[Docs] [txt|pdf|xml] [Tracker] [WG] [Email] [Diff1] [Diff2] [Nits]

Versions: 00 01 02 03 04 05 06 07 08 09 draft-ietf-netconf-netconf-client-server

NETCONF Working Group                                          K. Watsen
Internet-Draft                                          Juniper Networks
Intended status: Standards Track                        J. Schoenwaelder
Expires: June 14, 2015                          Jacobs University Bremen
                                                       December 11, 2014


        NETCONF Server and RESTCONF Server Configuration Models
                   draft-ietf-netconf-server-model-05

Abstract

   This draft defines a NETCONF server configuration data model and a
   RESTCONF server configuration data model.  These data models enable
   configuration of the NETCONF and RESTCONF services themselves,
   including which transports are supported, what ports the servers
   listens on, whether call-home is supported, and associated
   parameters.

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.  Please note
   that no other RFC Editor instructions are specified anywhere else 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  draft-ietf-netconf-rfc5539bis

   o  draft-ietf-netconf-restconf

   o  draft-ietf-netconf-call-home

   o  draft-ietf-netmod-snmp-cfg

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

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

   o  "WWWW" --> the assigned RFC value for draft-ietf-netconf-
      rfc5539bis




Watsen & Schoenwaelder    Expires June 14, 2015                 [Page 1]


Internet-Draft    NETCONF/RESTCONF Server Config Models    December 2014


   o  "XXXX" --> the assigned RFC value for draft-ietf-netconf-restconf

   o  "YYYY" --> the assigned RFC value for draft-ietf-netconf-call-home

   o  "ZZZZ" --> the assigned RFC value for draft-ietf-netmod-snmp-cfg

   Artwork in this document contains placeholder values for ports
   pending IANA assignment from "draft-ietf-netconf-call-home".  Please
   apply the following replacements:

   o  "7777" --> the assigned port value for "netconf-ch-ssh"

   o  "8888" --> the assigned port value for "netconf-ch-tls"

   o  "9999" --> the assigned port value for "restconf-ch-tls"

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

   o  "2014-12-11" --> the publication date of this draft

   The following two Appendix sections are to be removed prior to
   publication:

   o  Appendix B.  Change Log

   o  Appendix C.  Open Issues

Status of This Memo

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

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

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

   This Internet-Draft will expire on June 14, 2015.







Watsen & Schoenwaelder    Expires June 14, 2015                 [Page 2]


Internet-Draft    NETCONF/RESTCONF Server Config Models    December 2014


Copyright Notice

   Copyright (c) 2014 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

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

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   4
     1.1.  Terminology . . . . . . . . . . . . . . . . . . . . . . .   4
     1.2.  Tree Diagrams . . . . . . . . . . . . . . . . . . . . . .   4
   2.  Objectives  . . . . . . . . . . . . . . . . . . . . . . . . .   5
     2.1.  Support all NETCONF and RESTCONF transports . . . . . . .   5
     2.2.  Enable each transport to select which keys to use . . . .   5
     2.3.  Support authenticating NETCONF clients certificates . . .   5
     2.4.  Support mapping authenticated NETCONF client-certificates
           to usernames  . . . . . . . . . . . . . . . . . . . . . .   6
     2.5.  Support both Listening for connections and Call Home  . .   6
     2.6.  For Call Home connections . . . . . . . . . . . . . . . .   6
       2.6.1.  Support more than one northbound application  . . . .   6
       2.6.2.  Support applications having more than one server  . .   6
       2.6.3.  Support a reconnection strategy . . . . . . . . . . .   6
       2.6.4.  Support both persistent and periodic connections  . .   7
       2.6.5.  Reconnection strategy for periodic connections  . . .   7
       2.6.6.  Keep-alives for persistent connections  . . . . . . .   7
       2.6.7.  Customizations for periodic connections . . . . . . .   7
   3.  The NETCONF Server Configuration Model  . . . . . . . . . . .   8
     3.1.  Overview  . . . . . . . . . . . . . . . . . . . . . . . .   8
       3.1.1.  The "session-options" subtree . . . . . . . . . . . .   8
       3.1.2.  The "listen" subtree  . . . . . . . . . . . . . . . .   8
       3.1.3.  The "call-home" subtree . . . . . . . . . . . . . . .   9
       3.1.4.  The "ssh" subtree . . . . . . . . . . . . . . . . . .  11
       3.1.5.  The "tls" subtree . . . . . . . . . . . . . . . . . .  11
     3.2.  YANG Module . . . . . . . . . . . . . . . . . . . . . . .  12
   4.  The RESTCONF Server Configuration Model . . . . . . . . . . .  25
     4.1.  Overview  . . . . . . . . . . . . . . . . . . . . . . . .  25
       4.1.1.  The "listen" subtree  . . . . . . . . . . . . . . . .  25
       4.1.2.  The "call-home" subtree . . . . . . . . . . . . . . .  26
     4.2.  YANG Module . . . . . . . . . . . . . . . . . . . . . . .  28



Watsen & Schoenwaelder    Expires June 14, 2015                 [Page 3]


Internet-Draft    NETCONF/RESTCONF Server Config Models    December 2014


   5.  Implementation strategy for keep-alives . . . . . . . . . . .  36
     5.1.  Keep-alives for SSH . . . . . . . . . . . . . . . . . . .  37
     5.2.  Keep-alives for TLS . . . . . . . . . . . . . . . . . . .  37
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .  37
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  38
   8.  Other Considerations  . . . . . . . . . . . . . . . . . . . .  39
   9.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  39
   10. References  . . . . . . . . . . . . . . . . . . . . . . . . .  39
     10.1.  Normative References . . . . . . . . . . . . . . . . . .  39
     10.2.  Informative References . . . . . . . . . . . . . . . . .  40
   Appendix A.  Examples . . . . . . . . . . . . . . . . . . . . . .  41
     A.1.  NETCONF Configuration using SSH Transport . . . . . . . .  41
     A.2.  NETCONF Configuration using TLS Transport . . . . . . . .  42
     A.3.  RESTCONF Configuration using TLS Transport  . . . . . . .  44
   Appendix B.  Change Log . . . . . . . . . . . . . . . . . . . . .  44
     B.1.  00 to 01  . . . . . . . . . . . . . . . . . . . . . . . .  44
     B.2.  01 to 02  . . . . . . . . . . . . . . . . . . . . . . . .  45
     B.3.  02 to 03  . . . . . . . . . . . . . . . . . . . . . . . .  45
     B.4.  03 to 04  . . . . . . . . . . . . . . . . . . . . . . . .  45
     B.5.  04 to 05  . . . . . . . . . . . . . . . . . . . . . . . .  45
   Appendix C.  Open Issues  . . . . . . . . . . . . . . . . . . . .  46

1.  Introduction

   This draft defines a NETCONF [RFC6241] server configuration data
   model and a RESTCONF [draft-ietf-netconf-restconf] server
   configuration data model.  These data models enable configuration of
   the NETCONF and RESTCONF services themselves, including which
   transports are supported, what ports the servers listens on, whether
   call-home is supported, and associated parameters.

1.1.  Terminology

   The keywords "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in RFC 2119 [RFC2119].

1.2.  Tree Diagrams

   A simplified graphical representation of the data models is used in
   this document.  The meaning of the symbols in these diagrams is as
   follows:

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

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




Watsen & Schoenwaelder    Expires June 14, 2015                 [Page 4]


Internet-Draft    NETCONF/RESTCONF Server Config Models    December 2014


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

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

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

2.  Objectives

   The primary purpose of the YANG modules defined herein is to enable
   the configuration of the NETCONF and RESTCONF services on a network
   element.  This scope includes the following objectives:

2.1.  Support all NETCONF and RESTCONF transports

   The YANG module should support all current NETCONF and RESTCONF
   transports, namely NETCONF over SSH [RFC6242], NETCONF over TLS
   [draft-ietf-netconf-rfc5539bis], and RESTCONF over TLS
   [draft-ietf-netconf-restconf], and to be extensible to support future
   transports as necessary.

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

2.2.  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.

2.3.  Support authenticating NETCONF clients certificates

   When a certificate is used to authenticate a NETCONF client, either
   when using the TLS transport or the SSH transport with X.509
   certificates [RFC6187], there is a need to configure the server to
   know how to authenticate the certificates.  The server should be able
   to do this either by using path-validation to a configured trust
   anchor or by matching the client-certificate to one previously
   configured.






Watsen & Schoenwaelder    Expires June 14, 2015                 [Page 5]


Internet-Draft    NETCONF/RESTCONF Server Config Models    December 2014


2.4.  Support mapping authenticated NETCONF client-certificates to
      usernames

   Some NETCONF transports (e.g., TLS) need additional support to map
   authenticated transport-level sessions to a NETCONF username.  The
   NETCONF server model defined herein should define an ability for this
   mapping to be configured."

2.5.  Support both Listening for connections and Call Home

   The NETCONF and RESTCONF 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
   ([draft-ietf-netconf-call-home]), enabling the server to initiate the
   connection to the client, for both the NETCONF and RESTCONF
   protocols.  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.

2.6.  For Call Home connections

   The following objectives only pertain to call home connections.

2.6.1.  Support more than one northbound application

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

2.6.2.  Support applications having more than one server

   An application managing a device may implement a high-availability
   strategy employing a multiplicity of active and/or passive servers.
   Therefore, when it is desired for a device to initiate call home
   connections, it should be able to connect to any of the application's
   servers.

2.6.3.  Support a reconnection strategy

   Assuming an application has more than one server, then it becomes
   necessary to configure how a device should reconnect to the
   application should it lose its connection to the application's
   servers.  Of primary interest is if the device should start with



Watsen & Schoenwaelder    Expires June 14, 2015                 [Page 6]


Internet-Draft    NETCONF/RESTCONF Server Config Models    December 2014


   first server defined in a user-ordered list of servers or with the
   last server it was connected to.  Secondary settings might specify
   the frequency of attempts and number of attempts per server.
   Therefore, a reconnection strategy should be configurable.

2.6.4.  Support both persistent and periodic connections

   Applications may vary greatly on how frequently they need to interact
   with a device, how responsive interactions with devices need to be,
   and how many simultaneous connections they can support.  Some
   applications may need a persistent connection to devices to optimize
   real-time interactions, while others prefer periodic interactions in
   order to minimize resource requirements.  Therefore, when it is
   necessary for devices to initiate connections, the type of connection
   desired should be configurable.

2.6.5.  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
   server until it is no longer able to, at which time the reconnection
   strategy guides how to connect to another server.

2.6.6.  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
   application requirements, and therefore keep-alive settings should be
   configurable on a per-application basis.

2.6.7.  Customizations for periodic connections

   If a periodic connection is desired, it is necessary for the device
   to know how often it should connect.  This delay essentially
   determines how long the application might have to wait to send data
   to the device.  This setting does not constrain how often the device
   must wait to send data to the application, as the device should
   immediately connect to the application whenever it has data to send
   to it.





Watsen & Schoenwaelder    Expires June 14, 2015                 [Page 7]


Internet-Draft    NETCONF/RESTCONF Server Config Models    December 2014


   A common communication pattern is that one data transmission is many
   times closely followed by another.  For instance, if the device needs
   to send a notification message, there's a high probability that it
   will send another shortly thereafter.  Likewise, the application may
   have a sequence of pending messages to send.  Thus, it should be
   possible for a device to hold a connection open until some amount of
   time of no data being transmitted as transpired.

3.  The NETCONF Server Configuration Model

3.1.  Overview

3.1.1.  The "session-options" subtree

   module: ietf-netconf-server
      +--rw netconf-server
         +--rw session-options {session-options}?
            +--rw hello-timeout?   uint32
            +--rw idle-timeout?    uint32

   The above subtree illustrates how the ietf-netconf-server YANG module
   enables configuration of NETCONF session options, independent of any
   transport or connection strategy.  A feature statement is used for
   the server to advertise support for configuring these NETCONF server
   options.  Please see the YANG module (Section 3.2) for a complete
   description of these configuration knobs.

3.1.2.  The "listen" subtree























Watsen & Schoenwaelder    Expires June 14, 2015                 [Page 8]


Internet-Draft    NETCONF/RESTCONF Server Config Models    December 2014


   module: ietf-netconf-server
      +--rw netconf-server
         +--rw listen {listen}?
            +--rw max-sessions?   uint16
            +--rw endpoint* [name]
               +--rw name           string
               +--rw (transport)
               |  +--:(ssh) {ssh}?
               |  |  +--rw ssh
               |  |     +--rw address?     inet:ip-address
               |  |     +--rw port?        inet:port-number
               |  |     +--rw host-keys
               |  |        +--rw host-key*   string
               |  +--:(tls) {tls}?
               |     +--rw tls
               |        +--rw address?        inet:ip-address
               |        +--rw port?           inet:port-number
               |        +--rw certificates
               |           +--rw certificate*   string
               +--rw keep-alives
                  +--rw interval-secs?   uint8
                  +--rw count-max?       uint8

   The above subtree illustrates how the ietf-netconf-server YANG module
   enables configuration for listening for remote connections, as
   described in [RFC6242] and [draft-ietf-netconf-call-home].  Feature
   statements are used to limit both if listening is supported at all as
   well as for which transports.  If listening for connections is
   supported, then the model enables configuring a list of listening
   endpoints, each configured with a user-specified name (the key
   field), the transport to use (i.e.  SSH, TLS), and the IP address and
   port to listen on.  The port field is optional, defaulting to the
   transport-specific port when not configured.  Please see the YANG
   module (Section 3.2) for a complete description of these
   configuration knobs.

3.1.3.  The "call-home" subtree














Watsen & Schoenwaelder    Expires June 14, 2015                 [Page 9]


Internet-Draft    NETCONF/RESTCONF Server Config Models    December 2014


   module: ietf-netconf-server
      +--rw netconf-server
         +--rw call-home {call-home}?
            +--rw application* [name]
               +--rw name                  string
               +--rw (transport)
               |  +--:(ssh) {ssh}?
               |  |  +--rw ssh
               |  |     +--rw endpoints
               |  |     |  +--rw endpoint* [name]
               |  |     |     +--rw name       string
               |  |     |     +--rw address    inet:host
               |  |     |     +--rw port?      inet:port-number
               |  |     +--rw host-keys
               |  |        +--rw host-key*   string
               |  +--:(tls) {tls}?
               |     +--rw tls
               |        +--rw endpoints
               |        |  +--rw endpoint* [name]
               |        |     +--rw name       string
               |        |     +--rw address    inet:host
               |        |     +--rw port?      inet:port-number
               |        +--rw certificates
               |           +--rw certificate*   string
               +--rw connection-type
               |  +--rw (connection-type)?
               |     +--:(persistent-connection)
               |     |  +--rw persistent
               |     |     +--rw keep-alives
               |     |        +--rw interval-secs?   uint8
               |     |        +--rw count-max?       uint8
               |     +--:(periodic-connection)
               |        +--rw periodic
               |           +--rw timeout-mins?   uint8
               |           +--rw linger-secs?    uint8
               +--rw reconnect-strategy
                  +--rw start-with?      enumeration
                  +--rw interval-secs?   uint8
                  +--rw count-max?       uint8

   The above subtree illustrates how the ietf-netconf-server YANG module
   enables configuration for call home, as described in
   [draft-ietf-netconf-call-home].  Feature statements are used to limit
   both if call-home is supported at all as well as for which
   transports, if it is.  If call-home is supported, then the model
   supports configuring a list of applications to connect to.  Each
   application is configured with a user-specified name (the key field),
   the transport to be used (i.e.  SSH, TLS), and a list of remote



Watsen & Schoenwaelder    Expires June 14, 2015                [Page 10]


Internet-Draft    NETCONF/RESTCONF Server Config Models    December 2014


   endpoints, each having a name, an IP address, and an optional port.
   Additionally, the configuration for each remote application indicates
   the connection-type (persistent vs. periodic) and associated
   parameters, as well as the reconnection strategy to use.  Please see
   the YANG module (Section 3.2) for a complete description of these
   configuration knobs.

3.1.4.  The "ssh" subtree

   module: ietf-netconf-server
      +--rw netconf-server
         +--rw ssh {ssh}?
            +--rw x509 {rfc6187}?
               +--rw trusted-ca-certs
               |  +--rw trusted-ca-cert*   binary
               +--rw trusted-client-certs
                  +--rw trusted-client-cert*   binary

   The above subtree illustrates how the ietf-netconf-server YANG module
   enables some SSH configuration independent of if the NETCONF server
   is listening or calling home.  Specifically, when RFC 6187 is
   supported, this data model provides an ability to configure how
   client-certificates are authenticated.  Please see the YANG module
   (Section 3.2) for a complete description of these configuration
   knobs.

3.1.5.  The "tls" subtree

   module: ietf-netconf-server
      +--rw netconf-server
         +--rw tls {tls}?
            +--rw client-auth
               +--rw trusted-ca-certs
               |  +--rw trusted-ca-cert*   binary
               +--rw trusted-client-certs
               |  +--rw trusted-client-cert*   binary
               +--rw cert-maps
                  +--rw cert-to-name* [id]
                     +--rw id             uint32
                     +--rw fingerprint    x509c2n:tls-fingerprint
                     +--rw map-type       identityref
                     +--rw name           string

   The above subtree illustrates how the ietf-netconf-server YANG module
   enables TLS configuration independent of if the NETCONF server is
   listening or calling home.  Specifically, this data-model provides 1)
   an ability to configure how client-certificates are authenticated and
   2) how authenticated client-certificates are mapped to NETCONF user



Watsen & Schoenwaelder    Expires June 14, 2015                [Page 11]


Internet-Draft    NETCONF/RESTCONF Server Config Models    December 2014


   names.  Please see the YANG module (Section 3.2) for a complete
   description of these configuration knobs.

3.2.  YANG Module

   This YANG module imports YANG types from [RFC6991], and
   [draft-ietf-netmod-snmp-cfg].

<CODE BEGINS> file "ietf-netconf-server@2014-12-11.yang"

module ietf-netconf-server {

  namespace "urn:ietf:params:xml:ns:yang:ietf-netconf-server";
  prefix "ncserver";

  import ietf-inet-types {           // RFC 6991
    prefix inet;
    revision-date 2013-07-15;
  }
  import ietf-x509-cert-to-name {    // RFC ZZZZ
    prefix x509c2n;
    revision-date 2014-05-06;
  }

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

  contact
   "WG Web:   <http://tools.ietf.org/wg/netconf/>
    WG List:  <mailto:netconf@ietf.org>

    WG Chair: Mehmet Ersue
              <mailto:mehmet.ersue@nsn.com>

    WG Chair: Mahesh Jethanandani
              <mailto:mjethanandani@gmail.com>

    Editor:   Kent Watsen
              <mailto:kwatsen@juniper.net>";


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

    Copyright (c) 2014 IETF Trust and the persons identified as
    authors of the code. All rights reserved.




Watsen & Schoenwaelder    Expires June 14, 2015                [Page 12]


Internet-Draft    NETCONF/RESTCONF Server Config Models    December 2014


    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 VVVV; see
    the RFC itself for full legal notices.";

  revision "2014-12-11" {
    description
     "Initial version";
    reference
     "RFC VVVV: NETCONF Server and RESTCONF Server Configuration Models";
  }


  // Features

  feature session-options {
    description
     "The session-options feature indicates that the NETCONF server
      supports the session-options container.";
  }

  feature ssh {
    description
     "The ssh feature indicates that the server supports the
      SSH transport protocol.";
    reference
     "RFC 6242: Using the NETCONF Protocol over Secure Shell (SSH)";
  }

  feature tls {
    description
     "The tls feature indicates that the server supports the
      TLS transport protocol.";
    reference
     "RFC 5539: NETCONF over Transport Layer Security (TLS)";
  }

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



Watsen & Schoenwaelder    Expires June 14, 2015                [Page 13]


Internet-Draft    NETCONF/RESTCONF Server Config Models    December 2014


      RFC 5539: NETCONF over Transport Layer Security (TLS)";
  }

  feature call-home {
    description
     "The call-home feature indicates that the server supports
      connecting to the client";
    reference
     "RFC YYYY: NETCONF Call Home and RESTCONF Call Home";
  }

  feature rfc6187 {
    description
      "The rfc6187 feature indicates that the NETCONF server supports
       RFC 6187";
    reference
      "RFC 6187: X.509v3 Certificates for Secure Shell Authentication";
  }



  // top-level container  (groupings below)
  container netconf-server {
    description
      "Top-level container for NETCONF server configuration.";

    uses session-options-container;
    uses listen-container;
    uses call-home-container;
    uses ssh-container;
    uses tls-container;

  }


  grouping session-options-container {
    description
      "";
    container session-options {
      description
        "NETCONF session options, independent of transport or
         connection strategy.";
      if-feature session-options;
      leaf hello-timeout {
        type uint32 {
          range "0 | 10 .. 3600";
        }
        units "seconds";



Watsen & Schoenwaelder    Expires June 14, 2015                [Page 14]


Internet-Draft    NETCONF/RESTCONF Server Config Models    December 2014


        default '600';
        description
          "Specifies the number of seconds that a session may exist
           before the hello PDU is received.  A session will be
           dropped if no hello PDU is received before this number
           of seconds elapses.

           If this parameter is set to zero, then the server will
           wait forever for a hello message, and not drop any
           sessions stuck in 'hello-wait' state.

           Setting this parameter to zero may permit denial of
           service attacks, since only a limited number of
           concurrent sessions may be supported by the server.";
      }
      leaf idle-timeout {
        type uint32 {
          range "0 | 10 .. 360000";
        }
        units "seconds";
        default '3600';
        description
          "Specifies the number of seconds that a NETCONF session may
           remain idle without issuing any RPC requests.  A session
           will be dropped if it is idle for an interval longer than
           this number of seconds.  If this parameter is 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.

           This mechanism is independent of keep-alives, as it regards
           activity occurring at the NETCONF protocol layer, whereas
           the keep-alive mechanism regards transport-level activity.";
      }
    }
  }

  grouping listen-container {
    description
      "";
    container listen {
      description
        "Configures listen behavior";
      if-feature listen;
      leaf max-sessions {
        type uint16 {
          range "0 .. 1024";
        }



Watsen & Schoenwaelder    Expires June 14, 2015                [Page 15]


Internet-Draft    NETCONF/RESTCONF Server Config Models    December 2014


        default '0';
        description
          "Specifies the maximum number of concurrent sessions
             that can be active at one time.  The value 0 indicates
             that no artificial session limit should be used.";
      }
      list endpoint {
        key name;
        description
          "List of endpoints to listen for connections on.";
        leaf name {
          type string;
          description
            "An arbitrary name for the listen endpoint.";
        }
        choice transport {
          mandatory true;
          description
            "Selects between SSH and TLS transports.";
          case ssh {
            if-feature ssh;
            container ssh {
              description
                "SSH-specific listening configuration for inbound
                 connections.";
              uses address-and-port-grouping {
                refine port {
                  default 830;
                }
              }
              uses host-keys-container;
            }
          }
          case tls {
            if-feature tls;
            container tls {
              description
                "TLS-specific listening configuration for inbound
                 connections.";
              uses address-and-port-grouping {
                refine port {
                  default 6513;
                }
              }
              uses certificates-container;
            }
          }
        }



Watsen & Schoenwaelder    Expires June 14, 2015                [Page 16]


Internet-Draft    NETCONF/RESTCONF Server Config Models    December 2014


        uses keep-alives-container  {
          refine keep-alives/interval-secs {
            default 0; // disabled by default for listen connections
          }
        }
      }
    }
  }

  grouping call-home-container {
    description
      "";
    container call-home {
      if-feature call-home;
      description
        "Configures call-home behavior";
      list application {
        key name;
        description
          "List of NETCONF clients the NETCONF server is to initiate
           call-home connections to.";
        leaf name {
          type string;
          description
            "An arbitrary name for the remote NETCONF client.";
        }
        choice transport {
          mandatory true;
          description
            "Selects between available transports.";
          case ssh {
            if-feature ssh;
            container ssh {
              description
                "Specifies SSH-specific call-home transport
                 configuration.";
              uses endpoints-container {
                refine endpoints/endpoint/port {
                  default 7777;
                }
              }
              uses host-keys-container;
            }
          }
          case tls {
            if-feature tls;
            container tls {
              description



Watsen & Schoenwaelder    Expires June 14, 2015                [Page 17]


Internet-Draft    NETCONF/RESTCONF Server Config Models    December 2014


                "Specifies TLS-specific call-home transport
                 configuration.";
              uses endpoints-container {
                refine endpoints/endpoint/port {
                  default 8888;
                }
              }
              uses certificates-container;
            }
          }
        }
        container connection-type {
          description
           "Indicates the kind of connection to be maintained.";
          choice connection-type {
            default persistent-connection;
            description
              "Selects between persistent and periodic connections.";
            case persistent-connection {
              container persistent {
                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.";
                uses keep-alives-container  {
                  refine keep-alives/interval-secs {
                    default 15; // 15 seconds for call-home sessions
                  }
                }
              }
            }
            case periodic-connection {
              container periodic {
                description
                 "Periodically connect to NETCONF client, using the
                  reconnection strategy, so the NETCONF client can
                  deliver pending messages to the NETCONF server.

                  For messages the NETCONF server wants to send to
                  to the NETCONF client, the NETCONF server should
                  proactively connect to the NETCONF client, if
                  not already, to send the messages immediately.";
                leaf timeout-mins {



Watsen & Schoenwaelder    Expires June 14, 2015                [Page 18]


Internet-Draft    NETCONF/RESTCONF Server Config Models    December 2014


                  type uint8;
                  units minutes;
                  default 5;
                  description
                   "The maximum amount of unconnected time the NETCONF
                    server will wait until establishing a connection to
                    the NETCONF client again. The NETCONF server MAY
                    establish a connection before this time if it has
                    data it needs to send to the NETCONF client. Note:
                    this value differs from the reconnection strategy's
                    interval-secs value.";
                }
                leaf linger-secs {
                  type uint8;
                  units seconds;
                  default 30;
                  description
                   "The amount of time the NETCONF server should wait
                    after last receiving data from or sending data to
                    the NETCONF client's endpoint before closing its
                    connection to it.  This is an optimization to
                    prevent unnecessary connections.";
                }
              }
            }
          }
        }
        container reconnect-strategy {
          description
           "The reconnection strategy guides how a NETCONF server
            reconnects to an NETCONF client, after losing a connection
            to it, even if due to a reboot.  The NETCONF server starts
            with the specified endpoint and tries to connect to it
            count-max times, waiting interval-secs between each
            connection attempt, 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.  NETCONF servers
                   SHOULD support this flag across reboots.";



Watsen & Schoenwaelder    Expires June 14, 2015                [Page 19]


Internet-Draft    NETCONF/RESTCONF Server Config Models    December 2014


              }
            }
            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.  If no previous connection has
              ever been established, last-connected defaults to
              the first endpoint listed.";
          }
          leaf interval-secs {
            type uint8;
            units seconds;
            default 5;
            description
             "Specifies the time delay between connection attempts
              to the same endpoint.  Note: this value differs from
              the periodic-connection's timeout-mins value.";
          }
          leaf count-max {
            type uint8;
            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).";
          }
        }
      }
    }
  }


  grouping ssh-container {
    description
      "";
    container ssh {
      description
        "Configures SSH properties not specific to the listen
         or call-home use-cases";
      if-feature ssh;
      container x509 {
        if-feature rfc6187;
        uses trusted-certs-grouping;
      }
    }
  }




Watsen & Schoenwaelder    Expires June 14, 2015                [Page 20]


Internet-Draft    NETCONF/RESTCONF Server Config Models    December 2014


  grouping tls-container {
    description
      "";
    container tls {
      description
        "Configures TLS properties not specific to the listen
         or call-home use-cases";
      if-feature tls;
      container client-auth {
        description
          "Container for TLS client authentication configuration.";
        uses trusted-certs-grouping;
        container cert-maps {
          uses x509c2n:cert-to-name;
          description
           "The cert-maps container is used by a 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.";
        }
      }
    }
  }

  grouping trusted-certs-grouping {
    description
      "";
    container trusted-ca-certs {
      description
        "A list of Certificate Authority (CA) certificates that
         a NETCONF server can use to authenticate NETCONF client
         certificates.  A client's certificate is authenticated
         if there is a chain of trust to a configured trusted CA
         certificate.  The client certificate MAY be accompanied
         with additional certificates forming a chain of trust.
         The client's certificate is authenticated if there is
         path-validation from any of the certificates it presents
         to a configured trust anchor.";
      leaf-list trusted-ca-cert {
        type binary;
        ordered-by system;
        description
          "The binary certificate structure as specified by RFC
           5246, Section 7.4.6, i.e.,: opaque ASN.1Cert<1..2^24>;
          ";
        reference



Watsen & Schoenwaelder    Expires June 14, 2015                [Page 21]


Internet-Draft    NETCONF/RESTCONF Server Config Models    December 2014


          "RFC 5246: The Transport Layer Security (TLS)
                     Protocol Version 1.2";
      }
    }
    container trusted-client-certs {
      description
        "A list of client certificates that a NETCONF server can
         use to authenticate a NETCONF client's certificate.  A
         client's certificate is authenticated if it is an exact
         match to a configured trusted client certificates.";
      leaf-list trusted-client-cert {
        type binary;
        ordered-by system;
        description
          "The binary certificate structure, as
           specified by RFC 5246, Section 7.4.6, i.e.,:

             opaque ASN.1Cert<1..2^24>;

          ";
        reference
          "RFC 5246: The Transport Layer Security (TLS)
                     Protocol Version 1.2";
      }
    }
  }

  grouping host-keys-container {
    description
      "";
    container host-keys {
      description
        "Parent container for the list of host-keys.";
      leaf-list host-key {
        type string;
        min-elements 1;
        ordered-by user;
        description
          "A user-ordered list of host-keys the SSH server
           considers when composing the list of server host
           key algorithms it will send to the client in its
           SSH_MSG_KEXINIT message.  The value of the string
           is the unique identifier for a host-key configured
           on the system.  How valid values are discovered is
           outside the scope of this module, but they are
           envisioned to be the keys for a list of host-keys
           provided by another YANG module";
        reference



Watsen & Schoenwaelder    Expires June 14, 2015                [Page 22]


Internet-Draft    NETCONF/RESTCONF Server Config Models    December 2014


          "RFC 4253: The SSH Transport Layer Protocol, Section 7";
      }
    }
  }

  grouping certificates-container {
    description
      "";
    container certificates {
      description
        "Parent container for the list of certificates.";
      leaf-list certificate {
        type string;
        min-elements 1;
        description
          "An unordered list of certificates the TLS server can pick
           from when sending its Server Certificate message.  The value
           of the string is the unique identifier for a certificate
           configured on the system.  How valid values are discovered
           is outside the scope of this module, but they are envisioned
           to be the keys for a list of certificates provided
           by another YANG module";
        reference
          "RFC 5246: The TLS Protocol, Section 7.4.2";
      }
    }
  }

  grouping address-and-port-grouping {
    description
      "a common grouping";
    leaf address {
      type inet:ip-address;
      description
       "The IP address of the interface to listen on.";
    }
    leaf port {
      type inet:port-number;
      description
       "The local port number on this interface the NETCONF server
        listens on.";
    }
  }


  grouping endpoints-container {
    description
      "Grouping for transport-specific configuration for



Watsen & Schoenwaelder    Expires June 14, 2015                [Page 23]


Internet-Draft    NETCONF/RESTCONF Server Config Models    December 2014


       call-home connections.";
    container endpoints {
      description
        "Container for the list of endpoints.";
      list endpoint {
        key name;
        min-elements 1;
        ordered-by user;
        description
          "User-ordered list of endpoints for this NETCONF client.
           Defining more than one enables high-availability.";
        leaf name {
          type string;
          description
            "An arbitrary name for the endpoint to connect to.";
        }
        leaf address {
          type inet:host;
          mandatory true;
          description
           "The hostname or IP address or hostname of the endpoint.
            If a hostname is provided and DNS resolves to more than
            one IP address, the NETCONF server SHOULD try all of
            the ones it can based on how its networking stack is
            configured (e.g. v4, v6, dual-stack).";
        }
        leaf port {
          type inet:port-number;
          description
           "The IP port for this endpoint. The NETCONF server will
            use the IANA-assigned well-known port if not specified.";
        }
      }
    }
  }

  grouping keep-alives-container {
    description
      "";
    container keep-alives {
      description
        "Configures the keep-alive policy, to proactively test the
         aliveness of the NETCONF client, in order to know when a
         new call home connection should be established.";
      reference
        "RFC VVVV: NETCONF Server and RESTCONF Server Configuration
         Models, Section 4";
      leaf interval-secs {



Watsen & Schoenwaelder    Expires June 14, 2015                [Page 24]


Internet-Draft    NETCONF/RESTCONF Server Config Models    December 2014


        type uint8;
        units seconds;
        description
         "Sets a timeout interval in seconds after which if no data
          has been received from the NETCONF client, a message will
          be sent to request a response from the NETCONF client.  A
          value of '0' indicates that no keep-alive messages should
          be sent.";
      }
      leaf count-max {
        type uint8;
        default 3;
        description
         "Sets the number of keep-alive messages that may be sent
          without receiving any data from the NETCONF client before
          assuming the NETCONF client is no longer alive.  If this
          threshold is reached, the transport-level connection will
          be disconnected, which will trigger the reconnection
          strategy).  The interval timer is reset after each
          transmission, thus an unresponsive NETCONF client will
          be dropped after ~count-max * interval-secs seconds.";
      }
    }
  }
}


<CODE ENDS>

4.  The RESTCONF Server Configuration Model

4.1.  Overview

4.1.1.  The "listen" subtree

















Watsen & Schoenwaelder    Expires June 14, 2015                [Page 25]


Internet-Draft    NETCONF/RESTCONF Server Config Models    December 2014


   module: ietf-restconf-server
      +--rw restconf-server
         +--rw listen {listen}?
            +--rw max-sessions?   uint16
            +--rw endpoint* [name]
               +--rw name           string
               +--rw (transport)
               |  +--:(tls)
               |     +--rw tls
               |        +--rw address?        inet:ip-address
               |        +--rw port?           inet:port-number
               |        +--rw certificates
               |           +--rw certificate*   string
               +--rw keep-alives
                  +--rw interval-secs?   uint8
                  +--rw count-max?       uint8

   The above subtree illustrates how the ietf-restconf-server YANG
   module enables configuration for listening for remote connections, as
   described in [draft-ietf-netconf-restconf] and
   [draft-ietf-netconf-call-home].  Feature statements are used to limit
   both if listening is supported at all as well as for which
   transports.  If listening for connections is supported, then the
   model enables configuring a list of listening endpoints, each
   configured with a user-specified name (the key field), the transport
   to use (i.e.  SSH, TLS), and the IP address and port to listen on.
   The port field is optional, defaulting to the transport-specific port
   when not configured.  Please see the YANG module (Section 4.2) for a
   complete description of these configuration knobs.

4.1.2.  The "call-home" subtree




















Watsen & Schoenwaelder    Expires June 14, 2015                [Page 26]


Internet-Draft    NETCONF/RESTCONF Server Config Models    December 2014


   module: ietf-restconf-server
      +--rw restconf-server
         +--rw call-home {call-home}?
            +--rw application* [name]
               +--rw name                  string
               +--rw (transport)
               |  +--:(tls) {tls}?
               |     +--rw tls
               |        +--rw endpoints
               |        |  +--rw endpoint* [name]
               |        |     +--rw name       string
               |        |     +--rw address    inet:host
               |        |     +--rw port?      inet:port-number
               |        +--rw certificates
               |           +--rw certificate*   string
               +--rw connection-type
               |  +--rw (connection-type)?
               |     +--:(persistent-connection)
               |     |  +--rw persistent
               |     |     +--rw keep-alives
               |     |        +--rw interval-secs?   uint8
               |     |        +--rw count-max?       uint8
               |     +--:(periodic-connection)
               |        +--rw periodic
               |           +--rw timeout-mins?   uint8
               |           +--rw linger-secs?    uint8
               +--rw reconnect-strategy
                  +--rw start-with?      enumeration
                  +--rw interval-secs?   uint8
                  +--rw count-max?       uint8

   The above subtree illustrates how the ietf-restconf-server YANG
   module enables configuration for call home, as described in
   [draft-ietf-netconf-call-home].  Feature statements are used to limit
   both if call-home is supported at all as well as for which
   transports, if it is.  If call-home is supported, then the model
   supports configuring a list of applications to connect to.  Each
   application is configured with a user-specified name (the key field),
   the transport to be used (i.e.  SSH, TLS), and a list of remote
   endpoints, each having a name, an IP address, and an optional port.
   Additionally, the configuration for each remote application indicates
   the connection-type (persistent vs. periodic) and associated
   parameters, as well as the reconnection strategy to use.  Please see
   the YANG module (Section 4.2) for a complete description of these
   configuration knobs.






Watsen & Schoenwaelder    Expires June 14, 2015                [Page 27]


Internet-Draft    NETCONF/RESTCONF Server Config Models    December 2014


4.2.  YANG Module

   This YANG module imports YANG types from [RFC6991].

<CODE BEGINS> file "ietf-restconf-server@2014-12-11.yang"

module ietf-restconf-server {

  namespace "urn:ietf:params:xml:ns:yang:ietf-restconf-server";
  prefix "rcserver";

  import ietf-inet-types {           // RFC 6991
    prefix inet;
    revision-date 2013-07-15;
  }

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

  contact
   "WG Web:   <http://tools.ietf.org/wg/netconf/>
    WG List:  <mailto:netconf@ietf.org>

    WG Chair: Mehmet Ersue
              <mailto:mehmet.ersue@nsn.com>

    WG Chair: Mahesh Jethanandani
              <mailto:mjethanandani@gmail.com>

    Editor:   Kent Watsen
              <mailto:kwatsen@juniper.net>";


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

    Copyright (c) 2014 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 VVVV; see



Watsen & Schoenwaelder    Expires June 14, 2015                [Page 28]


Internet-Draft    NETCONF/RESTCONF Server Config Models    December 2014


    the RFC itself for full legal notices.";

  revision "2014-12-11" {
    description
     "Initial version";
    reference
     "RFC VVVV: NETCONF Server and RESTCONF Server Configuration Models";
  }


  // Features

  feature tls {
    description
     "The tls feature indicates that the server supports RESTCONF
      over the TLS transport protocol.";
    reference
     "RFC XXXX: RESTCONF Protocol";
  }

  feature listen {
    description
     "The listen feature indicates that the server supports
      opening a port to listen for incoming client connections.";
    reference
     "RFC XXXX: RESTCONF Protocol";
  }

  feature call-home {
    description
     "The call-home feature indicates that the server supports
      connecting to the client";
    reference
     "RFC YYYY: NETCONF Call Home and RESTCONF Call Home";
  }


  // top-level container  (groupings below)
  container restconf-server {
    description
      "Top-level container for RESTCONF server configuration.";

    uses listen-container;
    uses call-home-container;
  }


  grouping listen-container {



Watsen & Schoenwaelder    Expires June 14, 2015                [Page 29]


Internet-Draft    NETCONF/RESTCONF Server Config Models    December 2014


    description
      "";
    container listen {
      description
        "Configures listen behavior";
      if-feature listen;
      leaf max-sessions {
        type uint16 {
          range "0 .. 1024";
        }
        default '0';
        description
          "Specifies the maximum number of concurrent sessions
           that can be active at one time.  The value 0 indicates
           that no artificial session limit should be used.";
      }
      list endpoint {
        key name;
        description
          "List of endpoints to listen for connections on.";
        leaf name {
          type string;
          description
            "An arbitrary name for the listen endpoint.";
        }
        choice transport {
          mandatory true;
          description
            "Selects between available transports.";
          case tls {
            container tls {
              description
                "TLS-specific listening configuration for inbound
                 connections.";
              uses address-and-port-grouping {
                refine port {
                  default 6513;
                }
              }
              uses certificates-container;
            }
          }
        }
        uses keep-alives-container  {
          refine keep-alives/interval-secs {
            default 0; // disabled by default for listen connections
          }
        }



Watsen & Schoenwaelder    Expires June 14, 2015                [Page 30]


Internet-Draft    NETCONF/RESTCONF Server Config Models    December 2014


      }
    }
  }

  grouping call-home-container {
    description
      "";
    container call-home {
      if-feature call-home;
      description
        "Configures call-home behavior";
      list application {
        key name;
        description
          "List of RESTCONF clients the RESTCONF server is to initiate
           call-home connections to.";
        leaf name {
          type string;
          description
            "An arbitrary name for the remote RESTCONF client.";
        }
        choice transport {
          mandatory true;
          description
            "Selects between SSH and TLS transports.";
          case tls {
            if-feature tls;
            container tls {
              description
                "Specifies TLS-specific call-home transport
                 configuration.";
              uses endpoints-container {
                refine endpoints/endpoint/port {
                  default 9999;
                }
              }
              uses certificates-container;
            }
          }
        }
        container connection-type {
          description
           "Indicates the RESTCONF client's preference for how the
            RESTCONF server's connection is maintained.";
          choice connection-type {
            default persistent-connection;
            description
              "Selects between persistent and periodic connections.";



Watsen & Schoenwaelder    Expires June 14, 2015                [Page 31]


Internet-Draft    NETCONF/RESTCONF Server Config Models    December 2014


            case persistent-connection {
              container persistent {
                description
                 "Maintain a persistent connection to the RESTCONF
                  client. If the connection goes down, immediately
                  start trying to reconnect to it, using the
                  reconnection strategy.

                  This connection type minimizes any RESTCONF client
                  to RESTCONF server data-transfer delay, albeit at
                  the expense of holding resources longer.";
                uses keep-alives-container  {
                  refine keep-alives/interval-secs {
                    default 15; // 15 seconds for call-home sessions
                  }
                }
              }
            }
            case periodic-connection {
              container periodic {
                description
                 "Periodically connect to RESTCONF client, using the
                  reconnection strategy, so the RESTCONF client can
                  deliver pending messages to the RESTCONF server.

                  For messages the RESTCONF server wants to send to
                  to the RESTCONF client, the RESTCONF server should
                  proactively connect to the RESTCONF client, if
                  not already, to send the messages immediately.";
                leaf timeout-mins {
                  type uint8;
                  units minutes;
                  default 5;
                  description
                   "The maximum amount of unconnected time the RESTCONF
                    server will wait until establishing a connection to
                    the RESTCONF client again. The RESTCONF server MAY
                    establish a connection before this time if it has
                    data it needs to send to the RESTCONF client. Note:
                    this value differs from the reconnection strategy's
                    interval-secs value.";
                }
                leaf linger-secs {
                  type uint8;
                  units seconds;
                  default 30;
                  description
                   "The amount of time the RESTCONF server should wait



Watsen & Schoenwaelder    Expires June 14, 2015                [Page 32]


Internet-Draft    NETCONF/RESTCONF Server Config Models    December 2014


                    after last receiving data from or sending data to
                    the RESTCONF client's endpoint before closing its
                    connection to it.  This is an optimization to
                    prevent unnecessary connections.";
                }
              }
            }
          }
        }
        container reconnect-strategy {
          description
           "The reconnection strategy guides how a RESTCONF server
            reconnects to an RESTCONF client, after losing a connection
            to it, even if due to a reboot.  The RESTCONF server starts
            with the specified endpoint and tries to connect to it
            count-max times, waiting interval-secs between each
            connection attempt, 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.  RESTCONF servers
                   SHOULD support this flag across reboots.";
              }
            }
            default first-listed;
            description
             "Specifies which of the RESTCONF client's endpoints the
              RESTCONF server should start with when trying to connect
              to the RESTCONF client.  If no previous connection has
              ever been established, last-connected defaults to
              the first endpoint listed.";
          }
          leaf interval-secs {
            type uint8;
            units seconds;
            default 5;
            description
             "Specifies the time delay between connection attempts
              to the same endpoint.  Note: this value differs from
              the periodic-connection's timeout-mins value.";



Watsen & Schoenwaelder    Expires June 14, 2015                [Page 33]


Internet-Draft    NETCONF/RESTCONF Server Config Models    December 2014


          }
          leaf count-max {
            type uint8;
            default 3;
            description
             "Specifies the number times the RESTCONF server tries to
              connect to a specific endpoint before moving on to the
              next endpoint in the list (round robin).";
          }
        }
      }
    }
  }

  grouping certificates-container {
    description
      "";
    container certificates {
      description
        "Parent container for the list of certificates.";
      leaf-list certificate {
        type string;
        min-elements 1;
        description
          "An unordered list of certificates the TLS server can pick
           from when sending its Server Certificate message.  The value
           of the string is the unique identifier for a certificate
           configured on the system.  How valid values are discovered
           is outside the scope of this module, but they are envisioned
           to be the keys for a list of certificates provided
           by another YANG module";
        reference
          "RFC 5246: The TLS Protocol, Section 7.4.2";
      }
    }
  }

  grouping address-and-port-grouping {
    description
      "a common grouping";
    leaf address {
      type inet:ip-address;
      description
       "The IP address of the interface to listen on.";
    }
    leaf port {
      type inet:port-number;
      description



Watsen & Schoenwaelder    Expires June 14, 2015                [Page 34]


Internet-Draft    NETCONF/RESTCONF Server Config Models    December 2014


       "The local port number on this interface the RESTCONF server
        listens on.";
    }
  }


  grouping endpoints-container {
    description
      "Grouping for transport-specific configuration for
       call-home connections.";
    container endpoints {
      description
        "Container for the list of endpoints.";
      list endpoint {
        key name;
        min-elements 1;
        ordered-by user;
        description
          "User-ordered list of endpoints for this RESTCONF client.
           Defining more than one enables high-availability.";
        leaf name {
          type string;
          description
            "An arbitrary name for the endpoint to connect to.";
        }
        leaf address {
          type inet:host;
          mandatory true;
          description
           "The hostname or IP address or hostname of the endpoint.
            If a hostname is provided and DNS resolves to more than
            one IP address, the RESTCONF server SHOULD try all of
            the ones it can based on how its networking stack is
            configured (e.g. v4, v6, dual-stack).";
        }
        leaf port {
          type inet:port-number;
          description
           "The IP port for this endpoint. The RESTCONF server will
            use the IANA-assigned well-known port if not specified.";
        }
      }
    }
  }

  grouping keep-alives-container {
    description
      "";



Watsen & Schoenwaelder    Expires June 14, 2015                [Page 35]


Internet-Draft    NETCONF/RESTCONF Server Config Models    December 2014


    container keep-alives {
      description
        "Configures the keep-alive policy, to proactively test the
         aliveness of the RESTCONF client, in order to know when a
         new call home connection should be established.";
      reference
        "RFC VVVV: NETCONF Server and RESTCONF Server Configuration
         Models, Section 4";
      leaf interval-secs {
        type uint8;
        units seconds;
        description
         "Sets a timeout interval in seconds after which if no data
          has been received from the RESTCONF client, a message will
          be sent to request a response from the RESTCONF client.  A
          value of '0' indicates that no keep-alive messages should
          be sent.";
      }
      leaf count-max {
        type uint8;
        default 3;
        description
         "Sets the number of keep-alive messages that may be sent
          without receiving any data from the RESTCONF client before
          assuming the RESTCONF client is no longer alive.  If this
          threshold is reached, the transport-level connection will
          be disconnected, which will trigger the reconnection
          strategy).  The interval timer is reset after each
          transmission, thus an unresponsive RESTCONF client will
          be dropped after ~count-max * interval-secs seconds.";
      }
    }
  }
}


<CODE ENDS>

5.  Implementation strategy for keep-alives

   One of the objectives listed above, Keep-alives for persistent
   connections Section 2.6.6, indicates a need for a "keep-alive"
   mechanism.  This section specifies how the keep-alive mechanism is to
   be implemented for both the SSH and TLS transports.

   Both SSH and TLS have the ability to support keep-alives securely.
   Using the strategies listed below, the keep-alive messages are sent
   inside the encrypted tunnel and thus immune to attack.



Watsen & Schoenwaelder    Expires June 14, 2015                [Page 36]


Internet-Draft    NETCONF/RESTCONF Server Config Models    December 2014


5.1.  Keep-alives for SSH

   The SSH keep-alive solution that is expected to be used is ubiquitous
   in practice, though never being explicitly defined in an RFC.  The
   strategy used is to purposely send a malformed request message with a
   flag set to ensure a response.  More specifically, per section 4 of
   [RFC4253], either SSH peer can send a SSH_MSG_GLOBAL_REQUEST message
   with "want reply" set to '1' and that, if there is an error, will get
   back a SSH_MSG_REQUEST_FAILURE response.  Similarly, section 5 of
   [RFC4253] says that either SSH peer can send a
   SSH_MSG_CHANNEL_REQUEST message with "want reply" set to '1' and
   that, if there is an error, will get back a SSH_MSG_CHANNEL_FAILURE
   response.

   To ensure that the request will fail, current implementations of this
   keep-alive strategy (e.g.  OpenSSH's `sshd` server) send an invalid
   "request name" or "request type", respectively.  Abiding to the
   extensibility guidelines specified in Section 6 of [RFC4251], these
   implementations use the "name@domain".  For instance, when configured
   to send keep-alives, OpenSSH sends the string
   "keepalive@openssh.com".  In order to remain compatible with existing
   implementations, this draft does not require a specific "request
   name" or "request type" string be used, implementations are free to
   pick values of their choosing.

5.2.  Keep-alives for TLS

   The TLS keep-alive solution that is expected to be used is defined in
   [RFC6520].  This solution allows both peers to advertise if they can
   receive heartbeat request messages from its peer.  For standard TLS
   connections, devices SHOULD advertise "peer_allowed_to_send", as per
   [RFC6520].  This advertisement is not a "MUST" in order to
   grandfather existing NETCONF/RESTCONF over TLS implementations.  For
   NETCONF Call Home or RESTCONF Call Home, the network management
   system MUST advertise "peer_allowed_to_send" per [RFC6520].  This is
   a "MUST" so as to ensure devices can depend on it always being there
   for call home connections, which is when keep-alives are needed the
   most.

6.  Security Considerations

   The YANG modules defined in this memo are designed to be accessed via
   the NETCONF protocol [RFC6241].  Authorization for access to specific
   portions of conceptual data and operations within this module is
   provided by the NETCONF access control model (NACM) [RFC6536].

   There are a number of data nodes defined in the "ietf-netconf-server"
   YANG module which are readable and/or writable that may be considered



Watsen & Schoenwaelder    Expires June 14, 2015                [Page 37]


Internet-Draft    NETCONF/RESTCONF Server Config Models    December 2014


   sensitive or vulnerable in some network environments.  Write and read
   operations to these data nodes can have a negative effect on network
   operations.  It is thus important to control write and read access to
   these data nodes.  Below are the data nodes and their sensitivity/
   vulnerability.

   netconf-server/tls/client-auth/trusted-ca-certs:

   o  This container contains certificates that the server is to use as
      trust anchors for authenticating TLS-specific client certificates.
      Write access to this node should be protected.

   netconf-server/tls/client-auth/trusted-client-certs:

   o  This container contains certificates that the server is to trust
      directly when authenticating TLS-specific client certificates.
      Write access to this node should be protected.

   netconf-server/tls/client-auth/cert-map:

   o  This container contains a user name that some deployments may
      consider sensitive information.  Read access to this node may need
      to be guarded.

7.  IANA Considerations

   This document registers two URIs in the IETF XML registry [RFC2119].
   Following the format in [RFC3688], the following registrations are
   requested:

      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.

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

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










Watsen & Schoenwaelder    Expires June 14, 2015                [Page 38]


Internet-Draft    NETCONF/RESTCONF Server Config Models    December 2014


      name:         ietf-netconf-server
      namespace:    urn:ietf:params:xml:ns:yang:ietf-netconf-server
      prefix:       ncserver
      reference:    RFC VVVV

      name:         ietf-restconf-server
      namespace:    urn:ietf:params:xml:ns:yang:ietf-restconf-server
      prefix:       rcserver
      reference:    RFC VVVV

8.  Other Considerations

   The YANG modules define herein do not themselves support virtual
   routing and forwarding (VRF).  It is expected that external modules
   will augment in VRF designations when needed.

9.  Acknowledgements

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

   Juergen Schoenwaelder and was partly funded by Flamingo, a Network of
   Excellence project (ICT-318488) supported by the European Commission
   under its Seventh Framework Programme.

10.  References

10.1.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

   [RFC4251]  Ylonen, T. and C. Lonvick, "The Secure Shell (SSH)
              Protocol Architecture", RFC 4251, January 2006.

   [RFC4253]  Ylonen, T. and C. Lonvick, "The Secure Shell (SSH)
              Transport Layer Protocol", RFC 4253, January 2006.

   [RFC6020]  Bjorklund, M., "YANG - A Data Modeling Language for the
              Network Configuration Protocol (NETCONF)", RFC 6020,
              October 2010.

   [RFC6187]  Igoe, K. and D. Stebila, "X.509v3 Certificates for Secure
              Shell Authentication", RFC 6187, March 2011.




Watsen & Schoenwaelder    Expires June 14, 2015                [Page 39]


Internet-Draft    NETCONF/RESTCONF Server Config Models    December 2014


   [RFC6241]  Enns, R., Bjorklund, M., Schoenwaelder, J., and A.
              Bierman, "Network Configuration Protocol (NETCONF)", RFC
              6241, June 2011.

   [RFC6242]  Wasserman, M., "Using the NETCONF Protocol over Secure
              Shell (SSH)", RFC 6242, June 2011.

   [RFC6520]  Seggelmann, R., Tuexen, M., and M. Williams, "Transport
              Layer Security (TLS) and Datagram Transport Layer Security
              (DTLS) Heartbeat Extension", RFC 6520, February 2012.

   [RFC6536]  Bierman, A. and M. Bjorklund, "Network Configuration
              Protocol (NETCONF) Access Control Model", RFC 6536, March
              2012.

   [RFC6991]  Schoenwaelder, J., "Common YANG Data Types", RFC 6991,
              July 2013.

   [draft-ietf-netconf-call-home]
              Watsen, K., "NETCONF Call Home and RESTCONF Call Home",
              draft-ieft-netconf-call-home-02 (work in progress), 2014.

   [draft-ietf-netconf-restconf]
              Bierman, A., Bjorklund, M., and K. Watsen, "RESTCONF
              Protocol", draft-ieft-netconf-restconf-04 (work in
              progress), 2014.

   [draft-ietf-netconf-rfc5539bis]
              Badra, M., Luchuk, A., and J. Schoenwaelder, "Using the
              NETCONF Protocol over Transport Layer Security (TLS)",
              draft-ietf-netconf-rfc5539bis-06 (work in progress), 2014.

   [draft-ietf-netmod-snmp-cfg]
              Bjorklund, M. and J. Schoenwaelder, "A YANG Data Model for
              SNMP Configuration", draft-ietf-netmod-snmp-cfg-08 (work
              in progress), September 2014.

10.2.  Informative References

   [RFC3688]  Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688,
              January 2004.










Watsen & Schoenwaelder    Expires June 14, 2015                [Page 40]


Internet-Draft    NETCONF/RESTCONF Server Config Models    December 2014


Appendix A.  Examples

A.1.  NETCONF Configuration using SSH Transport

   The following example illustrates the <get> response from a NETCONF
   server that only supports SSH, both listening for incoming
   connections as well as calling home to a single application having
   two endpoints.

<netconf-server xmlns="urn:ietf:params:xml:ns:yang:ietf-netconf-server">
  <session-options>
    <hello-timeout>600</hello-timeout>
    <idle-timeout>3600</idle-timeout>
  </session-options>
  <listen>
    <endpoint>
      <name>foo bar</name>
      <ssh>
        <address>11.22.33.44</address>
        <host-keys>
          <host-key>my-rsa-key</host-key>
          <host-key>my-dss-key</host-key>
        </host-keys>
      </ssh>
    </endpoint>
  </listen>
  <call-home>
    <application>
      <name>config-mgr</name>
      <ssh>
        <endpoints>
          <endpoint>
            <name>east-data-center</name>
            <address>11.22.33.44</address>
          </endpoint>
          <endpoint>
            <name>west-data-center</name>
            <address>55.66.77.88</address>
          </endpoint>
        </endpoints>
        <host-keys>
          <host-key>my-call-home-x509-key</host-key>
        </host-keys>
      </ssh>
    </application>
  </call-home>
  <ssh>
    <x509>



Watsen & Schoenwaelder    Expires June 14, 2015                [Page 41]


Internet-Draft    NETCONF/RESTCONF Server Config Models    December 2014


      <trusted-ca-certs>
        <trusted-ca-cert>
          QW4gRWFzdGVyIGVnZywgZm9yIHRob3NlIHdobyBtaWdodCBsb29rICA6KQo=
        </trusted-ca-cert>
      </trusted-ca-certs>
      <trusted-client-certs>
        <trusted-client-cert>
          SSBhbSB0aGUgZWdnIG1hbiwgdGhleSBhcmUgdGhlIGVnZyBtZW4uCg==
        </trusted-client-cert>
        <trusted-client-cert>
          SSBhbSB0aGUgd2FscnVzLCBnb28gZ29vIGcnam9vYi4K
        </trusted-client-cert>
      </trusted-client-certs>
    </x509>
  </ssh>
</netconf-server>

A.2.  NETCONF Configuration using TLS Transport

   The following example illustrates the <get> response from a NETCONF
   server that only supports TLS, both listening for incoming
   connections as well as calling home to a single application having
   two endpoints.  Please note also the configurations for
   authenticating client certificates and mappings authenticated
   certificates to NETCONF user names.

<netconf-server xmlns="urn:ietf:params:xml:ns:yang:ietf-netconf-server">
  <session-options>
    <hello-timeout>600</hello-timeout>
    <idle-timeout>3600</idle-timeout>
  </session-options>
  <listen>
    <endpoint>
      <name>primary-netconf-endpoint</name>
      <tls>
        <address>11.22.33.44</address>
        <certificates>
          <certificate>fw1.east.example.com</certificate>
        </certificates>
      </tls>
    </endpoint>
  </listen>
  <call-home>
    <application>
      <name>config-mgr</name>
      <tls>
        <endpoints>
          <endpoint>



Watsen & Schoenwaelder    Expires June 14, 2015                [Page 42]


Internet-Draft    NETCONF/RESTCONF Server Config Models    December 2014


            <name>east-data-center</name>
            <address>11.22.33.44</address>
          </endpoint>
          <endpoint>
            <name>west-data-center</name>
            <address>55.66.77.88</address>
          </endpoint>
        </endpoints>
        <certificates>
          <certificate>fw1.east.example.com</certificate>
        </certificates>
      </tls>
    </application>
  </call-home>
  <tls>
    <client-auth>
      <trusted-ca-certs>
        <trusted-ca-cert>
          QW4gRWFzdGVyIGVnZywgZm9yIHRob3NlIHdobyBtaWdodCBsb29rICA6KQo=
        </trusted-ca-cert>
      </trusted-ca-certs>
      <trusted-client-certs>
        <trusted-client-cert>
          SSBhbSB0aGUgZWdnIG1hbiwgdGhleSBhcmUgdGhlIGVnZyBtZW4uCg==
        </trusted-client-cert>
        <trusted-client-cert>
          SSBhbSB0aGUgd2FscnVzLCBnb28gZ29vIGcnam9vYi4K
        </trusted-client-cert>
      </trusted-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>11:0A:05:11:00</fingerprint>
          <map-type>x509c2n:specified</map-type>
          <name>Joe Cool</name>
        </cert-to-name>
      </cert-maps>
    </client-auth>
  </tls>
</netconf-server>






Watsen & Schoenwaelder    Expires June 14, 2015                [Page 43]


Internet-Draft    NETCONF/RESTCONF Server Config Models    December 2014


A.3.  RESTCONF Configuration using TLS Transport

   The following example illustrates the <get> response from a RESTCONF
   server that only supports TLS, both listening for incoming
   connections as well as calling home to a single application having
   two endpoints.

<restconf-server xmlns="urn:ietf:params:xml:ns:yang:ietf-restconf-server">
  <listen>
    <endpoint>
      <name>primary-restconf-endpoint</name>
      <tls>
        <address>11.22.33.44</address>
        <certificates>
          <certificate>fw1.east.example.com</certificate>
        </certificates>
      </tls>
    </endpoint>
  </listen>
  <call-home>
    <application>
      <name>config-mgr</name>
      <tls>
        <endpoints>
          <endpoint>
            <name>east-data-center</name>
            <address>11.22.33.44</address>
          </endpoint>
          <endpoint>
            <name>west-data-center</name>
            <address>55.66.77.88</address>
          </endpoint>
        </endpoints>
        <certificates>
          <certificate>fw1.east.example.com</certificate>
        </certificates>
      </tls>
    </application>
  </call-home>
</restconf-server>

Appendix B.  Change Log

B.1.  00 to 01

   o  Restructured document so it flows better





Watsen & Schoenwaelder    Expires June 14, 2015                [Page 44]


Internet-Draft    NETCONF/RESTCONF Server Config Models    December 2014


   o  Added trusted-ca-certs and trusted-client-certs objects into the
      ietf-system-tls-auth module

B.2.  01 to 02

   o  removed the "one-to-many" construct

   o  removed "address" as a key field

   o  removed "network-manager" terminology

   o  moved open issues to github issues

   o  brought TLS client auth back into model

B.3.  02 to 03

   o  fixed tree diagrams and surrounding text

B.4.  03 to 04

   o  reduced the number of grouping statements

   o  removed psk-maps and associated feature statements

   o  added ability for listen/call-home instances to specify which
      host-keys/certificates (of all listed) to use

   o  clarified that last-connected should span reboots

   o  added missing "objectives" for selecting which keys to use,
      authenticating client-certificates, and mapping authenticated
      client-certificates to usernames

   o  clarified indirect client certificate authentication

   o  added keep-alive configuration for listen connections

   o  added global-level NETCONF session parameters

B.5.  04 to 05

   o  Removed all refs to the old ietf-system-tls-auth module

   o  Removed YANG 1.1 style if-feature statements (loss some
      expressiveness)





Watsen & Schoenwaelder    Expires June 14, 2015                [Page 45]


Internet-Draft    NETCONF/RESTCONF Server Config Models    December 2014


   o  Removed the read-only (config false) lists of SSH host-keys and
      TLS certs

   o  Added an if-feature around session-options container

   o  Added ability to configure trust-anchors for SSH X.509 client
      certs

   o  Now imports by revision, per best practice

   o  Added support for RESTCONF server

   o  Added RFC Editor instructions

Appendix C.  Open Issues

   Please see: https://github.com/netconf-wg/server-model/issues.

Authors' Addresses

   Kent Watsen
   Juniper Networks

   EMail: kwatsen@juniper.net


   Juergen Schoenwaelder
   Jacobs University Bremen

   EMail: j.schoenwaelder@jacobs-university.de





















Watsen & Schoenwaelder    Expires June 14, 2015                [Page 46]


Html markup produced by rfcmarkup 1.129c, available from https://tools.ietf.org/tools/rfcmarkup/