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A YANG Data Model for IS-IS Segment Routing for the MPLS Data Plane
draft-ietf-isis-sr-yang-21

Document Type Active Internet-Draft (lsr WG)
Authors Stephane Litkowski , Yingzhen Qu , Pushpasis Sarkar , Ing-Wher (Helen) Chen , Jeff Tantsura
Last updated 2024-01-22
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draft-ietf-isis-sr-yang-21
LSR Working Group                                           S. Litkowski
Internet-Draft                                             Cisco Systems
Intended status: Standards Track                                   Y. Qu
Expires: 25 July 2024                             Futurewei Technologies
                                                               P. Sarkar
                                                              Individual
                                                                 I. Chen
                                                   The MITRE Corporation
                                                             J. Tantsura
                                                                  Nvidia
                                                         22 January 2024

  A YANG Data Model for IS-IS Segment Routing for the MPLS Data Plane
                       draft-ietf-isis-sr-yang-21

Abstract

   This document defines a YANG data module that can be used to
   configure and manage IS-IS Segment Routing for MPLS data plane.

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 25 July 2024.

Copyright Notice

   Copyright (c) 2024 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

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   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 . . . . . . . . . . . . . . . . . .   2
     1.2.  Tree Diagrams . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Design of the IS-IS MPLS Segment Routing Module . . . . . . .   3
     2.1.  Segment Routing Activation  . . . . . . . . . . . . . . .   3
     2.2.  Advertising Mapping Server Policy . . . . . . . . . . . .   3
     2.3.  IP Fast Reroute . . . . . . . . . . . . . . . . . . . . .   3
   3.  IS-IS MPLS Segment Routing Module Tree  . . . . . . . . . . .   3
   4.  IS-IS MPLS Segment Routing YANG Module  . . . . . . . . . . .   7
   5.  Security Considerations . . . . . . . . . . . . . . . . . . .  26
   6.  Contributors  . . . . . . . . . . . . . . . . . . . . . . . .  27
   7.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  27
   8.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  28
   9.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  28
     9.1.  Normative References  . . . . . . . . . . . . . . . . . .  28
     9.2.  Informative References  . . . . . . . . . . . . . . . . .  30
   Appendix A.  A Configuration Example  . . . . . . . . . . . . . .  30
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  32

1.  Overview

   This document defines a YANG data model [RFC7950] that can be used to
   configure and manage IS-IS Segment Routing [RFC8667] for MPLS data
   plane and it is an augmentation to the IS-IS YANG data model
   [RFC9130].

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

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].

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2.  Design of the IS-IS MPLS Segment Routing Module

   This document defines a YANG model for IS-IS Segment Routing for the
   MPLS data plane.  It is an augmentation of the IS-IS base model.

   The IS-IS SR MPLS YANG module requires support for the base segment
   routing module [RFC9020], which defines the global segment routing
   configuration independent of any specific routing protocol
   configuration, and support of IS-IS base model [RFC9130] which
   defines basic IS-IS configuration and state.

2.1.  Segment Routing Activation

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

2.2.  Advertising Mapping Server Policy

   The base segment routing module defines mapping server policies.  By
   default, IS-IS will not advertise or process any mapping server
   entry.  The IS-IS SR MPLS module allows the advertisement of one or
   multiple mapping server policies through the "bindings/advertise/
   policies" leaf-list.  The "bindings/receive" leaf controls the
   reception and process of mapping server entries.

2.3.  IP Fast Reroute

   IS-IS SR MPLS 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.  IS-IS MPLS Segment Routing Module Tree

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

   module: ietf-isis-sr-mpls
     augment /rt:routing/rt:control-plane-protocols
             /rt:control-plane-protocol/isis:isis:
       +--rw segment-routing
       |  +--rw enabled?    boolean
       |  +--rw bindings {mapping-server}?
       |     +--rw advertise
       |     |  +--rw policies*   -> /rt:routing/sr:segment-routing
       |     |                       /sr-mpls:sr-mpls/bindings

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       |     |                       /mapping-server/policy/name
       |     +--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 weight?               uint8
             |  +--rw neighbor-system-id    isis:system-id
             +--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/isis:lfa:
       +--rw ti-lfa {ti-lfa}?
          +--rw enabled?                  boolean
          +--rw selection-tie-breakers
             +--rw node-protection!
             |  +--rw priority?   uint8
             +--rw srlg-disjoint!
                +--rw priority?   uint8
     augment /rt:routing/rt:control-plane-protocols
             /rt:control-plane-protocol/isis:isis/isis:interfaces
             /isis:interface/isis:fast-reroute/isis:lfa/isis:level-1:
       +--rw ti-lfa {ti-lfa}?
          +--rw enabled?   boolean
     augment /rt:routing/rt:control-plane-protocols
             /rt:control-plane-protocol/isis:isis/isis:interfaces
             /isis:interface/isis:fast-reroute/isis:lfa/isis:level-2:
       +--rw ti-lfa {ti-lfa}?
          +--rw enabled?   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]

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          +--ro value                   uint32
          +--ro address-family?         iana-rt-types:address-family
          +--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-flags*   identityref
       |  +--ro global-blocks
       |     +--ro global-block* []
       |        +--ro range-size?    uint32
       |        +--ro sid-sub-tlv
       |           +--ro length?   uint8
       |           +--ro sid?      uint32
       +--ro sr-algorithms
       |  +--ro sr-algorithm*   identityref
       +--ro local-blocks
       |  +--ro local-block* []
       |     +--ro range-size?    rt-types:uint24
       |     +--ro sid-sub-tlv
       |        +--ro length?   uint8
       |        +--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* [sid]
          +--ro adj-sid-flags
          |  +--ro flags*   identityref
          +--ro weight?          uint8
          +--ro neighbor-id?     isis:system-id
          +--ro sid              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* [sid]
          +--ro adj-sid-flags
          |  +--ro flags*   identityref
          +--ro weight?          uint8
          +--ro neighbor-id?     isis:system-id
          +--ro sid              uint32
     augment /rt:routing/rt:control-plane-protocols
             /rt:control-plane-protocol/isis:isis/isis:database
             /isis:levels/isis:lsp/isis:extended-ipv4-reachability

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             /isis:prefixes:
       +--ro prefix-sid-sub-tlvs
          +--ro prefix-sid-sub-tlv* [sid]
             +--ro prefix-sid-flags
             |  +--ro flags*   identityref
             +--ro algorithm?          identityref
             +--ro sid                 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 prefix-sid-sub-tlvs
          +--ro prefix-sid-sub-tlv* [sid]
             +--ro prefix-sid-flags
             |  +--ro flags*   identityref
             +--ro algorithm?          identityref
             +--ro sid                 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 prefix-sid-sub-tlvs
          +--ro prefix-sid-sub-tlv* [sid]
             +--ro prefix-sid-flags
             |  +--ro flags*   identityref
             +--ro algorithm?          identityref
             +--ro sid                 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 prefix-sid-sub-tlvs
          +--ro prefix-sid-sub-tlv* [sid]
             +--ro prefix-sid-flags
             |  +--ro flags*   identityref
             +--ro algorithm?          identityref
             +--ro sid                 uint32
     augment /rt:routing/rt:control-plane-protocols
             /rt:control-plane-protocol/isis:isis/isis:database
             /isis:levels/isis:lsp:
       +--ro sid-binding-tlvs
       |  +--ro sid-binding-tlv* [prefix]
       |     +--ro prefix                 inet:ip-prefix
       |     +--ro range?                 uint16
       |     +--ro sid-binding-flags
       |     |  +--ro flags*   identityref
       |     +--ro prefix-sid-sub-tlvs* []
       |     |  +--ro prefix-sid-sub-tlvs
       |     |     +--ro prefix-sid-sub-tlv* [sid]

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       |     |        +--ro prefix-sid-flags
       |     |        |  +--ro flags*   identityref
       |     |        +--ro algorithm?          identityref
       |     |        +--ro sid                 uint32
       |     +--ro sid-sub-tlvs* []
       |     |  +--ro sid-sub-tlv
       |     |     +--ro length?   uint8
       |     |     +--ro sid?      uint32
       |     +--ro unknown-tlvs
       |        +--ro unknown-tlv* []
       |           +--ro type?     uint16
       |           +--ro length?   uint16
       |           +--ro value?    yang:hex-string
       +--ro mt-sid-binding-tlvs
          +--ro mt-sid-binding-tlv* [prefix mt-id]
             +--ro prefix                 inet:ip-prefix
             +--ro range?                 uint16
             +--ro sid-binding-flags
             |  +--ro flags*   identityref
             +--ro prefix-sid-sub-tlvs* []
             |  +--ro prefix-sid-sub-tlvs
             |     +--ro prefix-sid-sub-tlv* [sid]
             |        +--ro prefix-sid-flags
             |        |  +--ro flags*   identityref
             |        +--ro algorithm?          identityref
             |        +--ro sid                 uint32
             +--ro sid-sub-tlvs* []
             |  +--ro sid-sub-tlv
             |     +--ro length?   uint8
             |     +--ro sid?      uint32
             +--ro unknown-tlvs
             |  +--ro unknown-tlv* []
             |     +--ro type?     uint16
             |     +--ro length?   uint16
             |     +--ro value?    yang:hex-string
             +--ro mt-id                  uint16

4.  IS-IS MPLS Segment Routing YANG Module

   [RFC6991], [RFC8102], [RFC8294], [RFC8349], [RFC8667], [RFC9020],
   [RFC9130], and [I-D.ietf-rtgwg-segment-routing-ti-lfa] are referenced
   in the YANG model.

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   <CODE BEGINS> file "ietf-isis-sr-mpls@2024-01-22.yang"
   module ietf-isis-sr-mpls {
     yang-version 1.1;
     namespace "urn:ietf:params:xml:ns:yang:ietf-isis-sr-mpls";
     prefix isis-sr-mpls;

     import ietf-routing {
       prefix rt;
       reference
         "RFC 8349 - A YANG Data Model for Routing
                     Management (NMDA Version)";
     }
     import ietf-inet-types {
       prefix inet;
       reference
         "RFC 6991 - Common YANG Data Types";
     }
     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;
       reference
         "RFC 9130 - YANG Data Model for IS-IS Protocol";
     }
     import iana-routing-types {
       prefix iana-rt-types;
       reference
         "RFC 8294 - Common YANG Data Types for the Routing Area";
     }
     import ietf-routing-types {
       prefix rt-types;
       reference
         "RFC 8294 - Common YANG Data Types for the Routing Area";
     }

     organization
       "IETF LSR - Link State Routing Working Group";
     contact
       "WG Web:   <https://datatracker.ietf.org/wg/lsr/>
        WG List:  <mailto:lsr@ietf.org>

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        Author:    Stephane Litkowski
                   <mailto:slitkows.ietf@gmail.com>
        Author:    Yingzhen Qu
                   <mailto:yingzhen.ietf@gmail.com>
        Author:    Acee Lindem
                   <mailto:acee.ietf@gmail.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 the generic configuration and
        operational state for Segment Routing ISIS extensions for the
        MPLS data plane, which is 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) 2024 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 Revised 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.";
     reference
       "RFC XXXX";

     revision 2024-01-22 {

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       description
         "Initial revision.";
       reference
         "RFC XXXX: A YANG Data Model for IS-IS Segment Routing for the
                    MPLS Data Plane";
     }

     /* Identities */

     identity sr-capability {
       description
         "Base identity for ISIS SR-Capabilities sub-TLV flags";
       reference
         "RFC 8667 - IS-IS Extensions for Segment Routing";
     }

     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-flag {
       description
         "Base identity for prefix SID sub-TLV flags.";
       reference
         "RFC 8667 - IS-IS Extensions for Segment Routing, Section 2.1";
     }

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

     identity n-flag {
       base prefix-sid-flag;
       description

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         "Node-SID Flag.";
     }

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

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

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

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

     identity adj-sid-flag {
       description
         "Base identity for Adj-SID sub-TLV flags.";
       reference
         "RFC 8667 - IS-IS Extensions for Segment Routing, Section 2.2";
     }

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

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

     identity vi-flag {
       base adj-sid-flag;

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       description
         "Value/Index flag.";
     }

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

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

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

     identity sid-binding-flag {
       description
         "Base identity for sid binding tlv flags.";
       reference
         "RFC 8667 - IS-IS Extensions for Segment Routing, Section 2.4";
     }

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

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

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

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

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

     /* Features */

     feature remote-lfa-sr {
       description
         "Enhance rLFA to use SR path.";
       reference
         "RFC 8102: Remote-LFA Node Protection and Manageability";
     }

     feature ti-lfa {
       description
         "Topology-Independent Loop-Free Alternate (TI-LFA)
          computation using segment routing.";
       reference
         "draft-ietf-rtgwg-segment-routing-ti-lfa -
          Topology-Independent Fast Reroute using Segment Routing";
     }

     /* 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 length {
           type uint8;
           description
             "Length of the SID value. YANG model specification
              is necessary since it dictates the semantics of the
              SID.";
         }
         leaf sid {
           type uint32;

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           description
             "Segment Identifier (SID) - A 20 bit label or 32 bit SID.
              If the length is set to 3, then the 20 rightmost bits
              represent an MPLS label. If the length is set to 4, then
              the value is a 32-bit index.";
         }
       }
     }

     grouping sr-capability {
       description
         "SR capability grouping.";
       reference
         "RFC 8667 - IS-IS Extensions for Segment Routing, Section 3";
       container sr-capability {
         description
           "Segment Routing capability.";
         container sr-capability {
           leaf-list sr-capability-flags {
             type identityref {
               base sr-capability;
             }
             description
               "SR Capability sub-TLV flags.";
           }
           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.";

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       container sr-algorithms {
         description
           "All SR algorithms.";
         leaf-list sr-algorithm {
           type identityref {
             base sr-cmn:prefix-sid-algorithm;
           }
           description
             "The Segment Routing (SR) algorithms that the router is
              currently using.";
         }
       }
     }

     grouping srlb {
       description
         "SR Local Block grouping.";
       reference
         "RFC 8667 - IS-IS Extensions for Segment Routing, Section 3.3";
       container local-blocks {
         description
           "List of SRLBs.";
         list local-block {
           description
             "Segment Routing Local Block.";
           leaf range-size {
             type rt-types:uint24;
             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;
           description
             "SRMS preference TLV, value from 0 to 255 with
              255 being the most preferred.";

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         }
       }
     }

     grouping adjacency-state {
       description
         "This grouping extends adjacency state.";
       list adjacency-sid {
         key "value";
         config false;
         leaf value {
           type uint32;
           description
             "Value of the Adj-SID.";
         }
         leaf address-family {
           type iana-rt-types:address-family;
           description
             "Address-family associated with the
              segment ID";
         }
         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-sid-sub-tlv {
       description
         "This grouping defines segment routing prefix segment identifier
          (prefix-sid) sub-tlv.";
       reference
         "RFC 8667 - IS-IS Extensions for Segment Routing, Section 2.1";
       container prefix-sid-sub-tlvs {
         description
           "PrefixSID sub-tlvs.";
         list prefix-sid-sub-tlv {

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           key "sid";
           container prefix-sid-flags {
             leaf-list flags {
               type identityref {
                 base prefix-sid-flag;
               }
               description
                 "Prefix SID sub-TLV flags.";
             }
             description
               "Describes flags associated with the
                segment ID.";
           }
           leaf algorithm {
             type identityref {
               base sr-cmn:prefix-sid-algorithm;
             }
             description
               "Algorithm to be used for path computation.";
           }
           leaf sid {
             type uint32;
             description
               "Value of the prefix-SID.";
           }
           description
             "List of prefix-sid sub-tlvs.";
         }
       }
     }

     grouping adjacency-segment-id {
       description
         "This grouping defines segment routing extensions
          for adjacencies.";
       list sid-list {
         key "sid";
         container adj-sid-flags {
           leaf-list flags {
             type identityref {
               base adj-sid-flag;
             }
             description
               "Adj-SID sub-TLV flags list.";
           }
           description
             "Adj-SID sub-TLV flags.";
         }

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         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 sid {
           type uint32;
           description
             "Value of the Adj-SID.";
         }
         description
           "List of segments.";
       }
     }

     grouping sid-binding-tlv {
       leaf prefix {
         type inet:ip-prefix;
         description
           "The prefix represents the Forwarding Equivalence
            Class at the tail end of the advertised path.";
       }
       leaf range {
         type uint16;
         description
           "Provides the ability to specify a range of addresses
            and their associated prefix-sids.";
       }
       container sid-binding-flags {
         leaf-list flags {
           type identityref {
             base sid-binding-flag;
           }
           description
             "SID Binding TLV flags.";
         }
         description
           "Binding TLV flags.";
       }
       list prefix-sid-sub-tlvs {

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         uses prefix-sid-sub-tlv;
         description
           "List of prefix-sid sub-tlvs.";
         reference
           "RFC 8667 - IS-IS Extensions for Segment Routing,
            Section 2.4.4";
       }
       list sid-sub-tlvs {
         uses sid-sub-tlv;
         description
           "List of prefix-sid sub-tlvs.";
         reference
           "RFC 8667 - IS-IS Extensions for Segment Routing,
            Section 2.4.5";
       }
       uses isis:unknown-tlvs;
       description
         "SID/Label binding TLV, type 149.";
       reference
         "RFC 8667 - IS-IS Extensions for Segment Routing,
          Section 2.4";
     }

     /* Configuration */

     augment "/rt:routing/"
           + "rt:control-plane-protocols/rt:control-plane-protocol"
           + "/isis:isis" {
       when "derived-from-or-self(../rt:type, 'isis:isis')" {
         description
           "This augments ISIS routing protocol when used";
       }
       description
         "This augments ISIS protocol configuration
          with segment routing for the MPLS data plane.";
       uses sr-mpls:sr-control-plane;
       container protocol-srgb {
         if-feature "sr-mpls:protocol-srgb";
         uses sr-cmn:srgb;
         description
           "Per-protocol Segment Routing Global Block (SRGB).";
         reference
           "RFC 8402 - Segment Routing Architecture, Section 2";
       }
     }

     augment "/rt:routing/"
           + "rt:control-plane-protocols/rt:control-plane-protocol"

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           + "/isis:isis/isis:interfaces/isis:interface" {
       when "derived-from-or-self(../../../rt:type, 'isis:isis')" {
         description
           "This augments ISIS routing protocol when used";
       }
       description
         "This augments ISIS protocol configuration
          with segment routing.";
       uses sr-mpls:igp-interface {
         augment "segment-routing/adjacency-sid/adj-sids" {
           when "../../../isis:interface-type = 'broadcast'" {
             description
               "This augments broadcast interface.";
           }
           description
             "This augments LAN interface adj-sid with system-id.";
           leaf neighbor-system-id {
             type isis:system-id;
             mandatory true;
             description
               "Neighbor system ID.";
           }
         }
       }
     }

     augment "/rt:routing/"
           + "rt:control-plane-protocols/rt:control-plane-protocol"
           + "/isis:isis/isis:interfaces/isis:interface"
           + "/isis:fast-reroute/isis:lfa" {
       when "derived-from-or-self(../../../../../rt:type,"
          + "'isis:isis')" {
         description
           "This augments ISIS routing protocol when used";
       }
       description
         "This augments ISIS interface IP FRR with TILFA.";
       container ti-lfa {
         if-feature "ti-lfa";
         leaf enabled {
           type boolean;
           default "false";
           description
             "Enables TI-LFA computation.";
         }
         container selection-tie-breakers {
           container node-protection {
             presence "Presence of container enables the node

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                       protection tie-breaker";
             leaf priority {
               type uint8;
               default "128";
               description
                 "Priority for node protection tie-breaker with
                  a lower priority being more preferred.";
             }
             description
               "Enable node protection as a TI-LFA path
                selection tie-breaker. A path providing node
                protection will be selected over one that
                doesn't provide node protection.";
           }
           container srlg-disjoint {
             presence "Presence of container enables the SRLG
                       disjoint tie-breaker";
             leaf priority {
               type uint8;
               default "128";
               description
                 "Priority for SRLG disjoint tie-breaker with
                  a lower priority being more preferred.";
             }
             description
               "Enable SRLG (Shared Resource Link Group)
                disjoint  as a TI-LFA path selection tie-breaker.
                A path providing node a disjoint path for SRLG
                links from the primary path will be selected over
                one that doesn't provide an SRLG disjoint path.";
           }
           description
             "Configure path selection tie-breakers and their
              respective priorities for the TI-LFA computation.";
         }
         description
           "Topology Independent Loop Free Alternate
            (TI-LFA) support.";
       }
     }

     augment "/rt:routing/"
           + "rt:control-plane-protocols/rt:control-plane-protocol"
           + "/isis:isis/isis:interfaces/isis:interface"
           + "/isis:fast-reroute/isis:lfa/isis:level-1" {
       when "derived-from-or-self(../../../../../../rt:type,"
          + "'isis:isis')" {
         description

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           "This augments ISIS routing protocol when used";
       }
       description
         "This augments ISIS interface level-1 IP FRR with TILFA.";
       container ti-lfa {
         if-feature "ti-lfa";
         leaf enabled {
           type boolean;
           default "false";
           description
             "Enables TI-LFA computation.";
         }
         description
           "TI-LFA configuration.";
       }
     }

     augment "/rt:routing/"
           + "rt:control-plane-protocols/rt:control-plane-protocol"
           + "/isis:isis/isis:interfaces/isis:interface"
           + "/isis:fast-reroute/isis:lfa/isis:level-2" {
       when "derived-from-or-self(../../../../../../rt:type,"
          + "'isis:isis')" {
         description
           "This augments ISIS routing protocol when used";
       }
       description
         "This augments ISIS IP interface level-2 FRR with TILFA.";
       container ti-lfa {
         if-feature "ti-lfa";
         leaf enabled {
           type boolean;
           default "false";
           description
             "Enables TI-LFA computation.";
         }
         description
           "TI-LFA 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 "derived-from-or-self(../../../../../../rt:type,"
          + "'isis:isis')" {
         description

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           "This augments 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;
         default "false";
         description
           "Force remote LFA to use segment routing path instead of LDP
            path. The value of this leaf is in effect only when
            remote-lfa is enabled.";
       }
     }

     /* Operational states */

     augment "/rt:routing/"
           + "rt:control-plane-protocols/rt:control-plane-protocol"
           + "/isis:isis/isis:interfaces/isis:interface"
           + "/isis:adjacencies/isis:adjacency" {
       when "derived-from-or-self(../../../../../rt:type, 'isis:isis')" {
         description
           "This augments 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 "derived-from-or-self(../../../../../rt:type, 'isis:isis')" {
         description
           "This augments ISIS routing protocol when used";
       }
       description
         "This augments ISIS protocol LSDB router capability.";
       uses sr-capability;
       uses sr-algorithm;
       uses srlb;
       uses srms-preference;
     }

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     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 "derived-from-or-self(../../../../../../rt:type,"
          + "'isis:isis')" {
         description
           "This augments 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 "derived-from-or-self(../../../../../../rt:type,"
          + "'isis:isis')" {
         description
           "This augments 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 "derived-from-or-self(../../../../../../rt:type,"
          + "'isis:isis')" {
         description
           "This augments ISIS routing protocol when used";
       }
       description
         "This augments ISIS protocol LSDB prefix.";
       uses prefix-sid-sub-tlv;
     }

     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 "derived-from-or-self(../../../../../../rt:type,"
          + "'isis:isis')" {

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         description
           "This augments ISIS routing protocol when used";
       }
       description
         "This augments ISIS protocol LSDB prefix.";
       uses prefix-sid-sub-tlv;
     }

     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 "derived-from-or-self(../../../../../../rt:type,"
          + "'isis:isis')" {
         description
           "This augments ISIS routing protocol when used";
       }
       description
         "This augments ISIS protocol LSDB prefix.";
       uses prefix-sid-sub-tlv;
     }

     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 "derived-from-or-self(../../../../../../rt:type,"
          + "'isis:isis')" {
         description
           "This augments ISIS routing protocol when used";
       }
       description
         "This augments ISIS protocol LSDB prefix.";
       uses prefix-sid-sub-tlv;
     }

     augment "/rt:routing/"
           + "rt:control-plane-protocols/rt:control-plane-protocol"
           + "/isis:isis/isis:database/isis:levels/isis:lsp" {
       when "derived-from-or-self(../../../../rt:type,"
          + "'isis:isis')" {
         description
           "This augments ISIS routing protocol when used";
       }
       description
         "This augments ISIS protocol LSDB.";
       container sid-binding-tlvs {
         list sid-binding-tlv {

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           key "prefix";
           uses sid-binding-tlv;
           description
             "Sid/label binding TLV, type 149.";
         }
         description
           "List of sid/label binding TLVs.";
       }
       container mt-sid-binding-tlvs {
         list mt-sid-binding-tlv {
           key "prefix mt-id";
           uses sid-binding-tlv;
           leaf mt-id {
             type uint16;
             description
               "A 12-bit field containing the non-zero ID
                of the topology.";
           }
           description
             "Multi-Topology SID/Label binding TLV, type 150.";
           reference
             "RFC 8667 - IS-IS Extensions for Segment Routing,
              Section 2.5";
         }
         description
           "List of multi-topology sid/label binding TLVs.";
       }
     }
   }
   <CODE ENDS>

5.  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.

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   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

      /isis:isis/isis:interfaces/isis:interface/isis:fast-reroute/ti-lfa

   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

      /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.

6.  Contributors

   Authors would like to thank Derek Yeung, Acee Lindem, Yi Yang for
   their major contributions to the draft.  Also thank Reshad Rahman,
   and Tom Petch for their thorough reviews and helpful comments.

7.  Acknowledgements

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

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8.  IANA Considerations

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

           URI: urn:ietf:params:xml:ns:yang:ietf-isis-sr-mpls
           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-mpls
           namespace: urn:ietf:params:xml:ns:yang:ietf-isis-sr-mpls
           prefix: isis-sr-mpls
           reference: RFC XXXX

9.  References

9.1.  Normative References

   [I-D.ietf-rtgwg-segment-routing-ti-lfa]
              Bashandy, A., Litkowski, S., Filsfils, C., Francois, P.,
              Decraene, B., and D. Voyer, "Topology Independent Fast
              Reroute using Segment Routing", Work in Progress,
              Internet-Draft, draft-ietf-rtgwg-segment-routing-ti-lfa-
              13, 16 January 2024,
              <https://datatracker.ietf.org/doc/html/draft-ietf-rtgwg-
              segment-routing-ti-lfa-13>.

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

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

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

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

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   [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>.

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

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

   [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>.

   [RFC8102]  Sarkar, P., Ed., Hegde, S., Bowers, C., Gredler, H., and
              S. Litkowski, "Remote-LFA Node Protection and
              Manageability", RFC 8102, DOI 10.17487/RFC8102, March
              2017, <https://www.rfc-editor.org/info/rfc8102>.

   [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>.

   [RFC8294]  Liu, X., Qu, Y., Lindem, A., Hopps, C., and L. Berger,
              "Common YANG Data Types for the Routing Area", RFC 8294,
              DOI 10.17487/RFC8294, December 2017,
              <https://www.rfc-editor.org/info/rfc8294>.

   [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>.

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

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   [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>.

   [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>.

   [RFC9020]  Litkowski, S., Qu, Y., Lindem, A., Sarkar, P., and J.
              Tantsura, "YANG Data Model for Segment Routing", RFC 9020,
              DOI 10.17487/RFC9020, May 2021,
              <https://www.rfc-editor.org/info/rfc9020>.

   [RFC9130]  Litkowski, S., Ed., Yeung, D., Lindem, A., Zhang, J., and
              L. Lhotka, "YANG Data Model for the IS-IS Protocol",
              RFC 9130, DOI 10.17487/RFC9130, October 2022,
              <https://www.rfc-editor.org/info/rfc9130>.

9.2.  Informative References

   [RFC8792]  Watsen, K., Auerswald, E., Farrel, A., and Q. Wu,
              "Handling Long Lines in Content of Internet-Drafts and
              RFCs", RFC 8792, DOI 10.17487/RFC8792, June 2020,
              <https://www.rfc-editor.org/info/rfc8792>.

Appendix A.  A Configuration Example

   The following is an XML example using the ISIS SR MPLS YANG module
   defined in this document.

   Note: '\' line wrapping per [RFC8792].

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   <?xml version='1.0' encoding='UTF-8'?>
     <routing xmlns="urn:ietf:params:xml:ns:yang:ietf-routing">
       <router-id>1.1.1.1</router-id>
       <control-plane-protocols>
         <control-plane-protocol>
           <type xmlns:isis="urn:ietf:params:xml:ns:yang:ietf-isis">\
             isis:isis</type>
           <name>isis</name>
           <isis xmlns="urn:ietf:params:xml:ns:yang:ietf-isis">
             <system-id>1111.2222.3333</system-id>
             <interfaces>
               <interface>
                 <name/>
                 <segment-routing xmlns="urn:ietf:params:xml:ns:yang:\
                   ietf-isis-sr-mpls">
                   <adjacency-sid>
                     <adj-sids>
                       <value>38888</value>
                     </adj-sids>
                   </adjacency-sid>
                 </segment-routing>
               </interface>
             </interfaces>
             <segment-routing xmlns="urn:ietf:params:xml:ns:yang:\
               ietf-isis-sr-mpls">
               <enabled>true</enabled>
             </segment-routing>
             <protocol-srgb xmlns="urn:ietf:params:xml:ns:yang:\
               ietf-isis-sr-mpls">
               <srgb>
                 <lower-bound>4000</lower-bound>
                 <upper-bound>5000</upper-bound>
               </srgb>
             </protocol-srgb>
           </isis>
         </control-plane-protocol>
       </control-plane-protocols>
     </routing>

   The following is the same example using JSON format.

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   {
     "routing": {
       "router-id": "1.1.1.1",
       "control-plane-protocols": {
         "control-plane-protocol": {
           "type": "isis:isis",
           "name": "isis",
           "isis": {
             "system-id": "1111.2222.3333",
             "interfaces": {
               "interface": {
                 "name": "",
                 "segment-routing": {
                   "adjacency-sid": {
                     "adj-sids": {
                       "value": 38888
                     }
                   }
                 }
               }
             },
             "segment-routing": {
               "enabled": true
             },
             "protocol-srgb": {
               "srgb": {
                 "lower-bound": 4000,
                 "upper-bound": 5000
               }
             }
           }
         }
       }
     }
   }

Authors' Addresses

   Stephane Litkowski
   Cisco Systems
   Email: slitkows.ietf@gmail.com

   Yingzhen Qu
   Futurewei Technologies
   Email: yingzhen.ietf@gmail.com

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   Pushpasis Sarkar
   Individual
   Email: pushpasis.ietf@gmail.com

   Ing-Wher Chen
   The MITRE Corporation
   Email: ingwherchen@mitre.org

   Jeff Tantsura
   Nvidia
   Email: jefftant.ietf@gmail.com

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