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Versions: (draft-shaikh-rtgwg-policy-model) 00 01 02 03

RTGWG                                                              Y. Qu
Internet-Draft                                                    Huawei
Intended status: Informational                               J. Tantsura
Expires: December 31, 2018                                Nuage Networks
                                                               A. Lindem
                                                                   Cisco
                                                                  X. Liu
                                                                   Jabil
                                                               A. Shaikh
                                                                  Google
                                                           June 29, 2018


            A YANG Data Model for Routing Policy Management
                    draft-ietf-rtgwg-policy-model-03

Abstract

   This document defines a YANG data model for configuring and managing
   routing policies in a vendor-neutral way and based on actual
   operational practice.  The model provides a generic policy framework
   which can be augmented with protocol-specific policy configuration.

Status of This Memo

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

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

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

   This Internet-Draft will expire on December 31, 2018.

Copyright Notice

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

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (https://trustee.ietf.org/license-info) in effect on the date of



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   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  . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  Route policy expression . . . . . . . . . . . . . . . . . . .   4
     3.1.  Defined sets for policy matching  . . . . . . . . . . . .   4
     3.2.  Policy conditions . . . . . . . . . . . . . . . . . . . .   5
     3.3.  Policy actions  . . . . . . . . . . . . . . . . . . . . .   6
     3.4.  Policy subroutines  . . . . . . . . . . . . . . . . . . .   7
   4.  Policy evaluation . . . . . . . . . . . . . . . . . . . . . .   7
   5.  Applying routing policy . . . . . . . . . . . . . . . . . . .   8
   6.  Routing protocol-specific policies  . . . . . . . . . . . . .   8
   7.  Security Considerations . . . . . . . . . . . . . . . . . . .  11
   8.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  11
   9.  YANG modules  . . . . . . . . . . . . . . . . . . . . . . . .  11
     9.1.  Routing policy model  . . . . . . . . . . . . . . . . . .  11
   10. Policy examples . . . . . . . . . . . . . . . . . . . . . . .  28
   11. References  . . . . . . . . . . . . . . . . . . . . . . . . .  28
     11.1.  Normative references . . . . . . . . . . . . . . . . . .  28
     11.2.  Informative references . . . . . . . . . . . . . . . . .  29
   Appendix A.  Acknowledgements . . . . . . . . . . . . . . . . . .  29
   Appendix B.  Change summary . . . . . . . . . . . . . . . . . . .  29
     B.1.  Changes between revisions -01 and -02 . . . . . . . . . .  29
     B.2.  Changes between revisions -00 and -01 . . . . . . . . . .  29
     B.3.  Changes between revisions draft-shaikh-rtgwg-policy-model
           and -00 . . . . . . . . . . . . . . . . . . . . . . . . .  29
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  29

1.  Introduction

   This document describes a YANG [RFC6020] [RFC7950] data model for
   routing policy configuration based on operational usage and best
   practices in a variety of service provider networks.  The model is
   intended to be vendor-neutral, in order to allow operators to manage
   policy configuration in a consistent, intuitive way in heterogeneous
   environments with routers supplied by multiple vendors.

   The YANG modules in this document conform to the Network Management
   Datastore Architecture (NMDA)[I-D.ietf-netmod-revised-datastores].




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1.1.  Goals and approach

   This model does not aim to be feature complete -- it is a subset of
   the policy configuration parameters available in a variety of vendor
   implementations, but supports widely used constructs for managing how
   routes are imported, exported, and modified across different routing
   protocols.  The model development approach has been to examine actual
   policy configurations in use across a number of operator networks.
   Hence the focus is on enabling policy configuration capabilities and
   structure that are in wide use.

   Despite the differences in details of policy expressions and
   conventions in various vendor implementations, the model reflects the
   observation that a relatively simple condition-action approach can be
   readily mapped to several existing vendor implementations, and also
   gives operators an intuitive and straightforward way to express
   policy without sacrificing flexibility.  A side affect of this design
   decision is that legacy methods for expressing policies are not
   considered.  Such methods could be added as an augmentation to the
   model if needed.

   Consistent with the goal to produce a data model that is vendor
   neutral, only policy expressions that are deemed to be widely
   available in existing major implementations are included in the
   model.  Those configuration items that are only available from a
   single implementation are omitted from the model with the expectation
   they will be available in separate vendor-provided modules that
   augment the current model.

2.  Model overview

   The routing policy module has three main parts:

   o  A generic framework to express policies as sets of related
      conditions and actions.  This includes match sets and actions that
      are useful across many routing protocols.

   o  A structure that allows routing protocol models to add protocol-
      specific policy conditions and actions though YANG augmentations.
      There is a complete example of this for BGP [RFC4271] policies in
      the proposed vendor-neutral BGP data model
      [I-D.ietf-idr-bgp-model].

   o  A reusable grouping for attaching import and export rules in the
      context of routing configuration for different protocols, VRFs,
      etc.  This also enables creation of policy chains and expressing
      default policy behavior.




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   The module makes use of the standard Internet types, such as IP
   addresses, autonomous system numbers, etc., defined in RFC 6991
   [RFC6991].

3.  Route policy expression

   Policies are expressed as a sequence of top-level policy definitions
   each of which consists of a sequence of policy statements.  Policy
   statements in turn consist of simple condition-action tuples.
   Conditions may include multiple match or comparison operations, and
   similarly, actions may effect multiple changes to route attributes,
   or indicate a final disposition of accepting or rejecting the route.
   This structure is shown below.

      +--rw routing-policy
         +--rw policy-definitions
            +--rw policy-definition* [name]
               +--rw name          string
               +--rw statements
                  +--rw statement* [name]
                     +--rw name          string
                     +--rw conditions
                     |     ...
                     +--rw actions
                           ...

3.1.  Defined sets for policy matching

   The models provides a set of generic sets that can be used for
   matching in policy conditions.  These sets are applicable for route
   selection across multiple routing protocols.  They may be further
   augmented by protocol-specific models which have their own defined
   sets.  The supported defined sets include:

   o  prefix sets - define a set of IP prefixes, each with an associated
      CIDR netmask range (or exact length)

   o  neighbor sets - define a set of neighboring nodes by their IP
      addresses.  These sets are used for selecting routes based on the
      neighbors advertising the routes.

   o  tag set - define a set of generic tag values that can be used in
      matches for filtering routes

   The model structure for defined sets is shown below.






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       +--rw routing-policy
          +--rw defined-sets
          |  +--rw prefix-sets
          |  |  +--rw prefix-set* [name]
          |  |     +--rw name        string
          |  |     +--rw mode?       enumeration
          |  |     +--rw prefixes
          |  |        +--rw prefix-list* [ip-prefix masklength-lower
          |  |                            masklength-upper]
          |  |           +--rw ip-prefix           inet:ip-prefix
          |  |           +--rw masklength-lower    uint8
          |  |           +--rw masklength-upper    uint8
          |  +--rw neighbor-sets
          |  |  +--rw neighbor-set* [name]
          |  |     +--rw name       string
          |  |     +--rw address*   inet:ip-address
          |  +--rw tag-sets
          |     +--rw tag-set* [name]
          |        +--rw name         string
          |        +--rw tag-value*   tag-type


3.2.  Policy conditions

   Policy statements consist of a set of conditions and actions (either
   of which may be empty).  Conditions are used to match route
   attributes against a defined set (e.g., a prefix set), or to compare
   attributes against a specific value.

   Match conditions may be further modified using the match-set-options
   configuration which allows operators to change the behavior of a
   match.  Three options are supported:

   o  ALL - match is true only if the given value matches all members of
      the set.

   o  ANY - match is true if the given value matches any member of the
      set.

   o  INVERT - match is true if the given value does not match any
      member of the given set.

   Not all options are appropriate for matching against all defined sets
   (e.g., match ALL in a prefix set does not make sense).  In the model,
   a restricted set of match options is used where applicable.






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   Comparison conditions may similarly use options to change how route
   attributes should be tested, e.g., for equality or inequality,
   against a given value.

   While most policy conditions will be added by individual routing
   protocol models via augmentation, this routing policy model includes
   several generic match conditions and also the ability to test which
   protocol or mechanism installed a route (e.g., BGP, IGP, static,
   etc.).  The conditions included in the model are shown below.

   +--rw routing-policy
     +--rw policy-definitions
         +--rw policy-definition* [name]
            +--rw name          string
            +--rw statements
               +--rw statement* [name]
                  +--rw conditions
                  |  +--rw call-policy?
                  |  +--rw install-protocol-eq?
                  |  +--rw match-interface
                  |  |  +--rw interface?
                  |  |  +--rw subinterface?
                  |  +--rw match-prefix-set
                  |  |  +--rw prefix-set?
                  |  |  +--rw match-set-options?
                  |  +--rw match-neighbor-set
                  |  |  +--rw neighbor-set?
                  |  +--rw match-tag-set
                  |     +--rw tag-set?
                  |     +--rw match-set-options?

3.3.  Policy actions

   When policy conditions are satisfied, policy actions are used to set
   various attributes of the route being processed, or to indicate the
   final disposition of the route, i.e., accept or reject.

   Similar to policy conditions, the routing policy model includes
   generic actions in addition to the basic route disposition actions.
   These are shown below.











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       +--rw routing-policy
         +--rw policy-definitions
            +--rw policy-definition* [name]
               +--rw statements
                  +--rw statement* [name]
                     +--rw actions
                       +--rw policy-result?    policy-result-type
                       +--rw set-metric?       uint16
                       +--rw set-preference?   uint8

3.4.  Policy subroutines

   Policy 'subroutines' (or nested policies) are supported by allowing
   policy statement conditions to reference other policy definitions
   using the call-policy configuration.  Called policies apply their
   conditions and actions before returning to the calling policy
   statement and resuming evaluation.  The outcome of the called policy
   affects the evaluation of the calling policy.  If the called policy
   results in an accept-route (either explicit or by default), then the
   subroutine returns an effective boolean true value to the calling
   policy.  For the calling policy, this is equivalent to a condition
   statement evaluating to a true value and evaluation of the policy
   continues (see Section 4).  Note that the called policy may also
   modify attributes of the route in its action statements.  Similarly,
   a reject-route action returns false and the calling policy evaluation
   will be affected accordingly.  Consequently, a subroutine cannot
   explicitly accept or reject a route.  Rather it merely provides an
   indication that 'call-policy' condition returns boolean true or false
   indicating whether or not the condition matches.  Route acceptance or
   rejection is solely determined by the top-level policy.

   Note that the called policy may itself call other policies (subject
   to implementation limitations).  The model does not prescribe a
   nesting depth because this varies among implementations.  For
   example, some major implementation may only support a single level of
   subroutine recursion.  As with any routing policy construction, care
   must be taken with nested policies to ensure that the effective
   return value results in the intended behavior.  Nested policies are a
   convenience in many routing policy constructions but creating
   policies nested beyond a small number of levels (e.g., 2-3) should be
   discouraged.

4.  Policy evaluation

   Evaluation of each policy definition proceeds by evaluating its
   corresponding individual policy statements in order.  When a
   condition statement in a policy statement is satisfied, the
   corresponding action statement is executed.  If the action statement



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   has either accept-route or reject-route actions, evaluation of the
   current policy definition stops, and no further policy definitions in
   the chain are evaluated.

   If the condition is not satisfied, then evaluation proceeds to the
   next policy statement.  If none of the policy statement conditions
   are satisfied, then evaluation of the current policy definition
   stops, and the next policy definition in the chain is evaluated.
   When the end of the policy chain is reached, the default route
   disposition action is performed (i.e., reject-route unless an
   alternate default action is specified for the chain).

5.  Applying routing policy

   Routing policy is applied by defining and attaching policy chains in
   various routing contexts.  Policy chains are sequences of policy
   definitions (described in Section 3) that have an associated
   direction (import or export) with respect to the routing context in
   which they are defined.  The routing policy model defines an apply-
   policy grouping that can be imported and used by other models.  As
   shown below, it allows definition of import and export policy chains,
   as well as specifying the default route disposition to be used when
   no policy definition in the chain results in a final decision.

         +--rw apply-policy
         |  +--rw import-policy*
         |  +--rw default-import-policy?   default-policy-type
         |  +--rw export-policy*
         |  +--rw default-export-policy?   default-policy-type

   The default policy defined by the model is to reject the route for
   both import and export policies.

6.  Routing protocol-specific policies

   Routing models that require the ability to apply routing policy may
   augment the routing policy model with protocol or other specific
   policy configuration.  The routing policy model assumes that
   additional defined sets, conditions, and actions may all be added by
   other models.

   An example of this is shown below, in which the BGP configuration
   model in [I-D.ietf-idr-bgp-model] adds new defined sets to match on
   community values or AS paths.  The model similarly augments BGP-
   specific conditions and actions in the corresponding sections of the
   routing policy model.

module: ietf-routing-policy



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    +--rw routing-policy
       +--rw defined-sets
       |  +--rw prefix-sets
       |  |  +--rw prefix-set* [name]
       |  |     +--rw name        string
       |  |     +--rw mode?       enumeration
       |  |     +--rw prefixes
       |  |        +--rw prefix-list* [ip-prefix masklength-lower
       |  |                            masklength-upper]
       |  |           +--rw ip-prefix           inet:ip-prefix
       |  |           +--rw masklength-lower    uint8
       |  |           +--rw masklength-upper    uint8
       |  +--rw neighbor-sets
       |  |  +--rw neighbor-set* [name]
       |  |     +--rw name       string
       |  |     +--rw address*   inet:ip-address
       |  +--rw tag-sets
       |  |  +--rw tag-set* [name]
       |  |     +--rw name         string
       |  |     +--rw tag-value*   tag-type
       |  +--rw bgp-pol:bgp-defined-sets
       |     +--rw bgp-pol:community-sets
       |     |  +--rw bgp-pol:community-set* [community-set-name]
       |     |     +--rw bgp-pol:community-set-name    string
       |     |     +--rw bgp-pol:community-member*     union
       |     +--rw bgp-pol:ext-community-sets
       |     |  +--rw bgp-pol:ext-community-set* [ext-community-set-name]
       |     |     +--rw bgp-pol:ext-community-set-name    string
       |     |     +--rw bgp-pol:ext-community-member*     union
       |     +--rw bgp-pol:as-path-sets
       |        +--rw bgp-pol:as-path-set* [as-path-set-name]
       |           +--rw bgp-pol:as-path-set-name      string
       |           +--rw bgp-pol:as-path-set-member*   string
       +--rw policy-definitions
          +--rw policy-definition* [name]
             +--rw name          string
             +--rw statements
                +--rw statement* [name]
                   +--rw name          string
                   +--rw conditions
                   |  +--rw call-policy?
                   |  +--rw source-protocol?          identityref
                   |  +--rw match-interface
                   |  |  +--rw interface?
                   |  |  +--rw subinterface?
                   |  +--rw match-prefix-set
                   |  |  +--rw prefix-set?
                   |  |  +--rw match-set-options? match-set-options-type



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                   |  +--rw match-neighbor-set
                   |  |  +--rw neighbor-set?
                   |  +--rw match-tag-set
                   |  |  +--rw tag-set?
                   |  |  +--rw match-set-options? match-set-options-type
                   |  +--rw bgp-pol:bgp-conditions
                   |     +--rw bgp-pol:med-eq?      uint32
                   |     +--rw bgp-pol:origin-eq?
                   |           bgp-types:bgp-origin-attr-type
                   |     +--rw bgp-pol:next-hop-in*
                   |           inet:ip-address-no-zone
                   |     +--rw bgp-pol:afi-safi-in*   identityref
                   |     +--rw bgp-pol:local-pref-eq? uint32
                   |     +--rw bgp-pol:route-type?    enumeration
                   |     +--rw bgp-pol:community-count
                   |     +--rw bgp-pol:as-path-length
                   |     +--rw bgp-pol:match-community-set
                   |     |  +--rw bgp-pol:community-set?
                   |     |  +--rw bgp-pol:match-set-options?
                   |              match-set-options-type
                   |     +--rw bgp-pol:match-ext-community-set
                   |     |  +--rw bgp-pol:ext-community-set?
                   |     |  +--rw bgp-pol:match-set-options?
                   |     |        match-set-options-type
                   |     +--rw bgp-pol:match-as-path-set
                   |        +--rw bgp-pol:as-path-set?
                   |        +--rw bgp-pol:match-set-options?
                   |              match-set-options-type
                   +--rw actions
                      +--rw policy-result?         policy-result-type
                      +--rw set-metric?            uint16
                      +--rw set-preference?        uint8
                      +--rw bgp-pol:bgp-actions
                         +--rw bgp-pol:set-route-origin?
                               bgp-types:bgp-origin-attr-type
                         +--rw bgp-pol:set-local-pref?        uint32
                         +--rw bgp-pol:set-next-hop?   bgp-next-hop-type
                         +--rw bgp-pol:set-med?        bgp-set-med-type
                         +--rw bgp-pol:set-as-path-prepend
                         |  +--rw bgp-pol:repeat-n?   uint8
                         +--rw bgp-pol:set-community
                         |  +--rw bgp-pol:method?      enumeration
                         |  +--rw bgp-pol:options?
                                  bgp-set-community-option-type
                         |  +--rw bgp-pol:inline
                         |  |  +--rw bgp-pol:communities*   union
                         |  +--rw bgp-pol:reference
                         |     +--rw bgp-pol:community-set-ref?



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                         +--rw bgp-pol:set-ext-community
                            +--rw bgp-pol:method?       enumeration
                            +--rw bgp-pol:options?
                                  bgp-set-community-option-type
                            +--rw bgp-pol:inline
                            |  +--rw bgp-pol:communities*   union
                            +--rw bgp-pol:reference
                               +--rw bgp-pol:ext-community-set-ref?

7.  Security Considerations

   Routing policy configuration has a significant impact on network
   operations, and, as such, any related 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 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 policy model could be considered
   sensitive from a security standpoint.  Unauthorized access or invalid
   data could cause major disruption.

8.  IANA Considerations

   This YANG data model and the component modules currently use a
   temporary ad-hoc namespace.  If and when it is placed on redirected
   for the standards track, an appropriate namespace URI will be
   registered in the IETF XML Registry" [RFC3688].  The routing policy
   YANG modules will be registered in the "YANG Module Names" registry
   [RFC6020].

9.  YANG modules

   The routing policy model is described by the YANG modules in the
   sections below.

9.1.  Routing policy model

   <CODE BEGINS> file "ietf-routing-policy@2018-06-25.yang"
   module ietf-routing-policy {

     yang-version "1.1";
     namespace "urn:ietf:params:xml:ns:yang:ietf-routing-policy";
     prefix rt-pol;



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

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

     import ietf-interfaces {
       prefix "if";
     }

     import ietf-routing {
       prefix "rt";
     }

     import ietf-interfaces-common {
       prefix if-cmn;
     }

     import ietf-if-l3-vlan {
       prefix "if-l3-vlan";
     }


    organization
       "IETF RTGWG - Routing Area Working Group";
     contact
       "WG Web:   <http://tools.ietf.org/wg/rtgwg/>
        WG List:  <mailto:rtgwg@ietf.org>


        Editor:   Yingzhen Qu
                  <mailto:yingzhen.qu@huawei.com>
                  Jeff Tantsura
                  <mailto:jefftant.ietf@gmail.com>
                  Acee Lindem
                  <mailto:acee@cisco.com>
                  Xufeng Liu
                  <mailto:xufeng_liu@jabil.com>
                  Anees Shaikh
                  <mailto:aashaikh@google.com>";

     description
       "This module describes a YANG model for routing policy
        configuration. It is a limited subset of all of the policy
        configuration parameters available in the variety of vendor
        implementations, but supports widely used constructs for



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        managing how routes are imported, exported, and modified across
        different routing protocols.  This module is intended to be used
        in conjunction with routing protocol configuration modules
        (e.g., BGP) defined in other models.

        Route policy expression:

        Policies are expressed as a set of top-level policy definitions,
        each of which consists of a sequence of policy statements.
        Policy statements consist of simple condition-action tuples.
        Conditions may include mutiple match or comparison operations,
        and similarly actions may be multitude of changes to route
        attributes or a final disposition of accepting or rejecting the
        route.

        Route policy evaluation:

        Policy definitions are referenced in routing protocol
        configurations using import and export configuration statements.
        The arguments are members of an ordered list of named policy
        definitions which comprise a policy chain, and optionally, an
        explicit default policy action (i.e., reject or accept).

        Evaluation of each policy definition proceeds by evaluating its
        corresponding individual policy statements in order.  When a
        condition statement in a policy statement is satisfied, the
        corresponding action statement is executed.  If the action
        statement has either accept-route or reject-route actions,
        policy evaluation of the current policy definition stops, and
        no further policy definitions in the chain are evaluated.

        If the condition is not satisfied, then evaluation proceeds to
        the next policy statement.  If none of the policy statement
        conditions are satisfied, then evaluation of the current policy
        definition stops, and the next policy definition in the chain is
        evaluated.  When the end of the policy chain is reached, the
        default route disposition action is performed (i.e.,
        reject-route unless an alternate default action is specified
        for the chain).

        Policy 'subroutines' (or nested policies) are supported by
        allowing policy statement conditions to reference another policy
        definition which applies conditions and actions from the
        referenced policy before returning to the calling policy
        statement and resuming evaluation.  If the called policy
        results in an accept-route (either explicit or by default), then
        the subroutine returns an effective true value to the calling
        policy.  Similarly, a reject-route action returns false.  If the



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        subroutine returns true, the calling policy continues to
        evaluate the remaining conditions (using a modified route if the
        subroutine performed any changes to the route).";


     revision "2018-06-25" {
       description
         "Initial revision.";
       reference
        "RFC XXXX: Routing Policy Configuration Model for Service
         Provider Networks";
     }


     // typedef statements

     typedef default-policy-type {
       // this typedef retained for name compatibiity with default
       // import and export policy
       type enumeration {
         enum accept-route {
           description
             "Default policy to accept the route";
         }
         enum reject-route {
           description
             "Default policy to reject the route";
         }
       }
       description
         "Type used to specify route disposition in
          a policy chain";
     }

     typedef policy-result-type {
       type enumeration {
         enum accept-route {
           description "Policy accepts the route";
         }
         enum reject-route {
           description "Policy rejects the route";
         }
       }
       description
         "Type used to specify route disposition in
          a policy chain";
     }




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     typedef tag-type {
       type union {
         type uint32;
         type yang:hex-string;
       }
       description "Type for expressing route tags on a local system,
          including IS-IS and OSPF; may be expressed as either decimal
          or hexadecimal integer";
       reference
         "RFC 2178 - OSPF Version 2
          RFC 5130 - A Policy Control Mechanism in IS-IS Using
                     Administrative Tags";
     }

     typedef match-set-options-type {
       type enumeration {
         enum any {
           description "Match is true if given value matches any member
              of the defined set";
         }
         enum all {
           description "Match is true if given value matches all
              members of the defined set";
         }
         enum invert {
           description "Match is true if given value does not match any
              member of the defined set";
         }
       }
       default any;
       description
         "Options that govern the behavior of a match statement.  The
          default behavior is any, i.e., the given value matches any
          of the members of the defined set";
     }


     // grouping statements

     grouping prefix-set {
       description
         "Configuration data for prefix sets used in policy
          definitions.";

       leaf name {
         type string;
         description
           "Name of the prefix set -- this is used as a label to



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            reference the set in match conditions";
       }

       leaf mode {
         type enumeration {
           enum ipv4 {
             description
               "Prefix set contains IPv4 prefixes only";
           }
           enum ipv6 {
             description
               "Prefix set contains IPv6 prefixes only";
           }
           enum mixed {
             description
               "Prefix set contains mixed IPv4 and IPv6 prefixes";
           }
         }
         description
           "Indicates the mode of the prefix set, in terms of which
            address families (IPv4, IPv6, or both) are present.  The
            mode provides a hint, but the device must validate that all
            prefixes are of the indicated type, and is expected to
            reject the configuration if there is a discrepancy.  The
            MIXED mode may not be supported on devices that require
            prefix sets to be of only one address family.";
       }

     }

     grouping prefix-set-top {
       description
         "Top-level data definitions for a list of IPv4 or IPv6
          prefixes which are matched as part of a policy";

       container prefix-sets {
         description
           "Enclosing container ";

         list prefix-set {
           key "name";
           description
             "List of the defined prefix sets";

           uses prefix-set;

           uses prefix-top;
         }



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       }
     }

     grouping prefix {
       description
         "Configuration data for a prefix definition";

       leaf ip-prefix {
         type inet:ip-prefix;
         mandatory true;
         description
           "The prefix member in CIDR notation -- while the
            prefix may be either IPv4 or IPv6, most
            implementations require all members of the prefix set
            to be the same address family.  Mixing address types in
            the same prefix set is likely to cause an error.";
       }

       leaf masklength-lower {
         type uint8;
         description
           "Masklength range lower bound.";
       }
       leaf masklength-upper {
         type uint8 {
           range "1..128";
         }
         must "../masklength-upper >= ../masklength-lower" {
           error-message "The upper bound should not be less"
                       + "than lower bound.";
         }
         description
           "Masklength range upper bound.

            The combination of masklength-lower and masklength-upper
            define a range for the mask length, or single 'exact'
            length if masklength-lower and masklenght-upper are equal.

            Example: 10.3.192.0/21 through 10.3.192.0/24 would be
            expressed as prefix: 10.3.192.0/21,
                         masklength-lower=21,
                         masklength-upper=24

            Example: 10.3.192.0/21 (an exact match) would be
            expressed as prefix: 10.3.192.0/21,
                         masklength-lower=21,
                         masklength-upper=21";
       }



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     }

     grouping prefix-top {
       description
         "Top-level grouping for prefixes in a prefix list";

       container prefixes {
         description
           "Enclosing container for the list of prefixes in a policy
            prefix list";

         list prefix-list {
           key "ip-prefix masklength-lower masklength-upper";
           description
             "List of prefixes in the prefix set";

           uses prefix;
         }
       }
     }

     grouping neighbor-set {
       description
         "This grouping provides neighbor set definitions";

       leaf name {
         type string;
         description
             "Name of the neighbor set -- this is used as a label
              to reference the set in match conditions";
       }

       leaf-list address {
         type inet:ip-address;
         description
           "List of IP addresses in the neighbor set";
       }
     }

     grouping neighbor-set-top {
       description
         "Top-level data definition for a list of IPv4 or IPv6
          neighbors which can be matched in a routing policy";

       container neighbor-sets {
         description
           "Enclosing container for the list of neighbor set
            definitions";



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         list neighbor-set {
           key "name";
           description
             "List of defined neighbor sets for use in policies.";

           uses neighbor-set;
         }
       }
     }

     grouping tag-set {
       description
         "This grouping provides tag set definitions.";

       leaf name {
         type string;
         description
           "Name of the tag set -- this is used as a label to reference
            the set in match conditions";
       }

       leaf-list tag-value {
         type tag-type;
         description
           "Value of the tag set member";
       }
     }

     grouping tag-set-top {
       description
         "Top-level data definitions for a list of tags which can
          be matched in policies";

       container tag-sets {
         description
           "Enclosing container for the list of tag sets.";

         list tag-set {
           key "name";
           description
             "List of tag set definitions.";

           uses tag-set;

         }
       }
     }




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     grouping match-set-options-group {
       description
         "Grouping containing options relating to how a particular set
          should be matched";

       leaf match-set-options {
         type match-set-options-type;
         description
           "Optional parameter that governs the behavior of the
            match operation";
       }
     }

     grouping match-set-options-restricted-group {
       description
         "Grouping for a restricted set of match operation modifiers";

       leaf match-set-options {
         type match-set-options-type {
           enum any {
             description "Match is true if given value matches any
                member of the defined set";
           }
           enum invert {
             description "Match is true if given value does not match
                any member of the defined set";
           }
         }
         description
           "Optional parameter that governs the behavior of the
            match operation.  This leaf only supports matching on ANY
            member of the set or inverting the match.  Matching on ALL
            is not supported";
       }
     }



     grouping match-interface-condition {
       description
         "This grouping provides interface match condition";

       container match-interface {
         leaf interface {
           type leafref {
             path "/if:interfaces/if:interface/if:name";
           }
           description



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             "Reference to a base interface.  If a reference to a
              subinterface is required, this leaf must be specified
              to indicate the base interface.";
         }
         leaf subinterface {
           type leafref {
             path "/if:interfaces/if:interface/if-cmn:encapsulation"
                + "/if-l3-vlan:dot1q-vlan"
                + "/if-l3-vlan:outer-tag/if-l3-vlan:vlan-id";
           }
           description
             "Reference to a subinterface -- this requires the base
              interface to be specified using the interface leaf in
              this container.  If only a reference to a base interface
              is requuired, this leaf should not be set.";
         }

         description
           "Container for interface match conditions";
       }
     }

     grouping prefix-set-condition {
       description
         "This grouping provides prefix-set conditions";

       container match-prefix-set {
         leaf prefix-set {
           type leafref {
             path "../../../../../../../defined-sets/" +
               "prefix-sets/prefix-set/name";
           }
           description "References a defined prefix set";
         }
         uses match-set-options-restricted-group;

         description
           "Match a referenced prefix-set according to the logic
            defined in the match-set-options leaf";
       }
     }

     grouping neighbor-set-condition {
       description
         "This grouping provides neighbor-set conditions";

       container match-neighbor-set {
         leaf neighbor-set {



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           type leafref {
             path "../../../../../../../defined-sets/neighbor-sets/" +
             "neighbor-set/name";
             require-instance true;
           }
           description "References a defined neighbor set";
         }

         description
           "Match a referenced neighbor set according to the logic
            defined in the match-set-options-leaf";
       }
     }

     grouping tag-set-condition {
       description
         "This grouping provides tag-set conditions";

       container match-tag-set {
         leaf tag-set {
           type leafref {
             path "../../../../../../../defined-sets/tag-sets/tag-set" +
             "/name";
             require-instance true;
           }
           description "References a defined tag set";
         }
         uses match-set-options-restricted-group;

         description
           "Match a referenced tag set according to the logic defined
            in the match-options-set leaf";
       }
     }

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

       uses match-interface-condition;
       uses prefix-set-condition;
       uses neighbor-set-condition;
       uses tag-set-condition;

     }

     grouping policy-conditions {
       description



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         "Data for general policy conditions, i.e., those
          not related to match-sets";

         leaf call-policy {
           type leafref {
             path "../../../../../../" +
               "rt-pol:policy-definitions/" +
               "rt-pol:policy-definition/rt-pol:name";
             require-instance true;
           }
           description
             "Applies the statements from the specified policy
              definition and then returns control the current
              policy statement. Note that the called policy may
              itself call other policies (subject to
              implementation limitations). This is intended to
              provide a policy 'subroutine' capability.  The
              called policy should contain an explicit or a
              default route disposition that returns an
              effective true (accept-route) or false
              (reject-route), otherwise the behavior may be
              ambiguous and implementation dependent";
         }

         leaf source-protocol {
           type identityref {
             base rt:control-plane-protocol;
           }
           description
             "Condition to check the protocol / method used to install
              the route into the local routing table";
         }
     }

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

       container conditions {
         description
           "Condition statements for the current policy statement";

         uses policy-conditions;

         uses generic-conditions;
       }
     }




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     grouping policy-statements {
       description
         "Data for policy statements";

       leaf name {
         type string;
         description
           "Name of the policy statement";
       }
     }


     grouping policy-actions {
       description
         "Top-level grouping for policy actions";

       container actions {
         description
           "Top-level container for policy action statements";

         leaf policy-result {
           type policy-result-type;
           description
             "Select the final disposition for the route, either
              accept or reject.";
         }
         leaf set-metric {
           type uint16;
           description
             "Set a new metric for the route.";
         }
         leaf set-preference {
           type uint8;
           description
             "Set a new preference for the route.";
         }
       }
     }

     grouping policy-statements-top {
       description
         "Top-level grouping for the policy statements list";

       container statements {
         description
           "Enclosing container for policy statements";

         list statement {



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           key "name";
           ordered-by user;
           description
             "Policy statements group conditions and actions
              within a policy definition.  They are evaluated in
              the order specified (see the description of policy
              evaluation at the top of this module.";

           uses policy-statements;

           uses policy-conditions-top;
           uses policy-actions;
         }
       }
     }


     grouping policy-definitions {
       description
         "This grouping provides policy definitions";

       leaf name {
         type string;
         description
           "Name of the top-level policy definition -- this name
           is used in references to the current policy";
       }
     }

     grouping apply-policy-import {
       description
         "Grouping for applying import policies";

       leaf-list import-policy {
         type leafref {
           path "/rt-pol:routing-policy/rt-pol:policy-definitions/" +
             "rt-pol:policy-definition/rt-pol:name";
           require-instance true;
         }
         ordered-by user;
         description
           "List of policy names in sequence to be applied on
            receiving a routing update in the current context, e.g.,
            for the current peer group, neighbor, address family,
            etc.";
       }

       leaf default-import-policy {



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         type default-policy-type;
         default reject-route;
         description
           "Explicitly set a default policy if no policy definition
            in the import policy chain is satisfied.";
       }

     }

     grouping apply-policy-export {
       description
         "Grouping for applying export policies";

       leaf-list export-policy {
         type leafref {
           path "/rt-pol:routing-policy/rt-pol:policy-definitions/" +
             "rt-pol:policy-definition/rt-pol:name";
           require-instance true;
         }
         ordered-by user;
         description
           "List of policy names in sequence to be applied on
            sending a routing update in the current context, e.g.,
            for the current peer group, neighbor, address family,
            etc.";
       }

       leaf default-export-policy {
         type default-policy-type;
         default reject-route;
         description
           "Explicitly set a default policy if no policy definition
            in the export policy chain is satisfied.";
       }
     }


     grouping apply-policy {
       description
         "Configuration data for routing policies";

       uses apply-policy-import;
       uses apply-policy-export;

       container apply-policy-state {
         description
           "Operational state associated with routing policy";




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         //TODO: identify additional state data beyond the intended
         //policy configuration.
       }

     }


     grouping apply-policy-group {
       description
         "Top level container for routing policy applications. This
          grouping is intended to be used in routing models where
          needed.";

       container apply-policy {
         description
           "Anchor point for routing policies in the model.
            Import and export policies are with respect to the local
            routing table, i.e., export (send) and import (receive),
            depending on the context.";

         uses apply-policy;

       }
     }

     container routing-policy {
       description
         "Top-level container for all routing policy";

       container defined-sets {
         description
           "Predefined sets of attributes used in policy match
            statements";

         uses prefix-set-top;
         uses neighbor-set-top;
         uses tag-set-top;
       }

       container policy-definitions {
         description
           "Enclosing container for the list of top-level policy
            definitions";

         list policy-definition {
           key "name";
           description
             "List of top-level policy definitions, keyed by unique



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              name.  These policy definitions are expected to be
              referenced (by name) in policy chains specified in import
              or export configuration statements.";

           uses policy-definitions;

           uses policy-statements-top;
         }
       }
     }
   }
   <CODE ENDS>


10.  Policy examples

   Below we show an example of XML-encoded configuration data using the
   routing policy and BGP models to illustrate both how policies are
   defined, and also how they can be applied.  Note that the XML has
   been simplified for readability.

   <?yfile include="file:///tmp/routing-policy-example-draft.xml"?>


11.  References

11.1.  Normative 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-10
              (work in progress), January 2018.

   [RFC3688]  Mealling, M., "The IETF XML Registry", RFC 3688, January
              2004.

   [RFC4271]  Rekhter, Y., Li, T., and S. Hares, "A Border Gateway
              Protocol 4 (BGP-4)", RFC 4271, January 2006.

   [RFC6020]  Bjorklund, M., "YANG - A Data Modeling Language for the
              Network Configuration Protocol (NETCONF)", RFC 6020,
              October 2014.

   [RFC6991]  Schoenwaelder, J., "Common YANG Data Types", RFC 6991,
              July 2013.





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

11.2.  Informative references

   [I-D.ietf-idr-bgp-model]
              Patel, K., Jethanandani, M., and S. Hares, "BGP Model for
              Service Provider Networks", draft-ietf-idr-bgp-model-03
              (work in progress), May 2018.

Appendix A.  Acknowledgements

   The routing policy module defined in this draft is based on the
   OpenConfig route policy model.  The authors would like to thank to
   OpenConfig for their contributions, especially Rob Shakir, Kevin
   D'Souza, and Chris Chase.

   The authors are grateful for valuable contributions to this document
   and the associated models from: Ebben Aires, Luyuan Fang, Josh
   George, Acee Lindem, Stephane Litkowski, Ina Minei, Carl Moberg, Eric
   Osborne, Steve Padgett, Juergen Schoenwaelder, Jim Uttaro, and Russ
   White.

Appendix B.  Change summary

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

   Updated the model to use IETF modules and be NMDA compliant.

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

   Updated policy model with additional condition for matching
   interfaces.

B.3.  Changes between revisions draft-shaikh-rtgwg-policy-model and -00

   This revision updates the draft name to reflect adoption as a working
   document in the RTGWG.  Minor changes include updates to references
   and updated author contact information.

Authors' Addresses









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   Yingzhen Qu
   Huawei
   2330 Central Expressway
   Santa Clara  CA 95050
   USA

   Email: yingzhen.qu@huawei.com


   Jeff Tantsura
   Nuage Networks

   Email: jefftant.ietf@gmail.com


   Acee Lindem
   Cisco
   301 Mindenhall Way
   Cary, NC  27513
   US

   Email: acee@cisco.com


   Xufeng Liu
   Jabil
   8281 Greensboro Drive, Suite 200
   Mclean, VA  22102
   US

   Email: xufeng_liu@jabil.com


   Anees Shaikh
   Google
   1600 Amphitheatre Pkwy
   Mountain View, CA  94043
   US

   Email: aashaikh@google.com











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