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Dispatch                                                 J. Winterbottom
Internet-Draft                               Winterb Consulting Services
Updates: RFC6442 (if approved)                                 R. Roland
Intended status: Standards Track                                L. Liess
Expires: July 3, 2017                                   Deutsche Telekom
                                                              B. Chatras
                                                             Orange Labs
                                                               A. Hutton
                                                                   Unify
                                                       December 30, 2016


     Location Source Parameter for the SIP Geolocation Header Field
              draft-winterbottom-dispatch-locparam-02.txt

Abstract

   There are some circumstances where a geolocation header field may
   contain more than one location value.  Knowing the identity of the
   node adding the location value allows the recipient more freedom in
   selecting the value to look at first rather than relying solely on
   the order of the location values.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
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   Drafts is at http://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
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   This Internet-Draft will expire on July 3, 2017.

Copyright Notice

   Copyright (c) 2016 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info) in effect on the date of



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   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  Rationale . . . . . . . . . . . . . . . . . . . . . . . . . .   3
   4.  Mechanism . . . . . . . . . . . . . . . . . . . . . . . . . .   4
   5.  Example . . . . . . . . . . . . . . . . . . . . . . . . . . .   4
   6.  Privacy Considerations  . . . . . . . . . . . . . . . . . . .   5
   7.  Security Considerations . . . . . . . . . . . . . . . . . . .   5
   8.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   5
     8.1.  Registration of loc-src Parameter for geolocation header
           field . . . . . . . . . . . . . . . . . . . . . . . . . .   6
   9.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   6
   10. References  . . . . . . . . . . . . . . . . . . . . . . . . .   6
     10.1.  Normative References . . . . . . . . . . . . . . . . . .   6
     10.2.  Informative References . . . . . . . . . . . . . . . . .   7
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   7



























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1.  Introduction

   The SIP geolocation specification [RFC6442] describes a SIP header
   field that is used to indicate that the SIP message is conveying
   location information.  The specification suggests that only one
   location value should be conveyed.  However, some communications
   architectures, such as 3GPP [TS23-167] and ETSI [M493], prefer to use
   information provided by edge-proxies or acquired through the use of
   core-network nodes, before using information provided solely by user
   equipment (UE).  These solutions don't preclude the use of UE
   provided location but require a means of being able to distinguish
   the identity of the node adding the location value to the SIP message
   from that provided by the UE.  [RFC6442] stipulates that the order of
   location values in the geolocation header field aligns with the order
   in which they were added to the header field.  Whilst this order
   provides guidance to the recipient as to which values were added to
   the message earlier in the communication chain, it does not provide
   any indication of which node actually added the location value.
   Knowing the identity of the entity that added the location to the
   message allows the recipient to choose which location to consider
   first rather than relying solely on the order of the location values
   in the geolocation header field.

   This document adds a location-source (loc-src) parameter to the
   location values in [RFC6442] so that the entity adding the location
   value to geolocation header field can identify itself using its
   hostname.  How the entity adding the location value to the header
   field obtains the location information is out of scope of this
   document.

2.  Terminology

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in [RFC2119].

3.  Rationale

   The primary intent of the parameter defined in this specific is for
   use in emergency calling.  There are various architectures defined
   for providing emergency calling using SIP-based messaging.  Each has
   it own characteristics with corresponding pros and cons.  All of them
   allow the UE to provide location information, however, many also
   attach other sources of location information to support veracity
   checks, provide backup information, or to be used as the primary
   location.  This document makes no attempt to comment on these various
   architectures or the rationale for them wishing to include multiple
   location values.  It does recognize that these architectures exist



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   and that there is a need to identify the entity adding the location
   information.

   The parameter defined in this specification adds the location source
   generating the location value to increase the trustworthiness of the
   location information.  Thus it is intended to use this parameter in
   trust domains where Spec(T) as described in [RFC3325] exists only.
   The functional architecture described within ETSI [M493] is an
   example of architecture where this parameter makes sense to be used.

4.  Mechanism

   The mechanism employed adds a parameter to the location value defined
   in [RFC6442] that identifies the hostname of the entity adding the
   location value to the geolocation header field.  The Augmented BNF
   (ABNF) [RFC5234] for this parameter is shown in Figure 1.


          location-source = "loc-src=" (host / other-loc-src)
          other-loc-src = token


                         Figure 1: Location Source

   Only a fully qualified host name is valid, an IP address MUST NOT be
   added by an entity conforming with this specification.  If a node
   conforming to this specification receives a geolocation header field
   with a loc-src parameter containing an IP address then the parameter
   MUST be removed.

   Any proxy adding a location value to a geolocation header field
   SHOULD also add its host name using the loc-src parameter so that it
   is clearly identified as the node adding the location.  A UE MUST NOT
   provide a loc-src parameter value.  If a proxy receives a message
   from an untrusted source with the loc-src parameter set then it MUST
   remove the loc-src parameter before passing the message into a
   trusted network.

5.  Example

   The following example shows a SIP INVITE message containing a
   geolocation header field with two location values.  The first
   location value points to a PIDF-LO in the SIP body using a content-
   indirection (cid:) URI per [RFC4483] and this is provided by the UE.
   The second location value is an https URI the provided by a proxy
   which identifies itself using the loc-src parameter.





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      INVITE sips:bob@biloxi.example.com SIP/2.0
      Via: SIPS/2.0/TLS pc33.atlanta.example.com;branch=z9hG4bK74bf9
      Max-Forwards: 70
      To: Bob <sips:bob@biloxi.example.com>
      From: Alice <sips:alice@atlanta.example.com>;tag=9fxced76sl
      Call-ID: 3848276298220188511@atlanta.example.com
      Geolocation: <cid:target123@atlanta.example.com>,
           <https://lis.example.com:8222/y77syc7cuecbh>;
                    loc-src=edgeproxy.example.com
      Geolocation-Routing: yes
      Accept: application/sdp, application/pidf+xml
      CSeq: 31862 INVITE
      Contact: <sips:alice@atlanta.example.com>
      Content-Type: multipart/mixed; boundary=boundary1
      Content-Length: ...

                    Figure 2: Example Location Request.

6.  Privacy Considerations

   This document doesn't change any of the privacy considerations
   described in [RFC6442].  While the addition of the loc-src parameter
   does provide an indicator of the entity that added the location in
   the signaling path this provides little more exposure than a proxy
   identity being added to the record-route header field.

7.  Security Considerations

   This document introduces the ability of a proxy or middle box to
   insert a host name indicating the that they added the specific
   location value to the geolocation header field.  The intent is for
   this field to be used by the location recipient in the event that the
   SIP message contains multiple location values.  As a consequence this
   parameter should only be used by the location recipient in a trusted
   network.

   The use of this parameter is not restricted to a specific
   architecture but using multiples locations and loc-src may end in
   compatibility issues.  [RFC6442] already addresses the issue of
   multiples locations.  To avoid problems of wrong interpretation of
   loc-src the value may be discarded when passed to an other domain.

8.  IANA Considerations








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8.1.  Registration of loc-src Parameter for geolocation header field

   This document calls for IANA to register a new SIP header parameter
   as per the guidelines in [RFC3261], which will be added to header
   sub-registry under http://www.iana.org/assignments/sip-parameters.

   Header Field:  geolocation

   Parameter Name:  loc-src

9.  Acknowledgements

   NONE

10.  References

10.1.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <http://www.rfc-editor.org/info/rfc2119>.

   [RFC3261]  Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston,
              A., Peterson, J., Sparks, R., Handley, M., and E.
              Schooler, "SIP: Session Initiation Protocol", RFC 3261,
              DOI 10.17487/RFC3261, June 2002,
              <http://www.rfc-editor.org/info/rfc3261>.

   [RFC3325]  Jennings, C., Peterson, J., and M. Watson, "Private
              Extensions to the Session Initiation Protocol (SIP) for
              Asserted Identity within Trusted Networks", RFC 3325,
              DOI 10.17487/RFC3325, November 2002,
              <http://www.rfc-editor.org/info/rfc3325>.

   [RFC5234]  Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax
              Specifications: ABNF", STD 68, RFC 5234,
              DOI 10.17487/RFC5234, January 2008,
              <http://www.rfc-editor.org/info/rfc5234>.

   [RFC6442]  Polk, J., Rosen, B., and J. Peterson, "Location Conveyance
              for the Session Initiation Protocol", RFC 6442,
              DOI 10.17487/RFC6442, December 2011,
              <http://www.rfc-editor.org/info/rfc6442>.







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10.2.  Informative References

   [M493]     European Telecommunications Standards Institute,
              "Functional architecture to support European requirements
              on emergency caller location determination and transport",
              ES 203 178, V 1.1.1, Februar 2015.

   [RFC4483]  Burger, E., Ed., "A Mechanism for Content Indirection in
              Session Initiation Protocol (SIP) Messages", RFC 4483,
              DOI 10.17487/RFC4483, May 2006,
              <http://www.rfc-editor.org/info/rfc4483>.

   [TS23-167]
              3rd Generation Partnership Project, "3rd Generation
              Partnership Project; Technical Specification Group
              Services and System Aspects; IP Multimedia Subsystem (IMS)
              emergency sessions", TS 23.167, V 12.1.0, March 2015.

Authors' Addresses

   James Winterbottom
   Winterb Consulting Services
   Gwynneville, NSW  2500
   AU

   Phone: +61 448 266004
   Email: a.james.winterbottom@gmail.com


   Roland Jesske
   Deutsche Telekom
   Heinrich-Hertz Str, 3-7
   Darmstadt  64295
   Germany

   Email: r.jesske@telekom.de
   URI:   www.telekom.de


   Laura Liess
   Deutsche Telekom
   Heinrich-Hertz Str, 3-7
   Darmstadt  64295
   Germany

   Email: l.liess@gmail.com





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   Bruno Chatras
   Orange Labs
   38-40 rue du General Leclerc
   Issy Moulineaux Cedex 9  F-92794
   France

   Email: bruno.chatras@orange.com


   Andrew Hutton
   Unify
   Technology Drive
   Nottingham  NG9 1LA
   UK

   Email: andrew.hutton@unify.com



































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