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Versions: (draft-thomas-spring-sr-policy-yang) 00 01

SPRING Working Group                                        K. Raza, Ed.
Internet-Draft                                                 R. Sawaya
Intended status: Standards Track                           Cisco Systems
Expires: December 1, 2019
                                                              Z. Shunwan
                                                     Huawei Technologies

                                                                D. Voyer
                                                             Bell Canada

                                                              M. Durrani
                                                                 Equinix

                                                           S. Matsushima
                                                                SoftBank


                                                            May 30, 2019


               YANG Data Model for Segment Routing Policy
                draft-raza-spring-sr-policy-yang-00.txt


Abstract

   This document defines a YANG data model for Segment Routing (SR)
   Policy that can be used for configuring, instantiating, and managing
   SR policies.  The model is generic and apply equally to the MPLS and
   SRv6 instantiations of SR policies.

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 1, 2019.

Copyright Notice

   Copyright (c) 2019 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

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



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   (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
   2.  Specification of Requirements . . . . . . . . . . . . . . . .   3
   3.  Building Blocks . . . . . . . . . . . . . . . . . . . . . . .   3
   4.  YANG Model  . . . . . . . . . . . . . . . . . . . . . . . . .   4
     4.1.  Types and Definitions . . . . . . . . . . . . . . . . . .   4
     4.2.  SR Policy . . . . . . . . . . . . . . . . . . . . . . . .   5
       4.2.1.  Configuration . . . . . . . . . . . . . . . . . . . .   6
       4.2.2.  State . . . . . . . . . . . . . . . . . . . . . . . .  10
       4.2.3.  Notification  . . . . . . . . . . . . . . . . . . . .  12
   5.  Pending Items . . . . . . . . . . . . . . . . . . . . . . . .  13
   6.  YANG Specification  . . . . . . . . . . . . . . . . . . . . .  14
     6.1.  Types . . . . . . . . . . . . . . . . . . . . . . . . . .  14
     6.2.  SR Policy . . . . . . . . . . . . . . . . . . . . . . . .  21
   7.  Security Considerations . . . . . . . . . . . . . . . . . . .  41
   8.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  41
   9.  Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .  42
   10. References  . . . . . . . . . . . . . . . . . . . . . . . . .  42
     10.1.  Normative References . . . . . . . . . . . . . . . . . .  42
     10.2.  Informative References . . . . . . . . . . . . . . . . .  43
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  43

1.  Introduction

   The Network Configuration Protocol (NETCONF) [RFC6241] defines
   mechanisms to manage network devices.  YANG [RFC6020] is a modular
   language that represents data structures in an XML tree format, and
   is used as a data modeling language for the NETCONF.

   Segment Routing (SR), as defined in [RFC8402], allows a headend node
   to steer a packet flow along any topological path and/or service
   chain.  The headend node is said to steer a flow into a Segment
   Routing Policy (SR Policy).  An SR policy is a framework
   [I-D.ietf-spring-segment-routing-policy] that enables instantiation
   of an ordered list of segments on a node for implementing a policy.

   This document introduces a YANG data model for SR policy framework
   for instantiating, configuring and managing SR policies along with
   its attributes.  It is also expected that other companion models,



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   such as BGP SR Policy [I-D.ietf-idr-segment-routing-te-policy], will
   be defined and/or augmented accordingly in their respective areas.

   This model defines the following constructs for managing an SR
   policy:

   o  Configuration

   o  Operational State

   o  Notifications

   o  Executables (Actions)

   This document expects and requires the reader to be well familiar
   with the concepts and constructs of an SR policy
   [I-D.ietf-spring-segment-routing-policy] as well as the YANG modeling
   language and its presentation [RFC6020].

2.  Specification of Requirements

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in BCP 14 [RFC2119]
   [RFC8174] when, and only when, they appear in all capitals, as shown
   here.

3.  Building Blocks

   Before looking into the YANG model for SR policy, it is important to
   recall and highlight the major building blocks and constructs that
   constitute and contribute to an SR policy, as described in
   [I-D.ietf-spring-segment-routing-policy].

   o  policy: specifies constructs to allow a headend node to setup SR
      path(s) as an ordered list of segments for a given color and
      endpoint.  The endpoint and the color are used to automate the
      steering of service or transport routes on an SR Policy.  For a
      given headend, the key for an SR policy is (color, endpoint) where
      endpoint is an IP address that could be also NULL.

   o  candidate-path: is the unit for signalling of an SR Policy to a
      headend via protocols (such as PCEP, BGP, CLI etc.).  A candidate
      path is either dynamic or explicit type, where an explicit
      candidate path is associated with one or more segment-lists and
      dynamic candidate path expresses optimization objectives and set
      of constraints.  An SR Policy is associated with one or more
      candidate paths and the preference of the candidate path is used



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      to select the best candidate path for an SR Policy.  A candidate
      path is valid if it is usable (e.g. when its constituents SIDs are
      reachable).  An "active" candidate path is the selected path (for
      forwarding) that is valid and determined to be the best path of
      the SR Policy.

   o  segment-list: specifies ordered list of segments to traverse,
      where a segment can be specified in various forms (refer section 4
      of [I-D.ietf-spring-segment-routing-policy]).  The list is sorted
      by the index of the segment.  A segment-list is used and referred
      by an explicit type of candidate-path.

   o  binding-sid: An SR policy is associated with a BSID to provide
      benefits of scaling, network opacity and service independence.

4.  YANG Model

   The modeling in this document complies with the Network Management
   Datastore Architecture (NMDA) [RFC8342].  The operational state data
   is combined with the associated configuration data in the same
   hierarchy [RFC8407].  When protocol states are retrieved from the
   NMDA operational state datastore, the returned states cover all
   "config true" (rw) and "config false" (ro) nodes defined in the
   schema.

   For SR policy YANG specification, this document defines following new
   YANG modules:

   +----------------------+--------------------------------------------+
   | Module Name          | Purpose                                    |
   +----------------------+--------------------------------------------+
   | ietf-sr-policy-types | defines common and basic types related to  |
   |                      | an SR policy and related constructs        |
   |                      |                                            |
   | ietf-sr-policy       | defines the model for SR policy            |
   |                      | instantiation, configuration, and          |
   |                      | management                                 |
   +----------------------+--------------------------------------------+

4.1.  Types and Definitions

   SR policy common types and definitions are defined in the new module
   "ietf-sr-policy-types".  The main types defined in this module
   include:

   o  dataplane-type: A union to specify MPLS or IPv6 as the dataplane
      type for SR.




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   o  sid-value-type: A Union to specify SID value for SR-MPLS or SRv6
      type.

   o  binding-sid-alloc-mode: Enum to define explicit or dynamic alloc
      mode types for a BSID.

   o  protocol-origin-type: Enum to specify protocol origin (e.g.  PCEP)
      for an SR policy.

   o  explicit-binding-sid-rule-type: Enum to specify BSID alloc
      enforcement/rule when doing explicit alloc request.

   o  binding-sid-oper-state: An Enum representing various operational
      states for a BSID.

   o  policy-admin-state: An Enum for admin state of an SR policy.

   o  policy-oper-state: An Enum for operational state of an SR policy.

   o  segment-type: An Enum that defines various types for a "segment"
      of a Segment list.

   o  candidate-path-non-selection-reason: The base identity along with
      its children to specify reason for not selecting a candidate path
      as the best/active path.

   o  policy-down-reason: The base identity along with its children to
      specify reason for a policy becoming (or remaining) operationally
      down.

   o  binding-sid-unavailable-reason: The base identity along with its
      children to specify reason for a BSID's unavailability.

   The associated YANG specification for this module is captured in
   Section 6.1.

4.2.  SR Policy

   The base SR policy model is captured in ietf-sr-policy module.  This
   base module augments "/rt:routing" and specifies the configuration,
   operational state, executables/rpcs, and notification events required
   to manage SR policies.

   The associated YANG specification for this module is captured in
   Section 6.2.






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4.2.1.  Configuration

   In terms of configuration hierarchy, SR policy configuration tree has
   following two main areas:

   o  policy-attributes: container that defines common constructs that
      could be used across policies.  An example of such a construct is
      segment-lists definition.  In future revision of this document, it
      is expected that this container will have more constructs defined.

   o  policies: container that defines list of policies with their
      attributes such as BSID, candidate-paths etc.

   Following diagram depicts high level yang organization and hierarchy
   for an SR policy specification:




































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         segment-routing
            sr-policy
               + policy-attributes
               |   + segment-lists
               |   |    segment-list* [name]
               |   |        segments
               |   |            segment* [index]
               |   |                ...
               |   + explicit-binding-sid-rules
               |        ...
               |
               + policies
                    policy* [color endpoint]
                       + ...
                       |
                       + binding-sid
                       | ...
                       |
                       + candidate-paths
                           candidate-path* [protocol origin discrim]
                               + ...
                               |
                               + type
                                   + dynamic
                                   |   ...
                                   |
                                   + explicit
                                       segment-lists
                                            segment-list* [ref]
                                                ...

                      Figure 1: SR Policy - Hierarchy

   Using the building blocks described in Section 3, following is the
   complete graphical representation of the data model for SR policy
   configuration:



module: ietf-sr-policy
  augment /rt:routing:
    +--rw segment-routing
       +--rw sr-policy
          +--rw policy-attributes
          |  +--rw segment-lists
          |  |  +--rw segment-list* [name]
          |  |     +--rw name        string
          |  |     +--rw segments



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          |  |        +--rw segment* [index]
          |  |           +--rw index            uint32
          |  |           +--rw type?            sr-policy-types:segment-type
          |  |           +--rw segment-types
          |  |           |  +--rw segment-type-1
          |  |           |  |  +--rw sid-value?   rt-types:mpls-label
          |  |           |  +--rw segment-type-2
          |  |           |  |  +--rw sid-value?   srv6-types:srv6-sid
          |  |           |  +--rw segment-type-3
          |  |           |  |  +--rw ipv4-address?   inet:ipv4-address
          |  |           |  |  +--rw algorithm?    uint8
          |  |           |  +--rw segment-type-4
          |  |           |  |  +--rw ipv4-address?   inet:ipv6-address
          |  |           |  |  +--rw algorithm?    uint8
          |  |           |  +--rw segment-type-5
          |  |           |  |  +--rw ipv4-address?             inet:ipv4-address
          |  |           |  |  +--rw interface-identifier?   uint32
          |  |           |  +--rw segment-type-6
          |  |           |  |  +--rw local-ipv4-address?    inet:ipv4-address
          |  |           |  |  +--rw remote-ipv4-address?   inet:ipv4-address
          |  |           |  +--rw segment-type-7
          |  |           |  |  +--rw local-ipv6-address?              inet:ipv6-address
          |  |           |  |  +--rw local-interface-identifier?    uint32
          |  |           |  |  +--rw remote-ipv6-address?             inet:ipv6-address
          |  |           |  |  +--rw remote-interface-identifier?   uint32
          |  |           |  +--rw segment-type-8
          |  |           |  |  +--rw local-ipv6-address?    inet:ipv6-address
          |  |           |  |  +--rw remote-ipv6-address?   inet:ipv6-address
          |  |           |  +--rw segment-type-9
          |  |           |  |  +--rw ipv6-address?   inet:ipv6-address
          |  |           |  |  +--rw algorithm?    uint8
          |  |           |  +--rw segment-type-10
          |  |           |  |  +--rw local-ipv6-address?              inet:ipv6-address
          |  |           |  |  +--rw local-interface-identifier?    uint32
          |  |           |  |  +--rw remote-ipv6-address?             inet:ipv6-address
          |  |           |  |  +--rw remote-interface-identifier?   uint32
          |  |           |  +--rw segment-type-11
          |  |           |     +--rw local-ipv6-address?    inet:ipv6-address
          |  |           |     +--rw remote-ipv6-address?   inet:ipv6-address
          |  |           +--rw validate?        boolean
          |  +--rw explicit-binding-sid-rules* [index]
          |     +--rw index    uint32
          |     +--rw rule?    sr-policy-types:explicit-binding-sid-rule-type
          +--rw policies
             +--rw policy* [color endpoint]
                +--rw color               uint32
                +--rw endpoint            inet:ip-address
                +--rw name?               string



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                +--rw description?        string
                +--rw admin-state?        sr-policy-types:policy-admin-state
                +--rw priority?           uint8
                +--rw binding-sid
                |  +--rw dataplane?       sr-policy-types:dataplane-type
                |  +--rw value?           sr-policy-types:sid-value-type
                +--rw candidate-paths
                   +--rw candidate-path* [protocol-origin originator discriminator]
                      +--rw protocol-origin             sr-policy-types:protocol-origin-type
                      +--rw originator                  string
                      +--rw discriminator               uint32
                      +--rw name?                       string
                      +--rw preference?                 uint32
                      +--rw description?                string
                      +--rw binding-sid {capability-candidate-path-binding-sid}?
                      |  +--rw dataplane?   sr-policy-types:dataplane-type
                      |  +--rw value?       sr-policy-types:sid-value-type
                      +--rw (type)?
                         +--:(explicit)
                         |  +--rw segment-lists
                         |     +--rw segment-list* [name-ref]
                         |        +--rw name-ref            -> .. segment-list/name
                         |        +--rw weight?             uint32
                         +--:(dynamic)
                            +--rw sid-dataplane-type?   sr-policy-types:dataplane-type

                     Figure 2: SR Policy - Config Tree

   Please take note of the following important points in the above
   configuration model:

   o  This model supports both MPLS and SRv6 dataplane for SR -- i.e.
      items like segments and BSID can be defined as MPLS label or SRv6
      SIDs.

   o  Specification of a segment supports all the types defined in SR
      policy base specification document

   o  The above model supports explicit BSID specification on SR policy
      level as the main mode of specification.  The model also allows
      explicit BSID per candidate-path as an if-feature capability that
      is optional for implementations

   o  The above model will be extended in future revisions of this
      document to enhance items like attribute and control related to
      dynamic type of segment-list, candidate-path, and traffic steering
      etc.




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4.2.2.  State

   As per NMDA model, the state related to configuration items specified
   in earlier Section 4.2.1 can be retrieved from the same tree.  This
   section defines the other operational state items related to SR
   policy.

   In addition to configured state, the operational state corresponding
   to the SR policy includes:

   o  policy operational state

   o  policy up/down timestamps

   o  policy BSID info such as alloc mode, actual value in-use,
      operational state, and forwarding stats

   o  Per candidate-path info such as:

      *  Whether candidate-path is the best candidate-path

      *  In case of non-best, the reason for such non-selection

      *  Type of candidate-path - explicit or dynamic

      *  Per segment-list information - such as validity of the segment-
         list, as well as forwarding state for a valid segment-list.
         The forwarding state is represented in terms of per forwarding
         path info that includes nexthop address, outgoing interface,
         protection information, and encapsulation (label stack or SRv6
         SID stack) etc.

   Following is a simplified graphical representation of the data model
   for the SR policy operational state:


module: ietf-sr-policy
  augment /rt:routing:
    +--rw segment-routing
       +--rw sr-policy
          +--rw policies
             +--rw policy* [color endpoint]
                +--rw color               uint32
                +--rw endpoint            inet:ip-address
                +--ro oper-state?         sr-policy-types:policy-oper-state
                +--ro transition-count?   uint32
                +--ro up-time?            yang:date-and-time
                +--ro down-time?          yang:date-and-time



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                +--rw binding-sid
                |  +--ro alloc-mode?      sr-policy-types:binding-sid-alloc-mode
                |  +--ro allocated-sid?   sr-policy-types:sid-value-type
                |  +--ro oper-state?      sr-policy-types:binding-sid-oper-state
                +--ro counters
                |  +--ro pkts?     yang:counter64
                |  +--ro octets?   yang:counter64
                +--rw candidate-paths
                   +--rw candidate-path* [protocol-origin originator discriminator]
                      +--rw protocol-origin             sr-policy-types:protocol-origin-type
                      +--rw originator                  string
                      +--rw discriminator               uint32
                      +--ro is-best-candidate-path?     boolean
                      +--ro non-selection-reason?       identityref
                      +--rw (type)?
                         +--:(explicit)
                         |  +--rw segment-lists
                         |     +--rw segment-list* [name-ref]
                         |        +--rw name-ref            -> .. segment-list/name
                         |        +--ro is-valid?           boolean
                         |        +--ro forwarding-paths
                         |           +--ro forwarding-path* [path-id]
                         |              +--ro path-id               uint8
                         |              +--ro next-hop-address?     inet:ip-address
                         |              +--ro next-hop-table-id?    uint32
                         |              +--ro outgoing-interface?   if:interface-ref
                         |              +--ro outgoing-sids
                         |              |  +--ro (dataplanetype)?
                         |              |     +--:(mpls)
                         |              |     |  +--ro labels* [label]
                         |              |     |     +--ro label    rt-types:mpls-label
                         |              |     +--:(srv6)
                         |              |        +--ro sids* [sid]
                         |              |           +--ro sid    srv6-types:srv6-sid
                         |              +--ro is-protected?         boolean
                         |              +--ro is-pure-backup?       boolean
                         |              +--ro backup-path-id?       uint8
                         |              +--ro weight?               uint32
                         +--:(dynamic)
                            +--ro is-valid?             boolean
                            +--ro forwarding-paths
                               +--ro forwarding-path* [path-id]
                                  +--ro path-id               uint8
                                  +--ro next-hop-address?     inet:ip-address
                                  +--ro next-hop-table-id?    uint32
                                  +--ro outgoing-interface?   if:interface-ref
                                  +--ro outgoing-sids
                                  |  +--ro (dataplanetype)?



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                                  |     +--:(mpls)
                                  |     |  +--ro labels* [label]
                                  |     |     +--ro label    rt-types:mpls-label
                                  |     +--:(srv6)
                                  |        +--ro sids* [sid]
                                  |           +--ro sid    srv6-types:srv6-sid
                                  +--ro is-protected?         boolean
                                  +--ro is-pure-backup?       boolean
                                  +--ro backup-path-id?       uint8
                                  +--ro weight?               uint32


                     Figure 3: SR Policy - State Tree

4.2.3.  Notification

   This model defines a list of notifications to inform an operator of
   important events detected regarding an SR policy.  These events
   include events related to:

   o  policy status: policy operational state changes

   o  Candidate-path active status and changes

   o  Explicit Binding SID collision/unavailability events

   Following is a simplified graphical representation of the data model
   for SR policy notifications:























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module: ietf-sr-policy
  notifications:
    +---n sr-policy-oper-state-change-event
    |  +--ro policy-name-ref?         -> .. policy/name
    |  +--ro policy-color-ref?        -> .. policy/color
    |  +--ro policy-endpoint-ref?     -> .. policy/endpoint
    |  +--ro policy-new-oper-state?   sr-policy-types:policy-oper-state
    |  +--ro policy-down-reason?      identityref
    +---n sr-policy-candidate-path-change-event
    |  +--ro policy-name-ref?       -> .. policy/name
    |  +--ro policy-color-ref?      -> .. policy/color
    |  +--ro policy-endpoint-ref?   -> .. policy/endpoint
    |  +--ro existing-preference?   uint32
    |  +--ro new-preference?        uint32
    +---n sr-policy-binding-sid-unavailable-event
    |  +--ro policy-name-ref?                -> .. policy/name
    |  +--ro policy-color-ref?               -> .. policy/color
    |  +--ro policy-endpoint-ref?            -> .. policy/endpoint
    |  +--ro policy-binding-sid-value-ref?   -> .. policy/binding-sid/value
    |  +--ro reason?                         identityref
    +---n sr-policy-candidate-path-binding-sid-mismatch-event
       +--ro policy-color-ref?                                    -> .. policy/color
       +--ro policy-endpoint-ref?                                 -> .. policy/endpoint
       +--ro existing-candidate-path-protocol-origin-ref?         -> .. candidate-path/protocol-origin
       +--ro existing-candidate-path-preference-ref?              -> .. candidate-path/preference
       +--ro existing-candidate-path-binding-sid-dataplane-ref?   -> .. candidate-path/binding-sid/dataplane
       +--ro existing-candidate-path-binding-sid-value-ref?       -> .. candidate-path/binding-sid/value
       +--ro conflicting-candidate-path-protocol-origin?          uint8
       +--ro conflicting-candidate-path-preference?               uint32
       +--ro conflicting-candidate-path-binding-sid-dataplane?    sr-policy-types:dataplane-type
       +--ro conflicting-candidate-path-binding-sid-value?        sr-policy-types:sid-value-type


                  Figure 4: SR Policy - Notification Tree

5.  Pending Items

   Following are the items that will be addressed in future revisions of
   this document:

   o  Configuration and Specification of:

      *  Link Attributes

      *  Dynamic type of candidate-path (optimization objectives and
         constraints)

      *  Traffic steering over SR policy



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      *  ODN templates

      *  Spray policy

   o  Executables (RPC actions)

6.  YANG Specification

   Following are actual YANG definition for the modules defined earlier
   in the document.

6.1.  Types


<CODE BEGINS> file "ietf-sr-policy-types@2018-07-01.yang" -->

module ietf-sr-policy-types {
  namespace "urn:ietf:params:xml:ns:yang:ietf-sr-policy";

  prefix "ietf-sr-policy-types";

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

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

  import ietf-srv6-types {
    prefix "srv6-types";
  }

  organization "IETF SPRING Working Group";

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

       Editor:   Kamran Raza
                 <mailto:skraza@cisco.com>

       Editor:   Zhuang Shunwan
                 <mailto:zhuangshunwa@huawei.com>

       Editor:   Daniel Voyer
                 <mailto:daniel.voyer@bell.ca>




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       Editor:   Muhammad Durrani
                 <mailto:mdurrani@equinix.com>

       Editor:   Satoru Matsushima
                 <mailto:satoru.matsushima@g.softbank.co.jp>
       ";

  description
    "This YANG module defines the essential types for the management
     of SR policy module.

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

     Redistribution and use in source and binary forms, with or
     without modification, is permitted pursuant to, and subject
     to the license terms contained in, the Simplified BSD License
     set forth in Section 4.c of the IETF Trust's Legal Provisions
     Relating to IETF Documents
     (http://trustee.ietf.org/license-info).";

  revision "2018-07-01" {
    description
      "Initial version";
    reference
      "draft-ietf-spring-segment-routing-policy";
  }

  /* Identities */
  identity candidate-path-not-selected-reason {
    description
      "Base identity for which reasons for not selecting
      candidate path are derived from";
  }
  identity candidate-path-not-selected-not-best {
    base candidate-path-not-selected-reason;
    description
      "Higher preference path exists";
  }
  identity candidate-path-not-selected-no-valid-segment-list {
    base candidate-path-not-selected-reason;
    description
      "Candidate path has no valid segment list(s)";
  }
  identity candidate-path-not-selected-empty-segment-list {
    base candidate-path-not-selected-reason;
    description
      "Candidate path has empty segment list(s)";



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  }
  identity candidate-path-not-selected-invalid-binding-sid {
    base candidate-path-not-selected-reason;
    description
      "Candidate path has invalid binding SID";
  }

  identity policy-down-reason {
   description
      "Base identity for the reasons why SR policy is operationally down";
  }
  identity policy-down-reason-admin-down {
    base policy-down-reason;
    description "Policy is administrately down";
  }
  identity policy-down-reason-no-source-address {
    base policy-down-reason;
    description "Policy has no source address";
  }
  identity policy-down-reason-no-endpoint {
    base policy-down-reason;
    description "Policy has no end-point";
  }
  identity policy-down-reason-no-candidate-path {
    base policy-down-reason;
    description "Policy has no candidate path";
  }
  identity policy-down-reason-no-valid-candidate-path {
    base policy-down-reason;
    description "Policy has no valid candidate path";
  }
  identity policy-down-reason-candidate-path-invalid-segment-list {
    base policy-down-reason;
    description "Policy's candidate path has invalid segment list";
  }
  identity policy-down-reason-policy-unconfigured {
    base policy-down-reason;
    description "Policy is unconfigured";
  }
  identity policy-down-reason-policy-color-endpoint-updated {
    base policy-down-reason;
    description "Policy's color and end-point are updated";
  }
  identity policy-down-reason-local-label-setup-failed {
    base policy-down-reason;
    description "Policy's local label setup (allocation/rewrite) failed";
  }
  identity policy-down-reason-forwarding-rewrite-failed {



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    base policy-down-reason;
    description "Policy's forwarding rewrite installation failed";
  }
  identity policy-down-reason-internal-error {
    base policy-down-reason;
    description "Infra related internal error";
  }

  identity binding-sid-unavailable-reason {
    description
      "Base identity for binding sid unavailable reason types";
  }
  identity binding-sid-allocation-error {
    base binding-sid-unavailable-reason;
    description "SID allocator returned an error";
  }
  identity binding-sid-already-exists {
    base binding-sid-unavailable-reason;
    description "Binding sid already exists/allocated";
  }
  identity binding-sid-internal-error {
    base binding-sid-unavailable-reason;
    description "Internal error with binding sid allocation";
  }
  identity binding-sid-color-endpoint-conflict {
    base binding-sid-unavailable-reason;
    description "Binding sid already allocated by another sr-policy with different color/endpoint";
  }
  identity binding-sid-rewrite-error {
    base binding-sid-unavailable-reason;
    description "Binding sid forwarding rewrite error";
  }
  identity binding-sid-outside-srlb-range {
    base binding-sid-unavailable-reason;
    description "Binding sid outside SRLB range";
  }

  /* Typdefs */
  typedef sid-value-type {
    type union {
      type rt-types:mpls-label;
      type srv6-types:srv6-sid;
    }
    description "The SID value type";
  }

  typedef binding-sid-oper-state {
    type enumeration {



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      enum ALLOC-PENDING {
        value 1;
        description "SID allocation pending for Binding SID";
      }
      enum PROGRAMMED {
        value 3;
        description "Binding SID is programmed in forwarding";
      }
      enum CONFLICT {
        value 4;
        description "Binding SID is in-conflict state with
        regards to SID allocation. This also means that SID
        allocation is pending";
      }
    }
    description
      "Binding SID operational state type";
  }

  typedef policy-admin-state {
    type enumeration {
      enum UP {
        value 1;
        description "SR policy is administratively up";
      }
      enum DOWN {
        value 2;
        description "SR policy is administratively down";
      }
    }
    description "SR policy admin state";
  }

  typedef policy-oper-state {
    type enumeration {
      enum UP {
        value 1;
        description "SR policy is operationally up";
      }
      enum DOWN {
        value 2;
        description "SR policy is operationally down";
      }
    }
    description "SR policy oper state";
  }

  typedef segment-type {



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    type enumeration {
      enum segment-type-1 {
        value 1;
        description "SR-MPLS Label";
      }
      enum segment-type-2 {
        value 2;
        description "SRv6 SID";
      }
      enum segment-type-3 {
        value 3;
        description "IPv4 Prefix with optional SR Algorithm";
      }
      enum segment-type-4 {
        value 4;
        description "IPv6 Global Prefix with optional SR Algorithm for SR-MPLS";
      }
      enum segment-type-5 {
        value 5;
        description "IPv4 Prefix with Local Interface ID";
      }
      enum segment-type-6 {
        value 6;
        description "IPv4 Addresses for link endpoints as Local, Remote pair";
      }
      enum segment-type-7 {
        value 7;
        description "IPv6 Prefix and Interface ID for link endpoints as Local,
           Remote pair for SR-MPLS";
      }
      enum segment-type-8 {
        value 8;
        description "IPv6 Addresses for link endpoints as Local, Remote pair for
           SR-MPLS";
      }
      enum segment-type-9 {
        value 9;
        description "IPv6 Global Prefix with optional SR Algorithm for SRv6";
      }
      enum segment-type-10 {
        value 10;
        description "IPv6 Prefix and Interface ID for link endpoints as Local,
           Remote pair for SRv6";
      }
      enum segment-type-11 {
        value 11;
        description "IPv6 Addresses for link endpoints as Local, Remote pair for
           SRv6";



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      }
    }
    description "SR segment type";
  }

  typedef dataplane-type {
    type enumeration {
      enum mpls {
        value 1;
        description "Segment-routing MPLS";
      }
      enum srv6 {
        value 2;
        description "Segment-routing v6";
      }
    }
    description "Dataplane type of the segments";
  }

  typedef binding-sid-alloc-mode {
    type enumeration {
      enum explicit {
        value 1;
        description "Explicitly specified BSID";
      }
      enum dynamic {
        value 2;
        description "Dynamically allocated BSID";
      }
    }
    description "binding SID allocation mode";
  }

  typedef protocol-origin-type {
    type enumeration {
      enum pcep {
        value 10;
        description "PCEP used as signalling mechanism for the candidate path";
      }
      enum bgp {
        value 20;
        description "BGP used as signalling mechanism for the candidate path";
      }
      enum local {
        value 30;
        description "CLI, Yang model via Netconf, gRPC, etc used for candidate path instantiation";
      }
    }



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    description "Originating protocol type";
  }

  typedef explicit-binding-sid-rule-type {
    type enumeration {
      enum enforce-srlb {
        value 1;
        description
            "Explicit Binding SID is enforced with no
             fallback if label does not fall in SRLB or
             if no SRLB is configured";
      }
      enum fallback-dynamic {
        value 2;
        description
            "Explicit Binding SID falls back to dynamic in
            case explicit label is not available.";
      }
    }
    description "Explicit binding sid rule types";
  }
}

<CODE ENDS>


                    Figure 5: ietf-sr-policy-types.yang

6.2.  SR Policy



<CODE BEGINS> file "ietf-sr-policy@2018-07-01.yang" -->

module ietf-sr-policy {

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

  prefix "ietf-sr-policy";

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

  import ietf-interfaces {
    prefix if;
  }




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  import ietf-routing {
    prefix "rt";
  }

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

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

  import ietf-srv6-types {
    prefix "srv6-types";
  }

  import ietf-sr-policy-types {
    prefix "sr-policy-types";
  }

  organization "IETF SPRING Working Group";

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

       Editor:   Kamran Raza
                 <mailto:skraza@cisco.com>

       Editor:   Zhuang Shunwan
                 <mailto:zhuangshunwa@huawei.com>

       Editor:   Daniel Voyer
                 <mailto:daniel.voyer@bell.ca>


       Editor:   Muhammad Durrani
                 <mailto:mdurrani@equinix.com>

       Editor:   Satoru Matsushima
                 <mailto:satoru.matsushima@g.softbank.co.jp>
       ";

  description
    "This module contains a collection of YANG definitions
     for SR policy module.

     Copyright (c) 2018 IETF Trust and the persons identified as



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     authors of the code.  All rights reserved.

     Redistribution and use in source and binary forms, with or
     without modification, is permitted pursuant to, and subject
     to the license terms contained in, the Simplified BSD License
     set forth in Section 4.c of the IETF Trust's Legal Provisions
     Relating to IETF Documents
     (http://trustee.ietf.org/license-info).";

  revision "2018-07-01" {
    description
      "Initial version";
    reference
      "draft-ietf-spring-segment-routing-policy";
  }

  grouping segment_config {
    description "Segment properties grouping";
    leaf index {
      type uint32;
      description "Segment index";
    }
    leaf type {
      type sr-policy-types:segment-type;
      description "Segment type";
    }
    container segment-types {
      description "Types of segments";
      container segment-type-1 {
        description
           "Segment declared by MPLS label";
        leaf sid-value {
           type rt-types:mpls-label;
           description "MPLS label value";
        }
      }
      container segment-type-2 {
        description
           "Segment declared by SRv6 SID value";
        leaf sid-value {
           type srv6-types:srv6-sid;
           description "SRv6 SID value";
        }
      }
      container segment-type-3 {
        description
           "Segment declared by IPv4 Prefix with optional SR Algorithm";
        leaf ipv4-address {



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          type inet:ipv4-address;
          description "Segment IPv4 address";
        }
        leaf algorithm {
          type uint8;
          description "Prefix SID algorithm identifier";
        }
      }
      container segment-type-4 {
        description
           "Segment declared by IPv6 Global Prefix with optional
            SR Algorithm for SR-MPLS";
        leaf ipv6-address {
          type inet:ipv6-address;
          description "Segment IPv6 address";
        }
        leaf algorithm {
          type uint8;
          description "Prefix SID algorithm identifier";
        }
      }
      container segment-type-5 {
        description
           "Segment declared by IPv4 Prefix with Local Interface ID";
        leaf ipv4-address {
          type inet:ipv4-address;
          description "Node IPv4 address";
        }
        leaf interface-identifier {
          type uint32;
          description "local interface identifier";
        }
      }
      container segment-type-6 {
        description
           "Segment declared by IPv4 Addresses for link endpoints
            as Local, Remote pair";
        leaf local-ipv4-address {
          type inet:ipv4-address;
          description "Segment local IPv4 adjacency address";
        }
        leaf remote-ipv4-address {
          type inet:ipv4-address;
          description "Segment remote IPv4 adjacency address";
        }
      }
      container segment-type-7 {
        description



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           "Segment declared by IPv6 Prefix and Interface ID for
           link endpoints as Local, Remote pair for SR-MPLS";
        leaf local-ipv6-address {
          type inet:ipv6-address;
          description "Local link IPv6 address";
        }
        leaf local-interface-identifier {
          type uint32;
          description "Local interface identifier";
        }
        leaf remote-ipv6-address {
          type inet:ipv6-address;
          description "Remote link IPv6 address";
        }
        leaf remote-interface-identifier {
          type uint32;
          description "Remote interface identifier";
        }
      }
      container segment-type-8 {
        description
           "Segment declared by IPv6 Addresses for link endpoints as
           Local, Remote pair for SR-MPLS";
        leaf local-ipv6-address {
          type inet:ipv6-address;
          description "Segment local IPv6 adjacency address";
        }
        leaf remote-ipv6-address {
          type inet:ipv6-address;
          description "Segment remote IPv6 adjacency address";
        }
      }
      container segment-type-9 {
        description
          "Segment declared by IPv6 Global Prefix with optional
           SR Algorithm for SRv6";
        leaf ipv6-address {
          type inet:ipv6-address;
          description "Segment IPv6 prefix";
        }
        leaf algorithm {
          type uint8;
          description "Prefix SID algorithm identifier";
        }
      }
      container segment-type-10 {
        description
           "Segment declared by IPv6 Prefix and Interface ID for



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           link endpoints as Local, Remote pair for SRv6";
        leaf local-ipv6-address {
          type inet:ipv6-address;
          description "Local link IPv6 address";
        }
        leaf local-interface-identifier {
          type uint32;
          description "Local interface identifier";
        }
        leaf remote-ipv6-address {
          type inet:ipv6-address;
          description "Remote link IPv6 address";
        }
        leaf remote-interface-identifier {
          type uint32;
          description "Remote interface identifier";
        }
      }
      container segment-type-11 {
        description
           "Segment declared by IPv6 Addresses for link endpoints as
            Local, Remote pair for SRv6";
          leaf local-ipv6-address {
            type inet:ipv6-address;
            description "Segment local IPv6 adjacency address";
          }
          leaf remote-ipv6-address {
            type inet:ipv6-address;
            description "Segment remote IPv6 adjacency address";
          }
      }
    }
    leaf validate {
      type boolean;
      default 'false';
      description "Indicates whether the segment should be validated. The default
                   applies to all segments other than the first segment. For the
                   first segment, validation is always done.";
    }
  }

  grouping segment-properties {
    description
      "SR segment properties grouping";
    uses segment_config;
  }

  grouping policy-attributes {



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    description
      "Grouping containing attributes applicable to all SR policies";

    container policy-attributes {
      description
         "Attributes applicable to all SR policies";

      uses segment-lists;

      uses explicit-binding-sid-rules;
    }
  }

  grouping segment-lists {
    description
      "Segment lists grouping";
    container segment-lists {
      description "Segment-lists properties";

      list segment-list {
        key "name";
        description "Segment-list properties";
        leaf name {
          type string;
          description "Segment-list name";
        }
        container segments {
          description
            "Segments for given segment list";

          list segment {
            key "index";
            description "Configure Segment/hop at the index";
            uses segment-properties;
          }
        }
      }
    }
  }

  grouping binding-sid_config {
    description
      "Binding SID configuration properties grouping";
      leaf dataplane {
        type sr-policy-types:dataplane-type;
        description "Binding SID dataplane type";
      }
      leaf value {



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        type sr-policy-types:sid-value-type;
        description "Binding SID value";
      }
  }

  grouping forwarding-counters {
    description
      "Grouping for counters";
    container counters {
      config false;
      description
         "Counters containing stats related to forwarding";

      leaf pkts {
        type yang:counter64;
        description "Number of packets forwarded";
      }
      leaf octets {
        type yang:counter64;
        units "byte";
        description "Number of bytes forwarded";
      }
    }
  }

  grouping binding-sid_state {
    description
      "Binding SID state properties grouping";
    leaf alloc-mode {
      type sr-policy-types:binding-sid-alloc-mode;
      config false;
      description "Binding SID type";
    }
    leaf allocated-sid {
      type sr-policy-types:sid-value-type;
      config false;
      description "Allocated SID value for the Binding SID";
    }
    leaf oper-state {
      type sr-policy-types:binding-sid-oper-state;
      config false;
      description
        "Binding SID operational state";
    }
  }

  grouping binding-sid-properties {
    description



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      "Binding SID properties grouping";
    container binding-sid {
      description "Binding Segment ID";
      uses binding-sid_config;
      uses binding-sid_state;
    }
  }

  grouping mpls-label-stack {
    description
      "Grouping for MPLS label stack";

    list labels {
      key "label";
      description
        "Stack containing MPLS labels";

      leaf label {
        type rt-types:mpls-label;
        description
          "MPLS label value";
      }
    }
  }

  grouping srv6-sid-stack {
    description
      "Grouping for SRv6 label stack";

    list sids {
      key "sid";
      description
        "Stack containing SRv6 SIDs";

      leaf sid {
        type srv6-types:srv6-sid;
        description
          "SRv6 sid value";
      }
    }
  }

  grouping path-forwarding_state {
    description "Policy Forwarding path information";
    leaf path-id {
      type uint8;
      description "Primary path id";
    }



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    leaf next-hop-address {
      type inet:ip-address;
      description "Nexthop address";
    }
    leaf next-hop-table-id {
      type uint32;
      description "Table ID for nexthop address";
    }
    leaf outgoing-interface {
      type if:interface-ref;
      description "Outgoing interface handle";
    }
    container outgoing-sids {
      description
        "Outgoing sid stack";
      choice dataplanetype {
        description
          "Outgoing sids dataplane choice";
        case mpls {
          uses mpls-label-stack;
        }
        case srv6 {
          uses srv6-sid-stack;
        }
      }
    }
    leaf is-protected {
      type boolean;
      description "Is this path protected ?";
    }
    leaf is-pure-backup {
      type boolean;
      description "Is this path a pure backup ?";
    }
    leaf backup-path-id {
      type uint8;
      description "Backup path id";
    }
    leaf weight {
      type uint32;
      description "Path's weight for W-ECMP balancing";
    }
  }

  grouping explicit-path-properties {
    description
      "Explicit path properties of the candidate path";
    container segment-lists {



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      description
        "Path segment list(s) properties";
      list segment-list {
        key "name-ref";
        description "SR policy candidate path segment lists";

        leaf name-ref {
          type leafref {
            path "/rt:routing/ietf-sr-policy:segment-routing/ietf-sr-policy:sr-policy/ietf-sr-policy:policy-attributes/ietf-sr-policy:segment-lists/ietf-sr-policy:segment-list/ietf-sr-policy:name";
          }
          description "Reference to segment-list name";
        }
        leaf weight {
          type uint32;
          description "Segment-list weighted loadshare";
        }
        leaf is-valid {
          type boolean;
          config false;
          description
            "True if the segment-list is valid, False otherwise";
        }
        container forwarding-paths {
          config false;
          description
            "Forwarding state of paths";
          list forwarding-path {
            key "path-id";
            description "Forwarding path";
            uses path-forwarding_state;
          }
        }
      }
    }
  }

  grouping dynamic-path-properties {
    description
      "Dynamic path properties of the candidate path";
    leaf sid-dataplane-type {
      type sr-policy-types:dataplane-type;
      description
        "The dataplane type for the sid";
    }
    leaf is-valid {
      type boolean;
      config false;
      description



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        "True if the segment-list is valid, False otherwise";
    }
    container forwarding-paths {
      config false;
      description
        "Forwarding state of paths";
      list forwarding-path {
        key "path-id";
        description "Forwarding path";
        uses path-forwarding_state;
      }
    }
  }

  grouping candidate-path_state {
    description
      "Candidate path state properties grouping";
    leaf is-best-candidate-path {
      type boolean;
      default 'false';
      config false;
      description
        "True if the candidate path is the best candidate path, False otherwise";
    }
    leaf non-selection-reason {
      type identityref {
        base sr-policy-types:candidate-path-not-selected-reason;
      }
      config false;
      description
        "Candidate path not selected reason";
    }
  }

  grouping policy-properties_config {
    description
      "SR policy configuration grouping";
    leaf name {
      type string {
        length "1..59";
      }
      description "SR policy name";
    }
    leaf color {
      type uint32 {
        range "1..4294967295";
      }
      description "Color associated with the policy";



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    }
    leaf endpoint {
      type inet:ip-address;
      description "Policy end point IP address";
    }
    leaf description {
      type string;
      description "Description of the policy";
    }
    leaf admin-state {
      type sr-policy-types:policy-admin-state;
      default 'UP';
      description
        "SR policy administrative state, true for
        enabled, false for disabled";
    }
  }

  grouping policy-properties_state {
    description
      "SR policy property grouping";
    leaf oper-state {
      type sr-policy-types:policy-oper-state;
      config false;
      description
        "SR policy operational state";
    }
    leaf transition-count {
      type uint32;
      config false;
      description "Indicates number of up/down transitions";
    }
    leaf up-time {
      type yang:date-and-time;
      config false;
      description "Policy up time in seconds";
    }
    leaf down-time {
      type yang:date-and-time;
      config false;
      description "Policy down time in seconds";
    }
  }

  grouping policy-properties {
    description
      "SR policy properties";
    uses policy-properties_state;



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    uses binding-sid-properties;
    uses forwarding-counters;
  }

  grouping candidate-path-type {
    description "Candidate path type grouping";
    choice type {
      description
        "Type of candidate paths";
      case explicit {
        description "Candidate path with explicitly defined set/s of segment-lists";
        uses explicit-path-properties;
      }
      case dynamic {
        description "Candidate path with dynamic computed segment-lists";
        uses dynamic-path-properties;
      }
    }
  }

  grouping candidate-paths {
    description "SR policy candidate path grouping";
    container candidate-paths {
      description "SR policy candidate path(s) ";

      list candidate-path {
        key "protocol-origin originator discriminator";
        description "SR policy Candidate path(s) list entry";

        leaf protocol-origin {
          type sr-policy-types:protocol-origin-type;
          description
            "Instantiation mechanism used to create the candidate path";
        }
        leaf originator {
          type string;
          description
            "Identifier (concatenation of ASN and node-address) of the node
             that signalled/instantiated the candidate path on headend";
        }
        leaf discriminator {
          type uint32;
          description "Candidate path distinguisher";
        }
        leaf name {
          type string;
          description "Candidate path name";
        }



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        leaf preference {
          type uint32 {
            range "1..65535";
          }
          description "Candidate path preference";
        }
        leaf description {
          type string;
          description "Candidate path description";
        }
        container binding-sid {
          if-feature capability-candidate-path-binding-sid;
          description
            "Binding segment ID";
         uses binding-sid_config;
        }
        uses candidate-path_state;
        uses candidate-path-type;
      }
    }
  }

  grouping policies {
    description "SR policy grouping";
    container policies {
      description "SR Policy container";

      list policy {
        key "color endpoint";
        unique "name";
        description "SR Policy properties";

        leaf color {
          type uint32 {
            range "1..4294967295";
          }
          description "Color associated with the policy";
        }
        leaf endpoint {
          type inet:ip-address;
          description "Policy end point IP address";
        }
        leaf name {
          type string {
            length "1..59";
          }
          description "SR policy name";
        }



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        leaf description {
          type string;
          description "Description of the policy";
        }
        leaf admin-state {
          type sr-policy-types:policy-admin-state;
          default 'UP';
          description
            "SR policy administrative state, true for
            enabled, false for disabled";
        }
        leaf priority {
          type uint8;
          default 128;
          description "Priority considered when policy is recomputed due to topology changes";
        }

        uses policy-properties;

        uses candidate-paths;
      }
    }
  }

  grouping explicit-binding-sid-rules {
    description
      "Grouping for explicit binding sid rules";

    list explicit-binding-sid-rules {
      key "index";
      description
         "Explicit binding sid rules applicable for all policies";
      leaf index {
         type uint32;
         description "Explicit binding SID rules list index";
      }
      leaf rule {
         type sr-policy-types:explicit-binding-sid-rule-type;
         description "Explicit binding sid rule";
      }
    }
  }

  augment "/rt:routing" {
    description
       "This augments routing-instance configuration with segment-routing sr-policy.";
    container segment-routing {
      description "Main segment routing container";



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      container sr-policy {
        description "SR policy main container";

        uses policy-attributes;

        uses policies;
      }
    }
  }

  /* Notifications */

  notification sr-policy-oper-state-change-event {
   description
      "Notification event when the operational state of the SR policy changes";

   leaf policy-name-ref {
     type leafref {
       path "/rt:routing/ietf-sr-policy:segment-routing/ietf-sr-policy:sr-policy/ietf-sr-policy:policies/ietf-sr-policy:policy/ietf-sr-policy:name";
     }
     description "Reference to sr-policy name";
   }

   leaf policy-color-ref {
     type leafref {
       path "/rt:routing/ietf-sr-policy:segment-routing/ietf-sr-policy:sr-policy/ietf-sr-policy:policies/ietf-sr-policy:policy/ietf-sr-policy:color";
     }
     description "Reference to sr-policy color";
   }

   leaf policy-endpoint-ref {
     type leafref {
       path "/rt:routing/ietf-sr-policy:segment-routing/ietf-sr-policy:sr-policy/ietf-sr-policy:policies/ietf-sr-policy:policy/ietf-sr-policy:endpoint";
     }
     description "Reference to sr-policy endpoint";
   }

   leaf policy-new-oper-state  {
      type sr-policy-types:policy-oper-state;
      description "New operational state of the SR policy";
   }

   leaf policy-down-reason {
      type identityref {
        base sr-policy-types:policy-down-reason;
      }
      description "Down reason if the SR policy's new operational state is down";
   }



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  }

  notification sr-policy-candidate-path-change-event {
   description
      "Notification event when candidate path changes for SR policy";

   leaf policy-name-ref {
     type leafref {
       path "/rt:routing/ietf-sr-policy:segment-routing/ietf-sr-policy:sr-policy/ietf-sr-policy:policies/ietf-sr-policy:policy/ietf-sr-policy:name";
     }
     description "Reference to sr-policy name";
   }

   leaf policy-color-ref {
     type leafref {
       path "/rt:routing/ietf-sr-policy:segment-routing/ietf-sr-policy:sr-policy/ietf-sr-policy:policies/ietf-sr-policy:policy/ietf-sr-policy:color";
     }
     description "Reference to sr-policy color";
   }

   leaf policy-endpoint-ref {
     type leafref {
       path "/rt:routing/ietf-sr-policy:segment-routing/ietf-sr-policy:sr-policy/ietf-sr-policy:policies/ietf-sr-policy:policy/ietf-sr-policy:endpoint";
     }
     description "Reference to sr-policy endpoint";
   }

   leaf existing-preference {
      type uint32;
      description "Existing candidate path preference";
   }

   leaf new-preference {
      type uint32;
      description "New candidate path preference";
   }
  }

  notification sr-policy-binding-sid-unavailable-event {
   description
      "Notification event when the binding sid of sr-policy is unavailable";

   leaf policy-name-ref {
     type leafref {
       path "/rt:routing/ietf-sr-policy:segment-routing/ietf-sr-policy:sr-policy/ietf-sr-policy:policies/ietf-sr-policy:policy/ietf-sr-policy:name";
     }
     description "Reference to sr-policy name";
   }



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   leaf policy-color-ref {
     type leafref {
       path "/rt:routing/ietf-sr-policy:segment-routing/ietf-sr-policy:sr-policy/ietf-sr-policy:policies/ietf-sr-policy:policy/ietf-sr-policy:color";
     }
     description "Reference to sr-policy color";
   }

   leaf policy-endpoint-ref {
     type leafref {
       path "/rt:routing/ietf-sr-policy:segment-routing/ietf-sr-policy:sr-policy/ietf-sr-policy:policies/ietf-sr-policy:policy/ietf-sr-policy:endpoint";
     }
     description "Reference to sr-policy endpoint";
   }

   leaf policy-binding-sid-value-ref {
     type leafref {
       path "/rt:routing/ietf-sr-policy:segment-routing/ietf-sr-policy:sr-policy/ietf-sr-policy:policies/ietf-sr-policy:policy/ietf-sr-policy:binding-sid/ietf-sr-policy:value";
     }
     description "Reference to sr-policy binding-sid value";
   }

   leaf reason {
     type identityref {
       base sr-policy-types:binding-sid-unavailable-reason;
     }
     description
         "Reason why the binding sid is unavailable";
   }
  }

  notification sr-policy-candidate-path-binding-sid-mismatch-event {
   description
      "Notification event when binding sid of requested candidate path
      is different from the binding sid of the existing candidate path";

   leaf policy-color-ref {
     type leafref {
       path "/rt:routing/ietf-sr-policy:segment-routing/ietf-sr-policy:sr-policy/ietf-sr-policy:policies/ietf-sr-policy:policy/ietf-sr-policy:color";
     }
     description "Reference to sr-policy color";
   }

   leaf policy-endpoint-ref {
     type leafref {
       path "/rt:routing/ietf-sr-policy:segment-routing/ietf-sr-policy:sr-policy/ietf-sr-policy:policies/ietf-sr-policy:policy/ietf-sr-policy:endpoint";
     }
     description "Reference to sr-policy endpoint";
   }



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   leaf existing-candidate-path-protocol-origin-ref {
     type leafref {
       path "/rt:routing/ietf-sr-policy:segment-routing/ietf-sr-policy:sr-policy/ietf-sr-policy:policies/ietf-sr-policy:policy/ietf-sr-policy:candidate-paths/ietf-sr-policy:candidate-path/ietf-sr-policy:protocol-origin";
     }
     description "Reference to existing candidate path protocol origin";
   }

   leaf existing-candidate-path-preference-ref {
     type leafref {
      path "/rt:routing/ietf-sr-policy:segment-routing/ietf-sr-policy:sr-policy/ietf-sr-policy:policies/ietf-sr-policy:policy/ietf-sr-policy:candidate-paths/ietf-sr-policy:candidate-path/ietf-sr-policy:preference";
     }
     description "Reference to existing candidate path preference";
   }

   leaf existing-candidate-path-binding-sid-dataplane-ref {
     type leafref {
      path "/rt:routing/ietf-sr-policy:segment-routing/ietf-sr-policy:sr-policy/ietf-sr-policy:policies/ietf-sr-policy:policy/ietf-sr-policy:candidate-paths/ietf-sr-policy:candidate-path/ietf-sr-policy:binding-sid/ietf-sr-policy:dataplane";
     }
     description "Reference to existing candidate path binding sid dataplane type";
   }

   leaf existing-candidate-path-binding-sid-value-ref {
     type leafref {
      path "/rt:routing/ietf-sr-policy:segment-routing/ietf-sr-policy:sr-policy/ietf-sr-policy:policies/ietf-sr-policy:policy/ietf-sr-policy:candidate-paths/ietf-sr-policy:candidate-path/ietf-sr-policy:binding-sid/ietf-sr-policy:value";
     }
     description "Reference to existing candidate path binding sid value";
   }

   leaf conflicting-candidate-path-protocol-origin {
     type uint8;
     description "Conflicting candidate path protocol origin";
   }

   leaf conflicting-candidate-path-preference {
     type uint32;
     description "Conflicting candidate path preference";
   }

   leaf conflicting-candidate-path-binding-sid-dataplane {
     type sr-policy-types:dataplane-type;
     description "Conflicting candidate path binding sid dataplane type";
   }

   leaf conflicting-candidate-path-binding-sid-value {
     type sr-policy-types:sid-value-type;
     description "Conflicting candidate path binding sid value";
   }
  }



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  /* Features */

  feature capability-candidate-path-binding-sid {
    description
      "This feature enables the capability of specifying binding-sid
       for a candidate path.";
  }
}

<CODE ENDS>


                       Figure 6: ietf-sr-policy.yang

7.  Security Considerations

   The configuration, state, and notification data defined using YANG
   data models in this document are likely to be accessed via the
   protocols such as NETCONF [RFC6241] etc.

   Hence, YANG implementations MUST comply with the security
   requirements specified in section 15 of [RFC6020].  Additionally,
   NETCONF implementations MUST comply with the security requirements
   specified in sections 2.2, 2.3 and 9 of [RFC6241] as well as section
   3.7 of [RFC8341].

8.  IANA Considerations

   This document requests the registration of the following URIs in the
   IETF "XML registry" [RFC3688]:

   +------------------------------------------------+------------+-----+
   | URI                                            | Registrant | XML |
   +------------------------------------------------+------------+-----+
   | urn:ietf:params:xml:ns:yang:ietf-sr-policy-    | The IESG   | N/A |
   | types                                          |            |     |
   |                                                |            |     |
   | urn:ietf:params:xml:ns:yang:ietf-sr-policy     | The IESG   | N/A |
   +------------------------------------------------+------------+-----+

   This document requests the registration of the following YANG modules
   in the "YANG Module Names" registry [RFC6020]:









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   +--------------+------------------------------+------------+--------+
   | Name         | Namespace                    | Prefix     | Refere |
   |              |                              |            | nce    |
   +--------------+------------------------------+------------+--------+
   | ietf-sr-     | urn:ietf:params:xml:ns:yang  | sr-policy- | This d |
   | policy-types | :ietf-sr-policy-types        | types      | ocumen |
   |              |                              |            | t      |
   |              |                              |            |        |
   | ietf-sr-     | urn:ietf:params:xml:ns:yang  | sr-policy  | This d |
   | policy       | :ietf-sr-policy              |            | ocumen |
   |              |                              |            | t      |
   +--------------+------------------------------+------------+--------+

9.  Acknowledgments

   The authors of this document/YANG model would like to acknowledge the
   contributions/reviews by Johnson Thomas, Clarence Filsfils, Siva
   Sivabalan, Tarek Saad, Kris Michielsen, Dhanendra Jain, Ketan
   Talaulikar, Bhupendra Yadav, and Bruno Decraene.

10.  References

10.1.  Normative References

   [I-D.ietf-spring-segment-routing-policy]
              Filsfils, C., Sivabalan, S., daniel.voyer@bell.ca, d.,
              bogdanov@google.com, b., and P. Mattes, "Segment Routing
              Policy Architecture", draft-ietf-spring-segment-routing-
              policy-03 (work in progress), May 2019.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <https://www.rfc-editor.org/info/rfc2119>.

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

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

   [RFC6241]  Enns, R., Ed., Bjorklund, M., Ed., Schoenwaelder, J., Ed.,
              and A. Bierman, Ed., "Network Configuration Protocol
              (NETCONF)", RFC 6241, DOI 10.17487/RFC6241, June 2011,
              <https://www.rfc-editor.org/info/rfc6241>.



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   [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
              2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
              May 2017, <https://www.rfc-editor.org/info/rfc8174>.

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

   [RFC8342]  Bjorklund, M., Schoenwaelder, J., Shafer, P., Watsen, K.,
              and R. Wilton, "Network Management Datastore Architecture
              (NMDA)", RFC 8342, DOI 10.17487/RFC8342, March 2018,
              <https://www.rfc-editor.org/info/rfc8342>.

   [RFC8402]  Filsfils, C., Ed., Previdi, S., Ed., Ginsberg, L.,
              Decraene, B., Litkowski, S., and R. Shakir, "Segment
              Routing Architecture", RFC 8402, DOI 10.17487/RFC8402,
              July 2018, <https://www.rfc-editor.org/info/rfc8402>.

   [RFC8407]  Bierman, A., "Guidelines for Authors and Reviewers of
              Documents Containing YANG Data Models", BCP 216, RFC 8407,
              DOI 10.17487/RFC8407, October 2018,
              <https://www.rfc-editor.org/info/rfc8407>.

10.2.  Informative References

   [I-D.ietf-idr-segment-routing-te-policy]
              Previdi, S., Filsfils, C., Jain, D., Mattes, P., Rosen,
              E., and S. Lin, "Advertising Segment Routing Policies in
              BGP", draft-ietf-idr-segment-routing-te-policy-06 (work in
              progress), May 2019.

Authors' Addresses

   Kamran Raza (editor)
   Cisco Systems

   Email: skraza@cisco.com


   Robert Sawaya
   Cisco Systems

   Email: thjohns2@cisco.com







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   Zhuang Shunwan
   Huawei Technologies

   Email: zhuangshunwa@huawei.com


   Daniel Voyer
   Bell Canada

   Email: daniel.voyer@bell.ca


   Muhammad Durrani
   Equinix

   Email: mdurrani@equinix.com


   Satoru Matsushima
   SoftBank

   Email: satoru.matsushima@g.softbank.co.jp





























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