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Versions: 00 draft-raza-bess-srv6-services-yang

Spring Working Group                                             D. Jain
Internet-Draft                                                   K. Raza
Intended status: Standards Track                                   Cisco
Expires: December 28, 2018                                   B. Decraene
                                                                  Orange
                                                                Z. Jiang
                                                                 Tencent
                                                            Jun 26, 2018


           YANG data model for BGP Segment Routing Extensions
                 draft-dhjain-spring-bgp-sr-yang-00.txt

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

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

   This Internet-Draft will expire on December 28, 2018.

Copyright Notice

   Copyright (c) 2018 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
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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




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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
   material may not have granted the IETF Trust the right to allow
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   it for publication as an RFC or to translate it into languages other
   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
     2.4.  SR Policy . . . . . . . . . . . . . . . . . . . . . . . .   5
     2.5.  Automatic Steering  . . . . . . . . . . . . . . . . . . .   5
     2.6.  SRv6 SIDs . . . . . . . . . . . . . . . . . . . . . . . .   6
   3.  Yang Tree . . . . . . . . . . . . . . . . . . . . . . . . . .   6
     3.1.  SR Prefix Sid (SR MPLS) . . . . . . . . . . . . . . . . .   6
     3.2.  Egress Peer Engineering . . . . . . . . . . . . . . . . .   7
     3.3.  SR Policy . . . . . . . . . . . . . . . . . . . . . . . .   8
     3.4.  Automatic Steering  . . . . . . . . . . . . . . . . . . .  10
     3.5.  SRv6 SIDs . . . . . . . . . . . . . . . . . . . . . . . .  11
   4.  Yang Module . . . . . . . . . . . . . . . . . . . . . . . . .  12
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  30
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .  30
   7.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  30
   8.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  30
     8.1.  Normative References  . . . . . . . . . . . . . . . . . .  30
     8.2.  Informative References  . . . . . . . . . . . . . . . . .  32
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  33

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)



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   [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.

   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
   [I-D.ietf-spring-segment-routing], 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.filsfils-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].

   o  BGP signaled SR Policy as described in
      [I-D.ietf-idr-segment-routing-te-policy].

   o  Automatic Steering as described in
      [I-D.ietf-spring-segment-routing-policy] and
      [I-D.ietf-idr-segment-routing-te-policy].





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   o  SRv6 VPN extensions as described in [I-D.draft-dawra-idr-
      srv6-vpn].

   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 [I-D.ietf-netmod-rfc6087bis].  When protocol states are
   retrieved from the NMDA operational state datastore, the returned
   states cover all "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




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   [I-D.ietf-idr-bgp-model].  The configuration and the applied config
   state are applicable for neighbor-groups as well.

2.4.  SR Policy

   Architecture for SR Policies is described in
   [I-D.ietf-spring-segment-routing-policy].  BGP Signaled SR Policies
   are described in the [I-D.ietf-idr-segment-routing-te-policy].
   Following Yang extensions for SR Policy configuration and state data
   are applicable:

   o  Addition of identies extending the BGP-AFI-SAFI base identity.
      This is to add two new address families namely IPv4 SR-policy and
      IPv6 SR-policy, as described in
      [I-D.ietf-idr-segment-routing-te-policy].

   o  BGP Signaled SR Policy candidate paths.  These refer to the
      explicit candidate paths signaled via BGP as SAFI NLRIs, state of
      which is applicable in the context of BGP speaker process.  This
      is modeled by adding SR Policy address family specific container
      under generic BGP afi-safi list entry defined in the base BGP
      model [I-D.ietf-idr-bgp-model].

   o  On Demand SR Policy candidate paths.  These refer to the dynamic
      candidate paths as described in
      [I-D.ietf-spring-segment-routing-policy].  There are two parts to
      this in the context of BGP.  A set of authorized SR Policy colors
      for on demand policy triggers, and the actual instantiated
      candidate paths per BGP next-hop.  New containers and lists are
      added under BGP global mode to model this information.

   o  SR Policy state in the context of BGP speaker.  This represents
      the state SR Policies (regardless of method of instantiation per
      candidate path).  The SR Policy state is maintained in the context
      of BGP speaker process to realize the Automatic Steering of
      overlay routes.  Automatic Steering extensions are described in
      the next section.

   Note: The common parameters and datatypes for the SR Policy,
   currently defined in this model, should be imported from SR Policy
   Manager model, once available.

2.5.  Automatic Steering

   Automatic Steering (AS) refers to the ability to forward traffic over
   a SR Policy on the head-end, as described in
   [I-D.ietf-spring-segment-routing-policy].  When a BGP route is
   received with the color extended community and if the color value



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   matches the color of an authorized SR Policy installed on the head-
   end, the route is programmed to resolve over SR Policy in forwarding.
   Automatic Steering information associated with the BGP routes is
   modeled as state information per route.

   TBD: The configuration parameters for Automatic Steering are yet to
   be added as an augmentation to the BGP route policy model.  Such as,
   extensions for opaque color extended community in BGP policy model,
   and the Color Only (CO) flags controlling the Automatic Steering
   behavior as described in [I-D.ietf-idr-segment-routing-te-policy].

2.6.  SRv6 SIDs

   SRv6 extensions defined here are correspond to the VPN programming
   via SRv6 as described in [I-D.draft-dawra-idr-srv6-vpn].  SRv6 sid
   allocation mode is applicable in the context of ipv4 unicast and ipv6
   unicast SAFI under VPN context.  This is modeled by adding new
   containers under the respective AFI/SAFIs from the base BGP model
   [I-D.ietf-idr-bgp-model].

   The common data types for SRv6 are imported form [I-D.draft-raza-
   spring-srv6-yang].

   TBD: Base BGP model [I-D.ietf-idr-bgp-model], in its current form is
   not scoped within the context of a Network Instance.  Therefore, the
   context of a VRF is not fully realized.  The extensions done in this
   model should fall within the scope of a VRF, once the top BGP
   container is linked under Network Instance.

3.  Yang Tree

3.1.  SR Prefix Sid (SR MPLS)



















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module: ietf-bgp-sr
augment /rpol:routing-policy/rpol:policy-definitions/rpol:policy-definition/rpol:statements/rpol:statement/rpol:actions/bgp-pol:bgp-actions:
    +--rw set-label-index?   uint32

augment /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                inet:ip-prefix
          +--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 /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                inet:ip-prefix
          +--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

 ...


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 /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
   ...

3.3.  SR Policy

   On Demand Nexthop (ODN) policies triggered by BGP






















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     augment /bgp:bgp/bgp:global:
       +--rw segment-routing
          +--rw on-demand-policies
          |  +--ro authorized-colors
          |  |  +--ro colors* [color]
          |  |     +--ro color    uint32
          |  +--ro installed-policies
          |     +--ro sr-policy* [color end-point]
          |        +--ro color        uint32
          |        +--ro end-point    inet:ip-address
          +--ro policy-state
             +--ro sr-policy* [color end-point]
                +--ro color                uint32
                +--ro end-point            inet:ip-address
                +--ro policy-state?        enumeration
                +--ro binding-sid?         sid-type
                +--ro steering-disabled?   empty
                +--ro ref-count?           uint32

   BGP Signaled Explicit SR Policies under ipv4 and ipv6 SR-Policy SAFI































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     augment /bgp:bgp/bgp:global/bgp:afi-safis/bgp:afi-safi:
       +--rw ipv4-srpolicy
          +--ro explicit-policies
             +--ro sr-policy* [distinguisher color endpoint]
                +--ro distinguisher           uint32
                +--ro color                   uint32
                +--ro endpoint                inet:ip-address
                +--ro preference?             uint32
                +--ro explicit-binding-sid
                |  +--ro binding-sid?       sid-type
                |  +--ro strict?            boolean
                |  +--ro drop-on-invalid?   boolean
                +--ro usable?                 boolean
                +--ro registered?             boolean

     augment /bgp:bgp/bgp:global/bgp:afi-safis/bgp:afi-safi:
       +--rw ipv6-srpolicy
          +--ro explicit-policies
             +--ro sr-policy* [distinguisher color endpoint]
                +--ro distinguisher           uint32
                +--ro color                   uint32
                +--ro endpoint                inet:ip-address
                +--ro preference?             uint32
                +--ro explicit-binding-sid
                |  +--ro binding-sid?       sid-type
                |  +--ro strict?            boolean
                |  +--ro drop-on-invalid?   boolean
                +--ro usable?                 boolean
                +--ro registered?             boolean


3.4.  Automatic Steering

   Yang Tree for Automatic Steering with example of ipv4-unicast SAFI

















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module: ietf-bgp-sr
  augment /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
          +--ro automatic-steering
          |  +--ro color?         -> /bgp:bgp/global/bgp-sr:segment-routing/policy-state/sr-policy/color
          |  +--ro end-point?     -> /bgp:bgp/global/bgp-sr:segment-routing/policy-state/sr-policy/end-point
          |  +--ro co-flag?       enumeration
          |  +--ro binding-sid?   -> /bgp:bgp/global/bgp-sr:segment-routing/policy-state/sr-policy/binding-sid


 ...


3.5.  SRv6 SIDs

   SRv6 SID allocation mode in the context of select AFs


module: ietf-bgp-sr
  augment /bgp:bgp/bgp:global/bgp:afi-safis/bgp:afi-safi/bgp:ipv4-unicast:
    +--rw segment-routing
       +--rw srv6
          +--rw sid-alloc-mode?   enumeration
  augment /bgp:bgp/bgp:global/bgp:afi-safis/bgp:afi-safi/bgp:ipv6-unicast:
    +--rw segment-routing
       +--rw srv6
          +--rw sid-alloc-mode?   enumeration

   ...


   SRv6 Received and local SID tree















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 augment /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
          +--ro srv6
             +--ro received-sids* [received-sid]
             |  +--ro received-sid    srv6-types:srv6-sid
             +--ro local-sids* [local-sid]
                +--ro local-sid    srv6-types:srv6-sid
                +--ro locator?     string
  augment /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
          +--ro srv6
             +--ro received-sids* [received-sid]
             |  +--ro received-sid    srv6-types:srv6-sid
             +--ro local-sids* [local-sid]
                +--ro local-sid    srv6-types:srv6-sid
                +--ro locator?     string

...

4.  Yang Module


<CODE BEGINS> file "ietf-bgp-sr@2018-06-26.yang"

module ietf-bgp-sr {
  yang-version 1.1;
  namespace "urn:ietf:params:xml:ns:yang:ietf-bgp-sr";
  // replace with IANA namespace when assigned
  prefix bgp-sr ;

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

  import ietf-inet-types {
    prefix inet;
  }




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  import ietf-routing-policy {
    prefix rpol;
  }

  import ietf-bgp {
    prefix bgp;
  }

  import ietf-bgp-policy {
    prefix bgp-pol;
  }

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

  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

     BGP (bgp) : Border Gateway Protocol

     EPE : Egress Peer Engineering

     EVPN: Ethernet VPN

     SR : Segment Routing

     SID : Segment Identifier

     SRv6 : Segment Routing with IPv6 Data plane

     VPN : Virtual Private Network




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     VRF : Virtual Routing and Forwarding

    ";

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

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

  // SR Policy SAFI identities
  identity IPV4_SRPOLICY {
    base bgp-types:AFI_SAFI_TYPE;
    description
     "IPv4 SR Policy (AFI,SAFI = 1,73)";
    reference "TBD";
  }

  identity IPV6_SRPOLICY {
    base bgp-types:AFI_SAFI_TYPE;
    description
      "IPv6 SR Policy (AFI,SAFI = 2,73)";
    reference "TBD";
  }

  // 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 {



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    description "SR Prefix SID attribute associated with BGP Route";
    container prefix-sid {
      description "Prefix SID attribute";
      leaf label-index {
        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.";
    }



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



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        }
        default "IGP";
        description "Type of the backup for this EPE";
        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 {



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          type string;
          config false;
          description "The interface corresponding to the link";
        }

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

  //
  // SR Policy Related Groupings
  //
  //Color and Endpoint of the SR Policy
  grouping sr-policy-color-endpoint {
    description "Common grouping for SR Policy Color and
                 Endpoint";
    leaf color {
      type uint32;
      description "Color of the policy";
    }

    leaf end-point {
      type inet:ip-address;
      description "Endpoint of the policy";
    }
  }
  // Authorized colors for On Demand SR Policy programming
  grouping sr-odn-auth-colors {
    description
      "Authorized colors for On Demand (dynamic) SR Policies
       towards BGP nexthops";
    container authorized-colors {
      config false;
      description
        "Authorized colors for On Demand (dynamic) SR policies
         towards BGP nexthops";
      list colors {
        key "color";
        description "List of SR Policy Colors";
        leaf color {
          type uint32;
          description "Color value";
        }
      }
    }
  }



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  grouping sr-policy-cmn-state {
    description "Common state parameters applicable to
                 SR Policies";
    leaf policy-state {
      type enumeration {
        enum UP {
          description "SR Policy state UP";
        }
        enum DOWN {
          description "SR Policy state DOWN";
        }
      }
      description "SR Policy forwarding state";
    }

    leaf binding-sid {
      type sid-type;
      description "Binding SID of the SR Policy";
    }

    leaf steering-disabled {
      type empty;
      description "This attribute is set if steering
                   is disabled on this SR policy";
    }

    leaf ref-count {
      type uint32;
      description "Count of routes steering over this policy";
    }
  }


  //
  // SR Policy State grouping
  //
  grouping sr-policy-state {
    description "SR Policy State";
    container policy-state {
      config false;
      description "SR Policy State";
      list sr-policy {
        key "color end-point";
        description "List of SR Policies";

        uses sr-policy-color-endpoint;

        // State of the SR Policy in BGP



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        uses sr-policy-cmn-state;
      }
    }
  }

  grouping sr-exp-policy-cp-state {
    description "State of BGP signaled SR Policy (explicit)
                 candidate paths";
    container explicit-policies {
      config false;
      description "BGP signaled explicit SR Policies";
      list sr-policy {
        key "distinguisher color end-point";
        description "List of BGP signaled explicit SR Policies";
        leaf distinguisher {
          type uint32;
          description "Distinguisher of the SR Policy
                       candidate path";
        }

        uses sr-policy-color-endpoint;

        leaf preference {
          type uint32;
          description "Preference of the SR Policy candidate path";
        }

        container explicit-binding-sid {
          description "Explicitly supplied Binding SID
                       for this policy";
          leaf binding-sid {
            type sid-type;
            description "Binding SID value";
          }
          leaf strict {
            type boolean;
            description "Boolean indicating that the node
                         must use only the supplied Binding SID
                         for this SR Policy.
                         reference: TBD";
          }
          leaf drop-on-invalid {
            type boolean;
            description "Boolean to indicate drop upon invalid
                         policy, behavior. This overwrites the
                         default behavior of fallback to IGP path
                         , when SR Policy is (or becomes) invalid.
                         reference: TBD";



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          }
        }

        leaf usable {
          type boolean;
          description "Boolean to indicate that the SR Policy is
                       usable on this node.
                       reference: TBD";
        }

        leaf registered {
          type boolean;
          description "Boolean to indicate that the SR policy
                       is registered with policy manager to
                       install the corresponding forwarding entry";

        }

        // TODO: Segment Lists and other parameters from SR Policy model
        //       to be imported here.
      }
    }
  }

  grouping sr-odn-policies {
    description "SR On Demand (dynamic) SR Policies";
    container installed-policies {
      config false;
      description "BGP triggered On Demand (dynamic) SR Policies
                   corresponding to the BGP nexthops";
      list sr-policy {
        key "color end-point";
        description "SR Policy list";
        uses sr-policy-color-endpoint;
      }
    }
  }

  grouping sr-policy-steering-state {
    description "Per route Automatic Steering parameters";
    container automatic-steering {
      description "Per route Automatic Steering parameters";
      leaf color {
        type leafref {
          path "/bgp:bgp/bgp:global/bgp-sr:segment-routing/" +
               "bgp-sr:policy-state/bgp-sr:sr-policy/" +
               "bgp-sr:color";
        }



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        description "Color of the SR Policy being used for
                     Automatic Steering";
      }
      leaf end-point {
        type leafref {
          path "/bgp:bgp/bgp:global/bgp-sr:segment-routing/" +
               "bgp-sr:policy-state/bgp-sr:sr-policy/" +
               "bgp-sr:end-point";
        }
        description "End-point of the SR Policy being used
                     for Automatic Steering";
      }
      leaf co-flag {
        type enumeration {
          enum 00 {
            description "Color-Only flag 00";
          }
          enum 01 {
            description "Color-Only flag 01";
          }
          enum 10 {
            description "Color-Only flag 10";
          }
        }
        default "00";
        description "Color-Only (CO) flags applicable for
                     Automatic Steering of this route";
      }
      leaf binding-sid {
        type leafref {
          path "/bgp:bgp/bgp:global/bgp-sr:segment-routing/" +
               "bgp-sr:policy-state/bgp-sr:sr-policy/" +
               "bgp-sr:binding-sid";
        }
        description "Binding SID of the SR Policy";
      }
    }
  }

  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.



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                  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";
      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;
      }
    }
  }

  //
  //  SRv6 extensions related Groupings
  //




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  // SRv6 VPN Sid allocation mode
  grouping srv6-sid-mode {
    description "SRv6 VPN SID allocation mode";
    leaf sid-alloc-mode {
      type enumeration {
        enum per-ce {
          description "Allocate SRv6 SID per CE";
        }
        enum per-route {
          description "Allocate SRv6 SID per prefix";
        }
        enum per-vpn {
          description "Allocate SRv6 SID per VPN";
        }
      }
      description "BGP SRv6 SID allocation model";
    }
  }

  grouping srv6-attr-sid-info {
    description "SRv6 SID info per route";
    container srv6 {
      description "Per Route SRv6 parameters";
      list received-sids {
        key "received-sid";
        description "List of received SRv6 SIDs";
        leaf received-sid {
          type srv6-types:srv6-sid;
          description "Received SID";
        }
      }
      list local-sids {
        key "local-sid";
        description "List of local SRv6 SIDs";
        leaf local-sid {
          type srv6-types:srv6-sid;
          description "Local SID";
        }
        leaf locator {
          type string;
          description "SRv6 Locator";
        }
      }
    }
  }

  //
  // BGP Specific Paramters



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  //
  // Augment AF with route list
  augment "/bgp:bgp/bgp:global/bgp:afi-safis/" +
          "bgp:afi-safi/bgp:ipv4-unicast" {
    description
      "Augment BGP SAFI route";
    uses common-bgp-route-grouping;
  }
  augment "/bgp:bgp/bgp:global/bgp:afi-safis/" +
          "bgp:afi-safi/bgp:ipv6-unicast" {
    description
      "Augment BGP SAFI route";
    uses common-bgp-route-grouping;
  }
  augment "/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 "/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 "/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;
  }
  augment "/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;
  }
  augment "/bgp:bgp/bgp:global/bgp:afi-safis/" +
          "bgp:afi-safi/bgp:l2vpn-evpn" {
    description
      "Augment BGP SAFI route";
    uses common-bgp-vpn-route-grouping;
  }

  // SR Prefix SID Related.
  // Prefix SID label index config via Route Policy



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  augment "/rpol:routing-policy/" +
          "rpol:policy-definitions/rpol:policy-definition/" +
          "rpol:statements/rpol:statement/" +
          "rpol:actions/bgp-pol:bgp-actions" {
    description
       "BGP policy actions to set label index";
    leaf set-label-index {
      type uint32;
      description "Label Index";
    }
  }

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

  // TBD: SR Mapping server related parameters.

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

  // SR Policy Related
  // On Demand authorized colors table
  // SR Policy state data
  augment "/bgp:bgp/bgp:global" {
    description
      "Segment Routing parameters in BGP global model";
    container segment-routing {



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      description "Segment Routing parameters";
      container on-demand-policies {
        description
          "Segment Routing On Demand Nexthop
           (ODN) SR Policies";
        uses sr-odn-auth-colors;
        uses sr-odn-policies;
      }
      uses sr-policy-state;
    }
  }

  // Steering state in overlay BGP routes
  augment "/bgp:bgp/bgp:global/bgp:afi-safis/" +
          "bgp:afi-safi/bgp:ipv4-unicast/bgp-sr:routes/bgp-sr:route" {
    description
      "Augment BGP SAFI route with steering info";
    uses sr-policy-steering-state;
  }
  augment "/bgp:bgp/bgp:global/bgp:afi-safis/" +
          "bgp:afi-safi/bgp:ipv6-unicast/bgp-sr:routes/bgp-sr:route" {
    description
      "Augment BGP SAFI route with steering info";
    uses sr-policy-steering-state;
  }
  augment "/bgp:bgp/bgp:global/bgp:afi-safis/" +
          "bgp:afi-safi/bgp:ipv4-labeled-unicast/bgp-sr:routes/bgp-sr:route" {
    description
      "Augment BGP SAFI route with steering info";
    uses sr-policy-steering-state;
  }
  augment "/bgp:bgp/bgp:global/bgp:afi-safis/" +
          "bgp:afi-safi/bgp:ipv6-labeled-unicast/bgp-sr:routes/bgp-sr:route" {
    description
      "Augment BGP SAFI route with steering info";
    uses sr-policy-steering-state;
  }
  augment "/bgp:bgp/bgp:global/bgp:afi-safis/" +
          "bgp:afi-safi/bgp:l3vpn-ipv4-unicast/bgp-sr:routes/bgp-sr:route" {
    description
      "Augment BGP SAFI route with steering info";
    uses sr-policy-steering-state;
  }
  augment "/bgp:bgp/bgp:global/bgp:afi-safis/" +
          "bgp:afi-safi/bgp:l3vpn-ipv6-unicast/bgp-sr:routes/bgp-sr:route" {
    description
      "Augment BGP SAFI route with steering info";
    uses sr-policy-steering-state;



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  }
  augment "/bgp:bgp/bgp:global/bgp:afi-safis/" +
          "bgp:afi-safi/bgp:l2vpn-evpn/bgp-sr:routes/bgp-sr:route" {
    description
      "Augment BGP SAFI route with steering info";
    uses sr-policy-steering-state;
  }

  // BGP Signaled SR Policy explicit candidate paths state
  augment "/bgp:bgp/bgp:global/bgp:afi-safis/bgp:afi-safi" {
    description "Augment IPv4 SR Policy SAFI list entry";
    container ipv4-srpolicy {
      when "../afi-safi-name = 'bgp-types:IPV4_SRPOLICY'" {
       description
         "Include this container for IPv4 SR Policy specific
          configuration";
      }
      description "IPv4 SR Policy specific parameters";
      uses sr-exp-policy-cp-state;
    }
  }

  augment "/bgp:bgp/bgp:global/bgp:afi-safis/bgp:afi-safi" {
    description "Augment IPv6 SR Policy SAFI list entry";
    container ipv6-srpolicy {
      when "../afi-safi-name = 'bgp-types:IPV6_SRPOLICY'" {
        description
          "Include this container for IPv6 SR Policy specific
           configuration";
      }
      description "IPv6 SR Policy specific parameters";
      uses sr-exp-policy-cp-state;
    }
  }

  // SRv6 VPN SID allocation mode configuration.
  augment "/bgp:bgp/bgp:global/bgp:afi-safis/" +
          "bgp:afi-safi/bgp:ipv4-unicast" {
    description
      "Augment BGP global IPv4 unicast AF mode
       to add SR specific parameters";
    container segment-routing {
      description "Segment Routing specific parameters";
      container srv6 {
        description "SRv6 specific parameters";
        uses srv6-sid-mode;
      }
    }



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  }

  augment "/bgp:bgp/bgp:global/bgp:afi-safis/" +
          "bgp:afi-safi/bgp:ipv6-unicast" {
    description
      "Augment BGP global IPv6 unicast AF mode
       to add SR specific parameters";
    container segment-routing {
      description "Segment Routing specific parameters";
      container srv6 {
        description "SRv6 specific parameters";
        uses srv6-sid-mode;
      }
    }
  }

  // SRv6 local and remote sids per route.
  augment "/bgp:bgp/bgp:global/bgp:afi-safis/" +
          "bgp:afi-safi/bgp:ipv4-unicast/bgp-sr:routes/bgp-sr:route" {
    description
      "Augment AF route with SRv6 SID info";
    uses srv6-attr-sid-info;
  }
  augment "/bgp:bgp/bgp:global/bgp:afi-safis/" +
          "bgp:afi-safi/bgp:ipv6-unicast/bgp-sr:routes/bgp-sr:route" {
    description
      "Augment AF route with SRv6 SID info";
    uses srv6-attr-sid-info;
  }

  augment "/bgp:bgp/bgp:global/bgp:afi-safis/" +
          "bgp:afi-safi/bgp:l3vpn-ipv4-unicast/routes/route" {
    description
      "Augment AF route with SRv6 SID info";
    uses srv6-attr-sid-info;
  }

  augment "/bgp:bgp/bgp:global/bgp:afi-safis/" +
          "bgp:afi-safi/bgp:l3vpn-ipv6-unicast/bgp-sr:routes/bgp-sr:route" {
    description
      "Augment AF route with SRv6 SID info";
    uses srv6-attr-sid-info;
  }

  augment "/bgp:bgp/bgp:global/bgp:afi-safis/" +
          "bgp:afi-safi/bgp:l2vpn-evpn/bgp-sr:routes/bgp-sr:route" {
    description
      "Augment AF route with SRv6 SID info";



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    uses srv6-attr-sid-info;
  }
}

<CODE ENDS>


5.  IANA Considerations

6.  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].

7.  Acknowledgements

   The authors would like to thank TBD for their detail reviews and
   comments.

8.  References

8.1.  Normative References

   [I-D.dawra-idr-srv6-vpn]
              Dawra, G., Filsfils, C., Dukes, D., Brissette, P.,
              Camarillo, P., Leddy, J., daniel.voyer@bell.ca, d.,
              daniel.bernier@bell.ca, d., Steinberg, D., Raszuk, R.,
              Decraene, B., and S. Matsushima, "BGP Signaling of IPv6-
              Segment-Routing-based VPN Networks", draft-dawra-idr-
              srv6-vpn-03 (work in progress), December 2017.

   [I-D.filsfils-spring-srv6-network-programming]
              Filsfils, C., Li, Z., Leddy, J., daniel.voyer@bell.ca, d.,
              daniel.bernier@bell.ca, d., Steinberg, D., Raszuk, R.,
              Matsushima, S., Lebrun, D., Decraene, B., Peirens, B.,
              Salsano, S., Naik, G., Elmalky, H., Jonnalagadda, P., and
              M. Sharif, "SRv6 Network Programming", draft-filsfils-
              spring-srv6-network-programming-04 (work in progress),
              March 2018.








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   [I-D.ietf-6man-segment-routing-header]
              Previdi, S., Filsfils, C., Leddy, J., Matsushima, S., and
              d. daniel.voyer@bell.ca, "IPv6 Segment Routing Header
              (SRH)", draft-ietf-6man-segment-routing-header-13 (work in
              progress), May 2018.

   [I-D.ietf-idr-bgp-model]
              Shaikh, A., Shakir, R., Patel, K., Hares, S., D'Souza, K.,
              Bansal, D., Clemm, A., Zhdankin, A., Jethanandani, M., and
              X. Liu, "BGP Model for Service Provider Networks", draft-
              ietf-idr-bgp-model-02 (work in progress), July 2016.

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

   [I-D.ietf-idr-segment-routing-te-policy]
              Previdi, S., Filsfils, C., Jain, D., Mattes, P., Rosen,
              E., and S. Lin, "Advertising Segment Routing Policies in
              BGP", draft-ietf-idr-segment-routing-te-policy-03 (work in
              progress), May 2018.

   [I-D.ietf-netmod-rfc6087bis]
              Bierman, A., "Guidelines for Authors and Reviewers of YANG
              Data Model Documents", draft-ietf-netmod-rfc6087bis-20
              (work in progress), March 2018.

   [I-D.ietf-rtgwg-ni-model]
              Berger, L., Hopps, C., Lindem, A., Bogdanovic, D., and X.
              Liu, "YANG Network Instances", draft-ietf-rtgwg-ni-
              model-04 (work in progress), September 2017.

   [I-D.ietf-rtgwg-routing-types]
              Liu, X., Qu, Y., Lindem, A., Hopps, C., and L. Berger,
              "Routing Area Common YANG Data Types", draft-ietf-rtgwg-
              routing-types-17 (work in progress), October 2017.

   [I-D.ietf-spring-segment-routing]
              Filsfils, C., Previdi, S., Ginsberg, L., Decraene, B.,
              Litkowski, S., and R. Shakir, "Segment Routing
              Architecture", draft-ietf-spring-segment-routing-15 (work
              in progress), January 2018.







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   [I-D.ietf-spring-segment-routing-policy]
              Filsfils, C., Sivabalan, S., daniel.voyer@bell.ca, d.,
              bogdanov@google.com, b., and P. Mattes, "Segment Routing
              Policy Architecture", draft-ietf-spring-segment-routing-
              policy-01 (work in progress), June 2018.

   [I-D.raza-spring-srv6-yang]
              Raza, K., Rajamanickam, J., Liu, X., Hu, Z., Hussain, I.,
              Shah, H., daniel.voyer@bell.ca, d., Elmalky, H.,
              Matsushima, S., Horiba, K., and A. Abdelsalam, "YANG Data
              Model for SRv6 Base and Static", draft-raza-spring-
              srv6-yang-01 (work in progress), March 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>.

8.2.  Informative References

   [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>.





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Authors' Addresses

   Dhanendra Jain
   Cisco
   170 W. Tasman Drive
   San Jose, CA  95134
   USA

   Email: dhjain@cisco.com


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

   Email: skraza@cisco.com


   Bruno Decraene
   Orange
   France

   Email: bruno.decraene@orange.com


   Zhichun Jiang
   Tencent

   Email: zcjiang@tencent.com




















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