in
   this document that would prevent the use of these extensions in the
   context of iBGP sessions.

4.  Link NLRI for BGP-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 NLRI Type (defined
   in [RFC7752]) is used.  A new Protocol-ID is used: BGP (codepoint 7
   assigned by IANA (Section 8) from the registry "BGP-LS Protocol-
   IDs").

   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 [RFC7752].  The
   Link NLRI Type uses descriptors and attributes already defined in
   [RFC7752] in addition to new TLVs defined in the following sections
   of this document.

   The extensions defined in this document apply to both internal and
   external BGP-LS EPE advertisements.

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

      Node Descriptors and Link Descriptors are defined in [RFC7752].

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):



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         Type: 516 (assigned by IANA (Section 8) from the registry "BGP-
         LS Node Descriptor, Link Descriptor, Prefix Descriptor, and
         Attribute TLVs").

         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: 517 (assigned by IANA (Section 8) from the registry "BGP-
         LS Node Descriptor, Link Descriptor, Prefix Descriptor, and
         Attribute TLVs").

         Length: 4 octets

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

4.2.  Mandatory BGP-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 capable node.

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

   o  BGP-LS Identifier.

   It has to be noted that [RFC6286] (section 2.1) requires the BGP
   identifier (router-id) to be unique within an Autonomous System.
   Therefore, the <ASN, BGP identifier> tuple is globally unique.

   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.







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4.3.  Optional BGP-EPE Node Descriptors

   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 [RFC7752].

   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 [RFC7752].

4.4.  Link Attributes

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

   +----------+---------------------------+----------+
   | TLV Code | Description               |   Length |
   |  Point   |                           |          |
   +----------+---------------------------+----------+
   |    1101  | Peer Node Segment         | variable |
   |          | Identifier (Peer-Node-SID)|          |
   |    1102  | Peer Adjacency Segment    | variable |
   |          | Identifier (Peer-Adj-SID) |          |
   |    1103  | Peer Set Segment          | variable |
   |          | Identifier (Peer-Set-SID) |          |
   +----------+---------------------------+----------+

               Figure 1: BGP-LS TLV code points for BGP-EPE

   Peer-Node-SID, Peer-Adj-SID and Peer-Set-SID have all the same format
   defined here below:












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

   where:

                                 Figure 2

   o  Type: 1101 or 1102 or 1103 (assigned by IANA (Section 8) from the
      registry "BGP-LS Node Descriptor, Link Descriptor, Prefix
      Descriptor, and Attribute TLVs").

   o  Length: variable.

   o  Flags: one octet of flags used when advertising a Peer-Adj-SID
      (Peer-Node and Peer-Set SIDs don't have flags defined).  The
      following Peer-Adj-SID flags have been defined:

    0 1 2 3 4 5 6 7
   +-+-+-+-+-+-+-+-+
   |V|L|           |
   +-+-+-+-+-+-+-+-+

   where:

      *  V-Flag: Value flag.  If set, then the Adj-SID carries a value.
         By default the flag is SET.

      *  L-Flag: Local Flag.  If set, then the value/index carried by
         the Adj-SID has local significance.  By default the flag is
         SET.

      *  Other bits: MUST be zero when originated and ignored when
         received.

   o  Weight: 1 octet.  The value represents the weight of the SID for
      the purpose of load balancing.  An example use of the weight is
      described in [I-D.ietf-spring-segment-routing].

   o  SID/Index/Label.  According to the TLV length and to the V and L
      flags settings, it contains either:




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      *  A 3 octet local label where the 20 rightmost bits are used for
         encoding the label value.  In this case the V and L flags MUST
         be set.

      *  A 4 octet index defining the offset in the SRGB (Segment
         Routing Global Block as defined in
         [I-D.ietf-spring-segment-routing] advertised by this router.
         In this case, the SRGB MUST be advertised using the extensions
         defined in [I-D.ietf-idr-bgp-ls-segment-routing-ext].

      *  A 16 octet IPv6 address.  In this case the V flag MUST be set.
         The L flag MUST be unset if the IPv6 address is globally
         unique.

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

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

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

   In addition, BGP-LS Nodes and Link Attributes, as defined in
   [RFC7752] MAY be inserted in order to advertise the characteristics
   of the link.

5.  Peer-Node and Peer-Adj SIDs

   In this section the following SIDs are defined:

      Peer Node Segment Identifier (Peer-Node-SID)

      Peer Adjacency Segment Identifier (Peer-Adj-SID)

      Peer Set Segment Identifier (Peer-Set-SID)

   The Peer-Node, Peer-Adj and Peer-Set SIDs can be either a local or a
   global (depending on the setting of the V and L flags defined in
   Figure 2.  For example, when BGP-EPE is used in the context of a SR
   network over the IPv6 dataplane, it is likely the case that the IPv6
   addresses used as SIDs will be global.






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5.1.  Peer-Node-SID

   The Peer-Node-SID describes the BGP session peer (neighbor).  It MUST
   be present when describing a BGP-EPE topology as defined in
   [I-D.ietf-spring-segment-routing-central-epe].  The Peer-Node-SID is
   encoded within the BGP-LS Link NLRI specified in Section 4.

   The Peer-Node-SID, at the BGP node advertising it, has the following
   semantic:

   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-SID is advertised with a Link NLRI, where:

   o  Local Node Descriptors contains

     Local BGP Router-ID of the BGP-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 [RFC7752], 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-Node-SID TLV as defined in
      Section 4.4.





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   o  In addition, BGP-LS Link Attributes, as defined in [RFC7752], MAY
      be inserted in order to advertise the characteristics of the link.

5.2.  Peer-Adj-SID

   The Peer-Adj-SID, at the BGP node advertising it, has the following
   semantic:

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

   o  Next-Hop: the interface peer address.

   The Peer-Adj-SID is advertised with a Link NLRI, where:

   o  Local Node Descriptors contains

     Local BGP Router-ID of the BGP-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 [RFC7752], MUST contain
      the following TLVs:

      *  Link Local/Remote Identifiers (Sub-TLV 258) contains the
         4-octet Link Local Identifier followed by the 4-octet value 0
         indicating the Link Remote Identifier in unknown [RFC5307].

   o  In addition, Link Descriptors Sub-TLVs, as defined in [RFC7752],
      MAY contain the following TLVs:

      *  IPv4 Interface Address (Sub-TLV 259) contains the address of
         the local interface through which the BGP session is
         established.

      *  IPv6 Interface Address (Sub-TLV 261) contains the address of
         the local interface through which the BGP session is
         established.

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





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      *  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-Adj-SID contains the TLV as
      defined in Section 4.4.

   In addition, BGP-LS Link Attributes, as defined in [RFC7752], MAY be
   inserted in order to advertise the characteristics of the link.

5.3.  Peer-Set-SID

   The Peer-Set-SID, at the BGP node advertising it, has the following
   semantic:

   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-SID 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 4.4 identifying the set of which the Peer-Node-SID or Peer-
   Adj-SID is a member.

6.  Illustration

6.1.  Reference Diagram

   The following reference diagram is used throughout this document.
   The solution is illustrated for IPv6 with MPLS-based SIDs and the
   BGP-EPE topology is based on eBGP sessions between external peers.

   As stated in Section 3, the solution illustrated hereafter is equally
   applicable to an iBGP session topology.  In other words, the solution
   also applies to the case where C, D, F, and E are in the same AS and
   run iBGP sessions between each other.












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

                        Figure 3: Reference Diagram

   IP addressing:

   o  C's IP address of interface to D: 2001:db8:cd::c/64, D's
      interface: 2001:db8:cd::d/64

   o  C's IP address of interface to F: 2001:db8:cf::c/64, F's
      interface: 2001:db8:cf::f/64

   o  C's IP address of upper interface to E: 2001:db8:ce1::c/64, E's
      interface: 2001:db8:ce1::e

   o  C's local identifier of upper interface to E: 0.0.0.1.0.0.0.0

   o  C's IP address of lower interface to E: 2001:db8:ce2::c, E's
      interface: 2001:db8:ce2::e

   o  C's local identifier of lower interface to E: 0.0.0.2.0.0.0.0

   o  Loopback of E used for eBGP multi-hop peering to C:
      2001:db8:e::e/128

   o  C's loopback is 2001:db8:c::c/128 with SID 64

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

   o  C's BGP Router-ID: 192.0.2.3

   o  D's BGP Router-ID: 192.0.2.4

   o  E's BGP Router-ID: 192.0.2.5

   o  F's BGP Router-ID: 192.0.2.6



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   C's BGP peering:

   o  Single-hop eBGP peering with neighbor 2001:db8:cd::d (D)

   o  Single-hop eBGP peering with neighbor 2001:db8:cf::f (F)

   o  Multi-hop eBGP peering with E on ip address 2001:db8:e::e (E)

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

   o  Static route 2001:db8:e::e/128 via 2001:db8:ce1::e

   o  Static route 2001:db8:e::e/128 via 2001:db8:ce2::e

   Node C configuration is such that:

   o  A Peer-Node-SID is allocated to each peer (D, F and E).

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

   o  A Peer-Set-SID is defined to include all peers in AS3 (peers F 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 Protocol-ID value (to be assigned by IANA)

   Once the BGP-LS update is originated by C, it may be advertised to
   internal (iBGP) as well as external (eBGP) neighbors supporting the
   BGP-LS EPE extensions defined in this document.

6.2.  Peer-Node-SID for Node D

   Descriptors:

   o  Local Node Descriptors (BGP Router-ID, local ASN, BGP-LS
      Identifier): 192.0.2.3, AS1, 10000

   o  Remote Node Descriptors (BGP Router-ID, peer ASN): 192.0.2.4, AS2

   o  Link Descriptors (BGP session IPv6 local address, BGP session IPv6
      neighbor address): 2001:db8:cd::c, 2001:db8:cd::d

   Attributes:

   o  Peer-Node-SID: 1012



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   o  Link Attributes: see section 3.3.2 of [RFC7752]

6.3.  Peer-Node-SID for Node F

   Descriptors:

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

   o  Remote Node Descriptors (BGP Router-ID ASN): 192.0.2.6, AS3

   o  Link Descriptors (BGP session IPv6 local address, BGP session IPv6
      peer address): 2001:db8:cf::c, 2001:db8:cf::f

   Attributes:

   o  Peer-Node-SID: 1022

   o  Peer-Set-SID: 1060

   o  Link Attributes: see section 3.3.2 of [RFC7752]

6.4.  Peer-Node-SID for Node E

   Descriptors:

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

   o  Remote Node Descriptors (BGP Router-ID, ASN): 192.0.2.5, AS3

   o  Link Descriptors (BGP session IPv6 local address, BGP session IPv6
      peer address): 2001:db8:c::c, 2001:db8:e::e

   Attributes:

   o  Peer-Node-SID: 1052

   o  Peer-Set-SID: 1060

6.5.  Peer-Adj-SID for Node E, Link 1

   Descriptors:

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

   o  Remote Node Descriptors (BGP Router-ID, ASN): 192.0.2.5, AS3



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   o  Link Descriptors (local interface identifier, IPv6 peer interface
      address): 0.0.0.1.0.0.0.0 , 2001:db8:ce1::e

   Attributes:

   o  Peer-Adj-SID: 1032

   o  LinkAttributes: see section 3.3.2 of [RFC7752]

6.6.  Peer-Adj-SID for Node E, Link 2

   Descriptors:

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

   o  Remote Node Descriptors (BGP Router-ID, ASN): 192.0.2.5, AS3

   o  Link Descriptors (local interface identifier, IPv6 peer interface
      address): 0.0.0.2.0.0.0.0 , 2001:db8:ce2::e

   Attributes:

   o  Peer-Adj-SID: 1042

   o  LinkAttributes: see section 3.3.2 of [RFC7752]

7.  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



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   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 following values:

                 +---------------------------------------+
                 |  Codepoint | Description              |
                 +---------------------------------------+
                 |       7    | Protocol-ID BGP          |
                 |     516    | BGP Router-ID            |
                 |     517    | BGP Confederation Member |
                 |    1101    | Peer-Node-SID            |
                 |    1102    | Peer-Adj-SID             |
                 |    1103    | Peer-Set-SID             |
                 +------------+--------------------------+

   IANA has now confirmed the assignment of the above coidepoints.
   SeeSection 8.

8.  IANA Considerations

   This document defines:

      A new Protocol-ID: BGP.  The codepoint is from the "BGP-LS
      Protocol-IDs" registry.

      Two new TLVs: BGP-Router-ID and BGP Confederation Member.  The
      codepoints are in the "BGP-LS Node Descriptor, Link Descriptor,
      Prefix Descriptor, and Attribute TLVs" registry.

      Three new BGP-LS Attribute TLVs: Peer-Node-SID, Peer-Adj-SID and
      Peer-Set-SID.  The codepoints are in the "BGP-LS Node Descriptor,
      Link Descriptor, Prefix Descriptor, and Attribute TLVs" registry.

8.1.  New BGP-LS Protocol-ID

   This document defines a new value in the registry "BGP-LS Protocol-
   IDs":

             +----------------------------------------------+
             |  Codepoint | Description | Status            |
             +----------------------------------------------+
             |    7       | BGP         | Assigned by IANA  |
             +----------------------------------------------+



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8.2.  Node Descriptors and Link Attribute TLVs

   This document defines 5 new TLVs in the registry "BGP-LS Node
   Descriptor, Link Descriptor, Prefix Descriptor, and Attribute TLVs":

   o  Two new node descriptor TLVs

   o  Three new link attribute TLVs

   All the new 5 codepoints are in the same registry: "BGP-LS Node
   Descriptor, Link Descriptor, Prefix Descriptor, and Attribute TLVs".
   However, the registry is organized in ranges (node descriptors, link
   descriptors, node attributes, link attributes).

   The following new Node Descriptors TLVs are defined:

       +-----------------------------------------------------------+
       |  Codepoint | Description              | Status            |
       +-----------------------------------------------------------+
       |    516     | BGP Router-ID            | Assigned by IANA  |
       |    517     | BGP Confederation Member | Assigned by IANA  |
       +------------+----------------------------------------------+

   The following new Link Attribute TLVs are defined:

       +-----------------------------------------------------------+
       |  Codepoint | Description              | Status            |
       +-----------------------------------------------------------+
       |    1101    | Peer-Node-SID            | Assigned by IANA  |
       |    1102    | Peer-Adj-SID             | Assigned by IANA  |
       |    1103    | Peer-Set-SID             | Assigned by IANA  |
       +------------+----------------------------------------------+

9.  Manageability Considerations

   The BGP-LS ([RFC7752]) extensions that are described in this document
   consist of additional BGP-LS descriptors and TLVs that will follow
   the same manageability functions of BGP-LS, described in [RFC7752].

   The operator MUST be capable of configuring, enabling, disabling the
   advertisement of each of the Peer-Node-SID, Peer-Adj-SID and Peer-
   Set-SID as well as to control which information is advertised to
   which internal or external peer.  This is not different from what is
   required by a BGP speaker in terms of information origination and
   advertisement.  In addition, the advertisement of EPE information
   MUST conform to standard BGP advertisement and propagation rules
   (iBGP, eBGP, Route-Reflectors, Confederations).




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10.  Security Considerations

   [RFC7752] defines BGP-LS NLRIs to which the extensions defined in
   this document apply.

   The Security Section of [RFC7752] also applies to:

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

   o  New BGP-LS Attributes TLVs: Peer-Node-SID, Peer-Adj-SID and Peer-
      Set-SID.

   The extensions defined in this document do not introduce any
   additional security aspects of BGP-LS.

11.  Contributors

   Mach (Guoyi) Chen
   Huawei Technologies
   China

   Email: mach.chen@huawei.com

   Acee Lindem
   Cisco Systems Inc.
   US

   Email: acee@cisco.com

12.  Acknowledgements

   The authors would like to thank Jakob Heitz, Howard Yang, Hannes
   Gredler, Peter Psenak, Ketan Jivan Talaulikar, Arjun Sreekantiah and
   Bruno Decraene for their feedback and comments.

13.  References

13.1.  Normative References

   [I-D.ietf-spring-segment-routing]
              Filsfils, C., Previdi, S., Decraene, B., Litkowski, S.,
              and R. Shakir, "Segment Routing Architecture", draft-ietf-
              spring-segment-routing-11 (work in progress), February
              2017.






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   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <http://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,
              <http://www.rfc-editor.org/info/rfc4271>.

   [RFC5065]  Traina, P., McPherson, D., and J. Scudder, "Autonomous
              System Confederations for BGP", RFC 5065,
              DOI 10.17487/RFC5065, August 2007,
              <http://www.rfc-editor.org/info/rfc5065>.

   [RFC5307]  Kompella, K., Ed. and Y. Rekhter, Ed., "IS-IS Extensions
              in Support of Generalized Multi-Protocol Label Switching
              (GMPLS)", RFC 5307, DOI 10.17487/RFC5307, October 2008,
              <http://www.rfc-editor.org/info/rfc5307>.

   [RFC6286]  Chen, E. and J. Yuan, "Autonomous-System-Wide Unique BGP
              Identifier for BGP-4", RFC 6286, DOI 10.17487/RFC6286,
              June 2011, <http://www.rfc-editor.org/info/rfc6286>.

13.2.  Informative References

   [I-D.ietf-idr-bgp-ls-segment-routing-ext]
              Previdi, S., Psenak, P., Filsfils, C., Gredler, H., Chen,
              M., and j. jefftant@gmail.com, "BGP Link-State extensions
              for Segment Routing", draft-ietf-idr-bgp-ls-segment-
              routing-ext-01 (work in progress), February 2017.

   [I-D.ietf-spring-segment-routing-central-epe]
              Filsfils, C., Previdi, S., Aries, E., and D. Afanasiev,
              "Segment Routing Centralized BGP Egress Peer Engineering",
              draft-ietf-spring-segment-routing-central-epe-05 (work in
              progress), March 2017.

   [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,
              <http://www.rfc-editor.org/info/rfc7752>.

   [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,
              <http://www.rfc-editor.org/info/rfc7942>.



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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


   Keyur Patel
   Arrcus, Inc.

   Email: Keyur@arrcus.com


   Saikat Ray
   Individual Contributor

   Email: raysaikat@gmail.com


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

   Email: jie.dong@huawei.com













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