Skip to main content

YANG Data Model for IS-IS Segment Routing
draft-ietf-isis-sr-yang-12

Document Type Active Internet-Draft (lsr WG)
Authors Stephane Litkowski , Yingzhen Qu , Pushpasis Sarkar , Ing-Wher Chen , Jeff Tantsura
Last updated 2022-02-09
Stream Internet Engineering Task Force (IETF)
Intended RFC status Proposed Standard
Formats plain text html xml htmlized pdfized bibtex
Yang Validation 0 errors, 2 warnings
Additional resources Yang catalog entry for ietf-isis-sr@2020-07-12.yang
Yang impact analysis for draft-ietf-isis-sr-yang
Mailing list discussion
Stream WG state WG Document
Document shepherd Christian Hopps
IESG IESG state I-D Exists
Consensus boilerplate Yes
Telechat date (None)
Responsible AD (None)
Send notices to Christian Hopps <chopps@chopps.org>
draft-ietf-isis-sr-yang-12
LSR Working Group                                           S. Litkowski
Internet-Draft                                             Cisco Systems
Intended status: Standards Track                                   Y. Qu
Expires: 13 August 2022                                        Futurewei
                                                               P. Sarkar
                                                              Individual
                                                                 I. Chen
                                                   The MITRE Corporation
                                                             J. Tantsura
                                                               Microsoft
                                                         9 February 2022

               YANG Data Model for IS-IS Segment Routing
                       draft-ietf-isis-sr-yang-12

Abstract

   This document defines a YANG data module that can be used to
   configure and manage IS-IS Segment Routing, as well as a YANG data
   module for the management of Signaling Maximum SID Depth (MSD) using
   IS-IS.

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 13 August 2022.

Copyright Notice

   Copyright (c) 2022 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.

Litkowski, et al.        Expires 13 August 2022                 [Page 1]
Internet-Draft                isis-sr-yang                 February 2022

   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 Revised BSD License text as
   described in Section 4.e of the Trust Legal Provisions and are
   provided without warranty as described in the Revised BSD License.

Table of Contents

   1.  Overview  . . . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Requirements Language . . . . . . . . . . . . . . . . . .   3
     1.2.  Tree Diagrams . . . . . . . . . . . . . . . . . . . . . .   3
   2.  IS-IS MSD . . . . . . . . . . . . . . . . . . . . . . . . . .   3
     2.1.  IS-IS MSD YANG Module . . . . . . . . . . . . . . . . . .   3
   3.  IS-IS Segment Routing . . . . . . . . . . . . . . . . . . . .   7
     3.1.  IS-IS Segment Routing configuration . . . . . . . . . . .  10
       3.1.1.  Segment Routing activation  . . . . . . . . . . . . .  10
       3.1.2.  Advertising mapping server policy . . . . . . . . . .  10
       3.1.3.  IP Fast reroute . . . . . . . . . . . . . . . . . . .  11
     3.2.  IS-IS Segment Routing YANG Module . . . . . . . . . . . .  11
   4.  Security Considerations . . . . . . . . . . . . . . . . . . .  26
   5.  Contributors  . . . . . . . . . . . . . . . . . . . . . . . .  27
   6.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  27
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  27
   8.  Normative References  . . . . . . . . . . . . . . . . . . . .  27
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  29

1.  Overview

   YANG [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 module that can be used to
   configure and manage IS-IS Segment Routing [RFC8667] and it is an
   augmentation to the IS-IS YANG data model.

   This document also defines a YANG data module for the management of
   Signaling Maximum SID Depth (MSD) using IS-IS [RFC8491], which
   augments the base IS-IS YANG data model.

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

Litkowski, et al.        Expires 13 August 2022                 [Page 2]
Internet-Draft                isis-sr-yang                 February 2022

1.1.  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.

1.2.  Tree Diagrams

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

2.  IS-IS MSD

   This document defines a module for Signaling Maximum SID Depth (MSD)
   using IS-IS[RFC8667].  It is an augmentation of the IS-IS base model.

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

   module: ietf-isis-msd
     augment /rt:routing/rt:control-plane-protocols
             /rt:control-plane-protocol/isis:isis/isis:database
             /isis:levels/isis:lsp/isis:router-capabilities:
       +--ro node-msd-tlv
          +--ro node-msds* [msd-type]
             +--ro msd-type     identityref
             +--ro msd-value?   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 link-msd-sub-tlv
          +--ro link-msds* [msd-type]
             +--ro msd-type     identityref
             +--ro msd-value?   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 link-msd-sub-tlv
          +--ro link-msds* [msd-type]
             +--ro msd-type     identityref
             +--ro msd-value?   uint8

2.1.  IS-IS MSD YANG Module

Litkowski, et al.        Expires 13 August 2022                 [Page 3]
Internet-Draft                isis-sr-yang                 February 2022

   <CODE BEGINS> file "ietf-isis-msd@2022-02-09.yang"
   module ietf-isis-msd {
     yang-version 1.1;
     namespace "urn:ietf:params:xml:ns:yang:ietf-isis-msd";
     prefix isis-msd;

     import ietf-routing {
       prefix rt;
       reference "RFC 8349: A YANG Data Model for Routing
                  Management (NMDA Version)";
     }

     import ietf-isis {
       prefix isis;
     }

     import ietf-mpls-msd {
       prefix mpls-msd;
     }

     organization
       "IETF LSR - LSR Working Group";
     contact
       "WG Web:   <https://tools.ietf.org/wg/mpls/>
        WG List:  <mailto:mpls@ietf.org>

        Author:    Yingzhen Qu
                  <mailto:yingzhen.qu@futurewei.com>
        Author:    Acee Lindem
                  <mailto:acee@cisco.com>
        Author:    Stephane Litkowski
                  <mailto:slitkows.ietf@gmail.com>
        Author:    Jeff Tantsura
                  <mailto:jefftant.ietf@gmail.com>

       ";
     description
       "The YANG module augments the base ISIS model to
        manage different types of MSDs.

        This YANG model conforms to the Network Management
        Datastore Architecture (NMDA) as described in RFC 8342.

        Copyright (c) 2022 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

Litkowski, et al.        Expires 13 August 2022                 [Page 4]
Internet-Draft                isis-sr-yang                 February 2022

        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
        (https://trustee.ietf.org/license-info).

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

        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 (RFC 2119) (RFC 8174) when, and only when,
        they appear in all capitals, as shown here.";

     reference "RFC XXXX: YANG Data Model for OSPF MSD.";

     revision 2022-02-09 {
       description
         "Initial Version";
       reference "RFC XXXX: YANG Data Model for ISIS MSD.";
     }

     grouping link-msd-sub-tlv {
       description
         "Link Maximum SID Depth (MSD) grouping for an interface.";
       container link-msd-sub-tlv {
         list link-msds {
           key "msd-type";
           leaf msd-type {
             type identityref {
               base mpls-msd:msd-base-type;
             }
             description
               "MSD-Types";
           }
           leaf msd-value {
             type uint8;
             description
               "MSD value, in the range of 0-255.";
           }
           description
             "List of link MSDs";
         }
         description
           "Link MSD sub-tlvs.";
       }
     }

Litkowski, et al.        Expires 13 August 2022                 [Page 5]
Internet-Draft                isis-sr-yang                 February 2022

     /* Node MSD TLV */
     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.";
       container node-msd-tlv {
         list node-msds {
           key "msd-type";
           leaf msd-type {
             type identityref {
             base mpls-msd:msd-base-type;
             }
             description
               "MSD-Types";
           }
           leaf msd-value {
             type uint8;
             description
               "MSD value, in the range of 0-255.";
           }
           description
             "Node MSD is the smallest link MSD supported by
              the node.";
         }
         description
           "Node MSD is the number of SIDs supported by a node.";
         reference
           "RFC 8476: Signaling Maximum SID Depth (MSD) Using OSPF";
       }
     }

     /* link MSD sub-tlv */
     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";

Litkowski, et al.        Expires 13 August 2022                 [Page 6]
Internet-Draft                isis-sr-yang                 February 2022

       }
       description
         "This augments ISIS protocol LSDB neighbor with
          Link MSD sub-TLV.";

       uses link-msd-sub-tlv;
     }

     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 link-msd-sub-tlv;
     }
   }
   <CODE ENDS>

3.  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

Litkowski, et al.        Expires 13 August 2022                 [Page 7]
Internet-Draft                isis-sr-yang                 February 2022

    |     +--rw receive?     boolean
    +--rw 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 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

Litkowski, et al.        Expires 13 August 2022                 [Page 8]
Internet-Draft                isis-sr-yang                 February 2022

    |  +--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:
    +--ro sid-list* [value]
       +--ro 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 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 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 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 perfix-sid-flags
       |  +--ro bits*   identityref

Litkowski, et al.        Expires 13 August 2022                 [Page 9]
Internet-Draft                isis-sr-yang                 February 2022

       +--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:
    +--ro sid-list* [value]
       +--ro 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 sid-binding-flags
       |  +--ro bits*   identityref
       +--ro binding
          +--ro prefix-sid
             +--ro sid-list* [value]
                +--ro perfix-sid-flags
                |  +--ro bits*   identityref
                +--ro algorithm?          uint8
                +--ro value               uint32

3.1.  IS-IS Segment Routing configuration

3.1.1.  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.

3.1.2.  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.

Litkowski, et al.        Expires 13 August 2022                [Page 10]
Internet-Draft                isis-sr-yang                 February 2022

3.1.3.  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.

3.2.  IS-IS Segment Routing YANG Module

   <CODE BEGINS> file "ietf-isis-sr@2022-02-09.yang"
   module ietf-isis-sr {
     yang-version 1.1;
     namespace "urn:ietf:params:xml:ns:"
             + "yang:ietf-isis-sr";
     prefix isis-sr;

     import ietf-routing {
       prefix "rt";
       reference
         "RFC 8349 - A YANG Data Model for Routing
                     Management (NMDA Version)";
     }

     import ietf-segment-routing-common {
       prefix "sr-cmn";
       reference
         "RFC 9020 - YANG Data Model for Segment Routing";
     }

     import ietf-segment-routing-mpls {
       prefix "sr-mpls";
       reference
         "RFC 9020 - YANG Data Model for Segment Routing";
     }

     import ietf-isis {
       prefix "isis";
     }

     import iana-routing-types {
       prefix "iana-rt-types";
       reference "RFC 8294 - Common YANG Data Types for the
                  Routing Area";
     }

     organization
      "IETF LSR - LSR Working Group";

Litkowski, et al.        Expires 13 August 2022                [Page 11]
Internet-Draft                isis-sr-yang                 February 2022

     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.

       This YANG model conforms to the Network Management
       Datastore Architecture (NMDA) as described in RFC 8342.

       Copyright (c) 2022 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
       (https://trustee.ietf.org/license-info).

       This version of this YANG module is part of RFC XXXX
       (https://www.rfc-editor.org/info/rfcXXXX); see the RFC itself
       for full legal notices.

       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 (RFC 2119) (RFC 8174) when, and only when,
       they appear in all capitals, as shown here.

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

Litkowski, et al.        Expires 13 August 2022                [Page 12]
Internet-Draft                isis-sr-yang                 February 2022

     reference "RFC XXXX";

     revision 2022-02-09 {
     description
       "Initial revision.";
     reference "RFC XXXX";
     }

     /* Identities */
     identity sr-capability {
       description
         "Base identity for ISIS SR-Capabilities sub-TLV flgs";
     }

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

     identity mpls-ipv6 {
       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
         "Base identity for prefix sid sub-tlv bits.";
     }

     identity r-bit {
       base prefix-sid-bit;
       description
        "Re-advertisement Flag.";
     }

     identity n-bit {
       base prefix-sid-bit;
       description
        "Node-SID Flag.";
     }

Litkowski, et al.        Expires 13 August 2022                [Page 13]
Internet-Draft                isis-sr-yang                 February 2022

     identity p-bit {
       base prefix-sid-bit;
       description
        "No-PHP (No Penultimate Hop-Popping) Flag.";
     }

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

     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 {

Litkowski, et al.        Expires 13 August 2022                [Page 14]
Internet-Draft                isis-sr-yang                 February 2022

       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 {

Litkowski, et al.        Expires 13 August 2022                [Page 15]
Internet-Draft                isis-sr-yang                 February 2022

       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.";

Litkowski, et al.        Expires 13 August 2022                [Page 16]
Internet-Draft                isis-sr-yang                 February 2022

           }
           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;
         }
       }
     }

Litkowski, et al.        Expires 13 August 2022                [Page 17]
Internet-Draft                isis-sr-yang                 February 2022

     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.";
       }
     }

Litkowski, et al.        Expires 13 August 2022                [Page 18]
Internet-Draft                isis-sr-yang                 February 2022

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

       list sid-list {
         key value;

         container perfix-sid-flags {
           leaf-list bits {
             type identityref {
               base prefix-sid-bit;
             }
             description
               "Prefix SID Sub-TLV flag 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;

         container adj-sid-flags {
           leaf-list bits {
             type identityref {
               base adj-sid-bit;

Litkowski, et al.        Expires 13 August 2022                [Page 19]
Internet-Draft                isis-sr-yang                 February 2022

             }
             description "Adj sid sub-tlv flags 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.";
         }

         container sid-binding-flags {
           leaf-list bits {

Litkowski, et al.        Expires 13 August 2022                [Page 20]
Internet-Draft                isis-sr-yang                 February 2022

             type identityref {
               base sid-binding-bit;
             }
             description
               "SID Binding TLV flag bits list.";
           }
           description
             "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-mpls:sr-control-plane;
       container protocol-srgb {
         if-feature sr-mpls:protocol-srgb;
         uses sr-cmn:srgb;
         description
           "Per-protocol SRGB.";

Litkowski, et al.        Expires 13 August 2022                [Page 21]
Internet-Draft                isis-sr-yang                 February 2022

       }
     }

     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-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'" {

Litkowski, et al.        Expires 13 August 2022                [Page 22]
Internet-Draft                isis-sr-yang                 February 2022

         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;

Litkowski, et al.        Expires 13 August 2022                [Page 23]
Internet-Draft                isis-sr-yang                 February 2022

       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"+

Litkowski, et al.        Expires 13 August 2022                [Page 24]
Internet-Draft                isis-sr-yang                 February 2022

             "/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";
       }

Litkowski, et al.        Expires 13 August 2022                [Page 25]
Internet-Draft                isis-sr-yang                 February 2022

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

     /* Notifications */
   }
   <CODE ENDS>

4.  Security Considerations

   The YANG module specified in this document defines a schema for data
   that is designed to be accessed via network management protocols such
   as NETCONF [RFC6241] or RESTCONF [RFC8040].  The lowest NETCONF layer
   is the secure transport layer, and the mandatory-to-implement secure
   transport is Secure Shell (SSH) [RFC6242].  The lowest RESTCONF layer
   is HTTPS, and the mandatory-to-implement secure transport is TLS
   [RFC8446].

   The NETCONF Access Control Model (NACM) [RFC8341] provides the means
   to restrict access for particular NETCONF or RESTCONF users to a pre-
   configured subset of all available NETCONF or RESTCONF protocol
   operations and content.

   There are a number of data nodes defined in this YANG module that are
   writable/creatable/deletable (i.e., config true, which is the
   default).  These data nodes may be considered sensitive or vulnerable
   in some network environments.  Write operations (e.g., edit-config)
   to these data nodes without proper protection can have a negative
   effect on network operations.  These are the subtrees and data nodes
   and their sensitivity/vulnerability:

      /isis:isis/segment-routing

      /isis:isis/protocol-srgb

      /isis:isis/isis:interfaces/isis:interface/segment-routing

   Some of the readable data nodes in the modules may be considered
   sensitive or vulnerable in some network environments.  It is thus
   important to control read access (e.g., via get, get-config, or
   notification) to these data nodes.

      /isis:router-capabilities/sr-capability

      /isis:router-capabilities/sr-algorithms

Litkowski, et al.        Expires 13 August 2022                [Page 26]
Internet-Draft                isis-sr-yang                 February 2022

      /isis:router-capabilities/local-blocks

      /isis:router-capabilities/srms-preference

      /isis:router-capabilities/node-msd-tlv

      And the augmentations to the ISIS link state database.

   Unauthorized access to any data node of these subtrees can disclose
   the operational state information of IS-IS protocol on this device.

5.  Contributors

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

6.  Acknowledgements

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

7.  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: The IESG.
           XML: N/A, the requested URI is an XML namespace

     URI: urn:ietf:params:xml:ns:yang:ietf-isis-msd
     Registrant Contact: The IESG.
     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

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

8.  Normative References

Litkowski, et al.        Expires 13 August 2022                [Page 27]
Internet-Draft                isis-sr-yang                 February 2022

   [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-spring-sr-yang]
              Litkowski, S., Qu, Y., Sarkar, P., and J. Tantsura, "YANG
              Data Model for Segment Routing", Work in Progress,
              Internet-Draft, draft-ietf-spring-sr-yang-15, 28 December
              2017, <http://www.ietf.org/internet-drafts/draft-ietf-
              spring-sr-yang-15.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>.

   [RFC6242]  Wasserman, M., "Using the NETCONF Protocol over Secure
              Shell (SSH)", RFC 6242, DOI 10.17487/RFC6242, June 2011,
              <https://www.rfc-editor.org/info/rfc6242>.

   [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>.

Litkowski, et al.        Expires 13 August 2022                [Page 28]
Internet-Draft                isis-sr-yang                 February 2022

   [RFC8040]  Bierman, A., Bjorklund, M., and K. Watsen, "RESTCONF
              Protocol", RFC 8040, DOI 10.17487/RFC8040, January 2017,
              <https://www.rfc-editor.org/info/rfc8040>.

   [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>.

   [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>.

   [RFC8446]  Rescorla, E., "The Transport Layer Security (TLS) Protocol
              Version 1.3", RFC 8446, DOI 10.17487/RFC8446, August 2018,
              <https://www.rfc-editor.org/info/rfc8446>.

   [RFC8491]  Tantsura, J., Chunduri, U., Aldrin, S., and L. Ginsberg,
              "Signaling Maximum SID Depth (MSD) Using IS-IS", RFC 8491,
              DOI 10.17487/RFC8491, November 2018,
              <https://www.rfc-editor.org/info/rfc8491>.

   [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
   Cisco Systems

   Email: slitkows.ietf@gmail.com

   Yingzhen Qu
   Futurewei

Litkowski, et al.        Expires 13 August 2022                [Page 29]
Internet-Draft                isis-sr-yang                 February 2022

   Email: yingzhen.qu@futurewei.com

   Pushpasis Sarkar
   Individual

   Email: pushpasis.ietf@gmail.com

   Ing-Wher Chen
   The MITRE Corporation

   Email: ingwherchen@mitre.org

   Jeff Tantsura
   Microsoft

   Email: jefftant.ietf@gmail.com

Litkowski, et al.        Expires 13 August 2022                [Page 30]