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NETCONF Working Group                                          K. Watsen
Internet-Draft                                           Watsen Networks
Intended status: Standards Track                             8 July 2020
Expires: 9 January 2021


                    NETCONF Client and Server Models
              draft-ietf-netconf-netconf-client-server-20

Abstract

   This document defines two YANG modules, one module to configure a
   NETCONF client and the other module to configure a NETCONF server.
   Both modules support both the SSH and TLS transport protocols, and
   support both standard NETCONF and NETCONF Call Home connections.

Editorial Note (To be removed by RFC Editor)

   This draft contains placeholder values that need to be replaced with
   finalized values at the time of publication.  This note summarizes
   all of the substitutions that are needed.  No other RFC Editor
   instructions are specified elsewhere in this document.

   Artwork in this document contains shorthand references to drafts in
   progress.  Please apply the following replacements (note: not all may
   be present):

   *  "AAAA" --> the assigned RFC value for draft-ietf-netconf-crypto-
      types

   *  "BBBB" --> the assigned RFC value for draft-ietf-netconf-trust-
      anchors

   *  "CCCC" --> the assigned RFC value for draft-ietf-netconf-keystore

   *  "DDDD" --> the assigned RFC value for draft-ietf-netconf-tcp-
      client-server

   *  "EEEE" --> the assigned RFC value for draft-ietf-netconf-ssh-
      client-server

   *  "FFFF" --> the assigned RFC value for draft-ietf-netconf-tls-
      client-server

   *  "GGGG" --> the assigned RFC value for draft-ietf-netconf-http-
      client-server

   *  "HHHH" --> the assigned RFC value for this draft



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   Artwork in this document contains placeholder values for the date of
   publication of this draft.  Please apply the following replacement:

   *  "2020-07-08" --> the publication date of this draft

   The following Appendix section is to be removed prior to publication:

   *  Appendix A.  Change Log

Status of This Memo

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

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at https://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on 9 January 2021.

Copyright Notice

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

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

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
     1.1.  Relation to other RFCs  . . . . . . . . . . . . . . . . .   4
     1.2.  Specification Language  . . . . . . . . . . . . . . . . .   5
     1.3.  Adherence to the NMDA . . . . . . . . . . . . . . . . . .   5
   2.  The "ietf-netconf-client" Module  . . . . . . . . . . . . . .   5
     2.1.  Data Model Overview . . . . . . . . . . . . . . . . . . .   6



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     2.2.  Example Usage . . . . . . . . . . . . . . . . . . . . . .  10
     2.3.  YANG Module . . . . . . . . . . . . . . . . . . . . . . .  14
   3.  The "ietf-netconf-server" Module  . . . . . . . . . . . . . .  25
     3.1.  Data Model Overview . . . . . . . . . . . . . . . . . . .  25
     3.2.  Example Usage . . . . . . . . . . . . . . . . . . . . . .  30
     3.3.  YANG Module . . . . . . . . . . . . . . . . . . . . . . .  36
   4.  Security Considerations . . . . . . . . . . . . . . . . . . .  49
     4.1.  The "ietf-netconf-client" YANG Module . . . . . . . . . .  49
     4.2.  The "ietf-netconf-server" YANG Module . . . . . . . . . .  49
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  50
     5.1.  The IETF XML Registry . . . . . . . . . . . . . . . . . .  50
     5.2.  The YANG Module Names Registry  . . . . . . . . . . . . .  50
   6.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  50
     6.1.  Normative References  . . . . . . . . . . . . . . . . . .  50
     6.2.  Informative References  . . . . . . . . . . . . . . . . .  52
   Appendix A.  Change Log . . . . . . . . . . . . . . . . . . . . .  53
     A.1.  00 to 01  . . . . . . . . . . . . . . . . . . . . . . . .  53
     A.2.  01 to 02  . . . . . . . . . . . . . . . . . . . . . . . .  53
     A.3.  02 to 03  . . . . . . . . . . . . . . . . . . . . . . . .  54
     A.4.  03 to 04  . . . . . . . . . . . . . . . . . . . . . . . .  54
     A.5.  04 to 05  . . . . . . . . . . . . . . . . . . . . . . . .  54
     A.6.  05 to 06  . . . . . . . . . . . . . . . . . . . . . . . .  54
     A.7.  06 to 07  . . . . . . . . . . . . . . . . . . . . . . . .  54
     A.8.  07 to 08  . . . . . . . . . . . . . . . . . . . . . . . .  55
     A.9.  08 to 09  . . . . . . . . . . . . . . . . . . . . . . . .  55
     A.10. 09 to 10  . . . . . . . . . . . . . . . . . . . . . . . .  55
     A.11. 10 to 11  . . . . . . . . . . . . . . . . . . . . . . . .  55
     A.12. 11 to 12  . . . . . . . . . . . . . . . . . . . . . . . .  55
     A.13. 12 to 13  . . . . . . . . . . . . . . . . . . . . . . . .  56
     A.14. 13 to 14  . . . . . . . . . . . . . . . . . . . . . . . .  56
     A.15. 14 to 15  . . . . . . . . . . . . . . . . . . . . . . . .  56
     A.16. 15 to 16  . . . . . . . . . . . . . . . . . . . . . . . .  56
     A.17. 16 to 17  . . . . . . . . . . . . . . . . . . . . . . . .  56
     A.18. 17 to 18  . . . . . . . . . . . . . . . . . . . . . . . .  57
     A.19. 18 to 19  . . . . . . . . . . . . . . . . . . . . . . . .  57
     A.20. 19 to 20  . . . . . . . . . . . . . . . . . . . . . . . .  57
   Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . . .  57
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .  57

1.  Introduction

   This document defines two YANG [RFC7950] modules, one module to
   configure a NETCONF [RFC6241] client and the other module to
   configure a NETCONF server.  Both modules support both NETCONF over
   SSH [RFC6242] and NETCONF over TLS [RFC7589] and NETCONF Call Home
   connections [RFC8071].





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1.1.  Relation to other RFCs

   This document presents one or more YANG modules [RFC7950] that are
   part of a collection of RFCs that work together to define
   configuration modules for clients and servers of both the NETCONF
   [RFC6241] and RESTCONF [RFC8040] protocols.

   The modules have been defined in a modular fashion to enable their
   use by other efforts, some of which are known to be in progress at
   the time of this writing, with many more expected to be defined in
   time.

   The relationship between the various RFCs in the collection is
   presented in the below diagram.  The labels in the diagram represent
   the primary purpose provided by each RFC.  Links the each RFC are
   provided below the diagram.

                                  crypto-types
                                    ^      ^
                                   /        \
                                  /          \
                         truststore         keystore
                          ^     ^             ^  ^
                          |     +---------+   |  |
                          |               |   |  |
                          |      +------------+  |
   tcp-client-server      |     /         |      |
      ^    ^        ssh-client-server     |      |
      |    |           ^            tls-client-server
      |    |           |              ^     ^        http-client-server
      |    |           |              |     |                 ^
      |    |           |        +-----+     +---------+       |
      |    |           |        |                     |       |
      |    +-----------|--------|--------------+      |       |
      |                |        |              |      |       |
      +-----------+    |        |              |      |       |
                  |    |        |              |      |       |
                  |    |        |              |      |       |
               netconf-client-server       restconf-client-server












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   +=======================+===========================================+
   | Label in Diagram      | Originating RFC                           |
   +=======================+===========================================+
   | crypto-types          | [I-D.ietf-netconf-crypto-types]           |
   +-----------------------+-------------------------------------------+
   | truststore            | [I-D.ietf-netconf-trust-anchors]          |
   +-----------------------+-------------------------------------------+
   | keystore              | [I-D.ietf-netconf-keystore]               |
   +-----------------------+-------------------------------------------+
   | tcp-client-server     | [I-D.ietf-netconf-tcp-client-server]      |
   +-----------------------+-------------------------------------------+
   | ssh-client-server     | [I-D.ietf-netconf-ssh-client-server]      |
   +-----------------------+-------------------------------------------+
   | tls-client-server     | [I-D.ietf-netconf-tls-client-server]      |
   +-----------------------+-------------------------------------------+
   | http-client-server    | [I-D.ietf-netconf-http-client-server]     |
   +-----------------------+-------------------------------------------+
   | netconf-client-server | [I-D.ietf-netconf-netconf-client-server]  |
   +-----------------------+-------------------------------------------+
   |restconf-client-server | [I-D.ietf-netconf-restconf-client-server] |
   +-----------------------+-------------------------------------------+

                       Table 1: Label to RFC Mapping

1.2.  Specification Language

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
   "OPTIONAL" in this document are to be interpreted as described in BCP
   14 [RFC2119] [RFC8174] when, and only when, they appear in all
   capitals, as shown here.

1.3.  Adherence to the NMDA

   This document in compliant with the Network Management Datastore
   Architecture (NMDA) [RFC8342].  For instance, as described in
   [I-D.ietf-netconf-trust-anchors] and [I-D.ietf-netconf-keystore],
   trust anchors and keys installed during manufacturing are expected to
   appear in <operational>.

2.  The "ietf-netconf-client" Module

   The NETCONF client model presented in this section supports both
   clients initiating connections to servers, as well as clients
   listening for connections from servers calling home, using either the
   SSH and TLS transport protocols.





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   YANG feature statements are used to enable implementations to
   advertise which potentially uncommon parts of the model the NETCONF
   client supports.

2.1.  Data Model Overview

2.1.1.  Features

   The following diagram lists all the "feature" statements defined in
   the "ietf-netconf-client" module:

   Features:
     +-- ssh-initiate
     +-- tls-initiate
     +-- ssh-listen
     +-- tls-listen

2.1.2.  Groupings

   The following diagram lists all the "grouping" statements defined in
   the "ietf-netconf-client" module:

   Groupings:
     +-- netconf-client-grouping
     +-- netconf-client-initiate-stack-grouping
     +-- netconf-client-listen-stack-grouping
     +-- netconf-client-app-grouping

   Each of these groupings are presented in the following subsections.

2.1.2.1.  The "netconf-client-grouping" Grouping

   The following tree diagram [RFC8340] illustrates the "netconf-client-
   grouping" grouping:

     grouping netconf-client-grouping ---> <empty>

   Comments:

   *  This grouping does not define any nodes, but is maintained so that
      downstream modules can augment nodes into it if needed.

   *  The "netconf-client-grouping" defines, if it can be called that,
      the configuration for just "NETCONF" part of a protocol stack.  It
      does not, for instance, define any configuration for the "TCP",
      "SSH" or "TLS" protocol layers (for that, see Section 2.1.2.2 and
      Section 2.1.2.3).




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2.1.2.2.  The "netconf-client-initiate-stack-grouping" Grouping

   The following tree diagram [RFC8340] illustrates the "netconf-client-
   initiate-stack-grouping" grouping:

     grouping netconf-client-initiate-stack-grouping
       +-- (transport)
          +--:(ssh) {ssh-initiate}?
          |  +-- ssh
          |     +-- tcp-client-parameters
          |     |  +---u tcpc:tcp-client-grouping
          |     +-- ssh-client-parameters
          |     |  +---u sshc:ssh-client-grouping
          |     +-- netconf-client-parameters
          |        +--u ncc:netconf-client-grouping
          +--:(tls) {tls-initiate}?
             +-- tls
                +-- tcp-client-parameters
                |  +---u tcpc:tcp-client-grouping
                +-- tls-client-parameters
                |  +---u tlsc:tls-client-grouping
                +-- netconf-client-parameters
                   +---u ncc:netconf-client-grouping

   Comments:

   *  The "netconf-client-initiate-stack-grouping" defines the
      configuration for a full NETCONF protocol stack, for NETCONF
      clients that initiate connections to NETCONF servers, as opposed
      to receiving call-home [RFC8071] connections.

   *  The "transport" choice node enables both the SSH and TLS
      transports to be configured, with each option enabled by a
      "feature" statement.

   *  For the referenced grouping statement(s):

      -  The "tcp-client-grouping" grouping is discussed in
         Section 3.1.2.1 of [I-D.ietf-netconf-tcp-client-server].
      -  The "ssh-client-grouping" grouping is discussed in
         Section 3.1.2.1 of [I-D.ietf-netconf-ssh-client-server].
      -  The "tls-client-grouping" grouping is discussed in
         Section 3.1.2.1 of [I-D.ietf-netconf-tls-client-server].
      -  The "netconf-client-grouping" grouping is discussed in
         Section 2.1.2.1 in this document.






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2.1.2.3.  The "netconf-client-listen-stack-grouping" Grouping

   The following tree diagram [RFC8340] illustrates the "netconf-client-
   listen-stack-grouping" grouping:

     grouping netconf-client-listen-stack-grouping
       +-- (transport)
          +--:(ssh) {ssh-listen}?
          |  +-- ssh
          |     +-- tcp-server-parameters
          |     |  +---u tcps:tcp-server-grouping
          |     +-- ssh-client-parameters
          |     |  +---u sshc:ssh-client-grouping
          |     +-- netconf-client-parameters
          |        +--u ncc:netconf-client-grouping
          +--:(tls) {tls-listen}?
             +-- tls
                +-- tcp-server-parameters
                |  +---u tcps:tcp-server-grouping
                +-- tls-client-parameters
                |  +---u tlsc:tls-client-grouping
                +-- netconf-client-parameters
                   +---u ncc:netconf-client-grouping

   Comments:

   *  The "netconf-client-listen-stack-grouping" defines the
      configuration for a full NETCONF protocol stack, for NETCONF
      clients that receive call-home [RFC8071] connections from NETCONF
      servers.

   *  The "transport" choice node enables both the SSH and TLS
      transports to be configured, with each option enabled by a
      "feature" statement.

   *  For the referenced grouping statement(s):

      -  The "tcp-server-grouping" grouping is discussed in
         Section 4.1.2.1 of [I-D.ietf-netconf-tcp-client-server].
      -  The "ssh-client-grouping" grouping is discussed in
         Section 3.1.2.1 of [I-D.ietf-netconf-ssh-client-server].
      -  The "tls-client-grouping" grouping is discussed in
         Section 3.1.2.1 of [I-D.ietf-netconf-tls-client-server].
      -  The "netconf-client-grouping" grouping is discussed in
         Section 2.1.2.1 in this document.






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2.1.2.4.  The "netconf-client-app-grouping" Grouping

   The following tree diagram [RFC8340] illustrates the "netconf-client-
   app-grouping" grouping:

     grouping netconf-client-app-grouping
       +-- initiate! {ssh-initiate or tls-initiate}?
       |  +-- netconf-server* [name]
       |     +-- name?                 string
       |     +-- endpoints
       |     |  +-- endpoint* [name]
       |     |     +-- name?                                     string
       |     |     +---u netconf-client-initiate-stack-grouping
       |     +-- connection-type
       |     |  +-- (connection-type)
       |     |     +--:(persistent-connection)
       |     |     |  +-- persistent!
       |     |     +--:(periodic-connection)
       |     |        +-- periodic!
       |     |           +-- period?         uint16
       |     |           +-- anchor-time?    yang:date-and-time
       |     |           +-- idle-timeout?   uint16
       |     +-- reconnect-strategy
       |        +-- start-with?     enumeration
       |        +-- max-attempts?   uint8
       +-- listen! {ssh-listen or tls-listen}?
          +-- idle-timeout?   uint16
          +-- endpoint* [name]
             +-- name?                                   string
             +---u netconf-client-listen-stack-grouping

   Comments:

   *  The "netconf-client-app-grouping" defines the configuration for a
      NETCONF client that supports both initiating connections to
      NETCONF servers as well as receiving call-home connections from
      NETCONF servers.

   *  Both the "initiate" and "listen" subtrees must be enabled by
      "feature" statements.

   *  For the referenced grouping statement(s):

      -  The "netconf-client-initiate-stack-grouping" grouping is
         discussed in Section 2.1.2.2 in this document.
      -  The "netconf-client-listen-stack-grouping" grouping is
         discussed in Section 2.1.2.3 in this document.




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2.1.3.  Protocol-accessible Nodes

   The following diagram lists all the protocol-accessible nodes defined
   in the "ietf-netconf-client" module:

   module: ietf-netconf-client
     +--rw netconf-client
        +---u netconf-client-app-grouping

   Comments:

   *  Protocol-accessible nodes are those nodes that are accessible when
      the module is "implemented", as described in Section 5.6.5 of
      [RFC7950].

   *  For the "ietf-netconf-client" module, the protocol-accessible
      nodes are an instance of the "netconf-client-app-grouping"
      discussed in Section 2.1.2.4 grouping.

   *  The reason for why "netconf-client-app-grouping" exists separate
      from the protocol-accessible nodes definition is so as to enable
      instances of netconf-client-app-grouping to be instantiated in
      other locations, as may be needed or desired by some modules.

2.2.  Example Usage

   The following example illustrates configuring a NETCONF client to
   initiate connections, using both the SSH and TLS transport protocols,
   as well as to listen for call-home connections, again using both the
   SSH and TLS transport protocols.

   This example is consistent with the examples presented in Section 2.2
   of [I-D.ietf-netconf-trust-anchors] and Section 2.2 of
   [I-D.ietf-netconf-keystore].

   =============== NOTE: '\' line wrapping per RFC 8792 ================

   <netconf-client
     xmlns="urn:ietf:params:xml:ns:yang:ietf-netconf-client"
     xmlns:ct="urn:ietf:params:xml:ns:yang:ietf-crypto-types">

     <!-- NETCONF servers to initiate connections to -->
     <initiate>
       <netconf-server>
         <name>corp-fw1</name>
         <endpoints>
           <endpoint>
             <name>corp-fw1.example.com</name>



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             <ssh>
               <tcp-client-parameters>
                 <remote-address>corp-fw1.example.com</remote-address>
                 <keepalives>
                   <idle-time>15</idle-time>
                   <max-probes>3</max-probes>
                   <probe-interval>30</probe-interval>
                 </keepalives>
               </tcp-client-parameters>
               <ssh-client-parameters>
                 <client-identity>
                   <username>foobar</username>
                   <public-key>
                     <keystore-reference>ssh-rsa-key</keystore-referenc\
   e>
                   </public-key>
                 </client-identity>
                 <server-authentication>
                   <ca-certs>
                     <truststore-reference>trusted-server-ca-certs</tru\
   ststore-reference>
                   </ca-certs>
                   <ee-certs>
                     <truststore-reference>trusted-server-ee-certs</tru\
   ststore-reference>
                   </ee-certs>
                 </server-authentication>
                 <keepalives>
                   <max-wait>30</max-wait>
                   <max-attempts>3</max-attempts>
                 </keepalives>
               </ssh-client-parameters>
               <netconf-client-parameters>
                 <!-- nothing to configure -->
               </netconf-client-parameters>
             </ssh>
           </endpoint>
           <endpoint>
             <name>corp-fw2.example.com</name>
             <tls>
               <tcp-client-parameters>
                 <remote-address>corp-fw2.example.com</remote-address>
                 <keepalives>
                   <idle-time>15</idle-time>
                   <max-probes>3</max-probes>
                   <probe-interval>30</probe-interval>
                 </keepalives>
               </tcp-client-parameters>



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               <tls-client-parameters>
                 <client-identity>
                   <certificate>
                     <keystore-reference>
                       <asymmetric-key>rsa-asymmetric-key</asymmetric-k\
   ey>
                       <certificate>ex-rsa-cert</certificate>
                     </keystore-reference>
                   </certificate>
                 </client-identity>
                 <server-authentication>
                   <ca-certs>
                     <truststore-reference>trusted-server-ca-certs</tru\
   ststore-reference>
                   </ca-certs>
                   <ee-certs>
                     <truststore-reference>trusted-server-ee-certs</tru\
   ststore-reference>
                   </ee-certs>
                 </server-authentication>
                 <keepalives>
                   <test-peer-aliveness>
                     <max-wait>30</max-wait>
                     <max-attempts>3</max-attempts>
                   </test-peer-aliveness>
                 </keepalives>
               </tls-client-parameters>
               <netconf-client-parameters>
                 <!-- nothing to configure -->
               </netconf-client-parameters>
             </tls>
           </endpoint>
         </endpoints>
         <connection-type>
           <persistent/>
         </connection-type>
         <reconnect-strategy>
           <start-with>last-connected</start-with>
         </reconnect-strategy>
       </netconf-server>
     </initiate>

     <!-- endpoints to listen for NETCONF Call Home connections on -->
     <listen>
       <endpoint>
         <name>Intranet-facing SSH listener</name>
         <ssh>
           <tcp-server-parameters>



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             <local-address>192.0.2.7</local-address>
           </tcp-server-parameters>
           <ssh-client-parameters>
             <client-identity>
               <username>foobar</username>
               <public-key>
                 <keystore-reference>ssh-rsa-key</keystore-reference>
               </public-key>
             </client-identity>
             <server-authentication>
               <ca-certs>
                 <truststore-reference>trusted-server-ca-certs</trustst\
   ore-reference>
               </ca-certs>
               <ee-certs>
                 <truststore-reference>trusted-server-ee-certs</trustst\
   ore-reference>
               </ee-certs>
               <ssh-host-keys>
                 <truststore-reference>trusted-ssh-public-keys</trustst\
   ore-reference>
               </ssh-host-keys>
             </server-authentication>
           </ssh-client-parameters>
           <netconf-client-parameters>
             <!-- nothing to configure -->
           </netconf-client-parameters>
         </ssh>
       </endpoint>
       <endpoint>
         <name>Intranet-facing TLS listener</name>
         <tls>
           <tcp-server-parameters>
             <local-address>192.0.2.7</local-address>
           </tcp-server-parameters>
           <tls-client-parameters>
             <client-identity>
               <certificate>
                 <keystore-reference>
                   <asymmetric-key>rsa-asymmetric-key</asymmetric-key>
                   <certificate>ex-rsa-cert</certificate>
                 </keystore-reference>
               </certificate>
             </client-identity>
             <server-authentication>
               <ca-certs>
                 <truststore-reference>trusted-server-ca-certs</trustst\
   ore-reference>



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               </ca-certs>
               <ee-certs>
                 <truststore-reference>trusted-server-ee-certs</trustst\
   ore-reference>
               </ee-certs>
             </server-authentication>
             <keepalives>
               <peer-allowed-to-send/>
             </keepalives>
           </tls-client-parameters>
           <netconf-client-parameters>
             <!-- nothing to configure -->
           </netconf-client-parameters>
         </tls>
       </endpoint>
     </listen>
   </netconf-client>

2.3.  YANG Module

   This YANG module has normative references to [RFC6242], [RFC6991],
   [RFC7589], [RFC8071], [I-D.ietf-netconf-tcp-client-server],
   [I-D.ietf-netconf-ssh-client-server], and
   [I-D.ietf-netconf-tls-client-server].

   <CODE BEGINS> file "ietf-netconf-client@2020-07-08.yang"

   module ietf-netconf-client {
     yang-version 1.1;
     namespace "urn:ietf:params:xml:ns:yang:ietf-netconf-client";
     prefix ncc;

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

     import ietf-tcp-client {
       prefix tcpc;
       reference
         "RFC DDDD: YANG Groupings for TCP Clients and TCP Servers";
     }

     import ietf-tcp-server {
       prefix tcps;
       reference
         "RFC DDDD: YANG Groupings for TCP Clients and TCP Servers";



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     }

     import ietf-ssh-client {
       prefix sshc;
       revision-date 2020-07-08; // stable grouping definitions
       reference
         "RFC EEEE: YANG Groupings for SSH Clients and SSH Servers";
     }

     import ietf-tls-client {
       prefix tlsc;
       revision-date 2020-07-08; // stable grouping definitions
       reference
         "RFC FFFF: YANG Groupings for TLS Clients and TLS Servers";
     }

     organization
       "IETF NETCONF (Network Configuration) Working Group";

     contact
       "WG Web:   <http://datatracker.ietf.org/wg/netconf/>
        WG List:  <mailto:netconf@ietf.org>
        Author:   Kent Watsen <mailto:kent+ietf@watsen.net>
        Author:   Gary Wu <mailto:garywu@cisco.com>";

     description
       "This module contains a collection of YANG definitions
        for configuring NETCONF clients.

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

        Redistribution and use in source and binary forms, with
        or without modification, is permitted pursuant to, and
        subject to the license terms contained in, the Simplified
        BSD License set forth in Section 4.c of the IETF Trust's
        Legal Provisions Relating to IETF Documents
        (https://trustee.ietf.org/license-info).

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

        The key words 'MUST', 'MUST NOT', 'REQUIRED', 'SHALL',
        'SHALL NOT', 'SHOULD', 'SHOULD NOT', 'RECOMMENDED',
        'NOT RECOMMENDED', 'MAY', and 'OPTIONAL' in this document
        are to be interpreted as described in BCP 14 (RFC 2119)
        (RFC 8174) when, and only when, they appear in all



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        capitals, as shown here.";

     revision 2020-07-08 {
       description
         "Initial version";
       reference
         "RFC HHHH: NETCONF Client and Server Models";
     }

     // Features

     feature ssh-initiate {
       description
         "The 'ssh-initiate' feature indicates that the NETCONF client
          supports initiating SSH connections to NETCONF servers.";
       reference
         "RFC 6242:
            Using the NETCONF Protocol over Secure Shell (SSH)";
     }

     feature tls-initiate {
       description
         "The 'tls-initiate' feature indicates that the NETCONF client
          supports initiating TLS connections to NETCONF servers.";
       reference
         "RFC 7589: Using the NETCONF Protocol over Transport
            Layer Security (TLS) with Mutual X.509 Authentication";
     }

     feature ssh-listen {
       description
         "The 'ssh-listen' feature indicates that the NETCONF client
          supports opening a port to listen for incoming NETCONF
          server call-home SSH connections.";
       reference
         "RFC 8071: NETCONF Call Home and RESTCONF Call Home";
     }

     feature tls-listen {
       description
         "The 'tls-listen' feature indicates that the NETCONF client
          supports opening a port to listen for incoming NETCONF
          server call-home TLS connections.";
       reference
         "RFC 8071: NETCONF Call Home and RESTCONF Call Home";
     }

     // Groupings



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     grouping netconf-client-grouping {
       description
         "A reusable grouping for configuring a NETCONF client
          without any consideration for how underlying transport
          sessions are established.

          This grouping currently doesn't define any nodes.";
     }

     grouping netconf-client-initiate-stack-grouping {
       description
         "A reusable grouping for configuring a NETCONF client
          'initiate' protocol stack for a single connection.";
       choice transport {
         mandatory true;
         description
           "Selects between available transports.";
         case ssh {
           if-feature "ssh-initiate";
           container ssh {
             description
               "Specifies IP and SSH specific configuration
                for the connection.";
             container tcp-client-parameters {
               description
                 "A wrapper around the TCP client parameters
                  to avoid name collisions.";
               uses tcpc:tcp-client-grouping {
                 refine "remote-port" {
                   default "830";
                   description
                     "The NETCONF client will attempt to connect
                      to the IANA-assigned well-known port value
                      for 'netconf-ssh' (830) if no value is
                      specified.";
                 }
               }
             }
             container ssh-client-parameters {
               description
                 "A wrapper around the SSH client parameters to
                  avoid name collisions.";
               uses sshc:ssh-client-grouping;
             }
             container netconf-client-parameters {
               description
                 "A wrapper around the NETCONF client parameters
                  to avoid name collisions.";



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               uses ncc:netconf-client-grouping;
             }
           }
         }
         case tls {
           if-feature "tls-initiate";
           container tls {
             description
               "Specifies IP and TLS specific configuration
                for the connection.";
             container tcp-client-parameters {
               description
                 "A wrapper around the TCP client parameters
                  to avoid name collisions.";
               uses tcpc:tcp-client-grouping {
                 refine "remote-port" {
                   default "6513";
                   description
                     "The NETCONF client will attempt to connect
                      to the IANA-assigned well-known port value
                      for 'netconf-tls' (6513) if no value is
                      specified.";
                 }
               }
             }
             container tls-client-parameters {
               must "client-identity" {
                 description
                   "NETCONF/TLS clients MUST pass some
                    authentication credentials.";
               }
               description
                 "A wrapper around the TLS client parameters
                  to avoid name collisions.";
               uses tlsc:tls-client-grouping;
             }
             container netconf-client-parameters {
               description
                 "A wrapper around the NETCONF client parameters
                  to avoid name collisions.";
               uses ncc:netconf-client-grouping;
             }
           }
         }
       }
     } // netconf-client-initiate-stack-grouping

     grouping netconf-client-listen-stack-grouping {



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       description
         "A reusable grouping for configuring a NETCONF client
          'listen' protocol stack for a single connection.  The
          'listen' stack supports call home connections, as
          described in RFC 8071";
       reference
         "RFC 8071: NETCONF Call Home and RESTCONF Call Home";
       choice transport {
         mandatory true;
         description
           "Selects between available transports.";
         case ssh {
           if-feature "ssh-listen";
           container ssh {
             description
               "SSH-specific listening configuration for inbound
                connections.";
             container tcp-server-parameters {
               description
                 "A wrapper around the TCP server parameters
                  to avoid name collisions.";
               uses tcps:tcp-server-grouping {
                 refine "local-port" {
                   default "4334";
                   description
                     "The NETCONF client will listen on the IANA-
                      assigned well-known port for 'netconf-ch-ssh'
                      (4334) if no value is specified.";
                 }
               }
             }
             container ssh-client-parameters {
               description
                 "A wrapper around the SSH client parameters
                  to avoid name collisions.";
               uses sshc:ssh-client-grouping;
             }
             container netconf-client-parameters {
               description
                 "A wrapper around the NETCONF client parameters
                  to avoid name collisions.";
               uses ncc:netconf-client-grouping;
             }
           }
         }
         case tls {
           if-feature "tls-listen";
           container tls {



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             description
               "TLS-specific listening configuration for inbound
                connections.";
             container tcp-server-parameters {
               description
                 "A wrapper around the TCP server parameters
                  to avoid name collisions.";
               uses tcps:tcp-server-grouping {
                 refine "local-port" {
                   default "4334";
                   description
                     "The NETCONF client will listen on the IANA-
                       assigned well-known port for 'netconf-ch-ssh'
                       (4334) if no value is specified.";
                 }
               }
             }
             container tls-client-parameters {
               must "client-identity" {
                 description
                   "NETCONF/TLS clients MUST pass some
                    authentication credentials.";
               }
               description
                 "A wrapper around the TLS client parameters
                  to avoid name collisions.";
               uses tlsc:tls-client-grouping;
             }
             container netconf-client-parameters {
               description
                 "A wrapper around the NETCONF client parameters
                  to avoid name collisions.";
               uses ncc:netconf-client-grouping;
             }
           }
         }
       }
     } // netconf-client-listen-stack-grouping

     grouping netconf-client-app-grouping {
       description
         "A reusable grouping for configuring a NETCONF client
          application that supports both 'initiate' and 'listen'
          protocol stacks for a multiplicity of connections.";
       container initiate {
         if-feature "ssh-initiate or tls-initiate";
         presence "Enables client to initiate TCP connections";
         description



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           "Configures client initiating underlying TCP connections.";
         list netconf-server {
           key "name";
           min-elements 1;
           description
             "List of NETCONF servers the NETCONF client is to
              maintain simultaneous connections with.";
           leaf name {
             type string;
             description
               "An arbitrary name for the NETCONF server.";
           }
           container endpoints {
             description
               "Container for the list of endpoints.";
             list endpoint {
               key "name";
               min-elements 1;
               ordered-by user;
               description
                 "A user-ordered list of endpoints that the NETCONF
                  client will attempt to connect to in the specified
                  sequence.  Defining more than one enables
                  high-availability.";
               leaf name {
                 type string;
                 description
                   "An arbitrary name for the endpoint.";
               }
               uses netconf-client-initiate-stack-grouping;
             } // list endpoint
           } // container endpoints

           container connection-type {
             description
               "Indicates the NETCONF client's preference for how the
                NETCONF connection is maintained.";
             choice connection-type {
               mandatory true;
               description
                 "Selects between available connection types.";
               case persistent-connection {
                 container persistent {
                   presence "Indicates that a persistent connection is
                             to be maintained.";
                   description
                     "Maintain a persistent connection to the NETCONF
                      server.  If the connection goes down, immediately



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                      start trying to reconnect to the NETCONF server,
                      using the reconnection strategy.

                      This connection type minimizes any NETCONF server
                      to NETCONF client data-transfer delay, albeit at
                      the expense of holding resources longer.";
                 }
               }
               case periodic-connection {
                 container periodic {
                   presence "Indicates that a periodic connection is
                             to be maintained.";
                   description
                     "Periodically connect to the NETCONF server.

                      This connection type increases resource
                      utilization, albeit with increased delay in
                      NETCONF server to NETCONF client interactions.

                      The NETCONF client should close the underlying
                      TCP connection upon completing planned activities.

                      In the case that the previous connection is still
                      active, establishing a new connection is NOT
                      RECOMMENDED.";
                   leaf period {
                     type uint16;
                     units "minutes";
                     default "60";
                     description
                       "Duration of time between periodic connections.";
                   }
                   leaf anchor-time {
                     type yang:date-and-time {
                       // constrained to minute-level granularity
                       pattern '\d{4}-\d{2}-\d{2}T\d{2}:\d{2}'
                             + '(Z|[\+\-]\d{2}:\d{2})';
                     }
                     description
                       "Designates a timestamp before or after which a
                        series of periodic connections are determined.
                        The periodic connections occur at a whole
                        multiple interval from the anchor time.  For
                        example, for an anchor time is 15 minutes past
                        midnight and a period interval of 24 hours, then
                        a periodic connection will occur 15 minutes past
                        midnight everyday.";
                   }



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                   leaf idle-timeout {
                     type uint16;
                     units "seconds";
                     default 120; // two minutes
                     description
                       "Specifies the maximum number of seconds that
                        a NETCONF session may remain idle. A NETCONF
                        session will be dropped if it is idle for an
                        interval longer then this number of seconds.
                        If set to zero, then the NETCONF client will
                        never drop a session because it is idle.";
                   }
                 }
               }
             }
           }
           container reconnect-strategy {
             description
               "The reconnection strategy directs how a NETCONF client
                reconnects to a NETCONF server, after discovering its
                connection to the server has dropped, even if due to a
                reboot.  The NETCONF client starts with the specified
                endpoint and tries to connect to it max-attempts times
                before trying the next endpoint in the list (round
                robin).";
             leaf start-with {
               type enumeration {
                 enum first-listed {
                   description
                     "Indicates that reconnections should start with
                      the first endpoint listed.";
                 }
                 enum last-connected {
                   description
                     "Indicates that reconnections should start with
                      the endpoint last connected to.  If no previous
                      connection has ever been established, then the
                      first endpoint configured is used.   NETCONF
                      clients SHOULD be able to remember the last
                      endpoint connected to across reboots.";
                 }
                 enum random-selection {
                   description
                     "Indicates that reconnections should start with
                      a random endpoint.";
                 }
               }
               default "first-listed";



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               description
                 "Specifies which of the NETCONF server's endpoints
                  the NETCONF client should start with when trying
                  to connect to the NETCONF server.";
             }
             leaf max-attempts {
               type uint8 {
                 range "1..max";
               }
               default "3";
               description
                 "Specifies the number times the NETCONF client tries
                  to connect to a specific endpoint before moving on
                  to the next endpoint in the list (round robin).";
             }
           }
         } // netconf-server
       } // initiate

       container listen {
         if-feature "ssh-listen or tls-listen";
         presence "Enables client to accept call-home connections";
         description
           "Configures the client to accept call-home TCP connections.";
         leaf idle-timeout {
           type uint16;
           units "seconds";
           default "3600"; // one hour
           description
             "Specifies the maximum number of seconds that a NETCONF
              session may remain idle. A NETCONF session will be
              dropped if it is idle for an interval longer than this
              number of seconds.  If set to zero, then the server
              will never drop a session because it is idle.  Sessions
              that have a notification subscription active are never
              dropped.";
         }
         list endpoint {
           key "name";
           min-elements 1;
           description
             "List of endpoints to listen for NETCONF connections.";
           leaf name {
             type string;
             description
               "An arbitrary name for the NETCONF listen endpoint.";
           }
           uses netconf-client-listen-stack-grouping;



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         } // endpoint
       } // listen
     } // netconf-client-app-grouping

     // Protocol accessible node, for servers that implement
     // this module.
     container netconf-client {
       uses netconf-client-app-grouping;
       description
         "Top-level container for NETCONF client configuration.";
     }
   }

   <CODE ENDS>

3.  The "ietf-netconf-server" Module

   The NETCONF server model presented in this section supports both
   listening for connections as well as initiating call-home
   connections, using either the SSH and TLS transport protocols.

   YANG feature statements are used to enable implementations to
   advertise which potentially uncommon parts of the model the NETCONF
   server supports.

3.1.  Data Model Overview

3.1.1.  Features

   The following diagram lists all the "feature" statements defined in
   the "ietf-netconf-server" module:

   Features:
     +-- ssh-listen
     +-- tls-listen
     +-- ssh-call-home
     +-- tls-call-home

3.1.2.  Groupings

   The following diagram lists all the "grouping" statements defined in
   the "ietf-netconf-server" module:

   Groupings:
     +-- netconf-server-grouping
     +-- netconf-server-listen-stack-grouping
     +-- netconf-server-callhome-stack-grouping
     +-- netconf-server-app-grouping



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   Each of these groupings are presented in the following subsections.

3.1.2.1.  The "netconf-server-grouping" Grouping

   The following tree diagram [RFC8340] illustrates the "netconf-server-
   grouping" grouping:

   =============== NOTE: '\' line wrapping per RFC 8792 ================

     grouping netconf-server-grouping
       +-- client-identity-mappings
               {(tls-listen or tls-call-home) and (sshcmn:ssh-x509-cert\
   s)}?
          +---u x509c2n:cert-to-name

   Comments:

   *  The "netconf-server-grouping" defines the configuration for just
      "NETCONF" part of a protocol stack.  It does not, for instance,
      define any configuration for the "TCP", "SSH" or "TLS" protocol
      layers (for that, see Section 3.1.2.2 and Section 3.1.2.3).

   *  The "client-identity-mappings" node, which must be enabled by
      "feature" statements, defines a mapping from certificate fields to
      NETCONF user names.

   *  For the referenced grouping statement(s):

      -  The "cert-to-name" grouping is discussed in Section 4.1 of
         [RFC7407].

3.1.2.2.  The "netconf-server-listen-stack-grouping" Grouping

   The following tree diagram [RFC8340] illustrates the "netconf-server-
   listen-stack-grouping" grouping:
















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     grouping netconf-server-listen-stack-grouping
       +-- (transport)
          +--:(ssh) {ssh-listen}?
          |  +-- ssh
          |     +-- tcp-server-parameters
          |     |  +---u tcps:tcp-server-grouping
          |     +-- ssh-server-parameters
          |     |  +---u sshs:ssh-server-grouping
          |     +-- netconf-server-parameters
          |        +---u ncs:netconf-server-grouping
          +--:(tls) {tls-listen}?
             +-- tls
                +-- tcp-server-parameters
                |  +---u tcps:tcp-server-grouping
                +-- tls-server-parameters
                |  +---u tlss:tls-server-grouping
                +-- netconf-server-parameters
                   +---u ncs:netconf-server-grouping

   Comments:

   *  The "netconf-server-listen-stack-grouping" defines the
      configuration for a full NETCONF protocol stack for NETCONF
      servers that listen for standard connections from NETCONF clients,
      as opposed to initiating call-home [RFC8071] connections.

   *  The "transport" choice node enables both the SSH and TLS
      transports to be configured, with each option enabled by a
      "feature" statement.

   *  For the referenced grouping statement(s):

      -  The "tcp-server-grouping" grouping is discussed in
         Section 4.1.2.1 of [I-D.ietf-netconf-tcp-client-server].
      -  The "ssh-server-grouping" grouping is discussed in
         Section 4.1.2.1 of [I-D.ietf-netconf-ssh-client-server].
      -  The "tls-server-grouping" grouping is discussed in
         Section 4.1.2.1 of [I-D.ietf-netconf-tls-client-server].
      -  The "netconf-server-grouping" is discussed in Section 3.1.2.1
         of this document.

3.1.2.3.  The "netconf-server-callhome-stack-grouping" Grouping

   The following tree diagram [RFC8340] illustrates the "netconf-server-
   callhome-stack-grouping" grouping:






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     grouping netconf-server-callhome-stack-grouping
       +-- (transport)
          +--:(ssh) {ssh-call-home}?
          |  +-- ssh
          |     +-- tcp-client-parameters
          |     |  +---u tcpc:tcp-client-grouping
          |     +-- ssh-server-parameters
          |     |  +---u sshs:ssh-server-grouping
          |     +-- netconf-server-parameters
          |        +---u ncs:netconf-server-grouping
          +--:(tls) {tls-call-home}?
             +-- tls
                +-- tcp-client-parameters
                |  +---u tcpc:tcp-client-grouping
                +-- tls-server-parameters
                |  +---u tlss:tls-server-grouping
                +-- netconf-server-parameters
                   +---u ncs:netconf-server-grouping

   Comments:

   *  The "netconf-server-callhome-stack-grouping" defines the
      configuration for a full NETCONF protocol stack, for NETCONF
      servers that initiate call-home [RFC8071] connections to NETCONF
      clients.

   *  The "transport" choice node enables both the SSH and TLS
      transports to be configured, with each option enabled by a
      "feature" statement.

   *  For the referenced grouping statement(s):

      -  The "tcp-client-grouping" grouping is discussed in
         Section 3.1.2.1 of [I-D.ietf-netconf-tcp-client-server].
      -  The "ssh-server-grouping" grouping is discussed in
         Section 4.1.2.1 of [I-D.ietf-netconf-ssh-client-server].
      -  The "tls-server-grouping" grouping is discussed in
         Section 4.1.2.1 of [I-D.ietf-netconf-tls-client-server].
      -  The "netconf-server-grouping" is discussed in Section 3.1.2.1
         of this document.

3.1.2.4.  The "netconf-server-app-grouping" Grouping

   The following tree diagram [RFC8340] illustrates the "netconf-server-
   app-grouping" grouping:






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     grouping netconf-server-app-grouping
       +-- listen! {ssh-listen or tls-listen}?
       |  +-- idle-timeout?   uint16
       |  +-- endpoint* [name]
       |     +-- name?                                   string
       |     +---u netconf-server-listen-stack-grouping
       +-- call-home! {ssh-call-home or tls-call-home}?
          +-- netconf-client* [name]
             +-- name?                 string
             +-- endpoints
             |  +-- endpoint* [name]
             |     +-- name?                                     string
             |     +---u netconf-server-callhome-stack-grouping
             +-- connection-type
             |  +-- (connection-type)
             |     +--:(persistent-connection)
             |     |  +-- persistent!
             |     +--:(periodic-connection)
             |        +-- periodic!
             |           +-- period?         uint16
             |           +-- anchor-time?    yang:date-and-time
             |           +-- idle-timeout?   uint16
             +-- reconnect-strategy
                +-- start-with?     enumeration
                +-- max-attempts?   uint8

   Comments:

   *  The "netconf-server-app-grouping" defines the configuration for a
      NETCONF server that supports both listening for connections from
      NETCONF clients as well as initiatiating call-home connections to
      NETCONF clients.

   *  Both the "listen" and "call-home" subtrees must be enabled by
      "feature" statements.

   *  For the referenced grouping statement(s):

      -  The "netconf-server-listen-stack-grouping" grouping is
         discussed in Section 3.1.2.2 in this document.
      -  The "netconf-server-callhome-stack-grouping" grouping is
         discussed in Section 3.1.2.3 in this document.

3.1.3.  Protocol-accessible Nodes

   The following diagram lists all the protocol-accessible nodes defined
   in the "ietf-netconf-server" module:




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   module: ietf-netconf-server
     +--rw netconf-server
        +---u netconf-server-app-grouping

   Comments:

   *  Protocol-accessible nodes are those nodes that are accessible when
      the module is "implemented", as described in Section 5.6.5 of
      [RFC7950].

   *  For the "ietf-netconf-server" module, the protocol-accessible
      nodes are an instance of the "netconf-server-app-grouping"
      discussed in Section 3.1.2.4 grouping.

   *  The reason for why "netconf-server-app-grouping" exists separate
      from the protocol-accessible nodes definition is so as to enable
      instances of netconf-server-app-grouping to be instantiated in
      other locations, as may be needed or desired by some modules.

3.2.  Example Usage

   The following example illustrates configuring a NETCONF server to
   listen for NETCONF client connections using both the SSH and TLS
   transport protocols, as well as configuring call-home to two NETCONF
   clients, one using SSH and the other using TLS.

   This example is consistent with the examples presented in Section 2.2
   of [I-D.ietf-netconf-trust-anchors] and Section 2.2 of
   [I-D.ietf-netconf-keystore].

   =============== NOTE: '\' line wrapping per RFC 8792 ================

   <netconf-server
     xmlns="urn:ietf:params:xml:ns:yang:ietf-netconf-server"
     xmlns:ct="urn:ietf:params:xml:ns:yang:ietf-crypto-types"
     xmlns:x509c2n="urn:ietf:params:xml:ns:yang:ietf-x509-cert-to-name">

     <!-- endpoints to listen for NETCONF connections on -->
     <listen>
       <endpoint> <!-- listening for SSH connections -->
         <name>netconf/ssh</name>
         <ssh>
           <tcp-server-parameters>
             <local-address>192.0.2.7</local-address>
           </tcp-server-parameters>
           <ssh-server-parameters>
             <server-identity>
               <host-key>



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                 <name>deployment-specific-certificate</name>
                 <public-key>
                   <keystore-reference>ssh-rsa-key</keystore-reference>
                 </public-key>
               </host-key>
             </server-identity>
             <client-authentication>
               <supported-authentication-methods>
                 <publickey/>
               </supported-authentication-methods>
             </client-authentication>
           </ssh-server-parameters>
           <netconf-server-parameters>
             <!-- nothing to configure -->
           </netconf-server-parameters>
         </ssh>
       </endpoint>
       <endpoint> <!-- listening for TLS sessions -->
         <name>netconf/tls</name>
         <tls>
           <tcp-server-parameters>
             <local-address>192.0.2.7</local-address>
           </tcp-server-parameters>
           <tls-server-parameters>
             <server-identity>
               <certificate>
                 <keystore-reference>
                   <asymmetric-key>rsa-asymmetric-key</asymmetric-key>
                   <certificate>ex-rsa-cert</certificate>
                 </keystore-reference>
               </certificate>
             </server-identity>
             <client-authentication>
               <ca-certs>
                 <truststore-reference>trusted-client-ca-certs</trustst\
   ore-reference>
               </ca-certs>
               <ee-certs>
                 <truststore-reference>trusted-client-ee-certs</trustst\
   ore-reference>
               </ee-certs>
             </client-authentication>
             <keepalives>
               <peer-allowed-to-send/>
             </keepalives>
           </tls-server-parameters>
           <netconf-server-parameters>
             <client-identity-mappings>



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               <cert-to-name>
                 <id>1</id>
                 <fingerprint>11:0A:05:11:00</fingerprint>
                 <map-type>x509c2n:specified</map-type>
                 <name>scooby-doo</name>
               </cert-to-name>
               <cert-to-name>
                 <id>2</id>
                 <map-type>x509c2n:san-any</map-type>
               </cert-to-name>
             </client-identity-mappings>
           </netconf-server-parameters>
         </tls>
       </endpoint>
     </listen>

     <!-- calling home to SSH and TLS based NETCONF clients -->
     <call-home>
       <netconf-client> <!-- SSH-based client -->
         <name>config-mgr</name>
         <endpoints>
           <endpoint>
             <name>east-data-center</name>
             <ssh>
               <tcp-client-parameters>
                 <remote-address>east.config-mgr.example.com</remote-ad\
   dress>
                 <keepalives>
                   <idle-time>15</idle-time>
                   <max-probes>3</max-probes>
                   <probe-interval>30</probe-interval>
                 </keepalives>
               </tcp-client-parameters>
               <ssh-server-parameters>
                 <server-identity>
                   <host-key>
                     <name>deployment-specific-certificate</name>
                     <public-key>
                       <keystore-reference>ssh-rsa-key</keystore-refere\
   nce>
                     </public-key>
                   </host-key>
                 </server-identity>
                 <client-authentication>
                   <supported-authentication-methods>
                     <publickey/>
                   </supported-authentication-methods>
                 </client-authentication>



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               </ssh-server-parameters>
               <netconf-server-parameters>
                 <!-- nothing to configure -->
               </netconf-server-parameters>
             </ssh>
           </endpoint>
           <endpoint>
             <name>west-data-center</name>
             <ssh>
               <tcp-client-parameters>
                 <remote-address>west.config-mgr.example.com</remote-ad\
   dress>
               </tcp-client-parameters>
               <ssh-server-parameters>
                 <server-identity>
                   <host-key>
                     <name>deployment-specific-certificate</name>
                     <public-key>
                       <keystore-reference>ssh-rsa-key</keystore-refere\
   nce>
                     </public-key>
                   </host-key>
                 </server-identity>
                 <client-authentication>
                   <supported-authentication-methods>
                     <publickey/>
                   </supported-authentication-methods>
                 </client-authentication>
               </ssh-server-parameters>
               <netconf-server-parameters>
                 <!-- nothing to configure -->
               </netconf-server-parameters>
             </ssh>
           </endpoint>
         </endpoints>
         <connection-type>
           <periodic>
             <idle-timeout>300</idle-timeout>
             <period>60</period>
           </periodic>
         </connection-type>
         <reconnect-strategy>
           <start-with>last-connected</start-with>
           <max-attempts>3</max-attempts>
         </reconnect-strategy>
       </netconf-client>
       <netconf-client> <!-- TLS-based client -->
         <name>data-collector</name>



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         <endpoints>
           <endpoint>
             <name>east-data-center</name>
             <tls>
               <tcp-client-parameters>
                 <remote-address>east.analytics.example.com</remote-add\
   ress>
                 <keepalives>
                   <idle-time>15</idle-time>
                   <max-probes>3</max-probes>
                   <probe-interval>30</probe-interval>
                 </keepalives>
               </tcp-client-parameters>
               <tls-server-parameters>
                 <server-identity>
                   <certificate>
                     <keystore-reference>
                       <asymmetric-key>rsa-asymmetric-key</asymmetric-k\
   ey>
                       <certificate>ex-rsa-cert</certificate>
                     </keystore-reference>
                   </certificate>
                 </server-identity>
                 <client-authentication>
                   <ca-certs>
                     <truststore-reference>trusted-client-ca-certs</tru\
   ststore-reference>
                   </ca-certs>
                   <ee-certs>
                     <truststore-reference>trusted-client-ee-certs</tru\
   ststore-reference>
                   </ee-certs>
                 </client-authentication>
                 <keepalives>
                   <test-peer-aliveness>
                     <max-wait>30</max-wait>
                     <max-attempts>3</max-attempts>
                   </test-peer-aliveness>
                 </keepalives>
               </tls-server-parameters>
               <netconf-server-parameters>
                 <client-identity-mappings>
                   <cert-to-name>
                     <id>1</id>
                     <fingerprint>11:0A:05:11:00</fingerprint>
                     <map-type>x509c2n:specified</map-type>
                     <name>scooby-doo</name>
                   </cert-to-name>



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                   <cert-to-name>
                     <id>2</id>
                     <map-type>x509c2n:san-any</map-type>
                   </cert-to-name>
                 </client-identity-mappings>
               </netconf-server-parameters>
             </tls>
           </endpoint>
           <endpoint>
             <name>west-data-center</name>
             <tls>
               <tcp-client-parameters>
                 <remote-address>west.analytics.example.com</remote-add\
   ress>
                 <keepalives>
                   <idle-time>15</idle-time>
                   <max-probes>3</max-probes>
                   <probe-interval>30</probe-interval>
                 </keepalives>
               </tcp-client-parameters>
               <tls-server-parameters>
                 <server-identity>
                   <certificate>
                     <keystore-reference>
                       <asymmetric-key>rsa-asymmetric-key</asymmetric-k\
   ey>
                       <certificate>ex-rsa-cert</certificate>
                     </keystore-reference>
                   </certificate>
                 </server-identity>
                 <client-authentication>
                   <ca-certs>
                     <truststore-reference>trusted-client-ca-certs</tru\
   ststore-reference>
                   </ca-certs>
                   <ee-certs>
                     <truststore-reference>trusted-client-ee-certs</tru\
   ststore-reference>
                   </ee-certs>
                 </client-authentication>
                 <keepalives>
                   <test-peer-aliveness>
                     <max-wait>30</max-wait>
                     <max-attempts>3</max-attempts>
                   </test-peer-aliveness>
                 </keepalives>
               </tls-server-parameters>
               <netconf-server-parameters>



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                 <client-identity-mappings>
                   <cert-to-name>
                     <id>1</id>
                     <fingerprint>11:0A:05:11:00</fingerprint>
                     <map-type>x509c2n:specified</map-type>
                     <name>scooby-doo</name>
                   </cert-to-name>
                   <cert-to-name>
                     <id>2</id>
                     <map-type>x509c2n:san-any</map-type>
                   </cert-to-name>
                 </client-identity-mappings>
               </netconf-server-parameters>
             </tls>
           </endpoint>
         </endpoints>
         <connection-type>
           <persistent/>
         </connection-type>
         <reconnect-strategy>
           <start-with>first-listed</start-with>
           <max-attempts>3</max-attempts>
         </reconnect-strategy>
       </netconf-client>
     </call-home>
   </netconf-server>

3.3.  YANG Module

   This YANG module has normative references to [RFC6242], [RFC6991],
   [RFC7407], [RFC7589], [RFC8071],
   [I-D.ietf-netconf-tcp-client-server],
   [I-D.ietf-netconf-ssh-client-server], and
   [I-D.ietf-netconf-tls-client-server].

   <CODE BEGINS> file "ietf-netconf-server@2020-07-08.yang"

   module ietf-netconf-server {
     yang-version 1.1;
     namespace "urn:ietf:params:xml:ns:yang:ietf-netconf-server";
     prefix ncs;

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




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     import ietf-x509-cert-to-name {
       prefix x509c2n;
       reference
         "RFC 7407: A YANG Data Model for SNMP Configuration";
     }

     import ietf-tcp-client {
       prefix tcpc;
       reference
         "RFC DDDD: YANG Groupings for TCP Clients and TCP Servers";
     }

     import ietf-tcp-server {
       prefix tcps;
       reference
         "RFC DDDD: YANG Groupings for TCP Clients and TCP Servers";
     }

     import ietf-ssh-common {
       prefix sshcmn;
       revision-date 2020-07-08; // stable grouping definitions
       reference
         "RFC EEEE: YANG Groupings for SSH Clients and SSH Servers";
     }

     import ietf-ssh-server {
       prefix sshs;
       revision-date 2020-07-08; // stable grouping definitions
       reference
         "RFC EEEE: YANG Groupings for SSH Clients and SSH Servers";
     }

     import ietf-tls-server {
       prefix tlss;
       revision-date 2020-07-08; // stable grouping definitions
       reference
         "RFC FFFF: YANG Groupings for TLS Clients and TLS Servers";
     }

     organization
       "IETF NETCONF (Network Configuration) Working Group";

     contact
       "WG Web:   <http://datatracker.ietf.org/wg/netconf/>
        WG List:  <mailto:netconf@ietf.org>
        Author:   Kent Watsen <mailto:kent+ietf@watsen.net>
        Author:   Gary Wu <mailto:garywu@cisco.com>
        Author:   Juergen Schoenwaelder



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                  <mailto:j.schoenwaelder@jacobs-university.de>";

     description
       "This module contains a collection of YANG definitions
        for configuring NETCONF servers.

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

        Redistribution and use in source and binary forms, with
        or without modification, is permitted pursuant to, and
        subject to the license terms contained in, the Simplified
        BSD License set forth in Section 4.c of the IETF Trust's
        Legal Provisions Relating to IETF Documents
        (https://trustee.ietf.org/license-info).

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

        The key words 'MUST', 'MUST NOT', 'REQUIRED', 'SHALL',
        'SHALL NOT', 'SHOULD', 'SHOULD NOT', 'RECOMMENDED',
        'NOT RECOMMENDED', 'MAY', and 'OPTIONAL' in this document
        are to be interpreted as described in BCP 14 (RFC 2119)
        (RFC 8174) when, and only when, they appear in all
        capitals, as shown here.";

     revision 2020-07-08 {
       description
         "Initial version";
       reference
         "RFC HHHH: NETCONF Client and Server Models";
     }

     // Features

     feature ssh-listen {
       description
         "The 'ssh-listen' feature indicates that the NETCONF server
          supports opening a port to accept NETCONF over SSH
          client connections.";
       reference
         "RFC 6242:
            Using the NETCONF Protocol over Secure Shell (SSH)";
     }

     feature tls-listen {
       description



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         "The 'tls-listen' feature indicates that the NETCONF server
          supports opening a port to accept NETCONF over TLS
          client connections.";
       reference
         "RFC 7589: Using the NETCONF Protocol over Transport
                    Layer Security (TLS) with Mutual X.509
                    Authentication";
     }

     feature ssh-call-home {
       description
         "The 'ssh-call-home' feature indicates that the NETCONF
          server supports initiating a NETCONF over SSH call
          home connection to NETCONF clients.";
       reference
         "RFC 8071: NETCONF Call Home and RESTCONF Call Home";
     }

     feature tls-call-home {
       description
         "The 'tls-call-home' feature indicates that the NETCONF
          server supports initiating a NETCONF over TLS call
          home connection to NETCONF clients.";
       reference
         "RFC 8071: NETCONF Call Home and RESTCONF Call Home";
     }

     // Groupings

     grouping netconf-server-grouping {
       description
         "A reusable grouping for configuring a NETCONF server
          without any consideration for how underlying transport
          sessions are established.

          Note that this grouping uses a fairly typical descendent
          node name such that a stack of 'uses' statements will
          have name conflicts.  It is intended that the consuming
          data model will resolve the issue by wrapping the 'uses'
          statement in a container called, e.g.,
          'netconf-server-parameters'.  This model purposely does
          not do this itself so as to provide maximum flexibility
          to consuming models.";

       container client-identity-mappings {
         if-feature
           "(tls-listen or tls-call-home) and (sshcmn:ssh-x509-certs)";
         description



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           "Specifies mappings through which NETCONF client X.509
            certificates are used to determine a NETCONF username.
            If no matching and valid cert-to-name list entry can be
            found, then the NETCONF server MUST close the connection,
            and MUST NOT accept NETCONF messages over it.";
         reference
           "RFC 7407: A YANG Data Model for SNMP Configuration.";
         uses x509c2n:cert-to-name {
           refine "cert-to-name/fingerprint" {
             mandatory false;
             description
               "A 'fingerprint' value does not need to be specified
                when the 'cert-to-name' mapping is independent of
                fingerprint matching.  A 'cert-to-name' having no
                fingerprint value will match any client certificate
                and therefore should only be present at the end of
                the user-ordered 'cert-to-name' list.";
           }
         }
       }
     }

     grouping netconf-server-listen-stack-grouping {
       description
         "A reusable grouping for configuring a NETCONF server
          'listen' protocol stack for a single connection.";
       choice transport {
         mandatory true;
         description
           "Selects between available transports.";
         case ssh {
           if-feature "ssh-listen";
           container ssh {
             description
               "SSH-specific listening configuration for inbound
                connections.";
             container tcp-server-parameters {
               description
                 "A wrapper around the TCP client parameters
                  to avoid name collisions.";
               uses tcps:tcp-server-grouping {
                 refine "local-port" {
                   default "830";
                   description
                     "The NETCONF server will listen on the
                      IANA-assigned well-known port value
                      for 'netconf-ssh' (830) if no value
                      is specified.";



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                 }
               }
             }
             container ssh-server-parameters {
               description
                 "A wrapper around the SSH server parameters
                  to avoid name collisions.";
               uses sshs:ssh-server-grouping;
             }
             container netconf-server-parameters {
               description
                 "A wrapper around the NETCONF server parameters
                  to avoid name collisions.";
               uses ncs:netconf-server-grouping;
             }
           }
         }
         case tls {
           if-feature "tls-listen";
           container tls {
             description
               "TLS-specific listening configuration for inbound
                connections.";
             container tcp-server-parameters {
               description
                 "A wrapper around the TCP client parameters
                  to avoid name collisions.";
               uses tcps:tcp-server-grouping {
                 refine "local-port" {
                   default "6513";
                   description
                     "The NETCONF server will listen on the
                      IANA-assigned well-known port value
                      for 'netconf-tls' (6513) if no value
                      is specified.";
                 }
               }
             }
             container tls-server-parameters {
               description
                 "A wrapper around the TLS server parameters to
                  avoid name collisions.";
               uses tlss:tls-server-grouping {
                 refine "client-authentication" {
                 must 'ca-certs or ee-certs';
                   description
                     "NETCONF/TLS servers MUST validate client
                      certificates.  This configures certificates



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                      at the socket-level (i.e. bags), more
                      discriminating client-certificate checks
                      SHOULD be implemented by the application.";
                   reference
                     "RFC 7589:
                       Using the NETCONF Protocol over Transport Layer
                       Security (TLS) with Mutual X.509 Authentication";
                 }
               }
             }
             container netconf-server-parameters {
               description
                 "A wrapper around the NETCONF server parameters
                  to avoid name collisions.";
               uses ncs:netconf-server-grouping;
             }
           }
         }
       }
     }

     grouping netconf-server-callhome-stack-grouping {
       description
         "A reusable grouping for configuring a NETCONF server
          'call-home' protocol stack, for a single connection.";
       choice transport {
         mandatory true;
         description
           "Selects between available transports.";
         case ssh {
           if-feature "ssh-call-home";
           container ssh {
             description
               "Specifies SSH-specific call-home transport
                configuration.";
             container tcp-client-parameters {
               description
                 "A wrapper around the TCP client parameters
                  to avoid name collisions.";
               uses tcpc:tcp-client-grouping {
                 refine "remote-port" {
                   default "4334";
                   description
                     "The NETCONF server will attempt to connect
                      to the IANA-assigned well-known port for
                      'netconf-ch-tls' (4334) if no value is
                      specified.";
                 }



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               }
             }
             container ssh-server-parameters {
               description
                 "A wrapper around the SSH server parameters
                  to avoid name collisions.";
               uses sshs:ssh-server-grouping;
             }
             container netconf-server-parameters {
               description
                 "A wrapper around the NETCONF server parameters
                  to avoid name collisions.";
               uses ncs:netconf-server-grouping;
             }
           }
         }
         case tls {
           if-feature "tls-call-home";
           container tls {
             description
               "Specifies TLS-specific call-home transport
                configuration.";
             container tcp-client-parameters {
               description
                 "A wrapper around the TCP client parameters
                  to avoid name collisions.";
               uses tcpc:tcp-client-grouping {
                 refine "remote-port" {
                   default "4335";
                   description
                     "The NETCONF server will attempt to connect
                      to the IANA-assigned well-known port for
                      'netconf-ch-tls' (4335) if no value is
                      specified.";
                 }
               }
             }
             container tls-server-parameters {
               description
                 "A wrapper around the TLS server parameters to
                  avoid name collisions.";
               uses tlss:tls-server-grouping {
                 refine "client-authentication" {
                 must 'ca-certs or ee-certs';
                   description
                     "NETCONF/TLS servers MUST validate client
                      certificates.  This configures certificates
                      at the socket-level (i.e. bags), more



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                      discriminating client-certificate checks
                      SHOULD be implemented by the application.";
                   reference
                     "RFC 7589:
                       Using the NETCONF Protocol over Transport Layer
                       Security (TLS) with Mutual X.509 Authentication";
                 }
               }
             }
             container netconf-server-parameters {
               description
                 "A wrapper around the NETCONF server parameters
                  to avoid name collisions.";
               uses ncs:netconf-server-grouping;
             }
           }
         }
       }
     }

     grouping netconf-server-app-grouping {
       description
         "A reusable grouping for configuring a NETCONF server
          application that supports both 'listen' and 'call-home'
          protocol stacks for a multiplicity of connections.";
       container listen {
         if-feature "ssh-listen or tls-listen";
         presence
           "Enables server to listen for NETCONF client connections.";
         description
           "Configures listen behavior";
         leaf idle-timeout {
           type uint16;
           units "seconds";
           default 3600; // one hour
           description
             "Specifies the maximum number of seconds that a NETCONF
              session may remain idle. A NETCONF session will be
              dropped if it is idle for an interval longer than this
              number of seconds.  If set to zero, then the server
              will never drop a session because it is idle.  Sessions
              that have a notification subscription active are never
              dropped.";
         }
         list endpoint {
           key "name";
           min-elements 1;
           description



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             "List of endpoints to listen for NETCONF connections.";
           leaf name {
             type string;
             description
               "An arbitrary name for the NETCONF listen endpoint.";
           }
           uses netconf-server-listen-stack-grouping;
         }
       }
       container call-home {
         if-feature "ssh-call-home or tls-call-home";
         presence
           "Enables the NETCONF server to initiate the underlying
            transport connection to NETCONF clients.";
         description "Configures call home behavior.";
         list netconf-client {
           key "name";
           min-elements 1;
           description
             "List of NETCONF clients the NETCONF server is to
              maintain simultaneous call-home connections with.";
           leaf name {
             type string;
             description
               "An arbitrary name for the remote NETCONF client.";
           }
           container endpoints {
             description
               "Container for the list of endpoints.";
             list endpoint {
               key "name";
               min-elements 1;
               ordered-by user;
               description
                 "A non-empty user-ordered list of endpoints for this
                  NETCONF server to try to connect to in sequence.
                  Defining more than one enables high-availability.";
               leaf name {
                 type string;
                 description
                   "An arbitrary name for this endpoint.";
               }
               uses netconf-server-callhome-stack-grouping;
             }
           }
           container connection-type {
             description
               "Indicates the NETCONF server's preference for how the



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                NETCONF connection is maintained.";
             choice connection-type {
               mandatory true;
               description
                 "Selects between available connection types.";
               case persistent-connection {
                 container persistent {
                   presence "Indicates that a persistent connection is
                             to be maintained.";
                   description
                     "Maintain a persistent connection to the NETCONF
                      client. If the connection goes down, immediately
                      start trying to reconnect to the NETCONF client,
                      using the reconnection strategy.

                      This connection type minimizes any NETCONF client
                      to NETCONF server data-transfer delay, albeit at
                      the expense of holding resources longer.";
                 }
               }
               case periodic-connection {
                 container periodic {
                   presence "Indicates that a periodic connection is
                             to be maintained.";
                   description
                     "Periodically connect to the NETCONF client.

                      This connection type increases resource
                      utilization, albeit with increased delay in
                      NETCONF client to NETCONF client interactions.

                      The NETCONF client SHOULD gracefully close the
                      connection using <close-session> upon completing
                      planned activities.  If the NETCONF session is
                      not closed gracefully, the NETCONF server MUST
                      immediately attempt to reestablish the connection.

                      In the case that the previous connection is still
                      active (i.e., the NETCONF client has not closed
                      it yet), establishing a new connection is NOT
                      RECOMMENDED.";
                   leaf period {
                     type uint16;
                     units "minutes";
                     default "60";
                     description
                       "Duration of time between periodic connections.";
                   }



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                   leaf anchor-time {
                     type yang:date-and-time {
                       // constrained to minute-level granularity
                       pattern '\d{4}-\d{2}-\d{2}T\d{2}:\d{2}'
                             + '(Z|[\+\-]\d{2}:\d{2})';
                     }
                     description
                       "Designates a timestamp before or after which a
                        series of periodic connections are determined.
                        The periodic connections occur at a whole
                        multiple interval from the anchor time.  For
                        example, for an anchor time is 15 minutes past
                        midnight and a period interval of 24 hours, then
                        a periodic connection will occur 15 minutes past
                        midnight everyday.";
                   }
                   leaf idle-timeout {
                     type uint16;
                     units "seconds";
                     default 120; // two minutes
                     description
                       "Specifies the maximum number of seconds that
                        a NETCONF session may remain idle. A NETCONF
                        session will be dropped if it is idle for an
                        interval longer than this number of seconds.
                        If set to zero, then the server will never
                        drop a session because it is idle.";
                   }
                 }
               } // case periodic-connection
             } // choice connection-type
           } // container connection-type
           container reconnect-strategy {
             description
               "The reconnection strategy directs how a NETCONF server
                reconnects to a NETCONF client, after discovering its
                connection to the client has dropped, even if due to a
                reboot.  The NETCONF server starts with the specified
                endpoint and tries to connect to it max-attempts times
                before trying the next endpoint in the list (round
                robin).";
             leaf start-with {
               type enumeration {
                 enum first-listed {
                   description
                     "Indicates that reconnections should start with
                      the first endpoint listed.";
                 }



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                 enum last-connected {
                   description
                     "Indicates that reconnections should start with
                      the endpoint last connected to.  If no previous
                      connection has ever been established, then the
                      first endpoint configured is used.   NETCONF
                      servers SHOULD be able to remember the last
                      endpoint connected to across reboots.";
                 }
                 enum random-selection {
                   description
                     "Indicates that reconnections should start with
                      a random endpoint.";
                 }
               }
               default "first-listed";
               description
                 "Specifies which of the NETCONF client's endpoints
                  the NETCONF server should start with when trying
                  to connect to the NETCONF client.";
             }
             leaf max-attempts {
               type uint8 {
                 range "1..max";
               }
               default "3";
               description
                 "Specifies the number times the NETCONF server tries
                  to connect to a specific endpoint before moving on
                  to the next endpoint in the list (round robin).";
             }
           } // container reconnect-strategy
         } // list netconf-client
       } // container call-home
     } // grouping netconf-server-app-grouping

     // Protocol accessible node, for servers that implement
     // this module.
     container netconf-server {
       uses netconf-server-app-grouping;
       description
         "Top-level container for NETCONF server configuration.";
     }
   }

   <CODE ENDS>





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4.  Security Considerations

4.1.  The "ietf-netconf-client" YANG Module

   The "ietf-netconf-client" YANG module defines data nodes that are
   designed to be accessed via YANG based management protocols, such as
   NETCONF [RFC6241] and RESTCONF [RFC8040].  Both of these protocols
   have mandatory-to-implement secure transport layers (e.g., SSH, TLS)
   with mutual authentication.

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

   None of the readable data nodes defined in this YANG module are
   considered sensitive or vulnerable in network environments.  The NACM
   "default-deny-all" extension has not been set for any data nodes
   defined in this module.

   None of the writable data nodes defined in this YANG module are
   considered sensitive or vulnerable in network environments.  The NACM
   "default-deny-write" extension has not been set for any data nodes
   defined in this module.

   This module does not define any RPCs, actions, or notifications, and
   thus the security consideration for such is not provided here.

   Please be aware that this module uses groupings defined in other RFCs
   that define data nodes that do set the NACM "default-deny-all" and
   "default-deny-write" extensions.

4.2.  The "ietf-netconf-server" YANG Module

   The "ietf-netconf-server" YANG module defines data nodes that are
   designed to be accessed via YANG based management protocols, such as
   NETCONF [RFC6241] and RESTCONF [RFC8040].  Both of these protocols
   have mandatory-to-implement secure transport layers (e.g., SSH, TLS)
   with mutual authentication.

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

   None of the readable data nodes defined in this YANG module are
   considered sensitive or vulnerable in network environments.  The NACM
   "default-deny-all" extension has not been set for any data nodes
   defined in this module.




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   None of the writable data nodes defined in this YANG module are
   considered sensitive or vulnerable in network environments.  The NACM
   "default-deny-write" extension has not been set for any data nodes
   defined in this module.

   This module does not define any RPCs, actions, or notifications, and
   thus the security consideration for such is not provided here.

   Please be aware that this module uses groupings defined in other RFCs
   that define data nodes that do set the NACM "default-deny-all" and
   "default-deny-write" extensions.

5.  IANA Considerations

5.1.  The IETF XML Registry

   This document registers two URIs in the "ns" subregistry of the IETF
   XML Registry [RFC3688].  Following the format in [RFC3688], the
   following registrations are requested:

      URI: urn:ietf:params:xml:ns:yang:ietf-netconf-client
      Registrant Contact: The NETCONF WG of the IETF.
      XML: N/A, the requested URI is an XML namespace.

      URI: urn:ietf:params:xml:ns:yang:ietf-netconf-server
      Registrant Contact: The NETCONF WG of the IETF.
      XML: N/A, the requested URI is an XML namespace.

5.2.  The YANG Module Names Registry

   This document registers two YANG modules in the YANG Module Names
   registry [RFC6020].  Following the format in [RFC6020], the the
   following registrations are requested:

      name:         ietf-netconf-client
      namespace:    urn:ietf:params:xml:ns:yang:ietf-netconf-client
      prefix:       ncc
      reference:    RFC HHHH

      name:         ietf-netconf-server
      namespace:    urn:ietf:params:xml:ns:yang:ietf-netconf-server
      prefix:       ncs
      reference:    RFC HHHH

6.  References

6.1.  Normative References




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   [I-D.ietf-netconf-keystore]
              Watsen, K., "A YANG Data Model for a Keystore", Work in
              Progress, Internet-Draft, draft-ietf-netconf-keystore-17,
              20 May 2020, <https://tools.ietf.org/html/draft-ietf-
              netconf-keystore-17>.

   [I-D.ietf-netconf-ssh-client-server]
              Watsen, K. and G. Wu, "YANG Groupings for SSH Clients and
              SSH Servers", Work in Progress, Internet-Draft, draft-
              ietf-netconf-ssh-client-server-19, 20 May 2020,
              <https://tools.ietf.org/html/draft-ietf-netconf-ssh-
              client-server-19>.

   [I-D.ietf-netconf-tcp-client-server]
              Watsen, K. and M. Scharf, "YANG Groupings for TCP Clients
              and TCP Servers", Work in Progress, Internet-Draft, draft-
              ietf-netconf-tcp-client-server-06, 16 June 2020,
              <https://tools.ietf.org/html/draft-ietf-netconf-tcp-
              client-server-06>.

   [I-D.ietf-netconf-tls-client-server]
              Watsen, K. and G. Wu, "YANG Groupings for TLS Clients and
              TLS Servers", Work in Progress, Internet-Draft, draft-
              ietf-netconf-tls-client-server-19, 20 May 2020,
              <https://tools.ietf.org/html/draft-ietf-netconf-tls-
              client-server-19>.

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

   [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>.






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

   [RFC7407]  Bjorklund, M. and J. Schoenwaelder, "A YANG Data Model for
              SNMP Configuration", RFC 7407, DOI 10.17487/RFC7407,
              December 2014, <https://www.rfc-editor.org/info/rfc7407>.

   [RFC7589]  Badra, M., Luchuk, A., and J. Schoenwaelder, "Using the
              NETCONF Protocol over Transport Layer Security (TLS) with
              Mutual X.509 Authentication", RFC 7589,
              DOI 10.17487/RFC7589, June 2015,
              <https://www.rfc-editor.org/info/rfc7589>.

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

   [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
              2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
              May 2017, <https://www.rfc-editor.org/info/rfc8174>.

6.2.  Informative References

   [I-D.ietf-netconf-crypto-types]
              Watsen, K., "Common YANG Data Types for Cryptography",
              Work in Progress, Internet-Draft, draft-ietf-netconf-
              crypto-types-15, 20 May 2020,
              <https://tools.ietf.org/html/draft-ietf-netconf-crypto-
              types-15>.

   [I-D.ietf-netconf-http-client-server]
              Watsen, K., "YANG Groupings for HTTP Clients and HTTP
              Servers", Work in Progress, Internet-Draft, draft-ietf-
              netconf-http-client-server-03, 20 May 2020,
              <https://tools.ietf.org/html/draft-ietf-netconf-http-
              client-server-03>.

   [I-D.ietf-netconf-netconf-client-server]
              Watsen, K., "NETCONF Client and Server Models", Work in
              Progress, Internet-Draft, draft-ietf-netconf-netconf-
              client-server-19, 20 May 2020,
              <https://tools.ietf.org/html/draft-ietf-netconf-netconf-
              client-server-19>.

   [I-D.ietf-netconf-restconf-client-server]
              Watsen, K., "RESTCONF Client and Server Models", Work in
              Progress, Internet-Draft, draft-ietf-netconf-restconf-



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              client-server-19, 20 May 2020,
              <https://tools.ietf.org/html/draft-ietf-netconf-restconf-
              client-server-19>.

   [I-D.ietf-netconf-trust-anchors]
              Watsen, K., "A YANG Data Model for a Truststore", Work in
              Progress, Internet-Draft, draft-ietf-netconf-trust-
              anchors-10, 20 May 2020, <https://tools.ietf.org/html/
              draft-ietf-netconf-trust-anchors-10>.

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

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

   [RFC8071]  Watsen, K., "NETCONF Call Home and RESTCONF Call Home",
              RFC 8071, DOI 10.17487/RFC8071, February 2017,
              <https://www.rfc-editor.org/info/rfc8071>.

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

   [RFC8341]  Bierman, A. and M. Bjorklund, "Network Configuration
              Access Control Model", STD 91, RFC 8341,
              DOI 10.17487/RFC8341, March 2018,
              <https://www.rfc-editor.org/info/rfc8341>.

   [RFC8342]  Bjorklund, M., Schoenwaelder, J., Shafer, P., Watsen, K.,
              and R. Wilton, "Network Management Datastore Architecture
              (NMDA)", RFC 8342, DOI 10.17487/RFC8342, March 2018,
              <https://www.rfc-editor.org/info/rfc8342>.

Appendix A.  Change Log

   This section is to be removed before publishing as an RFC.

A.1.  00 to 01

   *  Renamed "keychain" to "keystore".

A.2.  01 to 02

   *  Added to ietf-netconf-client ability to connected to a cluster of
      endpoints, including a reconnection-strategy.



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   *  Added to ietf-netconf-client the ability to configure connection-
      type and also keep-alive strategy.

   *  Updated both modules to accommodate new groupings in the ssh/tls
      drafts.

A.3.  02 to 03

   *  Refined use of tls-client-grouping to add a must statement
      indicating that the TLS client must specify a client-certificate.

   *  Changed 'netconf-client' to be a grouping (not a container).

A.4.  03 to 04

   *  Added RFC 8174 to Requirements Language Section.

   *  Replaced refine statement in ietf-netconf-client to add a
      mandatory true.

   *  Added refine statement in ietf-netconf-server to add a must
      statement.

   *  Now there are containers and groupings, for both the client and
      server models.

A.5.  04 to 05

   *  Now tree diagrams reference ietf-netmod-yang-tree-diagrams

   *  Updated examples to inline key and certificates (no longer a
      leafref to keystore)

A.6.  05 to 06

   *  Fixed change log missing section issue.

   *  Updated examples to match latest updates to the crypto-types,
      trust-anchors, and keystore drafts.

   *  Reduced line length of the YANG modules to fit within 69 columns.

A.7.  06 to 07

   *  Removed "idle-timeout" from "persistent" connection config.

   *  Added "random-selection" for reconnection-strategy's "starts-with"
      enum.



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   *  Replaced "connection-type" choice default (persistent) with
      "mandatory true".

   *  Reduced the periodic-connection's "idle-timeout" from 5 to 2
      minutes.

   *  Replaced reconnect-timeout with period/anchor-time combo.

A.8.  07 to 08

   *  Modified examples to be compatible with new crypto-types algs

A.9.  08 to 09

   *  Corrected use of "mandatory true" for "address" leafs.

   *  Updated examples to reflect update to groupings defined in the
      keystore draft.

   *  Updated to use groupings defined in new TCP and HTTP drafts.

   *  Updated copyright date, boilerplate template, affiliation, and
      folding algorithm.

A.10.  09 to 10

   *  Reformatted YANG modules.

A.11.  10 to 11

   *  Adjusted for the top-level "demux container" added to groupings
      imported from other modules.

   *  Added "must" expressions to ensure that keepalives are not
      configured for "periodic" connections.

   *  Updated the boilerplate text in module-level "description"
      statement to match copyeditor convention.

   *  Moved "expanded" tree diagrams to the Appendix.

A.12.  11 to 12

   *  Removed the "Design Considerations" section.

   *  Removed the 'must' statement limiting keepalives in periodic
      connections.




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   *  Updated models and examples to reflect removal of the "demux"
      containers in the imported models.

   *  Updated the "periodic-connnection" description statements to be
      more like the RESTCONF draft, especially where it described
      dropping the underlying TCP connection.

   *  Updated text to better reference where certain examples come from
      (e.g., which Section in which draft).

   *  In the server model, commented out the "must 'pinned-ca-certs or
      pinned-client-certs'" statement to reflect change made in the TLS
      draft whereby the trust anchors MAY be defined externally.

   *  Replaced the 'listen', 'initiate', and 'call-home' features with
      boolean expressions.

A.13.  12 to 13

   *  Updated to reflect changes in trust-anchors drafts (e.g., s/trust-
      anchors/truststore/g + s/pinned.//)

A.14.  13 to 14

   *  Adjusting from change in TLS client model (removing the top-level
      'certificate' container), by swapping refining-in a 'mandatory
      true' statement with a 'must' statement outside the 'uses'
      statement.

   *  Updated examples to reflect ietf-crypto-types change (e.g.,
      identities --> enumerations)

A.15.  14 to 15

   *  Refactored both the client and server modules similar to how the
      ietf-restconf-server module was refactored in -13 of that draft,
      and the ietf-restconf-client grouping.

A.16.  15 to 16

   *  Added refinement to make "cert-to-name/fingerprint" be mandatory
      false.

   *  Commented out refinement to "tls-server-grouping/client-
      authentication" until a better "must" expression is defined.

A.17.  16 to 17




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   *  Updated examples to include the "*-key-format" nodes.

   *  Updated examples to remove the "required" nodes.

   *  Updated examples to remove the "client-auth-defined-elsewhere"
      nodes.

A.18.  17 to 18

   *  Updated examples to reflect new "bag" addition to truststore.

A.19.  18 to 19

   *  Updated examples to remove the 'algorithm' nodes.

   *  Updated examples to reflect the new TLS keepalives structure.

   *  Added keepalives to the tcp-client-parameters section in the
      netconf-server SSH-based call-home example.

   *  Added a TLS-based call-home example to the netconf-client example.

   *  Added a "Note to Reviewers" note to first page.

A.20.  19 to 20

   *  Expanded "Data Model Overview section(s) [remove "wall" of tree
      diagrams].

   *  Removed expanded tree diagrams that were listed in the Appendix.

   *  Updated the Security Considerations section.

Acknowledgements

   The authors would like to thank for following for lively discussions
   on list and in the halls (ordered by last name): Andy Bierman, Martin
   Bjorklund, Benoit Claise, Ramkumar Dhanapal, Mehmet Ersue, Balazs
   Kovacs, David Lamparter, Ladislav Lhotka, Alan Luchuk, Radek Krejci,
   Tom Petch, Juergen Schoenwaelder, Phil Shafer, Sean Turner, and Bert
   Wijnen.

Author's Address

   Kent Watsen
   Watsen Networks

   Email: kent+ietf@watsen.net



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