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Versions: 00 01 02                                                      
Internet Engineering Task Force                           James M. Polk
Internet Draft                                            Cisco Systems
Expiration: April 25th, 2005                                Brian Rosen
File: draft-ietf-sipping-location-requirements-02.txt         Emergicom




                           Requirements for
           Session Initiation Protocol Location Conveyance


                          October 25th, 2004


Status of this Memo


   By submitting this Internet-Draft, I certify that any applicable
   patent or other IPR claims of which I am aware have been disclosed,
   and any of which I become aware will be disclosed, in accordance
   with RFC 3668.


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Copyright Notice


   Copyright (C) The Internet Society (2004).  All Rights Reserved.



Abstract


   This document presents the framework and requirements for usage of
   the Session Initiation Protocol (SIP) to convey user location
   information from one Session Initiation Protocol (SIP) entity to
   another SIP entity.  We consider cases where location information is
   conveyed from end to end, as well as cases where message routing by
   intermediaries is influenced by the location of the session
   initiator.  We offer a set of solutions to the requirements, based
   on the scenario(s) being addressed.




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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .  2
       1.1 Conventions . . . . . . . . . . . . . . . . . . . . . . .  3
       1.2 Changes from Prior Versions . . . . . . . . . . . . . . .  3
   2.  In the Body or in a Header  . . . . . . . . . . . . . . . . .  5
   3.  Scope of Location in a Message Body . . . . . . . . . . . . .  6
   4.  Requirements for UA-to-UA Location Conveyance . . . . . . . .  7
   5.  Requirements for UA-to-Proxy Server Location Conveyance . . .  7
   6.  Additional Requirements for Emergency Calls . . . . . . . . .  8
   7.  Location Conveyance Using SIP . . . . . . . . . . . . . . . . 10
   8.  Location Conveyance UA-to-UA  . . . . . . . . . . . . . . . . 12
       8.1 UA-to-UA Using INVITE . . . . . . . . . . . . . . . . . . 12
         8.1.1 UA-to-UA Using INVITE with Coordinate Format. . . . . 13
         8.1.2 UA-to-UA Using INVITE with Civic Format . . . . . . . 15
         8.1.3 UA-to-UA Using INVITE Involving 3 Users . . . . . . . 18
       8.2 UA-to-UA Using MESSAGE  . . . . . . . . . . . . . . . . . 24
       8.3 UA-to-UA Using UPDATE . . . . . . . . . . . . . . . . . . 27
       8.4 UA-to-UA Using PUBLISH  . . . . . . . . . . . . . . . . . 32
       8.5 UA-to-UA Location Conveyance Using SUBSCRIBE and NOTIFY . 32
       8.6 424 "Bad Location Information" Error Response . . . . . . 32
   9.  Special Considerations for Emergency Calls  . . . . . . . . . 32
       9.1 UA-to-Proxy Using INVITE  . . . . . . . . . . . . . . . . 33
       9.2 UA-to-Proxy Using UPDATE  . . . . . . . . . . . . . . . . 38
       9.3 425 "Retry Location Body" Error Response  . . . . . . . . 42
   10. Meeting RFC 3693 Requirements . . . . . . . . . . . . . . . . 43
   11. Current Known Open issues . . . . . . . . . . . . . . . . . . 43
   12. New Open issues . . . . . . . . . . . . . . . . . . . . . . . 44
   13. Security Considerations . . . . . . . . . . . . . . . . . . . 44
   14. IANA Considerations   . . . . . . . . . . . . . . . . . . . . 44
       14.1 IANA Registration for Response Code 424  . . . . . . . . 45
       14.2 IANA Registration for Response Code 425  . . . . . . . . 45
   15. Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . 45
   16. References  . . . . . . . . . . . . . . . . . . . . . . . . . 45
       16.1 Normative References   . . . . . . . . . . . . . . . . . 45
   17. Author Information  . . . . . . . . . . . . . . . . . . . . . 46



1.  Introduction


   This document presents the framework and requirements for the usage
   of the Session Initiation Protocol (SIP) [1] for conveyance of user
   location information described by [7] from a SIP entity to another
   SIP entity.


   There are several situations in which it is appropriate for SIP to
   be used to convey Location Information (LI) from one SIP entity to
   another.  This document specifies requirements when a SIP UAC knows
   its location by some means not specified herein, and needs to inform
   another SIP entity.  One example is one user agent informing another
   user agent where it is (you want to tell your friend where you are).




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   Another example is to reach your nearest pizza parlor.  A chain of
   pizza parlors may have a single well known uri
   (sip:pizzaparlor.com), that is forwarded to the closest franchise by
   the pizzaparlor.com proxy server.  The receiving franchise UAS uses
   the location information of the UAC to schedule your delivery.


   Another important example is emergency calling.  A call to
   sip:sos@example.com is an emergency call as in [3].  The example.com
   proxy server must route the call to the correct emergency response
   center (ERC) determined by the location of the caller. At the ERC,
   the UAS must determine the correct police/fire/ambulance/...
   service, which is also based on your location.  In many
   jurisdictions, precise location information of the caller in
   distress is a required component of a call to an emergency center.


   A forth example is a direction service, which might give you verbal
   directions to a venue from your present position.  This is a case
   where only the destination UAS needs to receive the location
   information.


   This document does not discuss how the UAC discovers or is
   configured with its location (either coordinate or civic based).  It
   also does not discuss the contents of the Location Object (LO).  It
   does specify the requirements for the "using protocol" as defined by
   Geopriv in [7].


   Sections 7, 8 and 9 give specific examples (in well-formed SIP
   messages) of SIP UA and Proxy behavior for location conveyance, the
   last of which is a section devoted to the unique circumstances
   regarding emergency calling.  Section 10 addresses how this document
   adheres to the requirements specified in [7] (Geopriv Requirements).
   Sections 11 and 12 list the current open issues with location
   conveyance in SIP, and the new open issues recently discovered as a
   result of the added effort to this revision.



1.1  Conventions used in this document


   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 [2].



1.2  Changes from Prior Versions


[NOTE TO RFC-EDITOR: If this document is to be published as an RFC,
this section is to be removed prior to that event.]


   This is a list of the changes that have been made from the -01
   working group version of this effort to this -02 version:




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   - added requirements for 2 new 4XX error responses (Bad Location
     Information) and (Retry Location Body)


   - added "Bad Location Information" as section 8.6


   - added "Retry Location Body " as section 9.3


   - added support for session mode to cover packet sizes larger than
     the single packet limit of 1300 bytes in the message body


   - added requirement for a SIP entity to SUBSCRIBE to another for
     location information


   - added SUBSCRIBE and NOTIFY as section 8.5


   - added requirement to have user turn off any tracking created by
     subscription


   - removed doubt about which method to use for updating location
     after a INVITE is sent (update)


   - cleaned up which method is to be used if there is no dialog
     existing (message)


   - removed use of reINVITE to convey location


   - clarified that UAs include <provided-by> element of PIDF-LO when
     placing an emergency call (to inform ERC who supplied Location
     information)


   - updated list of open issues


   - added to IANA Considerations section for the two new 4XX level
     error responses requested in the last meeting


   This is a list of the changes that have been made from the -00
   working group version of this ID to this version:


   - Added the offered solution in detail (with message flows,
     appropriate SIP Methods for location conveyance, and


   - Synchronized the requirements here with those from the Geopriv
     Working Group's (attempting to eliminate overlap)


   - Took on the task of making this effort the SIP "using protocol"
     specification from Geopriv's POV


   - Refined the Open Issues section to reflect the progress we've made
     here, and to indicate what we have discovered needs addressing,
     but has not been to date.


   This is a list of the changes that have been made from the -01



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   individual submission version to the WG -00 version of this ID:


   - Brian Rosen was brought on as a co-author


   - Requirements that a location header were negatively received in
     the previous version of this document.  AD and chair advice was to
     move all location information into a message body (and stay away
     from headers)


   - Added a section of "emergency call" specific requirements


   - Added an Open Issues section to mention what hasn't been resolved
     yet in this effort


   This is a list of the changes that have been made from the
   individual submission version -00 to the -01 version


   - Added the IPR Statement section


   - Adjusted a few requirements based on suggestions from the
     Minneapolis meeting


   - Added requirements that the UAC is to include from where it
     learned its location in any transmission of its LI


   - Distinguished the facts (known to date) that certain jurisdictions
     relieve persons of their right to privacy when they call an ERC,
     while other jurisdictions maintain a person's right to privacy,
     while still others maintain a person's right to privacy - but only
     if they ask that their service be set up that way.


   - Made the decision that TLS is the security mechanism for location
     conveyance in emergency communications (vs. S/MIME, which is still
     the mechanism for UA-to-UA non-emergency location conveyance
     cases).


   - Added the Open Issue of whether a Proxy can insert location
     information into an emergency SIP INVITE message, and some of the
     open questions surrounding the implications of that action


   - added a few names to the acknowledgements section



2.  In the Body or in a Header


   When one user agent wants to inform another user agent where they
   are, it seems reasonable to have this accomplished by placing the
   location information (coordinate or civic) in an S/MIME registered
   and encoded message body, and sending it as part of a SIP request or
   response.  No routing of the request based on the location
   information is required in this case; therefore no SIP Proxies
   between these two UAs need to view the location information



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   contained in the SIP messages.


   Although SIP [1} does not permit a proxy server to modify or delete
   a body, there is no restriction on viewing bodies.  However, S/MIME
   protection implemented on bodies is only specified between UAC and
   UAS, and if engaged, would render the location object opaque to a
   proxy server for any desired modification if it is not correct or
   precise enough from that proxy's point of view (were it to be able
   to view it).  This problem is similar to that raised in Session
   Policy [8], where an intermediary may need information in a body,
   such as IP address of media streams or codec choices to route a call
   properly.  Requirements in [8] are applicable to routing based on
   location, and are incorporated in these requirements by reference.


   It is conceivable to create a new header for location information.
   However, [7] prefers S/MIME for security of Location Information,
   and indeed S/MIME is preferable in SIP for protecting one part of a
   message.  Accordingly, these requirements specify location be
   carried in a body.


   It is the use of S/MIME however, that limits routing based on
   location.  Therefore, it seems appropriate to require that, where
   routing is dependent on location, protection of the location
   information object be accomplished by other mechanisms: here TLS
   ("sips:" from [1]).  It is envisioned that S/MIME SHOULD be used
   when location information is not required by proxy servers, and TLS
   MUST be used when it is.  The UAC will need to know the difference
   in the call's intent as to which security mechanism to engage for LI
   conveyance.


   This document does not address the behavior or configuration of SIP
   Proxy Servers in these cases in order to accomplish location-
   sensitive routing.  That is out of scope, and left for further
   (complementary) efforts.



3.  Scope of Location in a Message Body


   As concluded from the previous section, location information is to
   be contained within a message body.  If either another body (SDP for
   example) is also to be sent in the message, or the LI is to be
   protected with S/MIME, the rules stated in section 7 of [1]
   regarding multipart MIME bodies MUST be followed.  The format and
   privacy/security rules of the location information SHOULD be defined
   within the Geopriv WG.


   User agents providing location can perform this function
   incorrectly.  Therefore, there needs to be a UAC error response code
   created to inform the UAC by a UAS or Proxy of this incorrect
   request message containing location information.


   There will be times in which the UAC does not know its location



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   information, or another SIP entity knows the UAC's location better
   than the UAC itself.  How this is determined is out of scope of this
   document.  In these times, a Proxy servers that knows the location
   of the UAC needs inform the UAC of its location information and have
   that UAC include that message body in its next SIP message to the
   same destination UA.  This error code needs to be unique with
   respect to the error code for merely incorrect location information
   from the UAC.



4.  Requirements for UA-to-UA Location Conveyance


   The following are the requirements for UA-to-UA Location Conveyance
   Situations where routing is not based on the LI of either UA:


    U-U1 - MUST work with dialog-initiating SIP Requests and responses,
           as well as the SIP MESSAGE method [4], and SHOULD work with
           most SIP messages.


    U-U2 - UAC Location information SHOULD remain confidential in route
           to the destination UA.


    U-U3 - The privacy and security rules established within the
           Geopriv Working Group that would categorize SIP as a 'using
           protocol' MUST be met [7].


    U-U4 - Location information MUST be contained in the location
           Object as defined in [13], which will satisfy all format
           requirements for interoperability.


    U-U5 - SHOULD be able to communicate location between user agents
           with as many packets as is necessary.


    U-U6 - There MUST be a unique UAC error response code informing the
           UAC is did not provide valid location information.



5.  Requirements for UA-to-Proxy Server Location Conveyance


   The following are the requirements for UA-to-Proxy Server Location
   Conveyance situations:


    U-PS1 - MUST work with dialog-initiating SIP Requests and
            responses, as well as the SIP MESSAGE method[4], and SHOULD
            work with most SIP messages.


    U-PS2 - UAC location information SHOULD remain confidential with
            respect to entities to which the location information is
            not addressed, but MUST be useable by intermediary proxy
            servers.


    U-PS3 - The privacy and security rules established within the



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            Geopriv Working Group which would categorize SIP as a
            'using protocol' MUST be met [7].


    U-PS4 - Modification or removal of the LO by proxy servers MUST NOT
            be required (as [1] currently forbids this).


    U-PS5 - any mechanism used to prevent unwanted observation of this
            Location Information MUST NOT fail the SIP Request if not
            understood by intermediary SIP entities or the destination
            UAS.


    U-PS6 - Proxy Servers that do not or cannot understand the Location
            Information in the message body for routing purposes MUST
            NOT fail the SIP Request.


    U-PS7 ¡ It MUST be possible for a proxy server to assert the
            validity of the location information provided by the UA.
            Alternatively, it is acceptable for there to be a mechanism
            for a proxy server to assert a location object itself.


    U-PS8 - There MUST be a unique UAC error response code informing
            the UAC is did not provide valid location information.


    U-PS9 - There MUST be a unique UAC error response code informing
            the UAC it did not provide valid location information, and
            to include the location information contained in the
            message body of the error message in its next attempt to
            the same UAS of the original message.



6. Additional Requirements for Emergency Calls


   Emergency calls have requirements that are not generally important
   to other uses for location in SIP:


   Emergency calls presently have between 2 and 8-second call setup
   times.  There is ample evidence that the longer call setup end of
   the range causes an unacceptable number of callers to abandon the
   call before it is completed.  Two-second call completion time is a
   goal of many existing emergency call centers.  Allocating 25% of the
   call set up for processing privacy concerns seems reasonable; 1
   second would be 50% of the goal, which seems unacceptable; less than
   0.5 second seems unachievable, therefore:


    E-1 - Privacy mechanisms MUST add no more than 0.5 second of call
          setup time when implemented in present technology UAs and
          Proxy Servers.


   It may be acceptable for full privacy mechanisms related to the
   location of the UAC (and it's user) to be tried on an initial
   attempt to place a call, as long as the call attempt may be retried
   without the mechanism if the first attempt fails.  Abandoning



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   privacy in cases of failure of the privacy mechanism might be
   subject to user preference, although such a feature would be within
   the domain of a UA implementation and thus not subject to
   standardization.  It should be noted that some jurisdictions have
   laws that explicitly deny any expectation of location privacy when
   making an emergency call, while others grant the user the ability to
   remain anonymous even when calling an ERC.  So far, this has been
   offered in some jurisdictions, but the user within that jurisdiction
   must state this preference, as it is not the default configuration.


    E-2 ¡ Privacy mechanisms MUST NOT be mandatory for successful
          conveyance of location during an (sos-type) emergency call.


    E-3 - It MUST be possible to provide a privacy mechanism (that does
          not violate the other requirements within this document) to a
          user within a jurisdiction that gives that user the right to
          choose not to reveal their location even when contacting an
          ERC.



    E-4 ¡ The retention and retransmission policy of the ERC MUST be
          able to be made available to the user, and override the
          user's normal policy when local regulation governs such
          retention and retransmission (but does not violate
          requirement E-3).  As in E-2 above, requiring the use of the
          ERC's retention and/or retransmission policy may be subject
          to user preference; although in most jurisdictions, local
          laws specify such policies and may not be overridden by user
          preference.


   Location information is considered so important during emergency
   calls, that it is to be transmitted even when it is not considered
   reliable, or might even be wrong.  For example, some application
   might know that the DHCP reply with location information was
   overwritten recently (or exactly) when a VPN connection was
   activated.  This could, and likely will, provide any new location
   information to the UA from somewhere far away from the UA (perhaps
   the user's corporate facility).


    E-5 Location information MUST be transmitted, if known to the UAC,
        in all calls to an ERC, even in the case it is not considered
        reliable.


   With that in mind, it is important to distinguish the location
   information learned locally from LI learned over a VPN; which in
   itself is useful additional information to that ERC operator.


    E-7 THE UA must provide the actual LI of the endpoint, and not
        location which might have been erroneously given to it by, e.g.
        a VPN tunnel DHCP server.


    E-8 An ERC MAY wish to SUBSCRIBE to the UAC that initiated a



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        session.  If this is supported by the UAC, all NOTIFY messages
        MUST contain the UAC's location information.


   This is a means for the emergency response centers to maintain a
   location the callers in distress.


    E-9 It MUST be possible that any UAC supporting E-8 be informed of
        this subscription, as this will provide a means of alert to the
        user who does not wish this capability to remain enabled.



7.  Location Conveyance using SIP


   Geopriv is the IETF working group assigned to define a Location
   Object for carrying within another protocol to convey geographic
   location of an endpoint to another entity.  This Location Object
   will be supplied within SIP to convey location of a UA (or user of a
   UA).  The Location Object (LO) is defined in [13]. Section 26 of [1]
   defines the security functionality SIPS for transporting SIP
   messages with either TLS or IPsec, and S/MIME for encrypting message
   bodies from SIP intermediaries that would otherwise have access to
   reading the clear-text bodies.  For UA-to-UA location conveyance,
   using the PIDF-LO body satisfies the entire format and message-
   handling requirements as stated in the baseline Geopriv requirements
   [7].  SIP entities that will carry an LO MUST implement S/MIME for
   encrypting on an end-to-end basis the location of a user agent,
   satisfying [7]'s security requirements.  The SIPS-URI from [1]
   SHOULD also be used for further message protection (message
   integrity, authentication and message confidentiality) and MUST be
   used when S/MIME is not used.  The entities sending and receiving
   the LO MUST obey the privacy and security instructions in the
   LO to be compliant with this specification.


   Self-signed certificates SHOULD NOT be used for protecting LI, as
   the sender does not have a secure identity of the recipient.


   Several LOs MAY be included in a body.  If the message length
   exceeds the maximum message length of a single packet, session mode
   is to be used.


   Several SIP Methods are capable (and applicable) to carry the LO.
   The Methods are divided into two groups, one for those applicable
   for UA-to-UA location conveyance, and the other group for UA-to-
   Proxy Location conveyance for routing the message.


   The list of applicable Methods for UA-to-UA location conveyance is:


      INVITE,
      UPDATE,
      MESSAGE, and
      PUBLISH.




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   The list of applicable Methods for UA-to-Proxy location conveyance
   is:


      INVITE,
      UPDATE,
      MESSAGE, and
      SUBSCRIBE/NOTIFY


   While the authors do not yet see a reason to have location conveyed
   in the OPTIONS, ACK, PRACK, BYE, REFER and CANCEL Methods, we do not
   see a reason to prevent carrying a LO within these Method Requests
   as long as the SIP message meets the requirements stated within this
   document.


   A 200 OK to an INVITE MAY carry the UAS's LO back to the UAC that
   provided its location in the INVITE, but this is not something
   that can be required due to the timing of the INVITE to 200 OK
   messages, with potential local/user policy requiring the called user
   to get involved in determining if the caller is someone they wish to
   give location to (and at what precision).


   There is an open question as to whether there needs to be a new
   event package created for a SUBSCRIBE such that one SIP entity
   (perhaps a service using SIP) can request the ability to have a
   remote UA's location refreshed at some interval.  This idea is not
   explored further in this version of the document.  The capability to
   have location information refreshed between devices is out of scope
   within the Geopriv working group at this time, but could easily
   become part of the "using protocol's" capabilities without violating
   any of the Geopriv Requirements in [7].  The authors want feedback
   on incorporating this into this document, or a separate document.


   For UA-to-Proxy location conveyance, there are two cases: one in
   which all proxies on the path from the UA to the proxy that requires
   location can be trusted with the LI, and one in which intermediate
   proxies may not be trusted.  The former may be implemented with
   "hop-by-hop" security as specified in [1] using sips: (i.e. TLS
   security).   In particular, emergency call routing requires routing
   proxies to know location, and sips: protection is appropriate.  The
   latter case is under study by the SIPPING working group under the
   subject "End to Middle" security [12].


   Regardless which scenario (UA-to-UA or UA-to-Proxy) is used to
   convey location, SIP entities MUST adhere to the rules of [7],
   specifically the retention and distribution (privacy) attributes of
   a UA's location.  When Alice is deciding how to transmit her
   location, she should be keenly aware of the parameters in which she
   wants her location to be stored and distributed.  However, once she
   sends that location information to Bob, he MUST also now obey
   Alice's wishes regarding these privacy attributes if he is deciding
   to inform another party about Alice.  This is a fundamental
   principle of the Geopriv Working Group, i.e. "PRIVACY".



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8.  User Agent-to-User Agent Location Conveyance


   The offered solution here for the User-to-User solution for location
   conveyance between UAs is used with the INVITE, UPDATE, MESSAGE, and
   PUBLISH Methods in the following subsections.


8.1 UA-to-UA using INVITE Method


   Below is a common SIP session set-up sequence between two user
   agents.  In this example, Alice will provide Bob with her geographic
   location in the INVITE message.


   UA Alice                                  UA Bob


      |                INVITE [M1]              |
      |---------------------------------------->|
      |                                         |
      |                200 OK [M2]              |
      |<----------------------------------------|
      |                                         |
      |                  ACK [M3]               |
      |---------------------------------------->|
      |                                         |
      |                   RTP                   |
      |<=======================================>|
      |                                         |


      Figure 1. UA-UA with Location in INVITE


   User agent Alice invites user agent Bob to a session [M1 of Figure
   1].  Within this INVITE is a multipart body indication that it is
   S/MIME encrypted [according to the rules of 1] by Alice for Bob.
   One body part contains the SDP offered by Alice to Bob.  Alice's
   location (here coordinate based) is the other body part contained in
   this INVITE.  Bob responses with a 200 OK [M2] (choosing a codec as
   specified by the Offer/Answer Model [14]).  Bob can include his
   location in the 200 OK response, but this shouldn't be expected due
   to user timing.  If Bob wants to provide his location to Alice after
   the 200 OK, but before a BYE, the UPDATE Method [9] should be used.
   Alice's UA replies with an ACK and the session is set up.


   Figure 1. does not include any Proxies because in it assumed they
   would not affect the session set-up with respect to whether or not
   Alice's location is in a message body part, and Proxies don't react
   to S/MIME bodies, making their inclusion more or less moot and more
   complex than necessary.


   The most relevant message in Figure 1 having to do with location is
   (obviously) the message with the location object in it [M1].  So to
   cut down on length of this document, only the INVITE message in this



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   example will be shown. Section 8.1.1 will give an example of this
   well formed INVITE message using a Coordinate location format.
   Section 8.1.2 will give an example of this well formed INVITE
   message using the civic location format.



8.1.1 UA-to-UA INVITE with Coordinate Location Using S/MIME


   Below is a well-formed SIP INVITE Method message to the example in
   Figure 1 in section 8.1.


   [Message 1 in Figure 1]


   INVITE sips:bob@biloxi.example.com SIP/2.0
   Via: SIP/2.0/TLS pc33.atlanta.example.com
    ;branch=z9hG4bK776asdhds
   Max-Forwards: 70
   To: Bob <sips:bob@biloxi.example.com>
   From: Alice <sips:alice@atlanta.example.com>;tag=1928301774
   Call-ID: a84b4c76e66710@pc33.atlanta.example.com
   CSeq: 314159 INVITE
   Contact: <sips:alice@pc33.atlanta.example.com>
   Content-Type: application/pkcs7-mime;
      smime-type=enveloped-data; name=smime.p7m
   Content-Disposition: attachment;
      filename=smime.p7m  handling=required


   Content-Type: multipart/mixed; boundary=boundary1


   --boundary1


   Content-Type: application/sdp
   v=0
   o=alice 2890844526 2890844526 IN IP4 atlanta.example.com
   c=IN IP4 10.1.3.33
   t=0 0
   m=audio 49172 RTP/AVP 0 4 8
   a=rtpmap:0 PCMU/8000


   --boundary1


   Content-type: application/cpim-pidf+xml
   <?xml version="1.0" encoding="UTF-8"?>
       <presence xmlns="urn:ietf:params:xml:ns:pidf"
          xmlns:gp="urn:ietf:params:xml:ns:pidf:geopriv10"
          xmlns:gml="urn:opengis:specification:gml:schema-
                    xsd:feature:v3.0"
          entity="pres:alice@atlanta.example.com">
        <tuple id="sg89ae">
         <timestamp>2004-11-11T08:57:29Z</timestamp>
         <status>
          <gp:geopriv>



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            <gp:location-info>
              <gml:location>
                <gml:Point gml:id="point96" srsName="epsg:4326">
                  <gml:coordinates>41.87891N
                                   87.63649W</gml:coordinates>
                </gml:Point>
               </gml:location>
              <method>dhcp</method>
            </gp:location-info>
            <gp:usage-rules>
              <gp:retransmission-allowed>no</gp:retransmission-allowed>
              <gp:retention-expiry>2004-11-13T14:57:29Z</gp:retention-
                            expiry>
             </gp:usage-rules>
          </gp:geopriv>
         </status>
        </tuple>
       </presence>


   --boundary1--



8.1.1.1 UA-to-UA INVITE with Coordinate Location Not Using S/MIME


   Below is a well-formed SIP INVITE Method message to the example in
   Figure 1 in section 8.1.  This message is here to show that although
   the requirements are mandatory to implement proper security, it is
   not mandatory to use.  This message below is show for those cases
   where hop-by-hop security is deployed.


   [Message 1 in Figure 1]


   INVITE sip:bob@biloxi.example.com SIP/2.0
   Via: SIP/2.0/TCP pc33.atlanta.example.com
     ;branch=z9hG4bK74bf9
   Max-Forwards: 70
   From: Alice <sip:alice@atlanta.example.com>;tag=9fxced76sl
   To: Bob <sip:bob@biloxi.example.com>
   Call-ID: 3848276298220188511@atlanta.example.com
   CSeq: 31862 INVITE
   Contact: <sip:alice@atlanta.example.com>
   Content-Type: multipart/mixed; boundary=boundary1
   Content-Length: ...


   --boundary1


   Content-Type: application/sdp
   v=0
   o=alice 2890844526 2890844526 IN IP4 atlanta.example.com
   c=IN IP4 10.1.3.33
   t=0 0
   m=audio 49172 RTP/AVP 0 4 8



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   a=rtpmap:0 PCMU/8000


   --broundary1


   Content-Type: application/cpim-pidf+xml
   <?xml version="1.0" encoding="UTF-8"?>
       <presence xmlns="urn:ietf:params:xml:ns:pidf"
          xmlns:gp="urn:ietf:params:xml:ns:pidf:geopriv10"
          xmlns:gml="urn:opengis:specification:gml:schema-
          xsd:feature:v3.0"
          entity="pres:alice@atlanta.example.com">
        <tuple id="sg89ae">
         <timestamp>2004-11-11T08:57:29Z</timestamp>
         <status>
          <gp:geopriv>
            <gp:location-info>
              <gml:location>
                <gml:Point gml:id="point96" srsName="epsg:4326">
                  <gml:coordinates>41.87891N
                                   87.63649W</gml:coordinates>
                </gml:Point>
               </gml:location>
              <method>dhcp</method>
            </gp:location-info>
            <gp:usage-rules>
              <gp:retransmission-allowed>no</gp:retransmission-allowed>
              <gp:retention-expiry>2004-11-13T14:57:29Z</gp:retention-
                     expiry>
            </gp:usage-rules>
          </gp:geopriv>
         </status>
        </tuple>
       </presence>


   --boundary1--



8.1.2 UA-to-UA INVITE with Civic Location Using S/MIME


   Below is a well-formed SIP INVITE Method message to the example in
   Figure 1 in section 8.1 using the civic location format.



   [Message 1 in Figure 1]


   INVITE sips:bob@biloxi.example.com SIP/2.0
   Via: SIP/2.0/TLS pc33.atlanta.example.com
    ;branch=z9hG4bK776asdhds
   Max-Forwards: 70
   To: Bob <sips:bob@biloxi.example.com>
   From: Alice <sips:alice@atlanta.example.com>;tag=1928301774
   Call-ID: a84b4c76e66710@pc33.atlanta.example.com



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   CSeq: 314159 INVITE
   Contact: <sips:alice@pc33.atlanta.example.com>
   Content-Type: application/pkcs7-mime;
      smime-type=enveloped-data; name=smime.p7m
   Content-Disposition: attachment;
      filename=smime.p7m  handling=required


   Content-Type: multipart/mixed; boundary=boundary1


   --boundary1


   Content-Type: application/sdp
   v=0
   o=alice 2890844526 2890844526 IN IP4 atlanta.example.com
   c=IN IP4 10.1.3.33
   t=0 0
   m=audio 49172 RTP/AVP 0 4 8
   a=rtpmap:0 PCMU/8000


   --boundary1


   Content-type: application/cpim-pidf+xml
   <?xml version="1.0" encoding="UTF-8"?>
      <presence xmlns="urn:ietf:params:xml:ns:pidf"
          xmlns:gp="urn:ietf:params:xml:ns:pidf:geopriv10"
          xmlns:gml="urn:opengis:specification:gml:schema-
                     xsd:feature:v3.0"
          entity="pres:alice@atlanta.example.com">
        <tuple id="sg89ae">
         <timestamp>2004-11-11T08:57:29Z</timestamp>
         <status>
          <gp:geopriv>
            <gp:location-info>
              <cl:civilAddress>
                <cl:country>US</cl:country>
                <cl:A1>Illinois</cl:A1>
                <cl:A3>Chicago</cl:A3>
                <cl:HNO>233</cl:HNO>
                <cl:PRD>South</cl:PRD>
                <cl:A6>Wacker</cl:A6>
                <cl:STS>Drive</cl:STS>
                <cl:PC>60606</cl:PC>
                <cl:LMK>Sears Tower</cl:LMK>
                <cl:FLR>1</cl:FLR>
              <cl:civilAddress>
              <method>dhcp</method>
              <provided-by><nena>www.cisco.com</nena></provided-by/>
            </gp:location-info>
            <gp:usage-rules>
              <gp:retransmission-allowed>no</gp:retransmission-allowed>
              <gp:retention-expiry>2004-11-13T14:57:29Z</gp:retention-
                            expiry>



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            </gp:usage-rules>
          </gp:geopriv>
         </status>
        </tuple>
       </presence>


--boundary1--



8.1.2.1 UA-to-UA INVITE with Civic Location Not Using S/MIME


   Below is a well-formed SIP INVITE Method message to the example in
   Figure 1 in section 8.1.  This message is here to show that although
   the requirements are mandatory to implement proper security, it is
   not mandatory to use.  This message below is show for those cases
   where the sending user does not wish to use security mechanisms in
   transmitting their coordinate location.



   [Message 1 in Figure 1]


   INVITE sip:bob@biloxi.example.com SIP/2.0
   Via: SIP/2.0/TCP pc33.atlanta.example.com
     ;branch=z9hG4bK74bf9
   Max-Forwards: 70
   From: Alice <sip:alice@atlanta.example.com>;tag=9fxced76sl
   To: Bob <sip:bob@biloxi.example.com>
   Call-ID: 3848276298220188511@atlanta.example.com
   CSeq: 31862 INVITE
   Contact: <sip:alice@atlanta.example.com>
   Content-Type: multipart/mixed; boundary=boundary1
   Content-Length: ...


   --boundary1


   Content-Type: application/sdp
   v=0
   o=alice 2890844526 2890844526 IN IP4 atlanta.example.com
   c=IN IP4 10.1.3.33
   t=0 0
   m=audio 49172 RTP/AVP 0 4 8
   a=rtpmap:0 PCMU/8000


   --broundary1


   Content-type: application/cpim-pidf+xml
   <?xml version="1.0" encoding="UTF-8"?>
      <presence xmlns="urn:ietf:params:xml:ns:pidf"
          xmlns:gp="urn:ietf:params:xml:ns:pidf:geopriv10"
          xmlns:gml="urn:opengis:specification:gml:schema-
                     xsd:feature:v3.0"
          entity="pres:alice@atlanta.example.com">



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        <tuple id="sg89ae">
         <timestamp>2004-11-11T08:57:29Z</timestamp>
         <status>
          <gp:geopriv>
            <gp:location-info>
              <cl:civilAddress>
                <cl:country>US</cl:country>
                <cl:A1>Illinois</cl:A1>
                <cl:A3>Chicago</cl:A3>
                <cl:HNO>233</cl:HNO>
                <cl:PRD>South</cl:PRD>
                <cl:A6>Wacker</cl:A6>
                <cl:STS>Drive</cl:STS>
                <cl:PC>60606</cl:PC>
                <cl:LMK>Sears Tower</cl:LMK>
                <cl:FLR>1</cl:FLR>
              <cl:civilAddress>
              <method>dhcp</method>
              <provided-by><nena>www.cisco.com</nena></provided-by/>
            </gp:location-info>
            <gp:usage-rules>
              <gp:retransmission-allowed>no</gp:retransmission-allowed>
              <gp:retention-expiry>2004-11-13T14:57:29Z</gp:retention-
                            expiry>
            </gp:usage-rules>
          </gp:geopriv>
         </status>
        </tuple>
       </presence>


--boundary1--



8.1.3 UA-to-UA Location Conveyance Involving 3 Users


   In the following example, Alice presents her location in the INVITE
   to Bob, which Bob 200 OKs with his location as well.  Bob then
   directs Alice to contact Carol.  The REFER Method [15] is used in
   the message sequence, but it does not carry anyone's location within
   the REFER message.  This example is here to show a 3-way
   communication of location, coupled with how a UA can include someone
   else's location.  This has security implications due to neither
   primary party in the last location transfer being the owner of the
   location information.  Alice (in this case) MUST adhere to the
   retention and distribution privacy requirements within Bob's
   location object regarding his location information prior to
   considering its inclusion in the INVITE to Carol.


   UA Alice                        Bob          Carol


      |           INVITE [M1]       |             |
      |---------------------------->|             |



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      |           200 OK [M2]       |             |
      |<----------------------------|             |
      |            ACK [M3]         |             |
      |---------------------------->|             |
      |              RTP            |             |
      |<===========================>|             |
      |     reINVITE (hold) [M4]    |             |
      |<----------------------------|             |
      |          200 OK [M5]        |             |
      |---------------------------->|             |
      | REFER (Refer-to:Carol) [M6] |             |
      |<----------------------------|             |
      |                 INVITE [M7]               |
      |------------------------------------------>|
      |                 200 OK [M8]               |
      |------------------------------------------>|
      |                     RTP                   |
      |<=========================================>|
      |          NOTIFY [M9]        |             |
      |---------------------------->|             |
      |          200 OK [M10]       |             |
      |<----------------------------|             |
      |           BYE [M11]         |             |
      |<----------------------------|             |
      |          200 OK [M12]       |             |
      |---------------------------->|             |
      |                                           |


      Figure 1a. UA-to-UA with Location in REFER



8.1.3.1 UA-to-UA REFER with Civic Location Using S/MIME


   In Figure 1a., we have an example message flow involving the REFER
   Method.  The REFER itself does not carry location objects.


   We are not including all the messages for space reasons.  M1 is a
   well-formed SIP message that contains Alice's location.  M2 is Bob's
   200 OK in response to Alice's INVITE, and it contains Bob's
   Location.


[M1 of Figure 1a] - Alice at Sears Tower


   INVITE sips:bob@biloxi.example.com SIP/2.0
   Via: SIP/2.0/TLS pc33.atlanta.example.com
    ;branch=z9hG4bK776asdhds
   Max-Forwards: 70
   To: Bob <sips:bob@biloxi.example.com>
   From: Alice <sips:alice@atlanta.example.com>;tag=1928301774
   Call-ID: a84b4c76e66710@pc33.atlanta.example.com
   CSeq: 314159 INVITE
   Contact: <sips:alice@pc33.atlanta.example.com>



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   Content-Type: application/pkcs7-mime;
      smime-type=enveloped-data; name=smime.p7m
   Content-Disposition: attachment;
      filename=smime.p7m  handling=required


   Content-Type: multipart/mixed; boundary=boundary1


   --boundary1


   Content-Type: application/sdp
   v=0
   o=alice 2890844526 2890844526 IN IP4 atlanta.example.com
   c=IN IP4 10.1.3.33
   t=0 0
   m=audio 49172 RTP/AVP 0 4 8
   a=rtpmap:0 PCMU/8000


   --boundary1


   Content-type: application/cpim-pidf+xml
   <?xml version="1.0" encoding="UTF-8"?>
      <presence xmlns="urn:ietf:params:xml:ns:pidf"
          xmlns:gp="urn:ietf:params:xml:ns:pidf:geopriv10"
          xmlns:gml="urn:opengis:specification:gml:schema-
                     xsd:feature:v3.0"
          entity="pres:alice@atlanta.example.com">
        <tuple id="sg89ae">
         <timestamp>2004-11-11T08:57:29Z</timestamp>
         <status>
          <gp:geopriv>
            <gp:location-info>
              <cl:civilAddress>
                <cl:country>US</cl:country>
                <cl:A1>Illinois</cl:A1>
                <cl:A3>Chicago</cl:A3>
                <cl:HNO>233</cl:HNO>
                <cl:PRD>South</cl:PRD>
                <cl:A6>Wacker</cl:A6>
                <cl:STS>Drive</cl:STS>
                <cl:PC>60606</cl:PC>
                <cl:LMK>Sears Tower</cl:LMK>
                <cl:FLR>1</cl:FLR>
              <cl:civilAddress>
              <method>dhcp</method>
              <provided-by><nena>www.cisco.com</nena></provided-by/>
            </gp:location-info>
            <gp:usage-rules>
              <gp:retransmission-allowed>no</gp:retransmission-allowed>
              <gp:retention-expiry>2004-11-13T14:57:29Z</gp:retention-
                            expiry>
            </gp:usage-rules>
          </gp:geopriv>



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         </status>
        </tuple>
       </presence>


   --boundary1--



   Bob replies to Alice's INVITE with a 200 OK and includes his
   location.


[M2 of Figure 4] - Bob watching Cubs Game at Wrigley Field


   SIP/2.0 200 OK
   Via: SIP/2.0/TCP pc33.atlanta.example.com
     ;branch=z9hG4bKnashds8 ;received=10.1.3.33
   To: Bob <sip:bob@biloxi.com>;tag=a6c85cf
   From: Alice <sip:alice@atlanta.example.com>;tag=1928301774
   Call-ID: a84b4c76e66710
   CSeq: 314159 INVITE
   Contact: <sip:bob@192.168.10.20>
   Content-Type: application/pkcs7-mime;
      smime-type=enveloped-data; name=smime.p7m
   Content-Disposition: attachment;
      filename=smime.p7m  handling=required


   Content-Type: multipart/mixed; boundary=boundary1


   --boundary1


   Content-Type: application/sdp
   v=0
   o=bob 2890844530 2890844530 IN IP4 biloxi.example.com
   c=IN IP4 192.168.10.20
   t=0 0
   m=audio 3456 RTP/AVP 0
   a=rtpmap:0 PCMU/8000


   --boundary1


   Content-type: application/cpim-pidf+xml
   <?xml version="1.0" encoding="UTF-8"?>
      <presence xmlns="urn:ietf:params:xml:ns:pidf"
          xmlns:gp="urn:ietf:params:xml:ns:pidf:geopriv10"
          xmlns:gml="urn:opengis:specification:gml:schema-
                     xsd:feature:v3.0"
          entity="pres:bob@biloxi.example.com">
        <tuple id="sg89ae">
         <timestamp>2004-11-6T02:30:29Z</timestamp>
         <status>
          <gp:geopriv>
            <gp:location-info>
              <cl:civilAddress>



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                <cl:country>US</cl:country>
                <cl:A1>Illinois</cl:A1>
                <cl:A3>Chicago</cl:A3>
                <cl:A6>Addison</cl:A6>
                <cl:HNO>1060</cl:HNO>
                <cl:PRD>W</cl:PRD>
                <cl:STS>street</cl:STS>
                <cl:LMK>Wrigley Field</cl:LMK>
                <cl:PC>60613</cl:PC>
              <cl:civilAddress>
              <method>dhcp</method>
              <provided-by>www.cisco.com</provided-by/>
            </gp:location-info>
            <gp:usage-rules>
              <gp:retransmission-allowed>no</gp:retransmission-allowed>
              <gp:retention-expiry>2004-11-6T18:30:29Z</gp:retention-
                            expiry>
            </gp:usage-rules>
          </gp:geopriv>
         </status>
        </tuple>
       </presence>


   --boundary1--


   Bob REFERs Alice to Carol, and in M7, Alice includes both locations
   in a single SIP message.  This is possible because Bob set his
   retention value to "yes", thus allowing Alice to pass his location
   on to Carol.


[M7 of Figure 1a] - Alice tells Carol where she and Bob are


   INVITE sips:carol@chicago.example.com SIP/2.0
   Via: SIP/2.0/TLS pc33.atlanta.example.com
    ;branch=z9hG4bK776asdhdt
   Max-Forwards: 70
   To: Carol <sips:carol@chicago.example.com>
   From: Alice <sips:alice@atlanta.example.com>;tag=1928301775
   Call-ID: a84b4c76e66711@pc33.atlanta.example.com
   CSeq: 314160 INVITE
   Contact: <sips:alice@pc33.atlanta.example.com>
   Content-Type: application/pkcs7-mime;
      smime-type=enveloped-data; name=smime.p7m
   Content-Disposition: attachment;
      filename=smime.p7m  handling=required


   Content-Type: multipart/mixed; boundary=boundary1


   --boundary1


   Content-Type: application/sdp
   v=0



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   o=alice 2890844531 2890844531 IN IP4 atlanta.example.com
   c=IN IP4 10.1.3.33
   t=0 0
   m=audio 49173 RTP/AVP 0 4 8
   a=rtpmap:0 PCMU/8000


   --boundary1


   Content-type: application/cpim-pidf+xml
   <?xml version="1.0" encoding="UTF-8"?>
      <presence xmlns="urn:ietf:params:xml:ns:pidf"
          xmlns:gp="urn:ietf:params:xml:ns:pidf:geopriv10"
          xmlns:gml="urn:opengis:specification:gml:schema-
                     xsd:feature:v3.0"
          entity="pres:bob@biloxi.example.com">
        <tuple id="sg89af">
         <timestamp>2004-11-5T02:30:29Z</timestamp>
         <status>
          <gp:geopriv>
            <gp:location-info>
              <cl:civilAddress>
                <cl:country>US</cl:country>
                <cl:A1>Illinois</cl:A1>
                <cl:A3>Chicago</cl:A3>
                <cl:A6>Addison</cl:A6>
                <cl:HNO>1060</cl:HNO>
                <cl:PRD>W</cl:PRD>
                <cl:STS>street</cl:STS>
                <cl:LMK>Wrigley Field</cl:LMK>
                <cl:PC>60613</cl:PC>
              <cl:civilAddress>
              <method>dhcp</method>
              <method>802.11</method>
              <provided-by>www.cisco.com</provided-by/>
            </gp:location-info>
            <gp:usage-rules>
              <gp:retransmission-allowed>yes</gp:retransmission-
                                                             allowed>
              <gp:retention-expiry>2004-11-6T18:30:29Z</gp:retention-
                            expiry>
            </gp:usage-rules>
          </gp:geopriv>
         </status>
        </tuple>
       </presence>


   --boundary1


   Content-type: application/cpim-pidf+xml
   <?xml version="1.0" encoding="UTF-8"?>
      <presence xmlns="urn:ietf:params:xml:ns:pidf"
          xmlns:gp="urn:ietf:params:xml:ns:pidf:geopriv10"



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          xmlns:gml="urn:opengis:specification:gml:schema-
                     xsd:feature:v3.0"
          entity="pres:alice@atlanta.example.com">
        <tuple id="sg89ae">
         <timestamp>2004-11-6T02:30:29Z</timestamp>
         <status>
          <gp:geopriv>
            <gp:location-info>
              <cl:civilAddress>
                <cl:country>US</cl:country>
                <cl:A1>Illinois</cl:A1>
                <cl:A3>Chicago</cl:A3>
                <cl:HNO>233</cl:HNO>
                <cl:PRD>South</cl:PRD>
                <cl:A6>Wacker</cl:A6>
                <cl:STS>Drive</cl:STS>
                <cl:PC>60606</cl:PC>
                <cl:LMK>Sears Tower</cl:LMK>
                <cl:FLR>1</cl:FLR>
              <cl:civilAddress>
              <method>dhcp</method>
              <method>802.11</method>
              <provided-by>www.marconi.com</provided-by/>
            </gp:location-info>
            <gp:usage-rules>
              <gp:retransmission-allowed>no</gp:retransmission-allowed>
              <gp:retention-expiry>2004-11-6T18:30:29Z</gp:retention-
                            expiry>
            </gp:usage-rules>
          </gp:geopriv>
         </status>
        </tuple>
       </presence>


   --boundary1--



   It is an open question of whether there should be a mechanism to
   request or require the transmission of an LO.  The LO is contained
   in a body, so the available sip mechanisms do not apply.



8.2 UA-to-UA Using MESSAGE Method


   Anytime a user transmits location information outside a dialog, the
   MESSAGE Method is to be used.  The logic here is as follows:


      - UPDATE isn't appropriate because it is for the updating of
        session capabilities and parameters of a dialog (after the
        INVITE included location information).


      - reINVITE isn't appropriate because it is only used (or only



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        supposed to be used) for changing the parameters of an existing
        dialog, and one might not exist in all cases of location
        conveyance.


   This leaves MESSAGE as the only viable Request Method for location
   conveyance outside of a dialog between two users (Alice and Bob in
   this case). The following is an example of this communication.



   UA Alice                                  UA Bob


      |               MESSAGE [M1]              |
      |---------------------------------------->|
      |                                         |
      |                200 OK [M2]              |
      |<----------------------------------------|
      |                                         |


      Figure 2. UA-UA with Location in MESSAGE


   Section 8.2.1 will give the well formed MESSAGE Method containing a
   well formed Geopriv Location Object using the Coordinate location
   format that fully complies with all security requirements - SIPS for
   hop-by-hop security, and S/MIME for message body confidentiality
   end-to-end, as well as adhering to the retention and distribution
   concerns from [7].  Section 8.2.2 will show the Civic Location
   format alternative to the same location, as conveyed from Alice to
   Bob.  This section does not adhere to confidentiality or integrity
   concerns of [7], but does convey retention and distribution
   indicators from Alice.



8.2.1 UA-to-UA MESSAGE with Coordinate Location Using S/MIME


   Below is M1 from Figure 2 in section 8.2. that is fully secure and
   in compliance with Geopriv requirements in [7] for security
   concerns.



   [Message 1 in Figure 2]


   MESSAGE sips:bob@biloxi.example.com SIP/2.0
   Via: SIP/2.0/TLS pc33.atlanta.example.com
    ;branch=z9hG4bK776asegma
   Max-Forwards: 70
   To: Bob <sips:bob@biloxi.example.com>
   From: Alice <sips:alice@atlanta.example.com>;tag=1928301774
   Call-ID: a84b4c76e66710@pc33.atlanta.example.com
   CSeq: 22756 MESSAGE
   Content-Type: application/pkcs7-mime;
      smime-type=enveloped-data; name=smime.p7m
   Content-Disposition: attachment;



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      filename=smime.p7m  handling=required

   Content-Type: multipart/mixed; boundary=boundary1


   --boundary1


   Content-Type: text/plain
   Here's my location, Bob?


   --broundary1


   Content-Type: application/cpim-pidf+xml
   Content-Disposition: render
   Content-Description: my location
   <?xml version="1.0" encoding="UTF-8"?>
       <presence xmlns="urn:ietf:params:xml:ns:pidf"
          xmlns:gp="urn:ietf:params:xml:ns:pidf:geopriv10"
          xmlns:gml="urn:opengis:specification:gml:schema-
          xsd:feature:v3.0"
          entity="pres:alice@atlanta.example.com">
        <tuple id="sg89ae">
         <timestamp>2004-11-11T08:57:29Z</timestamp>
         <status>
          <gp:geopriv>
            <gp:location-info>
              <gml:location>
                <gml:Point gml:id="point96" srsName="epsg:4326">
                  <gml:coordinates>41.87891N
                                   87.63649W</gml:coordinates>
                </gml:Point>
               </gml:location>
              <method>dhcp</method>
            </gp:location-info>
            <gp:usage-rules>
              <gp:retransmission-allowed>no</gp:retransmission-allowed>
              <gp:retention-expiry>2004-11-13T14:57:29Z</gp:retention-
                     expiry>
            </gp:usage-rules>
          </gp:geopriv>
         </status>
        </tuple>
       </presence>


   --boundary1--



8.2.2 UA-to-UA MESSAGE with Civic Location Not Using S/MIME


   Below is a well-formed SIP MESSAGE Method message to the example in
   Figure 2 in section 8.2 when hop-by-hop security mechanisms are
   deployed.




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   [Message 1 in Figure 2]


   MESSAGE sip:bob@biloxi.example.com SIP/2.0
   From: <sip:alice@atlanta.example.com>;tag=34589882
   To: <sip:bob@biloxi.example.com>
   Call-ID: 9242892442211117@atlanta.example.com
   CSeq: 6187 MESSAGE
   Content-Type: application/cpim-pidf+xml
   Content-ID: <766534765937@atlanta.example.com>
   Content-Disposition: render
   Content-Description: my location


   <?xml version="1.0" encoding="UTF-8"?>
      <presence xmlns="urn:ietf:params:xml:ns:pidf"
          xmlns:gp="urn:ietf:params:xml:ns:pidf:geopriv10"
          xmlns:gml="urn:opengis:specification:gml:schema-
          xsd:feature:v3.0"
          entity="pres:alice@atlanta.example.com">
        <tuple id="sg89ae">
         <timestamp>2004-11-11T08:57:29Z</timestamp>
         <status>
          <gp:geopriv>
            <gp:location-info>
              <cl:civilAddress>
                <cl:country>US</cl:country>
                <cl:A1>Illinois</cl:A1>
                <cl:A3>Chicago</cl:A3>
                <cl:HNO>233</cl:HNO>
                <cl:PRD>South</cl:PRD>
                <cl:A6>Wacker</cl:A6>
                <cl:STS>Drive</cl:STS>
                <cl:PC>60606</cl:PC>
                <cl:LMK>Sears Tower</cl:LMK>
                <cl:FLR>1</cl:FLR>
              <cl:civilAddress>
              <method>dhcp</method>
            </gp:location-info>
            <gp:usage-rules>
              <gp:retransmission-allowed>no</gp:retransmission-allowed>
              <gp:retention-expiry>2004-11-13T14:57:29Z</gp:retention-
                      expiry>
            </gp:usage-rules>
          </gp:geopriv>
         </status>
        </tuple>
       </presence>



8.3 UA-to-UA Location Conveyance Using UPDATE


   UPDATE MUST NOT be used to send location information from UA-to-UA



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   unless location has already been sent in an INVITE or corresponding
   200 OK that was the first message exchange in the same dialog set-
   up.  The same security properties used in the INVITE MUST be used in
   the UPDATE message.


   The UPDATE Method is to be used any time location information is to
   be updated between UAs setting up a dialog or after the dialog has
   been established, no matter how long that dialog has been
   operational.  reINVITE is out of scope here, and the MESSAGE Method
   is for non-dialog location conveyance between UAs only.


   One reason for this message being generated is if either UA that
   sent its location information to the other UA (say in the INVITE and
   corresponding 200 OK) is if either UA determines that is has moved
   while the dialog has remained operational.  How this movement is
   determined is outside the scope of this document, but ultimately
   should be configurable by local administration or the user of the
   UA.  By how much Alice has moved to trigger the "sense of movement"
   (i.e. the need to send new location) to Bob is also outside the
   scope of this specification, but ultimately should be configurable
   by local administration or the user of the UA.


   In Figure 3., we have an example message flow involving the UPDATE
   Method. We are not including all the messages for space reasons.  M1
   is a well formed SIP message that contains Alice's location. During
   the session set-up, Alice's UA knows it has moved while knowing too
   the session has not been formally accepted by Bob.  Alice's UA
   decides to update Bob with her new location with an UPDATE Method
   message.   Messages M2, M3 and M4 have nothing to do with location
   conveyance, therefore will not be shown in detail.  Only M1 and M5
   will be shown.


   NOTE: A similar use for UPDATE is within the UA-to-Proxy Location
         Conveyance section of this document.



   UA Alice                                  UA Bob


      |                INVITE [M1]              |
      |---------------------------------------->|
      |                                         |
      |        183 (session Progress) [M2]      |
      |<----------------------------------------|
      |                                         |
      |                 PRACK [M3]              |
      |---------------------------------------->|
      |                                         |
      |              ACK (PRACK) [M4]           |
      |<----------------------------------------|
      |                                         |
      |                 UPDATE [M5]             |
      |---------------------------------------->|



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      |                                         |
      |              ACK (UPDATE) [M6]          |
      |<----------------------------------------|
      |                                         |
      |            200 OK (INVITE) [M7]         |
      |<----------------------------------------|
      |                                         |
      |                   RTP                   |
      |<=======================================>|
      |                                         |


      Figure 3. UA-UA with Location in UPDATE



   The following section will include the M1 and M5 messages in detail,
   but only in the civic format.



8.3.1 UA-to-UA UPDATE with Civic Location Not Using S/MIME


   Here is the initial INVITE from Alice to Bob.


  [M1 INVITE to Bob]


   INVITE sips:bob@biloxi.example.com SIP/2.0
   Via: SIP/2.0/TLS pc33.atlanta.example.com
    ;branch=z9hG4bK776asdhds
   Max-Forwards: 70
   To: Bob <sips:bob@biloxi.example.com>
   From: Alice <sips:alice@atlanta.example.com>;tag=1928301774
   Call-ID: a84b4c76e66710@pc33.atlanta.example.com
   CSeq: 314159 INVITE
   Contact: <sips:alice@pc33.atlanta.example.com>
   Content-Type: application/pkcs7-mime;
      smime-type=enveloped-data; name=smime.p7m
   Content-Disposition: attachment;
      filename=smime.p7m  handling=required


   Content-Type: multipart/mixed; boundary=boundary1


   --boundary1


   Content-Type: application/sdp
   v=0
   o=alice 2890844526 2890844526 IN IP4 atlanta.example.com
   c=IN IP4 10.1.3.33
   t=0 0
   m=audio 49172 RTP/AVP 0 4 8
   a=rtpmap:0 PCMU/8000


   --boundary1




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   Content-type: application/cpim-pidf+xml
   <?xml version="1.0" encoding="UTF-8"?>
      <presence xmlns="urn:ietf:params:xml:ns:pidf"
          xmlns:gp="urn:ietf:params:xml:ns:pidf:geopriv10"
          xmlns:gml="urn:opengis:specification:gml:schema-
                     xsd:feature:v3.0"
          entity="pres:alice@atlanta.example.com">
        <tuple id="sg89ae">
         <timestamp>2004-11-11T08:57:29Z</timestamp>
         <status>
          <gp:geopriv>
            <gp:location-info>
              <cl:civilAddress>
                <cl:country>US</cl:country>
                <cl:A1>Illinois</cl:A1>
                <cl:A3>Chicago</cl:A3>
                <cl:HNO>233</cl:HNO>
                <cl:PRD>South</cl:PRD>
                <cl:A6>Wacker</cl:A6>
                <cl:STS>Drive</cl:STS>
                <cl:PC>60606</cl:PC>
                <cl:LMK>Sears Tower</cl:LMK>
                <cl:FLR>1</cl:FLR>
              <cl:civilAddress>
              <method>dhcp</method>
              <method>802.11</method>
             <provided-by>www.cisco.com</provided-by/>
            </gp:location-info>
            <gp:usage-rules>
              <gp:retransmission-allowed>no</gp:retransmission-allowed>
              <gp:retention-expiry>2004-11-13T14:57:29Z</gp:retention-
                            expiry>
            </gp:usage-rules>
          </gp:geopriv>
         </status>
        </tuple>
       </presence>


--boundary1--


   Alice moves locations (with her UA detecting the movement), causing
   her UA to generate an UPDATE message ([M5] of Figure 3) prior to
   her UA receiving a final response from Bob.  Here is that message:


  M5 UPDATE to Bob


   UPDATE sips:bob@biloxi.example.com/TCP SIP/2.0
   Via: SIP/2.0/TLS pc33.atlanta.example.com
    ;branch=z9hG4bK776asdhds
   Max-Forwards: 70
   To: Bob <sips:bob@biloxi.example.com>
   From: Alice <sips:alice@atlanta.example.com>;tag=1928



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   Call-ID: a84b4c76e66710@pc33.atlanta.example.com
   CSeq: 10197 UPDATE
   Contact: <sips:alice@pc33.atlanta.example.com>
   Content-Type: application/pkcs7-mime;
      smime-type=enveloped-data; name=smime.p7m
   Content-Disposition: attachment;
      filename=smime.p7m  handling=required


   Content-Type: multipart/mixed; boundary=boundary1


   --boundary1


   Content-Type: application/sdp
   v=0
   o=alice 2890844526 2890844526 IN IP4 atlanta.example.com
   c=IN IP4 10.1.3.33
   t=0 0
   m=audio 49172 RTP/AVP 0 4 8
   a=rtpmap:0 PCMU/8000


   --boundary1


   Content-type: application/cpim-pidf+xml
   <?xml version="1.0" encoding="UTF-8"?>
      <presence xmlns="urn:ietf:params:xml:ns:pidf"
          xmlns:gp="urn:ietf:params:xml:ns:pidf:geopriv10"
          xmlns:gml="urn:opengis:specification:gml:schema-
                     xsd:feature:v3.0"
          entity="pres:alice@atlanta.example.com">
        <tuple id="sg89ae">
         <timestamp>2004-11-11T08:57:29Z</timestamp>
         <status>
          <gp:geopriv>
            <gp:location-info>
              <cl:civilAddress>
                <cl:country>US</cl:country>
                <cl:A1>Illinois</cl:A1>
                <cl:A3>Chicago</cl:A3>
                <cl:HNO>250</cl:HNO>
                <cl:PRD>South Upper</cl:PRD>
                <cl:A6>Wacker</cl:A6>
                <cl:STS>Drive</cl:STS>
                <cl:PC>60606</cl:PC>
                <cl:NAM>Venice Cafe</cl:NAM>
                <cl:FLR>1</cl:FLR>
              <cl:civilAddress>
              <method>dhcp</method>
              <method>802.11</method>
              <provided-by>www.t-mobile.com</provided-by/>
            </gp:location-info>
            <gp:usage-rules>
              <gp:retransmission-allowed>no</gp:retransmission-allowed>



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              <gp:retention-expiry>2004-11-13T14:57:29Z</gp:retention-
                            expiry>
            </gp:usage-rules>
          </gp:geopriv>
         </status>
        </tuple>
       </presence>


--boundary1--



8.4 UA-to-UA Location Conveyance Using PUBLISH


   ** This section could not be completed before submission time and
   will be completed shortly after IETF61. A thousand and one pardons.



8.5 UA-to-UA Location Conveyance Using SUBSCRIBE and NOTIFY


   This section was not completed in time for the ID cut-off, thus all
   text was removed until it can be completed.  The authors apologize.



8.6 424 "Bad Location Information" Error Response


   In the case that a user agent server or SIP Proxy detects an error
   in a message containing location information specific to that
   message body, a new 4XX level error needs to be sent.  This document
   creates the new error code:


      424 (Bad Location Information)


   This will provide the UAC with directed feedback about the status of
   location information it sent to that UAS or Proxy.  The UAC MAY
   attempt to retry sending the message providing its location.


   This new error code will be IANA registered.


   An example flow of this scenario will be included in the next
   version of this internet draft.



9.  Special Considerations for Emergency Calls


   When a Proxy Server knows to look for a location message body to
   route an emergency call as in [11].


   Emergency calls, which might be detected as detailed in [3], have
   special rules for conveyance of location:


   1. An emergency call MUST have all LI available to the UA, if any,
      sent with the INVITE, and subsequent UPDATE or reINVITE messages



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      as a PIDF-LO in a body


   2. The LO must be protected with sips: unless the attempt to
      establish hop-by-hop TLS connection fails and cannot reasonably
      be established in a very short (less than a second) time.  In
      such a case, the LO SHOULD be sent without TLS ONLY for those
      hops that failed to support TLS establishment.


   3. User Agents MUST NOT use S/MIME


   4. User Agents MUST include the <provided-by> element in the PIDF-LO
      (if known) to give the ERC an indication as to who is responsible
      for providing the UA with its location information.


   Proxies MUST NOT remove a location message body at any time.  In the
   case where the Proxy knows the location of the UAC and does not
   detect the UAC's location information message body in the message
   (or determines the LO is bad), the Proxy generates a new 4XX (Retry
   Location Body) error message that includes a location information
   message body for that UAC to include in the subsequent message.  The
   user agent MUST include this message body in the subsequent
   emergency message.


   In the <provided-by> element of the PIDF-LO, the Proxy MUST identify
   itself as the source of this location information.  The user agent
   MUST NOT alter this field's value if received from a Proxy server.


   If the UAS of the ERC receives a SIP request with multiple location
   objects, it must determine which to use, since more than one may be
   present.  This specification does not limit the number of LOs in a
   message, even in session mode.



9.1 UA-to-Proxy Routing the Message with INVITE (secure)


   When Alice signifies "sos@" [per 3], her UA must understand this
   message MUST NOT use S/MIME for the message body, because this is an
   emergency call - otherwise the message will not properly route to
   the correct destination.  Two definite possibilities will exist for
   how this message flow will occur [note: the message flows are not
   being defined here, they are defined in [11], but two are shown here
   to show the messages themselves].  The first possibility has Alice
   sending her INVITE to her first hop Proxy, which recognizes the
   message as an emergency message.  The Proxy knows to look into the
   message bodies for the location body; determine where Alice is and
   route the call to the appropriate ERC.  This is shown in Figure 4A.


   UA Alice             Proxy                  ERC


      |    INVITE [M1]    |                     |
      |------------------>|                     |



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      |                   |      INVITE [M2]    |
      |                   |-------------------->|
      |                   |      200 OK [M3]    |
      |                   |<--------------------|
      |   200 OK [M4]     |                     |
      |<------------------|                     |
      |     ACK [M5]                            |
      |---------------------------------------->|
      |                   RTP                   |
      |<=======================================>|
      |                                         |


      Figure 4A. UA-PROXY with Location in INVITE


   [M1 of  Figure 4A]


   INVITE sips:sos@atlanta.example.com SIP/2.0
   Via: SIP/2.0/TLS pc33.atlanta.example.com
     ;branch=z9hG4bK74bf9
   Max-Forwards: 70
   From: Alice <sips:alice@atlanta.example.com>;tag=9fxced76sl
   To: <sips:sos@atlanta.example.com>
   Call-ID: 3848276298220188511@atlanta.example.com
   CSeq: 31862 INVITE
   Contact: <sips:alice@atlanta.example.com>
   Content-Type: multipart/mixed; boundary=boundary1
   Content-Length: ...


   --boundary1


   Content-Type: application/sdp
   v=0
   o=alice 2890844526 2890844526 IN IP4 atlanta.example.com
   c=IN IP4 10.1.3.33
   t=0 0
   m=audio 49172 RTP/AVP 0 4 8
   a=rtpmap:0 PCMU/8000


   --boundary1




   Once the Proxy receives M1 and recognizes it as an emergency INVITE
   Request, this proxy knows to look into the message body for a
   location body part to determine the location of the UAC in order to
   match the location to an ERC.  Once this look-up occurs, the message
   is sent directly to the ERC (in message [M2]).


   [M2 of Figure 4A] - Proxy has determined when to send message


   INVITE sips:sos@192.168.10.20 SIP/2.0
   Via: SIP/2.0/TLS pc33.atlanta.example.com



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     ;branch=z9hG4bK74bf9
   Max-Forwards: 69
   From: Alice <sips:alice@atlanta.example.com>;tag=9fxced76sl
   To: <sips:sos@atlanta.example.com>
   Call-ID: 3848276298220188511@atlanta.example.com
   CSeq: 31862 INVITE
   Contact: <sips:alice@atlanta.example.com>
   Content-Type: multipart/mixed; boundary=boundary1
   Content-Length: ...


   --boundary1


   Content-Type: application/sdp
   v=0
   o=alice 2890844526 2890844526 IN IP4 atlanta.example.com
   c=IN IP4 10.1.3.33
   t=0 0
   m=audio 49172 RTP/AVP 0 4 8
   a=rtpmap:0 PCMU/8000


   --boundary1


   Content-type: application/cpim-pidf+xml
   <?xml version="1.0" encoding="UTF-8"?>
      <presence xmlns="urn:ietf:params:xml:ns:pidf"
          xmlns:gp="urn:ietf:params:xml:ns:pidf:geopriv10"
          xmlns:gml="urn:opengis:specification:gml:schema-
                     xsd:feature:v3.0"
          entity="pres:alice@atlanta.example.com">
        <tuple id="sg89ae">
         <timestamp>2004-11-11T08:57:29Z</timestamp>
         <status>
          <gp:geopriv>
            <gp:location-info>
              <cl:civilAddress>
                <cl:country>US</cl:country>
                <cl:A1>Illinois</cl:A1>
                <cl:A3>Chicago</cl:A3>
                <cl:HNO>233</cl:HNO>
                <cl:PRD>South</cl:PRD>
                <cl:A6>Wacker</cl:A6>
                <cl:STS>Drive</cl:STS>
                <cl:PC>60606</cl:PC>
                <cl:LMK>Sears Tower</cl:LMK>
                <cl:FLR>1</cl:FLR>
              <cl:civilAddress>
              <method>dhcp</method>
              <method>802.11</method>
              <provided-by>www.t-mobile.com</provided-by/>
            </gp:location-info>
            <gp:usage-rules>
              <gp:retransmission-allowed>no</gp:retransmission-allowed>



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              <gp:retention-expiry>2004-11-13T14:57:29Z</gp:retention-
                            expiry>
            </gp:usage-rules>
          </gp:geopriv>
         </status>
        </tuple>
       </presence>


--boundary1--



   The second probability in message flows is in Figure 4B. in which
   the first hop Proxy does not either: understand location, or does
   not know where the appropriate ERC is to route the message to.  In
   either case, that Proxy forwards the message to another Proxy for
   proper message routing ([11] talks to how this occurs).



   UA Alice       Proxy         Proxy          ERC


      | INVITE [M1] |             |             |
      |------------>|             |             |
      |             | INVITE [M2] |             |
      |             |------------>|             |
      |             |             | INVITE [M3] |
      |             |             |------------>|
      |             |             | 200 OK [M4] |
      |             |             |<------------|
      |             | 200 OK [M5] |             |
      |             |<------------|             |
      | 200 OK [M6] |             |             |
      |<------------|             |             |
      |   ACK [M7]                              |
      |---------------------------------------->|
      |                   RTP                   |
      |<=======================================>|
      |                                         |


      Figure 4B. UA-PROXY with Location in INVITE


   In message flows similar to 4A and/or 4B, the Record-Route header
   could be added by the proxies, this is OPTIONAL in usage and left to
   other documents to refine.


   In the case of an identifiable emergency call, something that cannot
   happen is for any Proxy to Challenge [per 1] the INVITE message.  In
   fact, while usage of the SIPS URI is encouraged and SHOULD be used,
   it MUST NOT be mandatory for successful message routing.  If the
   first SIPS INVITE fails for security property reasons, the second
   attempt by Alice (in these examples) MUST be allowed to be in the
   clear, not challenged, and routed properly.  Security mechanisms
   MUST NOT fail any call attempt, and if they do once, they MUST NOT



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   be mandatory for the subsequent attempt for a successful session
   set-up to an ERC.  The results of this are that the Proxy that
   failed the first attempt for security reasons MUST be aware of this
   failed attempt for the subsequent attempt that MUST process without
   failure a second time.   It must be assumed that the INVITE in any
   instance is considered "well formed".


   The remaining messages in both 4A and 4B are not included at this
   time.  If the working groups wants these added, they will be in the
   next revision of this document.



9.1.1 UA-to-Proxy Routing the Message with INVITE (unsecure)


   Below can be considered the initial unsecure INVITE M1 from Figures
   4A and 4A, or the second attempt message to an initial message that
   was failed by a Proxy.  This version of M1 is not using any security
   measures and is using the civic format message body that is the
   identical location to the previous example.



   [Message M1 from Figure 4A]


   INVITE sip:sos@atlanta.example.com SIP/2.0
   Via: SIP/2.0/TCP pc33.atlanta.example.com
     ;branch=z9hG4bK74bf9
   Max-Forwards: 70
   From: Alice <sip:alice@atlanta.example.com>;tag=9fxced76sl
   To: <sip:sos@atlanta.example.com>
   Call-ID: 3848276298220188511@atlanta.example.com
   CSeq: 31862 INVITE
   Contact: <sip:alice@atlanta.example.com>
   Content-Type: multipart/mixed; boundary=boundary1
   Contact-Length: ...


   --boundary1


   Content-Type: application/sdp
   v=0
   o=alice 2890844526 2890844526 IN IP4 atlanta.example.com
   c=IN IP4 10.1.3.33
   t=0 0
   m=audio 49172 RTP/AVP 0 4 8
   a=rtpmap:0 PCMU/8000


   --boundary1


   Content-type: application/cpim-pidf+xml
   <?xml version="1.0" encoding="UTF-8"?>
      <presence xmlns="urn:ietf:params:xml:ns:pidf"
          xmlns:gp="urn:ietf:params:xml:ns:pidf:geopriv10"
          xmlns:gml="urn:opengis:specification:gml:schema-



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                     xsd:feature:v3.0"
          entity="pres:alice@atlanta.example.com">
        <tuple id="sg89ae">
         <timestamp>2004-11-11T08:57:29Z</timestamp>
         <status>
          <gp:geopriv>
            <gp:location-info>
              <cl:civilAddress>
                <cl:country>US</cl:country>
                <cl:A1>Illinois</cl:A1>
                <cl:A3>Chicago</cl:A3>
                <cl:HNO>233</cl:HNO>
                <cl:PRD>South</cl:PRD>
                <cl:A6>Wacker</cl:A6>
                <cl:STS>Drive</cl:STS>
                <cl:PC>60606</cl:PC>
                <cl:LMK>Sears Tower</cl:LMK>
                <cl:FLR>1</cl:FLR>
              <cl:civilAddress>
              <method>dhcp</method>
              <method>802.11</method>
              <provided-by>www.t-mobile.com</provided-by/>
            </gp:location-info>
            <gp:usage-rules>
              <gp:retransmission-allowed>no</gp:retransmission-allowed>
              <gp:retention-expiry>2004-11-13T14:57:29Z</gp:retention-
                            expiry>
            </gp:usage-rules>
          </gp:geopriv>
         </status>
        </tuple>
       </presence>


--boundary1--



9.2 UA-to-Proxy Routing with UPDATE


   If the previous example of the location contained in the INVITE were
   to account for the movement of Alice (and her UA) before the ERC
   responded with a 200 OK, the UPDATE method is the appropriate SIP
   Request Method to use to update the proxies and ERC personnel that
   Alice has moved locations from where she initially made her set-up
   request.


   In this scenario (shown in the call flow of Figure 5A), Alice
   sending the UPDATE message here may cause the Proxy to CANCEL an
   existing pending INVITE Request, and retransmit INVITE to a NEW
   ERC(2), for example, if she walked across a street into a new ERC
   coverage area.  The Proxy MUST remain transaction stateful in order
   to be aware of the 200 OK Response from ERC1.  Upon receiving the
   UPDATE from Alice and analyzing the location provided by the message



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   looking for a location change, either forwarding that message to
   ERC1 if the change is still within ERC1's coverage area, or deciding
   to forward a message to another ERC covering where Alice is now
   (ERC2 in this case) with her new location.  If the latter change in
   destinations is required, the Proxy MUST CANCEL the pending INVITE
   to ERC1 (with a 487 "terminated request" being the specified
   response).


   SIPS SHOULD be used by Alice initially.  Upon any failure of the
   initial Request, Alice's UA MUST decide to send the new message
   without SIPS.



   UA Alice           Proxy         ERC1          ERC2


      |   INVITE [M1]   |             |             |
      |---------------->|             |             |
      |                 | INVITE [M2] |             |
      |                 |------------>|             |
      |   183 SP [M3]   |             |             |
      |<----------------|             |             |
      |    PRACK [M4]   |             |             |
      |---------------->|             |             |
      | 200 OK (PR)[M5] |             |             |
      |<----------------|             |             |
      |   UPDATE [M6]   |             |             |
      |---------------->|             |             |
      | 200 OK (UP)[M7] |             |             |
      |<----------------|             |             |
      |                 | CANCEL [M8] |             |
      |                 |------------>|             |
      |                 | 487 [M9]    |             |
      |                 |<------------|             |
      |                 | INVITE [M10]              |
      |                 |-------------------------->|
      |                 |        200 OK (INV) [M11] |
      |                 |<--------------------------|
      |200 OK (INV)[M12]|                           |
      |<----------------|                           |
      |   ACK [M13]                                 |
      |-------------------------------------------->|
      |                      RTP                    |
      |<===========================================>|
      |                                             |


      Figure 5A. UA-PROXY with Location in UPDATE


   ** see new open issue #9 for the problems with messages 8 through 10
   ** of the above flow.






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9.2.1 UA-to-Proxy Routing the Message with UPDATE (secure)


   INVITE sip:sos@atlanta.example.com SIP/2.0
   Via: SIP/2.0/TCP pc33.atlanta.example.com
     ;branch=z9hG4bK74bf9
   Max-Forwards: 70
   From: Alice <sip:alice@atlanta.example.com>;tag=9fxced76sl
   To: <sip:sos@atlanta.example.com>
   Call-ID: 3848276298220188511@atlanta.example.com
   CSeq: 31862 INVITE
   Contact: <sip:alice@atlanta.example.com>
   Content-Type: multipart/mixed; boundary=boundary1
   Contact-Length: ...


   --boundary1


   Content-Type: application/sdp
   v=0
   o=alice 2890844526 2890844526 IN IP4 atlanta.example.com
   c=IN IP4 10.1.3.33
   t=0 0
   m=audio 49172 RTP/AVP 0 4 8
   a=rtpmap:0 PCMU/8000


   --boundary1


   Content-type: application/cpim-pidf+xml
   <?xml version="1.0" encoding="UTF-8"?>
      <presence xmlns="urn:ietf:params:xml:ns:pidf"
          xmlns:gp="urn:ietf:params:xml:ns:pidf:geopriv10"
          xmlns:gml="urn:opengis:specification:gml:schema-
                     xsd:feature:v3.0"
          entity="pres:alice@atlanta.example.com">
        <tuple id="sg89ae">
         <timestamp>2004-11-11T08:57:29Z</timestamp>
         <status>
          <gp:geopriv>
            <gp:location-info>
              <cl:civilAddress>
                <cl:country>US</cl:country>
                <cl:A1>Illinois</cl:A1>
                <cl:A3>Chicago</cl:A3>
                <cl:HNO>233</cl:HNO>
                <cl:PRD>South</cl:PRD>
                <cl:A6>Wacker</cl:A6>
                <cl:STS>Drive</cl:STS>
                <cl:PC>60606</cl:PC>
                <cl:LMK>Sears Tower</cl:LMK>
                <cl:FLR>1</cl:FLR>
              <cl:civilAddress>
              <method>dhcp</method>
              <method>802.11</method>



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             <provided-by>www.cisco.com</provided-by/>
            </gp:location-info>
            <gp:usage-rules>
              <gp:retransmission-allowed>no</gp:retransmission-allowed>
              <gp:retention-expiry>2004-11-13T14:57:29Z</gp:retention-
                            expiry>
            </gp:usage-rules>
          </gp:geopriv>
         </status>
        </tuple>
       </presence>


--boundary1--


   Alice moves locations (with her UA detecting the movement), causing
   her UA to generate an UPDATE message ([M5] of Figure 3) prior to her
   UA receiving a final response from the ERC.  In this case, Alice has
   walked across the South Wacker Drive to another building.  Here is
   that message:


  [M5 UPDATE to ERC]


   UPDATE sips:bob@biloxi.example.com/TCP SIP/2.0
   Via: SIP/2.0/TLS pc33.atlanta.example.com
    ;branch=z9hG4bK776asdhds
   Max-Forwards: 70
   From: Alice <sip:alice@atlanta.example.com>;tag=9fxced76sl
   To: <sip:sos@atlanta.example.com>
   Call-ID: 3848276298220188511@atlanta.example.com
   CSeq: 10187 UPDATE
   Contact: <sip:alice@atlanta.example.com>
   Content-Type: multipart/mixed; boundary=boundary1
   Contact-Length: ...


   --boundary1


   Content-Type: application/sdp
   v=0
   o=alice 2890844526 2890844526 IN IP4 atlanta.example.com
   c=IN IP4 10.1.3.33
   t=0 0
   m=audio 49172 RTP/AVP 0 4 8
   a=rtpmap:0 PCMU/8000


   --boundary1


   Content-type: application/cpim-pidf+xml
   <?xml version="1.0" encoding="UTF-8"?>
      <presence xmlns="urn:ietf:params:xml:ns:pidf"
          xmlns:gp="urn:ietf:params:xml:ns:pidf:geopriv10"
          xmlns:gml="urn:opengis:specification:gml:schema-
                     xsd:feature:v3.0"



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          entity="pres:alice@atlanta.example.com">
        <tuple id="sg89ae">
         <timestamp>2004-11-11T08:57:29Z</timestamp>
         <status>
          <gp:geopriv>
            <gp:location-info>
              <cl:civilAddress>
                <cl:country>US</cl:country>
                <cl:A1>Illinois</cl:A1>
                <cl:A3>Chicago</cl:A3>
                <cl:HNO>250</cl:HNO>
                <cl:PRD>South Upper</cl:PRD>
                <cl:A6>Wacker</cl:A6>
                <cl:STS>Drive</cl:STS>
                <cl:PC>60606</cl:PC>
                <cl:NAM>Venice Cafe</cl:NAM>
                <cl:FLR>1</cl:FLR>
              <cl:civilAddress>
              <method>dhcp</method>
              <method>802.11</method>
              <provided-by>www.t-mobile.com</provided-by/>
            </gp:location-info>
            <gp:usage-rules>
              <gp:retransmission-allowed>no</gp:retransmission-allowed>
              <gp:retention-expiry>2004-11-13T14:57:29Z</gp:retention-
                            expiry>
            </gp:usage-rules>
          </gp:geopriv>
         </status>
        </tuple>
       </presence>


--boundary1--



9.2.2 UA-to-Proxy Routing the Message with UPDATE (unsecure)


   left blank for now



9.3 425 "Retry Location Body" Error Response


   In the case that a SIP Proxy detects an error in a message
   containing location information specific to that message body and
   has the location of that UAC locally, a new 400 level error needs to
   be sent back to the UAC to instruct the UAC to include the included
   location information message body in a subsequent message.  This
   document creates the new error code:


      425 (Retry Location Body)


   The UAC MUST ]retransmission of the failed message including this



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   new location information.  User agents may conclude they have
   already supplied a proper LO in the failed request.  That LO can be
   resent, but the Proxy supplied LO MUST be included as well.


   This new error code will be IANA registered.


   An example flow of this scenario will be included in the next
   version of this internet draft.



10.  Meeting RFC3693 Requirements


   Section 7.2 of [7] details the requirements of a "using protocol".
   They are:


   Req. 4.  The using protocol has to obey the privacy and security
      instructions coded in the Location Object and in the
      corresponding Rules regarding the transmission and storage of the
      LO.


   This document requires, in Section 7, that SIP entities sending or
   receiving location MUST obey such instructions.


   Req. 5.  The using protocol will typically facilitate that the keys
      associated with the credentials are transported to the respective
      parties, that is, key establishment is the responsibility of the
      using protocol.


   [1] and the documents it references define the key establish
   mechanisms.


   Req. 6.  (Single Message Transfer)  In particular, for tracking of
      small target devices, the design should allow a single
      message/packet transmission of location as a complete
      transaction.


   This document specifies that the LO be contained in the body of a
   single message.



11. Current Known Open issues


   This is a list of open issues that have not yet been addressed to
   conclusion:


   1) Should a Proxy somehow label its location information in the 4XX
      (Retry Location Body) message?


   2) Still have not determined how a SIP entity can request location
      to be delivered in a certain format (civil vs. coordinate).


   3) Still have not determined how a UAC can request the UAS return



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      its location in a 1XX or 2XX response


   4) Still have not determined if a Redirect model should be accounted
      for (if the 3XX response includes LI, does that get included in
      the new Request by the UAC?)


   5) This document needs to be renamed within SIPPING to remove the
      "requirements" portion


   6) From section 9.2 (Emergency call with an updated location), if
      Alice does venture into another coverage area, how does her new
      UPDATE with new location get sent to a second (and now
      appropriate) ERC(2)?


      The pending INVITE needs to be cancelled or able to be
      sequentially forked (which not all Proxies will be able to do).
      Without that occurring, the new UPDATE will not cause a new
      INVITE to be originated from the Proxy towards ERC2... and what
      happens to the UPDATE message (which cannot be an original
      request into ERC2)?



12.  New Open Issues


   These are new open issues to be addressed within this document or
   the topics/areas dropped from consideration:


   1) May add a section for end-to-middle in a services model


   2) Is there a need to create a new events package for a subscription
      to a UA to get it's location either at periodic time intervals or
      when the UA has determined it has moved?



13.  Security Considerations


   Conveyance of geo-location of a UAC is problematic for many reasons.
   This document calls for that conveyance to normally be accomplished
   through secure message body means (like S/MIME or TLS).  In cases
   where a session set-up is routed based on the location of the UAC
   initiating the session or SIP MESSAGE, securing the location with an
   end-to-end mechanism such as S/MIME is problematic.



14.  IANA Considerations


   This section defines two new 4XX error response codes within the
   sip-parameters section of IANA.  [NOTE: RFC XXXX denotes this
   document.






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14.1 IANA Registration for Response Code 4XX


   RFC number: XXXX
   Response code: 424
   Default reason phrase: Bad Location Information


14.2 IANA Registration for Response Code 4XX


   RFC number: XXXX
   Response code: 425
   Default reason phrase: Retry Location Body



15.  Acknowledgements


   To Dave Oran for helping to shape this idea. To Jon Peterson and
   Dean Willis on guidance of the effort. To Henning Schulzrinne,
   Jonathan Rosenberg, Dick Knight, and Keith Drage for constructive
   feedback.



16. References


16.1 References - Normative


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


 [2] S. Bradner, "Key words for use in RFCs to indicate requirement
     levels," RFC 2119, Mar. 1997.


 [3] H. Schulzrinne, "draft-ietf-sipping-sos-00.txt", Internet
     Draft, Feb 2004, Work in progress


 [4] B. Campbell, Ed., J. Rosenberg, H. Schulzrinne, C. Huitema, D.
     Gurle, "Session Initiation Protocol (SIP) Extension for Instant
     Messaging" , RFC 3428, December 2002


 [5] J. Polk, J. Schnizlein, M. Linsner, " DHCP Option for Location
     Configuration Information", RFC 3825, July 2004


 [6] H. Schulzrinne, "draft-ietf-geopriv-dhcp-civic-03.txt", Internet
     Draft, July 04, Work in progress


 [7] J. Cuellar, J. Morris, D. Mulligan, J. Peterson. J. Polk, "Geopriv
     Requirements", RFC 3693, February 2004


 [8] J. Rosenberg, "Requirements for Session Policy for the Session
     Initiation Protocolö, draft-ietf-sipping-session-policy-req-00",
     Internet Draft, June, 2003, "work in progress"




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 [9] J. Rosenberg, "The Session Initiation Protocol (SIP) UPDATE
     Method", RFC 3311, October 2002


 [10] A. Niemi, Ed., "draft-ietf-sip-publish-04", Internet Draft, May
      2004, work in progress


 [11] H. Schulzrinne, B. Rosen, "draft-schulzrinne-sipping-emergency-
      arch", Internet Draft, Feb 2004, work in progress


 [12] "Requirements for End to Middle Security in SIP",
      draft-ietf-sipping-e2m-sec-reqs-03.txt, Internet Draft, June
      2004, work in progress,


 [13] J. Peterson, "draft-ietf-geopriv-pidf-lo-02", Internet Draft, May
      2004, work in progress


 [14] J. Rosenberg, H. Schulzrinne, "The Offer/Answer Model with
      Session Description Protocol", RFC 3264, June 2002


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



17. Author Information


   James M. Polk
   Cisco Systems
   2200 East President George Bush Turnpike          33.00111N
   Richardson, Texas 75082 USA                       96.68142W
   jmpolk@cisco.com



   Brian Rosen                                       40.4N
   br@brianrosen.net                                 80.0W



Full Copyright Statement


   Copyright (C) The Internet Society (2004).  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 "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.






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Intellectual Property


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Acknowledgement


   Funding for the RFC Editor function is currently provided by the
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The Expiration date for this Internet Draft is:


April 25th, 2005



















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