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Versions: 00 01 02                                                      
Internet Engineering Task Force                           James M. Polk
Internet Draft                                            Cisco Systems
Expiration: Aug 9th, 2004                                   Brian Rosen
File: draft-ietf-sipping-location-requirements-00.txt           Marconi





                           Requirements for
           Session Initiation Protocol Location Conveyance


                          February 9th, 2003





Status of this Memo


   This document is an Internet-Draft and is in full conformance
   with all provisions of Section 10 of RFC2026.


   Internet-Drafts are working documents of the Internet Engineering
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Abstract


   This document presents the framework and requirements for an
   extension to the Session Initiation Protocol (SIP) [1] for
   conveyance of user location information from a Session Initiation
   Protocol (SIP) user agent 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.





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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .  2
       1.1 Conventions . . . . . . . . . . . . . . . . . . . . . . .  3
       1.2 Changes from Individual Submission Versions . . . . . . .  3
   2.  In the Body or in a Header  . . . . . . . . . . . . . . . . .  4
   3.  Scope of Location in a Message Body . . . . . . . . . . . . .  5
   4.  Requirements for UA-to-UA Location Conveyance . . . . . . . .  5
   5.  Requirements for UA-to-Proxy Server Location Conveyance . . .  5
   6.  Additional Requirements for Emergency Calls . . . . . . . . .  6
   7.  Current Known Open issues . . . . . . . . . . . . . . . . . .  8
   8.  Security Considerations . . . . . . . . . . . . . . . . . . .  8
   9.  IANA Considerations   . . . . . . . . . . . . . . . . . . . .  8
   10. Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  9
   11. References  . . . . . . . . . . . . . . . . . . . . . . . . .  9
   12. Author Information  . . . . . . . . . . . . . . . . . . . . .  9



1.  Introduction


   This document presents the framework and requirements for an
   extension to the Session Initiation Protocol (SIP) [1] for
   conveyance of user location information object described by [7] from
   a SIP User Agent 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 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, accurate location information of the caller in
   distress is a required component of a call to an emergency center.


   A third 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



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   configured with its location (either coordinate or civil based).  It
   also does not discuss the contents of the Location Object (LO).  It
   does specify the requirements for the "using protocol" in [7].



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 Individual Submission Versions


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


   - 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).



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   - 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 civil) 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
   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 UAS and
   UAC, 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.




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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.



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 - The UAC SHOULD indicate in the SIP message that includes
           location information where the LI came from (IANA registered
           codes for GPS, Cell Tower Triangulation, WiFi, DHCP, manual
           entry - as examples).



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



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    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 CANNOT 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 - The UAC SHOULD indicate in the SIP message that includes
            location information where the LI came from (IANA
            registered codes for GPS, Cell Tower Triangulation, WiFi,
            DHCP, manual entry - as examples).



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
   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



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   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.


    E-6 The UAC SHOULD be able to inform the ERC that the location
        information provided in the SIP message might be wrong.


   Requirements U-U4 and U-PS8 stipulate the inclusion of how the UAC
   learned its location.  This can be especially useful to an ERC
   operator attempting to learn all that is possible from this remote
   person in distress.  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 not provide the (overwritten?) location information
        provided by a VPN (in lieu of the LI from the local network).




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    E-8 The UA SHOULD include within the location conveyance to the ERC
        that it is (or recently was) connected to a VPN.



7.  Current Known Open issues


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


   1) Whether SIP Proxies SHOULD be able to insert location information
      into an emergency call set-up (the INVITE)?


      1a) This has the additional implication of whether or not, or
          regardless of the fact the UAC already inserted location into
          the sos@localdomain INVITE.


      1b) Should the Proxy somehow differentiate its location
          information from that provided by the UAC (with each LI
          having a SIP entity (type?) originator label?


      1c) Should there be any behavior difference with respect to Open
          Issue #1b if the Proxy does not know or cannot tell if the
          UAC inserted location information (further emphasizing the
          need for some form of originator label)?


   2) Whether SIP Proxies SHOULD be able to return location information
      in a Redirect message to the UAC making the emergency call?


   3) If S/MIME is chosen as a SHOULD (in general, vs. TLS), this doc
      might consider stipulating a special purpose Proxy (an "emergency
      services" proxy) that can process location information (a Geopriv
      LO) and route the message directly to the appropriate ERC.


       At Issue: plain "vanilla" proxies probably won't have the
       capabilities to route based on location information in the
       near future, but should that timing be considered here?



8.  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.



9.  IANA Considerations


   There are no IANA considerations within this document at this time.



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10.  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.



11. 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-schulzrinne-sipping-sos-04.txt", Internet
     Draft, Jan 03, 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, " draft-ietf-geopriv-dhcp-lci-
     option-03.txt", Internet Draft, Dec 2003, Work in progress


 [6] H. Schulzrinne, "draft-schulzrinne-geopriv-dhcp-civil-01.txt",
     Internet Draft, Feb 03, Work in progress


 [7] J. Cuellar, J. Morris, D. Mulligan, J. Peterson. J. Polk, "draft-
     ietf-geopriv-reqs-04.txt", Internet Draft, Oct 03, Work in
     progress


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



12. Author Information


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






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   Brian Rosen
   Marconi Communications, Inc.
   2000 Marconi Drive
   Warrendale, PA 15086
   Brian.rosen@marconi.com



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   This document and the information contained herein is provided on an
   "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
   TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
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   HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
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The Expiration date for this Internet Draft is:


August 9th, 2004






































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