YANG Data Model for IS-IS SRv6
draft-ietf-lsr-isis-srv6-yang-00

Document Type Active Internet-Draft (lsr WG)
Authors Zhibo Hu , Dan Ye  , Yingzhen Qu  , Xuesong Geng  , Qiufang Ma 
Last updated 2021-08-18
Stream Internet Engineering Task Force (IETF)
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Network Working Group                                              Z. Hu
Internet-Draft                                                    Huawei
Intended status: Standards Track                                   D. Ye
Expires: 19 February 2022                                          Cisco
                                                                   Y. Qu
                                                               Futurewei
                                                                 X. Geng
                                                                   Q. Ma
                                                                  Huawei
                                                          18 August 2021

                     YANG Data Model for IS-IS SRv6
                    draft-ietf-lsr-isis-srv6-yang-00

Abstract

   This document defines a YANG data model that can be used to configure
   and manage IS-IS SRv6 [I-D.ietf-lsr-isis-srv6-extensions].

Requirements Language

   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 RFC 2119 [RFC2119].

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 19 February 2022.

Copyright Notice

   Copyright (c) 2021 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

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

Table of Contents

   1.  Overview  . . . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  IS-IS SRv6  . . . . . . . . . . . . . . . . . . . . . . . . .   2
   3.  IS-IS SRv6 configuration  . . . . . . . . . . . . . . . . . .   5
     3.1.  SRv6 activation . . . . . . . . . . . . . . . . . . . . .   5
     3.2.  Locator setting . . . . . . . . . . . . . . . . . . . . .   5
     3.3.  IP Fast reroute . . . . . . . . . . . . . . . . . . . . .   5
     3.4.  Microloop avoidance . . . . . . . . . . . . . . . . . . .   6
   4.  IS-IS SRv6 YANG Module  . . . . . . . . . . . . . . . . . . .   6
   5.  Security Considerations . . . . . . . . . . . . . . . . . . .  19
   6.  Contributors  . . . . . . . . . . . . . . . . . . . . . . . .  20
   7.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  20
   8.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  20
   9.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  20
   Appendix A.  Configuration examples . . . . . . . . . . . . . . .  22
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  23

1.  Overview

   YANG[RFC6020][RFC7950] is a data definition language used to define
   the contents of a conceptual data store that allows networked devices
   to be managed using NETCONF[RFC6241].  YANG is proving relevant
   beyond its initial confines, as bindings to other interfaces (e.g.,
   REST) and encodings other than XML (e.g., JSON) are being defined.
   Furthermore, YANG data models can be used as the basis for
   implementation of other interfaces, such as CLI and programmatic
   APIs.

   This document defines a YANG data model that can be used to configure
   and manage IS-IS SRv6 and it is an augmentation to the IS-IS YANG
   data model.

2.  IS-IS SRv6

   This document defines a model for IS-IS SRv6 feature.  It is an
   augmentation of the IS-IS base model.

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   The IS-IS SRv6 YANG module requires support for the base srv6
   module[I-D.ietf-spring-srv6-yang], which defines the global srv6
   configuration independent of any specific routing protocol
   configuration, and support of IS-IS base model
   [I-D.ietf-isis-yang-isis-cfg] which defines basic IS-IS configuration
   and state.  This module uses types defined in [RFC6991].  It also
   references [RFC8349], [I-D.ietf-spring-srv6-yang],
   [I-D.ietf-isis-yang-isis-cfg], [I-D.ietf-spring-sr-yang] and
   [I-D.ietf-spring-srv6-yang].

   The figure below describes the overall structure of the isis-srv6
   YANG module:

module: ietf-isis-srv6
  augment /rt:routing/rt:control-plane-protocols
          /rt:control-plane-protocol/isis:isis:
    +--rw srv6-cfg
    |  +--rw enable?                 boolean
    |  +--rw default-locator?        boolean
    |  +--rw locator-name*           -> /rt:routing/sr:segment-routing
    |                                /srv6:srv6/locators/locator/name
    |  +--rw persistent-end-x-sid?   boolean
    +--rw micro-loop-avoidance
       +--rw srv6-enable?             boolean
       +--rw srv6-rib-update-delay?   uint16
  augment /rt:routing/rt:control-plane-protocols
          /rt:control-plane-protocol/isis:isis/isis:fast-reroute:
    +--rw srv6-ti-lfa {srv6-ti-lfa}?
       +--rw enable?   boolean
  augment /rt:routing/rt:control-plane-protocols
          /rt:control-plane-protocol/isis:isis/isis:database
          /isis:levels/isis:lsp/isis:router-capabilities:
    +--ro v6-capability
    |  +--ro flags?   bits
    +--ro srv6-msd
       +--ro max-segments-left?   uint8
       +--ro max-end-pop?         uint8
       +--ro max-h-encaps?        uint8
       +--ro max-end-d?           uint8
  augment /rt:routing/rt:control-plane-protocols
          /rt:control-plane-protocol/isis:isis/isis:database
          /isis:levels/isis:lsp/isis:extended-is-neighbor/isis:neighbor:
    +--ro srv6-adjacency-sids
       +--ro end-x-sid* [sid]
          +--ro func-flags?           bits
          +--ro algorithm?            uint8
          +--ro weight?               uint8
          +--ro endpoint-func

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          |  +--ro flags?                     uint8
          |  +--ro endpoint-func?             identityref
          |  +--ro undefined-endpoint-func?   uint16
          +--ro sid                   srv6-sid-value
          +--ro neighbor-id?          isis:system-id
          +--ro srv6-sid-structure
             +--ro lb-length?    uint8
             +--ro ln-length?    uint8
             +--ro fun-length?   uint8
             +--ro arg-length?   uint8
  augment /rt:routing/rt:control-plane-protocols
          /rt:control-plane-protocol/isis:isis/isis:database
          /isis:levels/isis:lsp/isis:mt-is-neighbor/isis:neighbor:
    +--ro srv6-adjacency-sids
       +--ro end-x-sid* [sid]
          +--ro func-flags?           bits
          +--ro algorithm?            uint8
          +--ro weight?               uint8
          +--ro endpoint-func
          |  +--ro flags?                     uint8
          |  +--ro endpoint-func?             identityref
          |  +--ro undefined-endpoint-func?   uint16
          +--ro sid                   srv6-sid-value
          +--ro neighbor-id?          isis:system-id
          +--ro srv6-sid-structure
             +--ro lb-length?    uint8
             +--ro ln-length?    uint8
             +--ro fun-length?   uint8
             +--ro arg-length?   uint8
  augment /rt:routing/rt:control-plane-protocols
          /rt:control-plane-protocol/isis:isis/isis:database
          /isis:levels/isis:lsp:
    +--ro srv6-locators
       +--ro locator* [locator]
          +--ro mt-id?                   uint16
          +--ro flags?                   bits
          +--ro metric?                  uint32
          +--ro algorithm?               uint8
          +--ro loc-size?                uint8
          +--ro locator                  inet:ipv6-address-no-zone
          +--ro srv6-end-sids
          |  +--ro end-sid* [sid]
          |     +--ro flags?                uint8
          |     +--ro endpoint-func
          |     |  +--ro flags?                     uint8
          |     |  +--ro endpoint-func?             identityref
          |     |  +--ro undefined-endpoint-func?   uint16
          |     +--ro sid                   srv6-sid-value

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          |     +--ro srv6-sid-structure
          |        +--ro lb-length?    uint8
          |        +--ro ln-length?    uint8
          |        +--ro fun-length?   uint8
          |        +--ro arg-length?   uint8
          +--ro external-prefix-flag?    boolean
          +--ro readvertisement-flag?    boolean
          +--ro node-flag?               boolean
          +--ro ipv4-source-router-id?   inet:ipv4-address
          +--ro ipv6-source-router-id?   inet:ipv6-address
  augment /rt:routing/rt:control-plane-protocols
          /rt:control-plane-protocol/isis:isis/isis:interfaces
          /isis:interface/isis:adjacencies/isis:adjacency:
    +--ro end-x-sid* [value]
       +--ro value                   srv6-sid-value
       +--ro weight?                 uint8
       +--ro protection-requested?   boolean
       +--ro persistent?             boolean
       +--ro algorithm?              uint8
       +--ro endpoint-func
          +--ro flags?                     uint8
          +--ro endpoint-func?             identityref
          +--ro undefined-endpoint-func?   uint16

3.  IS-IS SRv6 configuration

3.1.  SRv6 activation

   Activation of IS-IS SRv6 is done by setting the "enable" leaf to
   true.  This triggers advertisement of SRv6 extensions based on the
   configuration parameters that have been setup using the base SRv6
   module.

3.2.  Locator setting

   The basic SRv6 module defines the related locator leafs.  When the
   IS-IS SRv6 module is enabled, set the locator by using the following
   strategy: firstly, it is reasonable to check whether the default
   locator is used, if not, to use the specified locator.  The strategy
   is realized by adding the leaf "default-locator", "locator-name" .

3.3.  IP Fast reroute

   IS-IS SRv6 model augments the fast-reroute container.  It brings the
   ability to activate ipv6 TI-LFA (topology independent LFA).

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3.4.  Microloop avoidance

   IS-IS SRv6 model augments the micro-loop-avoidance container, this
   container including the leaf "srv6-enable" brings the ability to
   activate SRv6 avoid-microloop.

4.  IS-IS SRv6 YANG Module

   <CODE BEGINS> file "ietf-isis-srv6@2020-07-13.yang"
   module ietf-isis-srv6 {
     yang-version 1.1;
     namespace "urn:ietf:params:xml:ns:"
             + "yang:ietf-isis-srv6";
     prefix isis-srv6;

     import ietf-routing {
       prefix "rt";
       reference "RFC8349: A YANG Data Model for
                 Routing Management (NMDA Version)";
     }

     import ietf-isis {
       prefix "isis";
       reference "draft-ietf-isis-yang-isis-cfg: YANG
                  Data Model for IS-IS Protocol";
     }

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

     import ietf-segment-routing {
       prefix sr;
       reference "draft-ietf-spring-sr-yang: YANG Data
                  Model for Segment Routing";
     }
     import ietf-srv6-base {
       prefix "srv6";
       reference "draft-ietf-spring-srv6-yang: YANG Data
                  Model for SRv6 Base and Static";

     }

     organization
      "IETF LSR Working Group";

     contact

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       "WG List:  <mailto:spring@ietf.org>
       Author:    Zhibo Hu
                  <mailto:huzhibo@huawei.com>
       Author:    Dan Ye
                  <mailto:daye@cisco.com>
       Author:    Yingzhen Qu
                  <mailto:yingzhen.qu@futurewei.com>
       Author:    Qiufang Ma
                  <mailto:maqiufang1@huawei.com>
       ";
     description
       "The YANG module defines a generic configuration model for
       Segment IPV6 routing ISIS extensions common across all of
       the vendor implementations.";

     revision 2020-07-13 {
       description
           "Initial revision.";
       reference "draft-ietf-lsr-isis-srv6-extensions-08";
     }

     /* Identities */
     identity SRV6_END_FUNC_TYPE {
       description
       "Base identity type for srv6 endpoint function code points.";
     }

     identity SRV6_END_FUNC_PSP_USP_USD {
       base "SRV6_END_FUNC_TYPE";
       description
       "End (May support PSP, USP, USD).";
     }

     identity SRV6_END_X_FUNC_PSP_USP_USD {
       base "SRV6_END_FUNC_TYPE";
       description
       "End.X(May support PSP, USP, USD)";
     }

     identity SRV6_END_T_FUNC_PSP_USP_USD {
       base "SRV6_END_FUNC_TYPE";
       description
       "END (May support PSP, USP, USD)";
     }

     identity SRV6_END_FUNC_DX6 {
       base "SRV6_END_FUNC_TYPE";
       description

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       "End.DX6.";
     }

     identity SRV6_END_FUNC_DX4 {
       base "SRV6_END_FUNC_TYPE";
       description
       "End.DX4.";
     }

     identity SRV6_END_FUNC_DT6 {
       base "SRV6_END_FUNC_TYPE";
       description
       "End.DT6.";
     }

     identity SRV6_END_FUNC_DT4 {
       base "SRV6_END_FUNC_TYPE";
       description
       "End.DT4.";
     }

     identity SRV6_END_FUNC_DT64 {
       base "SRV6_END_FUNC_TYPE";
       description
       "End.DT64.";
     }

     identity SRV6_END_FUNC_OP {
       base "SRV6_END_FUNC_TYPE";
       description
       "END.OP .";
     }

     identity SRV6_END_FUNC_OTP {
       base "SRV6_END_FUNC_TYPE";
       description
       "END.OTP .";
     }

     /* typedef */
     typedef srv6-sid-value {
       type inet:ipv6-address-no-zone;
       description
         "16 Octets encoded sid value.";
     }

     /* Features */
     feature srv6-ti-lfa {

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       description
        "Enhance SRv6 FRR with ti-lfa
        support";
     }
     /* Groupings */
     grouping srv6-msds {
       description
         "means to advertise to advertise node/link specific
          values for Maxium Sid Depths(MSD) of various types";
       container srv6-msd {
         description
           "Maximum SRv6 SID Depths.";
         leaf max-segments-left {
           type uint8;
           description
             "The Maximum Segments Left MSD Type specifies
              the maximum value of the 'SL' field in the SRH
              of a received packet before applying the
              Endpoint behavior associated with a SID.";
         }
         leaf max-end-pop {
           type uint8;
           description
           "The Maximum End Pop MSD Type specifies the maximum
            number of SIDs in the SRH to which the router can
            apply 'PSP' or 'USP' behavior, as defined in flavors.";
         }
         leaf max-h-encaps {
           type uint8;
           description
           "The Maximum H.Encaps MSD Type specifies the maximum number
            of SIDs that can be included as part of the 'H.Encaps'
            behavior";
         }
         leaf max-end-d {
           type uint8;
           description
             "The maximum number of SIDs in an SRH when performing
              decapsulation associated with 'End.Dx' functions
              (e.g., 'End.DX6' and 'End.DT6').";
         }
       }
     }

     grouping srv6-sid-structures {
       description
         "This group defines SRv6 SID Structure sub-sub-TLV.";
       container srv6-sid-structure {

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         description
           "SRv6 SID Structure sub-sub-TLV is used to advertise
            the length of each individual part of the SRv6 SID
            as defined in [I-D.ietf-spring-srv6-network-programming]";
         leaf lb-length {
           type uint8;
           description
             "SRv6 SID Locator Block length in bits.";
         }

         leaf ln-length {
           type uint8;
           description
             "SRv6 SID Locator Node length in bits.";
         }

         leaf fun-length {
           type uint8;
           description
             "SRv6 SID Function length in bits.";
         }

         leaf arg-length {
           type uint8;
           description
             "SRv6 SID Argument length in bits.";
         }
       }
     }
     grouping srv6-capability {
       description
       "SRV6 capability grouping.";
       container v6-capability {
         description
           "SRv6 capability.";
         leaf flags {
           type bits {
             bit o-flag {
               position 1;
               description
               "If set, then the router is able to
                use of the O-bit in the Segment Routing Header(SRH)
                as defined in [draft-ietf-6man-segment-routing-header].";
             }
           }
           description
           "Flags.";
         }

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       }
     }

     grouping srv6-endpoint-func {
        description
         "This group defines srv6 endpoint function";
       container endpoint-func {
         description
           "Srv6 Endpoint function Descriptor.";
         leaf flags {
           type uint8;
           description
             "No flags are currently being defined.";
         }
         leaf endpoint-func {
           type identityref {
            base isis-srv6:SRV6_END_FUNC_TYPE;
           }
           description
             "The endpoint function.";
         }
         leaf undefined-endpoint-func {
           type uint16;
           description
             "Unknown endpoint func value.";
         }
       }
     }

     grouping srv6-end-sid {
       description
       "SRv6 Segment Identifier(SID) with Endpoint functions.";
       leaf flags {
         type uint8;
         description
           "NO flags are currently being defined.";
       }

       uses srv6-endpoint-func;

       leaf sid {
         type srv6-sid-value;
         description
           "SRV6 sid value.";
       }
       // sub-sub-tlvs
       uses srv6-sid-structures;
     }

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     grouping srv6-locator {
       description
         "This group defines srv6 locator tlv.";
       leaf mt-id {
         type uint16 {
           range "0..4095";
         }
         description
           "Multitopology Identifier as defined in [RFC5120].";
       }
       leaf flags {
         type bits {
           bit d-flag {
             position 0;
             description
               "When the locator is leaked from level-2 to leve-1,
                the d-flag must be set.";
           }
         }
         description
           "Flags for srv6 locator tlv.";
       }

       leaf metric {
         type uint32;
         description
           "Metric value.";
       }
       leaf algorithm {
         type uint8;
         description
         "Associated algorithm.";
       }

       leaf loc-size {
         type uint8;
         description
           "Number of bits in the locator field.";
       }
       leaf locator {
         type inet:ipv6-address-no-zone;
         description
           "Advertised SRV6 locator.";
       }
       container srv6-end-sids {
         description
           "This contains list of srv6 end sids.";
         list end-sid {

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           key "sid";
           description
             "List of SRV6 SRv6 Segment Identifiers (SID)
              with Endpoint functions.";
           uses srv6-end-sid;
         }
       }
       uses isis:prefix-reachability-attributes;
       uses isis:prefix-ipv4-source-router-id;
       uses isis:prefix-ipv6-source-router-id;
     }

     grouping srv6-adjacency-sid {
       description
       "SRv6 sid associated with an adjacency.";

       leaf func-flags {
         type bits {
           bit b-flag {
             position 0;
             description
               "Backup flag. If set, the End.X sid is
                eligible for protection.";
           }

           bit s-flag {
             position 1;
             description
               "Set flag. When set, the End.X sid refers to
                a set of adjacencies (and therefore May be assigned
                to other adjacencies as well.";
           }

           bit p-flag {
             position 2;
             description
             "Persistent flag. When set, the End.X sid is persistently
              allocated, i.e., the End.x sid value remains consistent
              across router restart and/or interface flap.";
           }
         }
         description
             "Flags for srv6 end x sid.";
       }

       leaf algorithm {
         type uint8;
         description

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           "Associated algorithm.";
       }

       leaf weight {
         type uint8;
         description
         "The value represents the weight of the End.X sid
          for the purpose of load balancing.";
       }

       uses srv6-endpoint-func;

       leaf sid {
         type srv6-sid-value;
         description
           "SRV6 sid value.";
       }

       leaf neighbor-id {
         type isis:system-id;
         description
           "Describes the system ID of the neighbor
            associated with the SID value. This is only
            used on LAN adjacencies.";
       }

       // sub-sub-tlvs
       uses srv6-sid-structures;
     }

     grouping srv6-adjacency-state {
       description
        "This group will extend adjacency state.";
       list end-x-sid {
         key value;
         config false;
         leaf value {
           type srv6-sid-value;
           description
            "Value of the Adj-SID.";
         }
         leaf weight {
           type uint8;
           description
            "Weight associated with
            the End.X SID.";
         }
         leaf protection-requested {

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           type boolean;
           description
            "Set to True if the End.X SID
            must be protected.";
         }
         leaf persistent {
           type boolean;
           description
             "Persistent flag. When set, the End.X sid is persistently
              allocated, i.e., the End.X sid value remains consistent
              across router restart and/or interface flap.";
         }
         leaf algorithm {
           type uint8;
           description
           "Associated algorithm.";
         }
         uses srv6-endpoint-func;

         description
          "List of End.X Segment IDs.";
       }
     }
     /* Cfg */
     augment "/rt:routing/" +
             "rt:control-plane-protocols/rt:control-plane-protocol"+
             "/isis:isis" {
       when "/rt:routing/rt:control-plane-protocols/"+
            "rt:control-plane-protocol/rt:type = 'isis:isis'" {
         description
           "This augment ISIS routing protocol when used";
       }
       description
         "This augments ISIS protocol configuration
          with SRv6.";

       container srv6-cfg{
         leaf enable{
           type boolean;
           default "false";
           description
             "Enables SRv6
              protocol extensions.";
         }

         leaf default-locator {
           type boolean;
           default "false";

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           description
             "Enable ISIS segment-routing IPv6 with default Locator.";
         }

         leaf-list locator-name {
           when "../default-locator = 'false'" {
             description
               "Only applies to non default locator.";
           }
           type leafref {
             path "/rt:routing/sr:segment-routing/srv6:srv6" +
                   "/srv6:locators/srv6:locator/srv6:name";
           }
           description
             "Enable ISIS segment-routing IPv6 with specified Locator.";
         }

         leaf persistent-end-x-sid{
           type boolean;
           default "false";
           description
             "Enable the persistent nature of End.X sid";
         }
         description
           "Configuration about ISIS segment-routing IPv6.";
       }
       container micro-loop-avoidance {
         leaf srv6-enable {
           type boolean;
           default "false";
           description
             "Enable SRv6 avoid-microloop.Depend on SR IPv6 Enable.";
         }

         leaf srv6-rib-update-delay {
           type uint16 {
             range "1000..10000";
           }
           units "ms";
           default "5000";
           description
             "Set the route delivery delay for SRv6 avoid-microloop.
              Depend on SR IPv6 Enable.";
         }

         description

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           "Enable IS-IS avoid-microloop.";
       }
     }

     augment "/rt:routing/" +
             "rt:control-plane-protocols/rt:control-plane-protocol"+
             "/isis:isis/isis:fast-reroute"{
       when "/rt:routing/rt:control-plane-protocols/"+
            "rt:control-plane-protocol/rt:type = 'isis:isis'"{
         description
           "This augment ISIS routing protocol when used";
       }
       description
         "This augments ISIS IPFRR with IPV6 TILFA.";

       container srv6-ti-lfa {

         if-feature srv6-ti-lfa;
         leaf enable {
           type boolean;
           description
             "Enables SRv6 TI-LFA computation.";
         }

         description
           "SRv6 TILFA configuration.";
       }
     }

     /* Operational states */
     augment "/rt:routing/" +
           "rt:control-plane-protocols/rt:control-plane-protocol"+
           "/isis:isis/isis:database/isis:levels/isis:lsp"+
           "/isis:router-capabilities" {
        when "/rt:routing/rt:control-plane-protocols/"+
           "rt:control-plane-protocol/rt:type = 'isis:isis'" {
         description
           "This augment ISIS routing protocol when used";
       }
       description
        "This augments ISIS protocol router capability.";
         uses srv6-capability;
         uses srv6-msds;
     }

     augment "/rt:routing/" +
           "rt:control-plane-protocols/rt:control-plane-protocol"+
           "/isis:isis/isis:database/isis:levels/isis:lsp"+

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           "/isis:extended-is-neighbor/isis:neighbor" {
        when "/rt:routing/rt:control-plane-protocols/"+
           "rt:control-plane-protocol/rt:type = 'isis:isis'" {
         description
         "This augment ISIS routing protocol when used.";
       }
       description
        "This augments ISIS protocol neighbor.";
       container srv6-adjacency-sids {
         description
           "This defines svr6 end-x sids for the adjacency.";
         list end-x-sid {
           key "sid";
           uses srv6-adjacency-sid;
           description
              "List of end-x sids.";
         }
       }
     }
     augment "/rt:routing/" +
           "rt:control-plane-protocols/rt:control-plane-protocol"+
           "/isis:isis/isis:database/isis:levels/isis:lsp"+
           "/isis:mt-is-neighbor/isis:neighbor" {
               when "/rt:routing/rt:control-plane-protocols/"+
           "rt:control-plane-protocol/rt:type = 'isis:isis'" {
         description
           "This augment ISIS routing protocol when used.";
       }
       description
         "This augments ISIS protocol neighbor.";
       container srv6-adjacency-sids {
          description
           "This defines svr6 end-x sids for the adjacency.";
         list end-x-sid {
           key "sid";
           uses srv6-adjacency-sid;
            description
              "List of end-x sids.";
         }
       }
     }

     augment "/rt:routing/" +
           "rt:control-plane-protocols/rt:control-plane-protocol"+
           "/isis:isis/isis:database/isis:levels/isis:lsp" {
           when "/rt:routing/rt:control-plane-protocols/"+
           "rt:control-plane-protocol/rt:type = 'isis:isis'" {
         description

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         "This augment ISIS routing protocol when used.";
       }
       description
        "This augments ISIS protocol LSDB.";
       container srv6-locators {
         description
            "This defines srv6 locator tlvs.";
         list locator {
           key "locator";
           uses srv6-locator;
           description
             "List of srv6 locators.";
         }
       }
     }

     augment "/rt:routing/" +
           "rt:control-plane-protocols/rt:control-plane-protocol"+
           "/isis:isis/isis:interfaces/isis:interface" +
           "/isis:adjacencies/isis:adjacency" {
       when "/rt:routing/rt:control-plane-protocols/"+
           "rt:control-plane-protocol/rt:type = 'isis:isis'" {
         description
         "This augment ISIS routing protocol when used.";
       }
       description
         "This augments ISIS protocol operational state
          with segment routing.";
       uses  srv6-adjacency-state;
     }
     /* Notifications */
   }
   <CODE ENDS>

5.  Security Considerations

   Configuration and state data defined in this document are designed to
   be accessed via the NETCONF protocol [RFC6241].

   As IS-IS is an IGP protocol (critical piece of the network), ensuring
   stability and security of the protocol is mandatory for the network
   service.

   Authors recommends to implement NETCONF access control model
   ([RFC6536]) to restrict access to all or part of the configuration to
   specific users.

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6.  Contributors

   Jiajia Dong
   Huawei
   China

   Email:dongjiajia@huawei.com

7.  Acknowledgements

   TBD.

8.  IANA Considerations

   The IANA is requested to assign two new URIs from the IETF XML
   registry ([RFC3688]).  Authors are suggesting the following URI:

               URI: urn:ietf:params:xml:ns:yang:ietf-isis-srv6
               Registrant Contact: IS-IS WG
               XML: N/A, the requested URI is an XML namespace

   This document also requests one new YANG module name in the YANG
   Module Names registry ([RFC6020]) with the following suggestion :

  name: ietf-isis-srv6
  namespace: urn:ietf:params:xml:ns:yang:ietf-isis-srv6 prefix: isis-srv6
  reference: RFC XXXX

9.  References

   [I-D.ietf-isis-yang-isis-cfg]
              Litkowski, S., Yeung, D., Lindem, A., Zhang, J., and L.
              Lhotka, "YANG Data Model for IS-IS Protocol", Work in
              Progress, Internet-Draft, draft-ietf-isis-yang-isis-cfg-
              42, 15 October 2019, <https://www.ietf.org/archive/id/
              draft-ietf-isis-yang-isis-cfg-42.txt>.

   [I-D.ietf-lsr-isis-srv6-extensions]
              Psenak, P., Filsfils, C., Bashandy, A., Decraene, B., and
              Z. Hu, "IS-IS Extensions to Support Segment Routing over
              IPv6 Dataplane", Work in Progress, Internet-Draft, draft-
              ietf-lsr-isis-srv6-extensions-17, 18 June 2021,
              <https://www.ietf.org/archive/id/draft-ietf-lsr-isis-srv6-
              extensions-17.txt>.

   [I-D.ietf-spring-sr-yang]
              Litkowski, S., Qu, Y., Lindem, A., Sarkar, P., and J.
              Tantsura, "YANG Data Model for Segment Routing", Work in

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              Progress, Internet-Draft, draft-ietf-spring-sr-yang-30, 25
              January 2021, <https://www.ietf.org/archive/id/draft-ietf-
              spring-sr-yang-30.txt>.

   [I-D.ietf-spring-srv6-yang]
              Raza, K., Agarwal, S., Liu, X., Hu, Z., Hussain, I., Shah,
              H., Voyer, D., Matsushima, S., Horiba, K., AbdelSalam, A.,
              and J. Rajamanickam, "YANG Data Model for SRv6 Base and
              Static", Work in Progress, Internet-Draft, draft-ietf-
              spring-srv6-yang-00, 9 September 2020,
              <https://www.ietf.org/archive/id/draft-ietf-spring-srv6-
              yang-00.txt>.

   [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>.

   [RFC6536]  Bierman, A. and M. Bjorklund, "Network Configuration
              Protocol (NETCONF) Access Control Model", RFC 6536,
              DOI 10.17487/RFC6536, March 2012,
              <https://www.rfc-editor.org/info/rfc6536>.

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

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

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

Appendix A.  Configuration examples

   The following is an XML example using IS-IS SRv6 YANG module.

      <routing xmlns="urn:ietf:params:xml:ns:yang:ietf-routing">
        <control-plane-protocols>
       <control-plane-protocol>
         <isis xmlns="urn:ietf:params:xml:ns:yang:ietf-isis">
        <srv6-cfg>
         <enable>true</enable>
      <default-locator>false</default-locator>
      <locator-name>DOM0_ALG0</locator-name>
      <persistent-end-x-sid>true</persistent-end-x-sid>
        </srv6-cfg>
        <micro-loop-avoidance>
         <srv6-enable>true</srv6-enable>
      <srv6-rib-update-delay>2000</srv6-rib-update-delay>
        </micro-loop-avoidance>
      </isis>
       </control-plane-protocol>
     </control-plane-protocols>
      </routing>

      <routing xmlns="urn:ietf:params:xml:ns:yang:ietf-routing">
        <control-plane-protocols>
       <control-plane-protocol>
         <isis xmlns="urn:ietf:params:xml:ns:yang:ietf-isis">
              <fast-reroute>
         <srv6-ti-lfa>
        <enable>true</enable>
      </srv6-ti-lfa>
        </fast-reroute>
      </isis>
       </control-plane-protocol>
     </control-plane-protocols>
      </routing>

   The following is the corresponding example using JSON format.

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   {
      "control-plane-protocols": {
         "control-plane-protocol": {
            "isis": {
               "srv6-cfg": {
                  "enable": "true",
                  "default-locator": "false",
                  "locator-name": "DOM0_ALG0",
                  "persistent-end-x-sid": "true"
               },
               "micro-loop-avoidance": {
                  "srv6-enable": "true",
                  "srv6-rib-update-delay": "2000"
               }
            }
         }
      }
   }

   {
      "control-plane-protocols": {
         "control-plane-protocol": {
            "isis": {
               "fast-reroute": {
                  "srv6-ti-lfa": {
                     "enable": "true"
                  }
               }
            }
         }
      }
   }

Authors' Addresses

   Zhibo Hu
   Huawei
   Huawei Bld., No.156 Beiqing Rd.
   Beijing
   100095
   China

   Email: huzhibo@huawei.com

   Dan Ye
   Cisco
   170 W. Tasman Dr. San Jose,

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   California,  95134
   United States of America

   Email: daye@cisco.com

   Yingzhen Qu
   Futurewei
   2330 Central Express Way
   Santa Clara,  950950
   United States of America

   Email: yingzhen.qu@futurewei.com

   Xuesong Geng
   Huawei
   Huawei Bld., No.156 Beiqing Rd.
   Beijing
   100095
   China

   Email: gengxuesong@huawei.com

   Qiufang Ma
   Huawei
   101 Software Avenue, Yuhua District
   Nanjing
   Jiangsu, 210012
   China

   Email: maqiufang1@huawei.com

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