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YANG data model for BGP Segment Routing Extensions
draft-deevi-spring-bgp-sr-yang-00

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This is an older version of an Internet-Draft whose latest revision state is "Expired".
Authors Krishna , Syed Kamran Raza , Kausik Majumdar , Bruno Decraene
Last updated 2020-09-28
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draft-deevi-spring-bgp-sr-yang-00
Spring Working Group                                            K. Deevi
Internet-Draft                                                   K. Raza
Intended status: Standards Track                                   Cisco
Expires: January 8, 2021                                     K. Majumdar
                                                                Comscope
                                                             B. Decraene
                                                                  Orange
                                                      September 27, 2020

           YANG data model for BGP Segment Routing Extensions
                  draft-deevi-spring-bgp-sr-yang-00

Abstract

   This document defines a YANG data model that can be used to configure
   and manage Segment Routing extensions in BGP.

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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   This Internet-Draft will expire on January 8, 2021.

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   Copyright (c) 2020 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

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   include Simplified BSD License text as described in Section 4.e of

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   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

   This document may contain material from IETF Documents or IETF
   Contributions published or made publicly available before November
   10, 2008.  The person(s) controlling the copyright in some of this
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   than English.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Requirements Language . . . . . . . . . . . . . . . . . .   3
   2.  BGP Segment Routing Yang model  . . . . . . . . . . . . . . .   3
     2.1.  Overview  . . . . . . . . . . . . . . . . . . . . . . . .   3
     2.2.  SR Prefix SID (SR MPLS) . . . . . . . . . . . . . . . . .   4
     2.3.  Egress Peer Engineering . . . . . . . . . . . . . . . . .   4
   3.  Yang Tree . . . . . . . . . . . . . . . . . . . . . . . . . .   4
     3.1.  SR Prefix Sid (SR MPLS) . . . . . . . . . . . . . . . . .   4
     3.2.  Egress Peer Engineering . . . . . . . . . . . . . . . . .   6
   4.  Yang Module . . . . . . . . . . . . . . . . . . . . . . . . .   8
   5.  Contributors  . . . . . . . . . . . . . . . . . . . . . . . .  16
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  16
   7.  Security Considerations . . . . . . . . . . . . . . . . . . .  16
   8.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  17
   9.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  17
     9.1.  Normative References  . . . . . . . . . . . . . . . . . .  17
     9.2.  Informative References  . . . . . . . . . . . . . . . . .  17
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  18

1.  Introduction

   YANG [RFC6020] is a data definition language that was introduced to
   define the contents of a conceptual data store that allows networked
   devices to be managed using NETCONF [RFC6241].  YANG is proving
   relevant beyond its initial confines, as bindings to other interfaces
   (e.g.  ReST) [RFC8040] and encodings other than XML (e.g.  JSON)
   [RFC7951] are being defined.  Furthermore, YANG data models can be
   used as the basis of implementation for other interfaces, such as CLI
   and programmatic APIs.

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   This document defines the YANG model for Segment Routing specific
   extensions in BGP.

1.1.  Requirements Language

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
   "OPTIONAL" in this document are to be interpreted as described in BCP
   14 [RFC2119] [RFC8174] when, and only when, they appear in all
   capitals, as shown here.

2.  BGP Segment Routing Yang model

2.1.  Overview

   Segment Routing (SR), as defined in [RFC8402], leverages the source
   routing paradigm where a node steers a packet through an ordered list
   of instructions, called segments.  SR, thus, allows enforcing a flow
   through any topological path and/or service chain while maintaining
   per-flow state only at the ingress nodes to the SR domain.

   When applied to ipv6 data-plane (i.e.  SRv6), the ordered set of
   instructions are realized via SRv6 SIDs.  The various functions and
   behaviors corresponding to network programming using SRv6 are
   specified in [I-D.ietf-spring-srv6-network-programming].

   This document defines Yang model for the Segment Routing extensions
   applicable for BGP as following:

   o  Prefix sid extensions in the context of SR MPLS, as described in
      [I-D.ietf-idr-bgp-prefix-sid].

   o  Egress Peer Engineering (EPE) as described in [I-D.ietf-spring-
      segment-routing-central-epe].

   The Yang extensions proposed in this model augment the base BGP model
   defined in [I-D.ietf-idr-bgp-model].

   Note: Base BGP model does not have a common structure for BGP RIB.
   The placeholder containers defined in this model can be removed once
   base BGP model has the BGP RIB structure.

   The modeling in this document complies with the Network Management
   Datastore Architecture (NMDA) [RFC8342].  The operational state data
   is combined with the associated configuration data in the same
   hierarchy [RFC8407].  When protocol states are retrieved from the
   NMDA operational state datastore, the returned states cover all

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   "config true" (rw) and "config false" (ro) nodes defined in the
   schema.

2.2.  SR Prefix SID (SR MPLS)

   Prefix SID attribute in BGP in the context of SR MPLS, carries the
   label index and SRGB block information.

   o  The configuration to attach the label index is modeled as a new
      route-policy set action.  BGP policy actions from the BGP policy
      module defined in base BGP yang model [I-D.ietf-idr-bgp-model] are
      augmented for this purpose.

   o  The configuration related to SR Mapping Server in the context of
      BGP prefix SID, is TBD.

   o  Prefix SID attribute received with the BGP route is modeled under
      BGP AF mode for select address families.  This information is
      applicable per route.

2.3.  Egress Peer Engineering

   Egress Peer Engineering (EPE) in the context of Segment Routing is
   described in [I-D.ietf-spring-segment-routing-central-epe].  EPE is
   enabled in the context of BGP neighbor session.  Three different
   types of EPE SIDs namely, Peer node SID, Peer adjacency SID and Peer
   set SID correspond to the segments required for source routed inter
   domain paths.  EPE SID(s) for each type above, can be statically
   configured or dynamically allocated by the node.  Further, FRR backup
   policy and backup SID can be specified per EPE.  The configuration
   and state for the EPE parameters is modeled by augmenting the
   neighbor container defined in the base BGP model
   [I-D.ietf-idr-bgp-model].  The configuration and the applied config
   state are applicable for neighbor-groups as well.

3.  Yang Tree

3.1.  SR Prefix Sid (SR MPLS)

module: ietf-bgp-sr
augment /rt:routing/rt:control-plane-protocols/rt:control-plane-protocol/bgp:bgp/bgp:global/bgp:afi-safis/bgp:afi-safi/bgp:ipv4-unicast:
   +--ro routes
      +--ro route* [prefix neighbor add-path-id]
         +--ro prefix         union
         +--ro neighbor       inet:ip-address
         +--ro add-path-id    uint32
augment /rt:routing/rt:control-plane-protocols/rt:control-plane-protocol/bgp:bgp/bgp:global/bgp:afi-safis/bgp:afi-safi/bgp:ipv6-unicast:
   +--ro routes

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      +--ro route* [prefix neighbor add-path-id]
         +--ro prefix         union
         +--ro neighbor       inet:ip-address
         +--ro add-path-id    uint32
augment /rt:routing/rt:control-plane-protocols/rt:control-plane-protocol/bgp:bgp/bgp:global/bgp:afi-safis/bgp:afi-safi/bgp:ipv4-labeled-unicast:
   +--ro routes
      +--ro route* [prefix neighbor add-path-id]
         +--ro prefix         union
         +--ro neighbor       inet:ip-address
         +--ro add-path-id    uint32
         +--ro prefix-sid
            +--ro label-index?       uint32
            +--ro originator-srgb
               +--ro srgb-ranges* [srgb-min srgb-max]
                  +--ro srgb-min    rt-types:mpls-label
                  +--ro srgb-max    rt-types:mpls-label
augment /rt:routing/rt:control-plane-protocols/rt:control-plane-protocol/bgp:bgp/bgp:global/bgp:afi-safis/bgp:afi-safi/bgp:ipv6-labeled-unicast:
   +--ro routes
      +--ro route* [prefix neighbor add-path-id]
         +--ro prefix         union
         +--ro neighbor       inet:ip-address
         +--ro add-path-id    uint32
         +--ro prefix-sid
            +--ro label-index?       uint32
            +--ro originator-srgb
               +--ro srgb-ranges* [srgb-min srgb-max]
                  +--ro srgb-min    rt-types:mpls-label
                  +--ro srgb-max    rt-types:mpls-label
augment /rt:routing/rt:control-plane-protocols/rt:control-plane-protocol/bgp:bgp/bgp:global/bgp:afi-safis/bgp:afi-safi/bgp:l3vpn-ipv4-unicast:
   +--ro routes
      +--ro route* [rd prefix neighbor add-path-id]
         +--ro rd             rt-types:route-distinguisher
         +--ro prefix         union
         +--ro neighbor       inet:ip-address
         +--ro add-path-id    uint32
augment /rt:routing/rt:control-plane-protocols/rt:control-plane-protocol/bgp:bgp/bgp:global/bgp:afi-safis/bgp:afi-safi/bgp:l3vpn-ipv6-unicast:
   +--ro routes
      +--ro route* [rd prefix neighbor add-path-id]
         +--ro rd             rt-types:route-distinguisher
         +--ro prefix         union
         +--ro neighbor       inet:ip-address
         +--ro add-path-id    uint32
augment /rpol:routing-policy/rpol:policy-definitions/rpol:policy-definition/rpol:statements/rpol:statement/rpol:actions/rpol:policy-result:
   +--rw set-label-index?   uint32

 ...

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3.2.  Egress Peer Engineering

   Egress Peer Engineering Yang Tree applicable to neighbor and peer-
   group containers

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module: ietf-bgp-sr

augment /rt:routing/rt:control-plane-protocols/rt:control-plane-protocol/bgp:bgp/bgp:neighbors/bgp:neighbor:
   +--rw egress-peer-engineering
      +--rw sid-allocation-type?   enumeration
      +--rw explicit-sid?          sid-type
      +--ro allocated-sid?         sid-type
      +--rw peer-set-name?         string
      +--rw backup
      |  +--ro active?        boolean
      |  +--rw backup-type?   enumeration
      |  +--rw backup-peer?   inet:ip-address
      |  +--rw backup-sid?    sid-type
      +--rw peer-adjacency* [first-hop-ipaddress]
         +--rw first-hop-ipaddress    inet:ip-address
         +--ro first-hop-interface?   string
         +--rw sid-allocation-type?   enumeration
         +--rw explicit-sid?          sid-type
         +--ro allocated-sid?         sid-type
         +--rw backup
            +--ro active?        boolean
            +--rw backup-type?   enumeration
            +--rw backup-peer?   inet:ip-address
            +--rw backup-sid?    sid-type
augment /rt:routing/rt:control-plane-protocols/rt:control-plane-protocol/bgp:bgp/bgp:peer-groups/bgp:peer-group:
   +--rw egress-peer-engineering
      +--rw sid-allocation-type?   enumeration
      +--rw explicit-sid?          sid-type
      +--ro allocated-sid?         sid-type
      +--rw peer-set-name?         string
      +--rw backup
      |  +--ro active?        boolean
      |  +--rw backup-type?   enumeration
      |  +--rw backup-peer?   inet:ip-address
      |  +--rw backup-sid?    sid-type
      +--rw peer-adjacency* [first-hop-ipaddress]
         +--rw first-hop-ipaddress    inet:ip-address
         +--ro first-hop-interface?   string
         +--rw sid-allocation-type?   enumeration
         +--rw explicit-sid?          sid-type
         +--ro allocated-sid?         sid-type
         +--rw backup
            +--ro active?        boolean
            +--rw backup-type?   enumeration
            +--rw backup-peer?   inet:ip-address
            +--rw backup-sid?    sid-type

...

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4.  Yang Module

<CODE BEGINS> file "ietf-bgp-sr@2019-07-07.yang"

module ietf-bgp-sr {

  namespace "urn:ietf:params:xml:ns:yang:ietf-bgp-sr";

  prefix ietf-bgp-sr ;

  import ietf-routing-types {
    prefix rt-types;
  }

  import ietf-routing {
    prefix "rt";
  }

  import ietf-inet-types {
    prefix inet;
  }

  import ietf-routing-policy {
    prefix rpol;
  }

  import ietf-bgp {
    prefix bgp;
  }

  import ietf-srv6-types {
    prefix srv6-types;
  }

  organization
     "IETF Spring Working Group";

  contact
     "Spring working group - spring@ietf.org";

  description
    "This YANG module defines a data model to configure and
     manage segment routing extensions in BGP.

     Terms and Acronyms

     AF : Address Family

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     BGP (bgp) : Border Gateway Protocol

     EPE : Egress Peer Engineering

     SR : Segment Routing

     SID : Segment Identifier

     VPN : Virtual Private Network

     VRF : Virtual Routing and Forwarding

    ";

  revision 2018-06-26 {
    description
      "Initial revision" ;
    reference "";

  }

  //
  // New identities and typedefs for SR extensions
  //

  // Sid type union
  typedef sid-type {
    type union {
      type rt-types:mpls-label;
      type srv6-types:srv6-sid;
    }
    description "Type definition for Segment Identifier. This is
                 a union type which can be either a SR MPLS SID in the
                 form of a label,  or a SRv6 SID in the form of
                 an IPv6 address.";
    reference "TBD";
  }

  //
  // SR Prefix SID related groupings
  //

  // Prefix SID attribute state in a route
  grouping sr-route-prefix-sid {
    description "SR Prefix SID attribute associated with BGP Route";
    container prefix-sid {
      description "Prefix SID attribute";
      leaf label-index {

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        type uint32;
        description "Label Index TLV carried with Prefix SID";
      }
      container originator-srgb {
        description "SRGB info of the originating node,
                     as signaled in the originator SRGB TLV";
        list srgb-ranges {
          key "srgb-min srgb-max";
          description "Concatenated ranges building the SRGB block";

          leaf srgb-min {
            type rt-types:mpls-label;
            description "Range min";
          }
          leaf srgb-max {
            type rt-types:mpls-label;
            description "Range max";
          }
        }
      }
    }
  }

  //
  // SR Egress Peer Engineering (EPE) related groupings
  //
  grouping epe-sid-alloc-mode {
    description "Common grouping for EPE mode and SID";
    leaf sid-allocation-type {
      type enumeration {
        enum EXPLICIT {
          description "EPE SID is configured";
        }
        enum DYNAMIC {
          description "EPE SID is generated by node";
        }
      }
      default "DYNAMIC";
      description "SID allocation mode specifies whether the EPE SID
                   is explicitly configured value, or a dynamically allocated
                   value by the node. This applicable for EPE peer SID, EPE peer
                   adjacency SID and Peer set SID, depending on the context
                   it is configured.";
    }

    leaf explicit-sid {
      //when "../mode = 'EXPLICIT'";
      type sid-type;

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      description "Explicitly configured EPE SID value, when the sid-allocation-type
                   is EXPLICIT";
    }

    leaf allocated-sid {
      type sid-type;
      config false;
      description "EPE SID value allocated by the node. When the sid allocation type
                   is DYNAMIC, this would be a SID allocated by the node. In the case
                   of EXPLICIT allocation type, this would typically be the explicit sid
                   value configured by the user";
    }
  }

  grouping epe-backup-info {
    description "Parameters for EPE backup SID selection";
    container backup {
      description "Backup policy for this EPE";
      leaf active {
        type boolean;
        config false;
        description
          "Boolean indicating if the backup as per requested policy is
           active for this EPE. Typically when EPE Peer, Link or Set is
           down, backup SID as per backup policy, would become active";
      }
      leaf backup-type {
        type enumeration {
          enum PeerNodeSid {
            description "Backup via another Peer Node SID to the
                         same AS. A Peer identifier is also
                         required when this backup-type is
                         selected";
          }
          enum PeerAdjSid {
            description "Backup via remaining Peer Adjacencies to the
                         same peer";
          }
          enum PeerSetSid {
            description "Backup via Remaining PeerNode SIDs in the
                         same PeerSet";
          }
          enum IGP {
            description "Pop the EPE SID and perform IP lookup";
          }
        }
        default "IGP";
        description "Type of the backup for this EPE";

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        reference "TBD";
      }

      leaf backup-peer {
        //when "../backup-type = 'PeerNodeSid'";
        type inet:ip-address;
        description "Peer identifier for the case when backup
                     type is PeerNodeSid";
      }

      leaf backup-sid {
        type sid-type;
        description
          "Backup SID (of a EPE Peer, Peer Adjacency or Peer-Set) to be
           used as backup for this EPE";
      }
    }
  }

  grouping epe-config {
    description "Egress Peer Engineering (EPE) config grouping";
    container egress-peer-engineering {
      description "Egress Peer Engineering (EPE) config under BGP Peer";

      uses epe-sid-alloc-mode;

      leaf peer-set-name {
        type string;
        description "Make this EPE peer a member of the named
                     Peer Set.";
      }

      uses epe-backup-info;

      list peer-adjacency {
        key first-hop-ipaddress;
        description "EPE parameters for the adjacency links
                     over which multi-hop peering is setup";

        leaf first-hop-ipaddress {
          type inet:ip-address;
          description "First hop IP address of the link";
        }

        leaf first-hop-interface {
          type string;
          config false;
          description "The interface corresponding to the link";

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        }

        uses epe-sid-alloc-mode;
        uses epe-backup-info;
      }
    }
  }

  grouping route-key-leafs {
    description "Grouping for key leafs identifying a route";
    leaf prefix {
      type union {
         type inet:ip-prefix;
         type string;
      }
      description "BGP Prefix. This is a temp definition to
                  cover ip-prefix and other NLRI formats.
                  Import the type once defined in base
                  BGP RIB model";
    }
    leaf neighbor {
      type inet:ip-address;
      description "BGP Neighbor";
    }
    leaf add-path-id {
      type uint32;
      description "Add-path ID";
    }
  }

  grouping common-bgp-route-grouping {
    description "BGP route list" ;
    container routes {
      config false;
      description "BGP Route in local RIB";
      list route {
        key "prefix neighbor add-path-id";
        description "BGP route list";
        uses route-key-leafs;
      }
    }
  }

  grouping common-bgp-vpn-route-grouping {
    description "BGP route list" ;
    container routes {
      config false;
      description "BGP VPN Route in local RIB";

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      list route {
        key "rd prefix neighbor add-path-id";
        description "Route List";

        leaf rd {
          type rt-types:route-distinguisher;
          description "Route Distinguisher";
        }
        uses route-key-leafs;
      }
    }
  }

  //
  // BGP Specific Paramters
  //
  // Augment AF with route list

  augment "/rt:routing/rt:control-plane-protocols/rt:control-plane-protocol/" +
          "bgp:bgp/bgp:global/bgp:afi-safis/bgp:afi-safi/bgp:ipv4-unicast" {
    description
      "Augment BGP SAFI route";
    uses common-bgp-route-grouping;
  }
  augment "/rt:routing/rt:control-plane-protocols/rt:control-plane-protocol/" +
          "bgp:bgp/bgp:global/bgp:afi-safis/bgp:afi-safi/bgp:ipv6-unicast" {
    description
      "Augment BGP SAFI route";
    uses common-bgp-route-grouping;
  }
  augment "/rt:routing/rt:control-plane-protocols/rt:control-plane-protocol/" +
          "bgp:bgp/bgp:global/bgp:afi-safis/bgp:afi-safi/bgp:ipv4-labeled-unicast" {
    description
      "Augment BGP SAFI route";
    uses common-bgp-route-grouping;

  }
  augment "/rt:routing/rt:control-plane-protocols/rt:control-plane-protocol/" +
          "bgp:bgp/bgp:global/bgp:afi-safis/bgp:afi-safi/bgp:ipv6-labeled-unicast" {
    description
      "Augment BGP SAFI route";
    uses common-bgp-route-grouping;
  }
  augment "/rt:routing/rt:control-plane-protocols/rt:control-plane-protocol/" +
          "bgp:bgp/bgp:global/bgp:afi-safis/bgp:afi-safi/bgp:l3vpn-ipv4-unicast" {
    description
      "Augment BGP SAFI route";
    uses common-bgp-vpn-route-grouping;

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  }
  augment "/rt:routing/rt:control-plane-protocols/rt:control-plane-protocol/" +
          "bgp:bgp/bgp:global/bgp:afi-safis/bgp:afi-safi/bgp:l3vpn-ipv6-unicast" {
    description
      "Augment BGP SAFI route";
    uses common-bgp-vpn-route-grouping;
  }

  // SR Prefix SID Related.
  // Prefix SID label index config via Route Policy
  augment "/rpol:routing-policy/" +
          "rpol:policy-definitions/rpol:policy-definition/" +
          "rpol:statements/rpol:statement/" +
          "rpol:actions/rpol:policy-result" {
    description
       "BGP policy actions to set label index";
    leaf set-label-index {
      type uint32;
      description "Label Index";
    }
  }

  // Prefix SID label in SAFI route
  augment "/rt:routing/rt:control-plane-protocols/rt:control-plane-protocol/" +
          "bgp:bgp/bgp:global/bgp:afi-safis/bgp:afi-safi/bgp:ipv4-labeled-unicast/" +
          "ietf-bgp-sr:routes/ietf-bgp-sr:route" {
    description
      "Augment BGP AF Table for SR prefix sid Labels info";
    uses sr-route-prefix-sid;
  }
  augment "/rt:routing/rt:control-plane-protocols/rt:control-plane-protocol/" +
          "bgp:bgp/bgp:global/bgp:afi-safis/bgp:afi-safi/bgp:ipv6-labeled-unicast/" +
          "ietf-bgp-sr:routes/ietf-bgp-sr:route" {
    description
      "Augment BGP AF Table for SR prefix sid Labels info";
    uses sr-route-prefix-sid;
  }

  // Egress Peer Engineering (EPE) related.
  // EPE config under neighbor
  augment "/rt:routing/rt:control-plane-protocols/rt:control-plane-protocol/" +
          "bgp:bgp/bgp:neighbors/bgp:neighbor" {
    description
      "Egress Peer Engineering data";
    uses epe-config;
  }
  augment "/rt:routing/rt:control-plane-protocols/rt:control-plane-protocol/" +
          "bgp:bgp/bgp:peer-groups/bgp:peer-group" {

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    description
      "Egress Peer Engineering data";
    uses epe-config;
  }
}

<CODE ENDS>

5.  Contributors

   Dhanendra Jain
   Cisco Systems
   US

   Email: dhanendra.ietf@gmail.com

   Zhichun Jiang
   Cisco Systems
   US

   Email: zcjiang@tencent.com

   Zafar Ali
   Cisco Systems
   US

   Email: zali@cisco.com

   Sharmila Palani
   Cisco Systems
   US

   Email: spalani@cisco.com

6.  IANA Considerations

7.  Security Considerations

   The transport protocol used for sending the BGP Segment Routing data
   MUST support authentication and SHOULD support encryption.  The data-
   model by itself does not create any security implications.

   This draft does not change any underlying security issues inherent in
   [I-D.ietf-idr-bgp-model].

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8.  Acknowledgements

   TBD.

9.  References

9.1.  Normative References

   [I-D.ietf-idr-bgp-model]
              Jethanandani, M., Patel, K., Hares, S., and J. Haas, "BGP
              YANG Model for Service Provider Networks", draft-ietf-idr-
              bgp-model-09 (work in progress), June 2020.

   [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.

   [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>.

   [RFC6020]  Bjorklund, M., Ed., "YANG - A Data Modeling Language for
              the Network Configuration Protocol (NETCONF)", RFC 6020,
              DOI 10.17487/RFC6020, October 2010,
              <https://www.rfc-editor.org/info/rfc6020>.

   [RFC6241]  Enns, R., Ed., Bjorklund, M., Ed., Schoenwaelder, J., Ed.,
              and A. Bierman, Ed., "Network Configuration Protocol
              (NETCONF)", RFC 6241, DOI 10.17487/RFC6241, June 2011,
              <https://www.rfc-editor.org/info/rfc6241>.

   [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
              2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
              May 2017, <https://www.rfc-editor.org/info/rfc8174>.

   [RFC8342]  Bjorklund, M., Schoenwaelder, J., Shafer, P., Watsen, K.,
              and R. Wilton, "Network Management Datastore Architecture
              (NMDA)", RFC 8342, DOI 10.17487/RFC8342, March 2018,
              <https://www.rfc-editor.org/info/rfc8342>.

9.2.  Informative References

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   [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-srv6-network-programming]
              Filsfils, C., Camarillo, P., Leddy, J., Voyer, D.,
              Matsushima, S., and Z. Li, "SRv6 Network Programming",
              draft-ietf-spring-srv6-network-programming-16 (work in
              progress), June 2020.

   [RFC7951]  Lhotka, L., "JSON Encoding of Data Modeled with YANG",
              RFC 7951, DOI 10.17487/RFC7951, August 2016,
              <https://www.rfc-editor.org/info/rfc7951>.

   [RFC8040]  Bierman, A., Bjorklund, M., and K. Watsen, "RESTCONF
              Protocol", RFC 8040, DOI 10.17487/RFC8040, January 2017,
              <https://www.rfc-editor.org/info/rfc8040>.

   [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>.

   [RFC8407]  Bierman, A., "Guidelines for Authors and Reviewers of
              Documents Containing YANG Data Models", BCP 216, RFC 8407,
              DOI 10.17487/RFC8407, October 2018,
              <https://www.rfc-editor.org/info/rfc8407>.

Authors' Addresses

   Krishna Deevi
   Cisco
   170 W. Tasman Drive
   San Jose, CA  95134
   USA

   Email: kdeevi@cisco.com

   Kamran Raza
   Cisco
   2000 Innovation Drive
   Kanata, ON  K2K-3E8
   CA

   Email: skraza@cisco.com

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   Kausik Majumdar
   Comscope

   Email: kausik.majumdar@commscope.com

   Bruno Decraene
   Orange
   France

   Email: bruno.decraene@orange.com

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