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Versions: 00 01

Interdomain Routing                                        K. Patel, Ed.
Internet-Draft                                                    Arrcus
Intended status: Standards Track                    M. Jethanandani, Ed.
Expires: May 19, 2018
                                                           S. Hares, Ed.
                                                 Hickory Hill Consulting
                                                       November 15, 2017


                             BGP YANG Model
                    draft-mks-idr-bgp-yang-model-01

Abstract

   This Internet draft provides a set of example text for the
   replacement of draft-ietf-idr-bgp-model-02.txt with the IETF models
   based on the Network Management Datastore Architecture to be released
   in draft-ietf-idr-bgp-model-03.txt.  This draft is provided for the
   IDR WG by potential editors as example text for draft-ietf-idr-bgp-
   model-03.txt for the yang models.  Please send review comments or
   suggestions to these potential editors and the IDR working group
   (idr@ietf.org).

   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/.

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

   This Internet-Draft will expire on May 19, 2018.








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Copyright Notice

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

   This document is subject to BCP 78 and the IETF Trust's Legal
   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  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Goals and approach  . . . . . . . . . . . . . . . . . . .   3
   2.  Model overview  . . . . . . . . . . . . . . . . . . . . . . .   4
     2.1.  BGP protocol configuration  . . . . . . . . . . . . . . .   5
     2.2.  Policy configuration overview . . . . . . . . . . . . . .   7
     2.3.  Operational state overview  . . . . . . . . . . . . . . .   8
   3.  Relation to other YANG data models  . . . . . . . . . . . . .   8
   4.  Security Considerations . . . . . . . . . . . . . . . . . . .   9
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   9
   6.  YANG modules  . . . . . . . . . . . . . . . . . . . . . . . .   9
   7.  BGP main module and submodule for base items  . . . . . . . .  10
   8.  BGP types . . . . . . . . . . . . . . . . . . . . . . . . . .  50
   9.  BGP policy data . . . . . . . . . . . . . . . . . . . . . . .  59
   10. References  . . . . . . . . . . . . . . . . . . . . . . . . .  73
     10.1.  Normative references . . . . . . . . . . . . . . . . . .  73
     10.2.  Informative references . . . . . . . . . . . . . . . . .  74
   Appendix A.  Acknowledgements . . . . . . . . . . . . . . . . . .  75
   Appendix B.  Change summary . . . . . . . . . . . . . . . . . . .  75
     B.1.  Changes between revisions -01 and -02 . . . . . . . . . .  75
     B.2.  Changes between revisions -00 and -01 . . . . . . . . . .  75
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  75

1.  Introduction

   This Internet draft is a set of example text for the replacement of
   draft-ietf-idr-bgp-model-02.txt with a version of the yang models
   which are compatible with the Network Management Datastore
   Architecture to be released in draft-ietf-idr-bgp-model-03.txt.  This
   draft is only for provided an example structure for the IDR WG by the
   potential editors for draft-ietf-idr-bgp-model-03.txt.  The authors
   of the draft-ietf-bgp-model-02.txt are:



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   o  Anees Shaikh

   o  Rob Shakir

   o  Keyur Patel

   o  Susan Hares

   o  Kevin D'Souza

   o  Deepak Bansal

   o  Alex Clemm

   o  Alex Zhdankin

   o  Mahesh Jethanandani

   o  Xufeng Liu

   This document describes a YANG data model for the BGP [RFC4271]
   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 [RFC4271], [RFC1997],
   [RFC4456], [RFC4760], [RFC3065], [RFC2439], [RFC4724], and [RFC6811].

   Along with configuration of base BGP features, this model also
   addresses policy configuration, by providing "hooks" for applying
   policies, and also defining BGP-specific policy features.  The BGP
   policy features are intended to be used with the general routing
   policy model defined in [I-D.ietf-rtgwg-policy-model].  The model
   also supports operational state data to provide a common model for
   reading BGP-related state from a BGP speaker.






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

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

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

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

   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:

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

   o  multiprotocol configuration -- configuration affecting individual
      address-families within BGP [RFC4760].

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



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

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

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

   These modules also make use of standard Internet types, such as IP
   addresses and prefixes, autonomous system numbers, etc., defined in
   RFC 6991 [RFC6991].

   Throughout the model, the approach described in NMDA
   [I-D.ietf-netmod-revised-datastores] is used to represent running
   configuration, intended and operational datastore.  That is to say,
   that the model defines a single container, and it is the
   implementation of the different datastores that reflects the value of
   a given node in either the <running>, <intended> or <operational>
   datastore.

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.



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   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:




















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           +--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 [I-D.ietf-rtgwg-policy-model],
   which represents a condition-action policy framework for routing.
   This model adds BGP-specific conditions (e.g., matching on the
   community attribute), and actions (e.g., setting local preference) to
   the generic policy framework.

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

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

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

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



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

              +--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

2.3.  Operational state overview

   The BGP operational model contains data which relates to the
   operational state of the various elements of the BGP router.  As
   noted in Section 2 - the approach described in NMDA
   [I-D.ietf-netmod-revised-datastores] is utilized for the modeling of
   operational and statistical data.  To this end, the "-state"
   groupings (those that contain derived operational parameters) is not
   a separate container, but is instead collapsed into one container
   that defines both the read-write and read-only nodes.  In some cases,
   operational information may be relevant to one instance of a common
   grouping, but not another - for example, the number of received,
   advertised, and installed prefixes is relevant on a per-neighbor-
   basis, but is not required (or meaningful) in the peer-group context.
   Groupings are defined with the appropriate operational state data
   accordingly.

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 [I-D.ietf-rtgwg-ni-model] 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




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   and instantiates the BGP model in its tree at /network-instances/
   network-instance/protocols/protocol/bgp/...

   It is also possible to integrate the BGP model with the Routing
   Management model [I-D.ietf-netmod-routing-cfg] or the Network Device
   Organizational Model [I-D.rtgyangdt-rtgwg-device-model], both of
   which define the notion of routing instances, or VRFs.

4.  Security Considerations

   BGP configuration has a significant impact on network operations, and
   as such any related protocol or model carries potential security
   risks.

   YANG data models are generally designed to be used with the NETCONF
   protocol over an SSH transport.  This provides an authenticated and
   secure channel over which to transfer BGP configuration and
   operational data.  Note that use of alternate transport or data
   encoding (e.g., JSON over HTTPS) would require similar mechanisms for
   authenticating and securing access to configuration data.

   Most of the data elements in the configuration model could be
   considered sensitive from a security standpoint.  Unauthorized access
   or invalid data could cause major disruption.

5.  IANA Considerations

   An appropriate namespace URI will be registered in the IETF XML
   Registry" [RFC3688].  The BGP YANG modules will be registered in the
   "YANG Module Names" registry [RFC6020].

6.  YANG modules

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

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

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

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

   o  ietf-bgp-common-structure - defines groupings that are shared by
      multiple contexts, but are used only to create structural



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      elements, i.e., containers (leaf nodes are defined in separate
      groupings)

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

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

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

   Additional modules include:

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

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

7.  BGP main module and submodule for base items

   <CODE BEGINS> file "ietf-bgp@2017-10-17.yang"
   module ietf-bgp {

     yang-version "1";

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

     prefix "bgp";

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

     // Common: defines the groupings that are common across more than
     //         one context (where contexts are neighbor, group, global)
     include ietf-bgp-common;
     // Multiprotocol: defines the groupings that are common across more
     //                than one context, and relate to Multiprotocol
     include ietf-bgp-common-multiprotocol;
     // Structure: defines groupings that are shared but are solely used
     //            for structural reasons.
     include ietf-bgp-common-structure;
     // Include peer-group/neighbor/global - these define the groupings



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     // that are specific to one context
     include ietf-bgp-neighbor;
     include ietf-bgp-global;
     include ietf-bgp-peer-group;

     // 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 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 "2017-10-17" {
       description
         "Initial Version";
       reference
         "RFC XXXX, BGP Model for Service Provider Network ";



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     }

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

       container global {
         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@2017-10-17.yang"
   submodule ietf-bgp-common {
     belongs-to ietf-bgp {
       prefix "bgp";
     }

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

     // meta
     organization
       "IETF IDR Working Group";



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     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 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 "2017-10-17" {
       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



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           "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.";



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       }

       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";



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       }
     }

     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



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         "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 thate 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";



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       }

       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 multipath applicable
          to all contexts";

       leaf allow-multiple-as {
        type boolean;
        default "false";
        description
         "Allow multipath to use paths from different neighbouring ASes.
          The default is to only consider multiple paths from the same
          neighbouring 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";




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       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
             "Multipath parameters for eBGP";

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

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

         container ibgp {
           description
             "Multipath parameters for iBGP";

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

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




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       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";
         }




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         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@2017-10-17.yang"
   submodule ietf-bgp-common-multiprotocol {
     belongs-to ietf-bgp {
       prefix "bgp";
     }

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

     include ietf-bgp-common;



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     // 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 "2017-10-17" {
       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";



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       }

       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;




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         // 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";



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       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";



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         // 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
       }
     }



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     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



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           "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



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          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@2017-10-17.yang"
   submodule ietf-bgp-common-structure {

     belongs-to ietf-bgp {
       prefix "bgp";
     }

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



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     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 "2017-10-17" {
       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 {



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       description
         "Structural grouping used to include eBGP multihop
          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 {



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           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 {



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           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@2017-10-17.yang"
   submodule ietf-bgp-peer-group {
     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



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       "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 BGP module.";

     revision "2017-10-17" {
       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



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             "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;



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       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@2017-10-17.yang"
   submodule ietf-bgp-neighbor {
     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 {



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       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 BGP module.";

     revision "2017-10-17" {
       description
         "Initial Version";
       reference
         "RFC XXX, BGP Model for Service Provider Network.";
     }

     grouping bgp-neighbor-use-multiple-paths {
       description
         "Multipath 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
             "Multipath configuration for eBGP";



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           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.";
         }



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         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;



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       }
     }

     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



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                 "neighbor is down, and the local system is awaiting a
                  conncetion 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



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            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



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             "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";



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         }
       }

       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



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             "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";



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         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@2017-10-17.yang"
   submodule ietf-bgp-global {
     belongs-to ietf-bgp {
       prefix "bgp";
     }

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

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

     // 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,



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                 Mahesh Jethanandani,
                 Susan Hares";

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

     revision "2017-10-17" {
       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



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         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 {



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       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";




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         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@2017-10-17.yang"
   module ietf-bgp-types {
     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";




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     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 "2017-10-17" {
       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";



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

     identity AFI_SAFI_TYPE {
       description
         "Base identity type for AFI,SAFI tuples for BGP-4";
       reference "RFC4760 - multiprotocol 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)";



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       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";
     }




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     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 readvertise 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;
       }



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       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 commmunity 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]|'      +



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                   '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.



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       //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



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         "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";



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         }
         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@2017-10-17.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-policy-types {
       prefix pol-types;
     }
     import ietf-bgp-types {
       prefix bgp-types;
     }

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



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     }


     // 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 "2017-10-17" {
       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.";



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         }
       }
       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";




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       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



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         "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";

         uses pol-types:attribute-compare-operators;
       }
     }

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

       container as-path-length {
         description



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           "Value and comparison operations for conditions based on the
           length of the AS path in the route update";

         uses pol-types:attribute-compare-operators;
       }
     }

     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



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             "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;



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               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



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           "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";



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         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";



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       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 referening 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";
         }
       }
     }




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     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";




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       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";



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         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



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     // notification statements
   }
       <CODE ENDS>


10.  References

10.1.  Normative references

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

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

   [RFC3065]  Traina, P., McPherson, D., and J. Scudder, "Autonomous
              System Confederations for BGP", RFC 3065,
              DOI 10.17487/RFC3065, February 2001,
              <https://www.rfc-editor.org/info/rfc3065>.

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

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

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

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

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






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

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

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

10.2.  Informative references

   [I-D.ietf-netmod-revised-datastores]
              Bjorklund, M., Schoenwaelder, J., Shafer, P., Watsen, K.,
              and R. Wilton, "Network Management Datastore
              Architecture", draft-ietf-netmod-revised-datastores-06
              (work in progress), October 2017.

   [I-D.ietf-netmod-routing-cfg]
              Lhotka, L. and A. Lindem, "A YANG Data Model for Routing
              Management", draft-ietf-netmod-routing-cfg-25 (work in
              progress), November 2016.

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

   [I-D.ietf-rtgwg-policy-model]
              Shaikh, A., Shakir, R., D'Souza, K., and C. Chase,
              "Routing Policy Configuration Model for Service Provider
              Networks", draft-ietf-rtgwg-policy-model-01 (work in
              progress), April 2016.

   [I-D.rtgyangdt-rtgwg-device-model]
              Lindem, A., Berger, L., Bogdanovic, D., and C. Hopps,
              "Network Device YANG Organizational Models", draft-
              rtgyangdt-rtgwg-device-model-05 (work in progress), August
              2016.








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Appendix A.  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.

Appendix B.  Change summary

B.1.  Changes between revisions -01 and -02

   o  Refactored BGP model such that it is comprised of multiple sub-
      modules rather than independent modules.

   o  Remove the need for self-augmentation of the BGP model to allow
      the ability to import the model in wider structures more easily.

   o  Added new operational state values for BGP session established
      transitions and last-established timestamp.  Also deprecated
      uptime operational state leaf.

   o  Added ability to select eligible paths for add-paths based on a
      policy.

B.2.  Changes between revisions -00 and -01

   o  Updated module namespaces to reflect IETF standard namespace.

   o  Updated module filenames with ietf- prefix per RFC 6087
      guidelines.

Authors' Addresses

   Keyur Patel (editor)
   Arrcus
   CA
   USA

   Email: keyur@arrcus.com









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   Mahesh Jethanandani (editor)
   CA
   USA

   Email: mjethanandani@gmail.com


   Susan Hares (editor)
   Hickory Hill Consulting
   7453 Hickory Hill
   Saline, MI  48176
   USA

   Email: shares@ndzh.com





































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