ECRIT                                                     H. Schulzrinne
Internet-Draft                                       Columbia University
Intended status: Informational                                  L. Liess
Expires: August 25, 2010                                Deutsche Telekom
                                                           H. Tschofenig
                                                  Nokia Siemens Networks
                                                                B. Stark
                                                                A. Kuett
                                                       February 21, 2010

          Location Hiding: Problem Statement and Requirements


   The emergency services architecture developed in the IETF Emergency
   Context Resolution with Internet Technology (ECRIT) working group
   describes an architecture where location information is provided by
   access networks to end points or VoIP service providers in order to
   determine the correct dial string and information to route the call
   to a Public Safety Answering Point (PSAP).  For determining the PSAP
   Uniform Resource Identifier (URI) the usage of the Location-to-
   Service Translation (LoST) Protocol is envisioned.

   This document provides a problem statement and lists requirements for
   situations where the Internet Access Provider (IAP) and/or the
   Internet Service Provider (ISP) are only willing to disclose limited
   or no location information.

Status of this Memo

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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . . . 4
     1.1.  Emergency Services Architecture . . . . . . . . . . . . . . 4
     1.2.  Location Hiding . . . . . . . . . . . . . . . . . . . . . . 4
     1.3.  Location by Reference . . . . . . . . . . . . . . . . . . . 5
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . . . 5
   3.  Requirements  . . . . . . . . . . . . . . . . . . . . . . . . . 6
   4.  IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 8
   5.  Security Considerations . . . . . . . . . . . . . . . . . . . . 8
   6.  Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . 8
   7.  References  . . . . . . . . . . . . . . . . . . . . . . . . . . 8
     7.1.  Normative References  . . . . . . . . . . . . . . . . . . . 8
     7.2.  Informative References  . . . . . . . . . . . . . . . . . . 9
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . . . 9

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1.  Introduction

1.1.  Emergency Services Architecture

   The emergency services architecture developed in the IETF Emergency
   Context Resolution with Internet Technology (ECRIT) working group,
   see [I-D.ietf-ecrit-framework], describes an architecture where
   location information is provided by access networks to end points or
   VoIP service providers in order to determine the correct dial string
   and information to route the call to a Public Safety Answering Point
   (PSAP).  The Location-to-Service Translation (LoST) Protocol
   [RFC5222] allows callers and other call-routing entities to determine
   the PSAP Uniform Resource Identifier (URI) for a specific
   geographical location together with a service URI [RFC5031].  The
   basic architecture is shown in Figure 1 of [I-D.ietf-ecrit-framework]
   and further detailed in the message flow in Figure 2 of

   For emergency services, location information is needed in three ways:
   1.  Emergency call routing to the PSAP that is responsible for a
       specific geographical region
   2.  Dispatch of the emergency personnel to the scene of an accident,
       crime or other types of incidents
   3.  Additionally, a Voice Service Provider (VSP) may need to verify
       that an call is indeed an emergency call and may therefore
       require location information to ensure that calls routed to a
       specific URI point to a PSAP.

   This document focuses on item (1) and item (3).  Providing location
   information by the ISP to the PSAP and to the emergency personnel are
   typically legal obligations covered by regulatory frameworks.

1.2.  Location Hiding

   Internet Access Providers (IAPs) and Internet Service Providers
   (ISPs)) typically have little incentives to provide location
   information to end hosts or independent VSPs (without monetary
   compensation) for any purpose, including for emergency call routing.
   The decision to deny disclosure of location information can be driven
   by a number of technical and business concerns.  Some providers may
   perceive a risk that allowing users to access location information
   for non-emergency purposes or prior to an emergency call will incur
   additional server load and thus costs.  Other providers may not want
   to make location information available without the ability to charge
   for it.  Yet others fear problems with regard to privacy when
   disclosing location information to potentially unknown third parties.

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1.3.  Location by Reference

   The work on the Location Configuration Protocol (LCP) indicated the
   need to provide the capability to obtain Location-by-References
   (LbyRs) in addition to Location-by-Value (LbyV) from a Location
   Information Server (LIS).

   The LCP problem statement and requirements document can be found in
   [I-D.ietf-geopriv-l7-lcp-ps].  The requirements for obtaining an LbyR
   via the LCP and the corresponding dereferencing step can be found in

   HTTP Enabled Location Delivery (HELD), see
   [I-D.ietf-geopriv-http-location-delivery], is an instantiation of the
   LCP concept and allows LbyVs and LbyRs to be requested.

   A location reference may already satisfy the requirement for location
   hiding if the PSAP has the appropriate credentials to resolve the
   reference.  These credentials allow the ISP/IAP to authenticate and
   to authorize the party that would like to request location
   information.  The policy to obtain these credentials allows ISPs/IAPs
   to put constraints under which these credentials are handed out.
   ISP/IAPs ideally might want to engage in a business relationship with
   the VSP to receive a financial compensation for the service they
   provide.  On the Internet the number of VSPs is potentially large and
   the VSPs would not want to enter a business contract with potentially
   every ISP/IAP worldwide.  The number of potential contracts between
   ISPs/IAPs and PSAPs is, however, relatively small as they typically
   need to have a local relationship as PSAPs provide their emergency
   services support in a certain geographical region for which certain
   ISPs/IAPs have networks deployed.

   Note that the requirement being met here is for delivery of location
   information to the PSAP, not for LoST routing or for validation at
   the VSP.  Another obstacle when it comes to the usage of location
   reference for location-based routing from a technical point of view
   is that a location reference cannot be used as input to LoST
   [RFC5222], as LoST requires location per value rather than a
   reference.  Also, LoST servers may be operated by independent
   parties, including VSPs, which again may not be able to resolve the
   reference to location by value.  (Note that LoST is a protocol used
   for determining the location-appropriate PSAP based on location
   information and a Service URN [RFC5031].

2.  Terminology

   The keywords "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",

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   document are to be interpreted as described in [RFC2119], with the
   important qualification that, unless otherwise stated, these terms
   apply to the design of an solution supporting location hiding, not
   its implementation or application.

   This document reuses terminology from [I-D.ietf-geopriv-l7-lcp-ps].

3.  Requirements

   Req-1:  There MUST be a way for the ISP/IAP to withhold precise
      location information from the endpoint and from the VSP.

   Req-2:  The ISP/IAP MUST support the ability of the endpoint or the
      VSP to route emergency calls.

   Req-3:  The VSP MUST be able to validate that a call purported to be
      an emergency call is being routed to a bona fide URI, which is
      denoted by being a URI in LoST for the designated emergency
      service.  This requirement is provided to deal with potential
      security problems described in Section 5.1 of [RFC5069].

   Req-4:  The PSAP MUST receive precise location information (by value)
      about emergency callers.  As such, any solution MUST be able to
      provide location information to the PSAP even while withholding it
      from the emergency caller.
   Req-5:  The proposed solution MUST NOT assume a business or trust
      relationship between the caller's VSP and the caller's ISP.

   Req-6:  A solution MUST consider deployment scenarios where a VSP
      does not operate in the same jurisdiction as the PSAP.

   Req-7:  The solution MUST offer automated discovery of servers and
      and other necessary configuration information.  No manual
      configuration can be assumed.

   Req-8:  The steps needed by the endpoint for emergency calling SHOULD
      be no different when location is withheld vs. when location is not
      withheld.  In particular, user agents cannot require additional
      configuration to discover which particular environment (hiding or
      no hiding) they find themselves in.

   Req-9:  The solution SHOULD work without the ISP/IAP having to
      support SIP and without the need to utilize SIP between the
      endpoint and the VSP.

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   Req-10:  The solution MUST work if PSAP boundaries have holes.  (For
      a discussion about holes in PSAP boundaries and their encoding the
      reader is referred to [I-D.ietf-ecrit-specifying-holes].)

   Req-11:  The solution MUST NOT assume the existence of Emergency
      Service Routing Proxies (ESRPs) per country, state and city.

   Req-12:  The solution MUST consider that service boundaries for
      different emergency services may differ, but they overlap at the
      location of the caller.

   Req-13:  Though the solution MAY add steps to the emergency call
      routing process described in [I-D.ietf-ecrit-framework], these
      steps MUST NOT significantly increase call setup latency.  For
      example, the revised process MUST NOT include "trial-and-error"
      operations on its critical path, such as attempts at LbyR
      resolutions that may take time to time out.

   Req-14:  The solution MUST allow the end host to determine PSAP/ESRP
      URLs prior to the call, for all emergency services.

   Req-15:  The solution MUST allow UAs to discover at least their dial
      string ahead of the emergency call.

   Req-16:  The solution MUST have minimal impact on UAs, i.e., a
      solution is preferred if it does not require an substantially
      different emergency services procedures compared to the procedure
      of dealing with emergency services where no location hiding is

   Req-17:  The solution MUST NOT interfere with the use of LoST for
      non-emergency services.

   Req-18:  The solution MUST allow emergency calls to reach an IP-to-
      PSTN gateway rather than the IP-based PSAP directly.

   Req-19:  The solution MUST NOT shift effort (externality), i.e., the
      convenience of the location-hiding ISP MUST NOT impose a burden on
      user agents or non-hiding ISPs/IAPs and SHOULD NOT impose a burden
      on VSPs.

   Req-20:  The solution SHOULD minimize the impact on LoST, SIP
      conveyance [I-D.ietf-sipcore-location-conveyance] and DHCP.

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   Req-21:  The solution SHOULD NOT break in the presence of NATs and
      SHOULD consider the presence of legacy devices, as described in

4.  IANA Considerations

   This document does not require actions by IANA.

5.  Security Considerations

   This document does not raise additional security consideration beyond
   those mentioned in [I-D.ietf-geopriv-l7-lcp-ps] and discussed in this

6.  Acknowledgments

   We would like to thank the following ECRIT working group members (in
   no particular order) for their contributions:

   o  Andrew Newton (
   o  James Winterbottom (
   o  Brian Rosen (
   o  Richard Barnes (
   o  Marc Linsner (
   o  Ted Hardie (

   The authors would also like to thank Ben Campbell for his Gen-ART
   review.  Additionally, we would like to thank Jari Arkko, Alexey
   Melnikov, Tim Polk, and Dan Romascanu for their IESG review.

7.  References

7.1.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", March 1997.

              Tschofenig, H. and H. Schulzrinne, "GEOPRIV Layer 7
              Location Configuration Protocol; Problem Statement and
              Requirements", draft-ietf-geopriv-l7-lcp-ps-10 (work in
              progress), July 2009.


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              Polk, J. and B. Rosen, "Location Conveyance for the
              Session Initiation Protocol",
              draft-ietf-sipcore-location-conveyance-02 (work in
              progress), February 2010.

              Rosen, B., Schulzrinne, H., Polk, J., and A. Newton,
              "Framework for Emergency Calling using Internet
              Multimedia", draft-ietf-ecrit-framework-10 (work in
              progress), July 2009.

   [RFC5069]  Taylor, T., Tschofenig, H., Schulzrinne, H., and M.
              Shanmugam, "Security Threats and Requirements for
              Emergency Call Marking and Mapping", RFC 5069,
              January 2008.

   [RFC5222]  Hardie, T., Newton, A., Schulzrinne, H., and H.
              Tschofenig, "LoST: A Location-to-Service Translation
              Protocol", RFC 5222, August 2008.

              Marshall, R., "Requirements for a Location-by-Reference
              Mechanism", draft-ietf-geopriv-lbyr-requirements-09 (work
              in progress), November 2009.

   [RFC5031]  Schulzrinne, H., "A Uniform Resource Name (URN) for
              Emergency and Other Well-Known Services", RFC 5031,
              January 2008.

              Barnes, M., Winterbottom, J., Thomson, M., and B. Stark,
              "HTTP Enabled Location Delivery (HELD)",
              draft-ietf-geopriv-http-location-delivery-16 (work in
              progress), August 2009.

              Winterbottom, J. and M. Thomson, "Specifying Holes in LoST
              Service Boundaries", draft-ietf-ecrit-specifying-holes-01
              (work in progress), October 2008.

7.2.  Informative References

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Authors' Addresses

   Henning Schulzrinne
   Columbia University
   Department of Computer Science
   450 Computer Science Building
   New York, NY  10027

   Phone: +1 212 939 7004

   Laura Liess
   Deutsche Telekom Networks
   Deutsche Telekom Allee 7
   Darmstadt, Hessen  64295


   Hannes Tschofenig
   Nokia Siemens Networks
   Linnoitustie 6
   Espoo  02600

   Phone: +358 (50) 4871445

   Barbara Stark
   725 W Peachtree St, NE
   Atlanta, GA  30308

   Phone: +1 404 499 7026

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   Andres Kuett


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