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


                    NETCONF Client and Server Models
              draft-ietf-netconf-netconf-client-server-10

Abstract

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

Editorial Note (To be removed by RFC Editor)

   This draft contains 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-ssh-client-server

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

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

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




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   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  . . . . . . . . . . . . . . . . . . . . . . . .   4
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   4
   3.  The NETCONF Client Model  . . . . . . . . . . . . . . . . . .   4
     3.1.  Tree Diagram  . . . . . . . . . . . . . . . . . . . . . .   4
     3.2.  Example Usage . . . . . . . . . . . . . . . . . . . . . .  13
     3.3.  YANG Module . . . . . . . . . . . . . . . . . . . . . . .  16
   4.  The NETCONF Server Model  . . . . . . . . . . . . . . . . . .  25
     4.1.  Tree Diagram  . . . . . . . . . . . . . . . . . . . . . .  25
     4.2.  Example Usage . . . . . . . . . . . . . . . . . . . . . .  34
     4.3.  YANG Module . . . . . . . . . . . . . . . . . . . . . . .  39
   5.  Design Considerations . . . . . . . . . . . . . . . . . . . .  49
     5.1.  Support all NETCONF transports  . . . . . . . . . . . . .  50
     5.2.  Enable each transport to select which keys to use . . . .  50
     5.3.  Support authenticating NETCONF clients certificates . . .  50
     5.4.  Support mapping authenticated NETCONF client certificates
           to usernames  . . . . . . . . . . . . . . . . . . . . . .  50
     5.5.  Support both listening for connections and call home  . .  50
     5.6.  For Call Home connections . . . . . . . . . . . . . . . .  51
       5.6.1.  Support more than one NETCONF client  . . . . . . . .  51
       5.6.2.  Support NETCONF clients having more than one endpoint  51
       5.6.3.  Support a reconnection strategy . . . . . . . . . . .  51
       5.6.4.  Support both persistent and periodic connections  . .  51
       5.6.5.  Reconnection strategy for periodic connections  . . .  51
       5.6.6.  Keep-alives for persistent connections  . . . . . . .  52
       5.6.7.  Customizations for periodic connections . . . . . . .  52
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .  52
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  53
     7.1.  The IETF XML Registry . . . . . . . . . . . . . . . . . .  53
     7.2.  The YANG Module Names Registry  . . . . . . . . . . . . .  53
   8.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  54
     8.1.  Normative References  . . . . . . . . . . . . . . . . . .  54
     8.2.  Informative References  . . . . . . . . . . . . . . . . .  55
   Appendix A.  Change Log . . . . . . . . . . . . . . . . . . . . .  56
     A.1.  00 to 01  . . . . . . . . . . . . . . . . . . . . . . . .  56
     A.2.  01 to 02  . . . . . . . . . . . . . . . . . . . . . . . .  56
     A.3.  02 to 03  . . . . . . . . . . . . . . . . . . . . . . . .  56
     A.4.  03 to 04  . . . . . . . . . . . . . . . . . . . . . . . .  56
     A.5.  04 to 05  . . . . . . . . . . . . . . . . . . . . . . . .  56
     A.6.  05 to 06  . . . . . . . . . . . . . . . . . . . . . . . .  57
     A.7.  06 to 07  . . . . . . . . . . . . . . . . . . . . . . . .  57
     A.8.  07 to 08  . . . . . . . . . . . . . . . . . . . . . . . .  57
   Appendix B.  08 to 09 . . . . . . . . . . . . . . . . . . . . . .  57
   Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . . .  57
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .  58





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1.  Introduction

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

2.  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.

3.  The NETCONF Client Model

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

   This model supports both the SSH and TLS transport protocols, using
   the SSH client and TLS client groupings defined in
   [I-D.ietf-netconf-ssh-client-server] and
   [I-D.ietf-netconf-tls-client-server] respectively.

   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 NETCONF client supports.

3.1.  Tree Diagram

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

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

   module: ietf-netconf-client
     +--rw netconf-client
        +--rw initiate! {initiate}?
        |  +--rw netconf-server* [name]
        |     +--rw name                  string
        |     +--rw endpoints



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        |     |  +--rw endpoint* [name]
        |     |     +--rw name         string
        |     |     +--rw (transport)
        |     |        +--:(ssh) {ssh-initiate}?
        |     |        |  +--rw ssh
        |     |        |     +--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
        |     |        |     |  +--rw probe-interval?   uint16
        |     |        |     +--rw ssh-client-identity
        |     |        |     |  +--rw username?            string
        |     |        |     |  +--rw (auth-type)
        |     |        |     |     +--:(password)
        |     |        |     |     |  +--rw password?      string
        |     |        |     |     +--:(public-key)
        |     |        |     |     |  +--rw public-key
        |     |        |     |     |     +--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



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        |     |        |     |     |        |           +---w public-ke\
   \y?
        |     |        |     |     |        |           |       binary
        |     |        |     |     |        |           +---w private-k\
   \ey?
        |     |        |     |     |        |                   binary
        |     |        |     |     |        +--:(keystore)
        |     |        |     |     |                 {keystore-supporte\
   \d}?
        |     |        |     |     |           +--rw keystore-reference?
        |     |        |     |     |                   ks:asymmetric-ke\
   \y-ref
        |     |        |     |     +--:(certificate)
        |     |        |     |        +--rw certificate
        |     |        |     |                {sshcmn:ssh-x509-certs}?
        |     |        |     |           +--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



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        |     |        |     |              |     +---n certificate-exp\
   \iration
        |     |        |     |              |        +-- expiration-date
        |     |        |     |              |                yang:date-\
   \and-time
        |     |        |     |              +--:(keystore)
        |     |        |     |                       {keystore-supporte\
   \d}?
        |     |        |     |                 +--rw keystore-reference?
        |     |        |     |                         ks:asymmetric-ke\
   \y-certificate-ref
        |     |        |     +--rw ssh-server-auth
        |     |        |     |  +--rw pinned-ssh-host-keys?
        |     |        |     |  |       ta:pinned-host-keys-ref
        |     |        |     |  |       {ta:ssh-host-keys}?
        |     |        |     |  +--rw pinned-ca-certs?
        |     |        |     |  |       ta:pinned-certificates-ref
        |     |        |     |  |       {sshcmn:ssh-x509-certs,ta:x509-\
   \certificates}?
        |     |        |     |  +--rw pinned-server-certs?
        |     |        |     |          ta:pinned-certificates-ref
        |     |        |     |          {sshcmn:ssh-x509-certs,ta:x509-\
   \certificates}?
        |     |        |     +--rw ssh-transport-params
        |     |        |     |       {ssh-client-transport-params-confi\
   \g}?
        |     |        |     |  +--rw host-key
        |     |        |     |  |  +--rw host-key-alg*   identityref
        |     |        |     |  +--rw key-exchange
        |     |        |     |  |  +--rw key-exchange-alg*   identityref
        |     |        |     |  +--rw encryption
        |     |        |     |  |  +--rw encryption-alg*   identityref
        |     |        |     |  +--rw mac
        |     |        |     |     +--rw mac-alg*   identityref
        |     |        |     +--rw ssh-keepalives {ssh-client-keepalive\
   \s}?
        |     |        |        +--rw max-wait?       uint16
        |     |        |        +--rw max-attempts?   uint8
        |     |        +--:(tls) {tls-initiate}?
        |     |           +--rw tls
        |     |              +--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-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\



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   \d}?
        |     |              |                 +--rw keystore-reference?
        |     |              |                         ks:asymmetric-ke\
   \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 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)
                 +--:(ssh) {ssh-listen}?
                 |  +--rw ssh
                 |     +--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 ssh-client-identity
                 |     |  +--rw username?            string



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                 |     |  +--rw (auth-type)
                 |     |     +--:(password)
                 |     |     |  +--rw password?      string
                 |     |     +--:(public-key)
                 |     |     |  +--rw public-key
                 |     |     |     +--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
                 |     |     |        |           +---w algorithm
                 |     |     |        |           |       asymmetric-ke\
   \y-algorithm-ref
                 |     |     |        |           +---w public-key?
                 |     |     |        |           |       binary
                 |     |     |        |           +---w private-key?
                 |     |     |        |                   binary
                 |     |     |        +--:(keystore) {keystore-supporte\
   \d}?
                 |     |     |           +--rw keystore-reference?
                 |     |     |                   ks:asymmetric-key-ref
                 |     |     +--:(certificate)
                 |     |        +--rw certificate {sshcmn:ssh-x509-cert\
   \s}?
                 |     |           +--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



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                 |     |              |     +---x generate-hidden-key
                 |     |              |     |  +---w input
                 |     |              |     |     +---w algorithm
                 |     |              |     |             asymmetric-ke\
   \y-algorithm-ref
                 |     |              |     +---x install-hidden-key
                 |     |              |     |  +---w input
                 |     |              |     |     +---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 ssh-server-auth
                 |     |  +--rw pinned-ssh-host-keys?
                 |     |  |       ta:pinned-host-keys-ref
                 |     |  |       {ta:ssh-host-keys}?
                 |     |  +--rw pinned-ca-certs?
                 |     |  |       ta:pinned-certificates-ref
                 |     |  |       {sshcmn:ssh-x509-certs,ta:x509-certif\
   \icates}?
                 |     |  +--rw pinned-server-certs?
                 |     |          ta:pinned-certificates-ref
                 |     |          {sshcmn:ssh-x509-certs,ta:x509-certif\
   \icates}?
                 |     +--rw ssh-transport-params
                 |     |       {ssh-client-transport-params-config}?
                 |     |  +--rw host-key
                 |     |  |  +--rw host-key-alg*   identityref
                 |     |  +--rw key-exchange
                 |     |  |  +--rw key-exchange-alg*   identityref
                 |     |  +--rw encryption
                 |     |  |  +--rw encryption-alg*   identityref
                 |     |  +--rw mac
                 |     |     +--rw mac-alg*   identityref
                 |     +--rw ssh-keepalives {ssh-client-keepalives}?



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                 |        +--rw max-wait?       uint16
                 |        +--rw max-attempts?   uint8
                 +--:(tls) {tls-listen}?
                    +--rw tls
                       +--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
                       |              |     |     +---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?



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                       |                         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

3.2.  Example Usage

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

   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) ===========

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

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



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               <ssh-client-identity>
                 <username>foobar</username>
                 <public-key>
                   <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>
                   </local-definition>
                 </public-key>
               </ssh-client-identity>
               <ssh-server-auth>
                 <pinned-ca-certs>explicitly-trusted-server-ca-certs</p\
   \inned-ca-certs>
                 <pinned-server-certs>explicitly-trusted-server-certs</\
   \pinned-server-certs>
               </ssh-server-auth>
               <ssh-keepalives>
                 <max-wait>30</max-wait>
                 <max-attempts>3</max-attempts>
               </ssh-keepalives>
             </ssh>
           </endpoint>
           <endpoint>
             <name>corp-fw2.example.com</name>
             <ssh>
               <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>
               <ssh-client-identity>
                 <username>foobar</username>
                 <public-key>
                   <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>
                   </local-definition>
                 </public-key>
               </ssh-client-identity>
               <ssh-server-auth>
                 <pinned-ca-certs>explicitly-trusted-server-ca-certs</p\
   \inned-ca-certs>
                 <pinned-server-certs>explicitly-trusted-server-certs</\
   \pinned-server-certs>



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               </ssh-server-auth>
               <ssh-keepalives>
                 <max-wait>30</max-wait>
                 <max-attempts>3</max-attempts>
               </ssh-keepalives>
             </ssh>
           </endpoint>
         </endpoints>
         <connection-type>
           <persistent/>
         </connection-type>
         <reconnect-strategy>
           <start-with>last-connected</start-with>
         </reconnect-strategy>
       </netconf-server>
     </initiate>

     <!-- endpoints to listen for NETCONF Call Home connections on -->
     <listen>
       <endpoint>
         <name>Intranet-facing listener</name>
         <ssh>
           <local-address>192.0.2.7</local-address>
           <ssh-client-identity>
             <username>foobar</username>
             <public-key>
               <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>
               </local-definition>
             </public-key>
           </ssh-client-identity>
           <ssh-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>
             <pinned-ssh-host-keys>explicitly-trusted-ssh-host-keys</pi\
   \nned-ssh-host-keys>
           </ssh-server-auth>
         </ssh>
       </endpoint>
     </listen>
   </netconf-client>





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3.3.  YANG Module

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

   <CODE BEGINS> file "ietf-netconf-client@2019-03-09.yang"
   module ietf-netconf-client {
     yang-version 1.1;
     namespace "urn:ietf:params:xml:ns:yang:ietf-netconf-client";
     prefix ncc;

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

     import ietf-tcp-client {
       prefix tcpc;
       reference
         "RFC 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-ssh-client {
       prefix sshc;
       revision-date 2019-03-09; // stable grouping definitions
       reference
         "RFC YYYY: YANG Groupings for SSH Clients and SSH Servers";
     }

     import ietf-tls-client {
       prefix tlsc;
       revision-date 2019-03-09; // stable grouping definitions
       reference
         "RFC ZZZZ: YANG Groupings for TLS Clients and TLS 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 NETCONF 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: NETCONF Client and Server Models";
     }

     // Features

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

     feature ssh-initiate {
       description
         "The 'ssh-initiate' feature indicates that the NETCONF client



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          supports initiating SSH connections to NETCONF servers.";
       reference
         "RFC 6242:
            Using the NETCONF Protocol over Secure Shell (SSH)";
     }

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

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

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

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

     // Groupings

     grouping netconf-client-grouping {
       description
         "Top-level grouping for NETCONF client configuration.";
       container initiate {
         if-feature "initiate";



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         presence "Enables client to initiate TCP connections";
         description
           "Configures client initiating underlying TCP connections.";
         list netconf-server {
           key "name";
           min-elements 1;
           description
             "List of NETCONF servers the NETCONF client is to
              initiate connections to in parallel.";
           leaf name {
             type string;
             description
               "An arbitrary name for the NETCONF server.";
           }
           container endpoints {
             description
               "Container for the list of endpoints.";
             list endpoint {
               key "name";
               min-elements 1;
               ordered-by user;
               description
                 "A user-ordered list of endpoints that the NETCONF
                  client will attempt to connect to in the specified
                  sequence.  Defining more than one enables
                  high-availability.";
               leaf name {
                 type string;
                 description
                   "An arbitrary name for the endpoint.";
               }
               choice transport {
                 mandatory true;
                 description
                   "Selects between available transports.";
                 case ssh {
                   if-feature "ssh-initiate";
                   container ssh {
                     description
                       "Specifies IP and SSH specific configuration
                        for the connection.";
                     uses tcpc:tcp-client-grouping {
                       refine "remote-port" {
                         default "830";
                         description
                           "The NETCONF client will attempt to connect
                            to the IANA-assigned well-known port value
                            for 'netconf-ssh' (443) if no value is



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                            specified.";
                       }
                     }
                     uses sshc:ssh-client-grouping;
                   }
                 }
                 case tls {
                   if-feature "tls-initiate";
                   container tls {
                     description
                       "Specifies IP and TLS specific configuration
                        for the connection.";
                     uses tcpc:tcp-client-grouping {
                       refine "remote-port" {
                         default "6513";
                         description
                           "The NETCONF client will attempt to connect
                            to the IANA-assigned well-known port value
                            for 'netconf-tls' (6513) if no value is
                            specified.";
                       }
                     }
                     uses tlsc:tls-client-grouping {
                       refine "tls-client-identity/auth-type" {
                         mandatory true;
                         description
                           "NETCONF/TLS clients MUST pass some
                            authentication credentials.";
                       }
                     }
                   }
                 }
               } // choice transport
             } // list endpoint
           } // container endpoints

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



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                   description
                     "Maintain a persistent connection to the NETCONF
                      server. If the connection goes down, immediately
                      start trying to reconnect to it, using the
                      reconnection strategy.

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

                      This connection type increases resource
                      utilization, albeit with increased delay in
                      NETCONF server to NETCONF 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;



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



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

       container listen {
         if-feature "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 a NETCONF
              session may remain idle. A NETCONF session will be
              dropped if it is idle for an interval longer than this
              number of seconds.  If set to zero, then the server
              will never drop a session because it is idle.  Sessions
              that have a notification subscription active are never
              dropped.";
         }
         list endpoint {
           key "name";
           min-elements 1;
           description
             "List of endpoints to listen for NETCONF connections.";
           leaf name {
             type string;
             description
               "An arbitrary name for the NETCONF listen endpoint.";
           }
           choice transport {
             mandatory true;
             description



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               "Selects between available transports.";
             case ssh {
               if-feature "ssh-listen";
               container ssh {
                 description
                   "SSH-specific listening configuration for inbound
                    connections.";
                 uses tcps:tcp-server-grouping {
                   refine "local-port" {
                     default "4334";
                     description
                       "The NETCONF client will listen on the IANA-
                        assigned well-known port for 'netconf-ch-ssh'
                        (4334) if no value is specified.";
                   }
                 }
                 uses sshc:ssh-client-grouping;
               }
             }
             case tls {
               if-feature "tls-listen";
               container tls {
                 description
                   "TLS-specific listening configuration for inbound
                    connections.";
                 uses tcps:tcp-server-grouping {
                   refine "local-port" {
                     default "4334";
                     description
                       "The NETCONF client will listen on the IANA-
                        assigned well-known port for 'netconf-ch-ssh'
                        (4334) if no value is specified.";
                   }
                 }
                 uses tlsc:tls-client-grouping {
                   refine "tls-client-identity/auth-type" {
                     mandatory true;
                     description
                       "NETCONF/TLS clients MUST pass some
                        authentication credentials.";
                   }
                 }
               }
             }
           } // transport
         } // endpoint
       } // listen
     } // netconf-client



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

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

4.  The NETCONF Server Model

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

   This model supports both the SSH and TLS transport protocols, using
   the SSH server and TLS server groupings defined in
   [I-D.ietf-netconf-ssh-client-server] and
   [I-D.ietf-netconf-tls-client-server] respectively.

   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 NETCONF server supports.

4.1.  Tree Diagram

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

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

   module: ietf-netconf-server
     +--rw netconf-server
        +--rw listen! {listen}?
        |  +--rw idle-timeout?   uint16
        |  +--rw endpoint* [name]
        |     +--rw name         string
        |     +--rw (transport)
        |        +--:(ssh) {ssh-listen}?
        |        |  +--rw ssh
        |        |     +--rw local-address           inet:ip-address
        |        |     +--rw local-port?             inet:port-number



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        |        |     +--rw tcp-keepalives {tcp-server-keepalives}?
        |        |     |  +--rw idle-time?        uint16
        |        |     |  +--rw max-probes?       uint16
        |        |     |  +--rw probe-interval?   uint16
        |        |     +--rw ssh-server-identity
        |        |     |  +--rw host-key* [name]
        |        |     |     +--rw name                 string
        |        |     |     +--rw (host-key-type)
        |        |     |        +--:(public-key)
        |        |     |        |  +--rw public-key
        |        |     |        |     +--rw (local-or-keystore)
        |        |     |        |        +--:(local)
        |        |     |        |        |        {local-keys-supported\
   \}?
        |        |     |        |        |  +--rw local-definition
        |        |     |        |        |     +--rw algorithm?
        |        |     |        |        |     |       asymmetric-key-a\
   \lgorithm-ref
        |        |     |        |        |     +--rw public-key?
        |        |     |        |        |     |       binary
        |        |     |        |        |     +--rw private-key?
        |        |     |        |        |     |       union
        |        |     |        |        |     +---x generate-hidden-key
        |        |     |        |        |     |  +---w input
        |        |     |        |        |     |     +---w algorithm
        |        |     |        |        |     |             asymmetric\
   \-key-algorithm-ref
        |        |     |        |        |     +---x install-hidden-key
        |        |     |        |        |        +---w input
        |        |     |        |        |           +---w algorithm
        |        |     |        |        |           |       asymmetric\
   \-key-algorithm-ref
        |        |     |        |        |           +---w public-key?
        |        |     |        |        |           |       binary
        |        |     |        |        |           +---w private-key?
        |        |     |        |        |                   binary
        |        |     |        |        +--:(keystore)
        |        |     |        |                 {keystore-supported}?
        |        |     |        |           +--rw keystore-reference?
        |        |     |        |                   ks:asymmetric-key-r\
   \ef
        |        |     |        +--:(certificate)
        |        |     |           +--rw certificate
        |        |     |                   {sshcmn:ssh-x509-certs}?
        |        |     |              +--rw (local-or-keystore)
        |        |     |                 +--:(local)
        |        |     |                 |        {local-keys-supported\
   \}?



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        |        |     |                 |  +--rw local-definition
        |        |     |                 |     +--rw algorithm?
        |        |     |                 |     |       asymmetric-key-a\
   \lgorithm-ref
        |        |     |                 |     +--rw public-key?
        |        |     |                 |     |       binary
        |        |     |                 |     +--rw private-key?
        |        |     |                 |     |       union
        |        |     |                 |     +---x generate-hidden-key
        |        |     |                 |     |  +---w input
        |        |     |                 |     |     +---w algorithm
        |        |     |                 |     |             asymmetric\
   \-key-algorithm-ref
        |        |     |                 |     +---x install-hidden-key
        |        |     |                 |     |  +---w input
        |        |     |                 |     |     +---w algorithm
        |        |     |                 |     |     |       asymmetric\
   \-key-algorithm-ref
        |        |     |                 |     |     +---w public-key?
        |        |     |                 |     |     |       binary
        |        |     |                 |     |     +---w private-key?
        |        |     |                 |     |             binary
        |        |     |                 |     +--rw cert?
        |        |     |                 |     |       end-entity-cert-\
   \cms
        |        |     |                 |     +---n certificate-expira\
   \tion
        |        |     |                 |        +-- expiration-date
        |        |     |                 |                yang:date-and\
   \-time
        |        |     |                 +--:(keystore)
        |        |     |                          {keystore-supported}?
        |        |     |                    +--rw keystore-reference?
        |        |     |                            ks:asymmetric-key-c\
   \ertificate-ref
        |        |     +--rw ssh-client-cert-auth {sshcmn:ssh-x509-cert\
   \s}?
        |        |     |  +--rw pinned-ca-certs?
        |        |     |  |       ta:pinned-certificates-ref
        |        |     |  |       {ta:x509-certificates}?
        |        |     |  +--rw pinned-client-certs?
        |        |     |          ta:pinned-certificates-ref
        |        |     |          {ta:x509-certificates}?
        |        |     +--rw ssh-transport-params
        |        |     |       {ssh-server-transport-params-config}?
        |        |     |  +--rw host-key
        |        |     |  |  +--rw host-key-alg*   identityref
        |        |     |  +--rw key-exchange



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        |        |     |  |  +--rw key-exchange-alg*   identityref
        |        |     |  +--rw encryption
        |        |     |  |  +--rw encryption-alg*   identityref
        |        |     |  +--rw mac
        |        |     |     +--rw mac-alg*   identityref
        |        |     +--rw ssh-keepalives {ssh-server-keepalives}?
        |        |        +--rw max-wait?       uint16
        |        |        +--rw max-attempts?   uint8
        |        +--:(tls) {tls-listen}?
        |           +--rw tls
        |              +--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
        |              |     |                yang:date-and-time
        |              |     +--:(keystore) {keystore-supported}?
        |              |        +--rw keystore-reference?
        |              |                ks:asymmetric-key-certificate-r\
   \ef
        |              +--rw tls-client-auth
        |              |  +--rw pinned-ca-certs?



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        |              |  |       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 call-home! {call-home}?
           +--rw netconf-client* [name]
              +--rw name                  string
              +--rw endpoints
              |  +--rw endpoint* [name]
              |     +--rw name         string
              |     +--rw (transport)
              |        +--:(ssh) {ssh-call-home}?
              |        |  +--rw ssh
              |        |     +--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
              |        |     |  +--rw probe-interval?   uint16
              |        |     +--rw ssh-server-identity
              |        |     |  +--rw host-key* [name]
              |        |     |     +--rw name                 string
              |        |     |     +--rw (host-key-type)
              |        |     |        +--:(public-key)
              |        |     |        |  +--rw public-key



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              |        |     |        |     +--rw (local-or-keystore)
              |        |     |        |        +--:(local)
              |        |     |        |        |        {local-keys-sup\
   \ported}?
              |        |     |        |        |  +--rw local-definition
              |        |     |        |        |     +--rw algorithm?
              |        |     |        |        |     |       asymmetric\
   \-key-algorithm-ref
              |        |     |        |        |     +--rw public-key?
              |        |     |        |        |     |       binary
              |        |     |        |        |     +--rw private-key?
              |        |     |        |        |     |       union
              |        |     |        |        |     +---x generate-hid\
   \den-key
              |        |     |        |        |     |  +---w input
              |        |     |        |        |     |     +---w algori\
   \thm
              |        |     |        |        |     |             asym\
   \metric-key-algorithm-ref
              |        |     |        |        |     +---x install-hidd\
   \en-key
              |        |     |        |        |        +---w input
              |        |     |        |        |           +---w algori\
   \thm
              |        |     |        |        |           |       asym\
   \metric-key-algorithm-ref
              |        |     |        |        |           +---w public\
   \-key?
              |        |     |        |        |           |       bina\
   \ry
              |        |     |        |        |           +---w privat\
   \e-key?
              |        |     |        |        |                   bina\
   \ry
              |        |     |        |        +--:(keystore)
              |        |     |        |                 {keystore-suppo\
   \rted}?
              |        |     |        |           +--rw keystore-refere\
   \nce?
              |        |     |        |                   ks:asymmetric\
   \-key-ref
              |        |     |        +--:(certificate)
              |        |     |           +--rw certificate
              |        |     |                   {sshcmn:ssh-x509-certs\
   \}?
              |        |     |              +--rw (local-or-keystore)
              |        |     |                 +--:(local)
              |        |     |                 |        {local-keys-sup\



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   \ported}?
              |        |     |                 |  +--rw local-definition
              |        |     |                 |     +--rw algorithm?
              |        |     |                 |     |       asymmetric\
   \-key-algorithm-ref
              |        |     |                 |     +--rw public-key?
              |        |     |                 |     |       binary
              |        |     |                 |     +--rw private-key?
              |        |     |                 |     |       union
              |        |     |                 |     +---x generate-hid\
   \den-key
              |        |     |                 |     |  +---w input
              |        |     |                 |     |     +---w algori\
   \thm
              |        |     |                 |     |             asym\
   \metric-key-algorithm-ref
              |        |     |                 |     +---x install-hidd\
   \en-key
              |        |     |                 |     |  +---w input
              |        |     |                 |     |     +---w algori\
   \thm
              |        |     |                 |     |     |       asym\
   \metric-key-algorithm-ref
              |        |     |                 |     |     +---w public\
   \-key?
              |        |     |                 |     |     |       bina\
   \ry
              |        |     |                 |     |     +---w privat\
   \e-key?
              |        |     |                 |     |             bina\
   \ry
              |        |     |                 |     +--rw cert?
              |        |     |                 |     |       end-entity\
   \-cert-cms
              |        |     |                 |     +---n certificate-\
   \expiration
              |        |     |                 |        +-- expiration-\
   \date
              |        |     |                 |                yang:da\
   \te-and-time
              |        |     |                 +--:(keystore)
              |        |     |                          {keystore-suppo\
   \rted}?
              |        |     |                    +--rw keystore-refere\
   \nce?
              |        |     |                            ks:asymmetric\
   \-key-certificate-ref
              |        |     +--rw ssh-client-cert-auth



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              |        |     |       {sshcmn:ssh-x509-certs}?
              |        |     |  +--rw pinned-ca-certs?
              |        |     |  |       ta:pinned-certificates-ref
              |        |     |  |       {ta:x509-certificates}?
              |        |     |  +--rw pinned-client-certs?
              |        |     |          ta:pinned-certificates-ref
              |        |     |          {ta:x509-certificates}?
              |        |     +--rw ssh-transport-params
              |        |     |       {ssh-server-transport-params-confi\
   \g}?
              |        |     |  +--rw host-key
              |        |     |  |  +--rw host-key-alg*   identityref
              |        |     |  +--rw key-exchange
              |        |     |  |  +--rw key-exchange-alg*   identityref
              |        |     |  +--rw encryption
              |        |     |  |  +--rw encryption-alg*   identityref
              |        |     |  +--rw mac
              |        |     |     +--rw mac-alg*   identityref
              |        |     +--rw ssh-keepalives {ssh-server-keepalive\
   \s}?
              |        |        +--rw max-wait?       uint16
              |        |        +--rw max-attempts?   uint8
              |        +--:(tls) {tls-call-home}?
              |           +--rw tls
              |              +--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\
   \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



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              |              |     |     |  +---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
              |              |        +--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 connection-type
              |  +--rw (connection-type)



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              |     +--:(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

4.2.  Example Usage

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

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

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

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

     <!-- endpoints to listen for NETCONF connections on -->
     <listen>
       <endpoint> <!-- listening for SSH connections -->
         <name>netconf/ssh</name>
         <ssh>
           <local-address>192.0.2.7</local-address>
           <ssh-server-identity>
             <host-key>
               <name>deployment-specific-certificate</name>
               <public-key>
                 <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>
                 </local-definition>
               </public-key>
             </host-key>
           </ssh-server-identity>
           <ssh-client-cert-auth>
             <pinned-ca-certs>explicitly-trusted-client-ca-certs</pinne\



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   \d-ca-certs>
             <pinned-client-certs>explicitly-trusted-client-certs</pinn\
   \ed-client-certs>
           </ssh-client-cert-auth>
         </ssh>
       </endpoint>
       <endpoint> <!-- listening for TLS sessions -->
         <name>netconf/tls</name>
         <tls>
           <local-address>192.0.2.7</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>
         </tls>
       </endpoint>
     </listen>

     <!-- calling home to SSH and TLS based NETCONF clients -->
     <call-home>
       <netconf-client> <!-- SSH-based client -->
         <name>config-mgr</name>
         <endpoints>
           <endpoint>



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             <name>east-data-center</name>
             <ssh>
               <remote-address>east.config-mgr.example.com</remote-addr\
   \ess>
               <ssh-server-identity>
                 <host-key>
                   <name>deployment-specific-certificate</name>
                   <public-key>
                     <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>
                     </local-definition>
                   </public-key>
                 </host-key>
               </ssh-server-identity>
               <ssh-client-cert-auth>
                 <pinned-ca-certs>explicitly-trusted-client-ca-certs</p\
   \inned-ca-certs>
                 <pinned-client-certs>explicitly-trusted-client-certs</\
   \pinned-client-certs>
               </ssh-client-cert-auth>
             </ssh>
           </endpoint>
           <endpoint>
             <name>west-data-center</name>
             <ssh>
               <remote-address>west.config-mgr.example.com</remote-addr\
   \ess>
               <ssh-server-identity>
                 <host-key>
                   <name>deployment-specific-certificate</name>
                   <public-key>
                     <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>
                     </local-definition>
                   </public-key>
                 </host-key>
               </ssh-server-identity>
               <ssh-client-cert-auth>
                 <pinned-ca-certs>explicitly-trusted-client-ca-certs</p\
   \inned-ca-certs>
                 <pinned-client-certs>explicitly-trusted-client-certs</\
   \pinned-client-certs>



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               </ssh-client-cert-auth>
             </ssh>
           </endpoint>
         </endpoints>
         <connection-type>
           <periodic>
             <idle-timeout>300</idle-timeout>
             <period>60</period>
           </periodic>
         </connection-type>
         <reconnect-strategy>
           <start-with>last-connected</start-with>
           <max-attempts>3</max-attempts>
         </reconnect-strategy>
       </netconf-client>
       <netconf-client> <!-- TLS-based client -->
         <name>data-collector</name>
         <endpoints>
           <endpoint>
             <name>east-data-center</name>
             <tls>
               <remote-address>east.analytics.example.com</remote-addre\
   \ss>
               <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>
                 <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>



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                   </cert-to-name>
                 </cert-maps>
               </tls-client-auth>
               <tcp-keepalives>
                 <idle-time>15</idle-time>
                 <max-probes>3</max-probes>
                 <probe-interval>30</probe-interval>
               </tcp-keepalives>
               <tls-keepalives>
                 <max-wait>30</max-wait>
                 <max-attempts>3</max-attempts>
               </tls-keepalives>
             </tls>
           </endpoint>
           <endpoint>
             <name>west-data-center</name>
             <tls>
               <remote-address>west.analytics.example.com</remote-addre\
   \ss>
               <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>
                 <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>
               <tcp-keepalives>



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                 <idle-time>15</idle-time>
                 <max-probes>3</max-probes>
                 <probe-interval>30</probe-interval>
               </tcp-keepalives>
               <tls-keepalives>
                 <max-wait>30</max-wait>
                 <max-attempts>3</max-attempts>
               </tls-keepalives>
             </tls>
           </endpoint>
         </endpoints>
         <connection-type>
           <persistent/>
         </connection-type>
         <reconnect-strategy>
           <start-with>first-listed</start-with>
           <max-attempts>3</max-attempts>
         </reconnect-strategy>
       </netconf-client>
     </call-home>
   </netconf-server>

4.3.  YANG Module

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

   This YANG module imports YANG types from [RFC6991], and YANG
   groupings from [RFC7407], [I-D.ietf-netconf-ssh-client-server] and
   [I-D.ietf-netconf-ssh-client-server].

   <CODE BEGINS> file "ietf-netconf-server@2019-03-09.yang"
   module ietf-netconf-server {
     yang-version 1.1;
     namespace "urn:ietf:params:xml:ns:yang:ietf-netconf-server";
     prefix ncs;

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

     import ietf-x509-cert-to-name {
       prefix x509c2n;



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       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-ssh-server {
       prefix sshs;
       revision-date 2019-03-09; // stable grouping definitions
       reference
         "RFC YYYY: YANG Groupings for SSH Clients and SSH Servers";
     }

     import ietf-tls-server {
       prefix tlss;
       revision-date 2019-03-09; // stable grouping definitions
       reference
         "RFC ZZZZ: YANG Groupings for TLS Clients and TLS Servers";
     }

     organization
       "IETF NETCONF (Network Configuration) Working Group";
     contact
       "WG Web:   <http://datatracker.ietf.org/wg/netconf/>
        WG List:  <mailto:netconf@ietf.org>
        Author:   Kent Watsen <mailto:kent+ietf@watsen.net>
        Author:   Gary Wu <mailto:garywu@cisco.com>
        Author:   Juergen Schoenwaelder
                  <mailto:j.schoenwaelder@jacobs-university.de>";
     description
       "This module contains a collection of YANG definitions for
        configuring NETCONF 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



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        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: NETCONF Client and Server Models";
     }

     // Features

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

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

     feature tls-listen {
       description
         "The 'tls-listen' feature indicates that the NETCONF server
          supports opening a port to accept NETCONF over TLS
          client connections.";
       reference
         "RFC 7589: Using the NETCONF Protocol over Transport



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                    Layer Security (TLS) with Mutual X.509
                    Authentication";
     }

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

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

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

     // Groupings

     grouping netconf-server-grouping {
       description
         "Top-level grouping for NETCONF server configuration.";
       container listen {
         if-feature "listen";
         presence "Enables server to listen for TCP connections";
         description
           "Configures listen behavior";
         leaf idle-timeout {
           type uint16;
           units "seconds";
           default 3600; // one hour
           description
             "Specifies the maximum number of seconds that a NETCONF



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              session may remain idle. A NETCONF session will be
              dropped if it is idle for an interval longer than this
              number of seconds.  If set to zero, then the server
              will never drop a session because it is idle.  Sessions
              that have a notification subscription active are never
              dropped.";
         }
         list endpoint {
           key "name";
           min-elements 1;
           description
             "List of endpoints to listen for NETCONF connections.";
           leaf name {
             type string;
             description
               "An arbitrary name for the NETCONF listen endpoint.";
           }
           choice transport {
             mandatory true;
             description
               "Selects between available transports.";
             case ssh {
               if-feature "ssh-listen";
               container ssh {
                 description
                   "SSH-specific listening configuration for inbound
                    connections.";
                 uses tcps:tcp-server-grouping {
                   refine "local-port" {
                     default "830";
                     description
                       "The NETCONF server will listen on the IANA-
                        assigned well-known port value for 'netconf-ssh'
                        (830) if no value is specified.";
                   }
                 }
                 uses sshs:ssh-server-grouping;
               }
             }
             case tls {
               if-feature "tls-listen";
               container tls {
                 description
                   "TLS-specific listening configuration for inbound
                    connections.";
                 uses tcps:tcp-server-grouping {
                   refine "local-port" {
                     default "6513";



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                     description
                       "The NETCONF server will listen on the IANA-
                        assigned well-known port value for 'netconf-tls'
                        (6513) if no value is specified.";
                   }
                 }
                 uses tlss:tls-server-grouping {
                   refine "tls-client-auth" {
                     must 'pinned-ca-certs or pinned-client-certs';
                     description
                       "NETCONF/TLS servers MUST validate client
                        certiticates.";
                   }
                   augment "tls-client-auth" {
                     description
                       "Augments in the cert-to-name structure.";
                     container cert-maps {
                       uses x509c2n:cert-to-name;
                       description
                         "The cert-maps container is used by a TLS-
                          based NETCONF server to map the NETCONF
                          client's presented X.509 certificate to a
                          NETCONF username.  If no matching and valid
                          cert-to-name list entry can be found, then
                          the NETCONF server MUST close the connection,
                          and MUST NOT accept NETCONF messages over
                          it.";
                       reference
                         "RFC WWWW: NETCONF over TLS, Section 7";
                     }
                   }
                 }
               }
             }
           }
         }
       }
       container call-home {
         if-feature "call-home";
         presence "Enables server to initiate TCP connections";
         description "Configures call-home behavior";
         list netconf-client {
           key "name";
           min-elements 1;
           description
             "List of NETCONF clients the NETCONF server is to
              initiate call-home connections to in parallel.";
           leaf name {



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             type string;
             description
               "An arbitrary name for the remote NETCONF client.";
           }
           container endpoints {
             description
               "Container for the list of endpoints.";
             list endpoint {
               key "name";
               min-elements 1;
               ordered-by user;
               description
                 "A non-empty user-ordered list of endpoints for this
                  NETCONF server to try to connect to in sequence.
                  Defining more than one enables high-availability.";
               leaf name {
                 type string;
                 description
                   "An arbitrary name for this endpoint.";
               }
               choice transport {
                 mandatory true;
                 description
                   "Selects between available transports.";
                 case ssh {
                   if-feature "ssh-call-home";
                   container ssh {
                     description
                       "Specifies SSH-specific call-home transport
                        configuration.";
                     uses tcpc:tcp-client-grouping {
                       refine "remote-port" {
                         default "4334";
                         description
                           "The NETCONF server will attempt to connect
                            to the IANA-assigned well-known port for
                            'netconf-ch-tls' (4334) if no value is
                            specified.";
                       }
                     }
                     uses sshs:ssh-server-grouping;
                   }
                 }
                 case tls {
                   if-feature "tls-call-home";
                   container tls {
                     description
                       "Specifies TLS-specific call-home transport



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                        configuration.";
                     uses tcpc:tcp-client-grouping {
                       refine "remote-port" {
                         default "4335";
                         description
                           "The NETCONF server will attempt to connect
                            to the IANA-assigned well-known port for
                            'netconf-ch-tls' (4335) if no value is
                            specified.";
                       }
                     }
                     uses tlss:tls-server-grouping {
                       refine "tls-client-auth" {
                         must 'pinned-ca-certs or pinned-client-certs';
                         description
                           "NETCONF/TLS servers MUST validate client
                            certiticates.";
                       }
                       augment "tls-client-auth" {
                         description
                           "Augments in the cert-to-name structure.";
                         container cert-maps {
                           uses x509c2n:cert-to-name;
                           description
                             "The cert-maps container is used by a
                              TLS-based NETCONF server to map the
                              NETCONF client's presented X.509
                              certificate to a NETCONF username.  If
                              no matching and valid cert-to-name list
                              entry can be found, then the NETCONF
                              server MUST close the connection, and
                              MUST NOT accept NETCONF messages over
                              it.";
                           reference
                             "RFC WWWW: NETCONF over TLS, Section 7";
                         }
                       }
                     }
                   }
                 } // tls
               } // choice
             } // endpoint
           } // endpoints
           container connection-type {
             description
               "Indicates the NETCONF server's preference for how the
                NETCONF connection is maintained.";
             choice connection-type {



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

                      This connection type minimizes any NETCONF client
                      to NETCONF server data-transfer delay, albeit at
                      the expense of holding resources longer.";
                 } // container persistent
               } // case persistent-connection
               case periodic-connection {
                 container periodic {
                   presence "Indicates that a periodic connection is
                             to be maintained.";
                   description
                     "Periodically connect to the NETCONF client.  The
                      NETCONF client should close the underlying TLS
                      connection upon completing planned activities.

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



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                        example, for an anchor time is 15 minutes past
                        midnight and a period interval of 24 hours, then
                        a periodic connection will occur 15 minutes past
                        midnight everyday.";
                   }
                   leaf idle-timeout {
                     type uint16;
                     units "seconds";
                     default 120; // two minutes
                     description
                       "Specifies the maximum number of seconds that
                        a NETCONF session may remain idle. A NETCONF
                        session will be dropped if it is idle for an
                        interval longer than this number of seconds.
                        If set to zero, then the server will never
                        drop a session because it is idle.";
                   }
                 } // container periodic
               } // case periodic-connection
             } // choice connection-type
           } // container connection-type
           container reconnect-strategy {
             description
               "The reconnection strategy directs how a NETCONF server
                reconnects to a NETCONF client, after discovering its
                connection to the client has dropped, even if due to a
                reboot.  The NETCONF server starts with the specified
                endpoint and tries to connect to it max-attempts times
                before trying the next endpoint in the list (round
                robin).";
             leaf start-with {
               type enumeration {
                 enum first-listed {
                   description
                     "Indicates that reconnections should start with
                      the first endpoint listed.";
                 }
                 enum last-connected {
                   description
                     "Indicates that reconnections should start with
                      the endpoint last connected to.  If no previous
                      connection has ever been established, then the
                      first endpoint configured is used.   NETCONF
                      servers SHOULD be able to remember the last
                      endpoint connected to across reboots.";
                 }
                 enum random-selection {
                   description



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                     "Indicates that reconnections should start with
                      a random endpoint.";
                 }
               }
               default "first-listed";
               description
                 "Specifies which of the NETCONF client's endpoints
                  the NETCONF server should start with when trying
                  to connect to the NETCONF client.";
             }
             leaf max-attempts {
               type uint8 {
                 range "1..max";
               }
               default "3";
               description
                 "Specifies the number times the NETCONF server tries
                  to connect to a specific endpoint before moving on
                  to the next endpoint in the list (round robin).";
             }
           } // container reconnect-strategy
         } // list netconf-client
       } // container call-home
     } // grouping netconf-server-grouping

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

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

5.  Design Considerations

   Editorial: this section is a hold over from before, previously called
   "Objectives".  It was only written two support the "server" (not the
   "client").  The question is if it's better to add the missing
   "client" parts, or remove this section altogether.

   The primary purpose of the YANG modules defined herein is to enable
   the configuration of the NETCONF client and servers.  This scope
   includes the following objectives:





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5.1.  Support all NETCONF transports

   The YANG module should support all current NETCONF transports, namely
   NETCONF over SSH [RFC6242], NETCONF over TLS [RFC7589], and to be
   extensible to support future transports as necessary.

   Because implementations may not support all transports, the modules
   should use YANG "feature" statements so that implementations can
   accurately advertise which transports are supported.

5.2.  Enable each transport to select which keys to use

   Servers may have a multiplicity of host-keys or server-certificates
   from which subsets may be selected for specific uses.  For instance,
   a NETCONF server may want to use one set of SSH host-keys when
   listening on port 830, and a different set of SSH host-keys when
   calling home.  The data models provided herein should enable
   configuration of which keys to use on a per-use basis.

5.3.  Support authenticating NETCONF clients certificates

   When a certificate is used to authenticate a NETCONF client, there is
   a need to configure the server to know how to authenticate the
   certificates.  The server should be able to authenticate the client's
   certificate either by using path-validation to a configured trust
   anchor or by matching the client-certificate to one previously
   configured.

5.4.  Support mapping authenticated NETCONF client certificates to
      usernames

   When a client certificate is used for TLS client authentication, the
   NETCONF server must be able to derive a username from the
   authenticated certificate.  Thus the modules defined herein should
   enable this mapping to be configured.

5.5.  Support both listening for connections and call home

   The NETCONF protocols were originally defined as having the server
   opening a port to listen for client connections.  More recently the
   NETCONF working group defined support for call-home ([RFC8071]),
   enabling the server to initiate the connection to the client.  Thus
   the modules defined herein should enable configuration for both
   listening for connections and calling home.  Because implementations
   may not support both listening for connections and calling home, YANG
   "feature" statements should be used so that implementation can
   accurately advertise the connection types it supports.




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5.6.  For Call Home connections

   The following objectives only pertain to call home connections.

5.6.1.  Support more than one NETCONF client

   A NETCONF server may be managed by more than one NETCONF client.  For
   instance, a deployment may have one client for provisioning and
   another for fault monitoring.  Therefore, when it is desired for a
   server to initiate call home connections, it should be able to do so
   to more than one client.

5.6.2.  Support NETCONF clients having more than one endpoint

   A NETCONF client managing a NETCONF server may implement a high-
   availability strategy employing a multiplicity of active and/or
   passive endpoint.  Therefore, when it is desired for a server to
   initiate call home connections, it should be able to connect to any
   of the client's endpoints.

5.6.3.  Support a reconnection strategy

   Assuming a NETCONF client has more than one endpoint, then it becomes
   necessary to configure how a NETCONF server should reconnect to the
   client should it lose its connection to one the client's endpoints.
   For instance, the NETCONF server may start with first endpoint
   defined in a user-ordered list of endpoints or with the last
   endpoints it was connected to.

5.6.4.  Support both persistent and periodic connections

   NETCONF clients may vary greatly on how frequently they need to
   interact with a NETCONF server, how responsive interactions need to
   be, and how many simultaneous connections they can support.  Some
   clients may need a persistent connection to servers to optimize real-
   time interactions, while others prefer periodic interactions in order
   to minimize resource requirements.  Therefore, when it is necessary
   for server to initiate connections, it should be configurable if the
   connection is persistent or periodic.

5.6.5.  Reconnection strategy for periodic connections

   The reconnection strategy should apply to both persistent and
   periodic connections.  How it applies to periodic connections becomes
   clear when considering that a periodic "connection" is a logical
   connection to a single server.  That is, the periods of
   unconnectedness are intentional as opposed to due to external
   reasons.  A periodic "connection" should always reconnect to the same



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   server until it is no longer able to, at which time the reconnection
   strategy guides how to connect to another server.

5.6.6.  Keep-alives for persistent connections

   If a persistent connection is desired, it is the responsibility of
   the connection initiator to actively test the "aliveness" of the
   connection.  The connection initiator must immediately work to
   reestablish a persistent connection as soon as the connection is
   lost.  How often the connection should be tested is driven by NETCONF
   client requirements, and therefore keep-alive settings should be
   configurable on a per-client basis.

5.6.7.  Customizations for periodic connections

   If a periodic connection is desired, it is necessary for the NETCONF
   server to know how often it should connect.  This frequency
   determines the maximum amount of time a NETCONF client may have to
   wait to send data to a server.  A server may connect to a client
   before this interval expires if desired (e.g., to send data to a
   client).

6.  Security Considerations

   The YANG module defined in this document uses groupings defined in
   [I-D.ietf-netconf-ssh-client-server] and
   [I-D.ietf-netconf-tls-client-server].  Please see the Security
   Considerations section in those documents for concerns related those
   groupings.

   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:




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      /: 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

7.  IANA Considerations

7.1.  The IETF XML Registry

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

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

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

7.2.  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-netconf-client
      namespace:    urn:ietf:params:xml:ns:yang:ietf-netconf-client
      prefix:       ncc
      reference:    RFC XXXX

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

8.  References

8.1.  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-ssh-client-server]
              Watsen, K., Wu, G., and L. Xia, "YANG Groupings for SSH
              Clients and SSH Servers", draft-ietf-netconf-ssh-client-
              server-08 (work in progress), October 2018.

   [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-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.

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

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

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



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   [RFC6242]  Wasserman, M., "Using the NETCONF Protocol over Secure
              Shell (SSH)", RFC 6242, DOI 10.17487/RFC6242, June 2011,
              <https://www.rfc-editor.org/info/rfc6242>.

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

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

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

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

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

8.2.  Informative References

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

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

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

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

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



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Appendix A.  Change Log

A.1.  00 to 01

   o  Renamed "keychain" to "keystore".

A.2.  01 to 02

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

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

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

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 'netconf-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-netconf-client to add a
      mandatory true.

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

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

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

Appendix B.  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.

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.



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Author's Address

   Kent Watsen
   Watsen Networks

   EMail: kent+ietf@watsen.net













































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