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<rfc category="std" docName="draft-tsou-pcp-natcoord-10" ipr="trust200902">
  <!-- category values: std, bcp, info, exp, and historic
     ipr values: trust200902, noModificationTrust200902, noDerivativesTrust200902,
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  <!-- ***** FRONT MATTER ***** -->

  <front>
    <!-- The abbreviated title is used in the page header - it is only necessary if the full title is longer than 39 characters -->

    <title abbrev="PCP PORT_SET">Port Control Protocol (PCP) Extension for
      Port Set Allocation</title>

    <author fullname="Qiong Sun" initials="Q." surname="Sun">
      <organization>China Telecom</organization>

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

          <city></city>

          <region></region>

          <code></code>

          <country>P.R.China</country>
        </postal>

        <phone>86 10 58552936</phone>

        <email>sunqiong@ctbri.com.cn</email>
      </address>
    </author>

    <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 initials="S." surname="Sivakumar" fullname="Senthil Sivakumar">
      <organization>Cisco Systems</organization>
      <address>
        <postal>
          <street>7100-8 Kit Creek Road</street>
          <city>Research Triangle Park</city>
          <region>North Carolina</region>
          <code>27709</code>
          <country>USA</country>
        </postal>
        <phone>+1 919 392 5158</phone>
        <email>ssenthil@cisco.com</email>
      </address>
    </author>

    <author fullname="Cathy Zhou" initials="C." surname="Zhou">
      <organization>Huawei Technologies</organization>

      <address>
        <postal>
          <street>Bantian, Longgang District</street>

          <city>Shenzhen</city>

          <code>518129</code>

          <country>P.R. China</country>
        </postal>

        <phone></phone>

        <email>cathy.zhou@huawei.com</email>
      </address>
    </author>

    <author fullname="Tina Tsou" initials="T." surname="Tsou">
      <organization>Huawei Technologies (USA)</organization>

      <address>
        <postal>
          <street>2330 Central Expressway</street>

          <city>Santa Clara, CA 95050</city>

          <code></code>

          <country>USA</country>
        </postal>

        <phone>+1 408 330 4424</phone>

        <email>Tina.Tsou.Zouting@huawei.com</email>
      </address>
    </author>

	<author fullname="Simon Perreault" initials="S." surname="Perreault">
      <organization>Viagenie</organization>
      <address>
      <postal>
      <street>246 Aberdeen</street>
		  <city>Quebec</city>
		  <region>QC</region>
      <code>G1R 2E1</code>
      <country>Canada</country>
      </postal>
	  <phone>+1 418 656 9254</phone>
      <email>simon.perreault@viagenie.ca</email>
      </address>
    </author>
	
    <date/>

    <!-- Meta-data Declarations -->

    <area>Transport</area>

    <workgroup>Internet Engineering Task Force</workgroup>

    <!-- WG name at the upperleft corner of the doc,
         IETF is fine for individual submissions.  
	 If this is not present, the default is "Network Working Group",
         which is used by the RFC Editor as a nod to the history of the IETF. -->

    <abstract>
      <t>This document defines an extension to PCP allowing clients to
        manipulate sets of ports as a whole. This is accomplished by a new
        MAP option: PORT_SET.</t>
    </abstract>
  </front>

  <middle>
    <section title="Introduction">

      <t>This section describes a few (and non-exhaustive) envisioned use cases.
        Note that the PCP extension defined in this document is generic and is
        expected to be applicable to other use cases.</t>

      <section title="Lightweight 4over6">

        <t>In the Lightweight 4over6 <xref
            target="I-D.cui-softwire-b4-translated-ds-lite"/> architecture,
          shared global addresses can be allocated to customers. It allows
          moving the Network Address Translation (NAT) function, otherwise
          accomplished by a Carrier-Grade NAT (CGN) <xref
            target="I-D.ietf-behave-lsn-requirements"/>, to the
          Customer-Premises Equipment (CPE). This provides more control over the
          NAT function to the user, and more scalability to the ISP.</t>

        <t>In the lw4o6 architecture, the PCP-controlled device corresponds to
          the lwAFTR, and the PCP client corresponds to the lwB4. The client
          sends a PCP MAP request containing a PORT_SET option to trigger shared
          address allocation on the lwAFTR. The PCP response contains the shared
          address information, including the port set allocated to the lwB4.</t>

      </section>

      <section title="Applications Using Port Sets">

        <t>Some applications require not just one port, but a port set. One
          example is a Session Initiation Protocol (SIP) User Agent Server (UAS)
          <xref target="RFC3261"/> expecting to handle multiple concurrent
          calls, including media termination. When it receives a call, it needs
          to signal media port numbers to its peer. Generating individual PCP
          MAP requests for each of the media ports during call setup would
          introduce unwanted latency. Instead, the server can pre-allocate a set
          of ports such that no PCP exchange is needed during call setup.</t>

        <t>Using PORT_SET, an application can manipulate port sets much more
          efficiently than with individual MAP requests.</t>

      </section>

      <section title="Firewall Control">

        <t>Port sets are often used in firewall rules. For example, defining a
          range for RTP <xref target="RFC3550"/> traffic is common practice. The
          MAP request can already be used for firewall control. The PORT_SET
          option brings the additional ability to manipulate firewall rules
          operating on port sets instead of single ports.</t>

      </section>

    </section>

    <section title="Terminology">

      <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"/>.</t>

    </section>

    <section title="The need for PORT_SET">

      <t>Multiple MAP requests can be used to manipulate a set of ports, having
        roughly the same effect as a single use of a MAP request with a PORT_SET
        option.  However, use of the PORT_SET option is more efficient when
        considering the following aspects:
        <list style="hanging">
          <t hangText="Network Traffic:">A single request uses less network
            resources than multiple requests.</t>
          <t hangText="Latency:">Even though MAP requests can be sent in
            parallel, we can expect the total processing time to be longer for
            multiple requests than a single one.</t>
          <t hangText="Client-side simplicity:">The logic that is necessary for
            maintaining a set of ports using a single port set entity is much
            simpler than that required for maintaining individual ports,
            especially when considering failures, retransmissions, lifetime
            expiration, and re-allocations.</t>
          <t hangText="Server-side efficiency:">Some PCP-controlled devices can
            allocate port sets in a manner such that data passing through the
            device is processed much more efficiently than the equivalent using
            individual port allocations. For example, a CGN having a "bulk" port
            allocation scheme (see <xref
              target="I-D.ietf-behave-lsn-requirements"/> section 5) often has
            this property.</t>
          <t hangText="Server-side scalability:">The number of mapping entries
            in PCP-controlled devices is often a limiting factor. Allocating
            port sets in a single request can result in a single mapping entry
            being used, therefore allowing greater scalability.</t>
        </list>
      </t>

      <t>Therefore, while it is functionally possible to obtain the same results
        using plain MAP, the extension proposed in this document allows greater
        efficiency, scalability, and simplicity, while lowering latency and
        necessary network traffic. In a nutshell, PORT_SET is a necessary
        optimization.</t>

      <t>In addition, PORT_SET supports parity preservation. Some protocols
        (e.g. RTP <xref target="RFC3550"/>) assign meaning to a port number's
        parity. When mapping sets of ports for the purpose of using such kind of
        protocol, preserving parity can be necessary.</t>

    </section>

    <section title="The PORT_SET Option" anchor="PORT_SET">

      <t>
        <list style="hanging">
          <t hangText="Option Name:">PORT_SET</t>
          <t hangText="Number:">TBD</t>
          <t hangText="Purpose:">To map sets of ports.</t>
          <t hangText="Valid for Opcodes:">MAP</t>
          <t hangText="Length:">2 bytes</t>
          <t hangText="May appear in:">Both requests and responses</t>
          <t hangText="Maximum occurrences:">1</t>
        </list>
      </t>

      <t>
        <list>
          <t>NOTE TO IANA (to be removed prior to publication as an RFC): The
            number is to be assigned by IANA in the range 1-63 (i.e., mandatory
            to process and created via Standards Action).</t>
        </list>
      </t>

      <t>The PORT_SET Option indicates that the client wishes to reserve a set
        of ports. The requested number of ports in that set is indicated in the
        option.</t>

      <t>The PORT_SET Option is formatted as shown in <xref
          target="format"/>.</t>

      <figure anchor="format" title="PORT_SET Option">
        <artwork>
 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Option Code=? |  Reserved   |P|    Option Length=2            |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|        Port Set Size          |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
        </artwork>
      </figure>

      <t>The fields are as follows:
        <list style="hanging">
          <t hangText="P:">1 if parity preservation is requested, 0
            otherwise.</t>
          <t hangText="Port Set Size:">Number of ports requested. MUST NOT be
            zero nor one.</t>
        </list>
      </t>

      <t>
        <list>
          <t>NOTE: In its current form, PORT_SET does not support allocating
            discontinuous port sets. That feature could be added in the future
            depending on input from the working group.</t>
        </list>
      </t>

      <t>The Internal Port Set is defined as being the range of Port Set Size
        ports starting from the Internal Port. The External Port Set is
        respectively defined as being the range of Port Set Size ports starting
        from the Assigned External Port. The two ranges always have the same
        size (i.e., the Port Set Size returned by the server).</t>

      <section title="Client Behavior">

        <t>To retrieve a set of ports, the PCP client adds a PORT_SET option to
          its PCP MAP request. If port preservation is required, the PCP  Client
          MUST set the parity bit (to 1) to ask the server to preserve the port
          parity (i.e., the Assigned External Port and Internal Port have the
          same parity). The PCP client MUST indicate a suggested Port Set Size.
          A non-null value MUST be used.</t>
        
        <t>The PCP Client MUST NOT include more than one PORT_SET option in a
          MAP request. If several port sets are needed, the PCP client MUST
          issue as many MAP requests each of them include a PORT_SET option.
          These individual MAP request MUST include distinct Internal Port.</t>
        
        <t>If the PORT_SET option is not supported by the server, the PCP client
          will have to issue individual MAP requests with no PORT_SET option.</t>

      </section>

      <section title="Server Behavior">

        <t>In addition to regular MAP request processing, the following checks
          are made upon receipt of a PORT_SET option with non-zero Requested
          Lifetime:

          <list style="symbols">

            <t>If multiple PORT_SET options are present in a single MAP request,
              a MALFORMED_OPTION error is returned.</t>

            <t>If the Port Set Size is zero or one, a MALFORMED_OPTION error is
              returned.</t>

          </list>

        </t>

        <t>If the PREFER_FAILURE option is present and the server is unable to
          map all ports in the requested External Port Set or is unable to
          preserve parity (P = 1), the CANNOT_PROVIDE_EXTERNAL error is
          returned.</t>

        <t>If the PREFER_FAILURE option is absent, the server MAY map fewer
          ports than the value of Port Set Size from the request. It MUST NOT
          map more ports than the client asked for. In any case, the Internal
          Port Set MUST always begin from the Internal Port indicated by the
          client. In particular, if the port mapping failed either because of
          the unavailability of ports, the PCP Server SHOULD reserve only one
          external port (i.e., the PCP server ignores the PORT_SET option). If
          the server ends up mapping only a single port, for any reason, the
          PORT_SET option MUST NOT be present in the response.</t>

        <t>If the PREFER_FAILURE option is absent and port parity preservation
          is requested (P = 1), the server MAY preserve port parity. In that
          case, the External Port is set to a value having the same parity as
          the Internal Port.</t>

        <t>If a mapping already exists and the PORT_SET option can be honored,
          the PCP server updates the mapping with port set information and sends
          back a positive answer to the requesting PCP client.</t>

        <t>If the mapping is successful, the MAP response's Assigned External
          Port is set to the first port in the External Port Set, and the
          PORT_SET option's Port Set Size is set to number of ports in the
          mapped port set.</t>

      </section>

      <section title="Port Set Renewal and Deletion">

        <t>Port set mappings are renewed and deleted as a single entity. That
          is, the lifetime of all port mappings in the set is set to the
          Assigned Lifetime at once.</t>

        <t>The PORT_SET option MUST be present in a renewal or deletion request.
          If a server receives a MAP request without a PORT_SET option and whose
          Internal Port is inside a mapped Internal Port Set, it replies with a
          MALFORMED_REQUEST error.</t>

      </section>

    </section>

    <section title="Operational Considerations">

      <t>It is totally up to the PCP server to determine the port-set quota
        for each PCP client. In addition, when the PCP-controlled device
        supports multiple port-sets delegation for a given PCP client, the PCP
        client MAY re-initiate a PCP request to get another port set when it has
        exhausted all the ports within the port-set.</t>

      <t>If the PCP server is configured to allocate multiple port-set
        allocation for one subscriber, the same Assigned External IP Address
        SHOULD be assigned to one subscriber in multiple port-set requests.</t>

      <t>To optimize the number of mapping entries maintained by the PCP
        server, it is RECOMMENDED to configure the server to assign the
        maximum allowed port set in a single response. This policy SHOULD be
        configurable.</t>

      <t>The failover mechanism in MAP [section 14 in <xref
          target="I-D.ietf-pcp-base"></xref>] and <xref
          target="I-D.boucadair-pcp-failure"></xref> can also be applied to
        port sets.</t>

    </section>

    <section title="Security Considerations">
      <t>It is believed that no additional security considerations beyond those
        discussed in <xref target="I-D.ietf-pcp-base"></xref> apply to this
        extension.</t>
    </section>

    <section title="IANA Considerations">

      <t>IANA shall allocate a code in the range 1-63 for the new PCP option
        defined in <xref target="PORT_SET"/>.</t>

    </section>

    <section title="Authors List">
      <t>The following are extended authors who contributed to the effort:</t>

      <t>Yunqing Chen</t>

      <t>China Telecom</t>

      <t>Room 502, No.118, Xizhimennei Street</t>

      <t>Beijing 100035</t>

      <t>P.R.China</t>

      <t></t>

      <t>Chongfeng Xie</t>

      <t>China Telecom</t>

      <t>Room 502, No.118, Xizhimennei Street</t>

      <t>Beijing 100035</t>

      <t>P.R.China</t>

      <t></t>

      <t>Yong Cui</t>

      <t>Tsinghua University</t>

      <t>Beijing 100084</t>

      <t>P.R.China</t>

      <t>Phone: +86-10-62603059</t>

      <t>Email: yong@csnet1.cs.tsinghua.edu.cn</t>

      <t></t>

      <t>Qi Sun</t>

      <t>Tsinghua University</t>

      <t>Beijing 100084</t>

      <t>P.R.China</t>

      <t>Phone: +86-10-62785822</t>

      <t>Email: sunqibupt@gmail.com</t>

      <t></t>

      <t>Gabor Bajko</t>

      <t>Nokia</t>

      <t>Email: gabor.bajko@nokia.com</t>

      <t></t>

      <t>Xiaohong Deng</t>
      <t>France Telecom</t>
      <t>Email: xiaohong.deng@orange-ftgroup.com</t>
    </section>
	
   <section title="Acknowledgements">
     <t>The authors would like to show sincere appreciation to
       Alain Durand,
       Dan Wing,
       Dave Thaler,
       Reinaldo Penno,
       Sam Hartman, 
       and Yoshihiro Ohba,
     for their useful comments and suggestions. 
     </t>
    </section>
  </middle>

  <!--  *****BACK MATTER ***** -->

  <back>
    <references title="Normative References">
      <reference anchor="I-D.ietf-pcp-base">
        <front>
          <title>Port Control Protocol (PCP)</title>

          <author fullname="Dan Wing" initials="D." surname="Wing">
            <organization>Cisco Systems</organization>
          </author>

          <date month="October" year="2012" />
        </front>
      </reference>

      <reference anchor='RFC2119'>
        <front>
          <title abbrev='RFC Key Words'>Key words for use in RFCs to Indicate Requirement Levels</title>
          <author initials='S.' surname='Bradner' fullname='Scott Bradner'>
            <organization>Harvard University</organization>
            <address>
              <postal>
                <street>1350 Mass. Ave.</street>
                <street>Cambridge</street>
                <street>MA 02138</street></postal>
              <phone>- +1 617 495 3864</phone>
              <email>sob@harvard.edu</email></address></author>
          <date year='1997' month='March' />
          <area>General</area>
          <keyword>keyword</keyword>
          <abstract>
            <t>
              In many standards track documents several words are used to signify
              the requirements in the specification.  These words are often
              capitalized.  This document defines these words as they should be
              interpreted in IETF documents.  Authors who follow these guidelines
              should incorporate this phrase near the beginning of their document:

              <list>
                <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
                  RFC 2119.
            </t></list></t>
            <t>
              Note that the force of these words is modified by the requirement
              level of the document in which they are used.
        </t></abstract></front>

        <seriesInfo name='BCP' value='14' />
        <seriesInfo name='RFC' value='2119' />
        <format type='TXT' octets='4723' target='http://www.rfc-editor.org/rfc/rfc2119.txt' />
        <format type='HTML' octets='17491' target='http://xml.resource.org/public/rfc/html/rfc2119.html' />
        <format type='XML' octets='5777' target='http://xml.resource.org/public/rfc/xml/rfc2119.xml' />
      </reference>

    </references>

    <references title="informative References">
      <reference anchor="I-D.cui-softwire-b4-translated-ds-lite">
        <front>
          <title>Lightweight 4over6: An Extension to DS-Lite
          Architecture</title>

          <author fullname=" Yong Cui" initials="Y." surname="Cui">
            <organization>Tsinghua University</organization>
          </author>

          <author fullname="Qiong Sun" initials="Q." surname="Sun">
            <organization>China Telecom</organization>
          </author>

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

          <author fullname=" Tina Tsou" initials="T." surname="Tsou">
            <organization>Huawei Technologies</organization>
          </author>

          <author fullname="Yiu L. Lee" initials="Y." surname="Lee">
            <organization>Comcast</organization>
          </author>

          <date month="Feb" year="2012" />
        </front>
      </reference>

      <reference anchor="I-D.boucadair-pcp-failure">
        <front>
          <title>Port Control Protocol (PCP) Failure Scenarios</title>

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

          <author fullname="Francis Dupont" initials=" F." surname="Dupont">
            <organization>Internet Systems Consortium</organization>
          </author>

          <author fullname="Reinaldo Penno" initials="R." surname="Penno">
            <organization>Cisco</organization>
          </author>

          <date month="August" year="2012" />
        </front>
      </reference>

      <reference anchor='I-D.ietf-behave-lsn-requirements'>
        <front>
          <title>Common requirements for Carrier Grade NATs (CGNs)</title>

          <author initials='S' surname='Perreault' fullname='Simon Perreault'>
            <organization />
          </author>

          <author initials='I' surname='Yamagata' fullname='Ikuhei Yamagata'>
            <organization />
          </author>

          <author initials='S' surname='Miyakawa' fullname='Shin Miyakawa'>
            <organization />
          </author>

          <author initials='A' surname='Nakagawa' fullname='Akira Nakagawa'>
            <organization />
          </author>

          <author initials='H' surname='Ashida' fullname='Hiroyuki Ashida'>
            <organization />
          </author>

          <date month='December' day='6' year='2012' />

          <abstract><t>This document defines common requirements for Carrier-Grade NAT (CGN).  It updates RFC 4787.</t></abstract>

        </front>

        <seriesInfo name='Internet-Draft' value='draft-ietf-behave-lsn-requirements-10' />
        <format type='TXT'
          target='http://www.ietf.org/internet-drafts/draft-ietf-behave-lsn-requirements-10.txt' />
      </reference>

      <reference anchor='RFC3261'>

        <front>
          <title>SIP: Session Initiation Protocol</title>
          <author initials='J.' surname='Rosenberg' fullname='J. Rosenberg'>
            <organization /></author>
          <author initials='H.' surname='Schulzrinne' fullname='H. Schulzrinne'>
            <organization /></author>
          <author initials='G.' surname='Camarillo' fullname='G. Camarillo'>
            <organization /></author>
          <author initials='A.' surname='Johnston' fullname='A. Johnston'>
            <organization /></author>
          <author initials='J.' surname='Peterson' fullname='J. Peterson'>
            <organization /></author>
          <author initials='R.' surname='Sparks' fullname='R. Sparks'>
            <organization /></author>
          <author initials='M.' surname='Handley' fullname='M. Handley'>
            <organization /></author>
          <author initials='E.' surname='Schooler' fullname='E. Schooler'>
            <organization /></author>
          <date year='2002' month='June' />
          <abstract>
            <t>This document describes Session Initiation Protocol (SIP), an application-layer control (signaling) protocol for creating, modifying, and terminating sessions with one or more participants.  These sessions include Internet telephone calls, multimedia distribution, and multimedia conferences. [STANDARDS-TRACK]</t></abstract></front>

        <seriesInfo name='RFC' value='3261' />
        <format type='TXT' octets='647976' target='http://www.rfc-editor.org/rfc/rfc3261.txt' />
      </reference>

      <reference anchor='RFC3550'>

        <front>
          <title>RTP: A Transport Protocol for Real-Time Applications</title>
          <author initials='H.' surname='Schulzrinne' fullname='H. Schulzrinne'>
            <organization /></author>
          <author initials='S.' surname='Casner' fullname='S. Casner'>
            <organization /></author>
          <author initials='R.' surname='Frederick' fullname='R. Frederick'>
            <organization /></author>
          <author initials='V.' surname='Jacobson' fullname='V. Jacobson'>
            <organization /></author>
          <date year='2003' month='July' />
          <abstract>
            <t>This memorandum describes RTP, the real-time transport protocol.  RTP provides end-to-end network transport functions suitable for applications transmitting real-time data, such as audio, video or simulation data, over multicast or unicast network services.  RTP does not address resource reservation and does not guarantee quality-of- service for real-time services.  The data transport is augmented by a control protocol (RTCP) to allow monitoring of the data delivery in a manner scalable to large multicast networks, and to provide minimal control and identification functionality.  RTP and RTCP are designed to be independent of the underlying transport and network layers.  The protocol supports the use of RTP-level translators and mixers.  Most of the text in this memorandum is identical to RFC 1889 which it obsoletes.  There are no changes in the packet formats on the wire, only changes to the rules and algorithms governing how the protocol is used.  The biggest change is an enhancement to the scalable timer algorithm for calculating when to send RTCP packets in order to minimize transmission in excess of the intended rate when many participants join a session simultaneously. [STANDARDS-TRACK]</t></abstract></front>

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