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

Versions: 00 01

NETCONF Working Group                                          K. Watsen
Internet-Draft                                          Juniper Networks
Intended status: Standards Track                        J. Schoenwaelder
Expires: August 18, 2014                        Jacobs University Bremen
                                                       February 14, 2014


           A YANG Data Model for NETCONF Server Configuration
                    draft-kwatsen-netconf-server-01

Abstract

   This draft defines a NETCONF server configuration data model.  This
   data model enables configuration of the NETCONF service itself,
   including which transports it supports, what ports they listen on,
   whether they support device-initiated connections, and associated
   parameters.

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 August 18, 2014.

Copyright Notice

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












Watsen & Schoenwaelder   Expires August 18, 2014                [Page 1]


Internet-Draft      YANG NETCONF Server Configuration      February 2014


   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  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Terminology . . . . . . . . . . . . . . . . . . . . . . .   3
     1.2.  Tree Diagrams . . . . . . . . . . . . . . . . . . . . . .   3
   2.  Objectives  . . . . . . . . . . . . . . . . . . . . . . . . .   3
     2.1.  Support all NETCONF Transports  . . . . . . . . . . . . .   3
     2.2.  Align Transport-Specific Configurations . . . . . . . . .   4
     2.3.  Support Transport-Independent Configuration . . . . . . .   4
     2.4.  Support both Inbound and Outbound Connections . . . . . .   4
     2.5.  For Device-Initiated Outbound Connections . . . . . . . .   4
       2.5.1.  Support More than One Application . . . . . . . . . .   4
       2.5.2.  Support Applications Having More than One Server  . .   4
       2.5.3.  Support a Reconnection Strategy . . . . . . . . . . .   5
       2.5.4.  Support both Persistent and Periodic Connections  . .   5
       2.5.5.  Keep-Alives for Persistent Connections  . . . . . . .   5
       2.5.6.  Customizations for Periodic Connections . . . . . . .   5
   3.  Data Model Overview . . . . . . . . . . . . . . . . . . . . .   6
     3.1.  The "listen" Grouping . . . . . . . . . . . . . . . . . .   6
     3.2.  The "call-home" Grouping  . . . . . . . . . . . . . . . .   6
     3.3.  The SSH Subtree . . . . . . . . . . . . . . . . . . . . .   7
     3.4.  The TLS Subtree . . . . . . . . . . . . . . . . . . . . .   8
   4.  NETCONF Server YANG Module  . . . . . . . . . . . . . . . . .   9
   5.  Security Considerations . . . . . . . . . . . . . . . . . . .  21
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  21
   7.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  21
   8.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  21
     8.1.  Normative References  . . . . . . . . . . . . . . . . . .  22
     8.2.  Informative References  . . . . . . . . . . . . . . . . .  22
   Appendix A.  Example: SSH . . . . . . . . . . . . . . . . . . . .  22
   Appendix B.  Example: TLS . . . . . . . . . . . . . . . . . . . .  23
   Appendix C.  Change Log . . . . . . . . . . . . . . . . . . . . .  25
     C.1.  00 to 01  . . . . . . . . . . . . . . . . . . . . . . . .  25
   Appendix D.  Open Issues  . . . . . . . . . . . . . . . . . . . .  25

1.  Introduction





Watsen & Schoenwaelder   Expires August 18, 2014                [Page 2]


Internet-Draft      YANG NETCONF Server Configuration      February 2014


   This draft defines a NETCONF [RFC6241] server configuration data
   model.  This data model enables configuration of the NETCONF service
   itself, including which transports it supports, what ports they
   listen on, whether they support device-initiated connections, 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 model 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).

   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 (":").

2.  Objectives

   The primary purpose of this YANG module is to enable the
   configuration of the NETCONF service on the device.  This scope
   includes both transport-independent and transport-specific
   configuration parameters.

2.1.  Support all NETCONF Transports

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

   Since implementations may not support all transports, the module
   should use YANG "feature" statements so that each implementation can
   advertise which transports it actually supports.





Watsen & Schoenwaelder   Expires August 18, 2014                [Page 3]


Internet-Draft      YANG NETCONF Server Configuration      February 2014


2.2.  Align Transport-Specific Configurations

   While each transport is unique in its protocol and may have some
   distinct configurations, there remains a significant overlap between
   them.  Thus the YANG module should use "grouping" statements so that
   the common aspects can be configured similarly.

2.3.  Support Transport-Independent Configuration

   Since some NETCONF server configurations may be independent of any
   transport, the module should define a location for these transport-
   independent values to be configured.

2.4.  Support both Inbound and Outbound Connections

   Historically, NETCONF only supported the device opening a port to
   listen for inbound client connections.  However, the NETCONF working
   group is actively defining support for devices to initiate outbound
   connections (e.g., "call home").  Thus, the module should enable the
   configuration of both inbound and outbound connections.

   Since implementations may not support both inbound and outbound
   connections, the module should use YANG "feature" statements so that
   each implementation can advertise the type of connections it actually
   supports.

2.5.  For Device-Initiated Outbound Connections

   The following objectives only pertain to support for device-initiated
   outbound connections.

2.5.1.  Support More than One Application

   A device may be managed by more than one northbound applications.
   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 management connections, it should be able to do
   so for more than one application.

2.5.2.  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 connections to
   the application, it should be able to connect to any of the
   applications servers.





Watsen & Schoenwaelder   Expires August 18, 2014                [Page 4]


Internet-Draft      YANG NETCONF Server Configuration      February 2014


2.5.3.  Support a Reconnection Strategy

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

   Note that 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 the device how to get connected to another server.

2.5.4.  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 are satisfied with periodic
   interactions and reduced resources required.  Therefore, when it is
   necessary for devices to initiate connections, the type of connection
   desired should be configured.

2.5.5.  Keep-Alives for Persistent Connections

   If a persistent connection is desired, it is the responsibility of
   the connection-initiator to actively test the connection for
   aliveness.  However, there is a balance between the frequency of the
   tests and the networking overhead they generate.  The appropriate
   balance can only be determined by the application, based on its
   interaction requirements.  Therefore, for persistent connections,
   keep-alive settings should be configurable on a per-application
   basis.

2.5.6.  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.  Note, this setting does not constrain how often the



Watsen & Schoenwaelder   Expires August 18, 2014                [Page 5]


Internet-Draft      YANG NETCONF Server Configuration      February 2014


   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.

   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.  Data Model Overview

3.1.  The "listen" Grouping

   To enable transports to configure listening on one or more ports in a
   common way, this grouping is defined.  Being a grouping enables each
   transport-specific data-model to augment it as needed (e.g., to
   specify a default for the "port" values), as well as enable
   implementations to advertise support for listening for inbound
   connections using a YANG feature.

   +--rw listen
      +--rw (one-or-many)?
         +--:(one-port)
         |  +--rw port?         inet:port-number
         +--:(many-ports)
            +--rw interface* [address]
               +--rw address    inet:ip-address
               +--rw port?      inet:port-number

3.2.  The "call-home" Grouping

   To enable transports to configure initiating connections to remote
   applications in a common way, this grouping is defined.  Being a
   grouping enables each transport-specific data-model to augment it as
   needed (e.g., to specify a default port value, lists of algorithms to
   advertise, etc.), as well as enable implementations to advertise
   support for listening for inbound connections using a YANG feature.

   +--rw call-home
      +--rw applications
         +--rw application* [name]
            +--rw name                  string
            +--rw description?          string
            +--rw servers
            |  +--rw server* [address]



Watsen & Schoenwaelder   Expires August 18, 2014                [Page 6]


Internet-Draft      YANG NETCONF Server Configuration      February 2014


            |     +--rw address    inet:host
            |     +--rw port?      inet:port-number
            +--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

3.3.  The SSH Subtree

   The SSH subtree uses both the "listen" and "call-home" groupings
   mentioned above.  Support for the SSH transport is advertised by the
   "ssh" feature, while listening for clients and calling home are
   advertised by the "inbound-ssh" and "outbound-ssh" features
   respectively.  The SSH subtree augments the "call-home" grouping by
   adding a "host-keys" container.  Also, though not visible in the tree
   output below, this subtree refines all the port values with a
   suitable default (i.e., 830).

   +--rw netconf
      +--rw ssh {ssh}?
         +--rw listen {inbound-ssh}?
         |  +--rw (one-or-many)?
         |     +--:(one-port)
         |     |  +--rw port?        inet:port-number
         |     +--:(many-ports)
         |        +--rw interface* [address]
         |           +--rw address    inet:ip-address
         |           +--rw port?      inet:port-number
         +--rw call-home {outbound-ssh}?
            +--rw applications
               +--rw application* [name]
                  +--rw name                  string
                  +--rw description?          string
                  +--rw servers
                  |  +--rw server* [address]
                  |     +--rw address    inet:host
                  |     +--rw port?      inet:port-number



Watsen & Schoenwaelder   Expires August 18, 2014                [Page 7]


Internet-Draft      YANG NETCONF Server Configuration      February 2014


                  +--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
                  +--rw host-keys
                     +--rw host-key* [name]
                        +--rw name    string

3.4.  The TLS Subtree

   The TLS subtree uses both the "listen" and "call-home" groupings
   mentioned above, while also defining containers for certificate and
   pre-shared key mappings.  Support for the TLS transport is advertised
   by the "tls" feature, while listening for clients and calling home
   are advertised by the "inbound-tls" and "outbound-tls" features
   respectively.  Also, though not visible in the tree output below,
   this submodule refines all the port values with a suitable defaults
   (e.g., 6513).

   +--rw netconf
      +--rw tls {tls}?
         +--rw listen {inbound-tls}?
         |  +--rw (one-or-many)?
         |     +--:(one-port)
         |     |  +--rw port?        inet:port-number
         |     +--:(many-ports)
         |        +--rw interface* [address]
         |           +--rw address    inet:ip-address
         |           +--rw port?      inet:port-number
         +--rw call-home {outbound-tls}?
         |  +--rw applications
         |     +--rw application* [name]
         |        +--rw name                  string
         |        +--rw description?          string
         |        +--rw servers
         |        |  +--rw server* [address]
         |        |     +--rw address    inet:host



Watsen & Schoenwaelder   Expires August 18, 2014                [Page 8]


Internet-Draft      YANG NETCONF Server Configuration      February 2014


         |        |     +--rw port?      inet:port-number
         |        +--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
         +--rw cert-maps {tls-map-certificates}?
         |  +--rw cert-to-name* [id]
         |     +--rw id             uint32
         |     +--rw fingerprint    x509c2n:tls-fingerprint
         |     +--rw map-type       identityref
         |     +--rw name           string
         +--rw psk-maps {tls-map-pre-shared-keys}?
            +--rw psk-map* [psk-identity]
               +--rw psk-identity        string
               +--rw user-name           nacm:user-name-type
               +--rw not-valid-before?   yang:date-and-time
               +--rw not-valid-after?    yang:date-and-time
               +--rw key                 yang:hex-string

4.  NETCONF Server YANG Module

   This YANG module imports YANG extensions from [RFC6536], and imports
   YANG types from [RFC6991] and a YANG grouping from
   [I-D.ietf-netmod-snmp-cfg].

   module ietf-netconf-server {

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

     import ietf-yang-types {
       prefix yang;                // RFC 6991
     }
     import ietf-inet-types {
       prefix inet;                // RFC 6991
     }
     import ietf-x509-cert-to-name {



Watsen & Schoenwaelder   Expires August 18, 2014                [Page 9]


Internet-Draft      YANG NETCONF Server Configuration      February 2014


       prefix x509c2n;             // I-D.ietf-netconf-rfc5539bis
     }
     import ietf-netconf-acm {
       prefix nacm;                // RFC 6536
     }

     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: Bert Wijnen
                 <mailto:bertietf@bwijnen.net>

       Editor:   Juergen Schoenwaelder
                 <mailto:j.schoenwaelder@jacobs-university.de>

                 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.

       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.";
     // RFC Ed.: replace XXXX with actual RFC number and
     // remove this note

     // RFC Ed.: please update the date to the date of publication

     revision "2014-01-24" {
       description



Watsen & Schoenwaelder   Expires August 18, 2014               [Page 10]


Internet-Draft      YANG NETCONF Server Configuration      February 2014


        "Initial version";
       reference
        "RFC XXXX: A YANG Data Model for NETCONF Server Configuration";
     }

     /*
      * Features
      */

     feature ssh {
       description
        "A server implements this feature if it supports NETCONF
         over Secure Shell (SSH).";
       reference
        "RFC 6242: Using the NETCONF Protocol over Secure Shell (SSH)";
     }

     feature inbound-ssh {
       description
        "The inbound-ssh feature indicates that the server can
         open a port to listen for incoming client connections.";
     }

     feature outbound-ssh {
       description
        "The outbound-ssh feature indicates that the server can
         connect to a client.";
       reference
        "RFC XXXX: Reverse Secure Shell (Reverse SSH)";
     }

     feature tls {
       description
        "A server implements this feature if it supports NETCONF
         over Transport Layer Security (TLS).";
       reference
        "RFC XXXX: NETCONF over Transport Layer Security (TLS)";
     }

     feature inbound-tls {
       description
        "The inbound-tls feature indicates that the server can
         open a port to listen for incoming client connections.";
     }

     feature outbound-tls {
       description
        "The outbound-tls feature indicates that the server can



Watsen & Schoenwaelder   Expires August 18, 2014               [Page 11]


Internet-Draft      YANG NETCONF Server Configuration      February 2014


         connect to a client.";
     }

     feature tls-map-certificates {
       description
        "The tls-map-certificates feature indicates that the
         server implements mapping X.509 certificates to NETCONF
         usernames.";
     }

     feature tls-map-pre-shared-keys {
       description
        "The tls-map-pre-shared-keys feature indicates that the
         server implements mapping TLS pre-shared keys to NETCONF
         usernames.";
     }

     /*
      * Groupings
      */

      grouping listen-config {
        description
         "Provides a choice of configuring one of more ports
          to listen for incoming client connections.";

        choice one-or-many {
          default one-port;
          case one-port {
            leaf port {
              type inet:port-number;
              description
               "The port number the server listens on on all
                interfaces.";
            }
          }

          case many-ports {
            list interface {
              key "address";
              leaf address {
                type inet:ip-address;
                  mandatory true;
                  description
                   "The local IP address of the interface to listen
                    on.";
                }
                leaf port {



Watsen & Schoenwaelder   Expires August 18, 2014               [Page 12]


Internet-Draft      YANG NETCONF Server Configuration      February 2014


                  type inet:port-number;
                  description
                   "The local port number on this interface the
                    server listens on.";
                }
              }
            }
         }
      }

     grouping call-home-config {

       container applications {
         description
          "A list of applications the device iniates connections
           to. The configuration for each application specifies
           its details, including its servers, the type of
           connection to maintain, and the reconnection strategy
           to use.";

         list application {
           key name;
   //        min-elements 1;  // this forces <call-home>?!
           leaf name {
             type string {
               length 1..64;  // XXX why these limits?
             }
             mandatory true;
             description
              "An arbitrary name for the application the device
               is connecting to.";
           }
           leaf description {
             type string;
             description
               "An optional description for the application.";
           }
           container servers {
             description
              "An ordered listing of the application's servers
               that the device should attempt connecting to.";
             list server {
               key address;
               min-elements 1;
               ordered-by user;
               leaf address {
                 type inet:host;
                 mandatory true;



Watsen & Schoenwaelder   Expires August 18, 2014               [Page 13]


Internet-Draft      YANG NETCONF Server Configuration      February 2014


                 description
                  "The address or domain-name of the server.";
               }
               leaf port {
                 type inet:port-number;
                 description
                  "The IP port for this server. The device will use
                   the IANA-assigned well-known port if not specified.";
               }
             }
           }
           container connection-type {
             description
              "Indicates the application's preference for how the
               device's connection is maintained.";
             choice connection-type {
               default persistent-connection;

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

                     This connection type minimizes any
                     application-to-server data-transfer delay,
                     albeit at the expense of holding resources
                     longer.";
                   container keep-alives {
                     leaf interval-secs {
                       type uint8;
                       units seconds;
                       default 15;
                       description
                        "Sets a timeout interval in seconds after which
                         if no data has been received from the
                         application, a message will be sent to request
                         a response from the application.  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



Watsen & Schoenwaelder   Expires August 18, 2014               [Page 14]


Internet-Draft      YANG NETCONF Server Configuration      February 2014


                         be sent without receiving any data from the
                         application before assuming the application is
                         no longer alive.  If this threshold is reached,
                         the transport-level connection will be
                         disconnected (thus triggering the reconnection
                         strategy).  The interval timer is reset after
                         each transmission, thus an unresponsive
                         application will be disconnected after
                         approximately count-max * interval-secs
                         seconds.";
                     }
                   }
                 }
               }

               case periodic-connection {
                 container periodic {
                   description
                    "Periodically connect to application, using the
                     reconnection strategy, so it can flush any pending
                     data it may be holding. This connection type
                     minimizes resources held open, albeit at the
                     expense of longer application-to-server
                     data-transfer delay.  Note that for
                     server-to-application data, the data should be
                     sent immediately, connecting to application first
                     if not already.";
                   leaf timeout-mins {
                     type uint8;
                     units minutes;
                     default 5;
                     description
                      "The maximum amount of unconnected time the
                       device will wait until establishing a
                       connection to the application again. The
                       device may establish a connection before this
                       time if it has data it needs to send to the
                       application. 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 device should wait after
                       last receiving data from or sending data to the



Watsen & Schoenwaelder   Expires August 18, 2014               [Page 15]


Internet-Draft      YANG NETCONF Server Configuration      February 2014


                       application before closing its connection to it.
                       This is an optimization to prevent unnecessary
                       connections.";
                   }
                 }
               }
             }
           }

           // XXX
           // Should we have something smarter as the reconnect
           // strategy, e.g. an exponential backoff?

           container reconnect-strategy {
             description
              "The reconnection strategy guides how a device reconnects
               to an application, after losing a connection to it, even
               if due to a reboot.  The device starts with the specified
               server, tries to connect to it count-max times, waiting
               interval-secs between each connection attempt, before
               trying the next server in the list (round robin).";
             leaf start-with {
               type enumeration {
                 enum first-listed { value 1; }
                 enum last-connected { value 2; }
               }
               default first-listed;
               description
                "Specifies which of the application's servers the
                 device should start with when trying to connect to
                 the application. In the case of newly configured
                 application, the first server listed shall be
                 considered last-connected.";
             }
             leaf interval-secs {
               type uint8;
               units seconds;
               default 5;
               description
                "Specifies the time delay between connection attempts
                 to the same server.  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 device tries to



Watsen & Schoenwaelder   Expires August 18, 2014               [Page 16]


Internet-Draft      YANG NETCONF Server Configuration      February 2014


                 connect to a specific server before moving on to
                 the next server in the list (round robin).";
             }
           }
         }
       }
     }


     grouping ssh-config {
        description
         "Provides a reusable grouping for all the ssh config.  This
          is done primarily to enable external modules to reference
          this definition in a &quot;uses&quot; statement.";

         container listen {
           if-feature inbound-ssh;
           description
            "Provides the configuration of the NETCONF server to
             open one or more ports to listen for incoming client
             connections.";
           uses listen-config {
             refine one-or-many/one-port/port {
               default 830;
             }
             refine one-or-many/many-ports/interface/port {
               default 830;
             }
           }
         }

         container call-home {
           if-feature outbound-ssh;
           description
            "Provides the configuration of the NETCONF call-home
             clients to connect to, the overall call-home policy,
             and the reconnect strategy.";
           uses call-home-config {
             augment applications/application {
               container host-keys {
                 description
                  "An ordered listing of the SSH host keys the
                   device should advertise to the application.";
                 list host-key {
                   key name;
                   min-elements 1;
                   ordered-by user;
                   leaf name {



Watsen & Schoenwaelder   Expires August 18, 2014               [Page 17]


Internet-Draft      YANG NETCONF Server Configuration      February 2014


                     type string {
                       length 1..64; // XXX why this limit?
                     }
                     mandatory true;
                     description
                      "The name of a host key the device should
                       advertise during the SSH key exchange.";
                   }
                 }
               }
             }
           }
         }
      }

     grouping tls-config {
        description
         "Provides a reusable grouping for all the tls config.  This
          is done primarily to enable external modules to reference
          this definition in a &quot;uses&quot; statement.";

         container listen {
           if-feature inbound-tls;
           description
            "Provides the configuration of the NETCONF server to
             open one or more ports to listen for incoming client
             connections.";
           uses listen-config {
             refine one-or-many/one-port/port {
               default 6513;
             }
             refine one-or-many/many-ports/interface/port {
               default 6513;
             }
           }
         }

         container call-home {
           if-feature outbound-tls;
           description
            "Provides the configuration of the NETCONF call-home
             clients to connect to, the overall call-home policy,
             and the reconnect strategy.";
           uses call-home-config;
         }

         /*
          * Objects for deriving NETCONF usernames from X.509



Watsen & Schoenwaelder   Expires August 18, 2014               [Page 18]


Internet-Draft      YANG NETCONF Server Configuration      February 2014


          * certificates.
          */

         container cert-maps {
           if-feature tls-map-certificates;
           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.";
         }

         /*
          * Objects for deriving NETCONF usernames from TLS
          * pre-shared keys.
          */

         container psk-maps {
           if-feature tls-map-pre-shared-keys;
           description
            "During the TLS Handshake, the client indicates which
             key to use by including a PSK identity in the TLS
             ClientKeyExchange message. On the server side, this
             PSK identity is used to look up an entry in the psk-map
             list. If such an entry is found, and the pre-shared keys
             match, then the client is authenticated. The server uses
             the value from the user-name leaf in the psk-map list as
             the NETCONF username.  If the server cannot find an entry
             in the psk-map list, or if the pre-shared keys do not
             match, then the server terminates the connection.";
           reference
            "RFC 4279: Pre-Shared Key Ciphersuites for Transport Layer
                       Security (TLS)";

           list psk-map {
             key psk-identity;

             leaf psk-identity {
               type string;
               description
                "The PSK identity encoded as a UTF-8 string. For
                 details how certain common PSK identity formats can
                 be encoded in UTF-8, see section 5.1. of RFC 4279.";
               reference



Watsen & Schoenwaelder   Expires August 18, 2014               [Page 19]


Internet-Draft      YANG NETCONF Server Configuration      February 2014


                "RFC 4279: Pre-Shared Key Ciphersuites for Transport
                           Layer Security (TLS)";
             }
             leaf user-name {
               type nacm:user-name-type;
               mandatory true;
               description
                "The NETCONF username associated with this PSK
                 identity.";
             }
             leaf not-valid-before {
               type yang:date-and-time;
               description
                "This PSK identity is not valid before the given date
                 and time.";
             }
             leaf not-valid-after {
               type yang:date-and-time;
               description
                "This PSK identity is not valid after the given date
                 and time.";
             }
             leaf key {
               type yang:hex-string;
               mandatory true;
               nacm:default-deny-all;
               description
                 "The key associated with the PSK identity";
               reference
                 "RFC 4279: Pre-Shared Key Ciphersuites for Transport
                  Layer Security (TLS)";
             }
           }
         }
      }


     /*
      * Configuration data nodes
      */

     container netconf {
       description
        "Top-level container for NETCONF server related
         configuration objects.";

       container ssh {
         if-feature ssh;



Watsen & Schoenwaelder   Expires August 18, 2014               [Page 20]


Internet-Draft      YANG NETCONF Server Configuration      February 2014


           uses ssh-config;
       }

       container tls {
         if-feature tls;
           uses tls-config;
       }

     }
   }

5.  Security Considerations

   This document defines a YANG modules to configure NETCONF's SSH and
   TLS transports.  Please see the Security Considerations section in
   those RFCs for transport-specific issues.

6.  IANA Considerations

   This document registers one URIs in the IETF XML registry [RFC2119].
   Following the format in [RFC3688], the following registration is
   requested to be made.

      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.

   This document registers one YANG module in the YANG Module Names
   registry [RFC6020].

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

7.  Acknowledgements

   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.

8.  References









Watsen & Schoenwaelder   Expires August 18, 2014               [Page 21]


Internet-Draft      YANG NETCONF Server Configuration      February 2014


8.1.  Normative References

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

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

   [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.

   [I-D.ietf-netmod-snmp-cfg]
              Bjorklund, M. and J. Schoenwaelder, "A YANG Data Model for
              SNMP Configuration", draft-ietf-netmod-snmp-cfg-03 (work
              in progress), November 2013.

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

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

   [I-D.ietf-netconf-rfc5539bis]
              Badra, M., Luchuk, A., and J. Schoenwaelder, "Using the
              NETCONF Protocol over Transport Layer Security (TLS) ",
              draft-ietf-netconf-rfc5539bis-04 (work in progress),
              October 2013.

8.2.  Informative References

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

Appendix A.  Example: SSH

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

       <listen>
         <port>831</port>
       </listen>




Watsen & Schoenwaelder   Expires August 18, 2014               [Page 22]


Internet-Draft      YANG NETCONF Server Configuration      February 2014


       <call-home>
         <applications>
           <application>
             <name>config-mgr</name>
             <description>
                This entry requests the device to periodically
                connect to the Configuration Manager application
             </description>
             <servers>
                <server>
                   <address>config-mgr1.example.com</address>
                </server>
                <server>
                   <address>config-mgr2.example.com</address>
                </server>
             </servers>
             <connection-type>
               <periodic>
                 <timeout-mins>5</timeout-mins>
                 <linger-secs>10</linger-secs>
               </periodic>
             </connection-type>
             <reconnect-strategy>
                <start-with>last-connected</start-with>
                <interval-secs>10</interval-secs>
                <count-max>3</count-max>
             </reconnect-strategy>
             <host-keys>
                <host-key>
                   <name>ssh_host_key_cert</name>
                </host-key>
                <host-key>
                   <name>ssh_host_key_cert2</name>
                </host-key>
             </host-keys>
           </application>
         </applications>
       </call-home>

     </ssh>
   </netconf>

Appendix B.  Example: TLS

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

       <listen>



Watsen & Schoenwaelder   Expires August 18, 2014               [Page 23]


Internet-Draft      YANG NETCONF Server Configuration      February 2014


         <interface>
           <address>192.0.2.1</address>
           <port>6514</port>
         </interface>
       </listen>

       <call-home>
         <applications>
           <application>
             <name>log-monitor</name>
             <description>
                This entry requests the device to maintain a
                persistent connect to the Log Monitor application
             </description>
             <servers>
                <server>
                   <address>log-monitor1.example.com</address>
                </server>
                <server>
                   <address>log-monitor2.example.com</address>
                </server>
             </servers>
             <connection-type>
               <persistent>
                 <keep-alives>
                   <interval-secs>5</interval-secs>
                   <count-max>3</count-max>
                 </keep-alives>
               </persistent>
             </connection-type>
             <reconnect-strategy>
                <start-with>first-listed</start-with>
                <interval-secs>10</interval-secs>
                <count-max>4</count-max>
             </reconnect-strategy>
           </application>
         </applications>
       </call-home>

       <cert-maps>
         <!-- Use a subject alt name field of a specific
              certificate as the NC username. -->
         <cert-to-name>
           <id>1</id>
           <fingerprint>11:0A:05:11:00</fingerprint>
           <map-type>x509c2n:san-any</map-type>
         </cert-to-name>
         <!-- Map a specific certificate to the NC username



Watsen & Schoenwaelder   Expires August 18, 2014               [Page 24]


Internet-Draft      YANG NETCONF Server Configuration      February 2014


              'Joe Cool'. -->
         <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>

       <psk-maps>
         <psk-map>
           <psk-identity>a8gc8]klh59</psk-identity>
           <user-name>admin</user-name>
           <not-valid-before>2013-01-01T00:00:00Z</not-valid-before>
           <not-valid-after>2014-01-01T00:00:00Z</not-valid-after>
         </psk-map>
       </psk-maps>

     </tls>
   </netconf>

Appendix C.  Change Log

C.1.  00 to 01

   o  Restructured YANG module slightly, to provide groupings useful to
      the ZeroTouch draft.

Appendix D.  Open Issues

   o  NETCONF implementations typically have config parameters such as
      session timeouts or hello timeouts.  Shall they be included in
      this model?

   o  Do we need knobs to enable/disable call-home without the need to
      remove all the call-home client configuration?

   o  Do we need something equivalent to the host-keys in the TLS
      configuration subtree?

Authors' Addresses

   Kent Watsen
   Juniper Networks

   EMail: kwatsen@juniper.net





Watsen & Schoenwaelder   Expires August 18, 2014               [Page 25]


Internet-Draft      YANG NETCONF Server Configuration      February 2014


   Juergen Schoenwaelder
   Jacobs University Bremen

   EMail: j.schoenwaelder@jacobs-university.de















































Watsen & Schoenwaelder   Expires August 18, 2014               [Page 26]


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