RESTCONF Client and Server Models
draft-ietf-netconf-restconf-client-server-20

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

                   RESTCONF Client and Server Models
              draft-ietf-netconf-restconf-client-server-20

Abstract

   This document defines two YANG modules, one module to configure a
   RESTCONF client and the other module to configure a RESTCONF server.
   Both modules support the TLS transport protocol with both standard
   RESTCONF and RESTCONF 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

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

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

   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 B.  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  . . . . . . . . . . . . . . . . . . . . . . . .   4

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     1.1.  Relation to other RFCs  . . . . . . . . . . . . . . . . .   4
     1.2.  Specification Language  . . . . . . . . . . . . . . . . .   5
     1.3.  Adherence to the NMDA . . . . . . . . . . . . . . . . . .   5
   2.  The "ietf-restconf-client" Module . . . . . . . . . . . . . .   5
     2.1.  Data Model Overview . . . . . . . . . . . . . . . . . . .   6
     2.2.  Example Usage . . . . . . . . . . . . . . . . . . . . . .  10
     2.3.  YANG Module . . . . . . . . . . . . . . . . . . . . . . .  14
   3.  The "ietf-restconf-server" Module . . . . . . . . . . . . . .  24
     3.1.  Data Model Overview . . . . . . . . . . . . . . . . . . .  24
     3.2.  Example Usage . . . . . . . . . . . . . . . . . . . . . .  29
     3.3.  YANG Module . . . . . . . . . . . . . . . . . . . . . . .  33
   4.  Security Considerations . . . . . . . . . . . . . . . . . . .  45
     4.1.  The "ietf-restconf-client" YANG Module  . . . . . . . . .  45
     4.2.  The "ietf-restconf-server" YANG Module  . . . . . . . . .  45
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  46
     5.1.  The IETF XML Registry . . . . . . . . . . . . . . . . . .  46
     5.2.  The YANG Module Names Registry  . . . . . . . . . . . . .  46
   6.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  47
     6.1.  Normative References  . . . . . . . . . . . . . . . . . .  47
     6.2.  Informative References  . . . . . . . . . . . . . . . . .  48
   Appendix A.  Expanded Tree Diagrams . . . . . . . . . . . . . . .  49
     A.1.  Expanded Tree Diagram for 'ietf-restconf-client'  . . . .  50
     A.2.  Expanded Tree Diagram for 'ietf-restconf-server'  . . . .  50
   Appendix B.  Change Log . . . . . . . . . . . . . . . . . . . . .  50
     B.1.  00 to 01  . . . . . . . . . . . . . . . . . . . . . . . .  50
     B.2.  01 to 02  . . . . . . . . . . . . . . . . . . . . . . . .  50
     B.3.  02 to 03  . . . . . . . . . . . . . . . . . . . . . . . .  50
     B.4.  03 to 04  . . . . . . . . . . . . . . . . . . . . . . . .  51
     B.5.  04 to 05  . . . . . . . . . . . . . . . . . . . . . . . .  51
     B.6.  05 to 06  . . . . . . . . . . . . . . . . . . . . . . . .  51
     B.7.  06 to 07  . . . . . . . . . . . . . . . . . . . . . . . .  51
     B.8.  07 to 08  . . . . . . . . . . . . . . . . . . . . . . . .  52
     B.9.  08 to 09  . . . . . . . . . . . . . . . . . . . . . . . .  52
     B.10. 09 to 10  . . . . . . . . . . . . . . . . . . . . . . . .  52
     B.11. 10 to 11  . . . . . . . . . . . . . . . . . . . . . . . .  52
     B.12. 11 to 12  . . . . . . . . . . . . . . . . . . . . . . . .  52
     B.13. 12 to 13  . . . . . . . . . . . . . . . . . . . . . . . .  53
     B.14. 13 to 14  . . . . . . . . . . . . . . . . . . . . . . . .  53
     B.15. 14 to 15  . . . . . . . . . . . . . . . . . . . . . . . .  53
     B.16. 15 to 16  . . . . . . . . . . . . . . . . . . . . . . . .  54
     B.17. 16 to 17  . . . . . . . . . . . . . . . . . . . . . . . .  54
     B.18. 17 to 18  . . . . . . . . . . . . . . . . . . . . . . . .  54
     B.19. 18 to 19  . . . . . . . . . . . . . . . . . . . . . . . .  54
     B.20. 19 to 20  . . . . . . . . . . . . . . . . . . . . . . . .  54
   Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . . .  55
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .  55

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1.  Introduction

   This document defines two YANG [RFC7950] modules, one module to
   configure a RESTCONF client and the other module to configure a
   RESTCONF server [RFC8040].  Both modules support the TLS [RFC8446]
   transport protocol with both standard RESTCONF and RESTCONF Call Home
   connections [RFC8071].

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-restconf-client" Module

   The RESTCONF client model presented in this section supports both
   clients initiating connections to servers, as well as clients
   listening for connections from servers calling home.

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

2.1.  Data Model Overview

2.1.1.  Features

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

   Features:
     +-- https-initiate
     +-- http-listen
     +-- https-listen

2.1.2.  Groupings

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

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

   Each of these groupings are presented in the following subsections.

2.1.2.1.  The "restconf-client-grouping" Grouping

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

     grouping restconf-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 "restconf-client-grouping" defines, if it can be called that,
      the configuration for just "RESTCONF" part of a protocol stack.
      It does not, for instance, define any configuration for the "TCP",
      "TLS", or "HTTP" 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 "restconf-client-initiate-stack-grouping" Grouping

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

     grouping restconf-client-initiate-stack-grouping
       +-- (transport)
          +--:(https) {https-initiate}?
             +-- https
                +-- tcp-client-parameters
                |  +---u tcpc:tcp-client-grouping
                +-- tls-client-parameters
                |  +---u tlsc:tls-client-grouping
                +-- http-client-parameters
                |  +---u httpc:http-client-grouping
                +-- restconf-client-parameters
                   +---u rcc:restconf-client-grouping

   Comments:

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

   *  The "transport" choice node enables transport options to be
      configured.  This document only defines an "https" option, but
      other options MAY be augmented in.

   *  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 "tls-client-grouping" grouping is discussed in
         Section 3.1.2.1 of [I-D.ietf-netconf-tls-client-server].
      -  The "http-client-grouping" grouping is discussed in
         Section 2.1.2.2 of [I-D.ietf-netconf-http-client-server].
      -  The "restconf-client-grouping" grouping is discussed in
         Section 2.1.2.1 in this document.

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

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

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     grouping restconf-client-listen-stack-grouping
       +-- (transport)
          +--:(http) {http-listen}?
          |  +-- http
          |     +-- tcp-server-parameters
          |     |  +---u tcps:tcp-server-grouping
          |     +-- http-client-parameters
          |     |  +---u httpc:http-client-grouping
          |     +-- restconf-client-parameters
          |        +---u rcc:restconf-client-grouping
          +--:(https) {https-listen}?
             +-- https
                +-- tcp-server-parameters
                |  +---u tcps:tcp-server-grouping
                +-- tls-client-parameters
                |  +---u tlsc:tls-client-grouping
                +-- http-client-parameters
                |  +---u httpc:http-client-grouping
                +-- restconf-client-parameters
                   +---u rcc:restconf-client-grouping

   Comments:

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

   *  The "transport" choice node enables both the HTTP and HTTPS
      transports to be configured, with each option enabled by a
      "feature" statement.  Note that RESTCONF requires HTTPS, the HTTP
      option is provided to support cases where a TLS-terminator is
      deployed in front of the RESTCONF-client.

   *  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 "tls-client-grouping" grouping is discussed in
         Section 3.1.2.1 of [I-D.ietf-netconf-tls-client-server].
      -  The "http-client-grouping" grouping is discussed in
         Section 2.1.2.2 of [I-D.ietf-netconf-http-client-server].
      -  The "restconf-client-grouping" grouping is discussed in
         Section 2.1.2.1 in this document.

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

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

     grouping restconf-client-app-grouping
       +-- initiate! {https-initiate}?
       |  +-- restconf-server* [name]
       |     +-- name?                 string
       |     +-- endpoints
       |     |  +-- endpoint* [name]
       |     |     +-- name?                                      string
       |     |     +---u restconf-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! {http-listen or https-listen}?
          +-- idle-timeout?   uint16
          +-- endpoint* [name]
             +-- name?                                    string
             +---u restconf-client-listen-stack-grouping

   Comments:

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

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

   *  For the referenced grouping statement(s):

      -  The "restconf-client-initiate-stack-grouping" grouping is
         discussed in Section 2.1.2.2 in this document.
      -  The "restconf-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-restconf-client" module:

   module: ietf-restconf-client
     +--rw restconf-client
        +---u restconf-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-restconf-client" module, the protocol-accessible
      nodes are an instance of the "restconf-client-app-grouping"
      discussed in Section 2.1.2.4 grouping.

   *  The reason for why "restconf-client-app-grouping" exists separate
      from the protocol-accessible nodes definition is so as to enable
      instances of restconf-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 RESTCONF client to
   initiate connections, as well as to listen for call-home connections.

   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 ================

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

     <!-- RESTCONF servers to initiate connections to -->
     <initiate>
       <restconf-server>
         <name>corp-fw1</name>
         <endpoints>
           <endpoint>
             <name>corp-fw1.example.com</name>
             <https>
               <tcp-client-parameters>

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                 <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>
               <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>
               <http-client-parameters>
                 <client-identity>
                   <basic>
                     <user-id>bob</user-id>
                     <password>secret</password>
                   </basic>
                 </client-identity>
               </http-client-parameters>
             </https>
           </endpoint>
           <endpoint>
             <name>corp-fw2.example.com</name>
             <https>
               <tcp-client-parameters>

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                 <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>
               <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>
               <http-client-parameters>
                 <client-identity>
                   <basic>
                     <user-id>bob</user-id>
                     <password>secret</password>
                   </basic>
                 </client-identity>
               </http-client-parameters>
             </https>
           </endpoint>
         </endpoints>
         <connection-type>
           <persistent/>
         </connection-type>

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       </restconf-server>
     </initiate>

     <!-- endpoints to listen for RESTCONF Call Home connections on -->
     <listen>
       <endpoint>
         <name>Intranet-facing listener</name>
         <https>
           <tcp-server-parameters>
             <local-address>11.22.33.44</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>
               </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>
           <http-client-parameters>
             <client-identity>
               <basic>
                 <user-id>bob</user-id>
                 <password>secret</password>
               </basic>
             </client-identity>
           </http-client-parameters>
         </https>
       </endpoint>
     </listen>
   </restconf-client>

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2.3.  YANG Module

   This YANG module has normative references to [RFC6991], [RFC8040],
   and [RFC8071], [I-D.ietf-netconf-tcp-client-server],
   [I-D.ietf-netconf-tls-client-server], and
   [I-D.ietf-netconf-http-client-server].

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

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

     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";
     }

     import ietf-tls-client {
       prefix tlsc;
       reference
         "RFC FFFF: YANG Groupings for TLS Clients and TLS Servers";
     }

     import ietf-http-client {
       prefix httpc;
       reference
         "RFC GGGG: YANG Groupings for HTTP Clients and HTTP Servers";
     }

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

     contact

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       "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 RESTCONF 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 IIII
        (https://www.rfc-editor.org/info/rfcIIII); 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 IIII: RESTCONF Client and Server Models";
     }

     // Features

     feature https-initiate {
       description
         "The 'https-initiate' feature indicates that the RESTCONF
          client supports initiating HTTPS connections to RESTCONF
          servers. This feature exists as HTTPS might not be a
          mandatory to implement transport in the future.";
       reference
         "RFC 8040: RESTCONF Protocol";
     }

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     feature http-listen {
       description
         "The 'https-listen' feature indicates that the RESTCONF client
          supports opening a port to listen for incoming RESTCONF
          server call-home connections.  This feature exists as not
          all RESTCONF clients may support RESTCONF call home.";
       reference
         "RFC 8071: NETCONF Call Home and RESTCONF Call Home";
     }

     feature https-listen {
       description
         "The 'https-listen' feature indicates that the RESTCONF client
          supports opening a port to listen for incoming RESTCONF
          server call-home connections.  This feature exists as not
          all RESTCONF clients may support RESTCONF call home.";
       reference
         "RFC 8071: NETCONF Call Home and RESTCONF Call Home";
     }

     // Groupings

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

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

     grouping restconf-client-initiate-stack-grouping {
       description
         "A reusable grouping for configuring a RESTCONF client
          'initiate' protocol stack for a single connection.";

       choice transport {
         mandatory true;
         description
           "Selects between available transports. This is a
            'choice' statement so as to support additional
            transport options to be augmented in.";
         case https {
           if-feature "https-initiate";
           container https {
             must 'tls-client-parameters/client-identity
                   or http-client-parameters/client-identity';
             description

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               "Specifies HTTPS-specific 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 "443";
                   description
                     "The RESTCONF client will attempt to
                      connect to the IANA-assigned well-known
                      port value for 'https' (443) if no value
                      is specified.";
                 }
               }
             }
             container tls-client-parameters {
               description
                 "A wrapper around the TLS client parameters
                  to avoid name collisions.";
               uses tlsc:tls-client-grouping;
             }
             container http-client-parameters {
               description
                 "A wrapper around the HTTP client parameters
                  to avoid name collisions.";
               uses httpc:http-client-grouping;
             }
             container restconf-client-parameters {
               description
                 "A wrapper around the HTTP client parameters
                  to avoid name collisions.";
               uses rcc:restconf-client-grouping;
             }
           }
         }
       }
     } // restconf-client-initiate-stack-grouping

     grouping restconf-client-listen-stack-grouping {
       description
         "A reusable grouping for configuring a RESTCONF 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";

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       choice transport {
         mandatory true;
         description
           "Selects between available transports. This is a
            'choice' statement so as to support additional
            transport options to be augmented in.";
         case http {
           if-feature "http-listen";
           container http {
             description
               "HTTP-specific listening configuration for inbound
                connections.

                This transport option is made available to support
                deployments where the TLS connections are terminated
                by another system (e.g., a load balanacer) fronting
                the client.";
             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 "4336";
                   description
                     "The RESTCONF client will listen on the IANA-
                      assigned well-known port for 'restconf-ch-tls'
                      (4336) if no value is specified.";
                 }
               }
             }
             container http-client-parameters {
               description
                 "A wrapper around the HTTP client parameters
                  to avoid name collisions.";
               uses httpc:http-client-grouping;
             }
             container restconf-client-parameters {
               description
                 "A wrapper around the RESTCONF client parameters
                  to avoid name collisions.";
               uses rcc:restconf-client-grouping;
             }
           }
         }
         case https {
           if-feature "https-listen";
           container https {

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             must 'tls-client-parameters/client-identity
                   or http-client-parameters/client-identity';
             description
               "HTTPS-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 "4336";
                   description
                     "The RESTCONF client will listen on the IANA-
                      assigned well-known port for 'restconf-ch-tls'
                      (4336) if no value is specified.";
                 }
               }
             }
             container tls-client-parameters {
               description
                 "A wrapper around the TLS client parameters
                  to avoid name collisions.";
               uses tlsc:tls-client-grouping;
             }
             container http-client-parameters {
               description
                 "A wrapper around the HTTP client parameters
                  to avoid name collisions.";
               uses httpc:http-client-grouping;
             }
             container restconf-client-parameters {
               description
                 "A wrapper around the RESTCONF client parameters
                  to avoid name collisions.";
               uses rcc:restconf-client-grouping;
             }
           }
         }
       }
     } // restconf-client-listen-stack-grouping

     grouping restconf-client-app-grouping {
       description
         "A reusable grouping for configuring a RESTCONF client
          application that supports both 'initiate' and 'listen'
          protocol stacks for a multiplicity of connections.";
       container initiate {

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         if-feature "https-initiate";
         presence "Enables client to initiate TCP connections";
         description
           "Configures client initiating underlying TCP connections.";
         list restconf-server {
           key "name";
           min-elements 1;
           description
             "List of RESTCONF servers the RESTCONF client is to
              maintain simultaneous connections with.";
           leaf name {
             type string;
             description
               "An arbitrary name for the RESTCONF server.";
           }
           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
                  RESTCONF client 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 restconf-client-initiate-stack-grouping;
             }
           }
           container connection-type {
             description
               "Indicates the RESTCONF client's preference for how
                the RESTCONF 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

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                      RESTCONF server. If the connection goes down,
                      immediately start trying to reconnect to the
                      RESTCONF server, using the reconnection strategy.

                      This connection type minimizes any RESTCONF server
                      to RESTCONF 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 RESTCONF server.

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

                      The RESTCONF client SHOULD gracefully close
                      the underlying TLS 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

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                        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 the underlying TCP session may remain
                        idle. A TCP session will be dropped if it
                        is idle for an interval longer than this
                        number of seconds If set to zero, then the
                        RESTCONF client will never drop a session
                        because it is idle.";
                   }
                 }
               } // periodic-connection
             } // connection-type
           } // connection-type
           container reconnect-strategy {
             description
               "The reconnection strategy directs how a RESTCONF
                client reconnects to a RESTCONF server, after
                discovering its connection to the server has
                dropped, even if due to a reboot.  The RESTCONF
                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.   RESTCONF clients
                      SHOULD be able to remember the last
                      endpoint connected to across reboots.";
                 }

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                 enum random-selection {
                   description
                     "Indicates that reconnections should start with
                      a random endpoint.";
                 }
               }
               default "first-listed";
               description
                 "Specifies which of the RESTCONF server's
                  endpoints the RESTCONF client should start
                  with when trying to connect to the RESTCONF
                  server.";
             }
             leaf max-attempts {
               type uint8 {
                 range "1..max";
               }
               default "3";
               description
                 "Specifies the number times the RESTCONF client
                  tries to connect to a specific endpoint before
                  moving on to the next endpoint in the list
                  (round robin).";
             }
           }
         }
       } // initiate
       container listen {
         if-feature "http-listen or https-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 an
              underlying TCP session may remain idle. A TCP session
              will be dropped if it is idle for an interval longer
              then 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;

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           description
             "List of endpoints to listen for RESTCONF connections.";
           leaf name {
             type string;
             description
               "An arbitrary name for the RESTCONF listen endpoint.";
           }
           uses restconf-client-listen-stack-grouping;
         }
       }
     } // restconf-client-app-grouping

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

   <CODE ENDS>

3.  The "ietf-restconf-server" Module

   The RESTCONF server model presented in this section supports both
   listening for connections as well as initiating call-home
   connections.

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

3.1.  Data Model Overview

3.1.1.  Features

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

   Features:
     +-- http-listen
     +-- https-listen
     +-- https-call-home

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3.1.2.  Groupings

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

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

   Each of these groupings are presented in the following subsections.

3.1.2.1.  The "restconf-server-grouping" Grouping

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

     grouping restconf-server-grouping
       +-- client-identity-mappings
          +---u x509c2n:cert-to-name

   Comments:

   *  The "restconf-server-grouping" defines the configuration for just
      "RESTCONF" part of a protocol stack.  It does not, for instance,
      define any configuration for the "TCP", "TLS", or "HTTP" 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
      RESTCONF 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 "restconf-server-listen-stack-grouping" Grouping

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

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     grouping restconf-server-listen-stack-grouping
       +-- (transport)
          +--:(http) {http-listen}?
          |  +-- http
          |     +-- external-endpoint!
          |     |  +-- address    inet:ip-address
          |     |  +-- port?      inet:port-number
          |     +-- tcp-server-parameters
          |     |  +---u tcps:tcp-server-grouping
          |     +-- http-server-parameters
          |     |  +---u https:http-server-grouping
          |     +-- restconf-server-parameters
          |        +---u rcs:restconf-server-grouping
          +--:(https) {https-listen}?
             +-- https
                +-- tcp-server-parameters
                |  +---u tcps:tcp-server-grouping
                +-- tls-server-parameters
                |  +---u tlss:tls-server-grouping
                +-- http-server-parameters
                |  +---u https:http-server-grouping
                +-- restconf-server-parameters
                   +---u rcs:restconf-server-grouping

   Comments:

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

   *  The "transport" choice node enables both the HTTP and HTTPS
      transports to be configured, with each option enabled by a
      "feature" statement.  The HTTP option is provided to support cases
      where a TLS-terminator is deployed in front of the RESTCONF-
      server.

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

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

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

     grouping restconf-server-callhome-stack-grouping
       +-- (transport)
          +--:(https) {https-listen}?
             +-- https
                +-- tcp-client-parameters
                |  +---u tcpc:tcp-client-grouping
                +-- tls-server-parameters
                |  +---u tlss:tls-server-grouping
                +-- http-server-parameters
                |  +---u https:http-server-grouping
                +-- restconf-server-parameters
                   +---u rcs:restconf-server-grouping

   Comments:

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

   *  The "transport" choice node enables transport options to be
      configured.  This document only defines an "https" option, but
      other options MAY be augmented in.

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

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

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

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     grouping restconf-server-app-grouping
       +-- listen! {http-listen or https-listen}?
       |  +-- endpoint* [name]
       |     +-- name?                                    string
       |     +---u restconf-server-listen-stack-grouping
       +-- call-home! {https-call-home}?
          +-- restconf-client* [name]
             +-- name?                 string
             +-- endpoints
             |  +-- endpoint* [name]
             |     +-- name?                                      string
             |     +---u restconf-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 "restconf-server-app-grouping" defines the configuration for a
      RESTCONF server that supports both listening for connections from
      RESTCONF clients as well as initiatiating call-home connections to
      RESTCONF clients.

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

   *  For the referenced grouping statement(s):

      -  The "restconf-server-listen-stack-grouping" grouping is
         discussed in Section 3.1.2.2 in this document.
      -  The "restconf-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-restconf-server" module:

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   module: ietf-restconf-server
     +--rw restconf-server
        +---u restconf-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-restconf-server" module, the protocol-accessible
      nodes are an instance of the "restconf-server-app-grouping"
      discussed in Section 3.1.2.4 grouping.

   *  The reason for why "restconf-server-app-grouping" exists separate
      from the protocol-accessible nodes definition is so as to enable
      instances of restconf-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 RESTCONF server to
   listen for RESTCONF client connections, as well as configuring call-
   home to one RESTCONF client.

   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 ================

   <restconf-server
     xmlns="urn:ietf:params:xml:ns:yang:ietf-restconf-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 RESTCONF connections on -->
     <listen>
       <endpoint>
         <name>restconf/https</name>
         <https>
           <tcp-server-parameters>
             <local-address>11.22.33.44</local-address>
           </tcp-server-parameters>
           <tls-server-parameters>
             <server-identity>
               <certificate>
                 <keystore-reference>

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                   <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>
           <http-server-parameters>
             <server-name>foo.example.com</server-name>
           </http-server-parameters>
           <restconf-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>
                 <cert-to-name>
                 <id>2</id>
                 <map-type>x509c2n:san-any</map-type>
               </cert-to-name>
             </client-identity-mappings>
           </restconf-server-parameters>
         </https>
       </endpoint>
     </listen>

     <!-- call home to a RESTCONF client with two endpoints -->
     <call-home>
       <restconf-client>
         <name>config-manager</name>
         <endpoints>
           <endpoint>
             <name>east-data-center</name>
             <https>

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               <tcp-client-parameters>
                 <remote-address>east.example.com</remote-address>
                 <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>
               <http-server-parameters>
                 <server-name>foo.example.com</server-name>
               </http-server-parameters>
               <restconf-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>
                   <cert-to-name>
                     <id>2</id>

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                     <map-type>x509c2n:san-any</map-type>
                   </cert-to-name>
                 </client-identity-mappings>
               </restconf-server-parameters>
             </https>
           </endpoint>
           <endpoint>
             <name>west-data-center</name>
             <https>
               <tcp-client-parameters>
                 <remote-address>west.example.com</remote-address>
                 <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>
               <http-server-parameters>
                 <server-name>foo.example.com</server-name>
               </http-server-parameters>
               <restconf-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>
               </restconf-server-parameters>
             </https>
           </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>
       </restconf-client>
     </call-home>
   </restconf-server>

3.3.  YANG Module

   This YANG module has normative references to [RFC6991], [RFC7407],
   [RFC8040], [RFC8071], [I-D.ietf-netconf-tcp-client-server],
   [I-D.ietf-netconf-tls-client-server], and
   [I-D.ietf-netconf-http-client-server].

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

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

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

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     }

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

     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-tls-server {
       prefix tlss;
       reference
         "RFC FFFF: YANG Groupings for TLS Clients and TLS Servers";
     }

     import ietf-http-server {
       prefix https;
       reference
         "RFC GGGG: YANG Groupings for HTTP Clients and HTTP 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
                  <mailto:j.schoenwaelder@jacobs-university.de>";

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     description
       "This module contains a collection of YANG definitions
        for configuring RESTCONF 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 IIII
        (https://www.rfc-editor.org/info/rfcIIII); 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 IIII: RESTCONF Client and Server Models";
     }

     // Features

     feature http-listen {
       description
         "The 'http-listen' feature indicates that the RESTCONF server
          supports opening a port to listen for incoming RESTCONF over
          TPC client connections, whereby the TLS connections are
          terminated by an external system.";
       reference
         "RFC 8040: RESTCONF Protocol";
     }

     feature https-listen {
       description
         "The 'https-listen' feature indicates that the RESTCONF server
          supports opening a port to listen for incoming RESTCONF over

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          TLS client connections, whereby the TLS connections are
          terminated by the server itself.";
       reference
         "RFC 8040: RESTCONF Protocol";
     }

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

     // Groupings

     grouping restconf-server-grouping {
       description
         "A reusable grouping for configuring a RESTCONF 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.,
          'restconf-server-parameters'.  This model purposely does
          not do this itself so as to provide maximum flexibility
          to consuming models.";

       container client-identity-mappings {
         description
           "Specifies mappings through which RESTCONF client X.509
            certificates are used to determine a RESTCONF username.
            If no matching and valid cert-to-name list entry can be
            found, then the RESTCONF server MUST close the connection,
            and MUST NOT accept RESTCONF 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

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                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 restconf-server-listen-stack-grouping {
       description
         "A reusable grouping for configuring a RESTCONF server
          'listen' protocol stack for a single connection.";
       choice transport {
         mandatory true;
         description
           "Selects between available transports. This is a
            'choice' statement so as to support additional
            transport options to be augmented in.";
         case http {
           if-feature "http-listen";
           container http {
             description
               "Configures RESTCONF server stack assuming that
                TLS-termination is handled externally.";
             container external-endpoint {
               presence
                 "Specifies configuration for an external endpoint.";
               description
                 "Identifies contact information for the external
                  system that terminates connections before passing
                  them thru to this server (e.g., a network address
                  translator or a load balancer).  These values have
                  no effect on the local operation of this server, but
                  may be used by the application when needing to
                  inform other systems how to contact this server.";
               leaf address {
                 type inet:ip-address;
                 mandatory true;
                 description
                   "The IP address or hostname of the external system
                    that terminates incoming RESTCONF client
                    connections before forwarding them to this
                    server.";
               }
               leaf port {
                 type inet:port-number;
                 default "443";
                 description

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                   "The port number that the external system listens
                    on for incoming RESTCONF client connections that
                    are forwarded to this server.  The default HTTPS
                    port (443) is used, as expected for a RESTCONF
                    connection.";
               }
             }
             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 "80";
                   description
                     "The RESTCONF server will listen on the IANA-
                      assigned well-known port value for 'http'
                      (80) if no value is specified.";
                 }
               }
             }
             container http-server-parameters {
               description
                 "A wrapper around the HTTP server parameters
                  to avoid name collisions.";
               uses https:http-server-grouping;
             }
             container restconf-server-parameters {
               description
                 "A wrapper around the RESTCONF server parameters
                  to avoid name collisions.";
               uses rcs:restconf-server-grouping;
             }
           }
         }
         case https {
           if-feature "https-listen";
           container https {
             description
               "Configures RESTCONF server stack assuming that
                TLS-termination is handled internally.";
             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 "443";

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                   description
                     "The RESTCONF server will listen on the IANA-
                      assigned well-known port value for 'https'
                      (443) 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;
             }
             container http-server-parameters {
               description
                 "A wrapper around the HTTP server parameters
                  to avoid name collisions.";
               uses https:http-server-grouping;
             }
             container restconf-server-parameters {
               description
                 "A wrapper around the RESTCONF server parameters
                  to avoid name collisions.";
               uses rcs:restconf-server-grouping;
             }
           }
         }
       }
     }

     grouping restconf-server-callhome-stack-grouping {
       description
         "A reusable grouping for configuring a RESTCONF server
          'call-home' protocol stack, for a single connection.";
       choice transport {
         mandatory true;
         description
           "Selects between available transports. This is a
            'choice' statement so as to support additional
            transport options to be augmented in.";
         case https {
           if-feature "https-listen";
           container https {
             description
               "Configures RESTCONF server stack assuming that
                TLS-termination is handled internally.";
             container tcp-client-parameters {
               description

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                 "A wrapper around the TCP client parameters
                  to avoid name collisions.";
               uses tcpc:tcp-client-grouping {
                 refine "remote-port" {
                   default "4336";
                   description
                     "The RESTCONF server will attempt to
                      connect to the IANA-assigned well-known
                      port for 'restconf-ch-tls' (4336) 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;
             }
             container http-server-parameters {
               description
                 "A wrapper around the HTTP server parameters
                  to avoid name collisions.";
               uses https:http-server-grouping;
             }
             container restconf-server-parameters {
               description
                 "A wrapper around the RESTCONF server parameters
                  to avoid name collisions.";
               uses rcs:restconf-server-grouping;
             }
           }
         }
       }
     }

     grouping restconf-server-app-grouping {
       description
         "A reusable grouping for configuring a RESTCONF server
          application that supports both 'listen' and 'call-home'
          protocol stacks for a multiplicity of connections.";
       container listen {
         if-feature "http-listen or https-listen";
         presence
           "Enables the RESTCONF server to listen for RESTCONF
            client connections.";
         description "Configures listen behavior";

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         list endpoint {
           key "name";
           min-elements 1;
           description
             "List of endpoints to listen for RESTCONF connections.";
           leaf name {
             type string;
             description
               "An arbitrary name for the RESTCONF listen endpoint.";
           }
           uses restconf-server-listen-stack-grouping;
         }
       }
       container call-home {
         if-feature "https-call-home";
         presence
           "Enables the RESTCONF server to initiate the underlying
            transport connection to RESTCONF clients.";
         description "Configures call-home behavior";
         list restconf-client {
           key "name";
           min-elements 1;
           description
             "List of RESTCONF clients the RESTCONF server is to
              maintain simultaneous call-home connections with.";
           leaf name {
             type string;
             description
               "An arbitrary name for the remote RESTCONF client.";
           }
           container endpoints {
             description
               "Container for the list of endpoints.";
             list endpoint {
               key "name";
               min-elements 1;
               ordered-by user;
               description
                 "User-ordered list of endpoints for this RESTCONF
                  client.  Defining more than one enables high-
                  availability.";
               leaf name {
                 type string;
                 description
                   "An arbitrary name for this endpoint.";
               }
               uses restconf-server-callhome-stack-grouping;
             }

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           }
           container connection-type {
             description
               "Indicates the RESTCONF server's preference for how the
                RESTCONF 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 RESTCONF
                      client. If the connection goes down, immediately
                      start trying to reconnect to the RESTCONF server,
                      using the reconnection strategy.

                      This connection type minimizes any RESTCONF
                      client to RESTCONF 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 RESTCONF client.

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

                      The RESTCONF client SHOULD gracefully close
                      the underlying TLS connection upon completing
                      planned activities.  If the underlying TLS
                      connection is not closed gracefully, the
                      RESTCONF server MUST immediately attempt
                      to reestablish the connection.

                      In the case that the previous connection is
                      still active (i.e., the RESTCONF client has not
                      closed it yet), establishing a new connection
                      is NOT RECOMMENDED.";

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                   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.";
                   }
                   leaf idle-timeout {
                     type uint16;
                     units "seconds";
                     default 120; // two minutes
                     description
                       "Specifies the maximum number of seconds that
                        the underlying TCP session may remain idle.
                        A TCP 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.";
                   }
                 }
               }
             }
           }
           container reconnect-strategy {
             description
               "The reconnection strategy directs how a RESTCONF server
                reconnects to a RESTCONF client after discovering its
                connection to the client has dropped, even if due to a
                reboot.  The RESTCONF 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).";

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

     // Protocol accessible node, for servers that implement
     // this module.
     container restconf-server {

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       uses restconf-server-app-grouping;
       description
         "Top-level container for RESTCONF server configuration.";
     }

   }

   <CODE ENDS>

4.  Security Considerations

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

   The "ietf-restconf-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 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 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-restconf-server" YANG Module

   The "ietf-restconf-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.

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   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 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 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-restconf-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-restconf-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:

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      name:         ietf-restconf-client
      namespace:    urn:ietf:params:xml:ns:yang:ietf-restconf-client
      prefix:       ncc
      reference:    RFC IIII

      name:         ietf-restconf-server
      namespace:    urn:ietf:params:xml:ns:yang:ietf-restconf-server
      prefix:       ncs
      reference:    RFC IIII

6.  References

6.1.  Normative References

   [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-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-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>.

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   [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>.

   [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>.

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

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

   [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>.

   [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-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-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-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>.

   [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>.

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

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

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

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

Appendix A.  Expanded Tree Diagrams

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A.1.  Expanded Tree Diagram for 'ietf-restconf-client'

   The following tree diagram [RFC8340] provides an overview of the data
   model for the "ietf-restconf-client" module.

   This tree diagram shows all the nodes defined in this module,
   including those defined by "grouping" statements used by this module.

   Please see Section 2.1 for a tree diagram that illustrates what the
   module looks like without all the "grouping" statements expanded.

   XNSERT_TEXT_FROM_FILE(refs/ietf-restconf-client-tree.txt)

A.2.  Expanded Tree Diagram for 'ietf-restconf-server'

   The following tree diagram [RFC8340] provides an overview of the data
   model for the "ietf-restconf-server" module.

   This tree diagram shows all the nodes defined in this module,
   including those defined by "grouping" statements used by this module.

   Please see Section 3.1 for a tree diagram that illustrates what the
   module looks like without all the "grouping" statements expanded.

   XNSERT_TEXT_FROM_FILE(refs/ietf-restconf-server-tree.txt)

Appendix B.  Change Log

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

B.1.  00 to 01

   *  Renamed "keychain" to "keystore".

B.2.  01 to 02

   *  Filled in previously missing 'ietf-restconf-client' module.

   *  Updated the ietf-restconf-server module to accommodate new
      grouping 'ietf-tls-server-grouping'.

B.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 restconf-client??? to be a grouping (not a container).

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B.4.  03 to 04

   *  Added RFC 8174 to Requirements Language Section.

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

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

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

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

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

B.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)

B.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.

B.7.  06 to 07

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

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

   *  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.

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B.8.  07 to 08

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

B.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.

B.10.  09 to 10

   *  Reformatted YANG modules.

B.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.

B.12.  11 to 12

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

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

   *  Updated the "periodic-connnection" description statements to
      better describe behavior when connections are not closed
      gracefully.

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

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   *  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.

B.13.  12 to 13

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

   *  In ietf-restconf-server, Added 'http-listen' (not https-listen)
      choice, to support case when server is behind a TLS-terminator.

   *  Refactored server module to be more like other 'server' models.
      If folks like it, will also apply to the client model, as well as
      to both the netconf client/server models.  Now the 'restconf-
      server-grouping' is just the RC-specific bits (i.e., the "demux"
      container minus the container), 'restconf-server-
      [listen|callhome]-stack-grouping' is the protocol stack for a
      single connection, and 'restconf-server-app-grouping' is
      effectively what was before (both listen+callhome for many
      inbound/outbound endpoints).

B.14.  13 to 14

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

   *  Adjusting from change in TLS client model (removing the top-level
      'certificate' container).

   *  Added "external-endpoint" to the "http-listen" choice in ietf-
      restconf-server.

B.15.  14 to 15

   *  Added missing "or https-listen" clause in a "must" expression.

   *  Refactored the client module similar to how the server module was
      refactored in -13.  Now the 'restconf-client-grouping' is just the
      RC-specific bits, the 'restconf-client-[initiate|listen]-stack-
      grouping' is the protocol stack for a single connection, and
      'restconf-client-app-grouping' is effectively what was before
      (both listen+callhome for many inbound/outbound endpoints).

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B.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.

   *  Updated restconf-client example to reflect that http-client-
      grouping no longer has a "protocol-version" leaf.

B.17.  16 to 17

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

   *  Updated examples to remove the "required" nodes.

B.18.  17 to 18

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

B.19.  18 to 19

   *  Updated examples to remove the 'algorithm' nodes.

   *  Updated examples to reflect the new TLS keepalives structure.

   *  Removed the 'protocol-versions' node from the restconf-server
      examples.

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

B.20.  19 to 20

   *  Moved and changed "must" statement so that either TLS *or* HTTP
      auth must be configured.

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

   *  Updated the Security Considerations section.

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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, Mehmet Ersue, Ramkumar Dhanapal, Balazs
   Kovacs, Radek Krejci, David Lamparter, Ladislav Lhotka, Alan Luchuk,
   Tom Petch, Juergen Schoenwaelder, Phil Shafer, Sean Turner, Bert
   Wijnen.

Author's Address

   Kent Watsen
   Watsen Networks

   Email: kent+ietf@watsen.net

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