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:

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

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

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

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

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.

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

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:

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.

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 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.

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

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

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 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 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.

    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)
      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";
        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";
        }
        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;
            }
          }
        }
        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
                "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 {
                  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.";
              }
            }
            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;
      }
    }
  }


  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
          "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
          "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
       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 {
        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

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

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.

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
    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 {
    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
          }
        }
      }
    }
  }

  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.";
            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
                    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.";
          }
          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
       "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
      "";
    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.

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 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:

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

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

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:

   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.
[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", Internet-Draft draft-ieft-netconf-call-home-02, 2014.
[draft-ietf-netconf-restconf] Bierman, A., Bjorklund, M. and K. Watsen, "RESTCONF Protocol", Internet-Draft draft-ieft-netconf-restconf-04, 2014.
[draft-ietf-netconf-rfc5539bis] Badra, M., Luchuk, A. and J. Schönwälder, "Using the NETCONF Protocol over Transport Layer Security (TLS)", Internet-Draft draft-ietf-netconf-rfc5539bis-06, 2014.
[draft-ietf-netmod-snmp-cfg] Bjorklund, M. and J. Schönwälder, "A YANG Data Model for SNMP Configuration", Internet-Draft draft-ietf-netmod-snmp-cfg-08, September 2014.

10.2. Informative References

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

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>
      <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>
            <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>

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

B.2. 01 to 02

B.3. 02 to 03

B.4. 03 to 04

B.5. 04 to 05

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