IS-IS Working Group                                         S. Litkowski
Internet-Draft                                                    Orange
Intended status: Standards Track                                D. Yeung
Expires: November 26, 2018 January 3, 2019                                     Arrcus, Inc
                                                               A. Lindem
                                                           Cisco Systems
                                                                J. Zhang
                                                        Juniper Networks
                                                               L. Lhotka
                                                                  CZ.NIC
                                                            May 25,
                                                            July 2, 2018

                   YANG Data Model for IS-IS protocol
                    draft-ietf-isis-yang-isis-cfg-20
                    draft-ietf-isis-yang-isis-cfg-21

Abstract

   This document defines a YANG data model that can be used to configure
   and manage IS-IS protocol on network elements.

Requirements Language

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in [RFC2119].

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at http://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 November 26, 2018. January 3, 2019.

Copyright Notice

   Copyright (c) 2018 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
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
     1.1.  Tree diagram  . . . . . . . . . . . . . . . . . . . . . .   3
   2.  Design of the Data Model  . . . . . . . . . . . . . . . . . .   3
     2.1.  IS-IS Configuration . . . . . . . . . . . . . . . . . . .   9
     2.2.  Multitopology Parameters  . . . . . . . . . . . . . . . .  10
     2.3.  Per-Level Parameters  . . . . . . . . . . . . . . . . . .  10
     2.4.  Per-Interface Parameters  . . . . . . . . . . . . . . . .  12
     2.5.  Authentication Parameters . . . . . . . . . . . . . . . .  23
     2.6.  IGP/LDP synchronization . . . . . . . . . . . . . . . . .  23
     2.7.  ISO parameters  . . . . . . . . . . . . . . . . . . . . .  23  24
     2.8.  IP FRR  . . . . . . . . . . . . . . . . . . . . . . . . .  23  24
     2.9.  Operational States  . . . . . . . . . . . . . . . . . . .  24
   3.  RPC Operations  . . . . . . . . . . . . . . . . . . . . . . .  24  25
   4.  Notifications . . . . . . . . . . . . . . . . . . . . . . . .  25
   5.  Interaction with Other YANG Modules . . . . . . . . . . . . .  26
   6.  IS-IS YANG Module . . . . . . . . . . . . . . . . . . . . . .  26  27
   7.  Security Considerations . . . . . . . . . . . . . . . . . . . 101  94
   8.  Contributors  . . . . . . . . . . . . . . . . . . . . . . . . 102  95
   9.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . 102  95
   10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 103  95
   11. Change log for ietf-isis YANG module  . . . . . . . . . . . . 103  96
     11.1.  From version -19 to version -20  . . . . . . . . . . . . 103  96
     11.2.  From version -18 to version -19  . . . . . . . . . . . . 103  96
     11.3.  From version -17 to version -18  . . . . . . . . . . . . 103  96
     11.4.  From version -16 to version -17  . . . . . . . . . . . . 104  96
     11.5.  From version -15 to version -16  . . . . . . . . . . . . 104  96
     11.6.  From version -14 to version -15  . . . . . . . . . . . . 104  97
     11.7.  From version -13 to version -14  . . . . . . . . . . . . 104  97
     11.8.  From version -12 to version -13  . . . . . . . . . . . . 105  97
     11.9.  From version -09 to version -12  . . . . . . . . . . . . 105  97
     11.10. From version -08 to version -09  . . . . . . . . . . . . 105  98
     11.11. From version -07 to version -08  . . . . . . . . . . . . 105  98
     11.12. From version -05 to version -07  . . . . . . . . . . . . 105  98
     11.13. From version -03 to version -05  . . . . . . . . . . . . 106  98
     11.14. From version -02 to version -03  . . . . . . . . . . . . 106  99
     11.15. From version -01 to version -02  . . . . . . . . . . . . 106  99
     11.16. From version -00 to version -01  . . . . . . . . . . . . 107  99
   12. Normative References  . . . . . . . . . . . . . . . . . . . . 107 100
   Appendix A.  Example of IS-IS configuration in XML  . . . . . . . 108 101
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . . 111 103

1.  Introduction

   This document defines a YANG data model for IS-IS routing protocol.

   The data model covers configuration of an IS-IS routing protocol
   instance as well as operational states.

1.1.  Tree diagram

   A simplified graphical representation of the data model is presented
   in Section 2.

   The meaning of the symbols in these diagrams is as follows:

   o  Brackets "[" and "]" enclose list keys.

   o  Curly braces "{" and "}" contain names of optional features that
      make the corresponding node conditional.

   o  Abbreviations before data node names: "rw" means configuration
      (read-write), and "ro" state data (read-only).

   o  Symbols after data node names: "?" means an optional node and "*"
      denotes a "list" or "leaf-list".

   o  Parentheses enclose choice and case nodes, and case nodes are also
      marked with a colon (":").

   o  Ellipsis ("...") stands for contents of subtrees that are not
      shown.

2.  Design of the Data Model

   The IS-IS YANG module augments the "control-plane-protocol" list in
   ietf-routing module with specific IS-IS parameters.

   The module is designed as per NMDA (Network Management Datastore
   Architecture).

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

   module: ietf-isis
     augment /rt:routing/rt:ribs/rt:rib/rt:routes/rt:route:
       +--ro metric?       uint32
       +--ro tag*          uint64
       +--ro route-type?   enumeration
     augment /if:interfaces/if:interface:
       +--rw clns-mtu?   uint16
     augment /rt:routing/rt:control-plane-protocols/rt:control-plane-protoc
ol: /rt:routing/rt:control-plane-protocols/
       |      rt:control-plane-protocol:
       +--rw isis
          +--rw enable?                   boolean {admin-control}?
          +--rw level-type?               level
          +--rw system-id?                system-id
          +--rw maximum-area-addresses?
          |      uint8 {maximum-area-addresses}?
          +--rw area-address*             area-address
          +--rw mpls
          |  +--rw ipv4-router-id?  inet:ipv4-address {ipv4-router-id}?
          |  +--rw ipv6-router-id?  inet:ipv6-address {ipv6-router-id}?
          |  +--rw ldp
          |        ...
          +--rw auto-cost {auto-cost}?
          |  +--rw reference-bandwidth?   uint32
          |  +--rw enable?                boolean
          +--rw lsp-mtu?                  uint16
          +--rw lsp-lifetime?             uint16
          +--rw lsp-refresh?
          |      rt-types:timer-value-seconds16 {l
sp-refresh}? {lsp-refresh}?
          +--rw graceful-restart {graceful-restart}?
          |  +--rw enable?             boolean
          |  +--rw restart-interval?   rt-types:timer-value-seconds16
          |  +--rw helper-enable?      boolean
          +--rw nsr {nsr}?
          |  +--rw enable?   boolean
          +--rw node-tags {node-tag}?
          |  +--rw node-tag* [tag]
          |        ...
          +--rw authentication
          |  +--rw (authentication-type)?
          |  |     ...
          |  +--rw level-1
          |  |     ...
          |  +--rw level-2
          |        ...

          +--rw metric-type
          |  +--rw value?     enumeration
          |  +--rw level-1
          |  |     ...
          |  +--rw level-2
          |        ...
          +--rw default-metric
          |  +--rw value?     wide-metric
          |  +--rw level-1
          |  |     ...
          |  +--rw level-2
          |        ...
          +--rw afs {nlpid-control}?
          |  +--rw af* [af]
          |        ...
          +--rw preference
          |  +--rw (granularity)?
          |        ...
          +--rw overload
          |  +--rw status?   boolean
          +--rw overload-max-metric {overload-max-metric}?
          |  +--rw timeout?   rt-types:timer-value-seconds16
          +--rw fast-reroute {fast-reroute}?
          |  +--rw lfa {lfa}?
          |  +--ro protected-routes
          |  |     ...
          |  +--ro nonprotected-routes
          |  |     ...
          |  +--ro protection-statistics* [frr-protection-method]
          |        ...
          +--rw spf-control
          |  +--rw ietf-spf-delay {ietf-spf-delay}?
          |        ...
          +--rw topologies {multi-topology}?
          |  +--rw topology* [name]
          |        ...
          +--rw interfaces
          |  +--rw interface* [name]
          |        ...
          +--ro spf-log
          |  +--ro event* [id]
          |        ...
          +--ro lsp-log
          |  +--ro event* [id]
          |        ...
          +--ro hostnames
          |  +--ro hostname* [system-id]
          |        ...

          +--ro database
          |  +--ro level-db* [level]
          |        ...
          +--ro local-rib
          |  +--ro route* [prefix]
          |        ...
          +--ro system-counters
             +--ro level* [level]
                   ...

     rpcs:
       +---x clear-adjacency
       |  +---w input
       |     +---w routing-protocol-instance-name    instance-state-ref
       |     +---w level?                            level
       |     +---w interface?                        string
       +---x clear-database
          +---w input
             +---w routing-protocol-instance-name    instance-state-ref
             +---w level?                            level

     notifications:
       +---n database-overload
       |  +--ro routing-instance?        string
       |  +--ro routing-protocol-name?   string
       |  +--ro isis-level?              level
       |  +--ro overload?                enumeration
       +---n lsp-too-large
       |  +--ro routing-instance?        string
       |  +--ro routing-protocol-name?   string
       |  +--ro isis-level?              level
       |  +--ro interface-name?          string
       |  +--ro interface-level?         level
       |  +--ro extended-circuit-id?     extended-circuit-id
       |  +--ro pdu-size?                uint32
       |  +--ro lsp-id?                  lsp-id
       +---n if-state-change
       |  +--ro routing-instance?        string
       |  +--ro routing-protocol-name?   string
       |  +--ro isis-level?              level
       |  +--ro interface-name?          string
       |  +--ro interface-level?         level
       |  +--ro extended-circuit-id?     extended-circuit-id
       |  +--ro state?                   if-state-type
       +---n corrupted-lsp-detected
       |  +--ro routing-instance?        string
       |  +--ro routing-protocol-name?   string
       |  +--ro isis-level?              level
       |  +--ro lsp-id?                  lsp-id
       +---n attempt-to-exceed-max-sequence
       |  +--ro routing-instance?        string
       |  +--ro routing-protocol-name?   string
       |  +--ro isis-level?              level
       |  +--ro lsp-id?                  lsp-id
       +---n id-len-mismatch
       |  +--ro routing-instance?        string
       |  +--ro routing-protocol-name?   string
       |  +--ro isis-level?              level
       |  +--ro interface-name?          string
       |  +--ro interface-level?         level
       |  +--ro extended-circuit-id?     extended-circuit-id
       |  +--ro pdu-field-len?           uint8
       |  +--ro raw-pdu?                 binary
       +---n max-area-addresses-mismatch
       |  +--ro routing-instance?        string
       |  +--ro routing-protocol-name?   string
       |  +--ro isis-level?              level
       |  +--ro interface-name?          string
       |  +--ro interface-level?         level
       |  +--ro extended-circuit-id?     extended-circuit-id
       |  +--ro max-area-addresses?      uint8
       |  +--ro raw-pdu?                 binary
       +---n own-lsp-purge
       |  +--ro routing-instance?        string
       |  +--ro routing-protocol-name?   string
       |  +--ro isis-level?              level
       |  +--ro interface-name?          string
       |  +--ro interface-level?         level
       |  +--ro extended-circuit-id?     extended-circuit-id
       |  +--ro lsp-id?                  lsp-id
       +---n sequence-number-skipped
       |  +--ro routing-instance?        string
       |  +--ro routing-protocol-name?   string
       |  +--ro isis-level?              level
       |  +--ro interface-name?          string
       |  +--ro interface-level?         level
       |  +--ro extended-circuit-id?     extended-circuit-id
       |  +--ro lsp-id?                  lsp-id
       +---n authentication-type-failure
       |  +--ro routing-instance?        string
       |  +--ro routing-protocol-name?   string
       |  +--ro isis-level?              level
       |  +--ro interface-name?          string
       |  +--ro interface-level?         level
       |  +--ro extended-circuit-id?     extended-circuit-id
       |  +--ro raw-pdu?                 binary
       +---n authentication-failure
       |  +--ro routing-instance?        string
       |  +--ro routing-protocol-name?   string
       |  +--ro isis-level?              level
       |  +--ro interface-name?          string
       |  +--ro interface-level?         level
       |  +--ro extended-circuit-id?     extended-circuit-id
       |  +--ro raw-pdu?                 binary
       +---n version-skew
       |  +--ro routing-instance?        string
       |  +--ro routing-protocol-name?   string
       |  +--ro isis-level?              level
       |  +--ro interface-name?          string
       |  +--ro interface-level?         level
       |  +--ro extended-circuit-id?     extended-circuit-id
       |  +--ro protocol-version?        uint8
       |  +--ro raw-pdu?                 binary
       +---n area-mismatch
       |  +--ro routing-instance?        string
       |  +--ro routing-protocol-name?   string
       |  +--ro isis-level?              level
       |  +--ro interface-name?          string
       |  +--ro interface-level?         level
       |  +--ro extended-circuit-id?     extended-circuit-id
       |  +--ro raw-pdu?                 binary
       +---n rejected-adjacency
       |  +--ro routing-instance?        string
       |  +--ro routing-protocol-name?   string
       |  +--ro isis-level?              level
       |  +--ro interface-name?          string
       |  +--ro interface-level?         level
       |  +--ro extended-circuit-id?     extended-circuit-id
       |  +--ro raw-pdu?                 binary
       |  +--ro reason?                  string
       +---n protocols-supported-mismatch
       |  +--ro routing-instance?        string
       |  +--ro routing-protocol-name?   string
       |  +--ro isis-level?              level
       |  +--ro interface-name?          string
       |  +--ro interface-level?         level
       |  +--ro extended-circuit-id?     extended-circuit-id
       |  +--ro raw-pdu?                 binary
       |  +--ro protocols*               uint8
       +---n lsp-error-detected
       |  +--ro routing-instance?        string
       |  +--ro routing-protocol-name?   string
       |  +--ro isis-level?              level
       |  +--ro interface-name?          string
       |  +--ro interface-level?         level
       |  +--ro extended-circuit-id?     extended-circuit-id
       |  +--ro lsp-id?                  lsp-id
       |  +--ro raw-pdu?                 binary
       |  +--ro error-offset?            uint32
       |  +--ro tlv-type?                uint8
       +---n adjacency-state-change
       |  +--ro routing-instance?        string
       |  +--ro routing-protocol-name?   string
       |  +--ro isis-level?              level
       |  +--ro interface-name?          string
       |  +--ro interface-level?         level
       |  +--ro extended-circuit-id?     extended-circuit-id
       |  +--ro neighbor?                string
       |  +--ro neighbor-system-id?      system-id
       |  +--ro state?                   adj-state-type
       |  +--ro reason?                  string
       +---n lsp-received
       |  +--ro routing-instance?        string
       |  +--ro routing-protocol-name?   string
       |  +--ro isis-level?              level
       |  +--ro interface-name?          string
       |  +--ro interface-level?         level
       |  +--ro extended-circuit-id?     extended-circuit-id
       |  +--ro lsp-id?                  lsp-id
       |  +--ro sequence?                uint32
       |  +--ro received-timestamp?      yang:timestamp
       |  +--ro neighbor-system-id?      system-id
       +---n lsp-generation
          +--ro routing-instance?        string
          +--ro routing-protocol-name?   string
          +--ro isis-level?              level
          +--ro lsp-id?                  lsp-id
          +--ro sequence?                uint32
          +--ro send-timestamp?          yang:timestamp

2.1.  IS-IS Configuration

   The IS-IS configuration container is divided in:

   o  Global parameters.

   o  Per interface configuration (see Section 2.4).

   Additional modules may be created this to support any additional
   parameters.  These additional modules should augment the ietf-isis
   module.

   The model implements features, thus some of the configuration
   statement becomes optional.  As an example, the ability to control
   the administrative state of a particular IS-IS instance is optional.
   By advertising the feature "admin-control", a device communicates to
   the client that it supports the ability to shutdown a particular IS-
   IS instance.

   The global configuration contains usual IS-IS parameters such as lsp-
   mtu, lsp-lifetime, lsp-refresh, default-metric...

2.2.  Multitopology Parameters

   The model supports multitopology (MT) IS-IS as defined in [RFC5120].

   The "topologies" container is used to enable support of MT
   extensions.

   The "name" used in the topology list should refer to an existing RIB
   of the device.

   Some specific parameters could be defined on a per topology basis
   both at global level and at interface level: for example, an
   interface metric can be defined per topology.

   Multiple address families (like IPv4 or IPv6) can also be activated
   within the default topology.  This can be achieved using the "afs"
   container (requiring "nlpid-control" feature to be advertised).

2.3.  Per-Level Parameters

   Some parameters allow a per level configuration.  In this case, the
   parameter is modeled as a container with three configuration
   locations:

   o  a top level container: corresponds to level-1-2, so the
      configuration applies to both levels.

   o  a level-1 container: corresponds to level-1 specific parameters.

   o  a level-2 container: corresponds to level-2 specific parameters.

               +--rw priority
               |  +--rw value?     uint8
               |  +--rw level-1
               |  |  +--rw value?   uint8
               |  +--rw level-2
               |     +--rw value?   uint8

   Example:

           <priority>
               <value>250</value>
                           <level-1>
                                   <value>100</value>
                           </level-1>
                           <level-2>
                                   <value>200</value>
                           </level-2>
           </priority>

   An implementation SHOULD prefer a level specific parameter over a
   level-all parameter.  As example, if the priority is 100 for the
   level-1, 200 for the level-2 and 250 for the top level configuration,
   the implementation should use 100 for the level-1 and 200 for the
   level-2.

   Some parameters like "overload bit" and "route preference" are not
   modeled to support a per level configuration.  If an implementation
   supports per level configuration for such parameter, this
   implementation SHOULD augment the current model by adding both
   level-1 and level-2 containers and SHOULD reuse existing
   configuration groupings.

   Example of augmentation:

   augment "/rt:routing/" +
           "rt:control-plane-protocols/rt:control-plane-protocol"+
           "/isis:isis/isis:overload" {
           when "rt:type = 'isis:isis'" {
         description
         "This augment IS-IS routing protocol when used";
       }
       description
        "This augments IS-IS overload configuration
         with per level configuration.";

           container level-1 {
                   uses isis:overload-global-cfg;
                   description
                    "Level 1 configuration.";
           }
           container level-2 {
                   uses isis:overload-global-cfg;
                   description
                    "Level 2 configuration.";
           }

   }

   If an implementation does not support per level configuration for a
   parameter modeled with per level configuration, the implementation
   SHOULD advertise a deviation to announce the non support of the
   level-1 and level-2 containers.

   Finally, if an implementation supports per level configuration but
   does not support the level-1-2 configuration, it SHOULD also
   advertise a deviation.

2.4.  Per-Interface Parameters

   The per-interface section of the IS-IS instance describes the
   interface specific parameters.

   The interface is modeled as a reference to an existing interface
   defined in the "ietf-interfaces" YANG model.

   Each interface has some interface-specific parameters that may have a
   different per level value as described in previous section.  An
   interface-specific parameter always override an IS-IS global
   parameter.

   Some parameters like hello-padding are defined as containers to allow
   easy extension by vendor specific modules.

       +--rw interfaces
       |  +--rw interface* [name]
       |     +--rw name                       if:interface-ref
       |     +--rw level-type?                level
       |     +--rw lsp-pacing-interval?       rt-types:timer-value-milli
seconds
       |     |       rt-types:timer-value-milliseconds
       |     +--rw lsp-retransmit-interval?   rt-types:timer-value-secon
ds16
       |     |       rt-types:timer-value-seconds16
       |     +--rw passive?                   boolean
       |     +--rw csnp-interval?             rt-types:timer-value-secon
ds16
       |     |       rt-types:timer-value-seconds16
       |     +--rw hello-padding
       |     |  +--rw enable?   boolean
       |     +--rw mesh-group-enable?         mesh-group-state
       |     +--rw mesh-group?                uint8
       |     +--rw interface-type?            interface-type
       |     +--rw enable?                    boolean {admin-control}?
       |     +--rw tag*                       uint32 {prefix-tag}?
       |     +--rw tag64*                     uint64 {prefix-tag64}?
       |     +--rw node-flag?                 boolean {node-flag}?
       |     +--rw hello-authentication
       |     |  +--rw (authentication-type)?
       |     |  |  +--:(key-chain) {key-chain}?
       |     |  |  |  +--rw key-chain?        key-chain:key-chain-ref
       |     |  |  +--:(password)
       |     |  |     +--rw key?                string
       |     |  |     +--rw crypto-algorithm?   identityref
       |     |  +--rw level-1
       |     |  |  +--rw (authentication-type)?
       |     |  |     +--:(key-chain) {key-chain}?
       |     |  |     |  +--rw key-chain?          key-chain:key-chain-r
ef      key-chain:key-chain-ref
       |     |  |     +--:(password)
       |     |  |        +--rw key?                string
       |     |  |        +--rw crypto-algorithm?   identityref
       |     |  +--rw level-2
       |     |     +--rw (authentication-type)?
       |     |        +--:(key-chain) {key-chain}?
       |     |        |  +--rw key-chain?          key-chain:key-chain-r
ef      key-chain:key-chain-ref
       |     |        +--:(password)
       |     |           +--rw key?                string
       |     |           +--rw crypto-algorithm?   identityref
       |     +--rw hello-interval
       |     |  +--rw value?     rt-types:timer-value-seconds16
       |     |  +--rw level-1
       |     |  |  +--rw value?   rt-types:timer-value-seconds16
       |     |  +--rw level-2
       |     |     +--rw value?   rt-types:timer-value-seconds16
       |     +--rw hello-multiplier
       |     |  +--rw value?     uint16
       |     |  +--rw level-1
       |     |  |  +--rw value?   uint16
       |     |  +--rw level-2
       |     |     +--rw value?   uint16
       |     +--rw priority
       |     |  +--rw value?     uint8
       |     |  +--rw level-1
       |     |  |  +--rw value?   uint8
       |     |  +--rw level-2
       |     |     +--rw value?   uint8
       |     +--rw metric
       |     |  +--rw value?     wide-metric
       |     |  +--rw level-1
       |     |  |  +--rw value?   wide-metric
       |     |  +--rw level-2
       |     |     +--rw value?   wide-metric
       |     +--rw bfd {bfd}?
       |     |  +--rw enable?                           boolean
       |     |  +--rw local-multiplier?                 multiplier
       |     |  +--rw (interval-config-type)?
       |     |     +--:(tx-rx-intervals)
       |     |     |  +--rw desired-min-tx-interval?    uint32
       |     |     |  +--rw required-min-rx-interval?   uint32
       |     |     +--:(single-interval) {single-minimum-interval}?
       |     |        +--rw min-interval?               uint32
       |     +--rw afs {nlpid-control}?
       |     |  +--rw af* [af]
       |     |     +--rw af    iana-rt-types:address-family
       |     +--rw mpls
       |     |  +--rw ldp
       |     |     +--rw igp-sync?   boolean {ldp-igp-sync}?
       |     +--rw fast-reroute {fast-reroute}?
       |     |  +--rw lfa {lfa}?
       |     |     +--rw candidate-disabled?   boolean
       |     |     +--rw enable?               boolean
       |     |     +--rw remote-lfa {remote-lfa}?
       |     |     |  +--rw enable?   boolean
       |     |     +--rw level-1
       |     |     |  +--rw candidate-disabled?   boolean
       |     |     |  +--rw enable?               boolean
       |     |     |  +--rw remote-lfa {remote-lfa}?
       |     |     |     +--rw enable?   boolean
       |     |     +--rw level-2
       |     |        +--rw candidate-disabled?   boolean
       |     |        +--rw enable?               boolean
       |     |        +--rw remote-lfa {remote-lfa}?
       |     |           +--rw enable?   boolean
       |     +--rw topologies {multi-topology}?
       |     |  +--rw topology* [name]
       |     |     +--rw name
       |     |     |      -> ../../../../../../../../rt:ribs/ri
b/name ../../../../../../../../rt:ribs/rib/name
       |     |     +--rw metric
       |     |        +--rw value?     wide-metric
       |     |        +--rw level-1
       |     |        |  +--rw value?   wide-metric
       |     |        +--rw level-2
       |     |           +--rw value?   wide-metric
       |     +--ro adjacencies
       |     |  +--ro adjacency* []
       |     |     +--ro neighbor-systype?               level
       |     |     +--ro neighbor-sysid?                 system-id
       |     |     +--ro neighbor-extended-circuit-id?   extended-circui
t-id
       |     |     |      extended-circuit-id
       |     |     +--ro neighbor-snpa?                  snpa
       |     |     +--ro usage?                          level
       |     |     +--ro hold-timer?                     rt-types:timer-
value-seconds16
       |     |     |       rt-types:timer-value-seconds16
       |     |     +--ro neighbor-priority?              uint8
       |     |     +--ro lastuptime?                     yang:timestamp
       |     |     +--ro state?                          adj-state-type
       |     +--ro event-counters
       |     |  +--ro adjacency-changes?             uint32
       |     |  +--ro adjacency-number?              uint32
       |     |  +--ro init-fails?                    uint32
       |     |  +--ro adjacency-rejects?             uint32
       |     |  +--ro id-len-mismatch?               uint32
       |     |  +--ro max-area-addresses-mismatch?   uint32
       |     |  +--ro authentication-type-fails?     uint32
       |     |  +--ro authentication-fails?          uint32
       |     |  +--ro lan-dis-changes?               uint32
       |     +--ro packet-counters
       |        +--ro level* [level]
       |           +--ro level      level-number
       |           +--ro iih
       |           |  +--ro in?    uint32
       |           |  +--ro out?   uint32
       |           +--ro ish
       |           |  +--ro in?    uint32
       |           |  +--ro out?   uint32
       |           +--ro esh
       |           |  +--ro in?    uint32
       |           |  +--ro out?   uint32
       |           +--ro lsp
       |           |  +--ro in?    uint32
       |           |  +--ro out?   uint32
       |           +--ro psnp
       |           |  +--ro in?    uint32
       |           |  +--ro out?   uint32
       |           +--ro csnp
       |           |  +--ro in?    uint32
       |           |  +--ro out?   uint32
       |           +--ro unknown
       |              +--ro in?    uint32
       |              +--ro out?   uint32
       +--ro spf-log
       |  +--ro event* [id]
       |     +--ro id                    uint32
       |     +--ro spf-type?             enumeration
       |     +--ro level?                level-number
       |     +--ro schedule-timestamp?   yang:timestamp
       |     +--ro start-timestamp?      yang:timestamp
       |     +--ro end-timestamp?        yang:timestamp
       |     +--ro trigger-lsp* [lsp]
       |        +--ro lsp         lsp-id
       |        +--ro sequence?   uint32
       +--ro lsp-log
       |  +--ro event* [id]
       |     +--ro id                    uint32
       |     +--ro level?                level-number
       |     +--ro lsp
       |     |  +--ro lsp?        lsp-id
       |     |  +--ro sequence?   uint32
       |     +--ro received-timestamp?   yang:timestamp
       |     +--ro change?               identityref
       +--ro hostnames
       |  +--ro hostname* [system-id]
       |     +--ro system-id    system-id
       |     +--ro hostname?    string
       +--ro database
       |  +--ro level-db* [level]
       |     +--ro level    level-number
       |     +--ro lsp* [lsp-id]
       |        +--ro decoded-completed?               boolean
       |        +--ro raw-data?                        yang:hex-string
       |        +--ro lsp-id                           lsp-id
       |        +--ro checksum?                        uint16
       |        +--ro remaining-lifetime?              uint16
       |        +--ro sequence?                        uint32
       |        +--ro attributes?                      bits
       |        +--ro ipv4-addresses*                  inet:ipv4-address
       |        +--ro ipv6-addresses*                  inet:ipv6-address
       |        +--ro ipv4-te-routerid?                inet:ipv4-address
       |        +--ro ipv6-te-routerid?                inet:ipv6-address
       |        +--ro protocol-supported*              uint8
       |        +--ro dynamic-hostname?                string
       |        +--ro authentication
       |        |  +--ro authentication-type?   string
       |        |  +--ro authentication-key?    string
       |        +--ro mt-entries
       |        |  +--ro topology* []
       |        |     +--ro MT-ID?        uint16
       |        |     +--ro attributes?   bits
       |        +--ro router-capabilities* []
       |        |  +--ro flags?       bits
       |        |  +--ro node-tags {node-tag}?
       |        |  |  +--ro node-tag* []
       |        |  |     +--ro tag?   uint32
       |        |  +--ro binary?      binary
       |        +--ro is-neighbor
       |        |  +--ro neighbor* []
       |        |     +--ro neighbor-id?      system-id
       |        |     +--ro i-e?              boolean
       |        |     +--ro default-metric?   std-metric
       |        |     +--ro delay-metric
       |        |     |  +--ro metric?      std-metric
       |        |     |  +--ro supported?   boolean
       |        |     +--ro expense-metric
       |        |     |  +--ro metric?      std-metric
       |        |     |  +--ro supported?   boolean
       |        |     +--ro error-metric
       |        |        +--ro metric?      std-metric
       |        |        +--ro supported?   boolean
       |        +--ro extended-is-neighbor
       |        |  +--ro neighbor* []
       |        |     +--ro neighbor-id?   system-id
       |        |     +--ro metric?        wide-metric
       |        +--ro ipv4-internal-reachability
       |        |  +--ro prefixes* []
       |        |     +--ro up-down?          boolean
       |        |     +--ro i-e?              boolean
       |        |     +--ro ip-prefix?        inet:ipv4-address
       |        |     +--ro prefix-len?       uint8
       |        |     +--ro default-metric?   std-metric
       |        |     +--ro delay-metric
       |        |     |  +--ro metric?      std-metric
       |        |     |  +--ro supported?   boolean
       |        |     +--ro expense-metric
       |        |     |  +--ro metric?      std-metric
       |        |     |  +--ro supported?   boolean
       |        |     +--ro error-metric
       |        |        +--ro metric?      std-metric
       |        |        +--ro supported?   boolean
       |        +--ro ipv4-external-reachability
       |        |  +--ro prefixes* []
       |        |     +--ro up-down?          boolean
       |        |     +--ro i-e?              boolean
       |        |     +--ro ip-prefix?        inet:ipv4-address
       |        |     +--ro prefix-len?       uint8
       |        |     +--ro default-metric?   std-metric
       |        |     +--ro delay-metric
       |        |     |  +--ro metric?      std-metric
       |        |     |  +--ro supported?   boolean
       |        |     +--ro expense-metric
       |        |     |  +--ro metric?      std-metric
       |        |     |  +--ro supported?   boolean
       |        |     +--ro error-metric
       |        |        +--ro metric?      std-metric
       |        |        +--ro supported?   boolean
       |        +--ro extended-ipv4-reachability
       |        |  +--ro prefixes* []
       |        |     +--ro up-down?                 boolean
       |        |     +--ro ip-prefix?               inet:ipv4-address
       |        |     +--ro prefix-len?              uint8
       |        |     +--ro metric?                  wide-metric
       |        |     +--ro tag*                     uint32
       |        |     +--ro tag64*                   uint64
       |        |     +--ro external-prefix-flag?    boolean
       |        |     +--ro readvertisement-flag?    boolean
       |        |     +--ro node-flag?               boolean
       |        |     +--ro ipv4-source-router-id?   inet:ipv4-address
       |        |     +--ro ipv6-source-router-id?   inet:ipv6-address
       |        +--ro mt-is-neighbor
       |        |  +--ro neighbor* []
       |        |     +--ro MT-ID?         uint16
       |        |     +--ro neighbor-id?   system-id
       |        |     +--ro metric?        wide-metric
       |        +--ro mt-extended-ipv4-reachability
       |        |  +--ro prefixes* []
       |        |     +--ro MT-ID?                   uint16
       |        |     +--ro up-down?                 boolean
       |        |     +--ro ip-prefix?               inet:ipv4-address
       |        |     +--ro prefix-len?              uint8
       |        |     +--ro metric?                  wide-metric
       |        |     +--ro tag*                     uint32
       |        |     +--ro tag64*                   uint64
       |        |     +--ro external-prefix-flag?    boolean
       |        |     +--ro readvertisement-flag?    boolean
       |        |     +--ro node-flag?               boolean
       |        |     +--ro ipv4-source-router-id?   inet:ipv4-address
       |        |     +--ro ipv6-source-router-id?   inet:ipv6-address
       |        +--ro mt-ipv6-reachability
       |        |  +--ro prefixes* []
       |        |     +--ro MT-ID?                   uint16
       |        |     +--ro up-down?                 boolean
       |        |     +--ro ip-prefix?               inet:ipv6-address
       |        |     +--ro prefix-len?              uint8
       |        |     +--ro metric?                  wide-metric
       |        |     +--ro tag*                     uint32
       |        |     +--ro tag64*                   uint64
       |        |     +--ro external-prefix-flag?    boolean
       |        |     +--ro readvertisement-flag?    boolean
       |        |     +--ro node-flag?               boolean
       |        |     +--ro ipv4-source-router-id?   inet:ipv4-address
       |        |     +--ro ipv6-source-router-id?   inet:ipv6-address
       |        +--ro ipv6-reachability
       |           +--ro prefixes* []
       |              +--ro up-down?                 boolean
       |              +--ro ip-prefix?               inet:ipv6-address
       |              +--ro prefix-len?              uint8
       |              +--ro metric?                  wide-metric
       |              +--ro tag*                     uint32
       |              +--ro tag64*                   uint64
       |              +--ro external-prefix-flag?    boolean
       |              +--ro readvertisement-flag?    boolean
       |              +--ro node-flag?               boolean
       |              +--ro ipv4-source-router-id?   inet:ipv4-address
       |              +--ro ipv6-source-router-id?   inet:ipv6-address
       +--ro local-rib
       |  +--ro route* [prefix]
       |     +--ro prefix       inet:ip-prefix
       |     +--ro next-hops
       |     |  +--ro next-hop* [next-hop]
       |     |     +--ro outgoing-interface?   if:interface-ref
       |     |     +--ro next-hop              inet:ip-address
       |     +--ro metric?      uint32
       |     +--ro level?       level-number
       |     +--ro route-tag?   uint32
       +--ro system-counters
          +--ro level* [level]
             +--ro level                            level-number
             +--ro corrupted-lsps?                  uint32
             +--ro authentication-type-fails?       uint32
             +--ro authentication-fails?            uint32
             +--ro database-overload?               uint32
             +--ro own-lsp-purge?                   uint32
             +--ro manual-address-drop-from-area?   uint32
             +--ro max-sequence?                    uint32
             +--ro sequence-number-skipped?         uint32
             +--ro id-len-mismatch?                 uint32
             +--ro partition-changes?               uint32
             +--ro lsp-errors?                      uint32
             +--ro spf-runs?                        uint32

   rpcs:
    +---x clear-adjacency
    |  +---w input
    |     +---w routing-protocol-instance-name    instance-state-ref
    |     +---w level?                            level
    |     +---w interface?                        string
    +---x clear-database
       +---w input
          +---w routing-protocol-instance-name    instance-state-ref
          +---w level?                            level

   notifications:
    +---n database-overload
    |  +--ro routing-instance?        string
    |  +--ro routing-protocol-name?   string
    |  +--ro isis-level?              level
    |  +--ro overload?                enumeration
    +---n lsp-too-large
    |  +--ro routing-instance?        string
    |  +--ro routing-protocol-name?   string
    |  +--ro isis-level?              level
    |  +--ro interface-name?          string
    |  +--ro interface-level?         level
    |  +--ro extended-circuit-id?     extended-circuit-id
    |  +--ro pdu-size?                uint32
    |  +--ro lsp-id?                  lsp-id
    +---n if-state-change
    |  +--ro routing-instance?        string
    |  +--ro routing-protocol-name?   string
    |  +--ro isis-level?              level
    |  +--ro interface-name?          string
    |  +--ro interface-level?         level
    |  +--ro extended-circuit-id?     extended-circuit-id
    |  +--ro state?                   if-state-type
    +---n corrupted-lsp-detected
    |  +--ro routing-instance?        string
    |  +--ro routing-protocol-name?   string
    |  +--ro isis-level?              level
    |  +--ro lsp-id?                  lsp-id
    +---n attempt-to-exceed-max-sequence
    |  +--ro routing-instance?        string
    |  +--ro routing-protocol-name?   string
    |  +--ro isis-level?              level
    |  +--ro lsp-id?                  lsp-id
    +---n id-len-mismatch
    |  +--ro routing-instance?        string
    |  +--ro routing-protocol-name?   string
    |  +--ro isis-level?              level
    |  +--ro interface-name?          string
    |  +--ro interface-level?         level
    |  +--ro extended-circuit-id?     extended-circuit-id
    |  +--ro pdu-field-len?           uint8
    |  +--ro raw-pdu?                 binary
    +---n max-area-addresses-mismatch
    |  +--ro routing-instance?        string
    |  +--ro routing-protocol-name?   string
    |  +--ro isis-level?              level
    |  +--ro interface-name?          string
    |  +--ro interface-level?         level
    |  +--ro extended-circuit-id?     extended-circuit-id
    |  +--ro max-area-addresses?      uint8
    |  +--ro raw-pdu?                 binary
    +---n own-lsp-purge
    |  +--ro routing-instance?        string
    |  +--ro routing-protocol-name?   string
    |  +--ro isis-level?              level
    |  +--ro interface-name?          string
    |  +--ro interface-level?         level
    |  +--ro extended-circuit-id?     extended-circuit-id
    |  +--ro lsp-id?                  lsp-id
    +---n sequence-number-skipped
    |  +--ro routing-instance?        string
    |  +--ro routing-protocol-name?   string
    |  +--ro isis-level?              level
    |  +--ro interface-name?          string
    |  +--ro interface-level?         level
    |  +--ro extended-circuit-id?     extended-circuit-id
    |  +--ro lsp-id?                  lsp-id
    +---n authentication-type-failure
    |  +--ro routing-instance?        string
    |  +--ro routing-protocol-name?   string
    |  +--ro isis-level?              level
    |  +--ro interface-name?          string
    |  +--ro interface-level?         level
    |  +--ro extended-circuit-id?     extended-circuit-id
    |  +--ro raw-pdu?                 binary
    +---n authentication-failure
    |  +--ro routing-instance?        string
    |  +--ro routing-protocol-name?   string
    |  +--ro isis-level?              level
    |  +--ro interface-name?          string
    |  +--ro interface-level?         level
    |  +--ro extended-circuit-id?     extended-circuit-id
    |  +--ro raw-pdu?                 binary
    +---n version-skew
    |  +--ro routing-instance?        string
    |  +--ro routing-protocol-name?   string
    |  +--ro isis-level?              level
    |  +--ro interface-name?          string
    |  +--ro interface-level?         level
    |  +--ro extended-circuit-id?     extended-circuit-id
    |  +--ro protocol-version?        uint8
    |  +--ro raw-pdu?                 binary
    +---n area-mismatch
    |  +--ro routing-instance?        string
    |  +--ro routing-protocol-name?   string
    |  +--ro isis-level?              level
    |  +--ro interface-name?          string
    |  +--ro interface-level?         level
    |  +--ro extended-circuit-id?     extended-circuit-id
    |  +--ro raw-pdu?                 binary
    +---n rejected-adjacency
    |  +--ro routing-instance?        string
    |  +--ro routing-protocol-name?   string
    |  +--ro isis-level?              level
    |  +--ro interface-name?          string
    |  +--ro interface-level?         level
    |  +--ro extended-circuit-id?     extended-circuit-id
    |  +--ro raw-pdu?                 binary
    |  +--ro reason?                  string
    +---n protocols-supported-mismatch
    |  +--ro routing-instance?        string
    |  +--ro routing-protocol-name?   string
    |  +--ro isis-level?              level
    |  +--ro interface-name?          string
    |  +--ro interface-level?         level
    |  +--ro extended-circuit-id?     extended-circuit-id
    |  +--ro raw-pdu?                 binary
    |  +--ro protocols*               uint8
    +---n lsp-error-detected
    |  +--ro routing-instance?        string
    |  +--ro routing-protocol-name?   string
    |  +--ro isis-level?              level
    |  +--ro interface-name?          string
    |  +--ro interface-level?         level
    |  +--ro extended-circuit-id?     extended-circuit-id
    |  +--ro lsp-id?                  lsp-id
    |  +--ro raw-pdu?                 binary
    |  +--ro error-offset?            uint32
    |  +--ro tlv-type?                uint8
    +---n adjacency-state-change
    |  +--ro routing-instance?        string
    |  +--ro routing-protocol-name?   string
    |  +--ro isis-level?              level
    |  +--ro interface-name?          string
    |  +--ro interface-level?         level
    |  +--ro extended-circuit-id?     extended-circuit-id
    |  +--ro neighbor?                string
    |  +--ro neighbor-system-id?      system-id
    |  +--ro state?                   adj-state-type
    |  +--ro reason?                  string
    +---n lsp-received
    |  +--ro routing-instance?        string
    |  +--ro routing-protocol-name?   string
    |  +--ro isis-level?              level
    |  +--ro interface-name?          string
    |  +--ro interface-level?         level
    |  +--ro extended-circuit-id?     extended-circuit-id
    |  +--ro lsp-id?                  lsp-id
    |  +--ro sequence?                uint32
    |  +--ro received-timestamp?      yang:timestamp
    |  +--ro neighbor-system-id?      system-id
    +---n lsp-generation
       +--ro routing-instance?        string
       +--ro routing-protocol-name?   string
       +--ro isis-level?              level
       +--ro lsp-id?                  lsp-id
       +--ro sequence?                uint32
       +--ro send-timestamp?          yang:timestamp

2.5.  Authentication Parameters

   The module enables authentication configuration through the IETF key-
   chain module ([I-D.ietf-rtgwg-yang-key-chain]).  The IS-IS module
   imports the "ietf-key-chain" module and reuses some groupings to
   allow global and per interface configuration of authentication.  If a
   global authentication is configured, an implementation SHOULD
   authenticate PSNPs, CSNPs and LSPs with the authentication parameters
   supplied.  The authentication of hello PDUs can be activated on a per
   interface basis.

2.6.  IGP/LDP synchronization

   [RFC5443] defines a mechanism where IGP needs to be synchronized with
   LDP.  An "ldp-igp-sync" feature has been defined in the model to
   support this mechanism.  The "mpls/ldp/igp-sync" leaf under
   "interface" allows activation of the mechanism on a per interface
   basis.  The "mpls/ldp/igp-sync" container in the global configuration
   is empty on purpose and is not required for the activation.  The goal
   of this empty container is to allow easy augmentation with additional
   parameters like timers for example.

2.7.  ISO parameters

   As IS-IS protocol is based on ISO protocol suite, some ISO parameters
   may be required.

   This module augments interface configuration model to support ISO
   configuration parameters.

   The clns-mtu can be defined under the interface.

2.8.  IP FRR

   This YANG model supports LFA ([RFC5286]) and remote LFA ([RFC7490])
   as IP FRR techniques.  The "fast-reroute" container may be augmented
   by other models to support other IPFRR flavors (MRT, TILFA ...).

   The current version of the model supports activation of LFA and
   remote LFA at interface only.  The global "lfa" container is present
   but kept empty to allow augmentation with vendor specific properties
   like policies.

   Remote LFA is considered as a child of LFA.  Remote LFA cannot be
   enabled if LFA is not enabled.

   The "candidate-disabled" allows to mark an interface to not be used
   as a backup.

2.9.  Operational States

   Operational states are provided in the module in various places:

   o  system-counters: provides statistical informations about the
      global system.

   o  interface : provides configuration state informations for each
      interface.

   o  adjacencies: provides state informations about current IS-IS
      adjacencies.

   o  spf-log: provides informations about SPF events on the node.  This
      SHOULD be implemented as a wrapping buffer.

   o  lsp-log: provides informations about LSP events on the node
      (reception of an LSP or modification of local LSP).  This SHOULD
      be implemented as a wrapping buffer and an implementation MAY
      decide to log refresh LSPs or not.

   o  local-rib: provides the IS-IS internal routing table view.

   o  database: provides details on the current LSDB.

   o  hostnames: provides informations about system-id to hostname
      mappings.

   o  fast-reroute: provides informations about IP FRR.

3.  RPC Operations

   The "ietf-isis" module defines two RPC operations:

   o  clear-isis-database: reset the content of a particular IS-IS
      database and restart database synchronization with the neighbors.

   o  clear-isis-adjacency: restart a particular set of IS-IS
      adjacencies.

4.  Notifications

   The "ietf-isis" module introduces some notifications :

      database-overload : raised when overload condition is changed.

      lsp-too-large : raised when the system tries to propagate a too
      large PDU.

      corrupted-lsp-detected : raised when the system find that an LSP
      that was stored in memory has become corrupted.

      attempt-to-exceed-max-sequence : This notification is sent when
      the system wraps the 32-bit sequence counter of an LSP.

      id-len-mismatch : This notification is sent when we receive a PDU
      with a different value for the System ID length.

      max-area-addresses-mismatch : This notification is sent when we
      receive a PDU with a different value for the Maximum Area
      Addresses.

      own-lsp-purge : This notification is sent when the system receives
      a PDU with its own system ID and zero age.

      sequence-number-skipped : This notification is sent when the
      system receives a PDU with its own system ID and different
      contents.  The system has to reissue the LSP with a higher
      sequence number.

      authentication-type-failure : This notification is sent when the
      system receives a PDU with the wrong authentication type field.

      authentication-failure : This notification is sent when the system
      receives a PDU with the wrong authentication information.

      version-skew : This notification is sent when the system receives
      a PDU with a different protocol version number.

      area-mismatch : This notification is sent when the system receives
      a Hello PDU from an IS that does not share any area address.

      rejected-adjacency : This notification is sent when the system
      receives a Hello PDU from an IS but does not establish an
      adjacency for some reason.

      protocols-supported-mismatch : This notification is sent when the
      system receives a non pseudonode LSP that has no matching protocol
      supported.

      lsp-error-detected : This notification is sent when the system
      receives a LSP with a parse error.

      adjacency-change : This notification is sent when an IS-IS
      adjacency moves to Up state or to Down state.

      lsp-received : This notification is sent when a LSP is received.

      lsp-generation : This notification is sent when a LSP is
      regenerated.

5.  Interaction with Other YANG Modules

   The "isis" configuration container augments the "/rt:routing/
   rt:control-plane-protocols/control-plane-protocol" container of the
   ietf-routing [I-D.ietf-netmod-routing-cfg] module by defining IS-IS
   specific parameters.

   The "isis" module augments "/if:interfaces/if:interface" with ISO
   specific parameters.

   The "isis" operational state container augments the "/rt:routing-
   state/rt:control-plane-protocols/control-plane-protocol" container of
   the ietf-routing module by defining IS-IS specific operational
   states.

   Some IS-IS specific routes attributes are added to route objects of
   the ietf-routing module by augmenting "/rt:routing-
   state/rt:ribs/rt:rib/rt:routes/rt:route".

   The modules defined in this document use some groupings from ietf-
   keychain [I-D.ietf-rtgwg-yang-key-chain].

6.  IS-IS YANG Module

   <CODE BEGINS> file "ietf-isis@2018-05-25.yang" "ietf-yang@2018-07-02.yang"
   module ietf-isis {
     yang-version 1.1;
     namespace "urn:ietf:params:xml:ns:yang:ietf-isis";

     prefix isis;

     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 6021 - Common YANG Data Types";
     }

     import ietf-yang-types {
       prefix yang;
       reference "RFC 6021 - Common YANG Data Types";
     }

     import ietf-interfaces {
       prefix "if";
       reference "RFC 8343 - A YANG Data Model for Interface
                  Management (NDMA Version)";
     }

     import ietf-key-chain {
       prefix "key-chain";
       reference "RFC 8177 - YANG Data Model for Key Chains";
     }

     import ietf-routing-types {
       prefix "rt-types";
       reference "RFC 8291 - Common YANG Data Types for the
                  Routing Area";
     }

     import iana-routing-types {
       prefix "iana-rt-types";
       reference "RFC 8291 - Common YANG Data Types for the
                  Routing Area";
     }

     import ietf-bfd-types {
       prefix "bfd-types";
       reference "RFC XXXX - YANG Data Model for Bidirectional
                  Forwarding Detection (BFD)";
     }

     organization
       "IETF IS-IS Working Group";

     contact
       "WG List:  &lt;mailto:isis-wg@ietf.org&gt;

       Editor:    Stephane Litkowski
             &lt;mailto:stephane.litkowski@orange.com&gt;

           Derek Yeung
             &lt;mailto:derek@arrcus.com&gt;
           Acee Lindem
             &lt;mailto:acee@cisco.com&gt;
           Jeffrey Zhang
             &lt;mailto:zzhang@juniper.net&gt;
           Ladislav Lhotka
             &lt;mailto:llhotka@nic.cz&gt;
           Yi Yang
             &lt;mailto:yiya@cisco.com&gt;
           Dean Bogdanovic
             &lt;mailto:deanb@juniper.net&gt;
           Kiran Agrahara Sreenivasa
             &lt;mailto:kkoushik@brocade.com&gt;
           Yingzhen Qu
             &lt;mailto:yiqu@cisco.com&gt;
                   Jeff Tantsura
                     &lt;mailto:jefftant.ietf@gmail.com&gt;

       ";

     description
       "The YANG module defines a generic configuration model for
        IS-IS common across all of the vendor implementations.";

     revision 2017-05-25 2018-07-02 {
       description
         "Initial revision.";
       reference "RFC XXXX";
     }

     /* Identities */

     identity isis {
       base rt:routing-protocol;
       description "Identity for the IS-IS routing protocol.";
     }

     identity isis-adjacency-change {
       description "Identity for the IS-IS routing protocol
                    adjacency state.";
     }

     identity clear-isis-database {
       description "Identity for the IS-IS routing protocol
                    database reset action.";
     }

     identity clear-isis-adjacency {
       description "Identity for the IS-IS routing protocol
                    adjacency reset action.";
     }

     identity lsp-log-reason {
       description "Base identity for an LSP change log reason.";
     }

     identity refresh {
       base lsp-log-reason;
       description
         "Identity used when the LSP log reason is
          a refresh LSP received.";
     }

     identity content-change {
       base lsp-log-reason;
       description
         "Identity used when the LSP log reason is
          a change in the content of the LSP.";
     }

     /* Feature definitions */

     feature ietf-spf-delay {
       description
         "Support of IETF SPF delay algorithm.";
       reference "RFC XXXX - SPF Back-off algorithm for link
                  state IGPs";
     }
     feature bfd {
       description
         "Support for BFD detection of IS-IS neighbor reachability.";
       reference "RFC 5880 - Bidirectional Forwarding Detection (BFD)
                  RFC 5881 - Bidirectional Forwarding Detection
                  (BFD) for IPv4 and IPv6 (Single Hop)";
     }
     feature key-chain {
       description
         "Support of keychain for authentication.";
       reference "RFC8177 - YANG Data Model for Key Chains";
     }
     feature node-flag {
       description
         "Support of node-flag advertisement
          as prefix attribute";
       reference "RFC7794 - IS-IS Prefix Attributes for
                  Extended IP and IPv6 Reachability";
     }
     feature node-tag {
       description
         "Support of node tag.";
       reference "RFC7917 - Advertising Node Administrative Tags
                  in IS-IS";
     }
     feature ldp-igp-sync {
       description
         "Support of synchronization between IS-IS and LDP.";
       reference "RFC5443 - LDP IGP Synchronization";
     }
     feature fast-reroute {
       description
         "Support of IP Fast Reroute.";
     }
     feature nsr {
       description
         "Support of
          Non Stop Non-Stop Routing.";
     }
     feature lfa {
       description
         "Support of Loop Free Loop-Free Alternates.";
       reference "RFC5286 - Basic Specification of IP Fast-Reroute:
                  Loop-free Alternates";
     }
     feature remote-lfa {
       description
         "Support of remote Loop Free Alternates.";
       reference "RFC7490 - Remote Loop-Free Alternate Fast Reroute";
     }

     feature overload-max-metric {
       description
         "Support of overload by setting
          all links to max metric.";
     }
     feature prefix-tag {
       description
        "Add 32bit tag to prefixes";
         "Support for 32-bit prefix tags";
       reference "RFC5130 - A Policy Control Mechanism in
                  IS-IS Using Administrative Tags";
     }
     feature prefix-tag64 {
       description
        "Add 64bit tag to prefixes";
         "Support for 64-bit prefix tags";
       reference "RFC5130 - A Policy Control Mechanism in
                  IS-IS Using Administrative Tags";
     }
     feature auto-cost {
       description
         "Use an automated assignment of metrics.";
     }
     feature ipv4-router-id {
       description
         "Support of IPv4 router ID configuration under IS-IS.";
     }

     feature ipv6-router-id {
       description
         "Support of IPv6 router ID configuration under IS-IS.";
     }

     feature multi-topology {
       description
         "Multitopology routing support.";
       reference "RFC5120 - M-IS-IS: Multi Topology Routing in IS-IS";
     }
     feature nlpid-control {
       description
         "This feature controls the advertisement
          of support NLPID within IS-IS configuration.";
     }
     feature graceful-restart {
       description
         "Graceful restart support.";
       reference "RFC5306 - Restart Signaling in IS-IS";
     }

     feature lsp-refresh {
       description
         "Configuration of LSP refresh interval.";
     }

     feature maximum-area-addresses {
       description
         "Support of maximum-area-addresses config.";
     }

     feature admin-control {
       description
         "Control administrative state of IS-IS.";
     }

     /* Type definitions */

     typedef instance-state-ref {
       type leafref {
         path "/rt:routing-state/"
           +"rt:control-plane-protocols/rt:control-plane-protocol/"
           +"rt:name";
       }
       description
         "This type is used for leaves that reference state data of for
          an IS-IS protocol instance.";
     }

     typedef circuit-id {
       type uint8;
       description
         "This type defines the circuit ID
          associated with an interface.";

     }

     typedef extended-circuit-id {
       type uint32;
       description
         "This type defines the extended circuit ID
          associated with an interface.";
     }

     typedef interface-type {
       type enumeration {
         enum broadcast {
           description
             "Broadcast interface type.";
         }
         enum point-to-point {
           description
           "Point to point
             "Point-to-point interface type.";
         }
       }
       description
         "This type defines the type of adjacency
          to be established on the interface.
       This is affecting
          The interface-type determines the type
          of hello message that would be is used.";

     }

     typedef level {
       type enumeration {
         enum "level-1" {
           description
             "This enum describes L1 only indicates L1-only capability.";
         }
         enum "level-2" {
           description
             "This enum describes L2 only indicates L2-only capability.";
         }
         enum "level-all" {
           description
             "This enum describes indicates capability for both levels capability."; levels.";
         }
       }
       default "level-all";
       description
         "This type defines IS-IS level of an object.";

     }
     typedef adj-state-type {
       type enumeration {
         enum "up" {
           description
             "This state describes that
             "State indicates the adjacency is established.";
         }
         enum "down" {
           description
             "This state describes that
             "State indicates the adjacency is NOT established.";
         }
         enum "init" {
           description
             "This state describes that
             "State indicates the adjacency is establishing.";
         }
         enum "failed" {
           description
             "This state describes that
             "State indicates the adjacency is failed.";
         }
       }
       description
         "This type defines states of an adjacency";
     }

     typedef if-state-type {
       type enumeration {
         enum "up" {
           description "Up state.";

         }
         enum "down" {
           description "Down state";
         }
       }
       description
         "This type defines states the state of an interface";
     }

     typedef level-number {
       type uint8 {
         range "1 .. 2";
       }
       description
         "This type defines a the current IS-IS level.";
     }

     typedef lsp-id {
       type string {
         pattern
           '[0-9A-Fa-f]{4}\.[0-9A-Fa-f]{4}\.[0-9A-Fa-f]'
           +'{4}\.[0-9][0-9]-[0-9][0-9]';
       }
       description
         "This type defines the IS-IS LSP ID format using a
          pattern,
        system id looks like : An example LSP ID is 0143.0438.AeF0.02-01";
     }

     typedef area-address {
       type string {
         pattern '[0-9A-Fa-f]{2}\.([0-9A-Fa-f]{4}\.){0,3}';
       }
       description
         "This type defines the area address format.";
     }

     typedef snpa {
       type string {
         length "0 .. 20";
       }
       description
         "This type defines the Subnetwork Point
          of Attachement (SNPA) format.";
     }

     typedef system-id {
       type string {
         pattern
           '[0-9A-Fa-f]{4}\.[0-9A-Fa-f]{4}\.[0-9A-Fa-f]{4}';
       }
       description
         "This type defines IS-IS system id system-id using pattern,
        system id looks like :
          An example system-id is 0143.0438.AeF0";
     }

     typedef wide-metric {
       type uint32 {
         range "0 .. 16777215";
       }
       description
         "This type defines wide style format of IS-IS metric.";
     }

     typedef std-metric {
       type uint8 {
         range "0 .. 63";
       }
       description
         "This type defines old style format of IS-IS metric.";
     }

     typedef mesh-group-state {
       type enumeration {
         enum "meshinactive" "mesh-inactive" {
           description
             "Interface is not part of a mesh group.";
         }
         enum "meshset" "mesh-set" {
           description
             "Interface is part of a mesh group.";
         }
         enum "meshblocked" "mesh-blocked" {
           description
             "LSPs must not be flooded over that this interface.";
         }
       }
       description
         "This type describes meshgroup mesh group state of an interface";
     }

     /* Grouping definitions for configuration and ops state */

     grouping adjacency-state {
       container adjacencies {
         config false;
         list adjacency {
           leaf neighbor-systype neighbor-sys-type {
             type level;
             description
             "Type
               "Level capability of neighboring system";
           }
           leaf neighbor-sysid {
             type system-id;
             description
               "The system-id of the neighbor";
           }
           leaf neighbor-extended-circuit-id {
             type extended-circuit-id;
             description
               "Circuit ID of the neighbor";
           }
           leaf neighbor-snpa {
             type snpa;
             description
               "SNPA of the neighbor";
           }
           leaf usage {
             type level;
             description
               "Define the level(s) activated on the adjacency.
                On a p2p link this might be level 1 and 2,
                but on a LAN, the usage will be level 1
                between peers at L1 level 1 or level 2 between
                peers at L2."; level 2.";
           }
           leaf hold-timer {
             type rt-types:timer-value-seconds16;
             units seconds;
             description
               "The holding time in seconds for this
                adjacency. This value is based on
                received hello PDUs and the elapsed
                time since receipt.";
           }
           leaf neighbor-priority {
             type uint8 {
               range "0 .. 127";
             }
             description
               "Priority of the neighboring IS for becoming
                the DIS.";
           }
           leaf lastuptime {
             type yang:timestamp;
             description
               "When the adjacency most recently entered
                state 'up', measured in hundredths of a
                second since the last reinitialization of
                the network management subsystem.
                The value is 0 if the adjacency has never
                been in state 'up'.";
           }
           leaf state {
             type adj-state-type;
             description
               "This leaf describes the state of the interface.";
           }

           description
             "List of operational adjacencies.";
         }
         description
           "This container lists the adjacencies of
            the local node.";
       }
       description
         "Adjacency state";
     }

     grouping fast-reroute-global-state {
       container protected-routes {
         config false;
         list af-stats {
           key "af prefix alternate";

           leaf af {
             type iana-rt-types:address-family;
             description
               "Address-family";
           }
           leaf prefix {
             type string;
             description
               "Protected prefix.";
           }
           leaf alternate {
             type string;
             description
               "Alternate nexthop for the prefix.";
           }
           leaf alternate-type {
             type enumeration {
               enum equalcost equal-cost {
                 description
                   "ECMP alternate.";
               }
               enum lfa {
                 description
                   "LFA alternate.";
               }
               enum remote-lfa {
                 description
                   "Remote LFA alternate.";
               }
               enum tunnel {
                 description
                   "Tunnel based alternate
                    (like RSVP-TE or GRE).";
               }
               enum ti-lfa {
                 description
                   "TI LFA
                   "TI-LFA alternate.";
               }
               enum mrt {
                 description
                   "MRT alternate.";
               }
               enum other {
                 description
                   "Unknown alternate type.";
               }
             }
             description
               "Type of alternate.";
           }
           leaf best {
             type boolean;
             description
               "describes
               "Indicates if the alternate is the best one."; preferred.";
           }
           leaf non-best-reason {
             type string;
             description
               "Information field to describe why the alternate
                is not best.";
           }
           leaf protection-available {
             type bits {
               bit nodeprotect node-protect {
                 position 0;
                 description
                   "Node protection available.";
               }
               bit linkprotect link-protect {
                 position 1;
                 description
                   "Link protection available.";
               }
               bit srlgprotect srlg-protect {
                 position 2;
                 description
                   "SRLG protection available.";
               }
               bit downstreamprotect downstream-protect {
                 position 3;
                 description
                   "Downstream protection available.";
               }
               bit other {
                 position 4;
                 description
                   "Other protection available.";
               }
             }
             description
              "Describes protection "Protection provided by the alternate.";
           }
           leaf alternate-metric1 {
             type uint32;
             description
               "Metric from PLR Point of Local Repair (PLR) to
                destination through the alternate path.";
           }
           leaf alternate-metric2 {
             type uint32;
             description
               "Metric from PLR to the alternate node";
           }
           leaf alternate-metric3 {
             type uint32;
             description
               "Metric from alternate node to the destination";
           }
           description
             "Per AF
             "Per-AF protected prefix statistics.";
         }
         description
           "List of prefixes that are protected.";
       }

       container nonprotected-routes unprotected-routes {
         config false;
         list af-stats {
           key "af prefix";

           leaf af {
             type iana-rt-types:address-family;

             description "Address-family";
           }
           leaf prefix {
             type string;
             description
               "Protected "Unprotected prefix.";
           }
           description
             "Per AF unprotected prefix statistics.";
         }
         description
           "List of prefixes that are not protected.";
       }

       list protection-statistics {
         key frr-protection-method;
         config false;
         leaf frr-protection-method {
           type string;
           description "Protection method used.";
         }
         list af-stats {
           key af;

           leaf af {
             type iana-rt-types:address-family;

             description "Address-family";
           }
           leaf total-routes {
             type uint32;
             description "Total prefixes.";
           }
           leaf unprotected-routes {
             type uint32;
             description
               "Total of prefixes who that are not protected.";
           }
           leaf protected-routes {
             type uint32;
             description
               "Total of prefixes who that are protected.";
           }
           leaf linkprotected-routes {
             type uint32;
             description
               "Total of prefixes who that are link protected.";
           }
           leaf nodeprotected-routes {
             type uint32;
             description
               "Total of prefixes who that are node protected.";
           }
           description
             "Per AF protected prefix statistics.";
         }

         description "Global protection statistics.";

       }
       description "IPFRR states.";
     }

     grouping notification-instance-hdr {
       description
       "This group describes common instance
         "Instance specific IS-IS notification data for notifications."; grouping";
       leaf routing-instance {
         type string;
         description
         "Describes the name "Name of the routing-instance instance.";
       }
       leaf routing-protocol-name {
         type string;
         description
         "Describes the name "Name of the IS-IS instance.";
       }
       leaf isis-level {
         type level;
         description
         "Describes the IS-IS "IS-IS level of the instance.";
       }
     }

     grouping notification-interface-hdr {
       description
       "This group describes common interface
         "Interface specific IS-IS notification data for notifications."; grouping";
       leaf interface-name {
         type string;
         description
         "Describes the name of the IS-IS interface."; "IS-IS interface name";
       }
       leaf interface-level {
         type level;
         description
         "Describes the IS-IS "IS-IS level of the interface.";
       }
       leaf extended-circuit-id {
         type extended-circuit-id;
         description
         "Describes the extended "Eextended circuit-id of the interface.";
       }
     }

     grouping route-content {
       description
       "This group add isis-specific
         "IS-IS protocol-specific route properties."; properties grouping.";
       leaf metric {
         type uint32;
         description
         "This leaf describes IS-IS "IS-IS metric of a route.";
       }
       leaf-list tag {
         type uint64;
         description
         "This leaf describes list
           "List of tags associated with the route. The leaf
            describes both
          32bits 32-bit and 64bits 64-bit tags.";
       }
       leaf route-type {
         type enumeration {
           enum l2-up-internal {
             description "Level 2 internal route
                          and not leaked to a lower level";
           }
           enum l1-up-internal {
             description "Level 1 internal route
                          and not leaked to a lower level";
           }
           enum l2-up-external {
             description "Level 2 external route
                          and not leaked to a lower level";
           }
           enum l1-up-external {
             description "Level 1 external route
                          and not leaked to a lower level";
           }
           enum l2-down-internal {
             description "Level 2 internal route
                          and leaked to a lower level";
           }
           enum l1-down-internal {
             description "Level 1 internal route
                          and leaked to a lower level";
           }
           enum l2-down-external {
             description "Level 2 external route
                          and leaked to a lower level";
           }
           enum l1-down-external {
             description "Level 1 external route
                          and leaked to a lower level";
           }
         }
         description
         "This leaf describes the type of IS-IS route."; "IS-IS route type.";
       }
     }

     grouping admin-control {
       leaf enable {
         if-feature admin-control;
         type boolean;
         default true;
         description
           "Control the administrative state.";
       }
       description
         "Grouping for admin control.";
     }

     grouping fast-reroute-global-cfg {
       description
       "This group defines
         "IPFRR global configuration of IPFRR."; grouping";
       container lfa {
         if-feature lfa;
         description
           "This container may be augmented with global
            parameters for LFA. Creating the container has no
            effect on LFA activation.";
       }
     }

     grouping fast-reroute-if-cfg {
       description
       "This group defines
         "IPFRR interface configuration of IPFRR."; grouping";
       container lfa {
         if-feature lfa;
         uses lfa-if-cfg;
         container level-1 {
           uses lfa-if-cfg;
           description
             "LFA level 1 config";
         }
         container level-2 {
           uses lfa-if-cfg;
           description
             "LFA level 2 config";
         }
         description
           "LFA config";
       }
     }

     grouping ietf-spf-delay-cfg {
       leaf initial-delay {
         type rt-types:timer-value-milliseconds;
         units msec;
         description
           "Delay used while in QUIET state.";
       }
       leaf short-delay {
         type rt-types:timer-value-milliseconds;
         units msec;
         description
           "Delay used while in SHORT_WAIT state.";
       }
       leaf long-delay {
         type rt-types:timer-value-milliseconds;
         units msec;
         description
           "Delay used while in LONG_WAIT state.";
       }

       leaf hold-down {
         type rt-types:timer-value-milliseconds;
         units msec;
         description
           "Timer used to consider an IGP stability period.";
       }
       leaf time-to-learn {
         type rt-types:timer-value-milliseconds;
         units msec;
         description
           "Duration used to learn all the IGP events
            related to a single component failure.";
       }

       description
         "Grouping for IETF SPF delay configuration.";
     }

     grouping ietf-spf-delay-state {
       leaf current-state {
         type enumeration {
           enum "quiet" {
             description "QUIET state";
           }
           enum "short-wait" {
             description "SHORT_WAIT state";
           }
           enum "long-wait" {
             description "LONG_WAIT state";
           }
         }
         config false;
         description
           "Current SPF backoff algorithm state.";
       }
       leaf remaining-time-to-learn {
         type rt-types:timer-value-milliseconds;
         units "msec";
         config false;
         description
           "Remaining time until time-to-learn timer fires.";
       }
       leaf remaining-hold-down {
         type rt-types:timer-value-milliseconds;
         units "msec";
         config false;
         description
           "Remaining time until hold-down timer fires.";
       }
       leaf last-event-received {
         type yang:timestamp;
         config false;
         description
           "Time of last IGP event received";
       }
       leaf next-spf-time {
         type yang:timestamp;
         config false;
         description
           "Time when next SPF has been scheduled.";
       }
       leaf last-spf-time {
         type yang:timestamp;
         config false;
         description
           "Time of last SPF computation.";
       }
       description
         "Grouping for IETF SPF delay operational states.";
     }

     grouping local-rib {
       description "Local-rib grouping.";
       container local-rib {
         config false;
         description "Local-rib.";
         list route {
           key "prefix";
           description "Routes";
          leaf prefix { "List of IS-IS local RIB Routes";
           leaf prefix {
             type inet:ip-prefix;
             description "Destination prefix.";
           }
           container next-hops {
             description "All next hops for the route.";
             list next-hop {
               key "next-hop";
               description "List of next hop for the route";
               leaf outgoing-interface {
                 type if:interface-ref;
                 description
                   "Name of the outgoing interface.";
               }
               leaf next-hop {
                 type inet:ip-address;
                 description "Nexthop address.";
               }
             }
           }
           leaf metric {
             type uint32;
             description "Metric for this route.";
           }
           leaf level {
             type level-number;
             description "Level number for this route.";
           }
           leaf route-tag {
             type uint32;
             description "Route tag for this route.";
           }
         }
       }
     }

     grouping isis-node-tag-cfg {
       description "IS-IS node tag config.";
       container node-tags {
         if-feature node-tag;
         list node-tag {
           key tag;
           leaf tag {
             type uint32;
             description
               "Node tag value.";
           }
           description
             "List of tags.";
         }
         description
           "Container for node tags.";
       }
     }
     grouping authentication-global-cfg {
       choice authentication-type {
         case key-chain {
           if-feature key-chain;
           leaf key-chain {
             type key-chain:key-chain-ref;
             description
               "Reference to a key-chain.";
           }
         }
         case password {
           leaf key {
             type string;
             description
               "This leaf describes specifies the authentication key.";
           }
           leaf crypto-algorithm {
             type identityref {
               base key-chain:crypto-algorithm;
             }
             description
               "Cryptographic algorithm associated with key.";
           }
         }
         description "Choice of authentication.";
       }
       description "Grouping for global auth authentication config.";
     }

     grouping metric-type-global-cfg {
       leaf value {
         type enumeration {
           enum wide-only {
             description
               "Advertise new metric style only (RFC5305)";
           }
           enum old-only {
             description
               "Advertise old metric style only (RFC1195)";
           }
           enum both {
             description "Advertise both metric
              styles"; metricstyles";
           }
         }
         default wide-only;
         description
           "This leaf describes the type
           "Type of metric to be generated.
           Wide-only generated:
            - wide-only means only new metric style
               is generated,
            - old-only means that only old style metric
              is generated,
           and
            - both means that both are advertised.
            This leaf is only affecting IPv4 metrics.";
       }
       description
         "Grouping for global metric style config.";
     }

     grouping default-metric-global-cfg {
       leaf value {
         type wide-metric;
         default "10";
         description  "Value of the metric";
       }
       description
            "Grouping for global
         "Global default metric config."; config grouping.";
     }

     grouping overload-global-cfg {
       leaf status {
         type boolean;
         default false;
         description
           "This leaf defines specifies the overload status.";
       }
       description "Grouping for overload bit config.";
     }

     grouping overload-max-metric-global-cfg {
       leaf timeout {
         type rt-types:timer-value-seconds16;
         units "seconds";
         description
           "This leaf defines the timeout in seconds
           "Timeout (in seconds) of the overload condition.";
       }
       description
        "Grouping for overload-max-metric config.";
         "Overload maximum metric configuration grouping";
     }

     grouping route-preference-global-cfg {
       choice granularity {
         case detail {
           leaf internal {
             type uint8;
             description
                    "This leaf defines the protocol
               "Protocol preference for internal routes.";
           }
           leaf external {
             type uint8;
             description
                    "This leaf defines the protocol
               "Protocol preference for external routes.";
           }
         }
         case coarse {
           leaf default {
             type uint8;
             description
                    "This leaf defines the protocol
               "Protocol preference for all IS-IS routes.";
           }
         }
         description
           "Choice for implementation of route preference.";
       }
       description
       "This grouping defines how
         "Global route preference is configured."; grouping";
     }

     grouping hello-authentication-cfg {
       choice authentication-type {
         case key-chain {
           if-feature key-chain;
           leaf key-chain {
             type key-chain:key-chain-ref;
             description "Reference to a key-chain.";
           }
         }
         case password {
           leaf key {
             type string;
             description
               "This leaf describes the
                 authentication key."; "Authentication key specification";
           }
           leaf crypto-algorithm {
             type identityref {
               base key-chain:crypto-algorithm;
             }
             description
               "Cryptographic algorithm associated with key.";
           }
         }
         description "Choice of authentication.";
       }
       description "Grouping for hello authentication.";
     }
     grouping hello-interval-cfg {
       leaf value {
         type rt-types:timer-value-seconds16;
         units "seconds";
         default 10;
         description
       "This leaf defines the interval of
           "Interval (in seconds) between successive hello
            messages.";
       }

       description "Interval between hello messages.";
     }

     grouping hello-multiplier-cfg {
       leaf value {
         type uint16;
         default 3;
         description
       "This leaf defines the number
           "Number of missed hello failed messages prior to be received before
            declaring the adjacency down.";
       }
       description
       "This grouping defines the number
           "Number of missed hello failed messages prior to be received before
        declaring the
            adjacency down."; down grouping.";
     }

     grouping priority-cfg {
       leaf value {
         type uint8 {
           range "0 .. 127";
         }
         default 64;
         description
       "This leaf describes the priority
           "Priority of
       the interface for DIS election.";
       }

       description
       "This grouping leaf describes the
       priority of
       the interface
       for "Interface DIS election."; election priority grouping";
     }

     grouping metric-cfg {
       leaf value {
         type wide-metric;
         default "10";
         description "Metric value.";
       }
       description
         "Grouping for interface metric"; "Interface metric grouping";
     }
     grouping lfa-if-cfg {
       leaf candidate-disabled {
         type boolean;
         default false;
         description
           "Prevent the interface to be used as backup.";
       }
       leaf enable {
         type boolean;
         default false;
         description
         "Activates LFA.
         This
           "LFA Activation - this model assumes activation
            of per-prefix LFA.";
       }

       container remote-lfa {
         if-feature remote-lfa;
         leaf enable {
           type boolean;
           default false;
           description
             "Activates rLFA.";
         }
         description
         "remote "Remote LFA configuration.";
       }
       description "Grouping for LFA interface configuration";
     }

     grouping isis-global-cfg {
       description
       "Defines the IS-IS "IS-IS global configuration."; configuration grouping";

       uses admin-control;

       leaf level-type {
         type level;
         default "level-all";
         description
             "This leaf describes the type
           "Level of an IS-IS node.
             A node - can be level-1-only,
            level-2-only or level-1-2.
             "; level-1-2.";
       }

       leaf system-id {
         type system-id;
         description
             "This leaf defines the system-id "System-id of the node.";
       }

       leaf maximum-area-addresses {
         if-feature maximum-area-addresses;
         type uint8;
         default 3;
         description
             "Defines the maximum "Maximum areas supported.";
       }

       leaf-list area-address {
         type area-address;
         description
           "List of areas supported by the protocol instance.";
       }

       container mpls {
         leaf ipv4-router-id {
           if-feature ipv4-router-id;
           type inet:ipv4-address;
           description
             "Router ID value that would be used in TLV 134.";
         }
         leaf ipv6-router-id {
           if-feature ipv6-router-id;
           type inet:ipv6-address;
           description
             "Router ID value that would be used in TLV 140.";
         }
         container ldp {
           container igp-sync {
             if-feature ldp-igp-sync;
             description
               "This container may be augmented with global
                parameters for igp-ldp-sync.";
           }
           description "LDP related configuration.";
         }
         description
              "This container handles mpls config."; "MPLS configuration";
       }
       container auto-cost {
         if-feature auto-cost;
         leaf reference-bandwidth {
           type uint32;
           units "bps";
           description
                 "This leaf defines the bandwidth "Bandwidth for calculating metric.";
         }
         leaf enable {
           type boolean;
           default false;
           description "Enable/disable auto-cost.";
         }
         description
               "This container defines the auto-cost "Auto-cost configuration.";

       }
       leaf lsp-mtu {
         type uint16;
         units "bytes";
         default 1492;
         description
             "This leaf describes the maximum
           "Maximum size of a an LSP PDU in bytes.";
       }
       leaf lsp-lifetime {
         type uint16 {
           range "1..65535";
         }
         units "seconds";
         description
             "This leaf describes the lifetime
           "Lifetime of the router
              LSP router's LSPs in seconds.";
       }
       leaf lsp-refresh {
         if-feature lsp-refresh;
         type rt-types:timer-value-seconds16;
         units "seconds";
         description
             "This leaf describes the refresh
           "Refresh interval of the
              router LSP router's LSPs in seconds.";
       }
       container graceful-restart {
         if-feature graceful-restart;
         leaf enable {
           type boolean;
           default false;
           description
               "Control enabling the feature."; "Enable graceful restart.";
         }
         leaf restart-interval {
           type rt-types:timer-value-seconds16;
           units "seconds";
           description
             "Interval in seconds (in seconds) to attempt graceful restart prior
              to failing"; failure.";
         }
         leaf helper-enable {
           type boolean;
           default true;
           description
              "If enabled, the
             "Enable local IS-IS router can act as graceful restart helper.";
         }
         description
             "This container activates graceful restart."; "Graceful-Restart Configuration.";
       }

       container nsr {
         if-feature nsr;
         description "Non-Stop Routing (NSR) config state."; configuration.";
         leaf enable {
           type boolean;
           default false;
           description "Enable/Disable NSR."; Non-Stop Routing (NSR).";
         }
       }

       uses isis-node-tag-cfg;

       container authentication {
         uses authentication-global-cfg;

         container level-1 {
           uses authentication-global-cfg;
           description "level-1 specific cfg"; configuration";
         }
         container level-2 {
           uses authentication-global-cfg;
           description "level-2 specific cfg"; configuration";
         }
         description "authentication "Authentication global cfg.
              It covers configuration for
                      both LSPs and SNPs.";
       }

       container metric-type {
         uses metric-type-global-cfg;
         container level-1 {
           uses metric-type-global-cfg;
           description "level-1 specific cfg"; configuration";
         }
         container level-2 {
           uses metric-type-global-cfg;
           description "level-2 specific cfg"; configuration";
         }
         description "Metric style global cfg."; configuration";
       }

       container default-metric {
         uses default-metric-global-cfg;
         container level-1 {
           uses default-metric-global-cfg;
           description "level-1 specific cfg"; configuration";
         }
         container level-2 {
           uses default-metric-global-cfg;
           description "level-2 specific cfg"; configuration";
         }
         description "Default metric global cfg."; configuration";
       }

       container afs {
         if-feature nlpid-control;
         list af {
           key af;
           leaf af {
             type iana-rt-types:address-family;
             description "Address-family";
           }
           leaf enable {
             type boolean;
             description
                    "Describes the activation state of "Activate the
                     AF."; address family.";
           }
           description
                 "This list permits activation
             "List of new address families."; families and whether or not they
              are activated.";
         }
         description
               "Container for address-families"; "Address Family configuration";
       }

       container preference {
         uses route-preference-global-cfg;
         description
               "This container defines the "Router preference configuration for IS-IS
                      protocol preference."; instance route installation";
       }

       container overload {
         uses overload-global-cfg;
         description
             "This container describes if the router is
              set to "Router protocol instance overload state."; state
                      configuration";
       }

       container overload-max-metric {
         if-feature overload-max-metric;
         uses overload-max-metric-global-cfg;
         description
             "This container describes if the router is
              set to
           "Router protocol instance overload state using max-metric
              advertisement."; maximum
            metric advertisement configuration.";
       }
     }

     grouping isis-global-topologies-cfg {
       description
      "Per topology config."; "Per-topology configuration";
       container default-metric {
         uses default-metric-global-cfg;
         container level-1 {
           uses default-metric-global-cfg;
           description "level-1 specific cfg"; configuration";
         }
         container level-2 {
           uses default-metric-global-cfg;
           description "level-2 specific cfg"; configuration";
         }
         description "Default metric per
          topology cfg."; per-topology configuration";
       }
       uses isis-node-tag-cfg;
     }

     grouping isis-if-cfg {
       description
       "Grouping for interface cfg."; "Interface configuration grouping";
       leaf level-type {
         type level;
         default "level-all";
         description
         "This leaf defines the associated IS-IS "IS-IS level of the interface.";
       }
       leaf lsp-pacing-interval {
         type rt-types:timer-value-milliseconds;
         units "milliseconds";
         default 33;
         description
         "This leaf defines the interval
           "Interval (in milli-seconds) between LSP transmissions in milli-seconds";
            transmissions.";
       }
       leaf lsp-retransmit-interval {
         type rt-types:timer-value-seconds16;
         units "seconds";
         description
         "This leaf defines the interval
           "Interval (in seconds) between
         retransmission of LSP"; LSP
            retransmissions.";
       }
       leaf passive {
         type boolean;
         default "false";
         description
         "This leaf defines if
           "Indicates whetherthe interface is in passive mode (IS-IS
            not running, running but network is advertised).";
       }
       leaf csnp-interval {
         type rt-types:timer-value-seconds16;
         units "seconds";
         default 10;
         description
         "This leaf defines the interval of
            "Interval (in seconds) between CSNP messages.";
       }
       container hello-padding {
         leaf enable {
           type boolean;
           default "true";
           description
           "Status of
             "IS-IS Hello-padding activation.
            By default, the implementation shall
            pad HELLOs."; activation - enabled by default.";
         }
         description
         "This container handles IS-IS "IS-IS hello padding configuration.";
       }
       leaf mesh-group-enable {
         type mesh-group-state;
         description
         "Describes the mesh group state of
          the interface."; "IS-IS interface mesh-group state";
       }
       leaf mesh-group {
         when "../mesh-group-enable = 'meshset'" 'mesh-set'" {
           description
             "Only valid when mesh-group-enable equals to meshset";
         }
         type uint8;
         description
         "Describes the mesh group ID of
          the interface."; "IS-IS interface mesh-group ID.";
       }
       leaf interface-type {
         type interface-type;
         default "broadcast";
         description
         "This leaf defines the type
           "Type of adjacency to be established on the interface. This is affecting
            dictates the type of hello
         message messages that would be are used.";
       }

       uses admin-control;

       leaf-list tag {
         if-feature prefix-tag;
         type uint32;
         description
         "This leaf defines list
           "List of tags associated with the interface.";
       }
       leaf-list tag64 {
         if-feature prefix-tag64;
         type uint64;
         description
         "This leaf defines list
           "List of 64bits 64-bit tags associated with the interface.";
       }
       leaf node-flag {
         if-feature node-flag;
         type boolean;
         default false;
         description
           "Set prefix as a node representative prefix.";
       }
       container hello-authentication {
         uses hello-authentication-cfg;
         container level-1 {
           uses hello-authentication-cfg;
           description "level-1 specific cfg"; configuration";
         }
         container level-2 {
           uses hello-authentication-cfg;
           description "level-2 specific cfg"; configuration";
         }
         description
           "Authentication type to be used in hello messages.";
       }
       container hello-interval {
         uses hello-interval-cfg;
         container level-1 {
           uses hello-interval-cfg;
           description "level-1 specific cfg"; configuration";
         }
         container level-2 {
           uses hello-interval-cfg;
           description "level-2 specific cfg"; configuration";
         }
         description "Interval between hello messages.";
       }
       container hello-multiplier {
         uses hello-multiplier-cfg;
         container level-1 {
           uses hello-multiplier-cfg;
           description "level-1 specific cfg"; configuration";
         }
         container level-2 {
           uses hello-multiplier-cfg;
           description "level-2 specific cfg"; configuration";
         }
         description "Hello multiplier configuration.";
       }
       container priority {
         must '../interface-type = "broadcast"' {
           error-message
             "Priority only applies to broadcast interfaces.";
           description "Check for broadcast interface.";
         }
         uses priority-cfg;
         container level-1 {
           uses priority-cfg;
           description "level-1 specific cfg"; configuration";
         }
         container level-2 {
           uses priority-cfg;
           description "level-2 specific cfg"; configuration";
         }
         description "Priority for DIS election.";
       }
       container metric {
         uses metric-cfg;
         container level-1 {
           uses metric-cfg;
           description "level-1 specific cfg"; configuration";
         }
         container level-2 {
           uses metric-cfg;
           description "level-2 specific cfg"; configuration";
         }
         description "Metric configuration.";
       }
       container bfd {
         if-feature bfd;
         description "BFD Client Configuration.";
         uses bfd-types:client-cfg-parms;

         reference "draft-ietf-bfd-yang-xx.txt:
                    YANG Data Model for Bidirectional Forwarding
                    Detection (BFD)";
       }
       container afs {
         if-feature nlpid-control;
         list af {
           key af;
           leaf af {
             type iana-rt-types:address-family;
             description  "Address-family";
           }
           description "List of AFs.";
         }
         description
               "Container for "Interface address-families";
       }
       container mpls {
         container ldp {
           leaf igp-sync {
             if-feature ldp-igp-sync;
             type boolean;
             default false;
             description "Enables IGP/LDP sync."; synchronization";

           }
           description "LDP protocol related configurations."; configuration.";
         }
         description
         "Container for MPLS specific "MPLS configuration for IS-IS."; IS-IS interfaces";
       }
     }

     grouping isis-if-topologies-cfg {
       description "IS-IS interface topology cfg."; configuration.";
       container metric {
         uses metric-cfg;
         container level-1 {
           uses metric-cfg;
           description "level-1 specific cfg"; configuration";
         }
         container level-2 {
           uses metric-cfg;
           description "level-2 specific cfg"; configuration";
         }
         description "Metric IS-IS interface configuration.";
       }
     }

     grouping system-counters {
       container system-counters {
         config false;
         list level {
           key level;

           leaf level {
             type level-number;
             description
             "This leaf describes the IS-IS "IS-IS level.";
           }
           leaf corrupted-lsps {
             type uint32;
             description
               "Number of corrupted in-memory LSPs detected.
                LSPs received from the wire with a bad
                checksum are silently dropped and not counted.
                LSPs received from the wire with parse errors
                are counted by lsp-errors.";
           }
           leaf authentication-type-fails {
             type uint32;
             description
                "Number of authentication type mismatches.";
           }
           leaf authentication-fails {
             type uint32;
             description
               "Number of authentication key failures.";
           }
           leaf database-overload {
             type uint32;
             description
               "Number of times the database has become
                overloaded.";
           }
           leaf own-lsp-purge {
             type uint32;
             description
               "Number of times a zero-aged copy of the system's
                own LSP is received from some other IS-IS node.";
           }
           leaf manual-address-drop-from-area {
             type uint32;
             description
               "Number of times a manual address
                has been dropped from the area.";
           }
           leaf max-sequence {
             type uint32;
             description
               "Number of times the system has attempted
                to exceed the maximum sequence number.";
           }
           leaf sequence-number-skipped {
             type uint32;
             description
               "Number of times a sequence number skip has
                occured.";
           }
           leaf id-len-mismatch {
             type uint32;
             description
               "Number of times a PDU is received with a
                different value for the ID field length
              from
                than that of the receiving system.";
           }
           leaf partition-changes {
             type uint32;
             description
               "Number of partition changes detected.";
           }
           leaf lsp-errors {
             type uint32;
             description
               "Number of LSPs with errors we have received.";
           }
           leaf spf-runs {
             type uint32;
             description
               "Number of times we ran SPF at this level.";
           }
           description
             "List of supported levels.";
         }
         description
         "The container defines a list of
           "List counters for the IS."; IS-IS protocol instance";
       }
       description
       "Grouping for system counters."; "System counters grouping.";
     }

     grouping event-counters {
       container event-counters {
         config false;
         leaf adjacency-changes {
           type uint32;
           description
             "The number of times an adjacency state change has
              occured on this interface.";
         }
         leaf adjacency-number {
           type uint32;
           description
             "The number of adjacencies on this interface.";
         }
         leaf init-fails {
           type uint32;
           description
             "The number of times initialization of this
              interface has failed. This counts events such
              as PPP NCP failures. Failures to form an
              adjacency are counted by adjacency-rejects.";
         }
         leaf adjacency-rejects {
           type uint32;
           description
             "The number of times an adjacency has been
              rejected on this interface.";
         }
         leaf id-len-mismatch {
           type uint32;
           description
             "The number of times an IS-IS PDU with an ID
              field length different from that for this
              system has been received on this interface.";
         }
         leaf max-area-addresses-mismatch {
           type uint32;
           description
             "The number of times an IS-IS PDU has been
              received on this interface with
                according the
              max area address field
                differs differing from that for
                this system has been received on of
              this
                interface."; system.";
         }
         leaf authentication-type-fails {
           type uint32;
           description
             "Number of authentication type mismatches.";
         }
         leaf authentication-fails {
           type uint32;
           description
             "Number of authentication key failures.";
         }
         leaf lan-dis-changes {
           type uint32;
           description
             "The number of times the DIS has changed on this
              interface at this level. If the interface type is point to point,
                the
              point-to-point,the count is zero.";
         }
         description
             "Provides protocol "IS-IS interface event counters.";
       }
       description
         "Grouping for IS-IS interface event counters";
     }

     grouping packet-counters {
       container packet-counters {
         config false;
         list level {
           key level;

           leaf level {
             type level-number;
             description
             "This leaf describes the IS-IS "IS-IS level.";
           }
           container iih {
             leaf in {
               type uint32;
               description "Received IIH PDUs.";
             }
             leaf out {
               type uint32;
               description "Sent IIH PDUs.";
             }
             description
             "The number "Number of IIH PDUs received/sent.";
           }
           container ish {
             leaf in {
               type uint32;
               description "Received ISH PDUs.";
             }
             leaf out {
               type uint32;
               description "Sent ISH PDUs.";
             }
             description
             "The number of ISH
               "ISH PDUs received/sent.";
           }
           container esh {
             leaf in {
               type uint32;
               description "Received ESH PDUs.";
             }
             leaf out {
               type uint32;
               description "Sent ESH PDUs.";
             }
             description
             "The number "Number of ESH PDUs received/sent.";
           }
           container lsp {
             leaf in {
               type uint32;
               description "Received LSP PDUs.";
             }
             leaf out {
               type uint32;
               description "Sent LSP PDUs.";
             }
             description
             "The number "Number of LSP PDUs received/sent.";
           }
           container psnp {
             leaf in {
               type uint32;
               description "Received PSNP PDUs.";
             }
             leaf out {
               type uint32;
               description "Sent PSNP PDUs.";
             }
             description
             "The number "Number of PSNP PDUs received/sent.";
           }
           container csnp {
             leaf in {
               type uint32;
               description "Received CSNP PDUs.";
             }
             leaf out {
               type uint32;
               description "Sent CSNP PDUs.";
             }
             description
             "The number "Number of CSNP PDUs received/sent.";
           }
           container unknown {
             leaf in {
               type uint32;
               description "Received unknown PDUs.";
             }
             leaf out {
               type uint32;
               description "Sent unknown PDUs.";
             }
             description
             "The number "Number of unknown PDUs received/sent.";
           }
           description
             "List of packet counter for supported levels."; llevels.";
         }
         description
         "Provides packet "Packet counters per IS-IS level.";
       }
       description
         "Grouping for per IS-IS Level packet counters.";
     }

     grouping spf-log {
       container spf-log {
         config false;
         list event {
           key id;

           leaf id {
             type uint32;
             description
             "This leaf defines the event identifier.
              This is a
               "Event identifier -  purely internal value.";
           }
           leaf spf-type {
             type enumeration {
               enum full {
                 description
                 "Computation done is a Full SPF."; "Full SPF computation.";
               }
               enum route-only {
                 description
                 "Computation done is a
                   "Route reachability computation
                  only."; only SPF computation";
               }
             }
             description
             "This leaf describes the type "Type of SPF computation
             used."; performed.";
           }
           leaf level {
             type level-number;
             description
             "This leaf describes the
               "IS-IS level affected by the
             the computation."; number for SPF computation";
           }
           leaf schedule-timestamp {
             type yang:timestamp;
             description
             "This leaf describes the timestamp
               "Timestamp of when the SPF computation was
                scheduled.";
           }
           leaf start-timestamp {
             type yang:timestamp;
             description
             "This leaf describes the timestamp
               "Timestamp of when the SPF computation was started.";
           }
           leaf end-timestamp {
             type yang:timestamp;
             description
             "This leaf describes the timestamp
               "Timestamp of when the SPF computation was ended.";
           }
           list trigger-lsp {
             key "lsp";
             leaf lsp {
               type lsp-id;
               description
               "This leaf describes the LSPID
                 "LSPID of the LSP."; LSP triggering SPF computation.";
             }
             leaf sequence {
               type uint32;
               description
               "This leaf describes the sequence
                 "Sequence number of the LSP."; LSP triggering SPF
                  computation";
             }
             description
               "This leaf describes list of includes the LSPs that triggered the
                SPF computation.";

           }
           description
             "List of computation events.
           It is used events - implemented as a
              wrapping buffer.";
         }

         description
           "This container lists the SPF computation events.";
       }
       description "Grouping for spf-log events.";
     }

     grouping lsp-log {
       container lsp-log {
         config false;
         list event {
           key id;

           leaf id {
             type uint32;
             description
             "This leaf defines the event identifier.
              This is a
               "Event identifier -  purely internal value.";
           }
           leaf level {
             type level-number;
             description
             "This leaf describes the
               "IS-IS level affected by the
             the computation."; number for LSP";
           }
           container lsp {
             leaf lsp {

               type lsp-id;
               description
               "This leaf describes the LSPID
                 "LSPID of the LSP.";
             }
             leaf sequence {
               type uint32;
               description
               "This leaf describes the sequence
                 "Sequence number of the LSP.";
             }
             description
             "This
               "LSP identification container describes - either the received
                LSP
             , in case of local LSP update or the local
             LSP ID is referenced."; locally generated LSP.";
           }

           leaf received-timestamp {
             type yang:timestamp;
             description
             "This leaf describes the timestamp
               "Timestamp of when the LSP was received. In case
                of local LSP update, the timestamp refers to the
                local LSP update time.";
           }

           leaf change {
             type identityref {
               base lsp-log-reason;
             }
             description
             "This leaf describes the type "Type of change
             in the LSP."; LSP change.";
           }

           description
             "List of LSP events.
           It is used events - implemented as a
              wrapping buffer.";
         }

         description
         "This container lists the LSP
           "LSP reception events.
         Local and local LSP modification are also contained in the
         list."; origination events
            container.";

       } description "Grouping for LSP log.";
     }

     grouping hostname-db {
       container hostnames {
         config false;
         list hostname {
           key system-id;
           leaf system-id {
             type system-id;
             description
             "This leaf describes the system-id
               "System-id associated with the hostname.";
           }
           leaf hostname {
             type string;
             description
             "This leaf describes the hostname
               "Hostname associated with the system ID.";
           }
           description
             "List of system-id/hostname associations"; associations.";
         }
         description
         "This container describes the list
         of binding between
           "Hostname to system-id and
         hostnames."; mapping database.";
       }
       description
         "Grouping for hostname to systemid system-id mapping database.";

     }

     /* Groupings for the LSDB description */

     grouping prefix-reachability-attributes {
       description
       "This group defines
         "Grouping for extended reachability attributes of an
          IPv4 or IPv6 prefix.";

       leaf external-prefix-flag {
         type boolean;
         description "External prefix flag.";
       }
       leaf readvertisement-flag {
         type boolean;
         description "Readvertisement flag.";
       }
       leaf node-flag {
         type boolean;
         description "Node flag.";
       }
     }

     grouping prefix-ipv4-source-router-id {
       description
       "This group defines
         "Grouping for the IPv4 source router ID of a prefix
          advertisement.";

       leaf ipv4-source-router-id {
         type inet:ipv4-address;
         description "IPv4 Source router ID address.";
       }
     }

     grouping prefix-ipv6-source-router-id {
       description
       "This group defines
         "Grouping for the IPv6 source router ID of a prefix
          advertisement.";

       leaf ipv6-source-router-id {
         type inet:ipv6-address;
         description "IPv6 Source router ID address.";
       }
     }

     grouping prefix-attributes-extension {
       description "Prefix extended attributes.";
       uses prefix-reachability-attributes;
       uses prefix-ipv4-source-router-id;
       uses prefix-ipv6-source-router-id;
     }

     grouping prefix-ipv4-std {
       description
       "This group defines
         "Grouping for attributes of an IPv4 standard prefix.";
       leaf up-down {
         type boolean;
         description
         "This leaf expresses the value "Value of up/down bit.";
       }
       leaf i-e {
         type boolean;
         description
         "This leaf expresses the value "Value of I/E bit.";
       }
       leaf ip-prefix {
         type inet:ipv4-address;
         description
         "This leaf describes the IPv4 prefix"; "IPv4 prefix address";
       }
       leaf prefix-len {
         type uint8;
         description
         "This leaf describes the IPv4 "IPv4 prefix len in bits"; length (in bits)";
       }
       leaf default-metric {
         type std-metric;
         description
         "This leaf describes the "Default IS-IS default metric value"; for IPv4 prefix";
       }
       container delay-metric {
         leaf metric {
           type std-metric;
           description
           "This leaf describes the IS-IS "IS-IS delay metric value"; for IPv4 prefix";
         }
         leaf supported {
           type boolean;
           default "false";
           description
           "This leaf describes if the
             "Indicates whether IS-IS delay metric is supported.";
         }
         description
         "This container defines the IS-IS "IS-IS delay metric."; metric container.";
       }
       container expense-metric {
         leaf metric {
           type std-metric;
           description
           "This leaf describes the IS-IS "IS-IS expense metric value"; for IPv4 prefix";
         }
         leaf supported {
           type boolean;
           default "false";
           description
           "This leaf describes if the
             "Indicates whether IS-IS delay metric is supported.";
         }
         description
         "This container defines the IS-IS "IS-IS expense metric."; metric container.";
       }
       container error-metric {
         leaf metric {
           type std-metric;
           description
             "This leaf describes the IS-IS error metric value";
         }
         leaf supported {
           type boolean;
           default "false";
           description
           "This leaf describes if the "IS-IS error metric is supported."; for IPv4 prefix";
         }
         description
         "This container defines the IS-IS "IS-IS error metric."; metric container.";
       }
     }

     grouping prefix-ipv4-extended {
       description
       "This group defines
         "Grouping for attributes of an IPv4 extended prefix.";
       leaf up-down {
         type boolean;
         description
         "This leaf expresses the value  "Value of up/down bit.";
       }
       leaf ip-prefix {
         type inet:ipv4-address;
         description
         "This leaf describes the IPv4 prefix"; "IPv4 prefix address";
       }
       leaf prefix-len {
         type uint8;
         description
         "This leaf describes the IPv4 "IPv4 prefix len in bits"; length (in bits)";
       }

       leaf metric {
         type wide-metric;
         description
         "This leaf describes the IS-IS "IS-IS wide metric value";
       }
       leaf-list tag {
         type uint32;
         description
         "This leaf describes a list
           "List of 32-bit tags associated with the IPv4 prefix.";
       }
       leaf-list tag64 {
         type uint64;
         description
         "This leaf describes a list
           "List of 64-bit 32-bit tags associated with the IPv4 prefix.";
       }
       uses prefix-attributes-extension;
     }

     grouping prefix-ipv6-extended {
       description
       "This group defines "Grouping for attributes of an IPv6 prefix.";
       leaf up-down {
         type boolean;
         description
         "This leaf expresses the value "Value of up/down bit.";
       }
       leaf ip-prefix {
         type inet:ipv6-address;
         description
         "This leaf describes the IPv6 prefix"; "IPv6 prefix address";
       }
       leaf prefix-len {
         type uint8;
         description
         "This leaf describes the IPv4  "IPv4 prefix len in bits"; length (in bits)";
       }
       leaf metric {
         type wide-metric;
         description
         "This leaf describes the IS-IS  "IS-IS wide metric value";
       }
       leaf-list tag {
         type uint32;
         description
         "This leaf describes a list
           "List of 32-bit tags associated with the IPv4 prefix.";
       }
       leaf-list tag64 {
         type uint64;
         description
         "This leaf describes a list
           "List of 64-bit 32-bit tags associated with the IPv4 prefix.";
       }
       uses prefix-attributes-extension;
     }

     grouping neighbor-extended {
       description
       "This group defines
        "Grouping for attributes of an IS-IS extended neighbor.";
       leaf neighbor-id {
         type system-id;
         description
         "This leaf describes the system-id "System-id of the extended neighbor.";
       }
       leaf metric {
         type wide-metric;
         description
         "This leaf describes the IS-IS "IS-IS wide metric value"; for extended neighbor";
       }

     }

     grouping neighbor {
       description
       "This group defines attributes of an
        IS-IS  "IS-IS standard neighbor."; neighbor grouping.";
       leaf neighbor-id {
         type system-id;
         description
         "This leaf describes the system-id of the neighbor."; "IS-IS neighbor system-id";
       }
       leaf i-e {
         type boolean;
         description
         "This leaf expresses the value of I/E bit.";
           "Internal or External (I/E) Metric bit value";
       }
       leaf default-metric {
         type std-metric;
         description
         "This leaf describes the IS-IS "IS-IS default metric value";
       }
       container delay-metric {
         leaf metric {
           type std-metric;
           description
           "This leaf describes the IS-IS "IS-IS delay metric value";
         }
         leaf supported {
           type boolean;
           default "false";
           description
           "This leaf describes if the "IS-IS delay metric is supported."; supported";
         }
         description
         "This container defines the IS-IS "IS-IS delay metric."; metric container";
       }
       container expense-metric {
         leaf metric {
           type std-metric;
           description
           "This leaf describes the IS-IS "IS-IS delay expense metric value";
         }
         leaf supported {
           type boolean;
           default "false";
           description
           "This leaf describes if the "IS-IS delay expense metric is supported."; supported";
         }
         description
         "This container defines the IS-IS "IS-IS delay expense metric."; metric container";
       }
       container error-metric {
         leaf metric {
           type std-metric;
           description
           "This leaf describes the IS-IS "IS-IS error metric value";
         }
         leaf supported {
           type boolean;
           default "false";
           description
           "This leaf describes if the "IS-IS error metric is supported."; supported";
         }
         description
         "This container defines the IS-IS "IS-IS error metric."; metric container";
       }
     }

     grouping lsp-entry {
       description
       "This group defines attributes of an
        IS-IS "IS-IS LSP database entry."; entry groupting";

       leaf decoded-completed {
         type boolean;
         description
          "The IS-IS "IS-IS LSP body is fully decoded.";
       }
       leaf raw-data {
         type yang:hex-string;
         description
           "The hexadecial representation of the complete LSP in network byte
            network-byte order hexadecimal (NBO) as received or originated.";
       }
       leaf lsp-id {
         type lsp-id;
         description
         "This leaf describes the LSP "LSP ID of the LSP."; LSP";
       }
       leaf checksum {
         type uint16;
         description
         "This leaf describes the checksum of the LSP."; "LSP checksum";
       }
       leaf remaining-lifetime {
         type uint16;
         units "seconds";
         description
         "This leaf describes the remaining
           "Remaining lifetime
          in seconds before the (in seconds) until LSP expiration.";
       }
       leaf sequence {
         type uint32;
         description
           "This leaf describes the sequence number of the LSP.";
       }
       leaf attributes {
         type bits {
           bit PARTITIONNED partitioned {
             description
             "If set, the originator supports "Originator partition
              repair."; repair supported";
           }
           bit ATTACHED-ERROR attached-error {
             description
               "If set, the originator is attached to
                another area using the referred metric.";

           }
           bit ATTACHED-EXPENSE attached-expense {
             description
               "If set, the originator is attached to
                another area using the referred metric.";
           }
           bit ATTACHED-DELAY attached-delay {
             description
               "If set, the originator is attached to
                another area using the referred metric.";
           }
           bit ATTACHED-DEFAULT attached-default {
             description
               "If set, the originator is attached to
                another area using the referred metric.";
           }
           bit OVERLOAD overload {
             description
               "If set, the originator is overloaded,
                and must be avoided in path calculation.";
           }
         }
         description
         "This leaf describes attributes of the LSP."; "LSP attributes";
       }

       leaf-list ipv4-addresses {
         type inet:ipv4-address;
         description
          "This leaf describes the
           "List of IPv4 addresses of the node. IS-IS node - IS-IS
            reference is TLV 132.";
       }

       leaf-list ipv6-addresses {
         type inet:ipv6-address;
         description
         "This leaf describes the
           "List of IPv6 interface addresses of the node. IS-IS node - IS-IS
            reference is TLV 232.";
       }

       leaf ipv4-te-routerid {
         type inet:ipv4-address;
         description
          "This leaf describes the IPv4
           "IPv4 Traffic Engineering router ID of the node. IS-IS node -
            IS-IS reference is TLV 134.";
       }

       leaf ipv6-te-routerid {
         type inet:ipv6-address;
         description
         "This leaf describes the IPv6
           "IPv6 Traffic Engineering router ID of the node. IS-IS node -
            IS-IS reference is TLV 140.";
       }

       leaf-list protocol-supported {
         type uint8;
         description
         "This leaf describes the list
         "List of supported protocols. protocols of the IS-IS node -
          IS-IS reference is TLV 129.";
       }

       leaf dynamic-hostname {
         type string;
         description
         "This leaf describes the name
           "Host Name of the node. IS-IS node - IS-IS reference
            is TLV 137.";
       }

       container authentication {
         leaf authentication-type {
           type string;
           description
           "This leaf describes the authentication
             "Authentication type to be used."; used with IS-IS node.";
         }
         leaf authentication-key {
           type string;
           description
           "This leaf describes the authentication key
            to
             "Authentication keyto be used. For security reason, reasons,
              the authentication key MUST NOT be presented in
              plaintext format. Authors recommends It is recommended to use an MD5
              hash to present the authentication-key.";
         }
         description "This container describes
           "IS-IS node authentication information of the node. container -
            IS-IS reference is TLV 10.";
       }

       container mt-entries {
         list topology {
           description
             "List of topologies supported";

           leaf MT-ID {
             type uint16 {
               range "0 .. 4095";
             }
             description
             "This leaf defines the
               "Multi-Topolgoy identifier of a topology.";
           }

           leaf attributes {
             type bits {
               bit OVERLOAD overload {
                 description
                   "If set, the originator is overloaded,
                    and must be avoided in path calculation.";
               }
               bit ATTACHED attached {
                 description
                   "If set, the originator is attached to
                   another area using the referred metric.";
               }
             }
             description
             "This leaf describes attributes
               "Attributes of the LSP for the associated
                topology.";
           }
          description
           "List of topologies supported.";
         }
         description
         "This container describes the
           "IS-IS node topology supported. information container -
            IS-IS reference is TLV 229.";
       }

       list router-capabilities {
         leaf flags {
           type bits {
             bit flooding {
               position 0;
               description
                 "If the S bit is set(1), set, the IS-IS Router CAPABILITY
                  TLV MUST be flooded across the entire routing
                  domain. If the S bit is
              not set(0), clear, the TLV MUST NOT
                  be leaked between levels. This bit MUST NOT
                   be altered during the TLV leaking.";
             }
             bit down {
               position 1;
               description
                 "When the IS-IS Router CAPABILITY TLV is leaked
                  from level-2 to level-1, the D bit MUST be set.
                  Otherwise, this bit MUST be clear.  IS-IS Router
                  capability TLVs with the D bit set MUST NOT be
                  leaked from level-1 to level-2.
              This is level-2 in to prevent
                  TLV looping.
              "; looping.";
             }

           }
           description
           "Flags associated with router capability."; "Router Capability Flags";
         }
         container node-tags {
           if-feature node-tag;
           list node-tag {
             leaf tag {
               type uint32;
               description "Node tag value.";
             }
             description "List of tags.";
          }
          description
           "Container for node of tags.";
           }
           description "Node Tag container";
         }

         leaf binary {
           type binary;
           description
           "This leaf describes the capability
             "Binary encoding of the node.
           Format is binary according to the protocol encoding."; IS-IS node capabilities";
         }
         description
         "This container describes the
           "IS-IS node capabilities of the node. container. This container may
            be extended with detailed
         information. information -  IS-IS
            reference is TLV 242.";
       }

       container is-neighbor {
         list neighbor {
           uses neighbor;
           description "List of neighbors.";
         }
         description
         "This leaf describes list of IS-IS neighbors.
           "Standard IS neighbors container - IS-IS reference is
            TLV 2.";
       }

       container extended-is-neighbor {
         list neighbor {
           uses neighbor-extended;
           description
             "List of neighbors."; extended IS neighbors";
         }
         description
         "This container describes list of IS-IS
           "Standard IS extended
         neighbors. neighbors container - IS-IS
            reference is TLV 22."; 22";
       }

       container ipv4-internal-reachability {
         list prefixes {
           uses prefix-ipv4-std;
           description "List of prefixes.";
         }
         description
         "This container describes list of IPv4
         "IPv4 internal reachability information. information container - IS-IS
          reference is TLV 128.";
       }

       container ipv4-external-reachability {
         list prefixes {
           uses prefix-ipv4-std;
           description "List of prefixes.";
         }
         description
         "This container describes list of IPv4
           "IPv4 external reachability information. information container -
            IS-IS reference is TLV 130.";
       }

       container extended-ipv4-reachability {
         list prefixes {
           uses prefix-ipv4-extended;
           description "List of prefixes.";
         }
         description
         "This container describes list of IPv4
           "IPv4 extended reachability information. information container -
            IS-IS reference is TLV 135.";
       }

       container mt-is-neighbor {
         list neighbor {
           leaf MT-ID mt-id {
             type uint16 {
               range "0 .. 4095";
             }
             description
             "This leaf defines the identifier
              of a topology."; "Multi-topology (MT) identifier";
           }
           uses neighbor-extended;
           description "List of neighbors.";
         }
         description
         "This container describes list of IS-IS
           "IS-IS multi-topology
          neighbors. neighbor container - IS-IS
            reference is TLV 223.";
       }

       container mt-extended-ipv4-reachability {
         list prefixes {
           leaf MT-ID mt-id {
             type uint16 {
               range "0 .. 4095";
             }
             description
             "This leaf defines the identifier
              of a topology.";  "Multi-topology (MT) identifier";
           }
           uses prefix-ipv4-extended;
           description "List of extended prefixes.";
         }
         description
         "This container describes list of IPv4
           "IPv4 multi-topolgy (MT) extended reachability
            information in multi-topology
         environment. container - IS-IS reference is TLV 235.";
       }

       container mt-ipv6-reachability {
         list prefixes {
           leaf MT-ID {
             type uint16 {
               range "0 .. 4095";
             }
             description
             "This leaf defines the identifier
              of a topology."; "Multi-topology (MT) identifier";
           }
           uses prefix-ipv6-extended;
           description "List of IPv6 extended prefixes.";
         }
         description
         "This container describes list of IPv6
           "IPv6 multi-topolgy (MT) extended reachability
            information in multi-topology
         environment. container - IS-IS reference is TLV 237.";
       }

       container ipv6-reachability {
         list prefixes {
           uses prefix-ipv6-extended;
           description "List of IPv6 prefixes.";
         }
         description
         "This container describes list of IPv6
           "IPv6 reachability information. information container - IS-IS
            reference is TLV 236.";
       }
     }

     grouping lsdb {
       description "Link State Database (LSDB) grouping";
       container database {
         config false;
         list level-db {
           key level;

           leaf level {
             type level-number;
             description
             "Current "LSDB level number"; number (1 or 2)";
           }
           list lsp {
             key lsp-id;
             uses lsp-entry;
             description "List of LSPs in LSDB."; LSDB";
           }
           description
           "This container describes the "LSP list of LSPs
           in the for LSDB level x database."; container";
         }
         description
         "This container describes IS-IS "IS-IS Link State
          databases."; database container";
       }
      description
       "Grouping for LSDB description.";
     }

     /* Augmentations */

     augment "/rt:routing/"
       +"rt:ribs/rt:rib/rt:routes/rt:route" {
       when "rt:source-protocol = 'isis:isis'" {
         description "IS-IS-specific route attributes.";
       }
       uses route-content;
       description
         "This augments route object in RIB with IS-IS-specific
          attributes.";
     }

     augment "/if:interfaces/if:interface" {
       leaf clns-mtu {
         type uint16;
         description
         "Defines CLNS "CLNS MTU of the interface."; interface";
       }
       description "ISO interface config.";
     }

     augment "/rt:routing/rt:control-plane-protocols/"
       +"rt:control-plane-protocol" {
       when "rt:type = 'isis:isis'" {
         description
           "This augment is only valid when routing protocol
            instance type is isis."; 'isis'";
       }
       description
         "This augments a routing protocol instance with IS-IS
          specific parameters.";
       container isis {
         must "count(area-address) > 0" {
           error-message
             "At least one area-address must be configured.";
           description
             "Enforce configuration of at least one area.";
         }

         uses isis-global-cfg;
         container fast-reroute {
           if-feature fast-reroute;
           uses fast-reroute-global-cfg;
           uses fast-reroute-global-state;
           description
                "IPFRR.";
             "IP Fast ReRoute (IPFRR) global container";
         }
         container spf-control {
           container ietf-spf-delay {
             if-feature ietf-spf-delay;
             uses ietf-spf-delay-cfg;
             uses ietf-spf-delay-state;
             description "IETF spf SPF delay algorithm configuration."; container";
           }
           description
               "Container for all SPF computation related
               operations.";
             "SPF computation-related information container";
         }
         container topologies {
           if-feature multi-topology;
           list topology {
             key "name";
             leaf enable {
               type boolean;
               description
                   "Control enabling of topologies"; "Topology enable configuration";
             }
             leaf name {
               type leafref {
                 path "../../../../../../rt:ribs/rt:rib/rt:name";
               }
               description "RIB";
                 "Routing Information Base (RIB) corresponding
                  to topology.";
             }

             uses isis-global-topologies-cfg;

             description "List of topologies";
           }
           description
               "Container for multi-topology"; "Multi-topology container";
         }
         container interfaces {
           list interface {
             key "name";
             leaf name {
               type if:interface-ref;

               description
                 "Reference to the interface within
                  the routing-instance.";
             }
             uses isis-if-cfg;
             container fast-reroute {
               if-feature fast-reroute;
               uses fast-reroute-if-cfg;
               description
                "IPFRR.";
                 "IP Fast ReRoute (IPFRR) interface container";
             }
             container topologies {
               if-feature multi-topology;
               list topology {
                 key name;

                 leaf name {
                   type leafref {
                     path "../../../../../../../../"+
                       "rt:ribs/rt:rib/rt:name";
                   }

                   description
                       "Name of RIB.";
                     "Routing Information Base (RIB) corresponding
                      to topology.";
                 }
                 uses isis-if-topologies-cfg;
                 description "List of topologies."; interface topologies";
               }
               description
               "Container for multi-topology"; "Multi-topology container";
             }
             uses adjacency-state;
             uses event-counters;
             uses packet-counters;
             description "List of IS-IS interfaces.";
           }
           description
             "This container defines IS-IS
             "IS-IS interface specific configuration objects."; container";
         }
         uses spf-log;
         uses lsp-log;
         uses hostname-db;
         uses lsdb;
         uses local-rib;
         uses system-counters;

         description
          "This container defines IS-IS specific configuration
           objects.";
           "IS-IS configuration/state top-level container";
       }
     }

     /* RPC methods */

     rpc clear-adjacency {
       description
         "This RPC request clears a particular set of IS-IS
          adjacencies. If the operation fails for IS-IS due to an internal
          reason, then the error-tag and error-app-tag should be
          set
        to a meaningful value."; indicating the reason for the failure.";
       input {

         leaf routing-protocol-instance-name {
           type instance-state-ref;
           mandatory "true";
           description
             "Name of the IS-IS protocol instance whose IS-IS
              information is being queried.

              If the corresponding IS-IS instance with name equal to the
            value of this parameter doesn't exist,
              then this the operation SHALL will fail with an error-tag of
              'data-missing' and an error-app-tag of
              'routing-protocol-instance-not-found'.";
         }
         leaf level {
           type level;
           description
             "IS-IS level of the adjacency to be cleared. If the
              IS-IS level is level-1-2, both level 1 and level 2
              adjacencies would be cleared.

              If the value provided is different from the one
              authorized in the enum type, then this the operation
              SHALL fail with an error-tag of 'data-missing' and
              an error-app-tag
            'bad-isis-level'.
           "; of 'bad-isis-level'.";
         }
         leaf interface {
           type string;
           description
           "Name of the IS-IS interface.
             "IS-IS interface name.

              If the corresponding IS-IS interface with name equal to the
            value of this parameter doesn't exist,
              then this the operation SHALL fail with an error-tag of
              'data-missing' and an error-app-tag of
              'isis-interface-not-found'.";
         }
       }
     }

     rpc clear-database {
       description
         "This RPC request clears a particular  IS-IS database. If
          the operation fails for an IS-IS internal reason, then
          the error-tag and error-app-tag should be set
        to a meaningful value.";
          indicating the reason for the failure.";
       input {
         leaf routing-protocol-instance-name {
           type instance-state-ref;
           mandatory "true";
           description
             "Name of the IS-IS protocol instance whose IS-IS
            information is
              database(s) is/are being queried. cleard.

              If the corresponding IS-IS instance with name equal to the
            value of this parameter doesn't exist,
              then this the operation SHALL will fail with an error-tag of
              'data-missing' and an error-app-tag of
              'routing-protocol-instance-not-found'.";
         }
         leaf level {
           type level;
           description
             "IS-IS level of the adjacency to be cleared. If the
              IS-IS level is level-1-2, both level 1 and level 2
           adjacencies
              databases would be cleared.

              If the value provided is different from the one
              authorized in the enum type, then this the operation
              SHALL fail with an error-tag of 'data-missing' and
              an error-app-tag
            'bad-isis-level'.

           "; of 'bad-isis-level'.";
         }
       }
     }

     /* Notifications */
     notification database-overload {
       uses notification-instance-hdr;

       leaf overload {
         type enumeration {
           enum "off" off {
             description
             "The system
               "Indicates IS-IS instance has left overload condition."; state";
           }
           enum "on" on {
             description
             "The system is in
               "Indicates IS-IS instance has entered overload condition."; state";
           }

         }
         description
           "Describes the new "New overload state of the instance."; IS-IS instance";
       }
       description
         "This notification is sent when an IS-IS instance
          overload condition state changes.";
     }

     notification lsp-too-large {
       uses notification-instance-hdr;
       uses notification-interface-hdr;

       leaf pdu-size {
         type uint32;
         description "Size of the LSP PDU";
       }
       leaf lsp-id {
         type lsp-id;
         description "LSP ID."; ID";
       }
       description
         "This notification is sent when we attempt to propagate
          an LSP that is larger than the dataLinkBlockSize for the
          circuit.  The notification generation must be throttled
          with at least a 5 second gap.
         "; seconds betweeen successive
          notifications.";
     }

     notification if-state-change {
       uses notification-instance-hdr;
       uses notification-interface-hdr;

       leaf state {
         type if-state-type;
         description "Interface state.";
       }
       description
         "This notification is sent when an interface
          state change is detected.";
     }

     notification corrupted-lsp-detected {
       uses notification-instance-hdr;
       leaf lsp-id {
         type lsp-id;
         description "LSP ID."; ID";
       }
       description
         "This notification is sent when we find that
          an LSP that was stored in memory has become corrupted.
         ";
          corrupted.";
     }

     notification attempt-to-exceed-max-sequence {
       uses notification-instance-hdr;
       leaf lsp-id {
         type lsp-id;
         description "LSP ID."; ID";
       }
       description
         "This notification is sent when the system
          wraps the 32-bit sequence counter of an LSP.
         "; LSP.";
     }

     notification id-len-mismatch {
       uses notification-instance-hdr;
       uses notification-interface-hdr;

       leaf pdu-field-len {
         type uint8;
         description "Size of the ID length in the received PDU";
       }
       leaf raw-pdu {
         type binary;
         description "Received raw PDU.";
       }
       description
         "This notification is sent when we receive a PDU
          with a different value for the System ID length.
          The notification generation must be throttled
          with at least a 5 second gap.
         "; seconds betweeen successive
          notifications.";

     }

     notification max-area-addresses-mismatch {
       uses notification-instance-hdr;
       uses notification-interface-hdr;

       leaf max-area-addresses {
         type uint8;
         description "Received number of supported areas";
       }
       leaf raw-pdu {
         type binary;
         description "Received raw PDU.";
       }
       description
         "This notification is sent when we receive a PDU
          with a different value for the Maximum Area Addresses.
          The notification generation must be throttled
          with at least a 5 second gap.
         "; seconds betweeen successive
          notifications.";
     }

     notification own-lsp-purge {
       uses notification-instance-hdr;
       uses notification-interface-hdr;
       leaf lsp-id {
         type lsp-id;
         description "LSP ID."; ID";
       }
       description
         "This notification is sent when the system receives
          a PDU with its own system ID and zero age.
         "; age.";
     }

     notification sequence-number-skipped {
       uses notification-instance-hdr;
       uses notification-interface-hdr;
       leaf lsp-id {
         type lsp-id;
         description "LSP ID."; ID";
       }
       description
         "This notification is sent when the system receives a
          PDU with its own system ID and different contents. The
          system has to reissue reoriginate the LSP with a higher sequence number.
         ";
          number.";
     }
     notification authentication-type-failure {
       uses notification-instance-hdr;
       uses notification-interface-hdr;
       leaf raw-pdu {
         type binary;
         description "Received raw PDU.";
       }
       description
         "This notification is sent when the system receives a
          PDU with the wrong authentication type field.
          The notification generation must be throttled
          with at least a 5 second gap.
         "; seconds betweeen successive
          notifications.";
     }

     notification authentication-failure {
       uses notification-instance-hdr;
       uses notification-interface-hdr;
       leaf raw-pdu {
         type binary;
         description "Received raw PDU.";
       }
       description
         "This notification is sent when the system receives
          a PDU with the wrong authentication information.
          The notification generation must be throttled with
          with at least a 5 second gap.
         "; seconds betweeen successive
          notifications.";
     }

     notification version-skew {
       uses notification-instance-hdr;
       uses notification-interface-hdr;
       leaf protocol-version {
         type uint8;
         description "Protocol version received in the PDU.";
       }
       leaf raw-pdu {
         type binary;
         description "Received raw PDU.";
       }
       description
         "This notification is sent when the system receives a
          PDU with a different protocol version number.
          The notification generation must be throttled
          with at least
         a 5 second gap.
         "; seconds betweeen successive
          notifications.";
     }
     notification area-mismatch {
       uses notification-instance-hdr;
       uses notification-interface-hdr;
       leaf raw-pdu {
         type binary;
         description "Received raw PDU.";
       }
       description
         "This notification is sent when the system receives a
          Hello PDU from an IS that does not share any area
          address. The notification generation must be throttled
          with at least
         a 5 second gap.
         "; seconds betweeen successive
          notifications.";
     }

     notification rejected-adjacency {
       uses notification-instance-hdr;
       uses notification-interface-hdr;
       leaf raw-pdu {
         type binary;
         description
           "Received raw PDU.";
       }
       leaf reason {
         type string;
         description
           "The system may provide a reason to reject the
            adjacency. If the reason is not available,
          the system use
            an empty string."; string will be returned.";
       }
       description
         "This notification is sent when the system receives a
          Hello PDU from an IS but does not establish an adjacency
          for some reason. The notification generation must be
          throttled with at least
         a 5 second gap.
         "; seconds betweeen successive
          notifications.";
     }

     notification protocols-supported-mismatch {
       uses notification-instance-hdr;
       uses notification-interface-hdr;
       leaf raw-pdu {
         type binary;
         description "Received raw PDU.";
       }
       leaf-list protocols {
         type uint8;
         description
         "The list
           "List of protocols supported by the remote system.";
       }
       description
         "This notification is sent when the system receives a non pseudonode
          non-pseudonode LSP that has no matching
        protocol protocols
          supported. The notification generation must be throttled
          with at least
         a 5 second gap.
         "; seconds betweeen successive
          notifications.";
     }

     notification lsp-error-detected {
       uses notification-instance-hdr;
       uses notification-interface-hdr;
       leaf lsp-id {
         type lsp-id;
         description "LSP ID.";
       }
       leaf raw-pdu {
         type binary;
         description "Received raw PDU.";
       }
       leaf error-offset {
         type uint32;
         description
           "If the problem is a malformed TLV, the error-offset
            points to the start of the TLV. If the problem is with
            the LSP header, the error-offset points to the suspicious errant
            byte";
       }
       leaf tlv-type {
         type uint8;
         description
         "if
           "If the problem is a malformed TLV, the tlv-type is set
            to the type value of the suspicious TLV.
         Otherwise Otherwise,
            this leaf is not present.";
       }
       description
         "This notification is sent when the system  receives a an
   '      LSP with a parse error. The notification generation must
          be throttled with at least
         a 5 second gap.
         "; seconds betweeen successive
          notifications.";
     }

     notification adjacency-state-change {
       uses notification-instance-hdr;
       uses notification-interface-hdr;
       leaf neighbor {
         type string;
         description
         "Describes the name
           "Name of the neighbor. If the name of the neighbor is
            not available, the
         field would be empty."; it is not returned.";
       }
       leaf neighbor-system-id {
         type system-id;
         description
         "Describes the system-id of the neighbor."; "Neighbor system-id";
       }
       leaf state {
         type adj-state-type;

         description
         "This leaf describes the new "New state of the IS-IS adjacency.";
       }
       leaf reason {
         type string;
         description
           "If the adjacency is going to DOWN,  this leaf provides
            a reason for the adjacency going down. The reason is
            provided as a text. If the adjacency is going to UP, no
            reason is provided.";
       }
       description
         "This notification is sent when an IS-IS adjacency
          moves to Up state or to Down state.";
     }

     notification lsp-received {
       uses notification-instance-hdr;
       uses notification-interface-hdr;

       leaf lsp-id {
         type lsp-id;
         description "LSP ID."; ID";
       }
       leaf sequence {
         type uint32;
         description "Sequence number of the received LSP.";
       }
       leaf received-timestamp {
         type yang:timestamp;

         description
         "This leaf describes the timestamp "Timestamp when the LSP was received. "; received.";
       }
       leaf neighbor-system-id {
         type system-id;
         description
         "Describes the "Neighbor system-id of the neighbor
         that sent the LSP."; LSP sender";
       }
       description
         "This notification is sent when a an LSP is received.
          The notification generation must be throttled with at
          least
         a 5 second gap. "; seconds betweeen successive notifications.";
      }

     notification lsp-generation {
       uses notification-instance-hdr;

       leaf lsp-id {
         type lsp-id;
         description "LSP ID."; ID";
       }
       leaf sequence {
         type uint32;
         description "Sequence number of the received LSP.";
       }
       leaf send-timestamp {
         type yang:timestamp;

         description
         "This leaf describes the timestamp "Timestamp when our LSP was regenerated. "; regenerated.";
       }
       description
         "This notification is sent when a an LSP is regenerated.
          The notification generation must be throttled with at
          least
         a 5 second gap. "; seconds betweeen successive notifications.";
     }
   }
   <CODE ENDS>

7.  Security Considerations

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

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

   Authors recommends to implement NETCONF access control model
   ([RFC6536]) to restrict access to all or part of the configuration to
   specific users.  Access control to RPCs is also critical as RPC
   allows to clear protocol datastructures that would definitively
   impact the network service.  This kind of RPC needs only to be used
   in specific cases by well-known experienced users.

   Authors consider that all the configuration is considered as
   sensitive/vulnerable as well as RPCs.  But security teams can decide
   to open some part of the configuration to less experienced users
   depending on the internal organization, for example:

   o  User FullWrite: would access to the whole data model.  This kind
      of profile may be restricted to few experienced people.

   o  User PartialWrite: would only access to configuration part within
      /isis/interfaces/interface.  So this kind of profile is restricted
      to creation/modification/deletion of interfaces.  This profile
      does not have access to RPC.

   o  User Read: would only access to the operational states.

   Unauthorized access to configuration or RPC may cause high damages to
   the network service.

   The "isis/database" may contain authentication information.  As
   presented in the description of the "/isis/database/level-
   1/lsp/authentication/authentication-key", the authentication MUST
   never be displayed in a plaintext format for security reason.
   Authors recommend the usage of MD5 to display or return the
   authentication-key.

   Some authentication-key may also be required in the "isis" writable
   container.  When configuring IS-IS using the NETCONF protocol,
   authors recommends the usage of secure transport of NETCONF using SSH
   ([RFC6242]).

8.  Contributors

   Authors would like to thank Kiran Agrahara Sreenivasa, Dean
   Bogdanovic, Yingzhen Qu, Yi Yang for their major contributions to the
   draft.

9.  Acknowledgements

   TBD.

10.  IANA Considerations

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

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

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

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

11.  Change log for ietf-isis YANG module

11.1.  From version -19 to version -20

   o  Moved to Yang 1.1

   o  Lower case enumerations

   o  Add RFC references to features

   o  Remove segment-routing feature

   o  Modified BFD activation modeling

11.2.  From version -18 to version -19

   o  Align with draft-ietf-netmod-rfc8022bis.

   o  Modify address family types as per draft-ietf-rtgwg-routing-types-
      17.

11.3.  From version -17 to version -18

   o  NMDA compliancy.

   o  Set some default values.

   o  Align with iana-rt-types module.

11.4.  From version -16 to version -17

   o  Cosmetic fixes.

   o  Use of rt-types model.

11.5.  From version -15 to version -16

   o  Alignment with last IETF key chain model.

   o  lsp-log "change" leaf moved as an identity.

   o  Incremental SPF removed from spf-log types.

11.6.  From version -14 to version -15

   o  Alignment with OSPF model done:

      *  Added spf-control container with IETF SPF delay algorithm as a
         feature.

      *  Added graceful-restart options.

      *  Added nsr as a feature.

      *  Removed per topology FRR.  Need to be augmented if necessary.

      *  Created an ldp container within mpls.

      *  Renamed igp-ldp-sync to igp-sync.

      *  Added auto-cost container.

      *  Moved reference-bandwidth under auto-cost container.

      *  Added IS-IS local RIB as operational state.

      *  Added decode-completed and raw-data leaves in the LSDB model.

      *  Modified the notification header.

11.7.  From version -13 to version -14

   o  Segment Routing extensions are now in a separate document.

11.8.  From version -12 to version -13

   o  Move feature nlpid-control to container rather than list.

   o  Rename multi-topology to topologies to align with OSPF.

   o  Rename bfd/enabled to bfd/enable for consistency reason.

   o  Add support for NSR with a feature.

11.9.  From version -09 to version -12

   o  Rename node-tag container to node-tags.

11.10.  From version -08 to version -09

   o  Added container before af list.

   o  Added container before topology list.

   o  Aligned LFA if per level cfg.

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

11.11.  From version -07 to version -08

   o  Remove selector from system-id type.

   o  Add some default values.

   o  Moved lists to containers+groupings for per level configuration.

   o  remove routing-instance as per core routing model v21.

   o  added BFD leaf (no more BFD protocol model).

   o  changed keychain module reference.

11.12.  From version -05 to version -07

   o  Move Overload config from list to container.

   o  Move Overload-max-metric config from list to container.

   o  Move preference config from list to container.

   o  Add Node flag in config.

   o  Removed BFD config => moved to isis-bfd module.

   o  Remove call to routing policy model.

11.13.  From version -03 to version -05

   o  Correct invalid references to previous versions of core routing
      model.

   o  Remove BFD config and replace by groupings from ietf-bfd.

   o  Adding routing-policy support through routing-policy model.

11.14.  From version -02 to version -03

   o  Reviewed config and op state groupings.

   o  Add default value to lfa candidate-disabled.

   o  Add enable leaf to isis container to reflect admin state.

   o  Move to VRF centric only.

   o  Segment routing is part os a separate module.

11.15.  From version -01 to version -02

   o  Adding IPFRR.

   o  Adding igp-ldp-sync.

   o  Adding segment-routing.

   o  Adding instance reference to operational states.

   o  Move AF type from string to identity.

   o  Updated router-capability in LSDB description.

   o  packet counters moved to interface-packet-counters.

   o  Added modification information in lsp-log.

   o  Removing igp-ldp-sync timer in IS-IS.

   o  Defining hierarchy for operational states.

   o  Adding clns-mtu.

   o  Adding key-chain.

11.16.  From version -00 to version -01

   o  Interface metric move from af container to interface container.

   o  Hello-padding on interface moved to hello-padding-disable with
      empty type.

   o  three-way-handshake removed.

   o  route preference changed to a choice.

   o  csnp-authentication/psnp-authentication merged to authentication
      container.

   o  lsp-gen-interval-exp-delay removed.

   o  Added overload-max-metric feature.

   o  overload-max-metric is in a separate container.

   o  Change hello-padding to container.

   o  Change bfd to container.

   o  Make BFD a feature.

   o  Create mpls-te container and put router-id inside.

   o  Remove GR helper disable and timers.

12.  Normative References

   [I-D.ietf-netmod-routing-cfg]
              Lhotka, L. and A. Lindem, "A YANG Data Model for Routing
              Management", draft-ietf-netmod-routing-cfg-25 (work in
              progress), November 2016.

   [I-D.ietf-rtgwg-yang-key-chain]
              Lindem, A., Qu, Y., Yeung, D., Chen, I., and Z. Zhang,
              "Routing Key Chain YANG Data Model", draft-ietf-rtgwg-
              yang-key-chain-24 (work in progress), April 2017.

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

   [RFC5120]  Przygienda, T., Shen, N., and N. Sheth, "M-ISIS: Multi
              Topology (MT) Routing in Intermediate System to
              Intermediate Systems (IS-ISs)", RFC 5120,
              DOI 10.17487/
              RFC5120, 10.17487/RFC5120, February 2008, <https://www.rfc-editor.org/info/
              rfc5120>. <https://www.rfc-
              editor.org/info/rfc5120>.

   [RFC5286]  Atlas, A., Ed. and A. Zinin, Ed., "Basic Specification for
              IP Fast Reroute: Loop-Free Alternates", RFC 5286,
              DOI 10.17487/RFC5286, September 2008, <https://www.rfc-
              editor.org/info/rfc5286>.

   [RFC5443]  Jork, M., Atlas, A., and L. Fang, "LDP IGP
              Synchronization", RFC 5443, DOI 10.17487/RFC5443, March
              2009, <https://www.rfc-editor.org/info/rfc5443>.

   [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>.

   [RFC7490]  Bryant, S., Filsfils, C., Previdi, S., Shand, M., and N.
              So, "Remote Loop-Free Alternate (LFA) Fast Reroute (FRR)",
              RFC 7490, DOI 10.17487/RFC7490, April 2015,
              <https://www.rfc-editor.org/info/rfc7490>.

Appendix A.  Example of IS-IS configuration in XML

   This section gives an example of configuration of an IS-IS instance
   on a device.  The example is written in XML.

   <?xml version="1.0" encoding="utf-8"?>
   <data xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
     <routing xmlns="urn:ietf:params:xml:ns:yang:ietf-routing">
         <name>SLI</name>
         <router-id>1.1.1.1</router-id>
         <description/>
         <interfaces>
           <interface>
             <name>Loopback0</name>
           </interface>
                   <interface>
             <name>Eth1</name>
           </interface>
         </interfaces>
         <control-plane-protocols>
           <control-plane-protocol>
             <name>ISIS</name>
             <description/>
             <type>isis:isis</type>
             <isis xmlns="urn:ietf:params:xml:ns:yang:ietf-isis">
                             <enable>true</enable>
                             <level-type>level-2</level-type>
                 <system-id>87FC.FCDF.4432</system-id>
                 <area-address>49.0001</area-address>
                 <mpls-te>
                   <ipv4-router-id>1.1.1.1</ipv4-router-id>
                 </mpls-te>
                 <lsp-lifetime>65535</lsp-lifetime>
                 <lsp-refresh>65000</lsp-refresh>
                 <metric-type>
                   <value>wide</value>
                 </metric-type>
                 <default-metric>
                   <value>111111</value>
                 </default-metric>
                 <afs>
                                   <af>
                                           <af>ipv4-unicast</af>
                                           <enabled>true</enabled>
                                   </af>
                 </afs>
                 <interfaces>
                   <interface>
                     <name>Loopback0</name>
                     <tag>200</tag>
                     <metric>
                       <value>0</value>
                     </metric>
                                     <passive>true</passive>
                   </interface>
                                   <interface>
                     <name>Eth1</name>
                                     <level-type>level-2</level-type>
                     <interface-type>point-to-point</interface-type>
                                     <interface-type>point-to-point
                                     </interface-type>
                     <metric>
                       <value>167890</value>
                     </metric>

                   </interface>
                 </interfaces>
             </isis>
           </control-plane-protocol>
         </control-plane-protocols>
     </routing>
     <interfaces xmlns="urn:ietf:params:xml:ns:yang:ietf-interfaces">
       <interface>
         <name>Loopback0</name>
         <description/>
         <type/>
         <link-up-down-trap-enable/>
         <ipv4 xmlns="urn:ietf:params:xml:ns:yang:ietf-ip">
           <mtu/>
           <address>
             <ip>1.1.1.1</ip>
             <prefix-length>32</prefix-length>
           </address>
         </ipv4>

       </interface>
           <interface>
         <name>Eth1</name>
         <description/>
         <type/>
         <link-up-down-trap-enable/>
         <ipv4 xmlns="urn:ietf:params:xml:ns:yang:ietf-ip">
           <mtu/>
           <address>
             <ip>10.0.0.1</ip>
             <prefix-length>30</prefix-length>
           </address>
         </ipv4>

       </interface>
     </interfaces>
   </data>

Authors' Addresses

   Stephane Litkowski
   Orange

   Email: stephane.litkowski@orange.com
   Derek Yeung
   Arrcus, Inc

   Email: derek@arrcus.com

   Acee Lindem
   Cisco Systems

   Email: acee@cisco.com

   Jeffrey Zhang
   Juniper Networks

   Email: zzhang@juniper.net

   Ladislav Lhotka
   CZ.NIC

   Email: lhotka@nic.cz