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NETCONF Working Group                                          K. Watsen
Internet-Draft                                           Watsen Networks
Intended status: Standards Track                           March 9, 2019
Expires: September 10, 2019


                   RESTCONF Client and Server Models
              draft-ietf-netconf-restconf-client-server-10

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 many 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.

   This document contains references to other drafts in progress, both
   in the Normative References section, as well as in body text
   throughout.  Please update the following references to reflect their
   final RFC assignments:

   o  I-D.ietf-netconf-keystore

   o  I-D.ietf-netconf-tcp-client-server

   o  I-D.ietf-netconf-tls-client-server

   o  I-D.ietf-netconf-http-client-server

   Artwork in this document contains shorthand references to drafts in
   progress.  Please apply the following replacements:

   o  "XXXX" --> the assigned RFC value for this draft

   o  "AAAA" --> the assigned RFC value for I-D.ietf-netconf-tcp-client-
      server

   o  "CCCC" --> the assigned RFC value for I-D.ietf-netconf-tls-client-
      server





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   o  "BBBB" --> the assigned RFC value for I-D.ietf-netconf-http-
      client-server

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

   o  "2019-03-09" --> the publication date of this draft

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

   o  Appendix A.  Change Log

Status of This Memo

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

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

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

   This Internet-Draft will expire on September 10, 2019.

Copyright Notice

   Copyright (c) 2019 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.








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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
     1.1.  Terminology . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  The RESTCONF Client Model . . . . . . . . . . . . . . . . . .   4
     2.1.  Tree Diagram  . . . . . . . . . . . . . . . . . . . . . .   4
     2.2.  Example Usage . . . . . . . . . . . . . . . . . . . . . .   9
     2.3.  YANG Module . . . . . . . . . . . . . . . . . . . . . . .  12
   3.  The RESTCONF Server Model . . . . . . . . . . . . . . . . . .  20
     3.1.  Tree Diagram  . . . . . . . . . . . . . . . . . . . . . .  21
     3.2.  Example Usage . . . . . . . . . . . . . . . . . . . . . .  24
     3.3.  YANG Module . . . . . . . . . . . . . . . . . . . . . . .  27
   4.  Security Considerations . . . . . . . . . . . . . . . . . . .  36
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  37
     5.1.  The IETF XML Registry . . . . . . . . . . . . . . . . . .  37
     5.2.  The YANG Module Names Registry  . . . . . . . . . . . . .  38
   6.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  38
     6.1.  Normative References  . . . . . . . . . . . . . . . . . .  38
     6.2.  Informative References  . . . . . . . . . . . . . . . . .  39
   Appendix A.  Change Log . . . . . . . . . . . . . . . . . . . . .  41
     A.1.  00 to 01  . . . . . . . . . . . . . . . . . . . . . . . .  41
     A.2.  01 to 02  . . . . . . . . . . . . . . . . . . . . . . . .  41
     A.3.  02 to 03  . . . . . . . . . . . . . . . . . . . . . . . .  41
     A.4.  03 to 04  . . . . . . . . . . . . . . . . . . . . . . . .  41
     A.5.  04 to 05  . . . . . . . . . . . . . . . . . . . . . . . .  41
     A.6.  05 to 06  . . . . . . . . . . . . . . . . . . . . . . . .  42
     A.7.  06 to 07  . . . . . . . . . . . . . . . . . . . . . . . .  42
     A.8.  07 to 08  . . . . . . . . . . . . . . . . . . . . . . . .  42
     A.9.  08 to 09  . . . . . . . . . . . . . . . . . . . . . . . .  42
     A.10. 09 to 10  . . . . . . . . . . . . . . . . . . . . . . . .  42
   Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . . .  43
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .  43

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.  Terminology

   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.



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2.  The RESTCONF Client Model

   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.

   This model, like that presented in
   [I-D.ietf-netconf-netconf-client-server], is designed to support any
   number of possible transports.  RESTCONF only supports the TLS
   transport currently, thus this model only supports the TLS transport.

   All private keys and trusted certificates are held in the keystore
   model defined in [I-D.ietf-netconf-keystore].

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

2.1.  Tree Diagram

   The following tree diagram [RFC8340] provides an overview of the data
   model for the "ietf-restconf-client" module.  Just the container is
   displayed below, but there is also a reusable grouping called
   "restconf-client-grouping" that the container is using.

   ========== NOTE: '\\' line wrapping per BCP XX (RFC XXXX) ===========

   module: ietf-restconf-client
     +--rw restconf-client
        +--rw initiate! {initiate}?
        |  +--rw restconf-server* [name]
        |     +--rw name         string
        |     +--rw endpoints
        |        +--rw endpoint* [name]
        |           +--rw name                  string
        |           +--rw (transport)
        |           |  +--:(https) {https-initiate}?
        |           |     +--rw https
        |           |        +--rw remote-address          inet:host
        |           |        +--rw remote-port?
        |           |        |       inet:port-number
        |           |        +--rw local-address?          inet:ip-addr\
   \ess
        |           |        +--rw local-port?
        |           |        |       inet:port-number
        |           |        +--rw tcp-keepalives {tcp-client-keepalive\
   \s}?
        |           |        |  +--rw idle-time?        uint16
        |           |        |  +--rw max-probes?       uint16



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        |           |        |  +--rw probe-interval?   uint16
        |           |        +--rw tls-client-identity
        |           |        |  +--rw (auth-type)
        |           |        |     +--:(certificate)
        |           |        |        +--rw certificate
        |           |        |           +--rw (local-or-keystore)
        |           |        |              +--:(local)
        |           |        |              |        {local-keys-suppor\
   \ted}?
        |           |        |              |  +--rw local-definition
        |           |        |              |     +--rw algorithm?
        |           |        |              |     |       asymmetric-ke\
   \y-algorithm-ref
        |           |        |              |     +--rw public-key?
        |           |        |              |     |       binary
        |           |        |              |     +--rw private-key?
        |           |        |              |     |       union
        |           |        |              |     +---x generate-hidden\
   \-key
        |           |        |              |     |  +---w input
        |           |        |              |     |     +---w algorithm
        |           |        |              |     |             asymmet\
   \ric-key-algorithm-ref
        |           |        |              |     +---x install-hidden-\
   \key
        |           |        |              |     |  +---w input
        |           |        |              |     |     +---w algorithm
        |           |        |              |     |     |       asymmet\
   \ric-key-algorithm-ref
        |           |        |              |     |     +---w public-ke\
   \y?
        |           |        |              |     |     |       binary
        |           |        |              |     |     +---w private-k\
   \ey?
        |           |        |              |     |             binary
        |           |        |              |     +--rw cert?
        |           |        |              |     |       end-entity-ce\
   \rt-cms
        |           |        |              |     +---n certificate-exp\
   \iration
        |           |        |              |        +-- expiration-date
        |           |        |              |                yang:date-\
   \and-time
        |           |        |              +--:(keystore)
        |           |        |                       {keystore-supporte\
   \d}?
        |           |        |                 +--rw keystore-reference?
        |           |        |                         ks:asymmetric-ke\



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   \y-certificate-ref
        |           |        +--rw tls-server-auth
        |           |        |  +--rw pinned-ca-certs?
        |           |        |  |       ta:pinned-certificates-ref
        |           |        |  |       {ta:x509-certificates}?
        |           |        |  +--rw pinned-server-certs?
        |           |        |          ta:pinned-certificates-ref
        |           |        |          {ta:x509-certificates}?
        |           |        +--rw tls-hello-params
        |           |        |       {tls-client-hello-params-config}?
        |           |        |  +--rw tls-versions
        |           |        |  |  +--rw tls-version*   identityref
        |           |        |  +--rw cipher-suites
        |           |        |     +--rw cipher-suite*   identityref
        |           |        +--rw tls-keepalives {tls-client-keepalive\
   \s}?
        |           |        |  +--rw max-wait?       uint16
        |           |        |  +--rw max-attempts?   uint8
        |           |        +--rw http-client-identity
        |           |        |  +--rw (auth-type)?
        |           |        |     +--:(basic)
        |           |        |     |  +--rw basic
        |           |        |     |     +--rw user-id?    string
        |           |        |     |     +--rw password?   string
        |           |        |     +--:(bearer)
        |           |        |     |  +--rw bearer
        |           |        |     |     +--rw token?   string
        |           |        |     +--:(digest)
        |           |        |     |  +--rw digest
        |           |        |     |     +--rw username?   string
        |           |        |     |     +--rw password?   string
        |           |        |     +--:(hoba)
        |           |        |     |  +--rw hoba
        |           |        |     +--:(mutual)
        |           |        |     |  +--rw mutual
        |           |        |     +--:(negotiate)
        |           |        |     |  +--rw negotiate
        |           |        |     +--:(oauth)
        |           |        |     |  +--rw oauth
        |           |        |     +--:(scram-sha-1)
        |           |        |     |  +--rw scram-sha-1
        |           |        |     +--:(scram-sha-256)
        |           |        |     |  +--rw scram-sha-256
        |           |        |     +--:(vapid)
        |           |        |        +--rw vapid
        |           |        +--rw http-keepalives
        |           |                {http-client-keepalives}?
        |           |           +--rw max-wait?       uint16



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        |           |           +--rw max-attempts?   uint8
        |           +--rw connection-type
        |           |  +--rw (connection-type)
        |           |     +--:(persistent-connection)
        |           |     |  +--rw persistent!
        |           |     +--:(periodic-connection)
        |           |        +--rw periodic!
        |           |           +--rw period?         uint16
        |           |           +--rw anchor-time?    yang:date-and-time
        |           |           +--rw idle-timeout?   uint16
        |           +--rw reconnect-strategy
        |              +--rw start-with?     enumeration
        |              +--rw max-attempts?   uint8
        +--rw listen! {listen}?
           +--rw idle-timeout?   uint16
           +--rw endpoint* [name]
              +--rw name           string
              +--rw (transport)
                 +--:(https) {https-listen}?
                    +--rw https
                       +--rw local-address           inet:ip-address
                       +--rw local-port?             inet:port-number
                       +--rw tcp-keepalives {tcp-server-keepalives}?
                       |  +--rw idle-time?        uint16
                       |  +--rw max-probes?       uint16
                       |  +--rw probe-interval?   uint16
                       +--rw tls-client-identity
                       |  +--rw (auth-type)
                       |     +--:(certificate)
                       |        +--rw certificate
                       |           +--rw (local-or-keystore)
                       |              +--:(local) {local-keys-supported\
   \}?
                       |              |  +--rw local-definition
                       |              |     +--rw algorithm?
                       |              |     |       asymmetric-key-algo\
   \rithm-ref
                       |              |     +--rw public-key?
                       |              |     |       binary
                       |              |     +--rw private-key?
                       |              |     |       union
                       |              |     +---x generate-hidden-key
                       |              |     |  +---w input
                       |              |     |     +---w algorithm
                       |              |     |             asymmetric-ke\
   \y-algorithm-ref
                       |              |     +---x install-hidden-key
                       |              |     |  +---w input



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                       |              |     |     +---w algorithm
                       |              |     |     |       asymmetric-ke\
   \y-algorithm-ref
                       |              |     |     +---w public-key?
                       |              |     |     |       binary
                       |              |     |     +---w private-key?
                       |              |     |             binary
                       |              |     +--rw cert?
                       |              |     |       end-entity-cert-cms
                       |              |     +---n certificate-expiration
                       |              |        +-- expiration-date
                       |              |                yang:date-and-ti\
   \me
                       |              +--:(keystore) {keystore-supporte\
   \d}?
                       |                 +--rw keystore-reference?
                       |                         ks:asymmetric-key-cert\
   \ificate-ref
                       +--rw tls-server-auth
                       |  +--rw pinned-ca-certs?
                       |  |       ta:pinned-certificates-ref
                       |  |       {ta:x509-certificates}?
                       |  +--rw pinned-server-certs?
                       |          ta:pinned-certificates-ref
                       |          {ta:x509-certificates}?
                       +--rw tls-hello-params
                       |       {tls-client-hello-params-config}?
                       |  +--rw tls-versions
                       |  |  +--rw tls-version*   identityref
                       |  +--rw cipher-suites
                       |     +--rw cipher-suite*   identityref
                       +--rw tls-keepalives {tls-client-keepalives}?
                       |  +--rw max-wait?       uint16
                       |  +--rw max-attempts?   uint8
                       +--rw http-client-identity
                       |  +--rw (auth-type)?
                       |     +--:(basic)
                       |     |  +--rw basic
                       |     |     +--rw user-id?    string
                       |     |     +--rw password?   string
                       |     +--:(bearer)
                       |     |  +--rw bearer
                       |     |     +--rw token?   string
                       |     +--:(digest)
                       |     |  +--rw digest
                       |     |     +--rw username?   string
                       |     |     +--rw password?   string
                       |     +--:(hoba)



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                       |     |  +--rw hoba
                       |     +--:(mutual)
                       |     |  +--rw mutual
                       |     +--:(negotiate)
                       |     |  +--rw negotiate
                       |     +--:(oauth)
                       |     |  +--rw oauth
                       |     +--:(scram-sha-1)
                       |     |  +--rw scram-sha-1
                       |     +--:(scram-sha-256)
                       |     |  +--rw scram-sha-256
                       |     +--:(vapid)
                       |        +--rw vapid
                       +--rw http-keepalives {http-client-keepalives}?
                          +--rw max-wait?       uint16
                          +--rw max-attempts?   uint8

2.2.  Example Usage

   The following example illustrates configuring a RESTCONF client to
   initiate connections, as well as listening for call-home connections.

   This example is consistent with the examples presented in Section 3.2
   of [I-D.ietf-netconf-keystore].

   ========== NOTE: '\\' line wrapping per BCP XX (RFC XXXX) ===========

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

     <!-- RESTCONF servers to initiate connections to -->
     <initiate>
       <restconf-server>
         <name>corp-fw1</name>
         <endpoints>
           <endpoint>
             <name>corp-fw1.example.com</name>
             <https>
               <remote-address>corp-fw1.example.com</remote-address>
               <tcp-keepalives>
                 <idle-time>15</idle-time>
                 <max-probes>3</max-probes>
                 <probe-interval>30</probe-interval>
               </tcp-keepalives>
               <tls-client-identity>
                 <certificate>
                   <local-definition>
                     <algorithm xmlns:ct="urn:ietf:params:xml:ns:yang:i\



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   \etf-crypto-types">ct:rsa2048</algorithm>
                     <private-key>base64encodedvalue==</private-key>
                     <public-key>base64encodedvalue==</public-key>
                     <cert>base64encodedvalue==</cert>
                   </local-definition>
                 </certificate>
               </tls-client-identity>
               <tls-server-auth>
                 <pinned-ca-certs>explicitly-trusted-server-ca-certs</p\
   \inned-ca-certs>
                 <pinned-server-certs>explicitly-trusted-server-certs</\
   \pinned-server-certs>
               </tls-server-auth>
               <tls-keepalives>
                 <max-wait>30</max-wait>
                 <max-attempts>3</max-attempts>
               </tls-keepalives>
               <http-client-identity>
                 <basic>
                   <user-id>bob</user-id>
                   <password>secret</password>
                 </basic>
               </http-client-identity>
               <http-keepalives>
                 <max-wait>30</max-wait>
                 <max-attempts>3</max-attempts>
               </http-keepalives>
             </https>
             <connection-type>
               <persistent/>
             </connection-type>
           </endpoint>
           <endpoint>
             <name>corp-fw2.example.com</name>
             <https>
               <remote-address>corp-fw2.example.com</remote-address>
               <tcp-keepalives>
                 <idle-time>15</idle-time>
                 <max-probes>3</max-probes>
                 <probe-interval>30</probe-interval>
               </tcp-keepalives>
               <tls-client-identity>
                 <certificate>
                   <local-definition>
                     <algorithm xmlns:ct="urn:ietf:params:xml:ns:yang:i\
   \etf-crypto-types">ct:rsa2048</algorithm>
                     <private-key>base64encodedvalue==</private-key>
                     <public-key>base64encodedvalue==</public-key>



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                     <cert>base64encodedvalue==</cert>
                   </local-definition>
                 </certificate>
               </tls-client-identity>
               <tls-server-auth>
                 <pinned-ca-certs>explicitly-trusted-server-ca-certs</p\
   \inned-ca-certs>
                 <pinned-server-certs>explicitly-trusted-server-certs</\
   \pinned-server-certs>
               </tls-server-auth>
               <tls-keepalives>
                 <max-wait>30</max-wait>
                 <max-attempts>3</max-attempts>
               </tls-keepalives>
               <http-client-identity>
                 <basic>
                   <user-id>bob</user-id>
                   <password>secret</password>
                 </basic>
               </http-client-identity>
               <http-keepalives>
                 <max-wait>30</max-wait>
                 <max-attempts>3</max-attempts>
               </http-keepalives>
             </https>
             <connection-type>
               <persistent/>
             </connection-type>
           </endpoint>
         </endpoints>
       </restconf-server>
     </initiate>

     <!-- endpoints to listen for RESTCONF Call Home connections on -->
     <listen>
       <endpoint>
         <name>Intranet-facing listener</name>
         <https>
           <local-address>11.22.33.44</local-address>
           <tls-client-identity>
             <certificate>
               <local-definition>
                 <algorithm xmlns:ct="urn:ietf:params:xml:ns:yang:ietf-\
   \crypto-types">ct:rsa2048</algorithm>
                 <private-key>base64encodedvalue==</private-key>
                 <public-key>base64encodedvalue==</public-key>
                 <cert>base64encodedvalue==</cert>
               </local-definition>



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             </certificate>
           </tls-client-identity>
           <tls-server-auth>
             <pinned-ca-certs>explicitly-trusted-server-ca-certs</pinne\
   \d-ca-certs>
             <pinned-server-certs>explicitly-trusted-server-certs</pinn\
   \ed-server-certs>
           </tls-server-auth>
         </https>
       </endpoint>
     </listen>
   </restconf-client>

2.3.  YANG Module

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

   <CODE BEGINS> file "ietf-restconf-client@2019-03-09.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 AAAA: YANG Groupings for TCP Clients and TCP Servers";
     }

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

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



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     }

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

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

     contact
       "WG Web:   <http://datatracker.ietf.org/wg/restconf/>
        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.

        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.

        Copyright (c) 2019 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
        (http://trustee.ietf.org/license-info).

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

     revision 2019-03-09 {
       description
         "Initial version";
       reference
         "RFC XXXX: RESTCONF Client and Server Models";
     }




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     // Features

     feature initiate {
       description
         "The 'initiate' feature indicates that the RESTCONF client
          supports initiating RESTCONF connections to RESTCONF servers
          using at least one transport (e.g., HTTPS, etc.).";
     }

     feature https-initiate {
       if-feature "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";
     }

     feature listen {
       description
         "The 'listen' feature indicates that the RESTCONF client
          supports opening a port to accept RESTCONF server call
          home connections using at least one transport (e.g.,
          HTTPS, etc.).";
     }

     feature https-listen {
       if-feature "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
         "Top-level grouping for RESTCONF client configuration.";
       container initiate {
         if-feature "initiate";
         presence "Enables client to initiate TCP connections";
         description



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           "Configures client initiating underlying TCP connections.";
         list restconf-server {
           key "name";
           min-elements 1;
           description
             "List of RESTCONF servers the RESTCONF client is to
              initiate connections to in parallel.";
           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.";
               }
               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 {
                     description
                       "Specifies HTTPS-specific transport
                        configuration.";
                     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.";



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                       }
                     }
                     uses tlsc:tls-client-grouping {
                       refine "tls-client-identity/auth-type" {
                         mandatory true;
                         description
                           "RESTCONF clients MUST pass some
                            authentication credentials.";
                       }
                     }
                     uses httpc:http-client-grouping;
                   }
                 } // https
               } // transport
               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
                          RESTCONF server. If the connection goes down,
                          immediately start trying to reconnect to it,
                          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.
                          The RESTCONF server should close the
                          underlying TCP connection upon completing
                          planned activities.

                          This connection type increases resource
                          utilization, albeit with increased delay in



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                          RESTCONF server to RESTCONF client
                          interactions.";
                       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
                            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



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                    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.";
                     }
                     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).";
                 }
               } // reconnect-strategy
             } // endpoint



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           } // endpoints
         } // restconf-server
       } // initiate

       container listen {
         if-feature "listen";
         presence "Enables client to accept call-home connections";
         description
           "Configures client accepting 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
              than this number of seconds.  If set to zero, then
              the server will never drop a session because it is
              idle.  Sessions that have a notification subscription
              active are never dropped.";
         }
         list endpoint {
           key "name";
           min-elements 1;
           description
             "List of endpoints to listen for RESTCONF connections.";
           leaf name {
             type string;
             description
               "An arbitrary name for the RESTCONF listen endpoint.";
           }
           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
                   "HTTPS-specific listening configuration for inbound
                    connections.";
                 uses tcps:tcp-server-grouping {
                   refine "local-port" {
                     default "4336";
                     description



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                       "The RESTCONF client will listen on the IANA-
                        assigned well-known port for 'restconf-ch-tls'
                        (4336) if no value is specified.";
                   }
                 }
                 uses tlsc:tls-client-grouping {
                   refine "tls-client-identity/auth-type" {
                     mandatory true;
                     description
                       "RESTCONF clients MUST pass some authentication
                        credentials.";
                   }
                 }
                 uses httpc:http-client-grouping;
               }
             } // case https
           } // transport
         } // endpoint
       } // listen
     } // restconf-client

     // Protocol accessible node, for servers that implement this
     // module.

     container restconf-client {
       uses restconf-client-grouping;
       description
         "Top-level container for RESTCONF client configuration.";
     }
   }
   <CODE ENDS>

3.  The RESTCONF Server Model

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

   All private keys and trusted certificates are held in the keystore
   model defined in [I-D.ietf-netconf-keystore].

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








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3.1.  Tree Diagram

   The following tree diagram [RFC8340] provides an overview of the data
   model for the "ietf-restconf-server" module.  Just the container is
   displayed below, but there is also a reusable grouping called
   "restconf-server-grouping" that the container is using.

   ========== NOTE: '\\' line wrapping per BCP XX (RFC XXXX) ===========

   module: ietf-restconf-server
     +--rw restconf-server
        +--rw listen! {listen}?
        |  +--rw endpoint* [name]
        |     +--rw name           string
        |     +--rw (transport)
        |        +--:(https) {https-listen}?
        |           +--rw https
        |              +--rw local-address          inet:ip-address
        |              +--rw local-port?            inet:port-number
        |              +--rw tcp-keepalives {tcp-server-keepalives}?
        |              |  +--rw idle-time?        uint16
        |              |  +--rw max-probes?       uint16
        |              |  +--rw probe-interval?   uint16
        |              +--rw tls-server-identity
        |              |  +--rw (local-or-keystore)
        |              |     +--:(local) {local-keys-supported}?
        |              |     |  +--rw local-definition
        |              |     |     +--rw algorithm?
        |              |     |     |       asymmetric-key-algorithm-ref
        |              |     |     +--rw public-key?               bina\
   \ry
        |              |     |     +--rw private-key?              union
        |              |     |     +---x generate-hidden-key
        |              |     |     |  +---w input
        |              |     |     |     +---w algorithm
        |              |     |     |             asymmetric-key-algorit\
   \hm-ref
        |              |     |     +---x install-hidden-key
        |              |     |     |  +---w input
        |              |     |     |     +---w algorithm
        |              |     |     |     |       asymmetric-key-algorit\
   \hm-ref
        |              |     |     |     +---w public-key?    binary
        |              |     |     |     +---w private-key?   binary
        |              |     |     +--rw cert?
        |              |     |     |       end-entity-cert-cms
        |              |     |     +---n certificate-expiration
        |              |     |        +-- expiration-date



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        |              |     |                yang:date-and-time
        |              |     +--:(keystore) {keystore-supported}?
        |              |        +--rw keystore-reference?
        |              |                ks:asymmetric-key-certificate-r\
   \ef
        |              +--rw tls-client-auth
        |              |  +--rw pinned-ca-certs?
        |              |  |       ta:pinned-certificates-ref
        |              |  |       {ta:x509-certificates}?
        |              |  +--rw pinned-client-certs?
        |              |  |       ta:pinned-certificates-ref
        |              |  |       {ta:x509-certificates}?
        |              |  +--rw cert-maps
        |              |     +--rw cert-to-name* [id]
        |              |        +--rw id             uint32
        |              |        +--rw fingerprint
        |              |        |       x509c2n:tls-fingerprint
        |              |        +--rw map-type       identityref
        |              |        +--rw name           string
        |              +--rw tls-hello-params
        |              |       {tls-server-hello-params-config}?
        |              |  +--rw tls-versions
        |              |  |  +--rw tls-version*   identityref
        |              |  +--rw cipher-suites
        |              |     +--rw cipher-suite*   identityref
        |              +--rw tls-keepalives {tls-server-keepalives}?
        |              |  +--rw max-wait?       uint16
        |              |  +--rw max-attempts?   uint8
        |              +--rw http-keepalives {http-server-keepalives}?
        |                 +--rw max-wait?       uint16
        |                 +--rw max-attempts?   uint8
        +--rw call-home! {call-home}?
           +--rw restconf-client* [name]
              +--rw name                  string
              +--rw endpoints
              |  +--rw endpoint* [name]
              |     +--rw name           string
              |     +--rw (transport)
              |        +--:(https) {https-call-home}?
              |           +--rw https
              |              +--rw remote-address         inet:host
              |              +--rw remote-port?           inet:port-num\
   \ber
              |              +--rw local-address?         inet:ip-addre\
   \ss
              |              +--rw local-port?            inet:port-num\
   \ber
              |              +--rw tcp-keepalives {tcp-client-keepalive\



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   \s}?
              |              |  +--rw idle-time?        uint16
              |              |  +--rw max-probes?       uint16
              |              |  +--rw probe-interval?   uint16
              |              +--rw tls-server-identity
              |              |  +--rw (local-or-keystore)
              |              |     +--:(local) {local-keys-supported}?
              |              |     |  +--rw local-definition
              |              |     |     +--rw algorithm?
              |              |     |     |       asymmetric-key-algorit\
   \hm-ref
              |              |     |     +--rw public-key?
              |              |     |     |       binary
              |              |     |     +--rw private-key?
              |              |     |     |       union
              |              |     |     +---x generate-hidden-key
              |              |     |     |  +---w input
              |              |     |     |     +---w algorithm
              |              |     |     |             asymmetric-key-a\
   \lgorithm-ref
              |              |     |     +---x install-hidden-key
              |              |     |     |  +---w input
              |              |     |     |     +---w algorithm
              |              |     |     |     |       asymmetric-key-a\
   \lgorithm-ref
              |              |     |     |     +---w public-key?    bin\
   \ary
              |              |     |     |     +---w private-key?   bin\
   \ary
              |              |     |     +--rw cert?
              |              |     |     |       end-entity-cert-cms
              |              |     |     +---n certificate-expiration
              |              |     |        +-- expiration-date
              |              |     |                yang:date-and-time
              |              |     +--:(keystore) {keystore-supported}?
              |              |        +--rw keystore-reference?
              |              |                ks:asymmetric-key-certifi\
   \cate-ref
              |              +--rw tls-client-auth
              |              |  +--rw pinned-ca-certs?
              |              |  |       ta:pinned-certificates-ref
              |              |  |       {ta:x509-certificates}?
              |              |  +--rw pinned-client-certs?
              |              |  |       ta:pinned-certificates-ref
              |              |  |       {ta:x509-certificates}?
              |              |  +--rw cert-maps
              |              |     +--rw cert-to-name* [id]
              |              |        +--rw id             uint32



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              |              |        +--rw fingerprint
              |              |        |       x509c2n:tls-fingerprint
              |              |        +--rw map-type       identityref
              |              |        +--rw name           string
              |              +--rw tls-hello-params
              |              |       {tls-server-hello-params-config}?
              |              |  +--rw tls-versions
              |              |  |  +--rw tls-version*   identityref
              |              |  +--rw cipher-suites
              |              |     +--rw cipher-suite*   identityref
              |              +--rw tls-keepalives {tls-server-keepalive\
   \s}?
              |              |  +--rw max-wait?       uint16
              |              |  +--rw max-attempts?   uint8
              |              +--rw http-keepalives
              |                      {http-server-keepalives}?
              |                 +--rw max-wait?       uint16
              |                 +--rw max-attempts?   uint8
              +--rw connection-type
              |  +--rw (connection-type)
              |     +--:(persistent-connection)
              |     |  +--rw persistent!
              |     +--:(periodic-connection)
              |        +--rw periodic!
              |           +--rw period?         uint16
              |           +--rw anchor-time?    yang:date-and-time
              |           +--rw idle-timeout?   uint16
              +--rw reconnect-strategy
                 +--rw start-with?     enumeration
                 +--rw max-attempts?   uint8

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 3.2
   of [I-D.ietf-netconf-keystore].

   ========== NOTE: '\\' line wrapping per BCP XX (RFC XXXX) ===========

   <restconf-server
     xmlns="urn:ietf:params:xml:ns:yang:ietf-restconf-server"
     xmlns:x509c2n="urn:ietf:params:xml:ns:yang:ietf-x509-cert-to-name">

     <!-- endpoints to listen for RESTCONF connections on -->
     <listen>



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       <endpoint>
         <name>netconf/tls</name>
         <https>
           <local-address>11.22.33.44</local-address>
           <tls-server-identity>
             <local-definition>
               <algorithm xmlns:ct="urn:ietf:params:xml:ns:yang:ietf-cr\
   \ypto-types">ct:rsa2048</algorithm>
               <private-key>base64encodedvalue==</private-key>
               <public-key>base64encodedvalue==</public-key>
               <cert>base64encodedvalue==</cert>
             </local-definition>
           </tls-server-identity>
           <tls-client-auth>
             <pinned-ca-certs>explicitly-trusted-client-ca-certs</pinne\
   \d-ca-certs>
             <pinned-client-certs>explicitly-trusted-client-certs</pinn\
   \ed-client-certs>
             <cert-maps>
               <cert-to-name>
                 <id>1</id>
                 <fingerprint>11:0A:05:11:00</fingerprint>
                 <map-type>x509c2n:san-any</map-type>
               </cert-to-name>
               <cert-to-name>
                 <id>2</id>
                 <fingerprint>B3:4F:A1:8C:54</fingerprint>
                 <map-type>x509c2n:specified</map-type>
                 <name>scooby-doo</name>
               </cert-to-name>
             </cert-maps>
           </tls-client-auth>
         </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>
               <remote-address>east.example.com</remote-address>
               <tls-server-identity>
                 <local-definition>
                   <algorithm xmlns:ct="urn:ietf:params:xml:ns:yang:iet\



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   \f-crypto-types">ct:rsa2048</algorithm>
                   <private-key>base64encodedvalue==</private-key>
                   <public-key>base64encodedvalue==</public-key>
                   <cert>base64encodedvalue==</cert>
                 </local-definition>
               </tls-server-identity>
               <tls-client-auth>
                 <pinned-ca-certs>explicitly-trusted-client-ca-certs</p\
   \inned-ca-certs>
                 <pinned-client-certs>explicitly-trusted-client-certs</\
   \pinned-client-certs>
                 <cert-maps>
                   <cert-to-name>
                     <id>1</id>
                     <fingerprint>11:0A:05:11:00</fingerprint>
                     <map-type>x509c2n:san-any</map-type>
                   </cert-to-name>
                   <cert-to-name>
                     <id>2</id>
                     <fingerprint>B3:4F:A1:8C:54</fingerprint>
                     <map-type>x509c2n:specified</map-type>
                     <name>scooby-doo</name>
                   </cert-to-name>
                 </cert-maps>
               </tls-client-auth>
             </https>
           </endpoint>
           <endpoint>
             <name>west-data-center</name>
             <https>
               <remote-address>west.example.com</remote-address>
               <tcp-keepalives>
                 <idle-time>15</idle-time>
                 <max-probes>3</max-probes>
                 <probe-interval>30</probe-interval>
               </tcp-keepalives>
               <tls-server-identity>
                 <local-definition>
                   <algorithm xmlns:ct="urn:ietf:params:xml:ns:yang:iet\
   \f-crypto-types">ct:rsa2048</algorithm>
                   <private-key>base64encodedvalue==</private-key>
                   <public-key>base64encodedvalue==</public-key>
                   <cert>base64encodedvalue==</cert>
                 </local-definition>
               </tls-server-identity>
               <tls-client-auth>
                 <pinned-ca-certs>explicitly-trusted-client-ca-certs</p\
   \inned-ca-certs>



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                 <pinned-client-certs>explicitly-trusted-client-certs</\
   \pinned-client-certs>
                 <cert-maps>
                   <cert-to-name>
                     <id>1</id>
                     <fingerprint>11:0A:05:11:00</fingerprint>
                     <map-type>x509c2n:san-any</map-type>
                   </cert-to-name>
                   <cert-to-name>
                     <id>2</id>
                     <fingerprint>B3:4F:A1:8C:54</fingerprint>
                     <map-type>x509c2n:specified</map-type>
                     <name>scooby-doo</name>
                   </cert-to-name>
                 </cert-maps>
               </tls-client-auth>
               <http-keepalives>
                 <max-wait>30</max-wait>
                 <max-attempts>3</max-attempts>
               </http-keepalives>
             </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.kwatsen-netconf-tcp-client-server],
   [I-D.ietf-netconf-tls-client-server], and
   [I-D.kwatsen-netconf-http-client-server].

   <CODE BEGINS> file "ietf-restconf-server@2019-03-09.yang"
   module ietf-restconf-server {
     yang-version 1.1;



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     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";
     }

     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 AAAA: YANG Groupings for TCP Clients and TCP Servers";
     }

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

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

     import ietf-http-server {
       prefix https;
       reference
         "RFC CCCC: 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



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

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

        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.

        Copyright (c) 2019 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
        (http://trustee.ietf.org/license-info).

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

     revision 2019-03-09 {
       description
         "Initial version";
       reference
         "RFC XXXX: RESTCONF Client and Server Models";
     }

     // Features

     feature listen {
       description
         "The 'listen' feature indicates that the RESTCONF server
          supports opening a port to accept RESTCONF client connections
          using at least one transport (e.g., HTTPS, etc.).";
     }

     feature https-listen {
       if-feature "listen";
       description
         "The 'https-listen' feature indicates that the RESTCONF server
          supports opening a port to listen for incoming RESTCONF
          client connections.  This feature exists as HTTPS might not



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          be a mandatory to implement transport in the future.";
       reference
         "RFC 8040: RESTCONF Protocol";
     }

     feature call-home {
       description
         "The 'call-home' feature indicates that the RESTCONF
          server supports initiating RESTCONF call home connections
          to RESTCONF clients using at least one transport (e.g.,
          HTTPS, etc.).";
       reference
         "RFC 8071: NETCONF Call Home and RESTCONF Call Home";
     }

     feature https-call-home {
       if-feature "call-home";
       description
         "The 'https-call-home' feature indicates that the RESTCONF
          server supports initiating connections to RESTCONF clients.
          This feature exists as not all RESTCONF servers may
          support RESTCONF call home.";
       reference
         "RFC 8071: NETCONF Call Home and RESTCONF Call Home";
     }

     // Groupings

     grouping restconf-server-grouping {
       description
         "Top-level grouping for RESTCONF server configuration.";
       container listen {
         if-feature "listen";
         presence "Enables server to listen for TCP connections";
         description "Configures listen behavior";
         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.";
           }
           choice transport {
             mandatory true;
             description



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               "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
                   "HTTPS-specific listening configuration for inbound
                    connections.";
                 uses tcps:tcp-server-grouping {
                   refine "local-port" {
                     default "443";
                     description
                       "The RESTCONF server will listen on the IANA-
                        assigned well-known port value for 'https'
                        (443) if no value is specified.";
                   }
                 }
                 uses tlss:tls-server-grouping {
                   refine "tls-client-auth" {
                     must 'pinned-ca-certs or pinned-client-certs';
                     description
                       "RESTCONF servers MUST be able to validate
                        clients.";
                   }
                   augment "tls-client-auth" {
                     description
                       "Augments in the cert-to-name structure,
                        so the RESTCONF server can map TLS-layer
                        client certificates to RESTCONF usernames.";
                     container cert-maps {
                       uses x509c2n:cert-to-name;
                       description
                         "The cert-maps container is used by a TLS-
                          based RESTCONF server to map the RESTCONF
                          client's presented X.509 certificate to
                          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 https:http-server-grouping;



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               } // https container
             } // tls case
           } // transport
         } // endpoint
       } // listen

       container call-home {
         if-feature "call-home";
         presence "Enables server to initiate TCP connections";
         description "Configures call-home behavior";
         list restconf-client {
           key "name";
           min-elements 1;
           description
             "List of RESTCONF clients the RESTCONF server is to
              initiate call-home connections to in parallel.";
           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.";
               }
               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-call-home";
                   container https {
                     description
                       "Specifies HTTPS-specific call-home transport



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                        configuration.";
                     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.";
                       }
                     }
                     uses tlss:tls-server-grouping {
                       refine "tls-client-auth" {
                         must 'pinned-ca-certs or pinned-client-certs';
                         description
                           "RESTCONF servers MUST be able to validate
                            clients.";
                       }
                       augment "tls-client-auth" {
                         description
                           "Augments in the cert-to-name structure,
                            so the RESTCONF server can map TLS-layer
                            client certificates to RESTCONF usernames.";
                         container cert-maps {
                           uses x509c2n:cert-to-name;
                           description
                             "The cert-maps container is used by a
                              TLS-based RESTCONF server to map the
                              RESTCONF client's presented X.509
                              certificate to 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 https:http-server-grouping;
                   }
                 }
               } // transport
             } // endpoint
           } // endpoints
           container connection-type {



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             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 it, 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.  The
                      RESTCONF client should close the underlying TCP
                      connection upon completing planned activities.

                      This connection type increases resource
                      utilization, albeit with increased delay in
                      RESTCONF client to RESTCONF client interactions.";
                   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})';
                     }



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                     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).";
             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



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                      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-grouping

     // Protocol accessible node, for servers that implement this
     // module.

     container restconf-server {
       uses restconf-server-grouping;
       description
         "Top-level container for RESTCONF server configuration.";
     }
   }
   <CODE ENDS>

4.  Security Considerations

   The YANG module defined in this document uses a grouping defined in
   [I-D.ietf-netconf-tls-client-server].  Please see the Security
   Considerations section in that document for concerns related that
   grouping.




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   The YANG module defined in this document is 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.

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

      /: The entire data trees defined by the modules defined in this
         draft are sensitive to write operations.  For instance, the
         addition or removal of references to keys, certificates,
         trusted anchors, etc., can dramatically alter the implemented
         security policy.  However, no NACM annotations are applied as
         the data SHOULD be editable by users other than a designated
         'recovery session'.

   Some of the readable data nodes in this YANG module may be considered
   sensitive or vulnerable in some network environments.  It is thus
   important to control read access (e.g., via get, get-config, or
   notification) to these data nodes.  These are the subtrees and data
   nodes and their sensitivity/vulnerability:

      NONE

   Some of the RPC operations in this YANG module may be considered
   sensitive or vulnerable in some network environments.  It is thus
   important to control access to these operations.  These are the
   operations and their sensitivity/vulnerability:

      NONE

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:



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      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:

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

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

6.  References

6.1.  Normative References

   [I-D.ietf-netconf-keystore]
              Watsen, K., "YANG Data Model for a Centralized Keystore
              Mechanism", draft-ietf-netconf-keystore-08 (work in
              progress), March 2019.

   [I-D.ietf-netconf-tls-client-server]
              Watsen, K., Wu, G., and L. Xia, "YANG Groupings for TLS
              Clients and TLS Servers", draft-ietf-netconf-tls-client-
              server-08 (work in progress), October 2018.

   [I-D.kwatsen-netconf-http-client-server]
              Watsen, K., "YANG Groupings for HTTP Clients and HTTP
              Servers", draft-kwatsen-netconf-http-client-server-00
              (work in progress), March 2019.

   [I-D.kwatsen-netconf-tcp-client-server]
              Watsen, K., "YANG Groupings for TCP Clients and TCP
              Servers", draft-kwatsen-netconf-tcp-client-server-00 (work
              in progress), March 2019.




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

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

   [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-netconf-client-server]
              Watsen, K., "NETCONF Client and Server Models", draft-
              ietf-netconf-netconf-client-server-08 (work in progress),
              October 2018.

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







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   [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>.

   [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>.


































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Appendix A.  Change Log

A.1.  00 to 01

   o  Renamed "keychain" to "keystore".

A.2.  01 to 02

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

   o  Updated the ietf-restconf-server module to accomodate new grouping
      'ietf-tls-server-grouping'.

A.3.  02 to 03

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

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

A.4.  03 to 04

   o  Added RFC 8174 to Requirements Language Section.

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

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

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

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

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

A.5.  04 to 05

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

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







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A.6.  05 to 06

   o  Fixed change log missing section issue.

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

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

A.7.  06 to 07

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

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

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

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

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

A.8.  07 to 08

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

A.9.  08 to 09

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

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

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

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

A.10.  09 to 10

   o  Reformatted YANG modules.








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

Author's Address

   Kent Watsen
   Watsen Networks

   EMail: kent+ietf@watsen.net




































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