Interdomain Routing                                      M. Jethanandani
Internet-Draft                                                    VMware
Intended status: Standards Track                                K. Patel
Expires: December 15, 2019 April 6, 2020                                            Arrcus
                                                                S. Hares
                                                                  Huawei
                                                           June 13,
                                                                 J. Haas
                                                        Juniper Networks
                                                         October 4, 2019

              BGP YANG Model for Service Provider Networks
                      draft-ietf-idr-bgp-model-06
                      draft-ietf-idr-bgp-model-07

Abstract

   This document defines a YANG data model for configuring and managing
   BGP, including protocol, policy, and operational aspects, such as
   RIB, based on data center, carrier and content provider operational
   requirements.

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   provisions of BCP 78 and BCP 79.

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   This Internet-Draft will expire on December 15, 2019. April 6, 2020.

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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2   3
     1.1.  Goals and approach  . . . . . . . . . . . . . . . . . . .   3
     1.2.  Note to RFC Editor  . . . . . . . . . . . . . . . . . . .   4
     1.3.  Terminology . . . . . . . . . . . . . . . . . . . . . . .   4   5
     1.4.  Abbreviations . . . . . . . . . . . . . . . . . . . . . .   5
   2.  Model overview  . . . . . . . . . . . . . . . . . . . . . . .   5
     2.1.  BGP protocol configuration  . . . . . . . . . . . . . . .   6
     2.2.  Policy configuration overview . . . . . . . . . . . . . .   8   9
     2.3.  BGP RIB overview  . . . . . . . . . . . . . . . . . . . .   9  10
       2.3.1.  Local Routing . . . . . . . . . . . . . . . . . . . .  11  12
       2.3.2.  Pre updates per-neighbor  . . . . . . . . . . . . . .  11  12
       2.3.3.  Post updates per-neighbor . . . . . . . . . . . . . .  11  12
       2.3.4.  Pre route advertisements per-neighbor . . . . . . . .  11  12
       2.3.5.  Post route advertisements per-neighbor  . . . . . . .  11  12
   3.  Relation to other YANG data models  . . . . . . . . . . . . .  11  12
   4.  Security Considerations . . . . . . . . . . . . . . . . . . .  11  13
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  12  13
     5.1.  URI Registration  . . . . . . . . . . . . . . . . . . . .  12  14
     5.2.  YANG Module Name Registration . . . . . . . . . . . . . .  12  14
   6.  YANG modules  . . . . . . . . . . . . . . . . . . . . . . . .  13  14
   7.  Structure of the YANG modules . . . . . . . . . . . . . . . .  14  15
     7.1.  Main module and submodules for base items . . . . . . . .  14  15
     7.2.  BGP types . . . . . . . . . . . . . . . . . . . . . . . .  58  64
     7.3.  BGP policy data . . . . . . . . . . . . . . . . . . . . .  69  75
     7.4.  RIB modules . . . . . . . . . . . . . . . . . . . . . . .  80  86
   8.  Examples  . . . . . . . . . . . . . . . . . . . . . . . . . . 113 120
     8.1.  Creating BGP Instance . . . . . . . . . . . . . . . . . . 113 120
     8.2.  Neighbor Address Family Configuration . . . . . . . . . . 114 121
     8.3.  IPv6 Neighbor Configuration . . . . . . . . . . . . . . . 123
     8.4.  VRF Configuration . . . . . . . . . . . . . . . . . . . . 124
   9.  Contributors  . . . . . . . . . . . . . . . . . . . . . . . . 116 125
   10. Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . 116 126
   11. References  . . . . . . . . . . . . . . . . . . . . . . . . . 116 126
     11.1.  Normative references . . . . . . . . . . . . . . . . . . 116 126
     11.2.  Informative references . . . . . . . . . . . . . . . . . 118 128
   Appendix A.  How to add a new AFI and Augment a Module  . . . . . 129
   Appendix B.  How to deviate a module  . . . . . . . . . . . . . . 131
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . . 119 132

1.  Introduction

   This document describes a YANG [RFC7950] data model for the BGP-4
   [RFC4271] protocol, including various protocol extensions, policy
   configuration, as well as defining key operational state data,
   including Routing Information Base (RIB).  The model is intended to
   be vendor-neutral, in order to allow operators to manage BGP
   configuration in heterogeneous environments with routers supplied by
   multiple vendors.  The model is also intended to be readily mapped to
   existing implementations to facilitate support from as large a set of
   routing hardware and software vendors as possible.  This module does
   not support previous versions of BGP, and cannot support establishing
   and maintaining state information of neighbors with previous versions
   of BGP.

1.1.  Goals and approach

   The model covers the base BGP features that are deployed across major
   implementations and the common BGP configurations in use across a
   number of operator network deployments.  In particular, this model
   attempts to cover BGP features defined in BGP [RFC4271], BGP
   Communities Attribute [RFC1997], BGP Route Reflection [RFC4456],
   Multiprotocol Extensions for BGP-4 [RFC4760], Autonomous System
   Confederations for BGP [RFC5065], BGP Route Flap Damping [RFC2439],
   Graceful Restart Mechanism for BGP [RFC4724], and BGP Prefix Origin
   Validation [RFC6811].

   Along with configuration of base BGP features, this model also
   addresses policy configuration, by providing "hooks" for applying
   policies, and also defining BGP-specific policy features.  The BGP
   policy features are intended to be used with the general routing
   policy model defined in A YANG Data Model for Routing Policy
   Management [I-D.ietf-rtgwg-policy-model].  The model conforms to the
   NMDA [RFC8342] architecture and has support for configuring
   Bidirectional Forward Detection (BFD) [RFC5880] for fast next hop
   liveliness check.

   For the base BGP features, the focus of the model described in this
   document is on providing configuration and operational state
   information relating to:

   o  The global BGP instance, and neighbors whose configuration is
      specified individually, or templated with the use of peer-groups.

   o  The address families that are supported by peers, and the global
      configuration which relates to them.

   o  The policy configuration "hooks" and BGP-specific policy features
      that relate to a neighbor - controlling the import and export of
      NLRIs.

   o  RIB contents.

   As mentioned earlier, any configuration items that are deemed to be
   widely available in existing major BGP implementations are included
   in the model.  Additional, more esoteric, configuration items that
   are not commonly used, or only available from a single
   implementation, are omitted from the model with an expectation that
   they will be available in companion modules that augment or extend
   the current model.  This allows clarity in identifying data that is
   part of the vendor-neutral base model.

   Where possible, naming in the model follows conventions used in
   available standards documents, and otherwise tries to be self-
   explanatory with sufficient descriptions of the intended behavior.
   Similarly, configuration data value constraints and default values,
   where used, are based on recommendations in current standards
   documentation, or those commonly used in multiple implementations.
   Since implementations can vary widely in this respect, this version
   of the model specifies only a limited set of defaults and ranges with
   the expectation of being more prescriptive in future versions based
   on actual operator use.

1.2.  Note to RFC Editor

   This document uses several placeholder values throughout the
   document.  Please replace them as follows and remove this note before
   publication.

   RFC XXXX, where XXXX is the number assigned to this document at the
   time of publication.

   2019-06-13

   2019-10-03 with the actual date of the publication of this document.

   RFC ZZZZ, where ZZZZ is the number assigned to A YANG Data Model for
   Routing Policy Management [I-D.ietf-rtgwg-policy-model].

   RFC AAAA, where AAAA is the number assigned to BGP Monitoring
   Protocol [RFC7854].

   RFC BBBB, where BBBB is the number assigned to YANG Data Model for
   Bidirectional Forward Detection [I-D.ietf-bfd-yang].

1.3.  Terminology

   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.

1.4.  Abbreviations

       +--------------+-------------------------------------------+
       | Abbreviation |                                           |
       +--------------+-------------------------------------------+
       | AFI          | Address Family Identifier                 |
       |              |                                           |
       | BFD          | Bidirectional Forward Detection           |
       |              |                                           |
       | NLRI         | Network Layer Reachability Information    |
       |              |                                           |
       | NMDA         | Network Management Datastore Architecture |
       |              |                                           |
       | RIB          | Routing Information Base                  |
       |              |                                           |
       | SAFI         | Subsequent Address Family Identifier      |
       |              |                                           |
       | VRF          | Virtual Routing and Forwarding            |
       +--------------+-------------------------------------------+

2.  Model overview

   The BGP model is defined across several YANG modules and submodules,
   but at a high level is organized into six elements:

   o  base protocol configuration -- configuration affecting BGP
      protocol-related operations, defined at various levels of
      hierarchy.

   o  multiprotocol configuration -- configuration affecting individual
      address-families within BGP Multiprotocol Extensions for BGP-4
      [RFC4760].

   o  neighbor configuration -- configuration affecting an individual
      neighbor within BGP.

   o  neighbor multiprotocol configuration -- configuration affecting
      individual address-families for a neighbor within BGP.

   o  policy configuration -- hooks for application of the policies
      defined in A YANG Data Model for Routing Policy Management
      [I-D.ietf-rtgwg-policy-model] that act on routes sent (received)
      to (from) peers or other routing protocols and BGP-specific policy
      features.

   o  operational state -- variables used for monitoring and management
      of BGP operations.

   These modules also make use of standard Internet types, such as IP
   addresses and prefixes, autonomous system numbers, etc., defined in
   Common YANG Data Types [RFC6991].

2.1.  BGP protocol configuration

   The BGP protocol configuration model is organized hierarchically,
   much like the majority of router implementations.  That is,
   configuration items can be specified at multiple levels, as shown
   below.

 module: ietf-bgp

   augment /rt:routing/rt:control-plane-protocols/rt:control-plane-proto
 col:
     +--rw bgp
        +--rw global!
        |  +--rw as                         inet:as-number
        |  +--rw identifier?                yang:dotted-quad
        |  +--rw default-route-distance distance
        |  +--rw confederation
        |  +--rw graceful-restart {graceful-restart}?
        |  +--rw use-multiple-paths
        |  +--rw route-selection-options
        |  +--rw afi-safis
        |  +--rw apply-policy
        |  +--ro total-paths?               uint32
        |  +--ro total-prefixes?            uint32
        +--rw neighbors
        |  +--rw neighbor* [remote-address]
        |  +---n established
        |  +---n backward-transition
        |  +--rw clear-neighbors {clear-neighbors}?
        +--rw peer-groups
        |  +--rw peer-group* [peer-group-name]
        +--rw interfaces
        |  +--rw interface* [name]
        +--ro rib
           +--ro attr-sets
           +--ro communities
           +--ro ext-communities
           +--ro afi-safis

   Users may specify configuration at a higher level and have it apply
   to all lower-level items, or provide overriding configuration at a
   lower level of the hierarchy.  Overriding configuration items are
   optional, with neighbor specific configuration being the most
   specific or lowest level, followed by peer-group, and finally global.
   Global configuration options reflect a subset of the peer-group or
   neighbor specific configuration options which are relevant to the
   entire BGP instance.

   The model makes the simplifying assumption that most of the
   configuration items are available at all levels of the hierarchy.
   That is, very little configuration is specific to a particular level
   in the hierarchy, other than obvious items such as "group-name" only
   being available for the peer group-level config.  A notable exception
   is for sub-address family configuration where some items are only
   applicable for a given AFI-SAFI combination.

   In order to allow common configuration to be applied to a set of
   neighbors, all neighbor configuration options are available within a
   peer-group.  A neighbor is associated to a particular peer-group
   through the use of a peer-group leaf (which provides a reference to a
   configured item in the peer-group list).

   Address-family configuration is made available in multiple points
   within the model - primarily within the global container, where
   instance-wide configuration can be set (for example, global protocol
   parameters, the BGP best path route selection options, or global
   policies relating to the address-family); and on a per-neighbor or
   per-peer-group basis, where address-families can be enabled or
   disabled, and policy associated with the parent entity applied.
   Within the afi-safi container, generic configuration that applies to
   all address-families (e.g., whether the AFI-SAFI is enabled) is
   presented at the top-level, with address-family specific containers
   made available for options relating to only that AFI-SAFI.  Within
   the current revision of the model a generic set of address-families,
   and common configuration and state options are included - further
   work is expected to add additional parameters to this area of the
   model.

   The following address-families are currently supported by the model:

           +--rw bgp
             +--rw global!
                +--rw afi-safis
                   +--rw afi-safi* [afi-safi-name]
                      +--rw afi-safi-name              identityref
                      |
                      +--rw ipv4-unicast
                      |     ...
                      +--rw ipv6-unicast
                      |     ...
                      +--rw ipv4-labeled-unicast
                      |     ...
                      +--rw ipv6-labeled-unicast
                      |     ...
                      +--rw l3vpn-ipv4-unicast
                      |     ...
                      +--rw l3vpn-ipv6-unicast
                      |     ...
                      +--rw l3vpn-ipv4-multicast
                      |     ...
                      +--rw l3vpn-ipv6-multicast
                      |     ...
                      +--rw l2vpn-vpls
                      |     ...
                      +--rw l2vpn-evpn
                      |     ...

2.2.  Policy configuration overview

   The BGP policy configuration model augments the generic YANG routing
   policy model described in A YANG Data Model for Routing Policy
   Management [I-D.ietf-rtgwg-policy-model], which represents a
   condition-action policy framework for routing.  This model adds BGP-
   specific conditions (e.g., matching on the community attribute), and
   actions (e.g., setting local preference) to the generic policy
   framework.

   Policies that are defined in the routing-policy model are referenced
   in multiple places within the model:

   o  within the global instance, where a policy applies to all address-
      families for all peers.

   o  on a global AFI-SAFI basis, where policies apply to all peers for
      a particular address-family.

   o  on a per-peer-group or per-neighbor basis - where the policy
      applies to all address-families for the particular group or
      neighbor.

   o  on a per-afi-safi basis within a neighbor or peer-group context,
      where the policy is specific to the AFI-SAFI for a a specific
      neighbor or group.

   module: ietf-bgp-policy
     augment /rpol:routing-policy/rpol:defined-sets:
       +--rw bgp-defined-sets
             ...
     augment /rpol:routing-policy/rpol:policy-definitions
               /rpol:policy-definition/rpol:statements/rpol:statement
               /rpol:conditions:
       +--rw bgp-conditions
             ...
     augment /rpol:routing-policy/rpol:policy-definitions
               /rpol:policy-definition/rpol:statements/rpol:statement
               /rpol:actions:
       +--rw bgp-actions
             ...

2.3.  BGP RIB overview

   The RIB data model represents the BGP RIB contents.  The model
   supports five logical RIBs per address family.

   A abridged version of the tree shows the RIB portion of the tree
   diagram.

   module: ietf-bgp
     augment /rt:routing/rt:control-plane-protocols
               /rt:control-plane-protocol:
       +--rw bgp
          +--ro rib
             +--ro afi-safis
                +--ro afi-safi* [afi-safi-name]
                   +--ro afi-safi-name    identityref
                   +--ro ipv4-unicast
                   |  +--ro loc-rib
                   |  |  +--ro routes
                   |  |     +--ro route* [prefix origin path-id]
                   |  |     |     ...
                   |  |     +--ro clear-routes {clear-routes}?
                   |  |           ...
                   |  +--ro neighbors
                   |     +--ro neighbor* [neighbor-address]
                   |        +--ro neighbor-address    inet:ip-address
                   |        +--ro adj-rib-in-pre
                   |        |     ...
                   |        +--ro adj-rib-in-post
                   |        |     ...
                   |        +--ro adj-rib-out-pre
                   |        |     ...
                   |        +--ro adj-rib-out-post
                   |              ...
                   +--ro ipv6-unicast
                      +--ro loc-rib
                      |  +--ro routes
                      |     +--ro route* [prefix origin path-id]
                      |     |     ...
                      |     +--ro clear-routes {clear-routes}?
                      |           ...
                      +--ro neighbors
                         +--ro neighbor* [neighbor-address]
                            +--ro neighbor-address    inet:ip-address
                            +--ro adj-rib-in-pre
                            |     ...
                            +--ro adj-rib-in-post
                            |     ...
                            +--ro adj-rib-out-pre
                            |     ...
                            +--ro adj-rib-out-post
                                  ...

2.3.1.  Local Routing

   The loc-rib is the main BGP routing table for the local routing
   instance, containing best-path selections for each prefix.  The loc-
   rib table may contain multiple routes for a given prefix, with an
   attribute to indicate which was selected as the best path.  Note that
   multiple paths may be used or advertised even if only one path is
   marked as best, e.g., when using BGP add-paths.  An implementation
   may choose to mark multiple paths in the RIB as best path by setting
   the flag to true for multiple entries.

2.3.2.  Pre updates per-neighbor

   The adj-rib-in-pre table is a per-neighbor table containing the NLRI
   updates received from the neighbor before any local input policy
   rules or filters have been applied.  This can be considered the 'raw'
   updates from a given neighbor.

2.3.3.  Post updates per-neighbor

   The adj-rib-in-post table is a per-neighbor table containing the
   routes received from the neighbor that are eligible for best-path
   selection after local input policy rules have been applied.

2.3.4.  Pre route advertisements per-neighbor

   The adj-rib-out-pre table is a per-neighbor table containing routes
   eligible for sending (advertising) to the neighbor before output
   policy rules have been applied.

2.3.5.  Post route advertisements per-neighbor

   The adj-rib-out-post table is a per-neighbor table containing routes
   eligible for sending (advertising) to the neighbor after output
   policy rules have been applied

3.  Relation to other YANG data models

   The BGP model augments the Routing Management model A YANG Data Model
   for Routing Management [RFC8349] which defines the notion of routing,
   routing protocols, routing instances, or VRFs, and RIBs.  The notion of Virtual Routing and
   Forwarding (VRF) is derived by using the YANG Schema Mount [RFC8528]
   to mount the Routing Management module under the YANG Data Model for
   Network Instances [RFC8529].

4.  Security Considerations

   The YANG module specified in this document defines a schema for data
   that is designed to be accessed via network management protocols such
   as NETCONF [RFC6241] or RESTCONF [RFC8040].  The lowest NETCONF layer
   is the secure transport layer, and the mandatory-to-implement secure
   transport is Secure Shell (SSH) [RFC6242].  The lowest RESTCONF layer
   is HTTPS, and the mandatory-to-implement secure transport is TLS
   [RFC8446].  The NETCONF Access Control Model (NACM) [RFC8341]
   provides the means to restrict access for particular NETCONF or
   RESTCONF users to a preconfigured subset of all available NETCONF or
   RESTCONF protocol operations and content.

   There are a number of data nodes defined in this YANG module that are
   writable/creatable/deletable (i.e., config true, which is the
   default).  These data nodes may be considered sensitive or vulnerable
   in some network environments.  Write operations (e.g., edit-config)
   to these data nodes without proper protection can have a negative
   effect on network operations.  These are the subtrees and data nodes
   and their sensitivity/vulnerability:

   Some of the readable data nodes in this YANG module may be considered
   sensitive or vulnerable in some network environments.  It is thus
   important to control read access (e.g., via get, get-config, or
   notification) to these data nodes.  These are the subtrees and data
   nodes and their sensitivity/vulnerability:

   Some of the RPC operations in this YANG module may be considered
   sensitive or vulnerable in some network environments.  It is thus
   important to control access to these operations.  These are the
   operations and their sensitivity/vulnerability:

   BGP OPSEC [RFC7454] describes several policies that can be used to
   secure a BGP.  In particular, it recommends securing the underlying
   TCP session and to use Generalized TTL Security Mechanism (GTSM)
   [RFC5082] capability to make it harder to spoof a BGP session.  This
   module allows implementations that want to support the capability to
   configure a TTL value, under a feature flag.  It also defines a
   container 'secure-session' that can be augmented with TCP-
   Authentication Option (TCP-AO) [RFC5925], or other methods to secure
   a BGP session, and will be developed in a future version of this
   draft.

5.  IANA Considerations

   This document registers three URIs and three YANG modules.

5.1.  URI Registration

   in the IETF XML registry [RFC3688] [RFC3688].  Following the format
   in RFC 3688, the following registration is requested to be made:

   URI: urn:ietf:params:xml:ns:yang:ietf-bgp
   URI: urn:ietf:params:xml:ns:yang:ietf-bgp-policy
   URI: urn:ietf:params:xml:ns:yang:ietf-bgp-types

   Registrant Contact: The IESG.  XML: N/A, the requested URI is an XML
   namespace.

5.2.  YANG Module Name Registration

   This document registers three YANG module in the YANG Module Names
   registry YANG [RFC6020].

   name: ietf-bgp
   namespace: urn:ietf:params:xml:ns:yang:ietf-bgp
   prefix: bgp
   reference: RFC XXXX

   name: ietf-bgp-policy
   namespace: urn:ietf:params:xml:ns:yang:ietf-bgp-policy
   prefix: bp
   reference: RFC XXXX

   name: ietf-bgp-types
   namespace: urn:ietf:params:xml:ns:yang:ietf-bgp-types
   prefix: bt
   reference: RFC XXXX

6.  YANG modules

   The modules comprising the BGP configuration and operational model
   are described by the YANG modules and submodules in the sections
   below.

   The main module, ietf-bgp.yang, includes the following submodules:

   o  ietf-bgp-common - defines the groupings that are common across
      more than one context (where contexts are neighbor, group, global)

   o  ietf-bgp-common-multiprotocol - defines the groupings that are
      common across more than one context, and relate to multiprotocol
      BGP

   o  ietf-bgp-common-structure - defines groupings that are shared by
      multiple contexts, but are used only to create structural
      elements, i.e., containers (leaf nodes are defined in separate
      groupings)

   o  ietf-bgp-global - groupings with data specific to the global
      context

   o  ietf-bgp-peer-group - groupings with data specific to the peer
      group context

   o  ietf-bgp-neighbor - groupings with data specific to the neighbor
      context

   o  ietf-bgp-rib - grouping for representing BGP RIB.

   Additionally, modules include:

   o  ietf-bgp-types - common type and identity definitions for BGP,
      including BGP policy

   o  ietf-bgp-policy - BGP-specific policy data definitions for use
      with [I-D.ietf-rtgwg-policy-model] (described in more detail
      Section 2.2)

7.  Structure of the YANG modules

   The YANG model can be subdivided between the main module for base
   items, types, policy data, and the RIB module.

7.1.  Main module and submodules for base items

<CODE BEGINS> file "ietf-bgp@2019-06-13.yang" "ietf-bgp@2019-10-03.yang"
module ietf-bgp {
  yang-version 1.1;
  namespace "urn:ietf:params:xml:ns:yang:ietf-bgp";
  prefix bgp;

  /*
   * Import and Include
   */

  import ietf-routing {
    prefix rt;
    reference
      "RFC 8349, A YANG Data Model for Routing Management
       (NMDA Version)";
  }
  import ietf-routing-policy {
    prefix rpol;
    reference
      "RFC ZZZZ, A YANG Data Model for Routing Policy Management";
  }
  import ietf-interfaces {
    prefix if;
    reference
      "RFC 8343, A YANG Data Model for Interface Management.";
  }
  import ietf-bgp-types {
    prefix bt;
    reference
      "RFC XXXX, BGP YANG Model for Service Provider Network.";
  }
  import ietf-bfd-types {
    prefix bfd;
    reference
      "RFC BBBB, YANG Data Model for Bidirectional Forward Detection.";
  }
  import ietf-inet-types {
    prefix inet;
    reference
      "RFC 6991: Common YANG Data Types.";
  }
  import ietf-yang-types {
    prefix yang;
    reference
      "RFC 6991: Common YANG Data Types.";
  }

  include ietf-bgp-common;
  include ietf-bgp-common-multiprotocol;
  include ietf-bgp-common-structure;
  include ietf-bgp-neighbor;
  include ietf-bgp-peer-group;
  include ietf-bgp-rib-types;
  include ietf-bgp-rib;
  include ietf-bgp-rib-ext;
  include ietf-bgp-rib-attributes;
  include ietf-bgp-rib-table-attributes;
  include ietf-bgp-rib-tables;

  organization
    "IETF IDR Working Group";
  contact
    "WG Web:   <http://tools.ietf.org/wg/idr>
     WG List:  <idr@ietf.org>

     Authors: Mahesh Jethanandani (mjethanandani at gmail.com),
              Keyur Patel (keyur at arrcus.com),
              Susan Hares (shares at ndzh.com"; ndzh.com),
              Jeffrey Haas (jhaas at pfrc.org).";
  description
    "This module describes a YANG model for BGP protocol
     configuration. It is a limited subset of all of the configuration
     parameters available in the variety of vendor implementations,
     hence it is expected that it would be augmented with vendor-
     specific configuration data as needed. Additional modules or
     submodules to handle other aspects of BGP configuration,
     including policy, VRFs, VPNs, and additional address families
     are also expected.

     This model supports the following BGP configuration level
     hierarchy:

      BGP
        |
        +-> [ global BGP configuration ]
          +-> AFI / SAFI global
        +-> peer group
          +-> [ peer group config ]
          +-> AFI / SAFI [ per-AFI overrides ]
        +-> neighbor
          +-> [ neighbor config ]
          +-> [ optional pointer to peer-group ]
          +-> AFI / SAFI [ per-AFI overrides ]";

  revision 2019-06-13 2019-10-03 {
    description
      "Initial Version";
    reference
      "RFC XXXX, BGP Model for Service Provider Network ";
  }

  /*
   * Identity
   */

  identity bgp {
    base rt:routing-protocol;
    description
      "BGP protocol.";
  }
  /*
   * Feature(s)
   */
  feature clear-routes graceful-restart {
    description
      "Clearing of BGP routes
      "Graceful restart as defined in RFC 4724 is supported.";
  }

  feature clear-neighbors {
    description
      "Clearing of BGP neighbors is supported.";
  }

  feature clear-statistics {
    description
      "Clearing of BGP statistics is supported.";
  }

  /*
   * Containers
   */

  augment "/rt:routing/rt:control-plane-protocols/"
        + "rt:control-plane-protocol" {
    when "derived-from-or-self(rt:type, 'bgp')" {
      description
        "This augmentation is valid for a routing protocol
         instance of BGP.";
    }
    description
      "BGP protocol augmentation of ietf-routing module
       control-plane-protocol.";

    container bgp {
      description
        "Top-level configuration for the BGP router";

      container global {
        presence "Enables global configuration of BGP";
        description
          "Global configuration for the BGP router";

        leaf as {
          type inet:as-number;
          mandatory true;
          description
            "Local autonomous system number of the router.  Uses
             the 32-bit as-number type from the model in RFC 6991.";

        }

        leaf identifier {
          type yang:dotted-quad;
          description
            "BGP Identifier of the router - an unsigned 32-bit,
             non-zero integer that should be unique within an AS.
             The value of the BGP Identifier for a BGP speaker is
             determined upon startup and is the same for every local
             interface and BGP peer.";
          reference
            "RFC 6286: AS-Wide Unique BGP ID for BGP-4. Section 2.1";
        }

        container default-route-distance distance {
          description
            "Administrative distance (or preference) assigned to
             routes received from different sources
             (external, internal, and local).";

          leaf external-route-distance external {
            type uint8 {
              range "1..255";
            }
            description
              "Administrative distance for routes learned from
               external BGP (eBGP).";
          }
          leaf internal-route-distance internal {
            type uint8 {
              range "1..255";
            }
            description
              "Administrative distance for routes learned from
               internal BGP (iBGP).";
          }
        }

        container confederation {
          description
            "Configuration options specifying parameters when the
             local router is within an autonomous system which is
             part of a BGP confederation.";

          leaf enabled {
            type boolean;
            description
              "When this leaf is set to true it indicates that
               the local-AS is part of a BGP confederation";
          }

          leaf identifier {
            type inet:as-number;
            description
              "Confederation identifier for the autonomous system.";
          }

          leaf-list member-as {
            type inet:as-number;
            description
              "Remote autonomous systems that are to be treated
               as part of the local confederation.";
          }
        }

        container graceful-restart {
          if-feature graceful-restart;
          description
            "Parameters relating the graceful restart mechanism for
             BGP";
          uses graceful-restart-config;
        }

        uses global-group-use-multiple-paths;
        uses route-selection-options;

        container afi-safis {
          description
            "List of address-families associated with the BGP
             instance";
          list afi-safi {
            key "afi-safi-name";

            description
              "AFI,SAFI configuration available for the
               neighbour or group";

            uses mp-afi-safi-config;
            uses state;

            container graceful-restart {
              if-feature graceful-restart;
              description
                "Parameters relating to BGP graceful-restart";

              uses mp-afi-safi-graceful-restart-config;

            }

            uses route-selection-options;
            uses global-group-use-multiple-paths;
            uses mp-all-afi-safi-list-contents;
          }
        }
        uses rpol:apply-policy-group;
        uses state;
      }

      container neighbors {
        description
          "Configuration for BGP neighbors";

        list neighbor {
          key "remote-address";

          description
            "List of BGP neighbors configured on the local system,
             uniquely identified by remote IPv[46] address";

          leaf local-address {
            type inet:ip-address;
            config false;
            description
              "The local IP address of this entry's BGP connection.";
          }

          leaf local-port {
            type inet:port-number {
              range "0..65535";
            }
            config false;
            description
              "The local port for the TCP connection between
               the BGP peers.";
          }

          leaf peer-group {
            type leafref {
              path "../../../peer-groups/peer-group/peer-group-name";
            }
            description
              "The peer-group with which this neighbor is associated";
          }

          leaf identifier {
            type yang:dotted-quad;
            config false;
            description
              "The BGP Identifier of this entry's BGP peer.
               This entry MUST be 0.0.0.0 unless the
               sessionstate is in the openconfirm or the
               established state.";
            reference
              "RFC 4271, Section 4.2, 'BGP Identifier'.";
          }

          leaf remote-address {
            type inet:ip-address;
            description
              "The remote IP address of this entry's BGP peer.";
          }

          leaf remote-port {
            type inet:port-number {
              range "0..65535";
            }
            config false;
            description
              "The remote port for the TCP connection
               between the BGP peers.  Note that the
               objects local-addr, local-port, remote-addr, and
               reemote-port provide the appropriate
               reference to the standard MIB TCP
               connection table.";
          }

          leaf remote-as enabled {
            type inet:as-number;
            config false; boolean;
            default "true";
            description
              "The remote autonomous system number received in
               the BGP OPEN message.";
            reference
              "RFC 4271, Section 4.2.";
          }

          leaf enabled {
            type boolean;
            default "true";
            description
              "Whether
              "Whether the BGP peer is enabled. In cases where the
               enabled leaf is set to false, the local system should
               not initiate connections to the neighbor, and should
               not respond to TCP connections attempts from the
               neighbor. If the state of the BGP session is
               ESTABLISHED at the time that this leaf is set to false,
               the BGP session should be ceased.

               A transition from 'false' to 'true' will cause
               the BGP Manual Start Event to be generated.
               A transition from 'true' to 'false' will cause
               the BGP Manual Stop Event to be generated.
               This parameter can be used to restart BGP peer
               connections. Care should be used in providing
               write access to this object without adequate
               authentication.";
            reference
              "RFC 4271, Section 8.1.2.";
          }

          leaf ttl-security {
            if-feature "bt:ttl-security";
            type uint8;
            default "255";
            description
              "BGP Time To Live (TTL) security check.";
            reference
              "RFC 5082: The Genaralized TTL Security Mechanism
               (GTSM),
               RFC 7454: BGP Operations and Security.";
          }

          uses neighbor-group-config;
          uses route-selection-options;

          leaf session-state {
            type enumeration {
              enum idle {
                description
                  "Neighbor is down, and in the Idle state of the FSM";
              }
              enum connect {
                description
                  "Neighbor is down, and the session is waiting for the
                   underlying transport session to be established";
              }
              enum active {
                description
                  "Neighbor is down, and the local system is awaiting a
                   connection from the remote peer";
              }
              enum opensent {
                description
                  "Neighbor is in the process of being established.  The
                   local system has sent an OPEN message";
              }
              enum openconfirm {
                description
                  "Neighbor is in the process of being established.
                   The local system is awaiting a NOTIFICATION or
                   KEEPALIVE message";

              }
              enum established {
                description
                  "Neighbor is up - the BGP session with the peer is
                   established";
              }
            }
            //  notification does not like a non-config statement.
            //  config false;
            description
              "The BGP peer connection state.";
            reference
              "RFC 4271, Section 8.1.2.";
          }

          leaf last-established {
            type uint64;
            config false;
            description
              "This timestamp indicates the time that the BGP session
               last transitioned in or out of the Established state.
               The value is the timestamp in seconds relative to the
               Unix Epoch (Jan 1, 1970 00:00:00 UTC).

               The BGP session uptime can be computed by clients as
               the difference between this value and the current time
               in UTC (assuming the session is in the ESTABLISHED
               state, per the session-state leaf).";
          }

          leaf-list supported-capabilities {
            type identityref {
              base bt:bgp-capability;
            }
            config false;
            description
              "BGP capabilities negotiated as supported with the peer";
          }

          leaf negotiated-hold-time {
            type decimal64 {
              fraction-digits 2;
            }
            config false;
            description
              "The negotiated hold-time for the BGP session";
          }
          leaf last-error {
            type binary {
              length "2";
            }
            // notification does not like non-config statement.
            // config false;
            description
              "The last error code and subcode seen by this
               peer on this connection.  If no error has
               occurred, this field is zero.  Otherwise, the
               first byte of this two byte OCTET STRING
               contains the error code, and the second byte
               contains the subcode.";
            reference
              "RFC 4271, Section 4.5.";
          }

          leaf fsm-established-time {
            type yang:gauge32;
            units "seconds";
            config false;
            description
              "This timer indicates how long (in
               seconds) this peer has been in the
               established state or how long
               since this peer was last in the
               established state.  It is set to zero when
               a new peer is configured or when the router is
               booted.";
            reference
              "RFC 4271, Section 8.";
          }

          container timers {
            description
              "Timers related to a BGP neighbor";

            uses neighbor-group-timers-config;

          }

          container transport {
            description
              "Transport session parameters for the BGP neighbor";

            uses neighbor-group-transport-config;
          }
          leaf treat-as-withdraw {
            type boolean;
            default "false";
            description
              "Specify whether erroneous UPDATE messages for which
               the NLRI can be extracted are treated as though the
               NLRI is withdrawn - avoiding session reset";
            reference
              "RFC 7606: Revised Error Handling for BGP UPDATE
               Messages.";
          }

          leaf erroneous-update-messages {
            type uint32;
            config false;
            description
              "The number of BGP UPDATE messages for which the
               treat-as-withdraw mechanism has been applied based on
               erroneous message contents";
          }

          container graceful-restart {
            if-feature graceful-restart;
            description
              "Parameters relating the graceful restart mechanism for
               BGP";

            uses graceful-restart-config;

            leaf peer-restart-time {
              type uint16 {
                range "0..4096";
              }
              config false;
              description
                "The period of time (advertised by the peer) that the
                 peer expects a restart of a BGP session to take";
            }

            leaf peer-restarting {
              type boolean;
              config false;
              description
                "This flag indicates whether the remote neighbor is
                 currently in the process of restarting, and hence
                 received routes are currently stale";
            }
            leaf local-restarting {
              type boolean;
              config false;
              description
                "This flag indicates whether the local neighbor is
                 currently restarting. The flag is unset after all NLRI
                 have been advertised to the peer, and the End-of-RIB
                 (EOR) marker has been unset";
            }

            leaf mode {
              type enumeration {
                enum HELPER_ONLY helper-only {
                  description
                    "The local router is operating in helper-only
                     mode, and hence will not retain forwarding state
                     during a local session restart, but will do so
                     during a restart of the remote peer";
                }
                enum BILATERAL bilateral {
                  description
                    "The local router is operating in both helper
                     mode, and hence retains forwarding state during
                     a remote restart, and also maintains forwarding
                     state during local session restart";
                }
                enum REMOTE_HELPER remote-helper {
                  description
                    "The local system is able to retain routes during
                     restart but the remote system is only able to
                     act as a helper";
                }
              }
              config false;
              description
                "This leaf indicates the mode of operation of BGP
                 graceful restart with the peer";
            }
          }

          uses structure-neighbor-group-logging-options;
          uses structure-neighbor-group-ebgp-multihop;
          uses structure-neighbor-group-route-reflector;
          uses structure-neighbor-group-as-path-options;
          uses structure-neighbor-group-add-paths;
          uses bgp-neighbor-use-multiple-paths;
          uses rpol:apply-policy-group;
          container afi-safis {
            description
              "Per-address-family configuration parameters associated
               with the neighbor";
            uses bgp-neighbor-afi-safi-list;
          }

          container statistics {

            leaf established-transitions {
              type yang:counter64;
              config false;
              description
                "Number of transitions to the Established state for the
               neighbor session.  This value is analogous to the
               bgpPeerFsmEstablishedTransitions object from the standard
               BGP-4 MIB";
              reference
                "RFC 4273 - Definitions of Managed Objects for BGP-4";
            }

            leaf fsm-established-transitions {
              type yang:counter32;
              config false;
              description
                "The total number of times the BGP FSM
               transitioned into the established state
               for this peer.";
              reference
                "RFC 4271, Section 8.";
            }

            container messages {
              config false;
              description
                "Counters for BGP messages sent and received from the
               neighbor";

              leaf in-total-messages {
                type yang:counter32;
                config false;
                description
                  "The total number of messages received
                 from the remote peer on this connection.";
                reference
                  "RFC 4271, Section 4.";
              }
              leaf out-total-messages {
                type yang:counter32;
                config false;
                description
                  "The total number of messages transmitted to
                 the remote peer on this connection.";
                reference
                  "RFC 4271, Section 4.";
              }

              leaf in-update-elapsed-time {
                type yang:gauge32;
                units "seconds";
                config false;
                description
                  "Elapsed time (in seconds) since the last BGP
                 UPDATE message was received from the peer.
                 Each time in-updates is incremented,
                 the value of this object is set to zero (0).";
                reference
                  "RFC 4271, Section 4.3.
                 RFC 4271, Section 8.2.2, Established state.";
              }

              container sent {
                description
                  "Counters relating to BGP messages sent to the
                 neighbor";
                uses bgp-neighbor-counters-message-types-state;
              }

              container received {
                description
                  "Counters for BGP messages received from the
                   neighbor";
                uses bgp-neighbor-counters-message-types-state;
              }
            }

            container queues {
              config false;
              description
                "Counters related to queued messages associated with
                 the BGP neighbor";

              leaf input {
                type uint32;
                description
                  "The number of messages received from the peer
                   currently queued";
              }

              leaf output {
                type uint32;
                description
                  "The number of messages queued to be sent to the
                   peer";
              }
            }

            container clear-statistics {
              if-feature "clear-statistics";

              action clear {
                input {
                  leaf clear-at {
                    type yang:date-and-time;
                    description
                      "Time when the clear action needs to be
                       executed.";
                  }
                }

                output {
                  leaf clear-finished-at {
                    type yang:date-and-time;
                    description
                      "Time when the clear action command completed.";
                  }
                }
              }
              description
                "Clear statistics action command.";
            }
            description
              "Statistics per neighbor.";
          }
        }

        notification established {
          description
            "The established event is generated
             when the BGP FSM enters the established state.";

          leaf remote-address {
            type leafref {
              path "../../neighbor/remote-address";
            }
            description
              "IP address of the neighbor that went into established
               state.";
          }

          leaf last-error {
            type leafref {
              path "../../neighbor/last-error";
            }
            description
              "The last error code and subcode seen by this
               peer on this connection.  If no error has
               occurred, this field is zero.  Otherwise, the
               first byte of this two byte OCTET STRING
               contains the error code, and the second byte
               contains the subcode.";
            reference
              "RFC 4271, Section 4.5.";
          }

          leaf session-state {
            type leafref {
              path "../../neighbor/session-state";
            }
            description
              "The BGP peer connection state.";
            reference
              "RFC 4271, Section 8.2.2.";
          }
        }

        notification backward-transition {
          description
            "The backward-transition event is
             generated when the BGP FSM moves from a higher
             numbered state to a lower numbered state.";

          leaf remote-addr {
            type leafref {
              path "../../neighbor/remote-address";
            }
            description
              "IP address of the neighbor that went away from
               established state.";
          }
          leaf last-error {
            type leafref {
              path "../../neighbor/last-error";
            }
            description
              "The last error code and subcode seen by this
               peer on this connection.  If no error has
               occurred, this field is zero.  Otherwise, the
               first byte of this two byte OCTET STRING
               contains the error code, and the second byte
               contains the subcode.";
            reference
              "RFC 4271, Section 4.5.";
          }

          leaf session-state {
            type leafref {
              path "../../neighbor/session-state";
            }
            description
              "The BGP peer connection state.";
            reference
              "RFC 4271, Section 8.2.2.";
          }
        }

        container clear-neighbors {
          if-feature "clear-neighbors";

          action clear {
            input {
              leaf clear-at {
                type yang:date-and-time;
                description
                  "Time when the clear action command needs to be
                   executed.";
              }
            }

            output {
              leaf clear-finished-at {
                type yang:date-and-time;
                description
                  "Time when the clear action command completed.";
              }
            }
          }
          description
            "Clear neighbors action.";
        }
      }

      container peer-groups {
        description
          "Configuration for BGP peer-groups";
        uses bgp-peer-group-list;
      }

      container interfaces {
        list interface {
          key "name";

          leaf name {
            type if:interface-ref;
            description
              "Reference to the interface within the routing instance.";
          }

          container bfd {
            if-feature "bt:bfd";

            uses bfd:client-cfg-parms;
            description
              "BFD client configuration.";
            reference
              "RFC BBBB - YANG Data Model for Bidirectional Forwarding
               Detection.";
          }
          description
            "List of interfaces within the routing instance.";
        }
        description
          "Interface specific parameters.";
      }
      uses rib;
    }
  }
}
<CODE ENDS>

   <CODE BEGINS> file "ietf-bgp-common@2019-06-13.yang" "ietf-bgp-common@2019-10-03.yang"
   submodule ietf-bgp-common {
     yang-version "1.1";
     belongs-to ietf-bgp {
       prefix "bgp";
     }

     import ietf-bgp-types {
       prefix bt;
       reference
         "RFC XXXX: BGP Model for Service Provider Network.";
     }
     import ietf-inet-types {
       prefix inet;
       reference
         "RFC 6991: Common YANG Data Types.";
     }
     import ietf-yang-types {
       prefix yang;
       reference
         "RFC 6991: Common YANG Data Types.";
     }

     organization
       "IETF IDR Working Group";

     contact
       "WG Web:   <http://tools.ietf.org/wg/idr>
        WG List:  <idr@ietf.org>

        Authors: Mahesh Jethanandani (mjethanandani at gmail.com),
                 Keyur Patel (keyur at arrcus.com),
                 Susan Hares (shares at ndzh.com"; ndzh.com,
                 Jeffrey Haas (jhaas at pfrc.org).";

     description
       "This sub-module contains common groupings that are common across
        multiple contexts within the BGP module. That is to say that
        they may be application to a subset of global, peer-group or
        neighbor contexts.";

     revision "2019-06-13" "2019-10-03" {
       description
         "Initial Version";
       reference
         "RFC XXXX, BGP Model for Service Provider Network.";
     }

     /*
      * Features.
      */
     feature damping {
       description
         "Weighted route dampening is supported.";
     }

     grouping neighbor-group-timers-config {
       description
         "Config parameters related to timers associated with the BGP
          peer";

       leaf connect-retry-interval {
         type uint32 uint16 {
           range "1..65535"; "1..max";
         }
         units "seconds";
         default "120";
         description
           "Time interval (in seconds) for the ConnectRetryTimer. The
            suggested value for this timer is 120 seconds.";
         reference
           "RFC 4271, Section 8.2.2.  This is the value used
            to initialize the 'ConnectRetryTimer'.";
       }

       leaf hold-time {
         type uint32 uint16 {
           range "0 | 3..65535";
         }
         units "seconds";
         default "90";
         description
           "Time interval (in seconds) for the HoldTimer established
            with the peer.  The  When read as operational data (ro), the
            value of this object is calculated by this BGP speaker,
            using the smaller of the values in hold-time-configured hold-time that was
            configured (rw) in the running datastore and the Hold Time
            received in the OPEN message.

            This value must be at least three seconds
            if it is not zero (0).

            If the Hold Timer has not been established
            with the peer this object MUST have a value
            of zero (0).

            If the hold-time-configured configured value of hold-time object has was
            a value of (0), then when read this object MUST have a
            value of (0)."; (0) also.";
         reference
           "RFC 4271, Section 4.2."; 4.2.
            RFC 4271, Section 10.";
       }

       leaf keepalive-interval keepalive {
         type uint32 uint16 {
           range "0..21845";
         }
         units "seconds";
         default 30; "30";
         description
          "Time
           "When used as a configuration (rw) value, this Time interval
            (in seconds) for the KeepAlive timer established configured for this BGP
            speaker with the this peer. The value of this object will only
            determine the KEEPALIVE messages' frequency relative to
            the value specified in configured value for hold-time.

            If the value of this object is zero (0), no periodical
            KEEPALIVE messages are sent to the peer after the BGP
            connection has been established.  The suggested value for
            this timer is 30 seconds.;

            The actual time interval for the KEEPALIVE messages is
            indicated by operational value of keepalive. That value
            of this object is calculated by this BGP speaker such that,
            when compared with hold-time, it has the same proportion
            that keep-alive-configured keepalive has, compared with hold-time-configured.

           If the KeepAlive hold-time. A
            reasonable maximum value for this timer has not been established
           with the peer, this object MUST have a value
           of zero (0).

           If the of keep-alive-configured object
           has a value would be one third
            of (0), then this object MUST have
           a value that of (0)."; hold-time.";
         reference
           "RFC 4271, Section 4.4."; 4.4.
            RFC 4271, Section 10.";
       }

       leaf hold-time-configured min-as-origination-interval {
         type uint32 uint16 {
           range "0 | 3..65535"; "0..max";
         }
         units "seconds";
         default "15";
         description
           "Time interval (in seconds) for the Hold Time
           configured for this BGP speaker with this
           peer.  This value is placed in an OPEN
           message sent to this peer by this BGP
           speaker, and is compared with the Hold
           Time field in an OPEN message received
           from the peer when determining the Hold
           Time (hold-time) with the peer.
           This value must not be less than three
           seconds if it is not zero (0).  If it is
           zero (0), the Hold Time is NOT to be
           established with the peer. MinASOriginationInterval
            timer. The suggested value for this timer is 90 15 seconds.";
         reference
           "RFC 4271, Section 4.2. 9.2.1.2.
            RFC 4271, Section 10.";
       }
       leaf keep-alive-configured min-route-advertisement-interval {
         type uint32 uint16 {
           range "0..21845"; "0..max";
         }
         units "seconds";
         description
           "Time interval (in seconds) for the
           KeepAlive timer configured for this BGP
           speaker with this peer.  The value of this
           object will only determine the
           KEEPALIVE messages' frequency relative to
           the value specified in
           hold-time-configured; the actual
           time interval for the KEEPALIVE messages is
           indicated by keep-alive.  A
           reasonable maximum value for this timer
           would be one third of that of
           hold-time-configured.
           If the value of this object is zero (0),
           no periodical KEEPALIVE messages are sent
           to the peer after the BGP connection has
           been established.
            MinRouteAdvertisementInterval timer.
            The suggested value for this timer is 30 seconds.";
            seconds for EBGP connections and 5
            seconds for IBGP connections.";
         reference
           "RFC 4271, Section 4.4. 9.2.1.1.
            RFC 4271, Section 10.";
       }
     }

     grouping neighbor-group-config {
       description
         "Neighbor level configuration items.";

       leaf min-as-origination-interval remote-as {
         type uint32 {
          range "0..65535";
        }
        units "seconds"; inet:as-number;
         description
          "Time interval (in seconds) for the
           MinASOriginationInterval timer.
           The suggested value for this timer is 15
           seconds.";
        reference
          "RFC 4271, Section 9.2.1.2.
           RFC 4271, Section 10.";
      }

      leaf min-route-advertisement-interval {
        type uint32 {
          range "0..65535";
        }
        units "seconds";
        description
          "Time interval (in seconds) for
           "The remote autonomous system number received in
            the
           MinRouteAdvertisementInterval timer.
           The suggested value for this timer is 30
           seconds for EBGP connections and 5
           seconds for IBGP connections."; BGP OPEN message.";
         reference
           "RFC 4271, Section 9.2.1.1.
           RFC 4271, Section 10.";
      } 4.2.";
       }

    grouping neighbor-group-config {
      description
        "Neighbor level configuration items.";

       leaf peer-as {
         type inet:as-number;
         description
           "AS number of the peer.";
       }

       leaf local-as {
         type inet:as-number;
         description
           "The local autonomous system number that is to be used when
            establishing sessions with the remote peer or peer group, if
            this differs from the global BGP router autonomous system
            number.";
       }

       leaf peer-type {
           type bt:peer-type;
           description
             "Explicitly designate the peer or peer group as internal
              (iBGP) or external (eBGP).";
       }

       leaf auth-password {
        type string;
        description
          "Configures an MD5 authentication password for use with
           neighboring devices.";
      }

      leaf remove-private-as {
         // could also make this a container with a flag to enable
         // remove-private and separate option.  here, option implies
         // remove-private is enabled.
         type bt:remove-private-as-option;
         description
           "Remove private AS numbers from updates sent to peers - when
            this leaf is not specified, the AS_PATH attribute should be
            sent to the peer unchanged";
       }

       container route-flap-damping {
         if-feature damping;

         leaf description enable {
           type string;
        description
          "An optional textual boolean;
           default false;
           description (intended primarily for use
           with a peer or group";
      }
             "Enable route flap damping.";
         }

    grouping neighbor-group-transport-config

         leaf suppress-above {
           type decimal64 {
             fraction-digits 1;
           }
           default "3.0";
           description
        "Configuration parameters relating to
             "This is the transport protocol
         used by value of the BGP session to instability metric at which
              route suppression takes place. A route is not installed
              in the peer"; forwarding information base (FIB), or announced
              even if it is reachable during the period that it is
              suppressed.";
         }

         leaf tcp-mss reuse-above {
           type uint16; decimal64 {
             fraction-digits 1;
           }
           default "2.0";
           description
          "Sets
             "This is the max segment size for BGP TCP sessions."; value of the instability metric at which a
              suppressed route becomes unsuppressed if it is reachable
              but currently suppressed. The value assigned to
              reuse-below must be less than suppress-above.";

         }

         leaf mtu-discovery max-flap {
           type boolean; decimal64 {
             fraction-digits 1;
           }
           default false; "16.0";
           description
          "Turns path mtu discovery for BGP TCP sessions on (true) or
           off (false)";
             "This is the upper limit of the instability metric. This
              value must be greater than the larger of 1 and
              suppress-above.";
         }

         leaf passive-mode reach-decay {
           type boolean; yang:gauge32;
           units "seconds";
           default false; "300";
           description
          "Wait for
             "This value specifies the time desired for the instability
              metric value to reach one-half of its current value when
              the route is reachable. This half-life value determines
              the rate at which the metric value is decayed. A smaller
              half-life value makes a suppressed route reusable sooner
              than a larger value.";
         }

         leaf unreach-decay {
           type yang:gauge32;
           units "seconds";
           default "900";
           description
             "This value acts the same as reach-decay except that it
              specifies the rate at which the instability metric is
              decayed when a route is unreachable. It should have a
              value greater than or equal to reach-decay.";
         }

         leaf keep-history {
           type yang:gauge32;
           units "seconds";
           default "1800";
           description
             "This value specifies the period over which the route
              flapping history is to be maintained for a given route.
              The size of the configuration arrays described below is
              directly affected by this value.";
         }
         description
           "Routes learned via BGP are subject to weighted route
            dampening.";
       }

       leaf send-community {
         if-feature "bt:send-communities";
         type bt:community-type;
         description
           "When supported, this tells the router to propogate any
            prefixes that are attached to this community. The value
            of 0 implies 'none'.";
       }

       leaf description {
         type string;
         description
           "An optional textual description (intended primarily for use
            with a peer or group";
       }
     }

     grouping neighbor-group-transport-config {
       description
         "Configuration parameters relating to the transport protocol
          used by the BGP session to the peer";

       leaf tcp-mss {
         type uint16;
         description
           "Sets the max segment size for BGP TCP sessions.";
       }

       leaf mtu-discovery {
         type boolean;
         default false;
         description
           "Turns path mtu discovery for BGP TCP sessions on (true) or
            off (false)";
       }

       leaf passive-mode {
         type boolean;
         default false;
         description
           "Wait for peers to issue requests to open a BGP session,
            rather than initiating sessions from the local router.";
       }
       leaf local-address {
         type union {
           type inet:ip-address;
           type leafref {
             path "../../../../interfaces/interface/name";
           }
         }
         description
           "Set the local IP (either IPv4 or IPv6) address to use for
            the session when sending BGP update messages.  This may be
            expressed as either an IP address or reference to the name
            of an interface.";
       }
    }
    grouping graceful-restart-config {
      description
        "Configuration parameters relating to BGP graceful restart.";

      leaf enabled {
        type boolean;
        description
          "Enable or disable

       // TODO: Better form of authentication of the graceful-restart capability.";
      } BGP session should
       // be added here. It can be in the form of TCP-AO [RFC 5925],
       // IPsec, or any other protocol deemed desirable.
       leaf auth-password {
         type string;
         description
           "Configures an MD5 authentication password for use with
            neighboring devices.";
       }
     }

     grouping graceful-restart-config {
       description
         "Configuration parameters relating to BGP graceful restart.";

       leaf enabled {
         type boolean;
         description
           "Enable or disable the graceful-restart capability.";
       }

       leaf restart-time {
         type uint16 {
           range 0..4096;
         }
         description
           "Estimated time (in seconds) for the local BGP speaker to
            restart a session. This value is advertise in the graceful
            restart BGP capability.  This is a 12-bit value, referred to
            as Restart Time in RFC4724.  Per RFC4724, the suggested
            default value is <= the hold-time value.";
         reference
           "RFC 4724: Graceful Restart Mechanism for BGP.";
       }
       leaf stale-routes-time {
         type uint32;
         description
           "An upper-bound on the time that stale routes will be
            retained by a router after a session is restarted. If an
            End-of-RIB (EOR) marker is received prior to this timer
            expiring stale-routes will be flushed upon its receipt - if
            no EOR is received, then when this timer expires stale paths
            will be purged. This timer is referred to as the
            Selection_Deferral_Timer in RFC4724";
         reference
           "RFC 4724: Graceful Restart Mechanism for BGP.";
       }

       leaf helper-only {
         type boolean;
         default true;
         description
           "Enable graceful-restart in helper mode only. When this leaf
            is set, the local system does not retain forwarding its own
            state during a restart, but supports procedures for the
            receiving speaker, as defined in RFC4724.";
         reference
           "RFC 4724: Graceful Restart Mechanism for BGP.";
       }
     }

     grouping use-multiple-paths-config global-group-use-multiple-paths {
       description
        "Generic
         "Common grouping used for both global and groups which provides
          configuration options and state parameters relating to use of multiple
          paths";

       container use-multiple-paths {
         description
           "Parameters related to the use of multiple paths for a referenced AFI-SAFI, group or neighbor"; the
           same NLRI";

         leaf enabled {
           type boolean;
           default false;
           description
             "Whether the use of multiple paths for the same NLRI is
              enabled for the neighbor. This value is overridden by any
              more specific configuration value.";
         }
    }

    grouping use-multiple-paths-ebgp-as-options-config {
      description
        "Configuration parameters specific to eBGP multi-path applicable
         to all contexts";

      leaf allow-multiple-as {
       type boolean;
       default "false";
       description
        "Allow multi-path to use paths from different neighboring ASes.
         The default is to only consider multiple paths from the same
         neighboring AS.";
      }
    }

    grouping global-group-use-multiple-paths {
      description
        "Common grouping used for both global and groups which provides
         configuration and state parameters relating to use of multiple
         paths";

      container use-multiple-paths {
        description
          "Parameters related to the use of multiple paths for the
          same NLRI";

        uses use-multiple-paths-config;

         container ebgp {
           description
             "Multi-Path parameters for eBGP";

           leaf allow-multiple-as {
             type boolean;
             default "false";
             description
               "Allow multi-path to use paths from different neighboring
                ASes.  The default is to only consider multiple paths
                from the same neighboring AS.";
           }

           leaf maximum-paths {
             type uint32;
             default 1;
             description
               "Maximum number of parallel paths to consider when using
                BGP multi-path. The default is use a single path.";
           }
         }

         container ibgp {
           description
             "Multi-Path parameters for iBGP";

           leaf maximum-paths {
             type uint32;
             default 1;
             description
               "Maximum number of parallel paths to consider when using
                iBGP multi-path. The default is to use a single path";
           }
         }
       }
     }

     grouping route-selection-options {
       description
         "Configuration and state relating to route selection options";

       container route-selection-options {
         description
           "Parameters relating to options for route selection";

         leaf enable-aigp always-compare-med {
           type boolean;
           default false; "false";
           description
            "Flag
             "Compare multi-exit discriminator (MED) value from
              different ASes when selecting the best route.  The default
              behavior is to enable sending / receiving accumulated IGP
             attribute in routing updates";
        }
      } only compare MEDs for paths received from
              the same AS.";
         }

    grouping state {
      description
        "Grouping containing common counters relating to prefixes and
         paths";

         leaf total-paths ignore-as-path-length {
           type uint32; boolean;
           default "false";
           description
             "Ignore the AS path length when selecting the best path.
              The default is to use the AS path length and prefer paths
              with shorter length.";
         }

         leaf external-compare-router-id {
           type boolean;
           default "true";
           description
             "When comparing similar routes received from external BGP
              peers, use the router-id as a criterion to select the
              active path.";
         }

         leaf advertise-inactive-routes {
           type boolean;
           default "false";
           description
             "Advertise inactive routes to external peers.  The default
              is to only advertise active routes.";
           reference
             "I-D.ietf-idr-best-external: Advertisement of the best
              external route in BGP.";
         }

         leaf enable-aigp {
           type boolean;
           default false;
           description
             "Flag to enable sending / receiving accumulated IGP
              attribute in routing updates";
           reference
             "RFC 7311: AIGP Metric Attribute for BGP.";
         }

         leaf ignore-next-hop-igp-metric {
           type boolean;
           default "false";
           description
             "Ignore the IGP metric to the next-hop when calculating BGP
              best-path. The default is to select the route for which
              the metric to the next-hop is lowest";
         }

         leaf enable-med {
           type boolean;
           default false;
           description
             "Flag to enable sending/receiving of MED metric attribute
              in routing updates.";
         }
       }
     }

     grouping state {
       description
         "Grouping containing common counters relating to prefixes and
          paths";

       leaf total-paths {
         type uint32;
         config false;
         description
           "Total number of BGP paths within the context";
       }

       leaf total-prefixes {
         type uint32;
         config false;
         description
           "Total number of BGP prefixes received within the context";
       }
     }
   }
   <CODE ENDS>

   <CODE BEGINS> file "ietf-bgp-common-multiprotocol@2019-06-13.yang" "ietf-bgp-common-multiprotocol@2019-10-03.yang"
   submodule ietf-bgp-common-multiprotocol {
     yang-version "1.1";
     belongs-to ietf-bgp {
       prefix "bgp";
     }

     import ietf-bgp-types {
       prefix bt;

     }
     import ietf-routing-policy {
       prefix rpol;
     }

     include ietf-bgp-common;

     // meta
     organization
       "IETF IDR Working Group";

     contact
       "WG Web:   <http://tools.ietf.org/wg/idr>
        WG List:  <idr@ietf.org>

        Authors: Mahesh Jethanandani (mjethanandani at gmail.com),
                 Keyur Patel (keyur at arrcus.com),
                 Susan Hares (shares at ndzh.com)";

     description
       "This sub-module contains groupings that are related to support
        for multiple protocols in BGP. The groupings are common across
        multiple contexts.";

     revision "2019-06-13" "2019-10-03" {
       description
         "Initial Version";
       reference
         "RFC XXX, BGP Model for Service Provider Network.";
     }

     grouping mp-afi-safi-graceful-restart-config {
       description
         "BGP graceful restart parameters that apply on a per-AFI-SAFI
          basis";

       leaf enabled {
         type boolean;
         default false;
         description
           "This leaf indicates whether graceful-restart is enabled for
            this AFI-SAFI";
       }
     }

     grouping mp-afi-safi-config {
       description
         "Configuration parameters used for all BGP AFI-SAFIs";

       leaf afi-safi-name {
         type identityref {
           base "bt:afi-safi-type";
         }
         description "AFI,SAFI";
       }

       leaf enabled {
         type boolean;
         default false;
         description
           "This leaf indicates whether the IPv4 Unicast AFI,SAFI is
           enabled for the neighbour or group";
       }
     }

     grouping mp-all-afi-safi-list-contents {
       description
         "A common grouping used for contents of the list that is used
          for AFI-SAFI entries";

       // import and export policy included for the afi/safi
       uses rpol:apply-policy-group;

       container ipv4-unicast {
         when "../afi-safi-name = 'bt:ipv4-unicast'" {
           description
             "Include this container for IPv4 Unicast specific
              configuration";
         }

         description
           "IPv4 unicast configuration options";

         // include common IPv[46] unicast options
         uses mp-ipv4-ipv6-unicast-common;

         // placeholder for IPv4 unicast  specific configuration
       }

       container ipv6-unicast {
         when "../afi-safi-name = 'bt:ipv6-unicast'" {
           description
             "Include this container for IPv6 Unicast specific
              configuration";
         }

         description
           "IPv6 unicast configuration options";

         // include common IPv[46] unicast options
         uses mp-ipv4-ipv6-unicast-common;

         // placeholder for IPv6 unicast specific configuration
         // options
       }

       container ipv4-labeled-unicast {
         when "../afi-safi-name = 'bt:ipv4-labeled-unicast'" {
           description
             "Include this container for IPv4 Labeled Unicast specific
              configuration";
         }

         description
           "IPv4 Labeled Unicast configuration options";

         uses mp-all-afi-safi-common;

         // placeholder for IPv4 Labeled Unicast specific config
         // options
       }

       container ipv6-labeled-unicast {
         when "../afi-safi-name = 'bt:ipv6-labeled-unicast'" {
           description
             "Include this container for IPv6 Labeled Unicast specific
              configuration";
         }

         description
           "IPv6 Labeled Unicast configuration options";

         uses mp-all-afi-safi-common;

         // placeholder for IPv6 Labeled Unicast specific config
         // options.
       }

       container l3vpn-ipv4-unicast {
         when "../afi-safi-name = 'bt:l3vpn-ipv4-unicast'" {
           description
             "Include this container for IPv4 Unicast L3VPN specific
              configuration";
         }
         description
           "Unicast IPv4 L3VPN configuration options";

         // include common L3VPN configuration options
         uses mp-l3vpn-ipv4-ipv6-unicast-common;

         // placeholder for IPv4 Unicast L3VPN specific config options.
       }

       container l3vpn-ipv6-unicast {
         when "../afi-safi-name = 'bt:l3vpn-ipv6-unicast'" {
           description
             "Include this container for unicast IPv6 L3VPN specific
              configuration";
         }

         description
           "Unicast IPv6 L3VPN configuration options";

         // include common L3VPN configuration options
         uses mp-l3vpn-ipv4-ipv6-unicast-common;

         // placeholder for IPv6 Unicast L3VPN specific configuration
         // options
       }

       container l3vpn-ipv4-multicast {
         when "../afi-safi-name = 'bt:l3vpn-ipv4-multicast'" {
           description
             "Include this container for multicast IPv6 L3VPN specific
              configuration";
         }

         description
           "Multicast IPv4 L3VPN configuration options";

         // include common L3VPN multicast options
         uses mp-l3vpn-ipv4-ipv6-multicast-common;

         // placeholder for IPv4 Multicast L3VPN specific configuration
         // options
       }

       container l3vpn-ipv6-multicast {
         when "../afi-safi-name = 'bt:l3vpn-ipv6-multicast'" {
           description
             "Include this container for multicast IPv6 L3VPN specific
              configuration";

         }
         description
           "Multicast IPv6 L3VPN configuration options";

         // include common L3VPN multicast options
         uses mp-l3vpn-ipv4-ipv6-multicast-common;

         // placeholder for IPv6 Multicast L3VPN specific configuration
         // options
       }

       container l2vpn-vpls {
         when "../afi-safi-name = 'bt:l2vpn-vpls'" {
           description
             "Include this container for BGP-signalled VPLS specific
              configuration";
         }

         description
           "BGP-signalled VPLS configuration options";

         // include common L2VPN options
         uses mp-l2vpn-common;

         // placeholder for BGP-signalled VPLS specific configuration
         // options
       }

       container l2vpn-evpn {
         when "../afi-safi-name = 'bt:l2vpn-evpn'" {
           description
             "Include this container for BGP EVPN specific
              configuration";
         }

         description
           "BGP EVPN configuration options";

         // include common L2VPN options
         uses mp-l2vpn-common;

         // placeholder for BGP EVPN specific configuration options
       }
     }

     // Common groupings across multiple AFI,SAFIs
     grouping mp-all-afi-safi-common {
       description
         "Grouping for configuration common to all AFI,SAFI";

       container prefix-limit {
         description
           "Parameters relating to the prefix limit for the AFI-SAFI";
         leaf max-prefixes {
           type uint32;
           description
             "Maximum number of prefixes that will be accepted from the
              neighbour";
         }
         leaf shutdown-threshold-pct {
           type bt:percentage;
           description
             "Threshold on number of prefixes that can be received from
              a neighbour before generation of warning messages or log
              entries. Expressed as a percentage of max-prefixes";
         }

         leaf restart-timer {
           type decimal64 {
             fraction-digits 2;
           } uint32;
           units "seconds";
           description
             "Time interval in seconds after which the BGP session is
              re-established after being torn down due to exceeding the
              max-prefix limit.";
         }
       }
     }

     grouping mp-ipv4-ipv6-unicast-common {
       description
         "Common configuration that is applicable for IPv4 and IPv6
         unicast";

       // include common afi-safi options.
       uses mp-all-afi-safi-common;

       // configuration options that are specific to IPv[46] unicast
       leaf send-default-route {
         type boolean;
         default "false";
         description
           "If set to true, send the default-route to the neighbour(s)";
       }
     }

     grouping mp-l3vpn-ipv4-ipv6-unicast-common {
       description
         "Common configuration applied across L3VPN for IPv4
          and IPv6";

       // placeholder -- specific configuration options that are generic
       // across IPv[46] unicast address families.
       uses mp-all-afi-safi-common;
     }

     grouping mp-l3vpn-ipv4-ipv6-multicast-common {
       description
         "Common configuration applied across L3VPN for IPv4
         and IPv6";

       // placeholder -- specific configuration options that are
       // generic across IPv[46] multicast address families.
       uses mp-all-afi-safi-common;
     }

     grouping mp-l2vpn-common {
       description
         "Common configuration applied across L2VPN address
         families";

       // placeholder -- specific configuration options that are
       // generic across L2VPN address families
       uses mp-all-afi-safi-common;
     }

     // Config groupings for common groups
     grouping mp-all-afi-safi-common-prefix-limit-config {
       description
         "Configuration parameters relating to prefix-limits for an
         AFI-SAFI";

     }
   }
   <CODE ENDS>

 <CODE BEGINS> file "ietf-bgp-common-structure@2019-06-13.yang" "ietf-bgp-common-structure@2019-10-03.yang"
 submodule ietf-bgp-common-structure {
   yang-version "1.1";
   belongs-to ietf-bgp {
     prefix "bgp";
   }

   import ietf-bgp-types { prefix bt; }
   import ietf-routing-policy { prefix rpol; }
   include ietf-bgp-common-multiprotocol;
   include ietf-bgp-common;

   // meta
   organization
     "IETF IDR Working Group";

   contact
     "WG Web:   <http://tools.ietf.org/wg/idr>
      WG List:  <idr@ietf.org>

      Authors: Mahesh Jethanandani (mjethanandani at gmail.com),
               Keyur Patel (keyur at arrcus.com),
               Susan Hares (shares at ndzh.com)"; ndzh.com),
               Jeffrey Haas (jhaas at pfrc.org).";

   description
     "This sub-module contains groupings that are common across
      multiple BGP contexts and provide structure around other
      primitive groupings.";

   revision "2019-06-13" "2019-10-03" {
     description
       "Initial Version";
     reference
       "RFC XXX, BGP Model for Service Provider Network.";
   }

   grouping structure-neighbor-group-logging-options {
     description
       "Structural grouping used to include error handling
        configuration and state for both BGP neighbors and groups";

     container logging-options {
       description
         "Logging options for events related to the BGP neighbor or
         group";

       leaf log-neighbor-state-changes {
         type boolean;
         default "true";
         description
           "Configure logging of peer state changes.  Default is to
            enable logging of peer state changes.

            Note: Documenting out of ESTABLISHED state is desirable,
                  but documenting all backward transitions is
                  problematic, and should be avoided.";
       }
     }
   }

   grouping structure-neighbor-group-ebgp-multihop {
     description
       "Structural grouping used to include eBGP multi-hop
        configuration and state for both BGP neighbors and peer
        groups";

     container ebgp-multihop {
       description
         "eBGP multi-hop parameters for the BGPgroup";

       leaf enabled {
         type boolean;
         default "false";
         description
           "When enabled the referenced group or neighbors are
            permitted to be indirectly connected - including cases
            where the TTL can be decremented between the BGP peers";
       }

       leaf multihop-ttl {
         type uint8;
         description
           "Time-to-live value to use when packets are sent to the
            referenced group or neighbors and ebgp-multihop is
            enabled";
       }
     }
   }

   grouping structure-neighbor-group-route-reflector {
     description
       "Structural grouping used to include route reflector
        configuration and state for both BGP neighbors and peer
        groups";

     container route-reflector {
       description
         "Route reflector parameters for the BGPgroup";
       reference
         "RFC 4456: BGP Route Reflection.";

       leaf route-reflector-cluster-id {
         when "../route-reflector-client = 'false'";
         type bt:rr-cluster-id-type;
         description
             "route-reflector
           "Route Reflector cluster id to use when local router is
            configured as a route reflector.  Commonly set at the
            group level, but allows a different cluster id to be set
            for each neighbor.";
         reference
           "RFC 4456: BGP Route Reflection: An Alternative to
            Full Mesh.";
       }

       leaf no-client-reflect {
         type boolean;
         default "false";
         description
           "When set to 'true', this disables route redistribution
            by the Route Reflector. It is set 'true' when the client is
            fully meshed to prevent sending of redundant route
            advertisements.";
         reference
           "TODO: Add reference when IETF writes a draft describing
            this.";
       }

       leaf route-reflector-client {
         type boolean;
         default "false";
         description
           "Configure the neighbor as a route reflector client.";
         reference
           "RFC 4456: BGP Route Reflection: An Alternative to
            Full Mesh.";
       }
     }
   }

   grouping structure-neighbor-group-as-path-options {
     description
       "Structural grouping used to include AS_PATH manipulation
        configuration and state for both BGP neighbors and peer
        groups";

     container as-path-options {
       description
         "AS_PATH manipulation parameters for the BGP neighbor or
          group";

       leaf allow-own-as {
         type uint8;
         default 0;
         description
           "Specify the number of occurrences of the local BGP
            speaker's AS that can occur within the AS_PATH before it
            is rejected.";
       }

       leaf replace-peer-as {
         type boolean;
         default "false";
         description
           "Replace occurrences of the peer's AS in the AS_PATH with
            the local autonomous system number";
       }
     }
   }

   grouping structure-neighbor-group-add-paths {
     description
       "Structural grouping used to include ADD-PATHs configuration
        and state for both BGP neighbors and peer groups";

     container add-paths {
       description
         "Parameters relating to the advertisement and receipt of
          multiple paths for a single NLRI (add-paths)";
       reference
         "RFC 7911: ADD-PATH.";

       leaf receive {
         type boolean;
         default false;
         description
           "Enable ability to receive multiple path advertisements for
            an NLRI from the neighbor or group";
       }

       choice send {
         default "all";
         description
           "Choice of sending the max. number of paths or to send all.";

         case max {
           leaf send-max max {
             type uint8;
             description
               "The maximum number of paths to advertise to neighbors
                for a single NLRI";
           }
         }

         case all {
           leaf all {
             type empty;
             description
               "Send all the path advertisements to neighbors for a
                single NLRI.";
           }
         }
       }

       leaf eligible-prefix-policy {
         type leafref {
           path "/rpol:routing-policy/rpol:policy-definitions/" +
                "rpol:policy-definition/rpol:name";
         }
         description
           "A reference to a routing policy which can be used to
            restrict the prefixes for which add-paths is enabled";
       }
     }
   }
 }
 <CODE ENDS>

  <CODE BEGINS> file "ietf-bgp-peer-group@2019-06-13.yang" "ietf-bgp-peer-group@2019-10-03.yang"
  submodule ietf-bgp-peer-group {
    yang-version "1.1";
    belongs-to ietf-bgp {
      prefix "bgp";
    }

    import ietf-routing-policy {
      prefix rpol;
    }

    // Include the common submodule
    include ietf-bgp-common;
    include ietf-bgp-common-multiprotocol;
    include ietf-bgp-common-structure;

    // meta
    organization
      "IETF IDR Working Group";

    contact
      "WG Web:   <http://tools.ietf.org/wg/idr>
       WG List:  <idr@ietf.org>

       Authors: Mahesh Jethanandani (mjethanandani at gmail.com),
                Keyur Patel (keyur at arrcus.com),
                Susan Hares (shares at ndzh.com)"; ndzh.com),
                Jeffrey Haas (jhaas at pfrc.org).";

    description
      "This sub-module contains groupings that are specific to the
       peer-group context of the OpenConfig BGP module.";

    revision "2019-06-13" "2019-10-03" {
      description
        "Initial Version";
      reference
        "RFC XXX, BGP Model for Service Provider Network.";
    }

    grouping bgp-peer-group-config {
      description
        "Configuration parameters relating to a base BGP peer group
         that are not also applicable to any other context (e.g.,
         neighbor)";

      leaf peer-group-name {
        type string;
        description
          "Name of the BGP peer-group";
      }

    }

    grouping bgp-peer-group-afi-safi-list {
      description
        "List of address-families associated with the BGP peer-group";

      list afi-safi {
        key "afi-safi-name";

        description
          "AFI, SAFI configuration available for the
           neighbour or group";

        uses mp-afi-safi-config;

        container graceful-restart {
          if-feature graceful-restart;
          description
            "Parameters relating to BGP graceful-restart";

          uses mp-afi-safi-graceful-restart-config;
        }

        uses route-selection-options;
        uses global-group-use-multiple-paths;
        uses mp-all-afi-safi-list-contents;
      }
    }
    grouping bgp-peer-group-base {
      description
        "Parameters related to a BGP group.";

      uses bgp-peer-group-config;

      leaf peer-group-name {
        type string;
        description
          "Name of the BGP peer-group";
      }

      uses neighbor-group-config;
      uses state;

      container timers {
        description
          "Timers related to a BGP peer-group.";

        uses neighbor-group-timers-config;
      }

      container transport {
        description
          "Transport session parameters for the BGP peer-group.";

        uses neighbor-group-transport-config;
      }

      container graceful-restart {
        if-feature graceful-restart;
        description
          "Parameters relating the graceful restart mechanism for BGP.";

        uses graceful-restart-config;
      }

      uses structure-neighbor-group-ebgp-multihop;
      uses structure-neighbor-group-route-reflector;
      uses structure-neighbor-group-as-path-options;
      uses structure-neighbor-group-add-paths;
      uses global-group-use-multiple-paths;
      uses rpol:apply-policy-group;

      container afi-safis {
        description
          "Per-address-family configuration parameters associated with
           the group.";
        uses bgp-peer-group-afi-safi-list;
      }
    }
    grouping bgp-peer-group-list {
      description
        "The list of BGP peer groups";

      list peer-group {
        key "peer-group-name";
        description
          "List of BGP peer-groups configured on the local system -
           uniquely identified by peer-group name";

        uses bgp-peer-group-base;
      }
    }
  }
  <CODE ENDS>

  <CODE BEGINS> file "ietf-bgp-neighbor@2019-06-13.yang" "ietf-bgp-neighbor@2019-10-03.yang"
  submodule ietf-bgp-neighbor {
    yang-version "1.1";
    belongs-to ietf-bgp {
      prefix "bgp";
    }

    // Include the common submodule
    include ietf-bgp-common;
    include ietf-bgp-common-multiprotocol;
    include ietf-bgp-peer-group;
    include ietf-bgp-common-structure;

    // meta
    organization
      "IETF IDR Working Group";

    contact
      "WG Web:   <http://tools.ietf.org/wg/idr>
       WG List:  <idr@ietf.org>

       Authors: Mahesh Jethanandani (mjethanandani at gmail.com),
                Keyur Patel (keyur at arrcus.com),
                Susan Hares (shares at ndzh.com)"; ndzh.com),
                Jeffrey Haas (jhaas at pfrc.org).";

    description
      "This sub-module contains groupings that are specific to the
       neighbor context of the BGP module.";

    revision "2019-06-13" "2019-10-03" {
      description
        "Initial Version";
      reference
        "RFC XXX, BGP Model for Service Provider Network.";
    }

    grouping bgp-neighbor-use-multiple-paths {
      description
        "Multi-path configuration and state applicable to a BGP
         neighbor";

      container use-multiple-paths {
        description
          "Parameters related to the use of multiple-paths for the same
           NLRI when they are received only from this neighbor";

        uses use-multiple-paths-config;

        leaf enabled {
          type boolean;
          default false;
          description
            "Whether the use of multiple paths for the same NLRI is
             enabled for the neighbor. This value is overridden by any
             more specific configuration value.";
        }

        container ebgp {
          description
            "Multi-path configuration for eBGP";
          uses use-multiple-paths-ebgp-as-options-config;

          leaf allow-multiple-as {
            type boolean;
            default "false";
            description
              "Allow multi-path to use paths from different neighboring
               ASes. The default is to only consider multiple paths
               from the same neighboring AS.";
          }
        }
      }
    }

    grouping bgp-neighbor-counters-message-types-state {
      description
        "Grouping of BGP message types, included for re-use across
         counters";

      leaf updates-received {
        type uint64;
        description
          "Number of BGP UPDATE messages received from this neighbor.";
        reference
          "RFC 4273: bgpPeerInUpdates.";
      }

      leaf updates-sent {
        type uint64;
        description
          "Number of BGP UPDATE messages sent to this neighbor";
        reference
          "RFC 4273 - bgpPeerOutUpdates";
      }

      leaf messages-received {
        type uint64;
        description
          "Number of BGP messages received from thsi neighbor";
        reference
          "RFC 4273 - bgpPeerInTotalMessages";
      }

      leaf messages-sent {
        type uint64;
        description
          "Number of BGP messages received from thsi neighbor";
        reference
          "RFC 4273 - bgpPeerOutTotalMessages";
      }

      leaf notification {
        type uint64;
        description
          "Number of BGP NOTIFICATION messages indicating an error
           condition has occurred exchanged.";
      }
    }

    grouping bgp-neighbor-afi-safi-list {
      description
        "List of address-families associated with the BGP neighbor";

      list afi-safi {
        key "afi-safi-name";

        description
          "AFI, SAFI configuration available for the neighbor or
           group";

        uses mp-afi-safi-config;

        leaf active {
          type boolean;
          config false;
          description
            "This value indicates whether a particular AFI-SAFI has
             been successfully negotiated with the peer. An AFI-SAFI may
             be enabled in the current running configuration, but a
             session restart may be required in order to negotiate the
             new capability.";
        }

        container prefixes {
          config false;
          description
            "Prefix counters for the BGP session";

          leaf received {
            type uint32;
            description
              "The number of prefixes received from the neighbor";
          }

          leaf sent {
            type uint32;
            description
              "The number of prefixes advertised to the neighbor";
          }

          leaf installed {
            type uint32;
            description
              "The number of advertised prefixes installed in the
               Loc-RIB";
          }
        }

        container graceful-restart {
          if-feature bgp:graceful-restart;
          description
            "Parameters relating to BGP graceful-restart";

          uses mp-afi-safi-graceful-restart-config;

          leaf received {
            type boolean;
            config false;
            description
              "This leaf indicates whether the neighbor advertised the
               ability to support graceful-restart for this AFI-SAFI";
          }

          leaf advertised {
            type boolean;
            config false;
            description
              "This leaf indicates whether the ability to support
               graceful-restart has been advertised to the peer";
          }
        }

        uses mp-all-afi-safi-list-contents;
        uses bgp-neighbor-use-multiple-paths;
      }
    }
  }
  <CODE ENDS>

7.2.  BGP types

  <CODE BEGINS> file "ietf-bgp-types@2019-06-13.yang" "ietf-bgp-types@2019-10-03.yang"
  module ietf-bgp-types {
    yang-version "1.1";
    namespace "urn:ietf:params:xml:ns:yang:ietf-bgp-types";

    prefix "bt";

    import ietf-inet-types {
      prefix inet;
    }

    // meta
    organization
      "IETF IDR Working Group";

    contact
      "WG Web:   <http://tools.ietf.org/wg/idr>
       WG List:  <idr@ietf.org>

       Authors: Mahesh Jethanandani (mjethanandani at gmail.com),
                Keyur Patel (keyur at arrcus.com),
                Susan Hares (shares at ndzh.com)"; ndzh.com),
                Jeffrey Haas (jhaas at pfrc.org).";

    description
      "This module contains general data definitions for use in BGP
       policy. It can be imported by modules that make use of BGP
       attributes";

    revision "2019-06-13" "2019-10-03" {
      description
        "Initial Version";
      reference
        "RFC XXX, BGP Model for Service Provider Network.";
    }

    identity bgp-capability {
      description "Base identity for a BGP capability";
    }

    identity mp-bgp {
      base bgp-capability;
      description
        "Multi-protocol extensions to BGP";
      reference
        "RFC 4760";
    }

    identity route-refresh {
      base bgp-capability;
      description
        "The BGP route-refresh functionality";
      reference
        "RFC2918";
    }

    identity asn32 {
      base bgp-capability;
      description
        "4-byte (32-bit) AS number functionality";
      reference
        "RFC6793";
    }

    identity graceful-restart {
      base bgp-capability;
      description
        "Graceful restart functionality";
      reference
        "RFC4724";
    }
    identity add-paths {
      base bgp-capability;
      description
        "BGP add-paths";
      reference
        "RFC 7911.";
    }

    identity afi-safi-type {
      description
        "Base identity type for AFI,SAFI tuples for BGP-4";
      reference
        "RFC4760 - multi-protocol extensions for BGP-4";
    }

    identity ipv4-unicast {
      base afi-safi-type;
      description
        "IPv4 unicast (AFI,SAFI = 1,1)";
      reference
        "RFC4760";
    }

    identity ipv6-unicast {
      base afi-safi-type;
      description
        "IPv6 unicast (AFI,SAFI = 2,1)";
      reference
        "RFC4760";
    }

    identity ipv4-labeled-unicast {
      base afi-safi-type;
      description
        "Labeled IPv4 unicast (AFI,SAFI = 1,4)";
      reference
        "RFC3107";
    }

    identity ipv6-labeled-unicast {
      base afi-safi-type;
      description
        "Labeled IPv6 unicast (AFI,SAFI = 2,4)";
      reference
        "RFC3107";
    }

    identity l3vpn-ipv4-unicast {
      base afi-safi-type;
      description
        "Unicast IPv4 MPLS L3VPN (AFI,SAFI = 1,128)";
      reference
        "RFC4364";
    }

    identity l3vpn-ipv6-unicast {
      base afi-safi-type;
      description
        "Unicast IPv6 MPLS L3VPN (AFI,SAFI = 2,128)";
      reference
        "RFC4659";
    }

    identity l3vpn-ipv4-multicast {
      base afi-safi-type;
      description
        "Multicast IPv4 MPLS L3VPN (AFI,SAFI = 1,129)";
      reference
        "RFC6514";
    }

    identity l3vpn-ipv6-multicast {
      base afi-safi-type;
      description
        "Multicast IPv6 MPLS L3VPN (AFI,SAFI = 2,129)";
      reference
        "RFC6514";
    }

    identity l2vpn-vpls {
      base afi-safi-type;
      description
        "BGP-signalled VPLS (AFI,SAFI = 25,65)";
      reference
        "RFC4761";
    }

    identity l2vpn-evpn {
      base afi-safi-type;
      description
        "BGP MPLS Based Ethernet VPN (AFI,SAFI = 25,70)";
    }

    identity BGP_WELL_KNOWN_STD_COMMUNITY bgp-well-known-std-community {
      description
        "Reserved
        "Base identity for reserved communities within the standard
         community space defined by RFC1997. These communities must
         fall within the range 0xFFFF0000 to 0xFFFFFFFF";
      reference
        "RFC 1997"; 1997: BGP Communities Attribute.";
    }

    identity NO_EXPORT no-export {
      base BGP_WELL_KNOWN_STD_COMMUNITY; bgp-well-known-std-community;
      description
        "Do not export NLRI received carrying this community outside
         the bounds of this autonomous system, or this confederation if
         the local autonomous system is a confederation member AS. This
         community has a value of 0xFFFFFF01.";
      reference
        "RFC1997";
        "RFC 1997: BGP Communities Attribute.";
    }

    identity NO_ADVERTISE no-advertise {
      base BGP_WELL_KNOWN_STD_COMMUNITY; bgp-well-known-std-community;
      description
        "All NLRI received carrying this community must not be
         advertised to other BGP peers. This community has a value of
         0xFFFFFF02.";
      reference
        "RFC1997";
        "RFC 1997: BGP Communities Attribute.";
    }

    identity NO_EXPORT_SUBCONFED no-export-subconfed {
      base BGP_WELL_KNOWN_STD_COMMUNITY; bgp-well-known-std-community;
      description
        "All NLRI received carrying this community must not be
         advertised to external BGP peers - including over confederation
         sub-AS boundaries. This community has a value of 0xFFFFFF03.";
      reference
        "RFC1997";
        "RFC 1997: BGP Communities Attribute.";
    }

    identity NOPEER no-peer {
      base BGP_WELL_KNOWN_STD_COMMUNITY; bgp-well-known-std-community;
      description
        "An autonomous system receiving NLRI tagged with this community
         is advised not to re-advertise the NLRI to external bi-lateral
         peer autonomous systems. An AS may also filter received NLRI
         from bilateral peer sessions when they are tagged with this
         community value";
      reference
        "RFC3765";
        "RFC 3765: NOPEER Community for BGP.";
    }
    identity as-path-segment-type {
      description
        "Base AS Path Segment Type. In [BGP-4], the path segment type
         is a 1-octet field with the following values defined.";
      reference
        "RFC 4271: A Border Gateway Protocol 4 (BGP-4), Section 4.3.";
    }

    identity as-set {
      base as-path-segment-type;
      description
        "Unordered set of autonomous systems that a route in the UPDATE
         message has traversed.";
      reference
        "RFC 4271: A Border Gateway Protocol 4 (BGP-4), Section 4.3.";
    }

    identity as-sequence {
      base as-path-segment-type;
      description
        "Ordered set of autonomous systems that a route in the UPDATE
         message has traversed.";
      reference
        "RFC 4271: A Border Gateway Protocol 4 (BGP-4), Section 4.3.";
    }

    identity as-confed-sequence {
      base as-path-segment-type;
      description
        "Ordered set of Member Autonomous Systems in the local
         confederation that the UPDATE message has traversed.";
      reference
        "RFC 5065, Autonomous System Configuration for BGP.";
    }

    identity as-confed-set {
      base as-path-segment-type;
      description
        "Unordered set of Member Autonomous Systems in the local
         confederation that the UPDATE message has traversed.";
      reference
        "RFC 5065, Autonomous System Configuration for BGP.";
    }

    /*
     * Features.
     */
    feature send-communities {
      description
        "Enable the propogation of communities.";
    }

    feature ttl-security {
      description
        "BGP Time To Live (TTL) security check support.";
      reference
        "RFC 5082, The Generalized TTL Security Mechanism (GTSM)";
    }

    feature bfd {
      description
        "Support for BFD detection of BGP neighbor reachability.";
      reference
        "RFC 5880, Bidirectional Forward Detection (BFD),
         RFC 5881, Bidirectional Forward Detection for IPv4 and IPv6
                   (Single Hop).
         RFC 5883, Bidirectional Forwarding Detection (BFD) for Multihop
                   Paths";
    }

    typedef bgp-session-direction {
      type enumeration {
        enum INBOUND {
          description
            "Refers to all NLRI received from the BGP peer";
        }
        enum OUTBOUND {
          description
            "Refers to all NLRI advertised to the BGP peer";
        }
      }
      description
        "Type to describe the direction of NLRI transmission";
    }

    typedef bgp-well-known-community-type {
      type identityref {
        base BGP_WELL_KNOWN_STD_COMMUNITY; bgp-well-known-std-community;
      }
      description
        "Type definition for well-known IETF community attribute
         values";
      reference
        "IANA Border Gateway Protocol (BGP) Well Known Communities";
    }
    typedef bgp-std-community-type {
      // TODO: further refine restrictions and allowed patterns
      // 4-octet value:
      //  <as number> 2 octets
      //  <community value> 2 octets
      type union {
        type uint32 {
        // per RFC 1997, 0x00000000 - 0x0000FFFF and 0xFFFF0000 -
        // 0xFFFFFFFF are reserved
          range "65536..4294901759"; // 0x00010000..0xFFFEFFFF
        }
        type string {
          pattern '([0-9]+:[0-9]+)';
        }
      }
      description
        "Type definition for standard community attributes";
      reference
        "RFC 1997 - BGP Communities Attribute";
    }

    typedef bgp-ext-community-type {
      // TODO: needs more work to make this more precise given the
      // variability of extended community attribute specifications
      // 8-octet value:
      //  <type> 2 octects
      //  <value> 6 octets

      type union {
        type string {
          // Type 1: 2-octet global and 4-octet local
          //         (AS number)        (Integer)
          pattern '(6[0-5][0-5][0-3][0-5]|[1-5][0-9]{4}|'            +
                  '[1-9][0-9]{1,4}|[0-9]):'                          +
                  '(4[0-2][0-9][0-4][0-9][0-6][0-7][0-2][0-9][0-6]|' +
                  '[1-3][0-9]{9}|[1-9]([0-9]{1,7})?[0-9]|[1-9])';
        }
        type string {
          // Type 2: 4-octet global and 2-octet local
          //         (ipv4-address)     (integer)
          pattern '(([0-9]|[1-9][0-9]|1[0-9][0-9]|2[0-4][0-9]|'      +
                  '25[0-5])\.){3}([0-9]|[1-9][0-9]|1[0-9][0-9]|'     +
                  '2[0-4][0-9]|25[0-5]):'                            +
                  '(6[0-5][0-5][0-3][0-5]|[1-5][0-9]{4}|'            +
                  '[1-9][0-9]{1,4}|[0-9])';
        }
        type string {
          // route-target with Type 1
          // route-target:(ASN):(local-part)
          pattern 'route\-target:(6[0-5][0-5][0-3][0-5]|'            +
                  '[1-5][0-9]{4}|[1-9][0-9]{1,4}|[0-9]):'            +
                  '(4[0-2][0-9][0-4][0-9][0-6][0-7][0-2][0-9][0-6]|' +
                  '[1-3][0-9]{9}|[1-9]([0-9]{1,7})?[0-9]|[1-9])';
        }
        type string {
          // route-target with Type 2
          // route-target:(IPv4):(local-part)
          pattern 'route\-target:' +
                  '(([0-9]|[1-9][0-9]|1[0-9][0-9]|2[0-4][0-9]|'      +
                  '25[0-5])\.){3}([0-9]|[1-9][0-9]|1[0-9][0-9]|'     +
                  '2[0-4][0-9]|25[0-5]):'                            +
                  '(6[0-5][0-5][0-3][0-5]|[1-5][0-9]{4}|'            +
                  '[1-9][0-9]{1,4}|[0-9])';
        }
        type string {
          // route-origin with Type 1
          pattern 'route\-origin:(6[0-5][0-5][0-3][0-5]|'            +
                  '[1-5][0-9]{4}|[1-9][0-9]{1,4}|[0-9]):'            +
                  '(4[0-2][0-9][0-4][0-9][0-6][0-7][0-2][0-9][0-6]|' +
                  '[1-3][0-9]{9}|[1-9]([0-9]{1,7})?[0-9]|[1-9])';
        }
        type string {
          // route-origin with Type 2
          pattern 'route\-origin:' +
                  '(([0-9]|[1-9][0-9]|1[0-9][0-9]|2[0-4][0-9]|'      +
                  '25[0-5])\.){3}([0-9]|[1-9][0-9]|1[0-9][0-9]|'     +
                  '2[0-4][0-9]|25[0-5]):'                            +
                  '(6[0-5][0-5][0-3][0-5]|[1-5][0-9]{4}|'            +
                  '[1-9][0-9]{1,4}|[0-9])';
        }
      }
      description
        "Type definition for extended community attributes";
      reference
        "RFC 4360 - BGP Extended Communities Attribute";
    }

    typedef bgp-community-regexp-type {
      // TODO: needs more work to decide what format these regexps can
      // take.
      type string;
      description
        "Type definition for communities specified as regular
         expression patterns";
    }
    typedef bgp-origin-attr-type {
      type enumeration {
        enum IGP igp {
          description "Origin of the NLRI is internal";
        }
        enum EGP egp {
          description "Origin of the NLRI is EGP";
        }
        enum INCOMPLETE incomplete {
          description "Origin of the NLRI is neither IGP or EGP";
        }
      }
      description
        "Type definition for standard BGP origin attribute";
      reference
        "RFC 4271 - A Border Gateway Protocol 4 (BGP-4), Sec 4.3";
    }

    typedef peer-type {
      type enumeration {
        enum INTERNAL internal {
          description
            "internal (iBGP) peer";
        }
        enum EXTERNAL external {
          description
            "external (eBGP) peer";
        }
        enum confederation {
          description
          "Confederation as peer";
        }
      }
      description
        "Labels a peer or peer group as explicitly internal internal,
         external or
         external"; confederation.";
    }

    identity REMOVE_PRIVATE_AS_OPTION {
      description
        "Base identity for options for removing private autonomous
         system numbers from the AS_PATH attribute";
    }

    identity PRIVATE_AS_REMOVE_ALL {
      base REMOVE_PRIVATE_AS_OPTION;
      description
        "Strip all private autonomous system numbers from the AS_PATH.

         This action is performed regardless of the other content of the
         AS_PATH attribute, and for all instances of private AS numbers
         within that attribute.";
    }

    identity PRIVATE_AS_REPLACE_ALL {
      base REMOVE_PRIVATE_AS_OPTION;
      description
        "Replace all instances of private autonomous system numbers in
         the AS_PATH with the local BGP speaker's autonomous system
         number. This action is performed regardless of the other
         content of the AS_PATH attribute, and for all instances of
         private AS number within that attribute.";
    }

    typedef remove-private-as-option {
      type identityref {
        base REMOVE_PRIVATE_AS_OPTION;
      }
      description
        "Set of options for configuring how private AS path numbers
         are removed from advertisements";
    }

    typedef percentage {
      type uint8 {
        range "0..100";
      }
      description
        "Integer indicating a percentage value";
    }

    typedef rr-cluster-id-type {
      type union {
        type uint32;
        type inet:ipv4-address;
      }
      description
        "Union type for route reflector cluster ids:
         option 1: 4-byte number
         option 2: IP address";
    }

    typedef community-type {
      type enumeration bits {
        enum STANDARD
        bit standard {
          position 0;
          description
            "Send only standard communities"; communities.";
          reference
            "RFC 1997: BGP Communities Attribute.";
        }
        enum EXTENDED
        bit extended {
          description
            "Send only extended communities"; communities.";
          reference
            "RFC 4360: BGP Extended Communities Attribute.";
        }
        enum BOTH
        bit large {
          description
            "Send both standard and extended communities";
        }
        enum NONE {
          description
          "Do not send any community attribute"; only large communities.";
          reference
            "RFC 8092: BGP Large Communities Attribute.";
        }
      }
      description
        "Type describing variations of community attributes:
         STANDARD: standard BGP community [rfc1997]
         EXTENDED: extended BGP attributes.
         The community [rfc4360]
         BOTH: both standard types can be combined and extended community"; a value of 0
         implies 'none'";
    }
  }
  <CODE ENDS>

7.3.  BGP policy data

     <CODE BEGINS> file "ietf-bgp-policy@2019-06-13.yang" "ietf-bgp-policy@2019-10-03.yang"
 module ietf-bgp-policy {
   yang-version "1.1";
   namespace "urn:ietf:params:xml:ns:yang:ietf-bgp-policy";
   prefix "bp";

   // import some basic types
   import ietf-inet-types {
     prefix inet;
   }
   import ietf-routing-policy {
     prefix rpol;
   }
   import ietf-bgp-types {
     prefix bt;
   }

   import ietf-routing-types {
     prefix rt-types;
   }
   organization
     "IETF IDR Working Group";

   contact
     "WG Web:   <http://tools.ietf.org/wg/idr>
      WG List:  <idr@ietf.org>

      Authors: Mahesh Jethanandani (mjethanandani at gmail.com),
               Keyur Patel (keyur at arrcus.com),
               Susan Hares (shares at ndzh.com)"; ndzh.com),
               Jeffrey Haas (jhaas at pfrc.org).";

   description
     "This module contains data definitions for BGP routing policy.
      It augments the base routing-policy module with BGP-specific
      options for conditions and actions.";

   revision "2019-06-13" "2019-10-03" {
     description
       "Initial Version";
     reference
       "RFC XXX, BGP Model for Service Provider Network.";
   }

   // typedef statements

   typedef bgp-set-community-option-type {
     type enumeration {
       enum ADD add {
         description
           "Add the specified communities to the existing
            community attribute";
       }
       enum REMOVE remove {
         description
           "Remove the specified communities from the
            existing community attribute";
       }
       enum REPLACE replace {
         description
           "Replace the existing community attribute with
            the specified communities. If an empty set is
            specified, this removes the community attribute
            from the route.";
       }
     }
     description
       "Type definition for options when setting the community
        attribute in a policy action";
   }

   typedef bgp-next-hop-type {
     type union {
       type inet:ip-address-no-zone;
       type enumeration {
         enum SELF self {
           description
             "Special designation for local router's own
              address, i.e., next-hop-self";
         }
       }
     }
     description
       "Type definition for specifying next-hop in policy actions";
   }

   typedef bgp-set-med-type {
     type union {
       type uint32;
       type string {
         pattern "^[+-][0-9]+"; "^[+-]([0-9]{1,8}|[0-3][0-9]{1,9}|4[0-1][0-9]{1,8}|" +
                 "428[0-9]{1,7}|429[0-3][0-9]{1,6}|42948[0-9]{1,5}|" +
                 "42949[0-5][0-9]{1,4}|429496[0-6][0-9]{1,3}|" +
                 "4294971[0-9]{1,2}|42949728[0-9]|42949729[0-5])$";
       }
       type enumeration {
         enum IGP igp {
           description
             "Set the MED value to the IGP cost toward the
              next hop for the route";
         }
         enum med-plus-igp {
           description
             "Before comparing MED values for path selection, adds to
              the MED the cost of the IGP route to the BGP next-hop
              destination.

              This option replaces the MED value for the router,
              but does not affect the IGP metric comparison. As a
              result, when multiple routes have the same value
              after the MED-plus-IPG comparison, and route selection
              continues, the IGP route metric is also compared, even
              though it was added to the MED value and compared
              earlier in the selection process.

              Useful when the downstream AS requires the complete
              cost of a certain route that is received across
              multiple ASs.";
         }
       }
     }
     description
       "Type definition for specifying how the BGP MED can
        be set in BGP policy actions. The three choices are to set
        the MED directly, increment/decrement using +/- notation,
        and setting it to the IGP cost (predefined value).";
     reference
       "None. WG needs to decide if this is going to be a standard.";
   }

   // augment statements

   augment "/rpol:routing-policy/rpol:defined-sets" {
     description
       "Adds BGP defined sets container to routing policy model.";

     container bgp-defined-sets {
       description
         "BGP-related set definitions for policy match conditions";

       container community-sets {
         description
           "Enclosing container for list of defined BGP community sets";

         list community-set {
           key "community-set-name"; "name";
           description
             "List of defined BGP community sets";

           leaf community-set-name name {
             type string;
             mandatory true;
             description
               "Name / label of the community set -- this is used to
                reference the set in match conditions";
           }

           leaf-list community-member member {
             type union {
               type bt:bgp-std-community-type;
               type bt:bgp-community-regexp-type;
               type bt:bgp-well-known-community-type;
             }
             description
               "Members of the community set";
           }
         }
       }

       container ext-community-sets {
         description
           "Enclosing container for list of extended BGP community
            sets";
         list ext-community-set {
           key "ext-community-set-name"; "name";
           description
             "List of defined extended BGP community sets";

           leaf ext-community-set-name name {
             type string;
             description
               "Name / label of the extended community set -- this is
                used to reference the set in match conditions";
           }

           leaf-list ext-community-member member {
             type union {
               type rt-types:route-target;
               type bt:bgp-community-regexp-type;
             }
             description
               "Members of the extended community set";
           }
         }
       }

       container as-path-sets {
         description
           "Enclosing container for list of define AS path sets";

         list as-path-set {
           key "as-path-set-name"; "name";
           description
             "List of defined AS path sets";

           leaf as-path-set-name name {
             type string;
             description
               "Name of the AS path set -- this is used to reference the
                set in match conditions";
           }
           leaf-list as-path-set-member member {
             // TODO: need to refine typedef for AS path expressions
             type string;
             description
               "AS path expression -- list of ASes in the set";
           }
         }
       }
     }
   }

   grouping set-community-action-common {
     description
       "Common leaves for set-community and set-ext-community
        actions";

     leaf method {
       type enumeration {
         enum INLINE inline {
           description
             "The extended communities are specified inline as a
              list";
         }
         enum REFERENCE reference {
           description
             "The extended communities are specified by referencing a
              defined ext-community set";
         }
       }
       description
         "Indicates the method used to specify the extended
          communities for the set-ext-community action";
     }

     leaf options {
       type bgp-set-community-option-type;
       description
         "Options for modifying the community attribute with
          the specified values.  These options apply to both
          methods of setting the community attribute.";
     }
   }

   augment "/rpol:routing-policy/rpol:policy-definitions/" +
     "rpol:policy-definition/rpol:statements/rpol:statement/" +
     "rpol:conditions" {
     description
       "BGP policy conditions added to routing policy module";

     container bgp-conditions {
       description
         "Top-level container for BGP specific policy conditions ";

       leaf med-eq {
         type uint32;
         description
           "Condition to check if the received MED value is equal to
            the specified value";
       }

       leaf origin-eq {
         type bt:bgp-origin-attr-type;
         description
           "Condition to check if the route origin is equal to the
            specified value";
       }

       leaf-list next-hop-in {
         type inet:ip-address-no-zone;
         description
           "List of next hop addresses to check for in the route
            update";
       }

       leaf-list afi-safi-in {
         type identityref {
           base bt:afi-safi-type;
         }
         description
           "List of address families which the NLRI may be within";
       }

       leaf local-pref-eq {
         type uint32;
         // TODO: add support for other comparisons if needed
         description
           "Condition to check if the local pref attribute is equal to
            the specified value";
       }

       leaf route-type {
         // TODO: verify extent of vendor support for this comparison
         type enumeration {
           enum INTERNAL internal {
             description "route type is internal";
           }
           enum EXTERNAL external {
             description "route type is external";
           }
         }
         description
           "Condition to check the route type in the route update";
       }

       container community-count {
         description
           "Value and comparison operations for conditions based on the
            number of communities in the route update";
       }

       container as-path-length {
         description
           "Value and comparison operations for conditions based on the
            length of the AS path in the route update";
       }

       container match-community-set {
         description
           "Top-level container for match conditions on communities.
            Match a referenced community-set according to the logic
            defined in the match-set-options leaf";

         leaf community-set {
           type leafref {
             path
               "/rpol:routing-policy/rpol:defined-sets/" +
               "bp:bgp-defined-sets/bp:community-sets/" +
               "bp:community-set/bp:community-set-name";
               "bp:community-set/bp:name";
           }
           description
             "References a defined community set";
         }

         uses rpol:match-set-options-group;
       }

       container match-ext-community-set {
         description
           "Match a referenced extended community-set according to the
            logic defined in the match-set-options leaf";

         leaf ext-community-set {
           type leafref {
             path
               "/rpol:routing-policy/rpol:defined-sets/" +
               "bp:bgp-defined-sets/bp:ext-community-sets/" +
               "bp:ext-community-set/" +
               "bp:ext-community-set-name";
               "bp:ext-community-set/bp:name";
           }
           description "References a defined extended community set";
         }

         uses rpol:match-set-options-group;
       }

       container match-as-path-set {
         description
           "Match a referenced as-path set according to the logic
            defined in the match-set-options leaf";

         leaf as-path-set {
           type leafref {
             path "/rpol:routing-policy/rpol:defined-sets/" +
               "bp:bgp-defined-sets/bp:as-path-sets/" +
               "bp:as-path-set/bp:as-path-set-name";
               "bp:as-path-set/bp:name";
           }
           description
             "References a defined AS path set";
         }
         uses rpol:match-set-options-group;
       }
     }
   }

   augment "/rpol:routing-policy/rpol:policy-definitions/" +
     "rpol:policy-definition/rpol:statements/rpol:statement/" +
     "rpol:actions" {
     description
       "BGP policy actions added to routing policy module.";

     container bgp-actions {
       description
         "Top-level container for BGP-specific actions";

       leaf set-route-origin {
         type bt:bgp-origin-attr-type;
         description
           "Set the origin attribute to the specified value";
       }

       leaf set-local-pref {
         type uint32;
         description
           "Set the local pref attribute on the route update";

       }

       leaf set-next-hop {
         type bgp-next-hop-type;
         description
           "Set the next-hop attribute in the route update";
       }

       leaf set-med {
         type bgp-set-med-type;
         description
           "Set the med metric attribute in the route update";
       }

       container set-as-path-prepend {
         description
           "Action to prepend local AS number to the AS-path a
            specified number of times";

         leaf repeat-n {
           type uint8 {
             range 1..max;
           }
           description
             "Number of times to prepend the local AS number to the AS
              path.  The value should be between 1 and the maximum
              supported by the implementation.";
         }
       }

       container set-community {
         description
           "Action to set the community attributes of the route, along
            with options to modify how the community is modified.
            Communities may be set using an inline list OR
            reference to an existing defined set (not both).";

         uses set-community-action-common;
         container inline {
           when "../method = 'INLINE'" 'inline'" {
             description
               "Active only when the set-community method is INLINE"; inline";
           }
           description
             "Set the community values for the action inline with
              a list.";

           leaf-list communities {
             type union {
               type bt:bgp-std-community-type;
               type bt:bgp-well-known-community-type;
             }
             description
               "Set the community values for the update inline with a
                list.";
           }
         }

         container reference {
           when "../method = 'REFERENCE'" 'reference'" {
             description
               "Active only when the set-community method is REFERENCE"; reference";
           }
           description
             "Provide a reference to a defined community set for the
              set-community action";

           leaf community-set-ref {
             type leafref {
               path "/rpol:routing-policy/rpol:defined-sets/" +
                 "bp:bgp-defined-sets/" +
                 "bp:community-sets/bp:community-set/" +
                 "bp:community-set-name";
                 "bp:community-sets/bp:community-set/bp:name";
             }
             description
               "References a defined community set by name";
           }
         }
       }

       container set-ext-community {
         description
           "Action to set the extended community attributes of the
            route, along with options to modify how the community is
            modified. Extended communities may be set using an inline
            list OR a reference to an existing defined set (but not
            both).";

         uses set-community-action-common;
         container inline {
           when "../method = 'INLINE'" 'inline'" {
             description
               "Active only when the set-community method is INLINE"; inline";
           }
           description
             "Set the extended community values for the action inline
              with a list.";

           leaf-list communities {
             type union {
               type rt-types:route-target;
               type bt:bgp-well-known-community-type;
             }
             description
               "Set the extended community values for the update inline
                with a list.";
           }
         }

         container reference {
           when "../method = 'REFERENCE'" 'reference'" {
             description
               "Active only when the set-community method is REFERENCE"; reference";
           }
           description
             "Provide a reference to an extended community set for the
              set-ext-community action";

           leaf ext-community-set-ref {
             type leafref {
               path
                 "/rpol:routing-policy/rpol:defined-sets/" +
                 "bp:bgp-defined-sets/bp:ext-community-sets/" +
                 "bp:ext-community-set/" +
                 "bp:ext-community-set-name";
                 "bp:ext-community-set/bp:name";
             }
             description
               "References a defined extended community set by name";
           }
         }
       }
     }
   }

   // rpc statements

   // notification statements
 }
     <CODE ENDS>

7.4.  RIB modules

<CODE BEGINS> file "ietf-bgp-rib@2019-06-13.yang" "ietf-bgp-rib@2019-10-03.yang"
submodule ietf-bgp-rib {
  yang-version "1.1";
  belongs-to ietf-bgp {
    prefix "br";

  }

  /*
   * Import and Include
   */
  import ietf-bgp-types {
    prefix "bt";
    reference
      "RFC XXXX: BGP YANG Model for Service Provider Networks.";
  }

  import ietf-inet-types {
    prefix inet;
    reference
      "RFC 6991: Common YANG Types.";
  }

  import ietf-yang-types {
    prefix yang;
    reference
      "RFC 6991: Common YANG Types.";
  }

  import ietf-routing-types {
    prefix "rt";
    reference
      "RFC 8294: Routing Area YANG Types.";
  }

  include ietf-bgp-rib-types;
  include ietf-bgp-rib-tables;

  // groupings of attributes in three categories:
  //  - shared across multiple routes
  //  - common to LOC-RIB and Adj-RIB, but not shared across routes
  //  - specific to LOC-RIB or Adj-RIB
  include ietf-bgp-rib-attributes;

  // groupings of annotations for each route or table
  include ietf-bgp-rib-table-attributes;

  organization
    "IETF IDR Working Group";

  contact
    "WG Web:   <http://tools.ietf.org/wg/idr>
     WG List:  <idr@ietf.org>
     Authors: Mahesh Jethanandani (mjethanandani at gmail.com),
              Keyur Patel (keyur at arrcus.com),
              Susan Hares (shares at ndzh.com)";

  description
    "Defines a submodule for representing BGP routing table (RIB)
     contents.  The submodule supports 5 logical RIBs per address
     family:

     loc-rib: This is the main BGP routing table for the local routing
     instance, containing best-path selections for each prefix. The
     loc-rib table may contain multiple routes for a given prefix,
     with an attribute to indicate which was selected as the best
     path.  Note that multiple paths may be used or advertised even if
     only one path is marked as best, e.g., when using BGP
     add-paths.  An implementation may choose to mark multiple
     paths in the RIB as best path by setting the flag to true for
     multiple entries.

     adj-rib-in-pre: This is a per-neighbor table containing the NLRI
     updates received from the neighbor before any local input policy
     rules or filters have been applied.  This can be considered the
     'raw' updates from a given neighbor.

     adj-rib-in-post: This is a per-neighbor table containing the
     routes received from the neighbor that are eligible for
     best-path selection after local input policy rules have been
     applied.

     adj-rib-out-pre: This is a per-neighbor table containing routes
     eligible for sending (advertising) to the neighbor before output
     policy rules have been applied.

     adj-rib-out-post: This is a per-neighbor table containing routes
     eligible for sending (advertising) to the neighbor after output
     policy rules have been applied.";

  revision "2019-06-13" "2019-10-03" {
    description
      "Initial Version";
    reference
      "RFC XXXX, BGP YANG Model for Service Provider Network.";
  }

  grouping rib {
    description
      "Grouping for rib.";

    container rib {
      config false;

      container attr-sets {
        description
          "Enclosing container for the list of path attribute sets";

        list attr-set {
          key "index";

          description
            "List of path attributes that may be in use by multiple
             routes in the table";

          leaf index {
            type uint64;
            description
              "System generated index for each attribute set.  The
               index is used to reference an attribute set from a
               specific path.  Multiple paths may reference the same
               attribute set.";
          }

          leaf origin {
            type bt:bgp-origin-attr-type;
            description
              "BGP attribute defining the origin of the path
               information.";
          }

          leaf atomic-aggregate {
            type boolean;
            description
              "BGP attribute indicating that the prefix is an atomic
               aggregate; i.e., the peer selected a less specific
               route without selecting a more specific route that is
               included in it.";
            reference
              "RFC 4271: Section 5.1.6.";
          }

          leaf next-hop {
            type inet:ip-address;
            description
              "BGP next hop attribute defining the IP address of the
               router that should be used as the next hop to the
               destination";
            reference
              "RFC 4271: Section 5.1.3.";
          }

          leaf med {
            type uint32;
            description
              "BGP multi-exit discriminator attribute used in BGP route
               selection process";
            reference
              "RFC 4271: Section 5.1.4.";
          }

          leaf local-pref {
            type uint32;
            description
              "BGP local preference attribute sent to internal peers to
               indicate the degree of preference for externally learned
               routes.  The route with the highest local preference
               value is preferred.";
            reference
              "RFC 4271: Section 5.1.5.";
          }

          leaf originator-id {
            type yang:dotted-quad;
            description
              "BGP attribute that provides the id as an IPv4 address
               of the originator of the announcement.";
            reference
              "RFC 4456 - BGP Route Reflection: An Alternative to Full
               Mesh Internal BGP (IBGP)";
          }

          leaf-list cluster-list {
            type yang:dotted-quad;
            description
              "Represents the reflection path that the route has
               passed.";
            reference
              "RFC 4456 - BGP Route Reflection: An Alternative to Full
               Mesh Internal BGP (IBGP)";
          }

          leaf aigp-metric {
            type uint64;
            description
              "BGP path attribute representing the accumulated IGP
               metric for the path";

            reference
              "RFC 7311 - The Accumulated IGP Metric Attribute for BGP";
          }
          container aggregator {
            config false;
            description
              "BGP attribute indicating the prefix has been
               aggregated by the specified AS and router.";
            reference
              "RFC 4271: Section 5.1.7.";

            leaf as {
              type inet:as-number;
              description
                "AS number of the autonomous system that performed the
                 aggregation.";
            }

            leaf as4 {
              type inet:as-number;
              description
                "AS number of the autonomous system that performed the
                 aggregation (4-octet representation).  This value is
                 populated if an upstream router is not 4-octet capable.
                 Its semantics are similar to the AS4_PATH optional
                 transitive attribute";
              reference
                "RFC 6793 - BGP Support for Four-octet AS Number Space";
            }

            leaf address {
              type inet:ipv4-address;
              description
                "IP address of the router that performed the
                 aggregation.";
            }
          }
          container as-path {
            description
              "Enclosing container for the list of AS path segments.

               In the Adj-RIB-In or Adj-RIB-Out, this list should show
               the received or sent AS_PATH, respectively.  For
               example, if the local router is not 4-byte capable, this
               value should consist of 2-octet ASNs or the AS_TRANS
               (AS 23456) values received or sent in route updates.

               In the Loc-RIB, this list should reflect the effective
               AS path for the route, e.g., a 4-octet value if the
               local router is 4-octet capable.";
            reference
              "RFC 4271 - A Border Gateway Protocol 4 (BGP-4)
               RFC 6793 - BGP Support for Four-octet AS Number Space
               RFC 5065 - Autonomous System Confederations for BGP";

            list segment {
              key "type";

              config false;
              uses bgp-as-path-attr;
              description
                "List of AS PATH segments";
            }
          }
          container as4-path {
            description
              "This is the path encoded with 4-octet
               AS numbers in the optional transitive AS4_PATH attribute.
               This value is populated with the received or sent
               attribute in Adj-RIB-In or Adj-RIB-Out, respectively.
               It should not be populated in Loc-RIB since the Loc-RIB
               is expected to store the effective AS-Path in the
               as-path leaf regardless of being 4-octet or 2-octet.";
            reference
              "RFC 6793 - BGP Support for Four-octet AS Number Space";

            list segment {
              key "type";

              config false;
              uses bgp-as-path-attr;
              description
                "List of AS PATH segments";
            }
          }
        }
      }

      container communities {
        description
          "Enclosing container for the list of community attribute
        sets";

        list community {
          key "index";
          config false;
          description
            "List of path attributes that may be in use by multiple
          routes in the table";

          leaf index {
            type uint64;
            description
              "System generated index for each attribute set.  The
              index is used to reference an attribute set from a
              specific path.  Multiple paths may reference the same
              attribute set.";
          }

          uses bgp-community-attr-state;
        }
      }

      container ext-communities {
        description
          "Enclosing container for the list of extended community
           attribute sets";

        list ext-community {
          key "index";

          config false;
          description
            "List of path attributes that may be in use by multiple
             routes in the table";

          leaf index {
            type uint64;
            description
              "System generated index for each attribute set.  The
               index is used to reference an attribute set from a
               specific path.  Multiple paths may reference the same
               attribute set.";
          }

          leaf-list ext-community {
            type rt:route-target;
            description
              "List of BGP extended community attributes. The received
               extended community may be an explicitly modeled
               type or unknown, represented by an 8-octet value
               formatted according to RFC 4360.";
            reference
              "RFC 4360 - BGP Extended Communities Attribute";
          }
        }
      }

      container afi-safis {
        config false;
        description
          "Enclosing container for address family list";

        list afi-safi {
          key "afi-safi-name";
          description
            "List of afi-safi types.";

          leaf afi-safi-name {
            type identityref {
              base bt:afi-safi-type;
            }
            description "AFI,SAFI name.";
          }

          container ipv4-unicast {
            when "../afi-safi-name = 'bt:ipv4-unicast'" {
              description
                "Include this container for IPv4 unicast RIB";
            }
            description
              "Routing tables for IPv4 unicast -- active when the
              afi-safi name is ipv4-unicast";

            uses ipv4-loc-rib;
            uses ipv4-adj-rib;
          }

          container ipv6-unicast {
            when "../afi-safi-name = 'bt:ipv6-unicast'" {
              description
                "Include this container for IPv6 unicast RIB";
            }
            description
              "Routing tables for IPv6 unicast -- active when the
               afi-safi name is ipv6-unicast";

            uses ipv6-loc-rib;
            uses ipv6-adj-rib;
          }
        }

      }
      description
        "Top level container for BGP RIB";
    }
  }
}
<CODE ENDS>

   <CODE BEGINS> file "ietf-bgp-rib-ext@2019-06-13.yang" "ietf-bgp-rib-ext@2019-10-03.yang"
   submodule ietf-bgp-rib-ext {
     yang-version "1.1";
     belongs-to ietf-bgp {
       prefix "bre";
     }

     include ietf-bgp-rib-types;

     organization
       "IETF IDR Working Group";

     contact
       "WG Web:   <http://tools.ietf.org/wg/idr>
        WG List:  <idr@ietf.org>

        Authors: Mahesh Jethanandani (mjethanandani at gmail.com),
                 Keyur Patel (keyur at arrcus.com),
                 Susan Hares (shares at ndzh.com)"; ndzh.com),
                 Jeffrey Haas (jhaas at pfrc.org).";

     description
       "Defines additional data nodes for the OpenConfig BGP RIB model.
        These items reflect extensions that are desirable features but
        are not currently supported in a majority of BGP
        implementations.";

     revision "2019-06-13" "2019-10-03" {
       description
         "Initial Revision.";
       reference
         "RFC XXXX: BGP YANG Model for Service Providers.";
     }

     grouping rib-ext-route-annotations {
       description
         "Extended annotations for routes in the routing tables";

       leaf reject-reason {
         type union {
           type identityref {
             base bgp-not-selected-bestpath;
           }
           type identityref {
             base bgp-not-selected-policy;
           }
         }
         description
           "Indicates the reason the route is not used, either due to
            policy filtering or bestpath selection";
       }
     }
   }
   <CODE ENDS>

   <CODE BEGINS> file "ietf-bgp-rib-types@2019-06-13.yang" "ietf-bgp-rib-types@2019-10-03.yang"
   submodule ietf-bgp-rib-types {
     yang-version "1.1";
     belongs-to ietf-bgp {
       prefix "br";
     }

     organization
       "IETF IDR Working Group";

     contact
       "WG Web:   <http://tools.ietf.org/wg/idr>
        WG List:  <idr@ietf.org>

        Authors: Mahesh Jethanandani (mjethanandani at gmail.com),
                 Keyur Patel (keyur at arrcus.com),
                 Susan Hares (shares at ndzh.com)"; ndzh.com),
                 Jeffrey Haas (jhaas at pfrc.org).";

     description
       "Defines identity and type definitions associated with
        the BGP RIB modules";

     revision "2019-06-13" "2019-10-03" {
       description
         "Initial Version";
       reference
         "RFC XXXX, BGP Model for Service Provider Network.";
     }

     identity invalid-route-reason {
       description
         "Base identity for reason code for routes that are rejected as
          invalid.  Some derived entities are based on BMP v3";
       reference
         "BGP
         "RFC 7854: BGP Monitoring Protocol (draft-ietf-grow-bmp-07)"; Protocol.";
     }

     identity invalid-cluster-loop {
       base invalid-route-reason;
       description
         "Route was invalid due to CLUSTER_LIST loop";
     }

     identity invalid-as-loop {
       base invalid-route-reason;
       description
         "Route was invalid due to AS_PATH loop";
     }

     identity invalid-originator {
       base invalid-route-reason;
       description
         "Route was invalid due to ORIGINATOR_ID, e.g., update has
          local router as originator";
     }

     identity invalid-confed {
       base invalid-route-reason;
       description
         "Route was invalid due to a loop in the AS_CONFED_SEQUENCE or
          AS_CONFED_SET attributes";
     }

     identity bgp-not-selected-bestpath {
       description
         "Base identity for indicating reason a route was was not
          selected by BGP route selection algorithm";
       reference
         "RFC 4271 - Section 9.1";
     }

     identity local-pref-lower {
       base bgp-not-selected-bestpath;
       description
         "Route has a lower localpref attribute than current best path";
       reference
         "RFC 4271 - Section 9.1.2";
     }
     identity as-path-longer {
       base bgp-not-selected-bestpath;
       description
         "Route has a longer AS path attribute than current best path";
       reference
         "RFC 4271 - Section 9.1.2.2 (a)";
     }

     identity origin-type-higher {
       base bgp-not-selected-bestpath;
       description
         "Route has a higher origin type, i.e., IGP origin is preferred
          over EGP or incomplete";
       reference
         "RFC 4271 - Section 9.1.2.2 (b)";
     }

     identity med-higher {
       base bgp-not-selected-bestpath;
       description
         "Route has a higher MED, or metric, attribute than the current
          best path";
       reference
         "RFC 4271 - Section 9.1.2.2 (c)";
     }

     identity prefer-external {
       base bgp-not-selected-bestpath;
       description
         "Route source is via IGP, rather than EGP.";
       reference
         "RFC 4271 - Section 9.1.2.2 (d)";
     }

     identity nexthop-cost-higher {
       base bgp-not-selected-bestpath;
       description
         "Route has a higher interior cost to the next hop.";
       reference
         "RFC 4271 - Section 9.1.2.2 (e)";
     }

     identity higher-router-id {
       base bgp-not-selected-bestpath;
       description
         "Route was sent by a peer with a higher BGP Identifier value,
          or router id";
       reference
         "RFC 4271 - Section 9.1.2.2 (f)";
     }

     identity higher-peer-address {
       base bgp-not-selected-bestpath;
       description
         "Route was sent by a peer with a higher IP address";
       reference
         "RFC 4271 - Section 9.1.2.2 (g)";
     }

     identity bgp-not-selected-policy {
       description
         "Base identity for reason code for routes that are rejected
          due to policy";
     }

     identity rejected-import-policy {
       base bgp-not-selected-policy;
       description
         "Route was rejected after apply import policies";
     }
   }
   <CODE ENDS>

<CODE BEGINS> file "ietf-bgp-rib-attributes@2019-06-13.yang" "ietf-bgp-rib-attributes@2019-10-03.yang"
submodule ietf-bgp-rib-attributes {
  yang-version "1.1";
  belongs-to ietf-bgp {
    prefix "br";
  }

  // import some basic types
  import ietf-bgp-types {
    prefix bgpt;
  }

  import ietf-inet-types {
    prefix inet;
  }

  include ietf-bgp-rib-types;

  // meta
  organization
    "IETF IDR Working Group";

  contact
    "WG Web:   <http://tools.ietf.org/wg/idr>
     WG List:  <idr@ietf.org>

     Authors: Mahesh Jethanandani (mjethanandani at gmail.com),
              Keyur Patel (keyur at arrcus.com),
              Susan Hares (shares at ndzh.com)";

  description
    "This submodule contains common data definitions for BGP
     attributes for use in BGP RIB tables.";

  revision "2019-06-13" "2019-10-03" {
    description
      "Initial version";
    reference
      "RFC XXXX: BGP YANG Model for Service Provider Network";
  }

  grouping bgp-as-path-attr {
    description
      "Data for representing BGP AS-PATH attribute";

    leaf type {
      type identityref {
        base bgpt:as-path-segment-type;
      }
      description
        "The type of AS-PATH segment";
    }

    leaf-list member {
      type inet:as-number;
      description
        "List of the AS numbers in the AS-PATH segment";
    }
  }

  grouping bgp-community-attr-state {
    description
      "Common definition of BGP community attributes";

    leaf-list community {
      type union {
        type bgpt:bgp-well-known-community-type;
        type bgpt:bgp-std-community-type;
      }
      description
        "List of standard or well-known BGP community
         attributes.";
    }
  }

  grouping bgp-unknown-attr-flags-state {
    description
      "Operational state data for path attribute flags";

    leaf optional {
      type boolean;
      description
        "Defines whether the attribute is optional (if
         set to true) or well-known (if set to false).
         Set in the high-order bit of the BGP attribute
         flags octet.";
      reference
        "RFC 4271 - A Border Gateway Protocol 4 (BGP-4)";
    }

    leaf transitive {
      type boolean;
      description
        "Defines whether an optional attribute is transitive
         (if set to true) or non-transitive (if set to false).  For
         well-known attributes, the transitive flag must be set to
         true.  Set in the second high-order bit of the BGP attribute
         flags octet.";
      reference
        "RFC 4271 - A Border Gateway Protocol 4 (BGP-4)";
    }

    leaf partial {
      type boolean;
      description
        "Defines whether the information contained in the optional
         transitive attribute is partial (if set to true) or complete
         (if set to false).  For well-known attributes and for
         optional non-transitive attributes, the partial flag
         must be set to false.  Set in the third high-order bit of
         the BGP attribute flags octet.";
      reference
        "RFC 4271 - A Border Gateway Protocol 4 (BGP-4)";
    }

    leaf extended {
      type boolean;
      description
        "Defines whether the attribute length is one octet
         (if set to false) or two octets (if set to true).  Set in
         the fourth high-order bit of the BGP attribute flags
         octet.";
      reference
        "RFC 4271 - A Border Gateway Protocol 4 (BGP-4)";
    }
  }

  grouping bgp-unknown-attr-state {
    description
      "Operational state data for path attributes not shared
       across route entries, common to LOC-RIB and Adj-RIB";

    leaf attr-type {
      type uint8;
      description
        "1-octet value encoding the attribute type code";
      reference
        "RFC 4271 - A Border Gateway Protocol 4 (BGP-4)";
    }

    leaf attr-len {
      type uint16;
      description
        "One or two octet attribute length field indicating the
         length of the attribute data in octets.  If the Extended
         Length attribute flag is set, the length field is 2 octets,
         otherwise it is 1 octet";
      reference
        "RFC 4271 - A Border Gateway Protocol 4 (BGP-4)";
    }

    leaf attr-value {
      type binary {
        length 0..65535;
      }
      description
        "Raw attribute value, not including the attribute
         flags, type, or length.  The maximum length
         of the attribute value data is 2^16-1 per the max value
         of the attr-len field (2 octets).";
      reference
        "RFC 4271 - A Border Gateway Protocol 4 (BGP-4)";
    }
  }
  grouping bgp-unknown-attr-top {
    description
      "Unknown path attributes that are not expected to be shared
       across route entries, common to LOC-RIB and Adj-RIB";

    container unknown-attributes {
      description
        "Unknown path attributes that were received in the UPDATE
         message which contained the prefix.";

      list unknown-attribute {
        key "attr-type";
        description
          "This list contains received attributes that are unrecognized
           or unsupported by the local router.  The list may be empty.";

        uses bgp-unknown-attr-flags-state;
        uses bgp-unknown-attr-state;
      }
    }
  }

  grouping bgp-loc-rib-attr-state {
    description
      "Path attributes that are not expected to be shared across
       route entries, specific to LOC-RIB";

  }

  grouping bgp-adj-rib-attr-state {
    description
      "Path attributes that are not expected to be shared across
       route entries, specific to Adj-RIB";

    leaf path-id {
      type uint32;
      description
        "When the BGP speaker supports advertisement of multiple
         paths for a prefix, the path identifier is used to
         uniquely identify a route based on the combination of the
         prefix and path id.  In the Adj-RIB-In, the path-id value is
         the value received in the update message.   In the Loc-RIB,
         if used, it should represent a locally generated path-id
         value for the corresponding route.  In Adj-RIB-Out, it
         should be the value sent to a neighbor when add-paths is
         used, i.e., the capability has been negotiated.";
      reference
        "RFC 7911: Advertisement of Multiple Paths in BGP";

    }
  }
}
<CODE ENDS>

   <CODE BEGINS> file "ietf-bgp-rib-table-attributes@2019-06-13.yang" "ietf-bgp-rib-table-attributes@2019-10-03.yang"
   submodule ietf-bgp-rib-table-attributes {
     yang-version "1.1";
     belongs-to ietf-bgp {
       prefix "br";
     }

     // import some basic types
     import ietf-yang-types {
       prefix types;
       reference
         "RFC 6991, Common YANG Data Types.";
     }

     include ietf-bgp-rib-types;

     organization
       "IETF IDR Working Group";

     contact
       "WG Web:   <http://tools.ietf.org/wg/idr>
        WG List:  <idr@ietf.org>

        Authors: Mahesh Jethanandani (mjethanandani at gmail.com),
                 Keyur Patel (keyur at arrcus.com),
                 Susan Hares (shares at ndzh.com";

     description
       "This submodule contains common data definitions for data
        related to a RIB entry, or RIB table.";

     revision "2019-06-13" "2019-10-03" {
       description
         "Initial version.";
       reference
         "RFC XXXX: BGP YANG Model for Service Provider Network.";
     }

     grouping bgp-common-route-annotations-state {
       description
         "Data definitions for flags and other information attached
          to routes in both LOC-RIB and Adj-RIB";

       leaf last-modified {
         type types:timeticks;
         description
           "Timestamp when this path was last modified.

            The value is the timestamp in seconds relative to
            the Unix Epoch (Jan 1, 1970 00:00:00 UTC).";
       }

       leaf valid-route {
         type boolean;
         description
           "Indicates that the route is considered valid by the
            local router";
       }

       leaf invalid-reason {
         type identityref {
           base invalid-route-reason;
         }
         description
           "If the route is rejected as invalid, this indicates the
            reason.";
       }
     }

     grouping bgp-loc-rib-route-annotations-state {
       description
         "Data definitions for information attached to routes in the
          LOC-RIB";

          // placeholder for route metadata specific to the LOC-RIB
     }

     grouping bgp-adj-rib-in-post-route-annotations-state {
       description
         "Data definitions for information attached to routes in the
          Adj-RIB-in post-policy table";

       leaf best-path {
         type boolean;
         description
           "Current path was selected as the best path.";
       }
     }
     grouping bgp-common-table-attrs-state {
       description
         "Common attributes attached to all routing tables";

         // placeholder for metadata associated with all tables
     }

     grouping bgp-common-table-attrs-top {
       // no enclosing container as this data will fit under an
       // existing LOC-RIB container

       uses bgp-common-table-attrs-state;
       description
         "Operational state data for data related to the entire
          LOC-RIB";
     }
   }
   <CODE ENDS>

   <CODE BEGINS> file "ietf-bgp-rib-tables@2019-06-13.yang" "ietf-bgp-rib-tables@2019-10-03.yang"
   submodule ietf-bgp-rib-tables {
     yang-version "1.1";
     belongs-to ietf-bgp {
       prefix "br";
     }

     // import some basic types
     import ietf-inet-types {
       prefix inet;
       reference
         "RFC 6991: Common YANG Data Types.";
     }

     import ietf-yang-types {
       prefix yang;
       reference
         "RFC 6991: Common YANG Data Types.";
     }

     import ietf-routing {
       prefix "rt";
       reference
         "RFC 8022: A YANG Data Model for Routing Management";
     }

     include ietf-bgp-rib-ext;
     include ietf-bgp-rib-attributes;
     include ietf-bgp-rib-table-attributes;

     organization
       "IETF IDR Working Group";

     contact
       "WG Web:   <http://tools.ietf.org/wg/idr>
        WG List:  <idr@ietf.org>

        Editor:  Mahesh Jethanandani (mjethanandani@gmail.com)
        Authors: Keyur Patel,
                 Mahesh Jethanandani,
                 Susan Hares";

     description
       "This submodule contains structural data definitions for
        BGP routing tables.";

     revision "2019-06-13" "2019-10-03" {
       description
         "Initial Version";
       reference
         "RFC XXXX, BGP YANG Model for Service Provider Network.";
     }

     /*
      * Feature(s)
      */
     feature clear-routes {
       description
         "Clearing of BGP routes is supported.";
     }

     grouping bgp-adj-rib-common-attr-refs {
       description
         "Definitions of common references to attribute sets for
          multiple AFI-SAFIs for Adj-RIB tables";

       leaf attr-index {
         type leafref {
           path "../../../../../../../../../attr-sets/" +
                "attr-set/index";
         }
         description
           "Reference to the common attribute group for the
            route";
       }
       leaf community-index {
         type leafref {
           path "../../../../../../../../../communities/community/" +
             "index";
         }
         description
           "Reference to the community attribute for the route";
       }

       leaf ext-community-index {
         type leafref {
           path "../../../../../../../../../ext-communities/" +
                "ext-community/index";
         }
         description
           "Reference to the extended community attribute for the
            route";
       }
     }

     grouping bgp-loc-rib-common-attr-refs {
       description
         "Definitions of common references to attribute sets for
          multiple AFI-SAFIs for LOC-RIB tables";

       leaf attr-index {
         type leafref {
           path "../../../../../../../attr-sets/attr-set/" +
                "index";
         }
         description
           "Reference to the common attribute group for the
            route";
       }

       leaf community-index {
         type leafref {
           path "../../../../../../../communities/community/" +
                "index";
         }
         description
           "Reference to the community attribute for the route";
       }

       leaf ext-community-index {
         type leafref {
           path "../../../../../../../ext-communities/" +
                "ext-community/index";

         }
         description
           "Reference to the extended community attribute for the
            route";
       }
     }

     grouping bgp-loc-rib-common-keys {
       description
         "Common references used in keys for IPv4 and IPv6
          LOC-RIB entries";

       leaf origin {
         type union {
           type inet:ip-address;
           type identityref {
             base rt:routing-protocol;
           }
         }
         description
           "Indicates the origin of the route.  If the route is learned
            from a neighbor, this value is the neighbor address.  If
            the route was injected or redistributed from another
            protocol, the origin indicates the source protocol for the
            route.";
       }

       leaf path-id {
         type uint32;
         // TODO: YANG does not allow default values for key
         // default 0;
         description
           "If the route is learned from a neighbor, the path-id
            corresponds to the path-id for the route in the
            corresponding adj-rib-in-post table.  If the route is
            injected from another protocol, or the neighbor does not
            support BGP add-paths, the path-id should be set
            to zero, also the default value.";
       }
     }

     grouping clear-routes {
       description
         "Action to clear BGP routes.";

       container clear-routes {
         if-feature "clear-routes";
         action clear {
           input {
             leaf clear-at {
               type yang:date-and-time;
               description
                 "The time, in the future when the clear operation will
                  be initiated.";
             }
           }

           output {
             leaf clear-finished-at {
               type yang:date-and-time;
               description
                 "The time when the clear operation finished.";
             }
           }
         }
         description
           "Action commands to clear routes governed by a if-feature.";
       }
     }

     grouping ipv4-loc-rib {
       description
         "Top-level grouping for IPv4 routing tables";

       container loc-rib {
         config false;
         description
           "Container for the IPv4 BGP LOC-RIB data";

         uses bgp-common-table-attrs-top;

         container routes {
           description
             "Enclosing container for list of routes in the routing
              table.";

           list route {
             key "prefix origin path-id";

             description
               "List of routes in the table, keyed by the route
                prefix, the route origin, and path-id.  The route
                origin can be either the neighbor address from which
                the route was learned, or the source protocol that
                injected the route.  The path-id distinguishes routes
                for the same prefix received from a neighbor (e.g.,
                if add-paths is eanbled)."; enabled).";

             leaf prefix {
               type inet:ipv4-prefix;
               description
                 "The IPv4 prefix corresponding to the route";
             }

             uses bgp-loc-rib-common-keys;
             uses bgp-loc-rib-common-attr-refs;
             uses bgp-loc-rib-attr-state;
             uses bgp-common-route-annotations-state;
             uses bgp-loc-rib-route-annotations-state;
             uses bgp-unknown-attr-top;
             uses rib-ext-route-annotations;
           }

           uses clear-routes;
         }
       }
     }

     grouping ipv6-loc-rib {
       description
         "Top-level grouping for IPv6 routing tables";

       container loc-rib {
         config false;
         description
           "Container for the IPv6 BGP LOC-RIB data";

         uses bgp-common-table-attrs-top;

         container routes {
           description
             "Enclosing container for list of routes in the routing
              table.";

           list route {
             key "prefix origin path-id";

             description
               "List of routes in the table, keyed by the route
                prefix, the route origin, and path-id.  The route
                origin can be either the neighbor address from which
                the route was learned, or the source protocol that
                injected the route.  The path-id distinguishes routes
                for the same prefix received from a neighbor (e.g.,
                if add-paths is eanbled)."; enabled).";

             leaf prefix {
               type inet:ipv6-prefix;
               description
                 "The IPv6 prefix corresponding to the route";
             }

             uses bgp-loc-rib-common-keys;
             uses bgp-loc-rib-common-attr-refs;
             uses bgp-loc-rib-attr-state;
             uses bgp-common-route-annotations-state;
             uses bgp-loc-rib-route-annotations-state;
             uses bgp-unknown-attr-top;
             uses rib-ext-route-annotations;
           }

           uses clear-routes;
         }
       }
     }

     grouping ipv4-adj-rib-common {
       description
         "Common structural grouping for each IPv4 adj-RIB table";

       uses bgp-common-table-attrs-top;

       container routes {
         config false;
         description
           "Enclosing container for list of routes in the routing
            table.";

         list route {
           key "prefix path-id";

           description
             "List of routes in the table, keyed by a combination of
              the route prefix and path-id to distinguish multiple
              routes received from a neighbor for the same prefix,
              e.g., when BGP add-paths is enabled.";

           leaf prefix {
             type inet:ipv4-prefix;
             description
               "Prefix for the route";

           }

           uses bgp-adj-rib-attr-state;
           uses bgp-adj-rib-common-attr-refs;
           uses bgp-common-route-annotations-state;
           uses bgp-unknown-attr-top;
           uses rib-ext-route-annotations;
         }

         uses clear-routes;
       }
     }

     grouping ipv4-adj-rib-in-post {
       description
         "Common structural grouping for the IPv4 adj-rib-in
          post-policy table";

       uses bgp-common-table-attrs-top;

       container routes {
         config false;
         description
           "Enclosing container for list of routes in the routing
            table.";

         list route {
           key "prefix path-id";

           description
             "List of routes in the table, keyed by a combination of
              the route prefix and path-id to distinguish multiple
              routes received from a neighbor for the same prefix,
              e.g., when BGP add-paths is enabled.";

           leaf prefix {
             type inet:ipv4-prefix;
             description
               "Prefix for the route";
           }

           uses bgp-adj-rib-attr-state;
           uses bgp-adj-rib-common-attr-refs;
           uses bgp-common-route-annotations-state;
           uses bgp-adj-rib-in-post-route-annotations-state;
           uses bgp-unknown-attr-top;
           uses rib-ext-route-annotations;
         }

       }
     }

     grouping ipv4-adj-rib {
       description
         "Top-level grouping for Adj-RIB table";

       container neighbors {
         config false;
         description
           "Enclosing container for neighbor list";

         list neighbor {
           key "neighbor-address";
           description
             "List of neighbors (peers) of the local BGP speaker";

           leaf neighbor-address {
             type inet:ip-address;
             description
               "IP address of the BGP neighbor or peer";
           }

           container adj-rib-in-pre {
             description
               "Per-neighbor table containing the NLRI updates
                received from the neighbor before any local input
                policy rules or filters have been applied.  This can
                be considered the 'raw' updates from the neighbor.";

             uses ipv4-adj-rib-common;

           }

           container adj-rib-in-post {
             description
               "Per-neighbor table containing the paths received from
                the neighbor that are eligible for best-path selection
                after local input policy rules have been applied.";

             uses ipv4-adj-rib-in-post;
           }

           container adj-rib-out-pre {
             description
               "Per-neighbor table containing paths eligble for
                sending (advertising) to the neighbor before output
                policy rules have been applied";

             uses ipv4-adj-rib-common;

           }

           container adj-rib-out-post {
             description
               "Per-neighbor table containing paths eligble for
                sending (advertising) to the neighbor after output
                policy rules have been applied";

             uses ipv4-adj-rib-common;
           }
         }
       }
     }

     grouping ipv6-adj-rib-common {
       description
         "Common structural grouping for each IPv6 adj-RIB table";

       uses bgp-common-table-attrs-state;

       container routes {
         config false;
         description
           "Enclosing container for list of routes in the routing
            table.";

         list route {
           key "prefix path-id";

           description
             "List of routes in the table";

           leaf prefix {
             type inet:ipv6-prefix;
             description
               "Prefix for the route";
           }

           uses bgp-adj-rib-attr-state;
           uses bgp-adj-rib-common-attr-refs;
           uses bgp-common-route-annotations-state;
           uses bgp-unknown-attr-top;
           uses rib-ext-route-annotations;
         }
         uses clear-routes;
       }
     }

     grouping ipv6-adj-rib-in-post {
       description
         "Common structural grouping for the IPv6 adj-rib-in
          post-policy table";

       uses bgp-common-table-attrs-state;

       container routes {
         config false;
         description
           "Enclosing container for list of routes in the routing
            table.";

         list route {
           key "prefix path-id";

           description
             "List of routes in the table";

           leaf prefix {
             type inet:ipv6-prefix;
             description
               "Prefix for the route";
           }

           uses bgp-adj-rib-attr-state;
           uses bgp-adj-rib-common-attr-refs;
           uses bgp-common-route-annotations-state;
           uses bgp-adj-rib-in-post-route-annotations-state;
           uses bgp-unknown-attr-top;
           uses rib-ext-route-annotations;
         }
       }
     }

     grouping ipv6-adj-rib {
       description
         "Top-level grouping for Adj-RIB table";

       container neighbors {
         config false;
         description
           "Enclosing container for neighbor list";

         list neighbor {
           key "neighbor-address";
           description
             "List of neighbors (peers) of the local BGP speaker";

           leaf neighbor-address {
             type inet:ip-address;
             description
               "IP address of the BGP neighbor or peer";
           }

           container adj-rib-in-pre {
             description
               "Per-neighbor table containing the NLRI updates
                received from the neighbor before any local input
                policy rules or filters have been applied.  This can
                be considered the 'raw' updates from the neighbor.";

             uses ipv6-adj-rib-common;

           }

           container adj-rib-in-post {
             description
               "Per-neighbor table containing the paths received from
                the neighbor that are eligible for best-path selection
                after local input policy rules have been applied.";

             uses ipv6-adj-rib-in-post;
           }

           container adj-rib-out-pre {
             description
               "Per-neighbor table containing paths eligble for
                sending (advertising) to the neighbor before output
                policy rules have been applied";

             uses ipv6-adj-rib-common;

           }

           container adj-rib-out-post {
             description
               "Per-neighbor table containing paths eligble for
                sending (advertising) to the neighbor after output
                policy rules have been applied";

             uses ipv6-adj-rib-common;

           }
         }
       }
     }
   }
   <CODE ENDS>

   <CODE BEGINS> file "ietf-bgp-rib-table-attributes@2019-06-13.yang" "ietf-bgp-rib-table-attributes@2019-10-03.yang"
   submodule ietf-bgp-rib-table-attributes {
     yang-version "1.1";
     belongs-to ietf-bgp {
       prefix "br";
     }

     // import some basic types
     import ietf-yang-types {
       prefix types;
       reference
         "RFC 6991, Common YANG Data Types.";
     }

     include ietf-bgp-rib-types;

     organization
       "IETF IDR Working Group";

     contact
       "WG Web:   <http://tools.ietf.org/wg/idr>
        WG List:  <idr@ietf.org>

        Authors: Mahesh Jethanandani (mjethanandani at gmail.com),
                 Keyur Patel (keyur at arrcus.com),
                 Susan Hares (shares at ndzh.com";

     description
       "This submodule contains common data definitions for data
        related to a RIB entry, or RIB table.";

     revision "2019-06-13" "2019-10-03" {
       description
         "Initial version.";
       reference
         "RFC XXXX: BGP YANG Model for Service Provider Network.";
     }

     grouping bgp-common-route-annotations-state {
       description
         "Data definitions for flags and other information attached
          to routes in both LOC-RIB and Adj-RIB";

       leaf last-modified {
         type types:timeticks;
         description
           "Timestamp when this path was last modified.

            The value is the timestamp in seconds relative to
            the Unix Epoch (Jan 1, 1970 00:00:00 UTC).";
       }

       leaf valid-route {
         type boolean;
         description
           "Indicates that the route is considered valid by the
            local router";
       }

       leaf invalid-reason {
         type identityref {
           base invalid-route-reason;
         }
         description
           "If the route is rejected as invalid, this indicates the
            reason.";
       }
     }

     grouping bgp-loc-rib-route-annotations-state {
       description
         "Data definitions for information attached to routes in the
          LOC-RIB";

          // placeholder for route metadata specific to the LOC-RIB
     }

     grouping bgp-adj-rib-in-post-route-annotations-state {
       description
         "Data definitions for information attached to routes in the
          Adj-RIB-in post-policy table";

       leaf best-path {
         type boolean;
         description
           "Current path was selected as the best path.";
       }

     }

     grouping bgp-common-table-attrs-state {
       description
         "Common attributes attached to all routing tables";

         // placeholder for metadata associated with all tables
     }

     grouping bgp-common-table-attrs-top {
       // no enclosing container as this data will fit under an
       // existing LOC-RIB container

       uses bgp-common-table-attrs-state;
       description
         "Operational state data for data related to the entire
          LOC-RIB";
     }
   }
   <CODE ENDS>

8.  Examples

   This section tries to show some examples in how the model can be
   used.

8.1.  Creating BGP Instance

   This example shows how to enable BGP with the IPv4 unicast address
   family, while adding one network to advertise.

[note: '\' line wrapping for formatting only]

<?xml version="1.0" encoding="UTF-8"?>
<config xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
  <routing
      xmlns="urn:ietf:params:xml:ns:yang:ietf-routing">
    <control-plane-protocols>
      <control-plane-protocol>
        <type
            xmlns:bgpm="urn:ietf:params:xml:ns:yang:ietf-bgp">bgpm:bgp
        </type>
        <name>BGP</name>
        <bgp
            xmlns="urn:ietf:params:xml:ns:yang:ietf-bgp">
          <global>
            <as>64496</as>
            <afi-safis>
              <afi-safi>
                <afi-safi-name
                    xmlns:bt="urn:ietf:params:xml:ns:yang:ietf-bgp-types">bt:ipv4-\
unicast
                </afi-safi-name>
              </afi-safi>
            </afi-safis>
          </global>
        </bgp>
      </control-plane-protocol>
    </control-plane-protocols>
  </routing>
</config>

8.2.  Neighbor Address Family Configuration

   This example shows how to configure a BGP peer, where the remote
   address is 192.0.2.1, the remote AS number is 64497, and the address
   family of the peer is IPv4 unicast.

[note: '\' line wrapping for formatting only]

<!--
  This example shows a neighbor configuration with damping.
-->

<?xml version="1.0" encoding="UTF-8"?>
<config xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
  <routing
      xmlns="urn:ietf:params:xml:ns:yang:ietf-routing">

    <control-plane-protocols>
      <control-plane-protocol>
        <type
            xmlns:bgp="urn:ietf:params:xml:ns:yang:ietf-bgp">bgp:bgp
        </type>
        <name>name:BGP</name>
        <bgp
            xmlns="urn:ietf:params:xml:ns:yang:ietf-bgp">
          <global>
            <as>64496</as>
            <afi-safis>
              <afi-safi>
                <afi-safi-name
                    xmlns:bt="urn:ietf:params:xml:ns:yang:ietf-bgp-types">bt:ipv4-\
unicast
                </afi-safi-name>
              </afi-safi>
            </afi-safis>
          </global>
          <neighbors>
            <neighbor>
              <remote-address>192.0.2.1</remote-address>
              <peer-as>64497</peer-as>
              <route-flap-damping>
                <enable>true</enable>
                <suppress-above>4.0</suppress-above>
                <reuse-above>3.0</reuse-above>
                <max-flap>15.0</max-flap>
                <reach-decay>100</reach-decay>
                <unreach-decay>500</unreach-decay>
                <keep-history>1000</keep-history>
              </route-flap-damping>
              <description>"Peer Router B"</description>
              <afi-safis>
                <afi-safi>
                  <afi-safi-name
                      xmlns:bt="urn:ietf:params:xml:ns:yang:ietf-bgp-types">bt:ipv\
4-unicast
                  </afi-safi-name>
                </afi-safi>
              </afi-safis>
            </neighbor>
          </neighbors>
        </bgp>
      </control-plane-protocol>
    </control-plane-protocols>
  </routing>
</config>
9.  Contributors

   Previous versions of this document saw contributions from Anees
   Shaikh, Rob Shakir, Kevin D'Souza, Alexander Clemm, Aleksandr
   Zhadkin, and Xyfeng Liu.

10.  Acknowledgements

   The authors are grateful for valuable contributions to this document
   and
8.3.  IPv6 Neighbor Configuration

   This example shows how to configure a BGP peer, where the remote peer
   has a IPv6 address, and uses non-default timers for hold-time and
   keepalive.

[note: '\' line wrapping for formatting only]

<?xml version="1.0" encoding="UTF-8"?>
<config xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
  <routing
      xmlns="urn:ietf:params:xml:ns:yang:ietf-routing">
    <control-plane-protocols>
      <control-plane-protocol>
        <type
            xmlns:bgp="urn:ietf:params:xml:ns:yang:ietf-bgp">bgp:bgp
        </type>
        <name>name:BGP</name>
        <bgp
            xmlns="urn:ietf:params:xml:ns:yang:ietf-bgp">
          <global>
            <as>64496</as>
            <afi-safis>
              <afi-safi>
                <afi-safi-name
                    xmlns:bt="urn:ietf:params:xml:ns:yang:ietf-bgp-types">bt:ipv6-\
unicast
                </afi-safi-name>
              </afi-safi>
            </afi-safis>
          </global>
          <neighbors>
            <neighbor>
              <remote-address>2001:db8::</remote-address>
              <enabled>true</enabled>
              <peer-as>64497</peer-as>
              <description>"Peer Router B"</description>
              <timers>
                <hold-time>120</hold-time>
                <keepalive>70</keepalive>
              </timers>
              <afi-safis>
                <afi-safi>
                  <afi-safi-name
                      xmlns:bt="urn:ietf:params:xml:ns:yang:ietf-bgp-types">bt:ipv\
6-unicast
                  </afi-safi-name>
                </afi-safi>

              </afi-safis>
            </neighbor>
          </neighbors>
        </bgp>
      </control-plane-protocol>
    </control-plane-protocols>
  </routing>
</config>

8.4.  VRF Configuration

   This example shows how BGP can be configured for two VRFs, red and
   blue.  In this case, the two network instances share a common AS, and
   distinguish between the instances using the router id.

[note: '\' line wrapping for formatting only]

<?xml version="1.0" encoding="UTF-8"?>
<config xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
  <network-instances
      xmlns="urn:ietf:params:xml:ns:yang:ietf-network-instance">
    <network-instance>
      <name>vrf-red</name>
      <vrf-root>
        <routing
            xmlns="urn:ietf:params:xml:ns:yang:ietf-routing">
          <router-id>192.0.2.1</router-id>
          <control-plane-protocols>
            <control-plane-protocol>
              <type
                  xmlns:bgpm="urn:ietf:params:xml:ns:yang:ietf-bgp">bgpm:bgp
              </type>
              <name>BGP</name>
              <bgp
                  xmlns="urn:ietf:params:xml:ns:yang:ietf-bgp">
                <global>
                  <as>64496</as>
                  <afi-safis>
                    <afi-safi>
                      <afi-safi-name
                          xmlns:bt="urn:ietf:params:xml:ns:yang:ietf-bgp-types">bt:ipv4-u\
nicast
                      </afi-safi-name>
                    </afi-safi>
                  </afi-safis>
                </global>
              </bgp>

            </control-plane-protocol>
          </control-plane-protocols>
        </routing>
      </vrf-root>
    </network-instance>
    <network-instance>
      <name>vrf-blue</name>
      <vrf-root>
        <routing
            xmlns="urn:ietf:params:xml:ns:yang:ietf-routing">
          <router-id>192.0.2.2</router-id>
          <control-plane-protocols>
            <control-plane-protocol>
              <type
                  xmlns:bgpm="urn:ietf:params:xml:ns:yang:ietf-bgp">bgpm:bgp
              </type>
              <name>BGP</name>
              <bgp
                  xmlns="urn:ietf:params:xml:ns:yang:ietf-bgp">
                <global>
                  <as>64496</as>
                  <afi-safis>
                    <afi-safi>
                      <afi-safi-name
                          xmlns:bt="urn:ietf:params:xml:ns:yang:ietf-bgp-types">bt:ipv4-u\
nicast
                      </afi-safi-name>
                    </afi-safi>
                  </afi-safis>
                </global>
              </bgp>
            </control-plane-protocol>
          </control-plane-protocols>
        </routing>
      </vrf-root>
    </network-instance>
  </network-instances>
</config>

9.  Contributors

   Previous versions of this document saw contributions from Anees
   Shaikh, Rob Shakir, Kevin D'Souza, Alexander Clemm, Aleksandr
   Zhadkin, and Xyfeng Liu.

10.  Acknowledgements

   The authors are grateful for valuable contributions to this document
   and the associated models from: Ebben Aires, Pavan Beeram, Chris
   Chase, Ed Crabbe, Luyuan Fang, Bill Fenner, Akshay Gattani, Josh
   George, Vijay Gill, Matt John, Jeff Haas, Dhanendra Jain, Acee
   Lindem, Ina Minei, Carl Moberg, Ashok Narayanan, Einar Nilsen-
   Nygaard, Adam Simpson, Puneet Sood, Jason Sterne, Jeff Tantsura, Jim
   Uttaro, and Gunter Vandevelde.

   Credit is also due to authors of the OpenConfig, whose model was
   relied upon to come up with this model.

   Special thanks to Robert Wilton who helped convert the YANG models to
   a NMDA compatible model.

11.  References

11.1.  Normative references

   [RFC1997]  Chandra, R., Traina, P., and T. Li, "BGP Communities
              Attribute", RFC 1997, DOI 10.17487/RFC1997, August 1996,
              <https://www.rfc-editor.org/info/rfc1997>.

   [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>.

   [RFC2439]  Villamizar, C., Chandra, R., and R. Govindan, "BGP Route
              Flap Damping", RFC 2439, DOI 10.17487/RFC2439, November
              1998, <https://www.rfc-editor.org/info/rfc2439>.

   [RFC3688]  Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688,
              DOI 10.17487/RFC3688, January 2004,
              <https://www.rfc-editor.org/info/rfc3688>.

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

   [RFC4456]  Bates, T., Chen, E., and R. Chandra, "BGP Route
              Reflection: An Alternative to Full Mesh Internal BGP
              (IBGP)", RFC 4456, DOI 10.17487/RFC4456, April 2006,
              <https://www.rfc-editor.org/info/rfc4456>.

   [RFC4724]  Sangli, S., Chen, E., Fernando, R., Scudder, J., and Y.
              Rekhter, "Graceful Restart Mechanism for BGP", RFC 4724,
              DOI 10.17487/RFC4724, January 2007,
              <https://www.rfc-editor.org/info/rfc4724>.

   [RFC4760]  Bates, T., Chandra, R., Katz, D., and Y. Rekhter,
              "Multiprotocol Extensions for BGP-4", RFC 4760,
              DOI 10.17487/RFC4760, January 2007,
              <https://www.rfc-editor.org/info/rfc4760>.

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

   [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>.

   [RFC6242]  Wasserman, M., "Using the NETCONF Protocol over Secure
              Shell (SSH)", RFC 6242, DOI 10.17487/RFC6242, June 2011,
              <https://www.rfc-editor.org/info/rfc6242>.

   [RFC6811]  Mohapatra, P., Scudder, J., Ward, D., Bush, R., and R.
              Austein, "BGP Prefix Origin Validation", RFC 6811,
              DOI 10.17487/RFC6811, January 2013,
              <https://www.rfc-editor.org/info/rfc6811>.

   [RFC6991]  Schoenwaelder, J., Ed., "Common YANG Data Types",
              RFC 6991, DOI 10.17487/RFC6991, July 2013,
              <https://www.rfc-editor.org/info/rfc6991>.

   [RFC7950]  Bjorklund, M., Ed., "The YANG 1.1 Data Modeling Language",
              RFC 7950, DOI 10.17487/RFC7950, August 2016,
              <https://www.rfc-editor.org/info/rfc7950>.

   [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>.

   [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>.

   [RFC8341]  Bierman, A. and M. Bjorklund, "Network Configuration
              Access Control Model", STD 91, RFC 8341,
              DOI 10.17487/RFC8341, March 2018,
              <https://www.rfc-editor.org/info/rfc8341>.

   [RFC8349]  Lhotka, L., Lindem, A., and Y. Qu, "A YANG Data Model for
              Routing Management (NMDA Version)", RFC 8349,
              DOI 10.17487/RFC8349, March 2018,
              <https://www.rfc-editor.org/info/rfc8349>.

   [RFC8446]  Rescorla, E., "The Transport Layer Security (TLS) Protocol
              Version 1.3", RFC 8446, DOI 10.17487/RFC8446, August 2018,
              <https://www.rfc-editor.org/info/rfc8446>.

   [RFC8528]  Bjorklund, M. and L. Lhotka, "YANG Schema Mount",
              RFC 8528, DOI 10.17487/RFC8528, March 2019,
              <https://www.rfc-editor.org/info/rfc8528>.

   [RFC8529]  Berger, L., Hopps, C., Lindem, A., Bogdanovic, D., and X.
              Liu, "YANG Data Model for Network Instances", RFC 8529,
              DOI 10.17487/RFC8529, March 2019,
              <https://www.rfc-editor.org/info/rfc8529>.

11.2.  Informative references

   [I-D.ietf-bfd-yang]
              Rahman, R., Zheng, L., Jethanandani, M., Networks, J., and
              G. Mirsky, "YANG Data Model for Bidirectional Forwarding
              Detection (BFD)", draft-ietf-bfd-yang-17 (work in
              progress), August 2018.

   [I-D.ietf-rtgwg-policy-model]
              Qu, Y., Tantsura, J., Lindem, A., and X. Liu, "A YANG Data
              Model for Routing Policy Management", draft-ietf-rtgwg-
              policy-model-06
              policy-model-07 (work in progress), March September 2019.

   [RFC5082]  Gill, V., Heasley, J., Meyer, D., Savola, P., Ed., and C.
              Pignataro, "The Generalized TTL Security Mechanism
              (GTSM)", RFC 5082, DOI 10.17487/RFC5082, October 2007,
              <https://www.rfc-editor.org/info/rfc5082>.

   [RFC5880]  Katz, D. and D. Ward, "Bidirectional Forwarding Detection
              (BFD)", RFC 5880, DOI 10.17487/RFC5880, June 2010,
              <https://www.rfc-editor.org/info/rfc5880>.

   [RFC7854]  Scudder,

   [RFC5925]  Touch, J., Ed., Fernando, R., Mankin, A., and S. Stuart, "BGP
              Monitoring Protocol (BMP)", R. Bonica, "The TCP
              Authentication Option", RFC 5925, DOI 10.17487/RFC5925,
              June 2010, <https://www.rfc-editor.org/info/rfc5925>.

   [RFC7454]  Durand, J., Pepelnjak, I., and G. Doering, "BGP Operations
              and Security", BCP 194, RFC 7454, DOI 10.17487/RFC7454,
              February 2015, <https://www.rfc-editor.org/info/rfc7454>.

   [RFC7854]  Scudder, J., Ed., Fernando, R., and S. Stuart, "BGP
              Monitoring Protocol (BMP)", RFC 7854,
              DOI 10.17487/RFC7854, June 2016,
              <https://www.rfc-editor.org/info/rfc7854>.

   [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>.

Appendix A.  How to add a new AFI and Augment a Module

   This section explains how a new AFI can be defined in a new module
   and how that module can then be augmented.  Assume that the new AFI
   being defined is called 'foo' which extends the base identity of
   'afi-safi-type', and the augmentation is to add a new container for
   'foo' under two different XPaths.  The example shows how the base
   identity can be extended to add this new AFI, and then use the
   augmented containers be used to add 'foo' specific information.

   module example-newafi-bgp {
     yang-version 1.1;
     namespace "http://example.com/ns/example-newafi-bgp";
     prefix example-newafi-bgp;

     import ietf-routing {
       prefix rt;
       reference
         "RFC 8349, A YANG Data Model for Routing Management
          (NMDA Version)";
     }

     import ietf-bgp {
       prefix "bgp";
       reference
         "RFC XXXX: BGP YANG module for Service Provider Network.";
     }

     import ietf-bgp-types {
       prefix "bt";

     }

     organization
       "Newafi model group.";

     contact
       "abc@newafi.com";
     description
       "This YANG module defines and uses new AFI.";

     revision 2019-10-03 {
       description
         "Creating new AFI and using in this model";

       reference
         "RFC XXXX: BGP YANG Model for Service Provider Network.";
     }

     identity foo {
       base bt:afi-safi-type;
       description
         "New AFI type foo.";
     }

     augment "/rt:routing/rt:control-plane-protocols/" +
             "rt:control-plane-protocol/bgp:bgp/bgp:global/" +
             "bgp:afi-safis/bgp:afi-safi" {
       when "derived-from-or-self(bgp:afi-safi-name, 'foo')" {
         description
           "This augmentation is valid for a AFI/SAFI instance
            of 'foo'";
       }
       container foo {
         description
           "Container to add 'foo' specific AFI/SAFI information.";
       }
     }

     augment "/rt:routing/rt:control-plane-protocols/" +
             "rt:control-plane-protocol/bgp:bgp/" +
             "bgp:rib/bgp:afi-safis/bgp:afi-safi" {
       when "derived-from-or-self(bgp:afi-safi-name, 'foo')" {
         description
           "This augmentation is valid for a AFI/SAFI instance
            of 'foo'";
       }
       container foo {
         description
           "Container to add 'foo' rib specific information.";
       }
     }
   }

Appendix B.  How to deviate a module

   This example shows how the BGP can be deviated to indicate two nodes
   that the particular implementation is choosing not to support.

   module example-newco-bgp {
     yang-version 1.1;
     namespace "http://example.com/ns/example-newco-bgp";
     prefix example-newco-bgp;

     import ietf-bgp {
       prefix "bgp";
     }

     organization
       "Newco model group.";

     contact
       "abc@newco.com";
     description
       "This YANG module deviates IETF BGP YANG module.";

     revision 2019-10-03 {
       description
         "Creating NewCo deviations to ietf-bgp model";

       reference
         "RFC XXXX: BGP YANG module for Service Provider Network.";
     }

     deviation "/bgp:bgp/bgp:global/bgp:graceful-restart/" +
               "bgp:restart-time" {
       deviate not-supported;
     }

     deviation "/bgp:bgp/bgp:global/bgp:graceful-restart/" +
               "bgp:stale-route-time" {
       deviate not-supported;
     }
   }

Authors' Addresses

   Mahesh Jethanandani
   VMware

   Email: mjethanandani@gmail.com

   Keyur Patel
   Arrcus
   CA
   USA

   Email: keyur@arrcus.com

   Susan Hares
   Huawei
   7453 Hickory Hill
   Saline, MI  48176
   USA

   Email: shares@ndzh.com

   Jeffrey Haas
   Juniper Networks

   Email: jhaas@pfrc.org