[Docs] [txt|pdf] [Tracker] [WG] [Email] [Diff1] [Diff2] [Nits]

Versions: (draft-ietf-sipping-multiple-refer) 00 01 02 03 RFC 5368

SIPPING Working Group                                       G. Camarillo
Internet-Draft                                                  Ericsson
Expires: March 22, 2007                                         A. Niemi
                                                              M. Isomaki
                                                        M. Garcia-Martin
                                                                   Nokia
                                                            H. Khartabil
                                                                   Telio
                                                      September 18, 2006


Refering to Multiple Resources in the Session Initiation Protocol (SIP)
                  draft-ietf-sip-multiple-refer-00.txt

Status of this Memo

   By submitting this Internet-Draft, each author represents that any
   applicable patent or other IPR claims of which he or she is aware
   have been or will be disclosed, and any of which he or she becomes
   aware will be disclosed, in accordance with Section 6 of BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF), its areas, and its working groups.  Note that
   other groups may also distribute working documents as Internet-
   Drafts.

   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."

   The list of current Internet-Drafts can be accessed at
   http://www.ietf.org/ietf/1id-abstracts.txt.

   The list of Internet-Draft Shadow Directories can be accessed at
   http://www.ietf.org/shadow.html.

   This Internet-Draft will expire on March 22, 2007.

Copyright Notice

   Copyright (C) The Internet Society (2006).

Abstract

   This document defines extensions to the SIP REFER method so that this
   method can be used to refer servers to multiple resources.  These
   extensions include the use of pointers to Uniform Resource Identifier



Camarillo, et al.        Expires March 22, 2007                 [Page 1]

Internet-Draft               Multiple REFER               September 2006


   (URI)-lists in the Refer-To header field and the "multiple-refer" SIP
   option-tag.


Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
   2.  Terminology  . . . . . . . . . . . . . . . . . . . . . . . . .  3
   3.  Overview of operation  . . . . . . . . . . . . . . . . . . . .  3
   4.  The multiple-refer SIP Option-Tag  . . . . . . . . . . . . . .  4
   5.  Suppressing REFER's Implicit Subscription  . . . . . . . . . .  4
   6.  URI-List Format  . . . . . . . . . . . . . . . . . . . . . . .  5
   7.  Behavior of SIP REFER-Issuers  . . . . . . . . . . . . . . . .  7
   8.  Behavior of REFER-Recipients . . . . . . . . . . . . . . . . .  7
   9.  Example  . . . . . . . . . . . . . . . . . . . . . . . . . . .  8
   10. Security Considerations  . . . . . . . . . . . . . . . . . . . 10
   11. IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 10
   12. References . . . . . . . . . . . . . . . . . . . . . . . . . . 10
     12.1.  Normative References  . . . . . . . . . . . . . . . . . . 10
     12.2.  Informative References  . . . . . . . . . . . . . . . . . 11
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 13
   Intellectual Property and Copyright Statements . . . . . . . . . . 14





























Camarillo, et al.        Expires March 22, 2007                 [Page 2]

Internet-Draft               Multiple REFER               September 2006


1.  Introduction

   The SIP [5] REFER method [7] allows a user agent to request a server
   to send a request to a third party.  Still, a number of applications
   need to request a server to initiate transactions towards a set of
   destinations.  In one example, the moderator of a conference may want
   the conference server to send BYE requests to a group of
   participants.  In another example, the same moderator may want the
   conference server to INVITE a set of new participants.

   We define an extension to REFER so that REFER can be used to refer
   servers to multiple destinations.  In addition, this mechanism uses
   the suppression of the REFER method implicit subscription specified
   in RFC 4488 [8] to suppress REFER's implicit subscription.


2.  Terminology

   In this document, the key words "MUST", "MUST NOT", "REQUIRED",
   "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT
   RECOMMENDED", "MAY", and "OPTIONAL" are to be interpreted as
   described in BCP 14, RFC 2119 [1] and indicate requirement levels for
   compliant implementations.

   We define the following three new terms:

   REFER-Issuer: the user agent issuing the REFER request.

   REFER-Recipient: the user agent receiving the REFER request.

   REFER-Target: the intended final recipient of the request to be
      generated by the REFER-Recipient.


3.  Overview of operation

   This document defines an extension to the SIP REFER method [7] that
   allows a SIP User Agent Client (UAC) to include a URI-list [9] of
   REFER-Targets in a REFER request and send it to a server.  The server
   will create a new request for each entry in the list of REFER-Target
   URIs.

   The URI-list of REFER-Targets is used in conjunction with the
   copyControl attribute extension [11] to allow the sender indicate the
   role (e.g., 'to', 'cc', or anonymous) in which the REFER-Target is
   involved in the signalling.

   We represent the multiple REFER-Targets of a REFER using a URI-list



Camarillo, et al.        Expires March 22, 2007                 [Page 3]

Internet-Draft               Multiple REFER               September 2006


   [9].  A UAC (User Agent Client) that wants to refer a server to a set
   of destinations creates a SIP REFER request.  The Refer-To header
   contains a pointer to a URI-list, which is included in a body part,
   and an option-tag in the Required header field: "multiple-refer".
   This option-tag indicates the requirement to support the
   functionality described in this specification.

   When the server receives such request it creates a new request per
   destination and sends them.

   This document does not provide any mechanism for UACs to find out
   about the results of a REFER with multiple REFER-Targets.
   Furthermore, it does not provide support for the implicit
   subscription mechanism that is part of the SIP REFER method.  The way
   UACs are kept informed about the results of a REFER is service
   specific.  For example, a UAC sending a REFER to INVITE a set of
   participants to a conference may discover which participants were
   successfully brought into the conference by subscribing to the
   conference state event [12].


4.  The multiple-refer SIP Option-Tag

   We define a new SIP option-tag for the Require and Supported header
   fields: "multiple-refer".

   A user agent including the "multiple-refer" option-tag in a Supported
   header field indicates compliance with this specification.

   A user agent generating a REFER with a pointer to a URI-list in its
   Refer-To header field MUST include the "multiple-refer" option-tag in
   the Require header field of the REFER.


5.  Suppressing REFER's Implicit Subscription

   REFER requests with a single REFER-Target establish implicitly a
   subscription to the refer event.  The REFER-Issuer is informed about
   the result of the transaction towards the REFER-Target through this
   implicit subscription.  As described in RFC 3515 [7], NOTIFY requests
   sent as a result of an implicit subscription created by a REFER
   request contain a body of type "message/sipfrag" [6] that describes
   the status of the transaction initiated by the REFER-Recipient.

   In the case of a REFER-Issuer that generates a REFER with multiple
   REFER-targets, the REFER-Issuer is typically already subscribed to
   other event package that can provide the information about the result
   of the transactions towards the REFER-Targets.  For example, a



Camarillo, et al.        Expires March 22, 2007                 [Page 4]

Internet-Draft               Multiple REFER               September 2006


   moderator instructing a conference server to send a BYE request to a
   set of participants is usually subscribed to the conference state
   event package for the conference.  Notifications to this event
   package will keep the moderator and the rest of the subscribers
   informed of the current list of conference participants.

   Most of the applications using multiple REFER do not need its
   implicit subscription.  Consequently, a SIP REFER-Issuer generating a
   REFER request with multiple REFER-Targets SHOULD include the
   "norefersub" option-tag in a Require header field and SHOULD include
   a Refer-Sub header field set to "false" to indicate that no
   notifications about the requests should be sent to the REFER-Issuer.
   The REFER-Recipient SHOULD honor the suggestion and also include a
   Refer-Sub header field set to "false" in the 200 OK response.  The
   "norefersub" SIP option-tag and the Refer-Sub header field are
   specified in RFC 4488 [8].

      RFC 4488 [8] indicates that a condition for the REFER-Issuer to
      include a Refer-Sub header is that the REFER-Issuer is sure that
      the REFER request will not fork.

   At the time of writing, there is no extension that allows to report
   the status of several transactions over a REFER's implicit
   subscription.  That is the motivation for this document to recommend
   the usage of the "norefersub" option-tag.  If in the future such an
   extension is defined, REFER-Issuers using it could refrain from using
   the "norefersub" option-tag and use the new extension instead.


6.  URI-List Format

   As described in the Framework and Security Considerations for SIP
   URI-List Services [10], specifications of individual URI-list
   services, need to specify a default format for 'recipient-list'
   bodies used within the particular service.

   The default format for 'recipient-list' bodies for conferencing UAs
   (User Agents) and servers is the XML resource list format [9]
   extended with the XML Format Extension for Representing Copy Control
   Attributes in Resource Lists [11].  UAs handling 'recipient-list'
   bodies MUST support both of these formats and MAY support other
   formats.

   As described in the XML Format Extension for Representing Copy
   Control Attributes in Resource Lists [11], each URI can be tagged
   with a 'copyControl' attribute set to either "to", "cc", or "bcc",
   indicating the role in which the recipient will get the referred SIP
   request.  However, it must be noted that, depending on the target SIP



Camarillo, et al.        Expires March 22, 2007                 [Page 5]

Internet-Draft               Multiple REFER               September 2006


   method, a 'copyControl' attribute may not have sense.  For example,
   while a 'copyControl' attribute can be applied to INVITE requests, it
   may not make sense with mid-dialog requests such as BYE requests.

   In addition to the 'copyControl' attribute, URIs can be tagged with
   the 'anonymize' attribute, also specified in the XML Format Extension
   for Representing Copy Control Attributes in Resource Lists [11] to
   prevent that the server discloses the target URI in a URI-list.

   Additionally, the XML Format Extension for Representing Copy Control
   Attributes in Resource Lists [11] defines a 'recipient-list-history'
   body that contains the list of recipients.  The default format for
   'recipient-list-history' bodies for conference services is also the
   XML resource list document format [7] extended with the XML Format
   Extension for Representing Copy Control Attributes in Resource Lists
   [8].  Conferencing servers MUST support both of these formats; UASes
   MAY support these formats.  Both conferencing servers and UASes MAY
   support other formats.

   Nevertheless, the XML resource list document [9] provides features,
   such as hierarchical lists and the ability to include entries by
   reference relative to the XCAP root URI, that are not needed by the
   multiplet REFER service defined in this document.  Therefore, when
   using the default resource list document, SIP REFER-Issuers
   generating REFERs with multiple REFER-Targets SHOULD use flat lists
   (i.e., no hierarchical lists) and SHOULD NOT use <entry-ref>
   elements.

   A REFER-Recipient receiving a URI-list with more information than
   what has just been described MAY discard all the extra information.

   Figure 1 shows an example of a flat list that follows the resource
   list document.


   <?xml version="1.0" encoding="UTF-8"?>
   <resource-lists xmlns="urn:ietf:params:xml:ns:resource-lists"
              xmlns:cp="urn:ietf:params:xml:ns:copycontrol">

     <list>
       <entry uri="sip:bill@example.com" cp:copyControl="to"  />
       <entry uri="sip:joe@example.org" cp:copyControl="cc" />
       <entry uri="sip:ted@example.net" cp:copyControl="bcc" />
     </list>
   </resource-lists>

   Figure 1: URI List




Camarillo, et al.        Expires March 22, 2007                 [Page 6]

Internet-Draft               Multiple REFER               September 2006


7.  Behavior of SIP REFER-Issuers

   As indicated in Section 4 and Section 5 a SIP REFER-Issuer that
   creates a REFER request with multiple REFER-Targets includes a
   "multiple-refer" and "norefersub" option-tags in the Require header
   field and, if appropriate, a Refer-Sub header field set to "false".
   The REFER-Issuer includes the set of REFER-Targets in body whose
   disposition type is 'recipient-list', as defined in the Framework and
   Security Considerations for SIP URI-List Services [10].  The URI-list
   body is further described in Section 6.

   The Refer-To header field of a REFER request with multiple REFER-
   Targets MUST contain a pointer (i.e., a Content-ID Uniform Resource
   Locator (URL) [3] ) that points to the body part that carries the
   URI-list.  The REFER-Issuer SHOULD NOT include any particular URI
   more than once in the URI-list.


8.  Behavior of REFER-Recipients

   The REFER-Recipient follows the rules in Section 2.4.2 of RFC 3515
   [7] to determine the status code of the response to the REFER.

   The REFER-Recipient SHOULD not create an implicit subscription, and
   SHOULD add a Refer-Sub header field set to "false" in the 200 OK
   response.

   If the URI-list of the REFER request contains a repeated URI, the
   REFER-Recipient MUST behave as if that URI appeared in the URI-list
   only once.  The REFER-Recipient uses the comparison rules specific to
   the URI scheme of each of the URIs in the URI-list to determine if
   there is any URI which appears more than once.

   The incoming REFER request typically contains a URI-list document or
   reference with the actual list of recipients.  If this URI-list
   includes resources tagged with the 'copyControl' attribute set to a
   value of "to" or "cc", and if appropriate for the service, e.g., if
   it is non-mid dialog request, the URI-list server SHOULD include a
   URI-list in each of the outgoing requests.  This list SHOULD be
   formatted according to the XML format for representing resource lists
   [9] and the copyControl extension [11].  The URI-list server MUST
   follow the procedures specified in XML format for representing
   resource lists [9] with respect handling of the 'anonymize', 'count'
   and 'copyControl' attributes.

   If the server includes a URI-list in an outgoing request, it MUST
   include a Content-Disposition header field [2] with the value set to
   'recipient-list-history' and a 'handling' parameter [4] set to



Camarillo, et al.        Expires March 22, 2007                 [Page 7]

Internet-Draft               Multiple REFER               September 2006


   "optional".

   The REFER-Recipient follows the rules in RFC 3515 [7] to generate the
   necessary requests towards the REFER-Targets, acting as if it had
   received a regular (no URI-list) REFER per each URI in the URI-list.


9.  Example

   Figure 2 shows an example flow where a REFER-Issuer sends a multiple-
   REFER request to the focus of a conference, which acts as the REFER-
   Recipient.  The REFER-Recipient generates a BYE request per REFER-
   Target.  (How to use REFER to remove participants from a conference
   is specified in [13].)

   +--------+         +---------+    +--------+  +--------+  +--------+
   | REFER  |         |  REFER  |    | REFER  |  | REFER  |  | REFER  |
   | issuer |         |recipient|    |target 1|  |target 2|  |target 3|
   +--------+         +---------+    +--------+  +--------+  +--------+
        | 1. REFER         |             |           |           |
        | ---------------->|             |           |           |
        | 2. 202 Accepted  |             |           |           |
        |<---------------- |   3. BYE    |           |           |
        |                  | ----------->|           |           |
        |                  |   4. BYE    |           |           |
        |                  | ----------------------->|           |
        |                  |   5. BYE    |           |           |
        |                  | ----------------------------------->|
        |                  |   6. 200 OK |           |           |
        |                  |<----------- |           |           |
        |                  |   7. 200 OK |           |           |
        |                  |<----------------------- |           |
        |                  |   8. 200K OK|           |           |
        |                  |<----------------------------------- |
        |                  |             |           |           |
        |                  |             |           |           |
        |                  |             |           |           |

   Figure 2: Example flow or a REFER request containin multiple REFER-
   Targets

   The REFER request (1) contains a Refer-To header field that includes
   a pointer to the message body, which carries a list with the URIs of
   the REFER-Targets.  In this example, the URI-list does not contain
   the copyControl attribute extension.  The REFER's Require header
   field carries the "multiple-refer" and "norefersub" option-tags.  The
   Request-URI is set to a Globally Routable User Agent URIs (GRUU) [14]
   (as a guarantee that the REFER request will not fork).  The Refer-Sub



Camarillo, et al.        Expires March 22, 2007                 [Page 8]

Internet-Draft               Multiple REFER               September 2006


   header field is set to "false" to request the suppression of the
   implicit subscription.  Figure 3 shows an example of this REFER
   request.  The resource list document contains the list of REFER-
   Target URIs along with the method of the SIP request that the REFER-
   Recipient generates.

   REFER sip:conf-123@example.com;gruu;opaque=hha9s8d-999a  SIP/2.0
   Via: SIP/2.0/TCP client.chicago.example.com
           ;branch=z9hG4bKhjhs8ass83
   Max-Forwards: 70
   To: "Conference 123" <sip:conf-123@example.com>
   From: Carol <sip:carol@chicago.example.com>;tag=32331
   Call-ID: d432fa84b4c76e66710
   CSeq: 2 REFER
   Contact: <sip:carol@client.chicago.example.com>
   Refer-To: <cid:cn35t8jf02@example.com>
   Refer-Sub: false
   Require: multiple-refer, norefersub
   Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, SUBSCRIBE, NOTIFY
   Allow-Events: dialog
   Accept: application/sdp, message/sipfrag
   Content-Type: application/resource-lists+xml
   Content-Disposition: recipient-list
   Content-Length: 362
   Content-ID: <cn35t8jf02@example.com>

   <?xml version="1.0" encoding="UTF-8"?>
   <resource-lists xmlns="urn:ietf:params:xml:ns:resource-lists"
           xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
     <list>
       <entry uri="sip:bill@example.com?method=BYE" />
       <entry uri="sip:joe@example.org?method=BYE" />
       <entry uri="sip:ted@example.net?method=BYE" />
     </list>
   </resource-lists>

   Figure 3: REFER request with multiple REFER-Targets

   Figure 4 shows an example of the BYE request (3) that the REFER-
   Recipient sends to the first REFER-Target.











Camarillo, et al.        Expires March 22, 2007                 [Page 9]

Internet-Draft               Multiple REFER               September 2006


   BYE sip:bill@example.com SIP/2.0
   Via: SIP/2.0/TCP conference.example.com
           ;branch=z9hG4bKhjhs8assmm
   Max-Forwards: 70
   From: "Conference 123" <sip:conf-123@example.com>;tag=88734
   To: <sip:bill@example.com>;tag=29872
   Call-ID: d432fa84b4c34098s812
   CSeq: 34 BYE
   Content-Length: 0

   Figure 4: BYE request


10.  Security Considerations

   The Framework and Security Considerations for SIP URI-List Services
   [10] discusses issues related to SIP URI-list services.  Given that a
   server accepting REFERs with multiple REFER-targets acts as an URI-
   list service, implementations of this type of server MUST follow the
   security-related rules in [10].  These rules include mandatory
   authentication and authorization of clients, and opt-in lists.

   Additionally, servers SHOULD only accept REFER requests within the
   context of an application the server understands (e.g., a
   conferencing application).  This implies that servers MUST NOT accept
   REFERs for methods they do not understand.  The idea behind these two
   rules is that servers are not used as dumb servers whose only
   function is to fan-out random messages they do not understand.


11.  IANA Considerations

   This document defines a new SIP option-tag: "multiple-refer".  This
   option-tag should be registered in the SIP Parameters registry.

   SIP user agents that place the "multiple-refer" option-tag in a
   Supported header field understand REFER requests that contain
   resource list document describing multiple REFER-Targets.


12.  References

12.1.  Normative References

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

   [2]   Troost, R., Dorner, S., and K. Moore, "Communicating



Camarillo, et al.        Expires March 22, 2007                [Page 10]

Internet-Draft               Multiple REFER               September 2006


         Presentation Information in Internet Messages: The Content-
         Disposition Header Field", RFC 2183, August 1997.

   [3]   Levinson, E., "Content-ID and Message-ID Uniform Resource
         Locators", RFC 2392, August 1998.

   [4]   Zimmerer, E., Peterson, J., Vemuri, A., Ong, L., Audet, F.,
         Watson, M., and M. Zonoun, "MIME media types for ISUP and QSIG
         Objects", RFC 3204, December 2001.

   [5]   Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston, A.,
         Peterson, J., Sparks, R., Handley, M., and E. Schooler, "SIP:
         Session Initiation Protocol", RFC 3261, June 2002.

   [6]   Sparks, R., "Internet Media Type message/sipfrag", RFC 3420,
         November 2002.

   [7]   Sparks, R., "The Session Initiation Protocol (SIP) Refer
         Method", RFC 3515, April 2003.

   [8]   Levin, O., "Suppression of Session Initiation Protocol (SIP)
         REFER Method Implicit Subscription", RFC 4488, May 2006.

   [9]   Rosenberg, J., "Extensible Markup Language (XML) Formats for
         Representing Resource Lists",
         draft-ietf-simple-xcap-list-usage-05 (work in progress),
         February 2005.

   [10]  Camarillo, G. and A. Roach, "Framework and Security
         Considerations for Session Initiation Protocol (SIP)  Uniform
         Resource Identifier (URI)-List Services",
         draft-ietf-sipping-uri-services-05 (work in progress),
         January 2006.

   [11]  Garcia-Martin, M. and G. Camarillo, "Extensible Markup Language
         (XML) Format Extension for Representing Capacity  Attributes in
         Resource Lists", draft-ietf-sipping-capacity-attribute-01 (work
         in progress), September 2006.

12.2.  Informative References

   [12]  Rosenberg, J., Schulzrinne, H., and O. Levin, "A Session
         Initiation Protocol (SIP) Event Package for Conference State",
         RFC 4575, August 2006.

   [13]  Johnston, A. and O. Levin, "Session Initiation Protocol (SIP)
         Call Control - Conferencing for User Agents", BCP 119,
         RFC 4579, August 2006.



Camarillo, et al.        Expires March 22, 2007                [Page 11]

Internet-Draft               Multiple REFER               September 2006


   [14]  Rosenberg, J., "Obtaining and Using Globally Routable User
         Agent (UA) URIs (GRUU) in the  Session Initiation Protocol
         (SIP)", draft-ietf-sip-gruu-10 (work in progress), August 2006.
















































Camarillo, et al.        Expires March 22, 2007                [Page 12]

Internet-Draft               Multiple REFER               September 2006


Authors' Addresses

   Gonzalo Camarillo
   Ericsson
   Hirsalantie 11
   Jorvas  02420
   Finland

   Email: Gonzalo.Camarillo@ericsson.com


   Aki Niemi
   Nokia
   P.O. Box 321
   NOKIA GROUP, FIN 00045
   Finland

   Email: Aki.Niemi@nokia.com


   Markus Isomaki
   Nokia
   Itamerenkatu 11-13
   Helsinki  00180
   Finland

   Email: Markus.Isomaki@nokia.com


   Miguel A. Garcia-Martin
   Nokia
   P.O.Box 407
   NOKIA GROUP, FIN  00045
   Finland

   Email: miguel.an.garcia@nokia.com


   Hisham Khartabil
   Telio
   P.O. Box 1203
   Oslo  0110
   Norway

   Email: Hisham.Khartabil@telio.no






Camarillo, et al.        Expires March 22, 2007                [Page 13]

Internet-Draft               Multiple REFER               September 2006


Intellectual Property Statement

   The IETF takes no position regarding the validity or scope of any
   Intellectual Property Rights or other rights that might be claimed to
   pertain to the implementation or use of the technology described in
   this document or the extent to which any license under such rights
   might or might not be available; nor does it represent that it has
   made any independent effort to identify any such rights.  Information
   on the procedures with respect to rights in RFC documents can be
   found in BCP 78 and BCP 79.

   Copies of IPR disclosures made to the IETF Secretariat and any
   assurances of licenses to be made available, or the result of an
   attempt made to obtain a general license or permission for the use of
   such proprietary rights by implementers or users of this
   specification can be obtained from the IETF on-line IPR repository at
   http://www.ietf.org/ipr.

   The IETF invites any interested party to bring to its attention any
   copyrights, patents or patent applications, or other proprietary
   rights that may cover technology that may be required to implement
   this standard.  Please address the information to the IETF at
   ietf-ipr@ietf.org.


Disclaimer of Validity

   This document and the information contained herein are provided on an
   "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
   OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET
   ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED,
   INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE
   INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
   WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.


Copyright Statement

   Copyright (C) The Internet Society (2006).  This document is subject
   to the rights, licenses and restrictions contained in BCP 78, and
   except as set forth therein, the authors retain all their rights.


Acknowledgment

   Funding for the RFC Editor function is currently provided by the
   Internet Society.




Camarillo, et al.        Expires March 22, 2007                [Page 14]


Html markup produced by rfcmarkup 1.108, available from http://tools.ietf.org/tools/rfcmarkup/