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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.
Intended status: Informational                          October 19, 2006
Expires: April 22, 2007


  Registration Event Package Extension for Session Initiation Protocol
            (SIP) Globally Routable User Agent URIs (GRUUs)
                  draft-ietf-sipping-gruu-reg-event-08

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
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   Internet-Drafts are working documents of the Internet Engineering
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   This Internet-Draft will expire on April 22, 2007.

Copyright Notice

   Copyright (C) The Internet Society (2006).

Abstract

   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
   contact.

   However, the registered contact is frequently unreachable and thus
   not useful for watchers.  The Globally Routable User Agent URI



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   (GRUU), defined in RFC YYYY [3], is a URI that is capable of reaching
   a particular contact.  However this URI is not included in the
   document format defined in RFC 3680.  This specification defines an
   extension to the registration event package to include GRUUs assigned
   by the registrar.

      [[NOTE TO RFC-EDITOR/IANA: Please replace YYYY throughout this
      document with the RFC number assigned to the referenced draft [3]
      when it is published.]]


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 . . . . . . . . . . .  5
   7.  Sample reginfo Document  . . . . . . . . . . . . . . . . . . .  5
   8.  Examples . . . . . . . . . . . . . . . . . . . . . . . . . . .  6
     8.1.  Example: Welcome Notice  . . . . . . . . . . . . . . . . .  6
     8.2.  Example: Implicit Registration . . . . . . . . . . . . . .  7
   9.  XML Schema Definition  . . . . . . . . . . . . . . . . . . . . 10
   10. IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 10
     10.1. URN Sub-Namespace Registration . . . . . . . . . . . . . . 10
     10.2. XML Schema Registration  . . . . . . . . . . . . . . . . . 11
   11. Security Considerations  . . . . . . . . . . . . . . . . . . . 11
   12. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 12
   13. References . . . . . . . . . . . . . . . . . . . . . . . . . . 12
     13.1. Normative References . . . . . . . . . . . . . . . . . . . 12
     13.2. Informative References . . . . . . . . . . . . . . . . . . 13
   Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 13
   Intellectual Property and Copyright Statements . . . . . . . . . . 14

















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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
   firewalls.

   The Globally Routable User Agent URI (GRUU), defined in RFC YYYY [3],
   is a URI that reaches a particular UA instance, but is reachable by
   any host on the Internet.  GRUUs assigned by the registrar represent
   additional registration state.  However, GRUUs assigned by the
   registrar are not included in the notifications provided by RFC 3680.
   For many applications of the registration event package, a 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 a 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 GRUUs are requested and obtained as part of the registration
   request, then additional GRUUs will also be needed for the implicit
   registrations.  While assigning the additional GRUUs 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 GRUUs for the
   associated AORs.

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






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2.  Terminology

   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. [1]


3.  Description

   Two new elements (<pub-gruu> and <temp-gruu>) are defined, each of
   which contains a GRUU.

   These optional elements may be included within the body of a NOTIFY
   for the "reg" event package when GRUUs are associated with the
   contact.  The contact URI and the GRUUs are then all 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 <pub-
   gruu> element when a contact has an Instance ID and a public GRUU is
   associated with the combination of the AOR and the Instance ID.  When
   present, the <pub-gruu> element MUST be be positioned as a child of
   the <contact> element.

   A notifier for the "reg" event package [2] MAY include the <temp-
   gruu> element when a contact has an Instance ID and a temporary GRUU
   is associated with the combination of the AOR and the Instance ID.
   This element SHOULD be included if the subscriber is also authorized
   to register to the AOR.  This element SHOULD NOT be included if the
   subscriber is not authorized to register to the AOR, unless there is
   an explicitly configured policy directing that it be included.  When
   present, the <temp-gruu> element MUST be be positioned as a child of
   the <contact> element.

   Note that it is possible for multiple registered contacts to share
   the same instance ID.  In such a case, each <contact> element will
   have child <pub-gruu> and <temp-gruu> elements, and those child
   elements of each <contact> element 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 <pub-gruu> and
   one <temp-gruu> child element.



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

   The content of the <temp-gruu> element is the temporary 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 <pub-gruu> and/or <temp-gruu>, it SHOULD use
   one of the GRUUs 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 <pub-gruu> and <temp-gruu> elements.


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 [7] are used to describe
      representation of long message lines.

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























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      <?xml version="1.0"?>
          <reginfo xmlns="urn:ietf:params:xml:ns:reginfo"
              xmlns:gr="urn:ietf:params:xml:ns:gruuinfo"
              version="0" state="full">
            <registration aor="sip:user@example.com" id="as9"
                 state="active">
              <contact id="76" state="active" event="registered"
                 duration-registered="7322"
                 q="0.8">
                   <uri>sip:user@192.0.2.1</uri>
      <allOneLine>
                   <unknown-param name="+sip.instance">
      "&lt;urn:uuid:f81d4fae-7dec-11d0-a765-00a0c91e6bf6&gt;"
      </unknown-param>
      </allOneLine>
      <allOneLine>
                   <gr:pub-gruu>sip:user@example.com
      ;gr=hha9s8d-999a</gr:pub-gruu>
      </allOneLine>
      <allOneLine>
                   <gr:temp-gruu>sip:8ffkas08af7fasklzi9@example.com
      ;gr</gr:temp-gruu>
      </allOneLine>
              </contact>
            </registration>
          </reginfo>


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
   contained public GRUU as follows:









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      MESSAGE sip:user@example.com;gr=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 GRUUs, 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>
        ;expires=3600
        ;+sip.instance="<urn:uuid:f81d4fae-7dec-11d0-a765-00a0c91e6bf6>"
      Supported: path, gruu
      Content-Length: 0

   The response reports success of the registration and returns the
   GRUUs 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 unique GRUUs assigned.  The REGISTER
   response will not include those GRUUs; it will only include the GRUUs
   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>
        ;expires=3600
        ;+sip.instance="<urn:uuid:f81d4fae-7dec-11d0-a765-00a0c91e6bf6>"
        ;pub-gruu="sip:user_aor_1@example.net;gr=hha9s8d-999a"
        ;temp-gruu="sip:8ffkas08af7fasklzi9@example.net;gr"
      P-Associated-URI: <sip:user_aor_2@example.net>,
        <sip:+358504821437@example.net;user=phone>
      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;gr=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;gr=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"
              xmlns:gr="urn:ietf:params:xml:ns:gruuinfo"
              version="1" state="full">
            <registration aor="sip:user_aor_1@example.net" id="a7"
                 state="active">
              <contact id="92" state="active" event="registered"
                 duration-registered="1" expires="3599">
                   <uri>
                      sip:ua.example.com
                   </uri>
      <allOneLine>
                   <unknown-param name="+sip.instance">
      "&lt;urn:uuid:f81d4fae-7dec-11d0-a765-00a0c91e6bf6&gt;"
      </unknown-param>
      </allOneLine>
      <allOneLine>
                   <gr:pub-gruu>sip:user_aor_1@example.net
      ;gr=hha9s8d-999a</gr:pub-gruu>
      </allOneLine>
      <allOneLine>
                   <gr:temp-gruu>sip:8ffkas08af7fasklzi9@example.net
      ;gr</gr:temp-gruu>



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      </allOneLine>
              </contact>
            </registration>
            <registration aor="sip:user_aor_2@example.net" id="a8"
                 state="active">
              <contact id="93" state="active" event="created"
                 duration-registered="1" expires="3599">
                   <uri>
                      sip:ua.example.com
                   </uri>
      <allOneLine>
                   <unknown-param name="+sip.instance">
      "&lt;urn:uuid:f81d4fae-7dec-11d0-a765-00a0c91e6bf6&gt;"
      </unknown-param>
      </allOneLine>
      <allOneLine>
                   <gr:pub-gruu>sip:user_aor_2@example.net
      ;gr=hha9s8d-999b</gr:pub-gruu>
      </allOneLine>
      <allOneLine>
                   <gr:temp-gruu>sip:07hcovy36vp6vngvbia@example.net
      ;gr</gr:temp-gruu>
      </allOneLine>
              </contact>
            </registration>
            <registration
                 aor="sip:+358504821437@example.net;user=phone"
                 id="a9"
                 state="active">
              <contact id="94" state="active" event="created"
                 duration-registered="1" expires="3599">
                   <uri>
                      sip:ua.example.com
                   </uri>
      <allOneLine>
                   <unknown-param name="+sip.instance">
      "&lt;urn:uuid:f81d4fae-7dec-11d0-a765-00a0c91e6bf6&gt;"
      </unknown-param>
      </allOneLine>
      <allOneLine>
                   <gr:pub-gruu>sip:+358504821437@example.net;user=phone
      ;gr=hha9s8d-999c</gr:pub-gruu>
      </allOneLine>
      <allOneLine>
                   <gr:temp-gruu>sip:h99egjbv17fe8ibvlka@example.net
      ;gr</gr:temp-gruu>
      </allOneLine>
              </contact>



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            </registration>
          </reginfo>

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


9.  XML Schema Definition

   The <pub-gruu> and <temp-gruu> elements are defined within a new XML
   namespace URI.  This namespace is "urn:ietf:params:xml:ns:gruuinfo".
   The schema for these elements is:


   <?xml version="1.0" encoding="UTF-8"?>
   <xs:schema targetNamespace="urn:ietf:params:xml:ns:gruuinfo"
     elementFormDefault="qualified"
     attributeFormDefault="unqualified"
     xmlns:xs="http://www.w3.org/2001/XMLSchema"
     xmlns:tns="urn:ietf:params:xml:ns:gruuinfo">
     <xs:element name="pub-gruu" type="xs:anyURI"/>
     <xs:element name="temp-gruu" type="xs:anyURI"/>
   </xs:schema>


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
   [4].

   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:









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         BEGIN
         <?xml version="1.0"?>
         <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML Basic 1.0//EN"
                   "http://www.w3.org/TR/xhtml-basic/xhtml-basic10.dtd">
         <html xmlns="http://www.w3.org/1999/xhtml">
         <head>
           <meta http-equiv="content-type"
              content="text/html;charset=iso-8859-1"/>
           <title>Reg Information GRUU Extension Namespace</title>
         </head>
         <body>
            <h1>Namespace for Reg Information GRUU Extension</h1>
            <h2>urn:ietf:params:xml:ns:gruuinfo</h2>
            <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>
          </body>
         </html>
         END

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 are
   discussed in RFC 3680 [2], and those considerations apply here.

   If a contact address obtained via subscription to the registration
   event package is not reachable by the subscriber then its disclosure
   may arguably be considered a minimal security risk.  In that case the
   inclusion of a GRUU may be considered to increase the risk by
   providing a reachable address.  On the other hand requests addressed
   to a 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.  For instance, the proxy
   servicing a GRUU may accept requests from senders whose identity
   appears on a white list, and reject other requests.  In this respect
   disclosing a GRUU presents no more risk than disclosing the AOR.



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   Temporary GRUUs have an additional security consideration.  The
   intent of the temporary GRUU is to provide a contact address that
   cannot be correlated to the identity of the calling party.  The
   recipient of a call using a temporary GRUU may guess the identity of
   the calling party and then attempt to obtain the temporary GRUUs
   assigned to that caller to confirm the conjecture.  Two possible
   approaches to obtaining the temporary GRUUs are:

   o  Send a REGISTER request to a conjectured caller.
   o  Send a SUBSCRIBE request for the "reg" event package to the
      conjectured caller.

   Typically REGISTER is restricted to devices or users that are
   authorized to originate and received calls with the AOR.  Anonymity
   among users of the same AOR is hard to achieve and typically
   unnecessary.  It is recommended (see Section 5) that the
   authorization policy for the "reg" event package permit only those
   subscribers authorized to register to the AOR to receive temporary
   GRUUs.  With this policy, the confidentiality of the temporary GRUU
   will be the same with and without the "reg" event package.  User
   agents that use a temporary GRUU should note that confidentiality
   does not extend to parties that are permitted to register to the AOR
   or obtain the temporary GRUU when subscribing the "reg" event
   package.


12.  Acknowledgements

   The author would like to thank Jonathan Rosenberg for help with 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
        (UA) URIs (GRUU) in the  Session Initiation Protocol (SIP)",
        draft-ietf-sip-gruu-11 (work in progress), April 2007.

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



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


Author's Address

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

   Email: pkyzivat@cisco.com


























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Full 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.

   This document and the information contained herein are provided on an
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   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
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   http://www.ietf.org/ipr.

   The IETF invites any interested party to bring to its attention any
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Acknowledgment

   Funding for the RFC Editor function is provided by the IETF
   Administrative Support Activity (IASA).





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