SIPCORE                                                  J. Winterbottom
Internet-Draft                               Winterb Consulting Services
Updates: RFC6442 (if approved)                                 R. Jesske
Intended status: Standards Track                        Deutsche Telekom
Expires: January 23, March 19, 2020                                       B. Chatras
                                                             Orange Labs
                                                               A. Hutton
                                                           July 22,
                                                      September 16, 2019

     Location Source Parameter for the SIP Geolocation Header Field


   There are some circumstances where a geolocation 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.  This document defines the
   location-source parameter so that the entity adding the location
   value to Geolocation header field can identify itself using its

Status of This Memo

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   This Internet-Draft will expire on January 23, March 19, 2020.

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Table of Contents

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

1.  Introduction

   The SIP geolocation Geolocation specification [RFC6442] describes the
   "Geolocation" SIP header field which is used to indicate that the SIP
   message is conveying location information.  The specification
   suggests  [RFC6442] specifies that only one location value
   SIP intermediaries should be conveyed. not add location values to a SIP request
   that already contains location value.  [RFC6442] also states that if
   a SIP intermediary adds location it is fully responsible for
   addressing the concerns of any 424 (Bad Location Information) SIP
   response it receives.  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 is the same as 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 Geolocation header field.

   This document adds a location-source (loc-src) parameter to the
   location values in [RFC6442] so that extends the Geolocation header field, by allowing an
   entity adding the location value to geolocation header field can identify identity itself using its a hostname.  How
   This is done by defining a new geoloc-param header field parameter,
   location-source."How the entity adding the location value to the
   header field obtains the location information is out of scope of this

2.  Terminology

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "OPTIONAL" in this document are to be interpreted as described in BCP
   14 [RFC2119] [RFC8174] when, and only when, they appear in all
   capitals, as shown here.

3.  Rationale

   The primary intent of the location-source parameter defined in this specific
   specification 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
   and that there is a need to identify the entity adding the location

   The location-source parameter defined in this specification adds the location source generating the
   location value to increase the trustworthiness of the location

   The loc-src location-source parameter is applicable within a single private
   administrative domain or between different administrative domains
   where there is a trust relationship between the domains.  Thus it is
   intended to use this parameter only in trust domains where Spec(T) as
   described in [RFC3325] exists.

   The loc-src location-source parameter is not included in a SIP message sent
   to another network if there is no trust relationship.  The The loc-src
   location-source parameter is not applicable if the administrative
   domain manages emergency calls in a way that does not require location source
   generating any
   generation of the location.

   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 Geolocation header field.  The Augmented BNF
   (ABNF) [RFC5234] for this parameter is shown in Figure 1.

          location-source = "loc-src=" (hostname ) "loc-src" EQUAL hostname
          hostname = <defined in RFC3261>

                         Figure 1: Location Source

   Only a fully qualified host name is valid, an valid.  The syntax does not
   support IP address MUST NOT be
   added by addresses, and if an entity conforming with this specification.  If a node
   conforming to this
   specification receives a geolocation Geolocation header field with a loc-src location-
   source parameter containing an IP address then the parameter MUST be

   Any proxy

   A SIP intermediarity conformant to this specification adding a
   location value to a geolocation Geolocation header field SHOULD also add its host name using the loc-src a
   location-source header field parameter so that it is clearly
   identified as the node adding the location.  A UE UA MUST NOT
   provide insert a loc-src parameter value.
   location-source header field parameter.  If a proxy SIP intermediarity
   receives a message from an untrusted source with the loc-src location-source
   parameter set then it MUST remove the loc-src location-source 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 SIP
   intermediarity which identifies itself using the loc-src location-source

      INVITE SIP/2.0
      Via: SIP/2.0/TLS;branch=z9hG4bK74bf9
      Max-Forwards: 70
      To: Bob <>
      From: Alice <>;tag=9fxced76sl
      Geolocation: <>,
      Geolocation-Routing: yes
      Accept: application/sdp, application/pidf+xml
      CSeq: 31862 INVITE
      Contact: <>
      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 location-source
   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 SIP intermediarity to
   insert a host name indicating the that they added the specific location
   value to the geolocation 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

   As already stated in [RFC6442] securing the location hop- by-hop,
   using TLS, protects the message from eavesdropping and modification
   in transit, but exposes the information to all proxies SIP intermediaries on
   the path as well as the endpoint.  The loc-src location-source parameter is
   applicable within a single private administrative domain or between
   different administrative domains where there is a trust relationship
   between the domains.  If such trust domain is not given it is
   strongly recommended to delete the location information.

   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 removed when passed to an other domain.

8.  IANA Considerations

8.1.  Registration of loc-src Parameter location-source parameter for geolocation Geolocation header

   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

   Header Field:  geolocation  Geolocation

   Parameter Name:  loc-src

9.  Acknowledgements

   The authors would like to thank Dale Worley and Christer Holmberg for his
   their extensive review of the draft The authors would like to
   acknowledge the constructive feedback provided by Paul Kyziva Kyzivat and Christer Holmberg.
   Robert Sparks.

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,

   [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,

   [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,

   [RFC5234]  Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax
              Specifications: ABNF", STD 68, RFC 5234,
              DOI 10.17487/RFC5234, January 2008,

   [RFC6442]  Polk, J., Rosen, B., and J. Peterson, "Location Conveyance
              for the Session Initiation Protocol", RFC 6442,
              DOI 10.17487/RFC6442, December 2011,

   [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
              2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
              May 2017, <>.

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,

              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

   Phone: +61 448 266004

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


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


   Andrew Hutton
   Mid City Place
   London  WC1V 6EA