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<rfc category="std" docName="draft-boucadair-pcp-capability-03"
     ipr="trust200902">
  <front>
    <title abbrev="CAPABILITY">Retrieving the Capabilities of a PCP-controlled
    Device</title>

    <author fullname="Mohamed Boucadair" initials="M." surname="Boucadair">
      <organization>France Telecom</organization>

      <address>
        <postal>
          <street></street>

          <city>Rennes</city>

          <region></region>

          <code>35000</code>

          <country>France</country>
        </postal>

        <email>mohamed.boucadair@orange.com</email>
      </address>
    </author>

    <author fullname="Tirumaleswar Reddy" initials="T." surname="Reddy">
      <organization abbrev="Cisco">Cisco Systems, Inc.</organization>

      <address>
        <postal>
          <street>Cessna Business Park, Varthur Hobli</street>

          <street>Sarjapur Marathalli Outer Ring Road</street>

          <city>Bangalore</city>

          <region>Karnataka</region>

          <code>560103</code>

          <country>India</country>
        </postal>

        <email>tireddy@cisco.com</email>
      </address>
    </author>

    <date day="25" month="November" year="2013" />

    <workgroup>PCP Working Group</workgroup>

    <abstract>
      <t>This document extends Port Control Protocol (PCP) with the ability to
      retrieve the capabilities of PCP-controlled device: CAPABILITY
      Option.</t>
    </abstract>

    <note title="Requirements Language">
      <t>The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
      "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
      document are to be interpreted as described in <xref
      target="RFC2119">RFC 2119</xref>.</t>
    </note>
  </front>

  <middle>
    <section anchor="introduction" title="Introduction">
      <t>This document extends the <xref target="RFC6887">base PCP </xref>
      with a new feature to discover the capabilities of a PCP-controlled
      device. Retrieving the capabilities of a PCP-controlled device would
      allow to avoid error, provide a hint why some applications fails, help
      select the OpCode to issue, etc.</t>

      <t>This option can be elected to be defined as a new OpCode.</t>
    </section>

    <section anchor="capability_ie" title="CAPABILITY">
      <t>The CAPABILITY option (Code: TBA, <xref target="capability"></xref>)
      is used by a PCP Server to indicate to a requesting PCP Client the
      capabilities it supports with regards to port forwarding operations.</t>

      <t>One single Capability option is conveyed in the same PCP response
      message even if several functions are co-located in the same
      PCP-controlled device (e.g., NAT44 and NAT64, NAT44 and ports set
      assignment capability, etc.).</t>

      <t>This option, when received from a PCP Server, is used by a PCP Client
      to constraint the content of its requests and therefore avoid
      errors.</t>

      <t><figure anchor="capability" title="Capability option">
          <preamble></preamble>

          <artwork><![CDATA[       
    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | CAPABILITY    |  Reserved     |            Length=16          |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |A|                           Capability                        |
   +-+                                                             |
   :                                                               :
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

      This Option:

      Option Name: PCP Capabilities Option (CAPABILITY)
      Number: TBA (IANA)
      Purpose: Retrieve the capabilities of a PCP-controlled device 
      Valid for Opcodes: ANNOUNCE, MAP, PEER
      Length: 16
      May appear in: both request and response
      Maximum occurrences: None

]]></artwork>

          <postamble></postamble>
        </figure></t>

      <t>A-bit when set (i.e., 1) indicates the PCP Server supports
      authentication. If this bit is set to 0, is indicates plain PCP is
      supported.</t>

      <t>The Capability Field is encoded in 127 bits. Each bit in the
      Capability bit mask is used to represent the PCP-controlled device
      capability. Several bits can be set if several functions are co-located
      in the same device. The following values for the Capability field
      are:</t>

      <t><list style="empty">
          <t>Bit #: Description</t>

          <t>1: NAT44</t>

          <t>2: Stateless NAT64 <xref target="RFC6145"></xref>.</t>

          <t>4: Stateful NAT64 <xref target="RFC6146"></xref>.</t>

          <t>8: A+P Port Range Router <xref target="RFC6346"></xref></t>

          <t>9: Supports PORT_SET option <xref
          target="I-D.ietf-pcp-port-set"></xref>. </t>

          <t>16: IPv4 firewall.</t>

          <t>32: IPv6 Firewall <xref target="RFC6092"></xref>.</t>

          <t>64: NPTv6 <xref target="RFC6296"></xref>.</t>

          <t>125: DSCP re-marking function.</t>

          <t>126: FLOWDATA-aware function (<xref
          target="I-D.wing-pcp-flowdata"></xref>).</t>

          <t>127: ILNP Translator <xref target="RFC6740"></xref>.</t>
        </list></t>
    </section>

    <section title="PCP Client/Server Behavior">
      <t>This section specifies the behavior of the PCP Client and the PCP
      Server to handle the CAPABILITY Option.</t>

      <t>The PCP Server MAY be configured to return the CAPABILITY Option even
      if it is not included in the request.</t>

      <t>Once the PCP Client is configured with its PCP Server(s), it MAY
      issue an ANNOUNCE OpCode which enclose a CAPABILITY Option. Sending the
      ANNOUNCE OpCode and the CAPABILITY Option allows the PCP Client to
      determine whether the PCP Server is alive and also to retrieve its
      capabilities. Based on the received capabilities, the PCP Client may
      decide to tune its requests (e.g., <xref target="usage"></xref>) and
      decide whether all PCP Servers need to be contacted in parallel or only
      a subset of them should be contacted.</t>

      <t>Upon receipt of a PCP request from a PCP Client requiring the PCP
      Server to enforce an operation beyond its capabilities, the PCP Server
      MAY return an error code together with the CAPABILITY option.</t>

      <t>When a new PCP Server joins the network then it MAY send an ANNOUNCE
      OpCode with its capabilities (i.e., CAPABILITY Option).</t>
    </section>

    <section anchor="usage" title="Option Usage">
      <t>Below are provided examples of the CAPABILITY Option usage:<list
          style="symbols">
          <t>In an IPv6 network with NPTv6 <xref target="RFC6296"></xref>,
          Firewalls implementing the PCP Server are on different devices: the
          PCP Client learns of the available PCP Servers by using DHCP <xref
          target="I-D.ietf-pcp-dhcp"></xref> or any other PCP Server discovery
          technique defined in future specifications. PCP Client learns the
          PCP Server capabilities using CAPABILITY Option. The PCP Client
          sends MAP PCP request to PCP-controlled NPTv6 device with Internal
          Port=0 and Protocol=0 (which means 'all ports for all protocols') to
          find the external IP address. This PCP request has to be sent only
          once since NPTv6 is stateless and provides a 1:1 relationship
          between addresses in the "inside" and "outside" prefixes. The PCP
          Client will send PCP re-request to NTPv6 only before the Assigned
          Lifetime of the MAP response expires or when the host embedding the
          PCP Client acquires a new IPv6 address using "inside" prefix.
          However PCP Client will send MAP/PEER requests to Firewall to
          create/delete dynamic outbound mapping or use PCP instead of its
          default application keep-alives to maintain the Firewall state
          alive.<figure anchor="figure1"
              title="NPTv6 and FW not collocated with PCP server Capability">
              <artwork><![CDATA[     PCP           
    Client                              __________
+-----------+   +------+   +------+    /          \   +-----------+
|Application|___| NPTv6|___| FW   |____| Internet |___|Application|    
|  Client   |   |      |   |      |    |          |   |   Server  | 
+-----------+   +------+   +------+    \__________/   +-----------+               
        ]]></artwork>
            </figure></t>

          <t>In a network with NAT64 <xref target="RFC6146"></xref>, Firewall
          implementing PCP servers are on different devices: IPv6-only PCP
          Client can send PREFIX64 PCP Option <xref
          target="I-D.ietf-pcp-nat64-prefix64"></xref> only to the
          PCP-controlled NAT64 device to learn the Prefix64(s) used to build
          IPv4-embedded IPv6 addresses.</t>

          <t>Multiple PCP-controlled devices: See <xref
          target="figure2"></xref> the example of a network deploying several
          techniques to ensure interconnection with IPv4, provide IPv6-only
          connectivity, etc. Of course, one can argue this configuration is no
          realistic. <figure anchor="figure2"
              title="Multiple PCP-controlled devoce">
              <artwork><![CDATA[                                     +-----+ 
                               ______|NPTv6|___________                      
                              /      +-----+           \
                              |                        |
                              |                     +-----+
+-----------+   +------+      |                     | PRR |
|Application|___| IPv6 |______|     SP Network      +-----+
|PCP  Client|   |  FW  |      |                        |
+-----------+   +------+      |                     +------+
                              |                     | NAT64|
+-----------+   +-------+     |                     |   +  |
|PCP Client |___|A+P NAT|_____|                     |  FW  |  
+-----------+   +-------+     |      +-----+        +------+
                              \______|NPTv6|___________/
                                     +-----+    
]]></artwork>
            </figure></t>

          <t>In a IPv6 network with ILNP translator <xref
          target="RFC6740"></xref>, Firewall implementing PCP servers are on
          different devices. PCP client needs to send PCP request only to the
          PCP-controlled ILNP translator to find Global Locators associated
          with Internal Locators.</t>

          <t>When the PCP-controlled device is a PRR, the PCP Client should
          use PORT_SET <xref target="I-D.ietf-pcp-port-set"></xref>
          option.</t>
        </list></t>
    </section>

    <section anchor="security" title="Security Considerations">
      <t>Security considerations discussed in <xref target="RFC6887"></xref>
      must be considered.</t>
    </section>

    <section anchor="iana" title="IANA Considerations">
      <t>The following PCP Option Code is to be allocated in the
      optional-to-process range (the registry is maintained in
      http://www.iana.org/assignments/pcp-parameters/pcp-parameters.xml#options):<list
          style="empty">
          <t>CAPABILITY</t>
        </list>A sub-registry is required to track the set of capabilities of
      PCP-controlled devices. </t>
    </section>
  </middle>

  <back>
    <references title="Normative References">
      <?rfc include="reference.RFC.2119"?>

      <?rfc include='reference.RFC.6887'?>

      <?rfc include='reference.RFC.6145'?>

      <?rfc include='reference.RFC.6146'
?>
    </references>

    <references title="Informative References">
      <?rfc include='reference.I-D.ietf-pcp-port-set'?>

      <?rfc include='reference.I-D.ietf-opsawg-firewalls'?>

      <?rfc include='reference.I-D.ietf-pcp-nat64-prefix64'?>

      <?rfc include='reference.I-D.wing-pcp-flowdata'?>

      <?rfc include='reference.RFC.6346'?>

      <?rfc include='reference.RFC.6092'?>

      <?rfc include='reference.RFC.6296'?>

      <?rfc include='reference.I-D.ietf-pcp-dhcp'
?>

      <?rfc include='reference.RFC.6740'?>
    </references>

    <!--
-->
  </back>
</rfc>
