NETCONF Working Group K. Watsen
Internet-Draft Juniper Networks
Intended status: Standards Track G. Wu
Expires: December 6, 2018 Cisco Networks
June 4, 2018

RESTCONF Client and Server Models
draft-ietf-netconf-restconf-client-server-06

Abstract

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

Editorial Note (To be removed by RFC Editor)

This draft contains many placeholder values that need to be replaced with finalized values at the time of publication. This note summarizes all of the substitutions that are needed. No other RFC Editor instructions are specified elsewhere in this document.

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

Artwork in this document contains shorthand references to drafts in progress. 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 Appendix section is 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 https://datatracker.ietf.org/drafts/current/.

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

This Internet-Draft will expire on December 6, 2018.

Copyright Notice

Copyright (c) 2018 IETF Trust and the persons identified as the document authors. All rights reserved.

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


Table of Contents

1. Introduction

This document defines two YANG [RFC7950] modules, one module to configure a RESTCONF client and the other module to configure a RESTCONF server [RFC8040]. Both modules support the TLS [RFC5246] transport protocol with both standard RESTCONF and RESTCONF Call Home connections [RFC8071].

1.1. Terminology

The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all capitals, as shown here.

2. The RESTCONF Client Model

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

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

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

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

2.1. Tree Diagram

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


[Note: '\' line wrapping for formatting only]

module: ietf-restconf-client
  +--rw restconf-client
     +--rw initiate! {initiate}?
     |  +--rw restconf-server* [name]
     |     +--rw name         string
     |     +--rw endpoints
     |        +--rw endpoint* [name]
     |           +--rw name                  string
     |           +--rw (transport)
     |           |  +--:(tls) {tls-initiate}?
     |           |     +--rw tls
     |           |        +--rw address            inet:host
     |           |        +--rw port?              inet:port-number
     |           |        +--rw client-identity
     |           |        |  +--rw (auth-type)
     |           |        |     +--:(certificate)
     |           |        |        +--rw certificate
     |           |        |           +--rw (local-or-keystore)
     |           |        |              +--:(local)
     |           |        |              |  +--rw algorithm
     |           |        |              |  |       ct:key-algorithm\
-ref
     |           |        |              |  +--rw public-key
     |           |        |              |  |       binary
     |           |        |              |  +--rw private-key
     |           |        |              |  |       union
     |           |        |              |  +--rw cert
     |           |        |              |  |       ct:end-entity-ce\
rt-cms
     |           |        |              |  +---n certificate-expira\
tion
     |           |        |              |     +-- expiration-date?
     |           |        |              |             yang:date-and\
-time
     |           |        |              +--:(keystore)
     |           |        |                       {keystore-implemen\
ted}?
     |           |        |                 +--rw reference
     |           |        |                         ks:asymmetric-ke\
y-certificate-ref
     |           |        +--rw server-auth
     |           |        |  +--rw pinned-ca-certs?
     |           |        |  |       ta:pinned-certificates-ref
     |           |        |  +--rw pinned-server-certs?
     |           |        |          ta:pinned-certificates-ref
     |           |        +--rw hello-params
     |           |                {tls-client-hello-params-config}?
     |           |           +--rw tls-versions
     |           |           |  +--rw tls-version*   identityref
     |           |           +--rw cipher-suites
     |           |              +--rw cipher-suite*   identityref
     |           +--rw connection-type
     |           |  +--rw (connection-type)?
     |           |     +--:(persistent-connection)
     |           |     |  +--rw persistent!
     |           |     |     +--rw idle-timeout?   uint32
     |           |     |     +--rw keep-alives
     |           |     |        +--rw max-wait?       uint16
     |           |     |        +--rw max-attempts?   uint8
     |           |     +--:(periodic-connection)
     |           |        +--rw periodic!
     |           |           +--rw idle-timeout?        uint16
     |           |           +--rw reconnect-timeout?   uint16
     |           +--rw reconnect-strategy
     |              +--rw start-with?     enumeration
     |              +--rw max-attempts?   uint8
     +--rw listen! {listen}?
        +--rw idle-timeout?   uint16
        +--rw endpoint* [name]
           +--rw name         string
           +--rw (transport)
              +--:(tls) {tls-listen}?
                 +--rw tls
                    +--rw address?           inet:ip-address
                    +--rw port?              inet:port-number
                    +--rw client-identity
                    |  +--rw (auth-type)
                    |     +--:(certificate)
                    |        +--rw certificate
                    |           +--rw (local-or-keystore)
                    |              +--:(local)
                    |              |  +--rw algorithm
                    |              |  |       ct:key-algorithm-ref
                    |              |  +--rw public-key
                    |              |  |       binary
                    |              |  +--rw private-key
                    |              |  |       union
                    |              |  +--rw cert
                    |              |  |       ct:end-entity-cert-cms\

                    |              |  +---n certificate-expiration
                    |              |     +-- expiration-date?
                    |              |             yang:date-and-time
                    |              +--:(keystore)
                    |                       {keystore-implemented}?
                    |                 +--rw reference
                    |                         ks:asymmetric-key-cert\
ificate-ref
                    +--rw server-auth
                    |  +--rw pinned-ca-certs?
                    |  |       ta:pinned-certificates-ref
                    |  +--rw pinned-server-certs?
                    |          ta:pinned-certificates-ref
                    +--rw hello-params
                            {tls-client-hello-params-config}?
                       +--rw tls-versions
                       |  +--rw tls-version*   identityref
                       +--rw cipher-suites
                          +--rw cipher-suite*   identityref

2.2. Example Usage

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

This example is consistent with the examples presented in Section 2.2 of [I-D.ietf-netconf-keystore].


[Note: '\' line wrapping for formatting only]

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

  <!-- RESTCONF servers to initiate connections to -->
  <initiate>
    <restconf-server>
      <name>corp-fw1</name>
        <endpoints>
          <endpoint>
            <name>corp-fw1.example.com</name>
            <tls>
              <address>corp-fw1.example.com</address>
              <client-identity>
                <certificate>
                  <algorithm xmlns:ct="urn:ietf:params:xml:ns:yang:i\
etf-crypto-types">ct:secp521r1</algorithm>
                  <private-key>base64encodedvalue==</private-key>
                  <public-key>base64encodedvalue==</public-key>
                  <cert>base64encodedvalue==</cert>
                </certificate>
              </client-identity>
              <server-auth>
                <pinned-ca-certs>explicitly-trusted-server-ca-certs<\
/pinned-ca-certs>
                <pinned-server-certs>explicitly-trusted-server-certs\
</pinned-server-certs>
              </server-auth>
            </tls>
          </endpoint>
          <endpoint>
            <name>corp-fw2.example.com</name>
            <tls>
              <address>corp-fw2.example.com</address>
              <client-identity>
                <certificate>
                  <algorithm xmlns:ct="urn:ietf:params:xml:ns:yang:i\
etf-crypto-types">ct:secp521r1</algorithm>
                  <private-key>base64encodedvalue==</private-key>
                  <public-key>base64encodedvalue==</public-key>
                  <cert>base64encodedvalue==</cert>
                </certificate>
              </client-identity>
              <server-auth>
                <pinned-ca-certs>explicitly-trusted-server-ca-certs<\
/pinned-ca-certs>
                <pinned-server-certs>explicitly-trusted-server-certs\
</pinned-server-certs>
              </server-auth>
            </tls>
          </endpoint>
        </endpoints>
    </restconf-server>
  </initiate>

  <!-- endpoints to listen for RESTCONF Call Home connections on -->\

  <listen>
    <endpoint>
      <name>Intranet-facing listener</name>
      <tls>
        <address>11.22.33.44</address>
        <client-identity>
          <certificate>
            <algorithm xmlns:ct="urn:ietf:params:xml:ns:yang:ietf-cr\
ypto-types">ct:secp521r1</algorithm>
            <private-key>base64encodedvalue==</private-key>
            <public-key>base64encodedvalue==</public-key>
            <cert>base64encodedvalue==</cert>
          </certificate>
        </client-identity>
        <server-auth>
          <pinned-ca-certs>explicitly-trusted-server-ca-certs</pinne\
d-ca-certs>
          <pinned-server-certs>explicitly-trusted-server-certs</pinn\
ed-server-certs>
        </server-auth>
      </tls>
    </endpoint>
  </listen>
</restconf-client>

2.3. YANG Module

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

<CODE BEGINS> file "ietf-restconf-client@2018-06-04.yang"
module ietf-restconf-client {
  yang-version 1.1;

  namespace "urn:ietf:params:xml:ns:yang:ietf-restconf-client";
  prefix "rcc";

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

  import ietf-tls-client {
    prefix ts;
    revision-date 2018-06-04; // stable grouping definitions
    reference
      "RFC ZZZZ: YANG Groupings for TLS Clients and TLS Servers";
  }
 
  organization
   "IETF NETCONF (Network Configuration) Working Group";

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

    Author:   Kent Watsen
              <mailto:kwatsen@juniper.net>

    Author:   Gary Wu
              <mailto:garywu@cisco.com>";


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

    Copyright (c) 2017 IETF Trust and the persons identified as
    authors of the code. All rights reserved.

    Redistribution and use in source and binary forms, with or
    without modification, is permitted pursuant to, and subject
    to the license terms contained in, the Simplified BSD
    License set forth in Section 4.c of the IETF Trust's
    Legal Provisions Relating to IETF Documents
    (http://trustee.ietf.org/license-info).

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

  revision "2018-06-04" {
    description
     "Initial version";
    reference
     "RFC XXXX: RESTCONF Client and Server Models";
  }

  // Features

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

  feature tls-initiate {
    if-feature initiate;
    description
     "The ‘tls-initiate’ feature indicates that the RESTCONF client
      supports initiating TLS connections to RESTCONF servers. This
      feature exists as TLS might not be a mandatory to implement
      transport in the future.";
    reference
     "RFC 8040: RESTCONF Protocol";
  }

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

  feature tls-listen {
    if-feature listen;
    description
     "The ‘tls-listen’ feature indicates that the RESTCONF client
      supports opening a port to listen for incoming RESTCONF
      server call-home TLS connections.  This feature exists as
      TLS might not be a mandatory to implement transport in the
      future.";
    reference
     "RFC 8071: NETCONF Call Home and RESTCONF Call Home";
  }

  container restconf-client {
    uses restconf-client;
    description
      "Top-level container for RESTCONF client configuration.";
  }

  grouping restconf-client {
    description
      "Top-level grouping for RESTCONF client configuration.";

    container initiate {
      if-feature initiate;
      presence "Enables client to initiate TCP connections";
      description
        "Configures client initiating underlying TCP connections.";
      list restconf-server {
        key name;
        min-elements 1;
        description
          "List of RESTCONF servers the RESTCONF client is to
           initiate connections to in parallel.";
        leaf name {
          type string;
          description
            "An arbitrary name for the RESTCONF server.";
        }
        container endpoints {
          description
            "Container for the list of endpoints.";
          list endpoint {
            key name;
            min-elements 1;
            ordered-by user;
            description
              "A non-empty user-ordered list of endpoints for this
               RESTCONF client to try to connect to in sequence. 
               Defining more than one enables high-availability.";
            leaf name {
              type string;
              description
                "An arbitrary name for this endpoint.";
            }
            choice transport {
              mandatory true;
              description
                "Selects between available transports. This is a
                 'choice' statement so as to support additional
                 transport options to be augmented in.";
              case tls {
                if-feature tls-initiate;
                container tls {
                  description
                    "Specifies TLS-specific transport
                     configuration.";
                  leaf address {
                    type inet:host;
                    mandatory true;
                    description
                     "The IP address or hostname of the endpoint. 
                      If a domain name is configured, then the
                      DNS resolution should happen on each usage
                      attempt.  If the the DNS resolution results
                      in multiple IP addresses, the IP addresses
                      will be tried according to local preference
                      order until a connection has been established
                      or until all IP addresses have failed.";
                  }
                  leaf port {
                    type inet:port-number;
                    default 443;
                    description
                     "The IP port for this endpoint. The RESTCONF
                      client will use the IANA-assigned well-known
                      port for 'https' (443) if no value is
                      specified.";
                  }
                  uses ts:tls-client-grouping {
                    refine "client-identity/auth-type" {
                      mandatory true;
                      description
                        "RESTCONF clients MUST pass some
                         authentication credentials.";
                    }
                  }
                }
              } // end tls
            } // end transport
            container connection-type {
              description
               "Indicates the kind of connection to use.";
              choice connection-type {
                default persistent-connection;
                description
                  "Selects between available connection types.";
                case persistent-connection {
                  container persistent {
                    presence
                     "Indicates that a persistent connection is
                      to be maintained.";
                    description
                     "Maintain a persistent connection to the
                      RESTCONF server. If the connection goes down,
                      immediately start trying to reconnect to it,
                      using the reconnection strategy.  This
                      connection type minimizes any RESTCONF server
                      to RESTCONF client data-transfer delay, albeit
                      at the expense of holding resources longer.";
                    leaf idle-timeout {
                      type uint32;
                      units "seconds";
                      default 86400;  // one day;
                      description
                        "Specifies the maximum number of seconds
                         that the underlying TLS session may remain
                         idle.  A TLS session will be dropped if it
                         is idle for an interval longer than this
                         number of seconds.  If set to zero, then
                         the client will never drop a session
                         because it is idle.  Sessions that have
                         a notification subscription active are
                         never dropped.";
                    }
                    container keep-alives {
                      description
                        "Configures the keep-alive policy, to
                         proactively test the aliveness of the TLS
                         server.  An unresponsive TLS server will
                         be dropped after approximately max-attempts
                         * max-wait seconds.";
                      reference
                        "RFC 8071: NETCONF Call Home and RESTCONF
                         Call Home, Section 3.1, item S6";
                      leaf max-wait {
                        type uint16 {
                          range "1..max";
                        }
                        units seconds;
                        default 30;
                        description
                         "Sets the amount of time in seconds after
                          which if no data has been received from
                          the TLS server, a TLS-level message will
                          be sent to test the aliveness of the TLS
                          server.";
                      }
                      leaf max-attempts {
                        type uint8;
                        default 3;
                        description
                         "Sets the maximum number of sequential
                          keep-alive messages that can fail to
                          obtain a response from the TLS server
                          before assuming the TLS server is no
                          longer alive.";
                      }
                    }
                  }
                }
                case periodic-connection {
                  container periodic {
                    presence
                     "Indicates that a periodic connection is to be
                      maintained.";
                    description
                     "Periodically connect to the RESTCONF server,
                      so that, e.g., the RESTCONF client can
                      collect data (logs) from the RESTCONF server.
                      Once the connection is closed, for whatever
                      reason, the RESTCONF client will restart its
                      timer until the next connection.";
                    leaf idle-timeout {
                      type uint16;
                      units "seconds";
                      default 300; // five minutes
                      description
                        "Specifies the maximum number of seconds
                         that the underlying TLS session may remain
                         idle. A TLS session will be dropped if it
                         is idle for an interval longer than this
                         number of seconds If set to zero, then the
                         server will never drop a session because
                         it is idle.";
                    }
                    leaf reconnect-timeout {
                      type uint16 {
                        range "1..max";
                      }
                      units minutes;
                      default 60;
                      description
                       "Sets the maximum amount of unconnected time
                        the RESTCONF client will wait before re-
                        establishing a connection to the RESTCONF
                        server.  The RESTCONF client may initiate 
                        a connection before this time if desired
                        (e.g., to set configuration).";
                    }
                  }
                } // end periodic-connection
              } // end connection-type
            } // end connection-type
            container reconnect-strategy {
              description
               "The reconnection strategy directs how a RESTCONF
                client reconnects to a RESTCONF server, after
                discovering its connection to the server has
                dropped, even if due to a reboot.  The RESTCONF
                client starts with the specified endpoint and
                tries to connect to it max-attempts times before
                trying the next endpoint in the list (round
                robin).";
              leaf start-with {
                type enumeration {
                  enum first-listed {
                    description
                      "Indicates that reconnections should start
                       with the first endpoint listed.";
                  }
                  enum last-connected { 
                    description
                      "Indicates that reconnections should start
                       with the endpoint last connected to.  If
                       no previous connection has ever been
                       established, then the first endpoint
                       configured is used.   RESTCONF clients
                       SHOULD be able to remember the last 
                       endpoint connected to across reboots.";
                  }
                }
                default first-listed;
                description
                 "Specifies which of the RESTCONF server's
                  endpoints the RESTCONF client should start
                  with when trying to connect to the RESTCONF
                  server.";
              }
              leaf max-attempts {
                type uint8 {
                  range "1..max";
                }
                default 3;
                description
                 "Specifies the number times the RESTCONF client
                  tries to connect to a specific endpoint before
                  moving on to the next endpoint in the list
                  (round robin).";
              }
            } // end reconnect-strategy
          } // end endpoint
        } // end endpoints
      } // end restconf-server
    } // end initiate

    container listen {
      if-feature listen;
      presence "Enables client to accept call-home connections";
      description
        "Configures client accepting call-home TCP connections.";

      leaf idle-timeout {
        type uint16;
        units "seconds";
        default 3600; // one hour
        description
          "Specifies the maximum number of seconds that an
           underlying TLS session may remain idle. A TLS session
           will be dropped if it is idle for an interval longer
           than this number of seconds.  If set to zero, then
           the server will never drop a session because it is
           idle.  Sessions that have a notification subscription
           active are never dropped.";
      }

      list endpoint {
        key name;
        min-elements 1;
        description
          "List of endpoints to listen for RESTCONF connections.";
        leaf name {
          type string;
          description
            "An arbitrary name for the RESTCONF listen endpoint.";
        }
        choice transport {
          mandatory true;
          description
            "Selects between available transports. This is a
             'choice' statement so as to support additional
             transport options to be augmented in.";
          case tls {
            if-feature tls-listen;
            container tls {
              description
                "TLS-specific listening configuration for inbound
                 connections.";
              leaf address {
                type inet:ip-address;
                description
                 "The IP address to listen on for incoming call-
                  home connections.  The RESTCONF client will
                  listen on all configured interfaces if no
                  value is specified.  INADDR_ANY (0.0.0.0) or
                  INADDR6_ANY (0:0:0:0:0:0:0:0 a.k.a. ::) MUST
                  be used when the server is to listen on all
                  IPv4 or IPv6 addresses, respectively.";
              }   
              leaf port {
                type inet:port-number;
                default 4336;
                description
                 "The port number to listen on for call-home
                  connections. The RESTCONF client will listen
                  on the IANA-assigned well-known port for
                  'restconf-ch-tls' (4336) if no value is
                   specified.";
              }   
              uses ts:tls-client-grouping {
                refine "client-identity/auth-type" {
                  mandatory true;
                  description
                    "RESTCONF clients MUST pass some authentication
                     credentials.";
                }
              }
            }
          }
        } // end transport
      } // end endpoint
    } // end listen
  } // end restconf-client
}
<CODE ENDS>

3. The RESTCONF Server Model

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

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

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

3.1. Tree Diagram

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


[Note: '\' line wrapping for formatting only]

module: ietf-restconf-server
  +--rw restconf-server
     +--rw listen! {listen}?
     |  +--rw endpoint* [name]
     |     +--rw name         string
     |     +--rw (transport)
     |        +--:(tls) {tls-listen}?
     |           +--rw tls
     |              +--rw address?           inet:ip-address
     |              +--rw port?              inet:port-number
     |              +--rw server-identity
     |              |  +--rw (local-or-keystore)
     |              |     +--:(local)
     |              |     |  +--rw algorithm
     |              |     |  |       ct:key-algorithm-ref
     |              |     |  +--rw public-key                binary
     |              |     |  +--rw private-key               union
     |              |     |  +--rw cert
     |              |     |  |       ct:end-entity-cert-cms
     |              |     |  +---n certificate-expiration
     |              |     |     +-- expiration-date?
     |              |     |             yang:date-and-time
     |              |     +--:(keystore) {keystore-implemented}?
     |              |        +--rw reference
     |              |                ks:asymmetric-key-certificate-r\
ef
     |              +--rw client-auth
     |              |  +--rw pinned-ca-certs?
     |              |  |       ta:pinned-certificates-ref
     |              |  +--rw pinned-client-certs?
     |              |  |       ta:pinned-certificates-ref
     |              |  +--rw cert-maps
     |              |     +--rw cert-to-name* [id]
     |              |        +--rw id             uint32
     |              |        +--rw fingerprint
     |              |        |       x509c2n:tls-fingerprint
     |              |        +--rw map-type       identityref
     |              |        +--rw name           string
     |              +--rw hello-params
     |                      {tls-server-hello-params-config}?
     |                 +--rw tls-versions
     |                 |  +--rw tls-version*   identityref
     |                 +--rw cipher-suites
     |                    +--rw cipher-suite*   identityref
     +--rw call-home! {call-home}?
        +--rw restconf-client* [name]
           +--rw name                  string
           +--rw endpoints
           |  +--rw endpoint* [name]
           |     +--rw name         string
           |     +--rw (transport)
           |        +--:(tls) {tls-call-home}?
           |           +--rw tls
           |              +--rw address            inet:host
           |              +--rw port?              inet:port-number
           |              +--rw server-identity
           |              |  +--rw (local-or-keystore)
           |              |     +--:(local)
           |              |     |  +--rw algorithm
           |              |     |  |       ct:key-algorithm-ref
           |              |     |  +--rw public-key
           |              |     |  |       binary
           |              |     |  +--rw private-key
           |              |     |  |       union
           |              |     |  +--rw cert
           |              |     |  |       ct:end-entity-cert-cms
           |              |     |  +---n certificate-expiration
           |              |     |     +-- expiration-date?
           |              |     |             yang:date-and-time
           |              |     +--:(keystore) {keystore-implemented\
}?
           |              |        +--rw reference
           |              |                ks:asymmetric-key-certifi\
cate-ref
           |              +--rw client-auth
           |              |  +--rw pinned-ca-certs?
           |              |  |       ta:pinned-certificates-ref
           |              |  +--rw pinned-client-certs?
           |              |  |       ta:pinned-certificates-ref
           |              |  +--rw cert-maps
           |              |     +--rw cert-to-name* [id]
           |              |        +--rw id             uint32
           |              |        +--rw fingerprint
           |              |        |       x509c2n:tls-fingerprint
           |              |        +--rw map-type       identityref
           |              |        +--rw name           string
           |              +--rw hello-params
           |                      {tls-server-hello-params-config}?
           |                 +--rw tls-versions
           |                 |  +--rw tls-version*   identityref
           |                 +--rw cipher-suites
           |                    +--rw cipher-suite*   identityref
           +--rw connection-type
           |  +--rw (connection-type)?
           |     +--:(persistent-connection)
           |     |  +--rw persistent!
           |     |     +--rw idle-timeout?   uint32
           |     |     +--rw keep-alives
           |     |        +--rw max-wait?       uint16
           |     |        +--rw max-attempts?   uint8
           |     +--:(periodic-connection)
           |        +--rw periodic!
           |           +--rw idle-timeout?        uint16
           |           +--rw reconnect-timeout?   uint16
           +--rw reconnect-strategy
              +--rw start-with?     enumeration
              +--rw max-attempts?   uint8

3.2. Example Usage

The following example illustrates configuring a RESTCONF server to listen for RESTCONF client connections, as well as configuring call-home to one RESTCONF client.

This example is consistent with the examples presented in Section 2.2 of [I-D.ietf-netconf-keystore].


[Note: '\' line wrapping for formatting only]

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

  <!-- endpoints to listen for RESTCONF connections on -->
  <listen>
    <endpoint>
      <name>netconf/tls</name>
      <tls>
        <address>11.22.33.44</address>
        <server-identity>
          <algorithm xmlns:ct="urn:ietf:params:xml:ns:yang:ietf-cryp\
to-types">ct:secp521r1</algorithm>
          <private-key>base64encodedvalue==</private-key>
          <public-key>base64encodedvalue==</public-key>
          <cert>base64encodedvalue==</cert>
        </server-identity>
        <client-auth>
          <pinned-ca-certs>explicitly-trusted-client-ca-certs</pinne\
d-ca-certs>
          <pinned-client-certs>explicitly-trusted-client-certs</pinn\
ed-client-certs>
          <cert-maps>
            <cert-to-name>
              <id>1</id>
              <fingerprint>11:0A:05:11:00</fingerprint>
              <map-type>x509c2n:san-any</map-type>
            </cert-to-name>
            <cert-to-name>
              <id>2</id>
              <fingerprint>B3:4F:A1:8C:54</fingerprint>
              <map-type>x509c2n:specified</map-type>
              <name>scooby-doo</name>
            </cert-to-name>
          </cert-maps>
        </client-auth>
      </tls>
    </endpoint>
  </listen>

  <!-- call home to a RESTCONF client with two endpoints -->
  <call-home>
    <restconf-client>
      <name>config-manager</name>
      <endpoints>
        <endpoint>
          <name>east-data-center</name>
          <tls>
            <address>22.33.44.55</address>
            <server-identity>
              <algorithm xmlns:ct="urn:ietf:params:xml:ns:yang:ietf-\
crypto-types">ct:secp521r1</algorithm>
              <private-key>base64encodedvalue==</private-key>
              <public-key>base64encodedvalue==</public-key>
              <cert>base64encodedvalue==</cert>
            </server-identity>
            <client-auth>
              <pinned-ca-certs>explicitly-trusted-client-ca-certs</p\
inned-ca-certs>
              <pinned-client-certs>explicitly-trusted-client-certs</\
pinned-client-certs>
              <cert-maps>
                <cert-to-name>
                  <id>1</id>
                  <fingerprint>11:0A:05:11:00</fingerprint>
                  <map-type>x509c2n:san-any</map-type>
                </cert-to-name>
                <cert-to-name>
                  <id>2</id>
                  <fingerprint>B3:4F:A1:8C:54</fingerprint>
                  <map-type>x509c2n:specified</map-type>
                  <name>scooby-doo</name>
                </cert-to-name>
              </cert-maps>
            </client-auth>
          </tls>
        </endpoint>
        <endpoint>
          <name>west-data-center</name>
          <tls>
            <address>33.44.55.66</address>
            <server-identity>
              <algorithm xmlns:ct="urn:ietf:params:xml:ns:yang:ietf-\
crypto-types">ct:secp521r1</algorithm>
              <private-key>base64encodedvalue==</private-key>
              <public-key>base64encodedvalue==</public-key>
              <cert>base64encodedvalue==</cert>
            </server-identity>
            <client-auth>
              <pinned-ca-certs>explicitly-trusted-client-ca-certs</p\
inned-ca-certs>
              <pinned-client-certs>explicitly-trusted-client-certs</\
pinned-client-certs>
              <cert-maps>
                <cert-to-name>
                  <id>1</id>
                  <fingerprint>11:0A:05:11:00</fingerprint>
                  <map-type>x509c2n:san-any</map-type>
                </cert-to-name>
                <cert-to-name>
                  <id>2</id>
                  <fingerprint>B3:4F:A1:8C:54</fingerprint>
                  <map-type>x509c2n:specified</map-type>
                  <name>scooby-doo</name>
                </cert-to-name>
              </cert-maps>
            </client-auth>
          </tls>
        </endpoint>
      </endpoints>
      <connection-type>
        <periodic>
          <idle-timeout>300</idle-timeout>
          <reconnect-timeout>60</reconnect-timeout>
        </periodic>
      </connection-type>
      <reconnect-strategy>
        <start-with>last-connected</start-with>
        <max-attempts>3</max-attempts>
      </reconnect-strategy>
    </restconf-client>
  </call-home>
</restconf-server>

3.3. YANG Module

This YANG module has normative references to [RFC6991], [RFC7407], [RFC8040], [RFC8071], and [I-D.ietf-netconf-tls-client-server].

<CODE BEGINS> file "ietf-restconf-server@2018-06-04.yang"
module ietf-restconf-server {
  yang-version 1.1;

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

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

  import ietf-x509-cert-to-name {
    prefix x509c2n;
    reference
      "RFC 7407: A YANG Data Model for SNMP Configuration";
  }

  import ietf-tls-server {
    prefix ts;
    revision-date 2018-06-04; // stable grouping definitions
    reference
      "RFC ZZZZ: YANG Groupings for TLS Clients and TLS Servers";
  }

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

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

    Author:   Kent Watsen
              <mailto:kwatsen@juniper.net>
              
    Author:   Gary Wu
              <mailto:garywu@cisco.com>

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


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

    Copyright (c) 2017 IETF Trust and the persons identified as
    authors of the code. All rights reserved.

    Redistribution and use in source and binary forms, with or
    without modification, is permitted pursuant to, and subject
    to the license terms contained in, the Simplified BSD
    License set forth in Section 4.c of the IETF Trust's
    Legal Provisions Relating to IETF Documents
    (http://trustee.ietf.org/license-info).

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

  revision "2018-06-04" {
    description
     "Initial version";
    reference
     "RFC XXXX: RESTCONF Client and Server Models";
  }


  // Features

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

  feature tls-listen {
    if-feature listen;
    description
     "The 'tls-listen' feature indicates that the RESTCONF server 
      supports opening a port to listen for incoming RESTCONF
      client connections.  This feature exists as TLS might not
      be a mandatory to implement transport in the future.";
    reference
     "RFC 8040: RESTCONF Protocol";
  }

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

  feature tls-call-home {
    if-feature call-home;
    description
     "The 'tls-call-home' feature indicates that the RESTCONF
      server supports initiating connections to RESTCONF clients.
      This feature exists as TLS might not be a mandatory to
      implement transport in the future.";
    reference
     "RFC 8071: NETCONF Call Home and RESTCONF Call Home";
  }

  container restconf-server {
    uses restconf-server;
    description
      "Top-level container for RESTCONF server configuration.";
  }

  grouping restconf-server {
    description
      "Top-level grouping for RESTCONF server configuration.";

    container listen {
      if-feature listen;
      presence "Enables server to listen for TCP connections";
      description "Configures listen behavior";
      list endpoint {
        key name;
        min-elements 1;
        description
          "List of endpoints to listen for RESTCONF connections.";
        leaf name {
          type string;
          description
            "An arbitrary name for the RESTCONF listen endpoint.";
        }
        choice transport {
          mandatory true;
          description
            "Selects between available transports. This is a
             'choice' statement so as to support additional
             transport options to be augmented in.";
          case tls {
            if-feature tls-listen;
            container tls {
              description
                "TLS-specific listening configuration for inbound
                 connections.";
              leaf address {
                type inet:ip-address;
              description
                "The IP address to listen on for incoming
                 connections.  The RESTCONF server will listen
                 on all configured interfaces if no value is
                 specified.  INADDR_ANY (0.0.0.0) or INADDR6_ANY
                 (0:0:0:0:0:0:0:0 a.k.a. ::) MUST be used when
                 the server is to listen on all IPv4 or IPv6
                 addresses, respectively.";
              }
              leaf port {
                type inet:port-number;
                default 443;
                description
                 "The local port number to listen on.  If no value
                  is specified, the IANA-assigned port value for
                  'https' (443) is used.";
              }
              uses ts:tls-server-grouping {
                refine "client-auth" {
                  must 'pinned-ca-certs or pinned-client-certs';
                  description
                    "RESTCONF servers MUST be able to validate
                     clients.";
                }
                augment "client-auth" {
                  description
                    "Augments in the cert-to-name structure,
                     so the RESTCONF server can map TLS-layer
                     client certificates to RESTCONF usernames.";
                  container cert-maps {
                    uses x509c2n:cert-to-name;
                    description
                     "The cert-maps container is used by a TLS-
                      based RESTCONF server to map the RESTCONF
                      client's presented X.509 certificate to
                      a RESTCONF username.  If no matching and
                      valid cert-to-name list entry can be found,
                      then the RESTCONF server MUST close the
                      connection, and MUST NOT accept RESTCONF
                      messages over it.";
                    reference
                      "RFC 7407: A YANG Data Model for SNMP
                                 Configuration.";
                  }
                }
              }
            } // end tls container
          } // end tls case
        } // end transport
      } // end endpoint
    } // end listen

    container call-home {
      if-feature call-home;
      presence "Enables server to initiate TCP connections";
      description "Configures call-home behavior";
      list restconf-client {
        key name;
        min-elements 1;
        description
          "List of RESTCONF clients the RESTCONF server is to 
           initiate call-home connections to in parallel.";
        leaf name {
          type string;
          description
            "An arbitrary name for the remote RESTCONF client.";
        }
        container endpoints {
          description
            "Container for the list of endpoints.";
          list endpoint {
            key name;
            min-elements 1;
            ordered-by user;
            description
              "User-ordered list of endpoints for this RESTCONF
               client.  Defining more than one enables high-
               availability.";
            leaf name {
              type string;
              description
                "An arbitrary name for this endpoint.";
            }
            choice transport {
              mandatory true;
              description
                "Selects between available transports. This is a
                 'choice' statement so as to support additional
                 transport options to be augmented in.";
              case tls {
                if-feature tls-call-home;
                container tls {
                  description
                    "Specifies TLS-specific call-home transport
                     configuration.";
                  leaf address {
                    type inet:host;
                    mandatory true;
                    description
                     "The IP address or hostname of the endpoint.  
                      If a domain name is configured, then the
                      DNS resolution should happen on each usage
                      attempt.  If the DNS resolution results in
                      multiple IP addresses, the IP addresses will
                      be tried according to local preference order
                      until a connection has been established or
                      until all IP addresses have failed.";
                  }
                  leaf port {
                    type inet:port-number;
                    default 4336;
                    description
                     "The IP port for this endpoint.  The RESTCONF
                      server will use the IANA-assigned well-known
                      port for 'restconf-ch-tls' (4336) if no value
                      is specified.";
                  }
                  uses ts:tls-server-grouping {
                    refine "client-auth" {
                     must 'pinned-ca-certs or pinned-client-certs';
                     description
                      "RESTCONF servers MUST be able to validate
                       clients.";
                    }
                    augment "client-auth" {
                      description
                       "Augments in the cert-to-name structure,
                        so the RESTCONF server can map TLS-layer
                        client certificates to RESTCONF usernames.";
                      container cert-maps {
                        uses x509c2n:cert-to-name;
                        description
                         "The cert-maps container is used by a
                          TLS-based RESTCONF server to map the
                          RESTCONF client's presented X.509
                          certificate to a RESTCONF username. If
                          no matching and valid cert-to-name list
                          entry can be found, then the RESTCONF
                          server MUST close the connection, and
                          MUST NOT accept RESTCONF messages over
                          it.";
                        reference
                          "RFC 7407: A YANG Data Model for SNMP
                           Configuration.";
                      }
                    }
                  }
                }
              }
            } // end transport
          } // end endpoint
        } // end endpoints
        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 available connection types.";
            case persistent-connection {
              container persistent {
                presence
                 "Indicates that a persistent connection is to be
                  maintained.";
                description
                 "Maintain a persistent connection to the RESTCONF 
                  client. If the connection goes down, immediately 
                  start trying to reconnect to it, using the 
                  reconnection strategy.
    
                  This connection type minimizes any RESTCONF
                  client to RESTCONF server data-transfer delay,
                  albeit at the expense of holding resources
                  longer.";
                leaf idle-timeout {
                  type uint32;
                  units "seconds";
                  default 86400;  // one day;
                  description
                    "Specifies the maximum number of seconds that
                     the underlying TLS session may remain idle.
                     A TLS session will be dropped if it is idle
                     for an interval longer than this number of
                     seconds.  If set to zero, then the server
                     will never drop a session because it is idle.
                     Sessions that have a notification subscription
                     active are never dropped.";
                }
                container keep-alives {
                  description
                    "Configures the keep-alive policy, to
                     proactively test the aliveness of the TLS
                     client.  An unresponsive TLS client will
                     be dropped after approximately (max-attempts
                     * max-wait) seconds.";
                  reference
                    "RFC 8071: NETCONF Call Home and RESTCONF
                               Call Home, Section 3.1, item S6";
                  leaf max-wait {
                    type uint16 {
                      range "1..max";
                    }
                    units seconds;
                    default 30;
                    description
                     "Sets the amount of time in seconds after
                      which if no data has been received from
                      the TLS client, a TLS-level message will
                      be sent to test the aliveness of the TLS
                      client.";
                  }
                  leaf max-attempts {
                    type uint8;
                    default 3;
                    description
                     "Sets the maximum number of sequential keep-
                      alive messages that can fail to obtain a
                      response from the TLS client before assuming
                      the TLS client is no longer alive.";  
                  }
                }
              }
            }
            case periodic-connection {
              container periodic {
                presence
                 "Indicates that a periodic connection is to be
                  maintained.";
                description
                 "Periodically connect to the RESTCONF client, so
                  that the RESTCONF client may send requests pending
                  for the RESTCONF server.  Once the connection has
                  been closed, for whatever reason, the server will
                  restart its timer until the next connection.";
                leaf idle-timeout {
                  type uint16;
                  units "seconds";
                  default 300; // five minutes
                  description
                    "Specifies the maximum number of seconds that
                     the underlying TLS session may remain idle.
                     A TLS session will be dropped if it is idle
                     for an interval longer than this number of
                     seconds.  If set to zero, then the server
                     will never drop a session because it is idle.
                     Sessions that have a notification subscription
                     active are never dropped.";
                }
                leaf reconnect-timeout {
                  type uint16 {
                    range "1..max";
                  }
                  units minutes;
                  default 60;
                  description
                   "The maximum amount of unconnected time
                    the RESTCONF server will wait before 
                    re-establishing a connection to the
                    RESTCONF client.  The RESTCONF server
                    may initiate a connection to the RESTCONF
                    client before this time if desired 
                    (e.g., to deliver a notification).";
                }
              }
            }
          }
        }
        container reconnect-strategy {
          description
           "The reconnection strategy directs how a RESTCONF
            server reconnects to a RESTCONF client after after
            discovering its connection to the client has dropped,
            even if due to a reboot.  The RESTCONF server starts
            with the specified endpoint and tries to connect to
            it max-attempts times before trying the next endpoint
            in the list (round robin).";
          leaf start-with {
            type enumeration {
              enum first-listed {
                description
                  "Indicates that reconnections should start with
                   the first endpoint listed.";
              }
              enum last-connected { 
                description
                  "Indicates that reconnections should start with
                   the endpoint last connected to.  If no previous
                   connection has ever been established, then the
                   first endpoint configured is used.   RESTCONF 
                   servers SHOULD be able to remember the last 
                   endpoint connected to 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.";
          }
          leaf max-attempts {
            type uint8 {
              range "1..max";
            }
            default 3;
            description
             "Specifies the number times the RESTCONF server tries
              to connect to a specific endpoint before moving on to
              the next endpoint in the list (round robin).";
          }
        }
      }
    }
  }
}
<CODE ENDS>

4. Security Considerations

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

The YANG module defined in this document is designed to be accessed via YANG based management protocols, such as NETCONF [RFC6241] and RESTCONF [RFC8040]. Both of these protocols have mandatory-to-implement secure transport layers (e.g., SSH, TLS) with mutual authentication.

The NETCONF access control model (NACM) [RFC6536] provides the means to restrict access for particular users to a pre-configured subset of all available protocol operations and content.

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

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

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

NONE

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

NONE

5. IANA Considerations

5.1. The IETF XML Registry

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

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

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

5.2. The YANG Module Names Registry

This document registers two YANG modules in the YANG Module Names registry [RFC7950]. Following the format in [RFC7950], the the following registrations are requested:

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

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

6. References

6.1. Normative References

[I-D.ietf-netconf-keystore] Watsen, K., "YANG Data Model for a Centralized Keystore Mechanism", Internet-Draft draft-ietf-netconf-keystore-05, June 2018.
[I-D.ietf-netconf-tls-client-server] Watsen, K. and G. Wu, "YANG Groupings for TLS Clients and TLS Servers", Internet-Draft draft-ietf-netconf-tls-client-server-05, October 2017.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997.
[RFC6991] Schoenwaelder, J., "Common YANG Data Types", RFC 6991, DOI 10.17487/RFC6991, July 2013.
[RFC7407] Bjorklund, M. and J. Schoenwaelder, "A YANG Data Model for SNMP Configuration", RFC 7407, DOI 10.17487/RFC7407, December 2014.
[RFC7950] Bjorklund, M., "The YANG 1.1 Data Modeling Language", RFC 7950, DOI 10.17487/RFC7950, August 2016.
[RFC8040] Bierman, A., Bjorklund, M. and K. Watsen, "RESTCONF Protocol", RFC 8040, DOI 10.17487/RFC8040, January 2017.
[RFC8071] Watsen, K., "NETCONF Call Home and RESTCONF Call Home", RFC 8071, DOI 10.17487/RFC8071, February 2017.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, May 2017.

6.2. Informative References

[I-D.ietf-netconf-netconf-client-server] Watsen, K. and G. Wu, "NETCONF Client and Server Models", Internet-Draft draft-ietf-netconf-netconf-client-server-05, October 2017.
[RFC3688] Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688, DOI 10.17487/RFC3688, January 2004.
[RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer Security (TLS) Protocol Version 1.2", RFC 5246, DOI 10.17487/RFC5246, August 2008.
[RFC6241] Enns, R., Bjorklund, M., Schoenwaelder, J. and A. Bierman, "Network Configuration Protocol (NETCONF)", RFC 6241, DOI 10.17487/RFC6241, June 2011.
[RFC6536] Bierman, A. and M. Bjorklund, "Network Configuration Protocol (NETCONF) Access Control Model", RFC 6536, DOI 10.17487/RFC6536, March 2012.
[RFC8340] Bjorklund, M. and L. Berger, "YANG Tree Diagrams", BCP 215, RFC 8340, DOI 10.17487/RFC8340, March 2018.

Appendix A. Change Log

A.1. 00 to 01

A.2. 01 to 02

A.3. 02 to 03

A.4. 03 to 04

A.5. 04 to 05

A.6. 05 to 06

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, Balázs Kovács, David Lamparter, Alan Luchuk, Ladislav Lhotka, Radek Krejci, Tom Petch, Juergen Schoenwaelder, Phil Shafer, Sean Turner, and Bert Wijnen.

Authors' Addresses

Kent Watsen Juniper Networks EMail: kwatsen@juniper.net
Gary Wu Cisco Networks EMail: garywu@cisco.com