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Versions: (draft-kyzivat-sipping-gruu-reg-event) 00 01 02 03 04 05 06 07 08 09 RFC 5628

Sipping                                                       P. Kyzivat
Internet-Draft                                       Cisco Systems, Inc.
Expires: November 18, 2006                                  May 17, 2006

  Registration Event Package Extension for Session Initiation Protocol
             (SIP) Globally Routable User Agent URIs (GRUU)

Status of this Memo

   By submitting this Internet-Draft, each author represents that any
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Copyright Notice

   Copyright (C) The Internet Society (2006).


   RFC 3680 defines a Session Initiation Protocol (SIP) event package
   for registration state.  This package allows a watcher to learn about
   information stored by a SIP registrar, including its registered

   However, the registered contact is frequently unreachable and thus
   not useful for watchers.  The Globally Routable User Agent URI (GRUU)
   has been defined for SIP as a URI that is capable of reaching a

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   particular contact, however this URI is not present in the format
   defined in RFC 3680.  This specification defines an extension to the
   registration event package to include a GRUU.

Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
   2.  Terminology  . . . . . . . . . . . . . . . . . . . . . . . . .  4
   3.  Description  . . . . . . . . . . . . . . . . . . . . . . . . .  4
   4.  Notifier Processing of SUBSCRIBE Requests  . . . . . . . . . .  4
   5.  Notifier Generation of NOTIFY Requests . . . . . . . . . . . .  4
   6.  Subscriber Processing of NOTIFY Requests . . . . . . . . . . .  4
   7.  Sample reginfo Document  . . . . . . . . . . . . . . . . . . .  5
   8.  Examples . . . . . . . . . . . . . . . . . . . . . . . . . . .  5
     8.1.  Example: Welcome Notice  . . . . . . . . . . . . . . . . .  5
     8.2.  Example: Implicit Registration . . . . . . . . . . . . . .  6
   9.  XML Schema Definition  . . . . . . . . . . . . . . . . . . . .  8
   10. IANA Considerations  . . . . . . . . . . . . . . . . . . . . .  9
     10.1. URN Sub-Namespace Registration . . . . . . . . . . . . . .  9
     10.2. XML Schema Registration  . . . . . . . . . . . . . . . . . 10
   11. Security Considerations  . . . . . . . . . . . . . . . . . . . 10
   12. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 10
   13. References . . . . . . . . . . . . . . . . . . . . . . . . . . 10
     13.1. Normative References . . . . . . . . . . . . . . . . . . . 10
     13.2. Informative References . . . . . . . . . . . . . . . . . . 11
   Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 12
   Intellectual Property and Copyright Statements . . . . . . . . . . 13

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1.  Introduction

   RFC 3680 [2] defines a Session Initiation Protocol (SIP) event
   package for registration state.  This package allows a watcher to
   learn about information stored by a SIP registrar, including the
   registered contacts.

   However, a registered contact is frequently unreachable from hosts
   outside of the domain of the user agent.  It is commonly a private
   address, or even when public, direct access to it may be blocked by

   The Globally Routable User Agent URI (GRUU) [3] has been defined as a
   URI that reaches a particular UA instance, but is reachable by any
   host on the Internet.  The GRUU represents another piece of
   registration state.  However, the GRUU is not included in the
   notifications provided by RFC 3860.  For many applications of the
   registration event package, the GRUU is needed, and not the
   registered contact.

   For example, the Welcome Notices example in [2] will only operate
   correctly if the contact address in the reg event notification is
   reachable by the sender of the welcome notice.  When the registering
   device is using the GRUU extension, it is likely that the registered
   contact address will not be globally addressable, and the GRUU should
   be used as the target address for the MESSAGE.

   Another case where this feature may be helpful is within the 3GPP IP
   Multimedia Subsystem (IMS).  IMS employs a technique where a REGISTER
   of a contact address to one Address of Record (AOR) causes the
   implicit registration of the same contact to other associated AORs.
   If a GRUU is requested and obtained as part of the registration
   request, then additional GRUU will also be needed for the implicit
   registrations.  While assigning the additional GRUU is
   straightforward, informing the registering UA of them is not.  In
   IMS, UAs typically subscribe to the "reg" event, and subscriptions to
   the "reg" event for an AOR result in notifications containing
   registration state for all the associated AORs.  The proposed
   extension provides a way to easily deliver the GRUU for the
   associated AORs.

   The reg event package has provision for including extension elements
   within the <contact> element.  This document defines a new element
   that may be used in that context to deliver the GRUU corresponding to
   the contact.

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2.  Terminology

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   document are to be interpreted as described in RFC 2119. [1]

3.  Description

   A new element (<gruu>) is defined which contains a GRUU.

   This optional element is included within the body of a NOTIFY for the
   "reg" event package when a GRUU is associated with the contact.  The
   contact URI and the GRUU are then both available to the watcher.

4.  Notifier Processing of SUBSCRIBE Requests

   Unchanged from RFC 3680 [2].

5.  Notifier Generation of NOTIFY Requests

   A notifier for the "reg" event package [2] SHOULD include the <gruu>
   element when a contact has an Instance ID and a GRUU is associated
   with the combination of the AOR and the Instance ID.  When present,
   the <gruu> element MUST be be positioned as a child of the <contact>

   Note that it is possible for multiple registered contacts to share
   the same instance ID.  In such a case, each <contact> element will
   have a child <gruu> element, and the URI contained within those
   <gruu> elements will be identical.  Since a particular contact can
   not be associated with more than one instance ID, a <contact> element
   will never have more than one <gruu> child element.

   The content of the <gruu> element is the GRUU that is associated with
   the instance ID and AOR of the registered contact.

6.  Subscriber Processing of NOTIFY Requests

   When a subscriber receives a "reg" event notification [2] with a
   <contact> containing a <gruu>, it SHOULD use the GRUU in preference
   to the corresponding <uri> when sending SIP requests to the contact.

   Subscribers that are unaware of this extension will, as required by
   [2], ignore the <gruu> element.

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7.  Sample reginfo Document

      Note: This example and others in the following section are
      indented for readability by the addition of a fixed amount of
      whitespace to the beginning of each line.  This whitespace is not
      part of the example.  The conventions of [8] are used to describe
      representation of long message lines.

   The following is an example registration information document
   including the new element:

      <?xml version="1.0"?>
          <reginfo xmlns="urn:ietf:params:xml:ns:reginfo"
              version="0" state="full">
            <registration aor="sip:user@example.com" id="as9"
              <contact id="76" state="active" event="registered"
                   <unknown-param name="+sip.instance">

8.  Examples

   Note: In the following examples the SIP messages have been
   simplified, removing headers that are not pertinent to the example.

   When the value of the Content-Length header field is "..." this means
   that the value should be whatever the computed length of the body is.

8.1.  Example: Welcome Notice

   Consider the Welcome Notices example in [2].  When the application
   server receives a notification of a new registration containing the
   reginfo shown in Section 7 it should address messages using the

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   contained GRUU as follows:

      MESSAGE sip:user@example.com;gruu;opaque=hha9s8d-999a SIP/2.0
      To: <sip:user@example.com>
      From: "SIPland Notifier" <sip:notifier@example.com>;tag=7xy8
      Content-Type: text/plain
      Content-Length: ...

      Welcome to SIPland!
      Blah, blah, blah.

8.2.  Example: Implicit Registration

   In an 3GPP IMS setting, a UA may send a single register message,
   requesting assignment of a GRUU, as follows:

      REGISTER sip:example.net SIP/2.0
      From: <sip:user_aor_1@example.net>;tag=5ab4
      To: <sip:user_aor_1@example.net>
      Contact: <sip:ua.example.com>
      Supported: path, gruu
      Content-Length: 0

   The response reports success of the registration and returns the GRUU
   assigned for the combination of AOR, Instance ID, and Contact.  It
   also indicates (via the P-Associated-URI header [6]) that there are
   two other associated AORs that may have been implicitly registered
   using the same contact.  Each of those implicitly registered AORs
   will have a unique GRUU assigned.  The REGISTER response will not
   include those GRUU; it will only include the GRUU for the AOR and
   instance ID explicitly included in the registration.

      SIP/2.0 200 OK
      From: <sip:user_aor_1@example.net>;tag=5ab4
      To: <sip:user_aor_1@example.net>;tag=373392
      Path: <sip:proxy.example.net;lr>
      Service-Route: <sip:proxy.example.net;lr>
      Contact: <sip:ua.example.com>
      P-Associated-URI: <sip:user_aor_2@example.net>,
      Content-Length: 0

   The UA then subscribes to the "reg" event package as follows:

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      SUBSCRIBE sip:user_aor_1@example.net SIP/2.0
      From: <sip:user_aor_1@example.net>;tag=27182
      To: <sip:user_aor_1@example.net>
      Route: <sip:proxy.example.net;lr>
      Event: reg
      Expires: 3600
      Accept: application/reginfo+xml
      Contact: <sip:user_aor_1@example.net;gruu;opaque=hha9s8d-999a>
      Content-Length: 0

   (The successful response to the subscription is not shown.)  Once the
   subscription is established an initial notification is sent giving
   registration status.  In IMS deployments the response includes, in
   addition to the status for the requested URI, the status for the
   other associated URIs.

      NOTIFY sip:user_aor_1@example.net;gruu;opaque=hha9s8d-999a SIP/2.0
      From: <sip:user_aor_1@example.net>;tag=27182
      To: <sip:user_aor_1@example.net>;tag=262281
      Subscription-State: active;expires=3600
      Event: reg
      Content-Type: application/reginfo+xml
      Contact: <sip:registrar.example.net>
      Content-Length: ...

      <?xml version="1.0"?>
          <reginfo xmlns="urn:ietf:params:xml:ns:reginfo"
              version="1" state="full">
            <registration aor="sip:user_aor_1@example.net" id="a7"
              <contact id="92" state="active" event="registered"
                 duration-registered="1" expires="3599">
                   <unknown-param name="+sip.instance">
            <registration aor="sip:user_aor_2@example.net" id="a8"

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              <contact id="93" state="active" event="created"
                 duration-registered="1" expires="3599">
                   <unknown-param name="+sip.instance">
              <contact id="94" state="active" event="created"
                 duration-registered="1" expires="3599">
                   <unknown-param name="+sip.instance">

   The status indicates that the associated URIs all have the same
   contact registered.  It also includes the unique GRUU that has been
   assigned to each.  The UA may then retain those GRUU for use when
   establishing dialogs using the corresponding AORs.

9.  XML Schema Definition

   The <gruu> element is defined within a new XML namespace URI.  This

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   namespace is "urn:ietf:params:xml:ns:gruuinfo".  The schema for the
   <gruu> element is:

   <?xml version="1.0" encoding="UTF-8"?>
   <xs:schema targetNamespace="urn:ietf:params:xml:ns:gruuinfo"
     <xs:element name="gruu" type="xs:anyURI"/>

10.  IANA Considerations

   There are two IANA considerations associated with this specification.

10.1.  URN Sub-Namespace Registration

   This section registers a new XML namespace, per the guidelines in

   URI: The URI for this namespace is urn:ietf:params:xml:ns:gruuinfo

   Registrant Contact: IETF, SIPPING working group, <sipping@ietf.org>,
   Paul Kyzivat <pkyzivat@cisco.com>


         <?xml version="1.0"?>
         <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML Basic 1.0//EN"
         <html xmlns="http://www.w3.org/1999/xhtml">
           <meta http-equiv="content-type"
           <title>Reg Information GRUU Extension Namespace</title>
            <h1>Namespace for Reg Information GRUU Extension</h1>
            <p>See <a href="[URL of published RFC]">RFCXXXX [[NOTE
      TO RFC-EDITOR/IANA: Please replace XXXX with the RFC Number of
      this specification]]</a>.</p>

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10.2.  XML Schema Registration

   This section registers an XML schema per the procedures in [4].

   URI: urn:ietf:params:xml:schema:gruuinfo.

   Registrant Contact: IETF, SIPPING working group, <sipping@ietf.org>,
   Paul Kyzivat <pkyzivat@cisco.com>

   The XML for this schema can be found in Section 9.

11.  Security Considerations

   Security considerations for the registration event package is
   discussed in RFC 3680 [2], and those considerations apply here.

   If the contact address is not reachable by the subscriber to the
   registration event package, then its disclosure may arguably be
   considered of minimal security risk.  In that case the inclusion of
   the GRUU may be considered to increase the risk by providing a
   reachable address.  On the other hand, requests addressed to the GRUU
   are always first processed by the servicing proxy before they reach
   the intended user agent.  The proxy may control access as desired,
   just as it may for the AOR.  In this respect disclosing the GRUU
   presents no more risk than disclosing the AOR.

12.  Acknowledgements

   The author would like to thank Jonathan Rosenberg for encouraging
   this draft, and Jari Urpalainen for assistance with the XML.

13.  References

13.1.  Normative References

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

   [2]  Rosenberg, J., "A Session Initiation Protocol (SIP) Event
        Package for Registrations", RFC 3680, March 2004.

   [3]  Rosenberg, J., "Obtaining and Using Globally Routable User Agent

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        (UA) URIs (GRUU) in the  Session Initiation Protocol (SIP)",
        draft-ietf-sip-gruu-07 (work in progress), May 2006.

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

13.2.  Informative References

   [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]  Garcia-Martin, M., Henrikson, E., and D. Mills, "Private Header
        (P-Header) Extensions to the Session Initiation Protocol (SIP)
        for the 3rd-Generation Partnership Project (3GPP)", RFC 3455,
        January 2003.

   [7]  Rosenberg, J., Schulzrinne, H., and P. Kyzivat, "Indicating User
        Agent Capabilities in the Session Initiation Protocol (SIP)",
        RFC 3840, August 2004.

   [8]  Sparks, R., "Session Initiation Protocol Torture Test Messages",
        draft-ietf-sipping-torture-tests-09 (work in progress),
        November 2005.

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Author's Address

   Paul H. Kyzivat
   Cisco Systems, Inc.
   1414 Massachusetts Avenue
   Boxborough, MA  01719

   Email: pkyzivat@cisco.com

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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
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   This document and the information contained herein are provided on an

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.


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

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