Interdomain Routing K. Patel
Internet-Draft Arrcus
Intended status: Standards Track M. Jethanandani
Expires: November 11, 2018
S. Hares
Huawei
May 10, 2018

BGP Model for Service Provider Networks
draft-ietf-idr-bgp-model-03

Abstract

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

Status of This Memo

This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79.

Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet-Drafts is at https://datatracker.ietf.org/drafts/current/.

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This Internet-Draft will expire on November 11, 2018.

Copyright Notice

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

This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (https://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License.


Table of Contents

1. Introduction

This document describes a YANG data model for the BGP protocol, including various protocol extensions, policy configuration, as well as defining key operational state data. 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.

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, BGP Communities Attribute, BGP Route Reflection, Multiprotocol Extensions for BGP-4, Autonomous System Confederations for BGP, BGP Route Flap Damping, Graceful Restart Mechanism for BGP, and BGP Prefix Origin Validation.

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. The model supports the NMDA architecture.

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

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.

2. Model overview

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

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.

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.

              +--rw bgp!
                 +--rw global
                 |  +-- (global-configuration-options)
                 +--rw neighbors
                 |  +--rw neighbor* [neighbor-address]
                 |  +-- (neighbor-configuration-options)
                 +--rw peer-groups
                    +--rw peer-group* [peer-group-name]
                    +-- (neighbor-configuration-options)
            

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    -> ../config/afi-safi-name
                   |
                   +--rw ipv4-unicast
                   |     ...
                   +--rw ipv6-unicast
                   |     ...
                   +--rw ipv4-labelled-unicast
                   |     ...
                   +--rw ipv6-labelled-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 references the generic YANG routing policy model described in A YANG Data Model for Routing Policy Management, 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:

           +--rw bgp
              +--rw global
              |  +--rw afi-safi
              |  |  +--rw afi-safi* [afi-safi-name]
              |  |     +--rw apply-policy
              |  +--rw apply-policy
              +--rw neighbors
              |  +--rw neighbor* [neighbor-address]
              |     +--rw afi-safi
              |     |  +--rw afi-safi* [afi-safi-name]
              |     |     +--rw apply-policy
              |     +--rw apply-policy
              +--rw peer-groups
                 +--rw peer-group* [peer-group-name]
                    +--rw afi-safi
                    |  +--rw afi-safi* [afi-safi-name]
                    |     +--rw apply-policy
                    +--rw apply-policy
            

3. Relation to other YANG data models

The BGP model is intended to work within a larger framework model, such as the Network Instance model YANG Model for Network Instance which provides a comprehensive model for defining VRFs, associated routing protocols, multiple protocol instances, and inter-protocol and inter-instance routing policies. The current version of the model imports and instantiates the BGP model in its tree at /network-instances/network-instance/vrf-root/rt:routing/control-plane-protocols/control-plane-protocol/bgp/...

It is also possible to integrate the BGP model with the Routing Management model A YANG Data Model for Routing Management which defines the notion of routing instances, or VRFs.

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 or RESTCONF. The lowest NETCONF layer is the secure transport layer, and the mandatory-to-implement secure transport is Secure Shell (SSH). The lowest RESTCONF layer is HTTPS, and the mandatory-to-implement secure transport is TLS. The NETCONF Access Control Model (NACM) 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:

5. IANA Considerations

This document registers three URIs and three YANG modules.

5.1. URI Registration

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

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

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.

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: bgp-pol
reference: RFC XXXX

name: ietf-bgp-types
namespace: urn:ietf:params:xml:ns:yang:ietf-bgp-types
prefix: bgp-types
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:

Additional modules include:

7. BGP main module and submodule for base items

<CODE BEGINS> file "ietf-bgp@2018-05-09.yang"
module ietf-bgp {
  yang-version "1.1";
  namespace "urn:ietf:params:xml:ns:yang:ietf-bgp";
  prefix "bgp";

  import ietf-routing-policy { 
    prefix rpol;
    reference
      "RFC ZZZZ: A YANG Data Model for Routing Policy Management";
  }

  include ietf-bgp-common;
  include ietf-bgp-common-multiprotocol;
  include ietf-bgp-common-structure;
  include ietf-bgp-neighbor;
  include ietf-bgp-global;
  include ietf-bgp-peer-group;

  organization
    "IETF IDR Working Group";

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

     Authors: Keyur Patel (keyur at arrcus.com),
              Mahesh Jethanandani (mjethanandani at gmail.com),
              Susan Hares (shares at ndzh.com";
     
  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 "2018-05-09" {
    description
      "Initial Version";
    reference 
      "RFC XXXX, BGP Model for Service Provider Network ";
  }

  /*
   * Groupings
   */
  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";
      uses bgp-global-base;
      uses rpol:apply-policy-group;
    }

    container neighbors {
      description
        "Configuration for BGP neighbors";
      uses bgp-neighbor-list;
    }

    container peer-groups {
      description
        "Configuration for BGP peer-groups";
      uses bgp-peer-group-list;
    }
  }
}
<CODE ENDS>
 
        
<CODE BEGINS> file "ietf-bgp-common@2018-05-09.yang"
submodule ietf-bgp-common {
  yang-version "1.1";
  belongs-to ietf-bgp {
    prefix "bgp";
  }

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

  organization
    "IETF IDR Working Group";

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

     Authors: Keyur Patel,
              Mahesh Jethanandani,
              Susan Hares";

  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 "2018-05-09" {
    description
      "Initial Version";
    reference 
      "RFC XXX, BGP Model for Service Provider Network.";
  }

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

    leaf connect-retry {
      type decimal64 {
        fraction-digits 2;
      }
      default 30;
      description
        "Time interval in seconds between attempts to establish a
         session with the peer.";
    }

    leaf hold-time {
      type decimal64 {
        fraction-digits 2;
      }
      default 90;
      description
        "Time interval in seconds that a BGP session will be
         considered active in the absence of keepalive or other
         messages from the peer.  The hold-time is typically set to
         3x the keepalive-interval.";
      reference
        "RFC 4271 - A Border Gateway Protocol 4, Sec. 10";
    }

    leaf keepalive-interval {
      type decimal64 {
        fraction-digits 2;
      }
      default 30;
      description
        "Time interval in seconds between transmission of keepalive
         messages to the neighbor.  Typically set to 1/3 the
         hold-time.";
    }

    leaf minimum-advertisement-interval {
      type decimal64 {
        fraction-digits 2;
      }
      default 30;
      description
        "Minimum time which must elapse between subsequent UPDATE
         messages relating to a common set of NLRI being transmitted
         to a peer. This timer is referred to as
         MinRouteAdvertisementIntervalTimer by RFC 4721 and serves to
         reduce the number of UPDATE messages transmitted when a
         particular set of NLRI exhibit instability.";
      reference
        "RFC 4271 - A Border Gateway Protocol 4, Sec 9.2.1.1";
    }
  }

  grouping bgp-common-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 bgp-types: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 bgp-types: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";
    }

    leaf route-flap-damping {
      type boolean;
      default false;
      description
        "Enable route flap damping.";
    }

    leaf send-community {
      type bgp-types:community-type;
      default "NONE";
      description
        "Specify which types of community should be sent to the
         neighbor or group. The default is to not send the community
         attribute";
    }

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

  grouping bgp-common-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 string;
      }
      //TODO:  the string should be converted to a leafref type
      //to point to an interface when YANG 1.1 is available with
      //leafrefs in union types.
      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 bgp-common-neighbor-group-error-handling-config {
    description
      "Configuration parameters relating to enhanced error handling
       behaviours for BGP";

    leaf treat-as-withdraw {
      type boolean;
      default "false";
      description
        "Specify whether erroneous UPDATE messages for which the NLRI
         can be extracted are reated as though the NLRI is withdrawn
         - avoiding session reset";
      reference "draft-ietf-idr-error-handling-16";
    }
  }

  grouping bgp-common-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.";
    }

    leaf stale-routes-time {
      type decimal64 {
        fraction-digits 2;
      }
      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";
    }

    leaf helper-only {
      type boolean;
      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.";
    }
  }

  grouping bgp-common-use-multiple-paths-config {
    description
      "Generic configuration options relating to use of multiple
       paths for a referenced AFI-SAFI, group or neighbor";

    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 bgp-common-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 bgp-common-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 bgp-common-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 bgp-common-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 always-compare-med {
        type boolean;
        default "false";
        description
          "Compare multi-exit discriminator (MED) value from
           different ASes when selecting the best route.  The default
           behavior is to only compare MEDs for paths received from
           the same AS.";
      }

      leaf ignore-as-path-length {
        type 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.";
      }

      leaf enable-aigp {
        type boolean;
        default false;
        description
          "Flag to enable sending / receiving accumulated IGP
           attribute in routing updates";
      }
      
      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";
      }
    }
  }

  grouping bgp-common-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@2018-05-09.yang"
submodule ietf-bgp-common-multiprotocol {
  yang-version "1.1";
  belongs-to ietf-bgp {
    prefix "bgp";
  }

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

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

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

  revision "2018-05-09" {
    description
      "Initial Version";
    reference 
      "RFC XXX, BGP Model for Service Provider Network.";
  }

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

    leaf afi-safi-name {
      type identityref {
        base bgp-types: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 bgp-common-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;

    uses bgp-common-mp-ipv4-unicast-group;
    uses bgp-common-mp-ipv6-unicast-group;
    uses bgp-common-mp-ipv4-labeled-unicast-group;
    uses bgp-common-mp-ipv6-labeled-unicast-group;
    uses bgp-common-mp-l3vpn-ipv4-unicast-group;
    uses bgp-common-mp-l3vpn-ipv6-unicast-group;
    uses bgp-common-mp-l3vpn-ipv4-multicast-group;
    uses bgp-common-mp-l3vpn-ipv6-multicast-group;
    uses bgp-common-mp-l2vpn-vpls-group;
    uses bgp-common-mp-l2vpn-evpn-group;
  }

  // Groupings relating to each address family
  grouping bgp-common-mp-ipv4-unicast-group {
    description
      "Group for IPv4 Unicast configuration options";

    container ipv4-unicast {
      when "../afi-safi-name = 'bgp-types:IPV4_UNICAST'" {
        description
          "Include this container for IPv4 Unicast specific
          configuration";
      }

      description "IPv4 unicast configuration options";

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

      // placeholder for IPv4 unicast  specific configuration
    }
  }

  grouping bgp-common-mp-ipv6-unicast-group {
    description
      "Group for IPv6 Unicast configuration options";

    container ipv6-unicast {
      when "../afi-safi-name = 'bgp-types:IPV6_UNICAST'" {
        description
          "Include this container for IPv6 Unicast specific
          configuration";
      }

      description "IPv6 unicast configuration options";

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

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

  grouping bgp-common-mp-ipv4-labeled-unicast-group {
    description
      "Group for IPv4 Labeled Unicast configuration options";

    container ipv4-labeled-unicast {
      when "../afi-safi-name = 'bgp-types:IPV4_LABELED_UNICAST'" {
        description
          "Include this container for IPv4 Labeled Unicast specific
          configuration";
      }

      description "IPv4 Labeled Unicast configuration options";

      uses bgp-common-mp-all-afi-safi-common;

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

  grouping bgp-common-mp-ipv6-labeled-unicast-group {
    description
      "Group for IPv6 Labeled Unicast configuration options";

    container ipv6-labeled-unicast {
      when "../afi-safi-name = 'bgp-types:IPV6_LABELED_UNICAST'" {
        description
          "Include this container for IPv6 Labeled Unicast specific
          configuration";
      }

      description "IPv6 Labeled Unicast configuration options";

      uses bgp-common-mp-all-afi-safi-common;

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

  grouping bgp-common-mp-l3vpn-ipv4-unicast-group {
    description
      "Group for IPv4 Unicast L3VPN configuration options";

    container l3vpn-ipv4-unicast {
      when "../afi-safi-name = 'bgp-types: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 bgp-common-mp-l3vpn-ipv4-ipv6-unicast-common;

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

  grouping bgp-common-mp-l3vpn-ipv6-unicast-group {
    description
      "Group for IPv6 Unicast L3VPN configuration options";

    container l3vpn-ipv6-unicast {
      when "../afi-safi-name = 'bgp-types: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 bgp-common-mp-l3vpn-ipv4-ipv6-unicast-common;

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

  grouping bgp-common-mp-l3vpn-ipv4-multicast-group {
    description
      "Group for IPv4 L3VPN multicast configuration options";

    container l3vpn-ipv4-multicast {
      when "../afi-safi-name = 'bgp-types: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 bgp-common-mp-l3vpn-ipv4-ipv6-multicast-common;

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

  grouping bgp-common-mp-l3vpn-ipv6-multicast-group {
    description
      "Group for IPv6 L3VPN multicast configuration options";

    container l3vpn-ipv6-multicast {
      when "../afi-safi-name = 'bgp-types: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 bgp-common-mp-l3vpn-ipv4-ipv6-multicast-common;

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

  grouping bgp-common-mp-l2vpn-vpls-group {
    description
      "Group for BGP-signalled VPLS configuration options";

    container l2vpn-vpls {
      when "../afi-safi-name = 'bgp-types:L2VPN_VPLS'" {
        description
          "Include this container for BGP-signalled VPLS specific
          configuration";
      }

      description "BGP-signalled VPLS configuration options";

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

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

  grouping bgp-common-mp-l2vpn-evpn-group {
    description
      "Group for BGP EVPN configuration options";

    container l2vpn-evpn {
      when "../afi-safi-name = 'bgp-types:L2VPN_EVPN'" {
        description
          "Include this container for BGP EVPN specific
          configuration";
      }

      description "BGP EVPN configuration options";

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

      // placeholder for BGP EVPN specific configuration options
    }
  }

  // Common groupings across multiple AFI,SAFIs
  grouping bgp-common-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 bgp-types: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;
        }
        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 bgp-common-mp-ipv4-ipv6-unicast-common {
    description
      "Common configuration that is applicable for IPv4 and IPv6
      unicast";

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

  grouping bgp-common-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 bgp-common-mp-all-afi-safi-common;
  }

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

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

  // Config groupings for common groups
  grouping bgp-common-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@2018-05-09.yang"
submodule ietf-bgp-common-structure {
  yang-version "1.1";
  belongs-to ietf-bgp {
    prefix "bgp";
  }

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

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

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


  revision "2018-05-09" {
    description
      "Initial Version";
    reference 
      "RFC XXX, BGP Model for Service Provider Network.";
  }

  grouping bgp-common-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.";
      }
    }
  }
  grouping bgp-common-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 bgp-common-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";

      leaf route-reflector-cluster-id {
        type bgp-types:rr-cluster-id-type;
        description
          "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.";
      }

      leaf route-reflector-client {
        type boolean;
        default "false";
        description
          "Configure the neighbor as a route reflector client.";
      }
    }
  }

  grouping bgp-common-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 bgp-common-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)";

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

      leaf send-max {
        type uint8;
        description
          "The maximum number of paths to advertise 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@2018-05-09.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>

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

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

  revision "2018-05-09" {
    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 bgp-common-mp-afi-safi-config;

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

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

      uses bgp-common-route-selection-options;
      uses bgp-common-global-group-use-multiple-paths;
      uses bgp-common-mp-all-afi-safi-list-contents;
    }
  }

  grouping bgp-peer-group-base {
    description
      "Parameters related to a BGP group";

    uses bgp-peer-group-config;
    uses bgp-common-neighbor-group-config;
    uses bgp-common-state;

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

      uses bgp-common-neighbor-group-timers-config;
    }

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

      uses bgp-common-neighbor-group-transport-config;
    }

    container error-handling {
      description
        "Error handling parameters used for the BGP peer-group";

      uses bgp-common-neighbor-group-error-handling-config;
    }

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

      uses bgp-common-graceful-restart-config;
    }

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

    container afi-safis {
      description
        "Per-address-family configuration parameters associated with
        thegroup";
      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@2018-05-09.yang"
submodule ietf-bgp-neighbor {
  yang-version "1.1";
  belongs-to ietf-bgp {
    prefix "bgp";
  }

  import ietf-routing-policy { 
    prefix rpol; 
  }
  import ietf-bgp-types { 
    prefix bgp-types; 
  }
  import ietf-inet-types { 
    prefix inet; 
  }
  import ietf-yang-types { 
    prefix yang; 
  }

  // 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>

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

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

  revision "2018-05-09" {
    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 bgp-common-use-multiple-paths-config;

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

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

    leaf UPDATE {
      type uint64;
      description
        "Number of BGP UPDATE messages announcing, withdrawing or
         modifying paths exchanged.";
    }

    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 neighbour or
         group";

      uses bgp-common-mp-afi-safi-config;

      leaf active {
        type boolean;
        config false;
        description
          "This value indicates whether a particular AFI-SAFI has
           been succesfully 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 {
        description
          "Parameters relating to BGP graceful-restart";

        uses bgp-common-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 bgp-common-mp-all-afi-safi-list-contents;
      uses bgp-neighbor-use-multiple-paths;
    }
  }

  grouping bgp-neighbor-base {
    description
      "Parameters related to a BGP neighbor";

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

    leaf neighbor-address {
      type inet:ip-address;
      description
        "Address of the BGP peer, either in IPv4 or IPv6";
    }

    leaf enabled {
      type boolean;
      default true;
      description
        "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.";
    }

    uses bgp-common-neighbor-group-config;

    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";
          }
        }
      config false;
      description
        "Operational state of the BGP peer";
    }

    leaf last-established {
      // Was oc-types:timeticks64
      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 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-list supported-capabilities {
      type identityref {
        base bgp-types:BGP_CAPABILITY;
      }
      config false;
      description
        "BGP capabilities negotiated as supported with the peer";
    }

    container messages {
      config false;
      description
        "Counters for BGP messages sent and received from the
         neighbor";
      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 timers {
      description
        "Timers related to a BGP neighbor";

      uses bgp-common-neighbor-group-timers-config;

      leaf negotiated-hold-time {
        type decimal64 {
          fraction-digits 2;
        }
        config false;
        description
          "The negotiated hold-time for the BGP session";
      }
    }

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

      uses bgp-common-neighbor-group-transport-config;

      leaf local-port {
        type inet:port-number;
        config false;
        description
          "Local TCP port being used for the TCP session supporting
           the BGP session";
      }

      leaf remote-address {
        type inet:ip-address;
        config false;
        description
          "Remote address to which the BGP session has been
           established";
      }

      leaf remote-port {
        type inet:port-number;
        config false;
        description
          "Remote port being used by the peer for the TCP session
           supporting the BGP session";
      }
    }

    container error-handling {
      description
        "Error handling parameters used for the BGP neighbor or
         group";
      uses bgp-common-neighbor-group-error-handling-config;

      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 {
      description
        "Parameters relating the graceful restart mechanism for BGP";

      uses bgp-common-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 {
            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 {
            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 {
            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 bgp-common-structure-neighbor-group-logging-options;
    uses bgp-common-structure-neighbor-group-ebgp-multihop;
    uses bgp-common-structure-neighbor-group-route-reflector;
    uses bgp-common-structure-neighbor-group-as-path-options;
    uses bgp-common-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;
    }
  }

  grouping bgp-neighbor-list {
    description
      "The list of BGP neighbors";

    list neighbor {
      key "neighbor-address";
      description
        "List of BGP neighbors configured on the local system,
        uniquely identified by peer IPv[46] address";

      uses bgp-neighbor-base;
    }
  }
}
<CODE ENDS>
 
        
<CODE BEGINS> file "ietf-bgp-global@2018-05-09.yang"
submodule ietf-bgp-global {
  yang-version "1.1";
  belongs-to ietf-bgp {
    prefix bgp;
  }

  import ietf-inet-types { 
    prefix inet; 
  }
  import ietf-yang-types { 
    prefix yang; 
  }

  include ietf-bgp-common;
  include ietf-bgp-common-multiprotocol;
  
  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 sub-module contains groupings that are specific to the
     global context of the BGP module";

  revision "2018-05-09" {
    description
      "Initial Version";
    reference 
      "RFC XXX, BGP Model for Service Provider Network.";
  }

  grouping bgp-global-config {
    description
      "Global configuration options 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 router-id {
      type yang:dotted-quad;
      description
        "Router id of the router - an unsigned 32-bit integer
        expressed in dotted quad notation.";
      reference
        "RFC4271 - A Border Gateway Protocol 4 (BGP-4),
        Section 4.2";
    }
  }

  grouping bgp-global-state {
    description
      "Operational state parameters for the BGP neighbor";

    uses bgp-common-state;
  }

  grouping bgp-global-default-route-distance-config {
    description
      "Configuration options relating to the administrative distance
      (or preference) assigned to routes received from different
      sources (external, internal, and local).";

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

  grouping bgp-global-confederation-config {
    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.";
    }
  }

  grouping bgp-global-afi-safi-list {
    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 bgp-common-mp-afi-safi-config;
      uses bgp-common-state;

      container graceful-restart {
        description
          "Parameters relating to BGP graceful-restart";
  
        uses bgp-common-mp-afi-safi-graceful-restart-config;
      }

      uses bgp-common-route-selection-options;
      uses bgp-common-global-group-use-multiple-paths;
      uses bgp-common-mp-all-afi-safi-list-contents;
    }
  }

  // Structural groupings
  grouping bgp-global-base {
    description
      "Global configuration parameters for the BGP router";

    uses bgp-global-config;
    uses bgp-global-state;

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

      uses bgp-global-default-route-distance-config;
    }

    container confederation {
      description
        "Parameters indicating whether the local system acts as part
        of a BGP confederation";

      uses bgp-global-confederation-config;
    }

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

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

    container afi-safis {
      description
        "Address family specific configuration";
      uses bgp-global-afi-safi-list;
    }
  }

}
<CODE ENDS>
 
        

8. BGP types

<CODE BEGINS> file "ietf-bgp-types@2018-05-09.yang"
module ietf-bgp-types {
  yang-version "1.1";
  namespace "urn:ietf:params:xml:ns:yang:ietf-bgp-types";

  prefix "bgp-types";

  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>

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

  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 "2018-05-09" {
    description
      "Initial Version";
    reference 
      "RFC XXX, BGP Model for Service Provider Network.";
  }

  identity BGP_CAPABILITY {
    description "Base identity for a BGP capability";
  }

  identity MPBGP {
    base BGP_CAPABILITY;
    description
      "Multi-protocol extensions to BGP";
    reference "RFC2858";
  }

  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 "draft-ietf-idr-add-paths";
  }

  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 {
    description
      "Reserved communities within the standard community space
      defined by RFC1997. These communities must fall within the
      range 0x00000000 to 0xFFFFFFFF";
    reference "RFC1997";
  }

  identity NO_EXPORT {
    base 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";
  }

  identity NO_ADVERTISE {
    base 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";
  }

  identity NO_EXPORT_SUBCONFED {
    base 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";
  }

  identity NOPEER {
    base 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";
  }

  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;
    }
    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 oc-types:std-regexp;
    type string;
    description
      "Type definition for communities specified as regular
      expression patterns";
  }

  typedef bgp-origin-attr-type {
    type enumeration {
      enum IGP {
        description "Origin of the NLRI is internal";
      }
      enum EGP {
        description "Origin of the NLRI is EGP";
      }
      enum 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 {
        description "internal (iBGP) peer";
      }
      enum EXTERNAL {
        description "external (eBGP) peer";
      }
    }
    description
      "labels a peer or peer group as explicitly internal or
      external";
  }

  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 autonmous 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 {
      enum STANDARD {
        description "send only standard communities";
      }
      enum EXTENDED {
        description "send only extended communities";
      }
      enum BOTH {
        description "send both standard and extended communities";
      }
      enum NONE {
        description "do not send any community attribute";
      }
    }
    description
      "type describing variations of community attributes:
      STANDARD: standard BGP community [rfc1997]
      EXTENDED: extended BGP community [rfc4360]
      BOTH: both standard and extended community";
  }
}
<CODE ENDS>
       
        

9. BGP policy data

    <CODE BEGINS> file "ietf-bgp-policy@2018-05-09.yang"
module ietf-bgp-policy {
  yang-version "1.1";

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

  prefix "bgp-pol";

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


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

  revision "2018-05-09" {
    description
      "Initial Version";
    reference 
      "RFC XXX, BGP Model for Service Provider Network.";
  }

  // typedef statements

  typedef bgp-set-community-option-type {
    type enumeration {
      enum ADD {
        description
          "add the specified communities to the existing
          community attribute";
      }
      enum REMOVE {
        description
          "remove the specified communities from the
          existing community attribute";
      }
      enum 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 {
          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]+";
      }
      type enumeration {
        enum IGP {
          description "set the MED value to the IGP cost toward the
          next hop for the route";
        }
      }
    }
    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).";
  }

  // grouping statements


  grouping match-community-top {
    description
      "Top-level grouping for match conditions on communities";

    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/" +
            "bgp-pol:bgp-defined-sets/bgp-pol:community-sets/" +
            "bgp-pol:community-set/bgp-pol:community-set-name";
        }
        description
          "References a defined community set";
      }

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

  grouping match-ext-community-top {
    description
      "Top-level grouping for match conditions on extended
      communities";

    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/" +
            "bgp-pol:bgp-defined-sets/bgp-pol:ext-community-sets/" +
            "bgp-pol:ext-community-set/" +
            "bgp-pol:ext-community-set-name";
        }
        description "References a defined extended community set";
      }

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

  grouping match-as-path-top {
    description
      "Top-level grouping for match conditions on AS path set";

    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/" +
            "bgp-pol:bgp-defined-sets/bgp-pol:as-path-sets/" +
            "bgp-pol:as-path-set/bgp-pol:as-path-set-name";
        }
        description "References a defined AS path set";
      }
      uses rpol:match-set-options-group;
    }
  }

  grouping bgp-match-set-conditions {
    description
      "Condition statement definitions for checking membership in a
      defined set";

    uses match-community-top;
    uses match-ext-community-top;
    uses match-as-path-top;
  }

  grouping community-count-top {
    description
      "Top-level grouping for community count condition";

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

  grouping as-path-length-top {
    description
      "Top-level grouping for AS path length condition";

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

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

    container bgp-conditions {
      description
        "Top-level container ";

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

      leaf origin-eq {
        type bgp-types: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 bgp-types: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 {
            description "route type is internal";
          }
          enum EXTERNAL {
            description "route type is external";
          }
        }
        description
          "Condition to check the route type in the route update";
      }

      uses community-count-top;
      uses as-path-length-top;
      uses bgp-match-set-conditions;
    }
  }

  grouping community-set-top {
    description
      "Top-level grouping for BGP community sets";

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

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

        leaf community-set-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 {
          type union {
            type bgp-types:bgp-std-community-type;
            type bgp-types:bgp-community-regexp-type;
            type bgp-types:bgp-well-known-community-type;
          }
          description
            "members of the community set";
        }
      }
    }
  }

  grouping ext-community-set-top {
    description
      "Top-level grouping for extended BGP community sets";

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

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

  grouping as-path-set-top {
    description
      "Top-level grouping for AS path sets";

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

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

        leaf as-path-set-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 {
          // TODO: need to refine typedef for AS path expressions
          type string;
          description
            "AS path expression -- list of ASes in the set";
        }
      }
    }
  }

  // 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";

      uses community-set-top;
      uses ext-community-set-top;
      uses as-path-set-top;
    }
  }

  grouping as-path-prepend-top {
    description
      "Top-level grouping for the AS path prepend action";

    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.";
      }
    }
  }

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

    leaf method {
      type enumeration {
        enum INLINE {
          description
            "The extended communities are specified inline as a
            list";
        }
        enum 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.";
    }
  }

  grouping set-community-inline-top {
    description
      "Top-level grouping or inline specification of set-community
      action";

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

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

  grouping set-community-reference-top {
    description
      "Top-level grouping for referencing a community-set in the
      set-community action";

    container reference {
      when "../config/method=REFERENCE" {
        description
          "Active only when the set-community method is 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/" +
            "bgp-pol:bgp-defined-sets/" +
            "bgp-pol:community-sets/bgp-pol:community-set/" +
            "bgp-pol:community-set-name";
        }
        description
          "References a defined community set by name";
      }
    }
  }

  grouping set-community-action-top {
    description
      "Top-level grouping for the set-community action";

    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;
      uses set-community-inline-top;
      uses set-community-reference-top;
    }
  }

  grouping set-ext-community-inline-top {
    description
      "Top-level grouping or inline specification of
       set-ext-community action";

    container inline {
      when "../config/method=INLINE" {
        description
          "Active only when the set-community method is 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 bgp-types:bgp-well-known-community-type;
        }
        description
          "Set the extended community values for the update inline
           with a list.";
      }
    }
  }

  grouping set-ext-community-reference-top {
    description
      "Top-level grouping for referening an extended community-set
      in the set-community action";

    container reference {
      when "../config/method=REFERENCE" {
        description
          "Active only when the set-community method is 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/" +
            "bgp-pol:bgp-defined-sets/bgp-pol:ext-community-sets/" +
            "bgp-pol:ext-community-set/" +
            "bgp-pol:ext-community-set-name";
        }
        description
          "References a defined extended community set by name";
      }
    }
  }

  grouping set-ext-community-action-top {
    description
      "Top-level grouping for the set-ext-community action";

    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;
      uses set-ext-community-inline-top;
      uses set-ext-community-reference-top;
    }
  }

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

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

      leaf set-route-origin {
        type bgp-types: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";
      }
      uses as-path-prepend-top;
      uses set-community-action-top;
      uses set-ext-community-action-top;
    }
  }

  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";

    uses bgp-conditions-top;
  }

  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";

    uses bgp-actions-top;
  }

  // rpc statements

  // notification statements
}
    <CODE ENDS>
    

10. Contributors

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

11. 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.

12. References

12.1. Normative references

[I-D.ietf-rtgwg-ni-model] Berger, L., Hopps, C., Lindem, A., Bogdanovic, D. and X. Liu, "YANG Model for Network Instances", Internet-Draft draft-ietf-rtgwg-ni-model-12, March 2018.
[RFC1997] Chandra, R., Traina, P. and T. Li, "BGP Communities Attribute", RFC 1997, DOI 10.17487/RFC1997, August 1996.
[RFC2439] Villamizar, C., Chandra, R. and R. Govindan, "BGP Route Flap Damping", RFC 2439, DOI 10.17487/RFC2439, November 1998.
[RFC3688] Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688, DOI 10.17487/RFC3688, January 2004.
[RFC4271] Rekhter, Y., Li, T. and S. Hares, "A Border Gateway Protocol 4 (BGP-4)", RFC 4271, DOI 10.17487/RFC4271, January 2006.
[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.
[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.
[RFC4760] Bates, T., Chandra, R., Katz, D. and Y. Rekhter, "Multiprotocol Extensions for BGP-4", RFC 4760, DOI 10.17487/RFC4760, January 2007.
[RFC5065] Traina, P., McPherson, D. and J. Scudder, "Autonomous System Confederations for BGP", RFC 5065, DOI 10.17487/RFC5065, August 2007.
[RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer Security (TLS) Protocol Version 1.2", RFC 5246, DOI 10.17487/RFC5246, August 2008.
[RFC6020] Bjorklund, M., "YANG - A Data Modeling Language for the Network Configuration Protocol (NETCONF)", RFC 6020, DOI 10.17487/RFC6020, October 2010.
[RFC6241] Enns, R., Bjorklund, M., Schoenwaelder, J. and A. Bierman, "Network Configuration Protocol (NETCONF)", RFC 6241, DOI 10.17487/RFC6241, June 2011.
[RFC6242] Wasserman, M., "Using the NETCONF Protocol over Secure Shell (SSH)", RFC 6242, DOI 10.17487/RFC6242, June 2011.
[RFC6811] Mohapatra, P., Scudder, J., Ward, D., Bush, R. and R. Austein, "BGP Prefix Origin Validation", RFC 6811, DOI 10.17487/RFC6811, January 2013.
[RFC6991] Schoenwaelder, J., "Common YANG Data Types", RFC 6991, DOI 10.17487/RFC6991, July 2013.
[RFC7950] Bjorklund, M., "The YANG 1.1 Data Modeling Language", RFC 7950, DOI 10.17487/RFC7950, August 2016.
[RFC8040] Bierman, A., Bjorklund, M. and K. Watsen, "RESTCONF Protocol", RFC 8040, DOI 10.17487/RFC8040, January 2017.
[RFC8341] Bierman, A. and M. Bjorklund, "Network Configuration Access Control Model", STD 91, RFC 8341, DOI 10.17487/RFC8341, March 2018.
[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.

12.2. Informative references

[I-D.ietf-rtgwg-policy-model] Qu, Y., Tantsura, J., Lindem, A., Liu, X. and A. Shaikh, "A YANG Data Model for Routing Policy Management", Internet-Draft draft-ietf-rtgwg-policy-model-02, March 2018.
[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.

Authors' Addresses

Keyur Patel Arrcus CA USA EMail: keyur@arrcus.com
Mahesh Jethanandani EMail: mjethanandani@gmail.com
Susan Hares Huawei 7453 Hickory Hill Saline, MI 48176 USA EMail: shares@ndzh.com