IS-IS Working Group                                         S. Litkowski
Internet-Draft                                                    Orange                                             Cisco Systems
Intended status: Standards Track                                   Y. Qu
Expires: January 8, July 12, 2020                                         Futurewei
                                                               P. Sarkar
                                                              Individual
                                                                 I. Chen
                                                   The MITRE Corporation
                                                             J. Tantsura
                                                              Individual
                                                            July 7, 2019
                                                                  Apstra
                                                         January 9, 2020

               YANG Data Model for IS-IS Segment Routing
                       draft-ietf-isis-sr-yang-06
                       draft-ietf-isis-sr-yang-07

Abstract

   This document defines a YANG data model that can be used to configure
   and manage IS-IS Segment Routing.

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 January 8, July 12, 2020.

Copyright Notice

   Copyright (c) 2019 2020 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

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

Table of Contents

   1.  Overview  . . . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Requirements Language . . . . . . . . . . . . . . . . . . . .   3
   3.  Tree Diagrams . . . . . . . . . . . . . . . . . . . . . . . .   3
   4.  IS-IS Segment Routing . . . . . . . . . . . . . . . . . . . .   3
   5.  IS-IS Segment Routing configuration . . . . . . . . . . . . .   6
     5.1.  Segment Routing activation  . . . . . . . . . . . . . . .   6
     5.2.  Advertising mapping server policy . . . . . . . . . . . .   6
     5.3.  IP Fast reroute . . . . . . . . . . . . . . . . . . . . .   6
   6.  IS-IS Segment Routing YANG Module . . . . . . . . . . . . . .   6
   7.  Security Considerations . . . . . . . . . . . . . . . . . . .  20  21
   8.  Contributors  . . . . . . . . . . . . . . . . . . . . . . . .  21
   9.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  21
   10. IANA Considerations . . . . . . . . . . . . . . . . . . . . .  21  22
   11. Change log for ietf-isis-sr YANG module . . . . . . . . . . .  21  22
     11.1.  From version -03 to version -04  . . . . . . . . . . . .  21  22
     11.2.  From version -02 to version -03  . . . . . . . . . . . .  22
     11.3.  From isis-sr document version -01 to version -02 . . . .  22
     11.4.  From isis-sr document version -00 to version -01 . . . .  22  23
     11.5.  From isis document version -12 to isis-sr document
            version -00  . . . . . . . . . . . . . . . . . . . . . .  22  23
     11.6.  From isis document version -12 to version -13  . . . . .  22  23
     11.7.  From isis document version -09 to version -11  . . . . .  22  23
     11.8.  From isis document version -08 to version -09  . . . . .  22  23
     11.9.  From isis document version -07 to version -08  . . . . .  22  23
   12. Normative References  . . . . . . . . . . . . . . . . . . . .  23
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  24

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 Segment Routing

   [I-D.ietf-isis-segment-routing-extensions] [RFC8667] and it is an augmentation
   to the IS-IS YANG data model.

   The YANG modules in this document conform to the Network Management
   Datastore Architecture (NMDA) [RFC8342].

2.  Requirements Language

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "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.  Tree Diagrams

   This document uses the graphical representation of data models
   defined in [RFC8340].

4.  IS-IS Segment Routing

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

   The IS-IS SR YANG module requires support for the base segment
   routing module [I-D.ietf-spring-sr-yang], which defines the global
   segment routing 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.

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

module: ietf-isis-sr
  augment /rt:routing/rt:control-plane-protocols
          /rt:control-plane-protocol/isis:isis:
    +--rw segment-routing
    |  +--rw enabled?    boolean
    |  +--rw bindings
    |     +--rw advertise
    |     |  +--rw policies*   string
    |     +--rw receive?     boolean
    +--rw protocol-srgb {sr:protocol-srgb}? {sr-mpls:protocol-srgb}?
       +--rw srgb* [lower-bound upper-bound]
          +--rw lower-bound    uint32
          +--rw upper-bound    uint32
  augment /rt:routing/rt:control-plane-protocols
          /rt:control-plane-protocol/isis:isis/isis:interfaces
          /isis:interface:
    +--rw segment-routing
       +--rw adjacency-sid
          +--rw adj-sids* [value]
          |  +--rw value-type?   enumeration
          |  +--rw value         uint32
          |  +--rw protected?    boolean
          +--rw advertise-adj-group-sid* [group-id]
          |  +--rw group-id    uint32
          +--rw advertise-protection?      enumeration
  augment /rt:routing/rt:control-plane-protocols
          /rt:control-plane-protocol/isis:isis/isis:interfaces
          /isis:interface/isis:fast-reroute:
    +--rw ti-lfa {ti-lfa}?
       +--rw enable?   boolean
  augment /rt:routing/rt:control-plane-protocols
          /rt:control-plane-protocol/isis:isis/isis:interfaces
          /isis:interface/isis:fast-reroute/isis:lfa/isis:remote-lfa:
    +--rw use-segment-routing-path?   boolean {remote-lfa-sr}?
  augment /rt:routing/rt:control-plane-protocols
          /rt:control-plane-protocol/isis:isis/isis:interfaces
          /isis:interface/isis:adjacencies/isis:adjacency:
    +--ro adjacency-sid* [value]
       +--ro af?                     iana-rt-types:address-family
       +--ro value                   uint32
       +--ro weight?                 uint8
       +--ro protection-requested?   boolean
  augment /rt:routing/rt:control-plane-protocols
          /rt:control-plane-protocol/isis:isis/isis:database
          /isis:levels/isis:lsp/isis:router-capabilities:
    +--ro sr-capability
    |  +--ro flags?           bits sr-capability
    |  |  +--ro sr-capability-bits*   identityref
    |  +--ro global-blocks
    |     +--ro global-block* []
    |        +--ro range-size?    uint32
    |        +--ro sid-sub-tlv
    |           +--ro sid?   uint32
    +--ro sr-algorithms
    |  +--ro sr-algorithm*   uint8
    +--ro local-blocks
    |  +--ro local-block* []
    |     +--ro range-size?    uint32
    |     +--ro sid-sub-tlv
    |        +--ro sid?   uint32
    +--ro srms-preference
       +--ro preference?   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:
          /rt:control-plane-protocol/isis:isis/isis:database/isis:levels
          /isis:lsp/isis:extended-is-neighbor/isis:neighbor:

    +--ro sid-list* [value]
       +--ro flags?         bits adj-sid-flags
       |  +--ro bits*   identityref
       +--ro weight?          uint8
       +--ro neighbor-id?     isis:system-id
       +--ro value            uint32
  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 sid-list* [value]
       +--ro flags?         bits adj-sid-flags
       |  +--ro bits*   identityref
       +--ro weight?          uint8
       +--ro neighbor-id?     isis:system-id
       +--ro value            uint32
  augment /rt:routing/rt:control-plane-protocols
          /rt:control-plane-protocol/isis:isis/isis:database
          /isis:levels/isis:lsp/isis:extended-ipv4-reachability
          /isis:prefixes:
    +--ro sid-list* [value]
       +--ro flags?       bits perfix-sid-flags
       |  +--ro bits*   identityref
       +--ro algorithm?          uint8
       +--ro value               uint32
  augment /rt:routing/rt:control-plane-protocols
          /rt:control-plane-protocol/isis:isis/isis:database
          /isis:levels/isis:lsp/isis:mt-extended-ipv4-reachability
          /isis:prefixes:
    +--ro sid-list* [value]
       +--ro flags?       bits perfix-sid-flags
       |  +--ro bits*   identityref
       +--ro algorithm?          uint8
       +--ro value               uint32
  augment /rt:routing/rt:control-plane-protocols
          /rt:control-plane-protocol/isis:isis/isis:database
          /isis:levels/isis:lsp/isis:ipv6-reachability/isis:prefixes:
    +--ro sid-list* [value]
       +--ro flags?       bits perfix-sid-flags
       |  +--ro bits*   identityref
       +--ro algorithm?          uint8
       +--ro value               uint32
  augment /rt:routing/rt:control-plane-protocols
          /rt:control-plane-protocol/isis:isis/isis:database
             /isis:levels/isis:lsp/isis:mt-ipv6-reachability
             /isis:prefixes:
          /isis:levels/isis:lsp/isis:mt-ipv6-reachability/isis:prefixes:
    +--ro sid-list* [value]
       +--ro flags?       bits perfix-sid-flags
       |  +--ro bits*   identityref
       +--ro algorithm?          uint8
       +--ro value               uint32
  augment /rt:routing/rt:control-plane-protocols
          /rt:control-plane-protocol/isis:isis/isis:database
          /isis:levels/isis:lsp:
    +--ro segment-routing-bindings* [fec range]
       +--ro fec                  string
       +--ro range                uint16
       +--ro flags?     bits sid-binding-flags
       |  +--ro bits*   identityref
       +--ro binding
          +--ro prefix-sid
             +--ro sid-list* [value]
                +--ro flags?       bits perfix-sid-flags
                |  +--ro bits*   identityref
                +--ro algorithm?          uint8
                +--ro value               uint32

5.  IS-IS Segment Routing configuration

5.1.  Segment Routing activation

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

5.2.  Advertising mapping server policy

   The base segment routing module defines mapping server policies.  By
   default, IS-IS will not advertise nor receive any mapping server
   entry.  The IS-IS segment-routing module allows to advertise one or
   multiple mapping server policies through the "bindings/advertise/
   policies" leaf-list.  The "bindings/receive" leaf allows to enable
   the reception of mapping server entries.

5.3.  IP Fast reroute

   IS-IS SR model augments the fast-reroute container under interface.
   It brings the ability to activate TI-LFA (topology independent LFA)
   and also enhances remote LFA to use segment-routing tunneling instead
   of LDP.

6.  IS-IS Segment Routing YANG Module

   <CODE BEGINS> file "ietf-isis-sr@2019-07-07.yang" "ietf-isis-sr@2020-01-09.yang"
   module ietf-isis-sr {
     namespace "urn:ietf:params:xml:ns:"
             + "yang:ietf-isis-sr";

     prefix isis-sr;

     import ietf-routing {
       prefix "rt";
     }

     import ietf-segment-routing-common {
       prefix "sr-cmn";
     }

     import ietf-segment-routing ietf-segment-routing-mpls {
       prefix "sr"; "sr-mpls";
     }

     import ietf-isis {
       prefix "isis";
     }

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

     organization
      "IETF LSR - LSR Working Group";

     contact
       "WG List:  <mailto:lsr@ietf.org>

       Editor:    Stephane Litkowski
                  <mailto:stephane.litkowski@orange.com>

       Author:    Acee Lindem
                  <mailto:acee@cisco.com>
       Author:    Yingzhen Qu
                  <mailto:yingzhen.qu@futurewei.com>
       Author:    Pushpasis Sarkar
                  <mailto:pushpasis.ietf@gmail.com>
       Author:    Ing-Wher Chen
                  <mailto:ingwherchen@mitre.org>
       Author:    Jeff Tantsura
                  <mailto:jefftant.ietf@gmail.com>
       ";

     description
       "The YANG module defines a generic configuration model for
        Segment routing ISIS extensions common across all of the vendor
      implementations.";
        implementations
        Copyright (c) 2020 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).

        This version of this YANG module is part of RFC XXXX;
        see the RFC itself for full legal notices.";

     reference "RFC XXXX";

     revision 2019-07-07 2020-01-09 {
     description
       "Initial revision.";
     reference "RFC XXXX";
     }

     /* Identities */

    /* Features */

    feature remote-lfa-sr {
      description
       "Enhance rLFA to use SR path.";
    }

    feature ti-lfa {
      description
       "Enhance IPFRR with ti-lfa
       support";
    }

    /* Groupings */

    grouping sid-sub-tlv
     identity sr-capability {
       description "SID/Label
         "Base identity for ISIS SR-Capabilities sub-TLV grouping.";
      container sid-sub-tlv {
        description
          "Used to advertise the SID/Label associated with a
        prefix or adjacency.";
        leaf sid {
          type uint32;
        description
          "Segment Identifier (SID) - A 20 bit label or
           32 bit SID."; flgs";
     }
      }
    }

    grouping sr-capability {
      description
        "SR capability grouping.";
      container sr-capability {
        description
          "Segment Routing capability.";
        leaf flags {
          type bits {
            bit

     identity mpls-ipv4 {
              position 0;
       base sr-capability;
       description
         "If set, then the router is capable of
          processing SR MPLS encapsulated IPv4 packets
          on all interfaces.";
     }
            bit

     identity mpls-ipv6 {
              position 1;
       base sr-capability;
       description
         "If set, then the router is capable of
          processing SR MPLS encapsulated IPv6 packets
          on all interfaces.";
     }
          }

     identity prefix-sid-bit {
       description
            "Flags.";
         "Base identity for prefix sid sub-tlv bits.";
     }
        container global-blocks
     identity r-bit {
       base prefix-sid-bit;
       description
            "Segment Routing Global Blocks.";
          list global-block
        "Re-advertisement Flag.";
     }

     identity n-bit {
       base prefix-sid-bit;
       description "Segment Routing Global Block.";
            leaf range-size
        "Node-SID Flag.";
     }

     identity p-bit {
              type uint32;
       base prefix-sid-bit;
       description "The SID range.";
            }
            uses sid-sub-tlv;
          }
        }
        "No-PHP (No Penultimate Hop-Popping) Flag.";
     }

     identity e-bit {
       base prefix-sid-bit;
       description
        "Explicit NULL Flag.";
     }

    grouping sr-algorithm

     identity v-bit {
       base prefix-sid-bit;
       description
        "Value Flag.";
     }

     identity l-bit {
       base prefix-sid-bit;
       description
        "Local Flag.";
     }

     identity adj-sid-bit {
       description
         "Base identity for adj sid sub-tlv bits.";
     }

     identity f-bit {
       base adj-sid-bit;
       description
         "Address-Family flag.";
     }

     identity b-bit {
       base adj-sid-bit;
       description
         "Backup flag.";
     }

     identity vi-bit {
       base adj-sid-bit;
       description
         "Value/Index flag.";
     }

     identity lo-bit {
       base adj-sid-bit;
       description
         "Local flag.";
     }

     identity s-bit {
       base adj-sid-bit;
       description
         "Group flag.";
     }

     identity pe-bit {
       base adj-sid-bit;
       description
         "Persistent flag.";
     }

     identity sid-binding-bit {
       description
         "Base identity for sid binding tlv bits.";
     }

     identity af-bit {
       base sid-binding-bit;
       description
         "Address-Family flag.";
     }

     identity m-bit {
       base sid-binding-bit;
       description
         "Mirror Context flag.";
     }

     identity sf-bit {
       base sid-binding-bit;
       description
         "S flag. If set, the binding label tlv should be flooded
          across the entire routing domain.";
     }

     identity d-bit {
       base sid-binding-bit;
       description
         "Leaking flag.";
     }

     identity a-bit {
       base sid-binding-bit;
       description
         "Attached flag.";
     }

     /* Features */

     feature remote-lfa-sr {
       description
        "Enhance rLFA to use SR path.";
     }

     feature ti-lfa {
       description
        "Enhance IPFRR with ti-lfa
        support";
     }

     /* Groupings */

     grouping sid-sub-tlv {
       description "SID/Label sub-TLV grouping.";
       container sid-sub-tlv {
         description
           "Used to advertise the SID/Label associated with a
         prefix or adjacency.";
         leaf sid {
           type uint32;
         description
           "Segment Identifier (SID) - A 20 bit label or
            32 bit SID.";
         }
       }
     }
     grouping sr-capability {
       description
         "SR capability grouping.";
       container sr-capability {
         description
           "Segment Routing capability.";
         container sr-capability {
           leaf-list sr-capability-bits {
             type identityref {
               base sr-capability;
             }
             description "SR Capbility sub-tlv flags list.";
           }
           description
             "SR Capability Flags.";
         }
         container global-blocks {
           description
             "Segment Routing Global Blocks.";
           list global-block {
             description "Segment Routing Global Block.";
             leaf range-size {
               type uint32;
               description "The SID range.";
             }
             uses sid-sub-tlv;
           }
         }
       }
     }

     grouping sr-algorithm {
       description
         "SR algorithm grouping.";
       container sr-algorithms {
         description "All SR algorithms.";
         leaf-list sr-algorithm {
           type uint8;
           description
             "The Segment Routing (SR) algorithms that the router is
              currently using.";
         }
       }
     }

     grouping srlb {
       description
         "SR Local Block grouping.";

       container local-blocks {
         description "List of SRLBs.";
         list local-block {
           description "Segment Routing Local Block.";
           leaf range-size {
             type uint32;
             description "The SID range.";
           }
           uses sid-sub-tlv;
         }
       }
     }

     grouping srms-preference {
       description "The SRMS preference TLV is used to advertise
                    a preference associated with the node that acts
                    as an SR Mapping Server.";
       container srms-preference {
         description "SRMS Preference TLV.";
         leaf preference {
           type uint8 {
             range "0 .. 255";
           }
           description "SRMS preference TLV, vlaue from 0 to 255.";
         }
       }
     }

     grouping adjacency-state {
       description
         "This group will extend adjacency state.";
       list adjacency-sid {
         key value;
         config false;
         leaf af {
           type iana-rt-types:address-family;
           description
             "Address-family associated with the
              segment ID";
         }
         leaf value {
           type uint32;
           description
             "Value of the Adj-SID.";
         }
         leaf weight {
           type uint8;
           description
             "Weight associated with
             the adjacency SID.";
         }
         leaf protection-requested {
           type boolean;
           description
             "Describe if the adjacency SID
              must be protected.";
         }
         description
           "List of adjacency Segment IDs.";
       }
     }

     grouping prefix-segment-id {
       description
         "This group defines segment routing extensions
          for prefixes.";

       list sid-list {
         key value;

        leaf flags

         container perfix-sid-flags {
          type
           leaf-list bits {
            bit readvertisment {
              position 7;
              description
                "If set, then the prefix to
                 which this Prefix-SID is attached,
                 has been propagated by the
                 router either from another level
                 or from redistribution.";
            }
            bit php {
              position 5;
              description
                "If set, then the penultimate hop MUST NOT
                 pop the Prefix-SID before delivering the packet
                 to the node that advertised the Prefix-SID.";
            }
            bit explicit-null {
              position 4;
              description
                "If set, any upstream neighbor of
                 the Prefix-SID originator MUST replace
                 the Prefix-SID with a
                 Prefix-SID having an
                 Explicit-NULL value (0 for IPv4 and 2 for
                 IPv6) before forwarding the packet.";
            }
            bit value
             type identityref {
              position 3;
              description
                "If set, then the Prefix-SID carries a
                 value (instead of an index).
                 By default the flag is UNSET.";
               base prefix-sid-bit;
             }
            bit local {
              position 2;
             description
                "If set, then the value/index carried by
                 the Prefix-SID has local significance.
                 By default the
               "Prefix SID Sub-TLV flag is UNSET.";
            } bits list.";
           }
           description
             "Describes flags associated with the
              segment ID.";
         }

         leaf algorithm {
           type uint8;
           description
             "Algorithm to be used for path computation.";
         }
        leaf value {
          type uint32;
          description
           "Value of the prefix-SID.";
        }
        description
          "List of segments.";
      }
    }

    grouping adjacency-segment-id {
      description
        "This group defines segment routing extensions
         for adjacencies.";

      list sid-list {
        key value;

        leaf flags {
          type bits {
            bit address-family {
              position 7;
              description
                "If unset, then the Adj-SID refers
                 to an adjacency with outgoing IPv4 encapsulation.
                 If set then the Adj-SID refers to an adjacency
                 with outgoing IPv6 encapsulation.";
            }
            bit backup {
              position 6;
              description
                "If set, the Adj-SID refers to an
                 adjacency being protected
                 (e.g.: using IPFRR or MPLS-FRR)";
            }
            bit value {
              position 5;
              description
                "If set, then the SID carries a
                 value (instead of an index).
                 By default the flag is SET.";
            }
            bit local
         leaf value {
              position 4;
           type uint32;
           description
                "If set, then the value/index carried by
                 the SID has local significance.
                 By default
            "Value of the flag is SET."; prefix-SID.";
         }
            bit set {
              position 3;
         description
                "When set, the S-Flag indicates that the
                 Adj-SID refers to a set
           "List of adjacencies."; segments.";
       }
            bit persistent

     }

     grouping adjacency-segment-id {
              position 2;
       description
                "When set, the P-Flag indicates that the
                 Adj-SID is persistently allocated.";
            }
         "This group defines segment routing extensions
          for adjacencies.";

       list sid-list {
         key value;

         container adj-sid-flags {
           leaf-list bits {
             type identityref {
               base adj-sid-bit;
             }
             description
            "Describes "Adj sid sub-tlv flags associated with the
             segment ID."; list.";
             }
           description "Adj-sid sub-tlv flags.";
         }

         leaf weight {
           type uint8;
           description
             "The value represents the weight of the Adj-SID
              for the purpose of load balancing.";
         }
         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.";
         }
         leaf value {
           type uint32;
           description
             "Value of the Adj-SID.";
         }
         description
           "List of segments.";
       }
     }

     grouping segment-routing-binding-tlv {
       list segment-routing-bindings {
         key "fec range";

         leaf fec {
           type string;
           description
           "IP (v4 or v6) range to be bound to SIDs.";
         }

         leaf range {
           type uint16;
           description
             "Describes number of elements to assign
              a binding to.";
         }

        leaf flags

         container sid-binding-flags {
          type
           leaf-list bits {
            bit address-family {
              position 7;
              description
                "If unset, then the Prefix FEC
                 carries an IPv4 Prefix.
                 If set then the Prefix FEC carries an
                 IPv6 Prefix.";

            }
            bit mirror {
              position 6;
              description
                "Set if the advertised SID/path
                 corresponds to a mirrored context.";
            }
            bit flooding {
              position 5;
              description
                "If the S bit is set(1),
                 the IS-IS Router CAPABILITY TLV
                 MUST be flooded across the entire routing domain.
                 If the S bit is
                 not set(0), the TLV MUST NOT be leaked between levels.
                 This bit MUST NOT be altered during the TLV leaking.";
            }
            bit down
             type identityref {
              position 4;
              description
                "When the IS-IS Router CAPABILITY TLV is
                 leaked from level-2 to level-1, the D bit
                 MUST be set.  Otherwise, this bit MUST
                 be clear.  IS-IS Router capability TLVs
                 with the D bit set MUST NOT
                 be leaked from level-1 to level-2.
                 This is to prevent TLV looping.";
               base sid-binding-bit;
             }
            bit attached {
              position 3;
             description
                "The originator of the SID/Label Binding TLV MAY set the
                 A bit in order to signal that the prefixes and SIDs
                 advertised in the SID/Label
               "SID Binding TLV are directly
                 connected to their originators.";
            } flag bits list.";
           }
           description
            "Flags of the binding.";
             "Binding flags.";
         }

         container binding {
           container prefix-sid {
             uses prefix-segment-id;
             description
               "Binding prefix SID to the range.";
           }
           description
             "Bindings associated with the range.";
         }

         description
           "This container describes list of SID/Label bindings.
            ISIS reference is TLV 149.";
       }
       description
         "Defines binding TLV for database.";
     }

     /* 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 segment routing.";

       uses sr:sr-controlplane; sr-mpls:sr-controlplane;
       container protocol-srgb {
         if-feature sr:protocol-srgb; sr-mpls:protocol-srgb;
         uses sr-cmn:srgb;
         description
           "Per-protocol SRGB.";
       }
     }

     augment "/rt:routing/" +
             "rt:control-plane-protocols/rt:control-plane-protocol"+
             "/isis:isis/isis:interfaces/isis:interface" {
       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 segment routing.";

       uses sr:igp-interface; sr-mpls:igp-interface;
     }

     augment "/rt:routing/" +
             "rt:control-plane-protocols/rt:control-plane-protocol"+
             "/isis:isis/isis:interfaces/isis:interface"+
             "/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 IP FRR with TILFA.";

       container ti-lfa {
         if-feature ti-lfa;
         leaf enable {
           type boolean;
           description
             "Enables TI-LFA computation.";
         }
         description
           "TILFA configuration.";
       }
     }

     augment "/rt:routing/" +
             "rt:control-plane-protocols/rt:control-plane-protocol"+
             "/isis:isis/isis:interfaces/isis:interface"+
             "/isis:fast-reroute/isis:lfa/isis:remote-lfa" {
       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 remoteLFA config with
          use of segment-routing path.";

       leaf use-segment-routing-path {
         if-feature remote-lfa-sr;
         type boolean;
         description
           "force remote LFA to use segment routing
            path instead of LDP path.";
       }
     }

     /* Operational states */

     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 configuration
          with segment routing.";

       uses adjacency-state;
     }
     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 LSDB router capability.";

       uses sr-capability;
       uses sr-algorithm;
       uses srlb;
       uses srms-preference;
     }

     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" {
       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 LSDB neighbor.";
          uses adjacency-segment-id;
     }

     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 LSDB neighbor.";
          uses adjacency-segment-id;
     }

     augment "/rt:routing/" +
             "rt:control-plane-protocols/rt:control-plane-protocol"+
             "/isis:isis/isis:database/isis:levels/isis:lsp"+
             "/isis:extended-ipv4-reachability/isis:prefixes" {
       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 LSDB prefix.";
          uses prefix-segment-id;
     }

     augment "/rt:routing/" +
             "rt:control-plane-protocols/rt:control-plane-protocol"+
             "/isis:isis/isis:database/isis:levels/isis:lsp"+
             "/isis:mt-extended-ipv4-reachability/isis:prefixes" {
       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 LSDB prefix.";
       uses prefix-segment-id;
     }

     augment "/rt:routing/" +
             "rt:control-plane-protocols/rt:control-plane-protocol"+
             "/isis:isis/isis:database/isis:levels/isis:lsp"+
             "/isis:ipv6-reachability/isis:prefixes" {
       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 LSDB prefix.";
       uses prefix-segment-id;
     }

     augment "/rt:routing/" +
             "rt:control-plane-protocols/rt:control-plane-protocol"+
             "/isis:isis/isis:database/isis:levels/isis:lsp"+
             "/isis:mt-ipv6-reachability/isis:prefixes" {
       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 LSDB prefix.";
       uses prefix-segment-id;
     }

     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
           "This augment ISIS routing protocol when used";
       }
       description
         "This augments ISIS protocol LSDB.";
       uses segment-routing-binding-tlv;
     }

     /* Notifications */

   }
   <CODE ENDS>

7.  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.

8.  Contributors

   Authors would like to thank Derek Yeung, Acee Lindem, Yi Yang for
   their major contributions to the draft.

9.  Acknowledgements

   Author affiliation with The MITRE Corporation is provided for
   identification purposes only, and is not intended to convey or imply
   MITRE's concurrence with, or support for, the positions, opinions or
   viewpoints expressed.

   MITRE has approved this document for Public Release, Distribution
   Unlimited, with Public Release Case Number
   18-3281. 19-3033.

10.  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-sr
           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-sr
           namespace: urn:ietf:params:xml:ns:yang:ietf-isis-sr
           prefix: isis-sr
           reference: RFC XXXX

11.  Change log for ietf-isis-sr YANG module

11.1.  From version -03 to version -04

   o  Fixed yang module indentations.

11.2.  From version -02 to version -03

   o  Change address-family type according to routing types.

11.3.  From isis-sr document version -01 to version -02

   o  NMDA compliancy.

   o  Added SRLB in configuration and LSDB.

   o  Added SR capability in LSDB.

   o  Added SR algorithms in LSDB.

   o  Added SRMS preference in LSDB.

   o  Alignment with iana-rt-types module.

   o  Align binding SID with draft-ietf-isis-segment-routing-extensions-
      13.

11.4.  From isis-sr document version -00 to version -01

   o  Added P-Flag in Adj-SID.

11.5.  From isis document version -12 to isis-sr document version -00

   o  Separate document for IS-IS SR extensions.

11.6.  From isis document version -12 to version -13

   o  Align with new segment routing common module.

11.7.  From isis document version -09 to version -11

   o  Fixed XPATH in 'when' expressions.

11.8.  From isis document version -08 to version -09

   o  Align to draft-ietf-netmod-routing-cfg-23.

11.9.  From isis document version -07 to version -08

   o  Align to draft-ietf-netmod-routing-cfg-21.

12.  Normative References

   [I-D.ietf-isis-segment-routing-extensions]
              Previdi, S., Ginsberg, L., Filsfils, C., Bashandy, A.,
              Gredler, H., Litkowski, S., Decraene, B., and J. Tantsura,
              "IS-IS Extensions for Segment Routing", draft-ietf-isis-
              segment-routing-extensions-22 (work in progress).

   [I-D.ietf-isis-yang-isis-cfg]
              Litkowski, S., Yeung, D., Lindem, A., Zhang, Z., and L.
              Lhotka, "YANG Data Model for IS-IS Protocol", draft-ietf-
              isis-yang-isis-cfg-35
              isis-yang-isis-cfg-42 (work in progress), March October 2019.

   [I-D.ietf-spring-sr-yang]
              Litkowski, S., Qu, Y., Sarkar, P., and J. Tantsura, "YANG
              Data Model for Segment Routing", draft-ietf-spring-sr-
              yang-08
              yang-15 (work in progress), December 2017.

   [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>.

   [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>.

   [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>.

   [RFC8340]  Bjorklund, M. and L. Berger, Ed., "YANG Tree Diagrams",
              BCP 215, RFC 8340, DOI 10.17487/RFC8340, March 2018,
              <https://www.rfc-editor.org/info/rfc8340>.

   [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>.

   [RFC8667]  Previdi, S., Ed., Ginsberg, L., Ed., Filsfils, C.,
              Bashandy, A., Gredler, H., and B. Decraene, "IS-IS
              Extensions for Segment Routing", RFC 8667,
              DOI 10.17487/RFC8667, December 2019,
              <https://www.rfc-editor.org/info/rfc8667>.

Authors' Addresses

   Stephane Litkowski
   Orange
   Cisco Systems

   Email: stephane.litkowski@orange.com slitkows.ietf@gmail.com
   Yinghzen Qu
   Futurewei

   Email: yingzhen.qu@Futurewei.com yingzhen.qu@futurewei.com

   Pushpasis Sarkar
   Individual

   Email: pushpasis.ietf@gmail.com

   Ing-Wher Chen
   The MITRE Corporation

   Email: ingwherchen@mitre.org

   Jeff Tantsura
   Individual
   Apstra

   Email: jefftant.ietf@gmail.com