ECRIT H. Schulzrinne
Internet-Draft Columbia University
Intended status: Informational L. Liess
Expires: February 27, 2008 Deutsche Telekom
H. Tschofenig
Nokia Siemens Networks
August 26, 2007
Location Hiding: Problem Statement and Requirements
draft-schulzrinne-ecrit-location-hiding-requirements-01.txt
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Abstract
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 in order to determine the correct dial
string and information to route the call to a Public Safety Answering
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Point (PSAP). For determining the PSAP Uniform Resource Identifier
(URI) the usage of the Location-to-Service Translation (LoST)
Protocol is envisioned.
This document explores the architectural impact for the IETF
emergency services architecture 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.
This document provides a problem statement and lists requirements.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Emergency Services Architecture . . . . . . . . . . . . . . 3
1.2. Location Hiding . . . . . . . . . . . . . . . . . . . . . . 3
1.3. Location by Reference . . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. Requirements . . . . . . . . . . . . . . . . . . . . . . . . . 4
3.1. High-Level Requirements . . . . . . . . . . . . . . . . . . 4
3.2. Detailed Requirements . . . . . . . . . . . . . . . . . . . 5
3.3. Desirable Properties . . . . . . . . . . . . . . . . . . . 6
4. Security Considerations . . . . . . . . . . . . . . . . . . . . 6
5. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . 6
6. References . . . . . . . . . . . . . . . . . . . . . . . . . . 7
6.1. Normative References . . . . . . . . . . . . . . . . . . . 7
6.2. Informative References . . . . . . . . . . . . . . . . . . 7
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 8
Intellectual Property and Copyright Statements . . . . . . . . . . 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 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 [I-D.ietf-ecrit-lost] allows to
determine the PSAP Uniform Resource Identifier (URI) for a specific
geographical location together with a service URI
[I-D.ietf-ecrit-service-urn]. 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 [I-D.ietf-ecrit-framework].
For emergency services, location information is needed for two
different purposes, namely for routing an emergency call to the PSAP
that is responsible for a specific geographical region (and also for
requested service, such as police or ambulance) and for dispatch of
the emergency personell to the scene of an accident, crime or other
types of incidents.
It is very important to note that this document only discusses
location hiding in the context of location information that is need
for call routing. ISPs have no interest or even legal basis for
hiding location information from emergency services personnel.
1.2. Location Hiding
In some cases, Internet Access Providers (IAPs) and/or the Internet
Service Providers (ISPs) are afraid 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.
Hence, they do not to disclose precise location information (at the
quality suitable for dispatch emergency personell by the PSAP
operator) or not to disclose any location information.
In some other cases IAPs and ISPs may not want to make location
information available without the ability to charge for it. This is
a pure business decision.
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
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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
[I-D.marshall-geopriv-lbyr-requirements].
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. This requires a trust relationship between the PSAP and
the ISP.
Unfortunately, a location reference is not compatible with LoST, as
LoST requires an information value rather than a reference. Also,
LoST servers may be operated by the VSP, which may not have a trust
relationship with the ISP.
This document explores the architectural impact for the current
architecture and lists requirements.
2. Terminology
The keywords "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], 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
This section presents requirements.
3.1. High-Level Requirements
Req-A: There SHOULD be a way an access network can withhold detailed
location information from any entity it wishes to, and
specifically, the endpoint, and a VSP.
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Req-B: The ISP/IAP MUST support the ability of the endpoint or the
VSP to route emergency calls.
Req-C: 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.
Req-D: Precise location information must be conveyed (either LbyR or
LbyV) to the PSAP.
3.2. Detailed Requirements
Req-1: A business or trust relationship between an ISP and a VSP
MUST NOT be assumed.
Req-2: A solution MUST consider deployment scenarios where a VSP is
outside the jurisdiction of the PSAP.
Req-3: The solution MUST offer automated discovery of servers and
other behavior, i.e., no manual configuration can be assumed.
Req-4: 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-5: The solution SHOULD work for non-SIP entities, without the
ISP/IAP having to support these protocols.
Req-6: The solution MUST work if PSAP boundaries have holes.
Req-7: The solution MUST NOT assume the existence of Emergency
Service Routing Proxies (ESRPs) per country, state and city.
Req-8: The solution MUST consider that service boundaries for
different emergency services may differ, but they overlap at the
location of the caller.
Req-9: UAs MUST NOT have to deduce the desired behavior by trial-
and-error operations, such as LbyR resolutions, fail, as failures
add latency during call setup. The solution MUST NOT
significantly increase call setup latency.
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Req-10: The solution MUST allow the end host to determine PSAP/ESRP
URLs prior to the call, for all emergency services.
Req-11: The solution MUST allow UAs to discover at least their dial
string ahead of the emergency call.
Req-12: The solution MUST have minimal impact on UAs.
Req-13: The solution MUST NOT interfere with the use of LoST for
non-emergency services.
Req-14: Deleted
Req-15: Calls may reach a PSTN gateway, rather than the PSAP
directly.
3.3. Desirable Properties
o 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.
o The solution SHOULD minimize the impact on LoST, SIP conveyance
[I-D.ietf-sip-location-conveyance] and DHCP.
o The solution SHOULD NOT rely on DHCP for LoST configuration, as
the information in the DHCP server provided by the ISP may not
reach the UA, due to NATs.
4. 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
document.
5. Acknowledgments
We would like to thank the following ECRIT working group members (in
no particular order) for their contributions:
o Andrew Newton (andy@hxr.us)
o James Winterbottom (James.Winterbottom@andrew.com)
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o Brian Rosen (br@brianrosen.net)
o Richard Barnes (rbarnes@bbn.com)
o Marc Linsner (mlinsner@cisco.com)
o Barbara Stark (Barbara.Stark@BellSouth.com)
o Andres Kuett (andres.kytt@skype.net)
o Ted Hardie (hardie@qualcomm.com)
6. References
6.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", March 1997.
6.2. Informative References
[I-D.ietf-geopriv-l7-lcp-ps]
Tschofenig, H. and H. Schulzrinne, "GEOPRIV Layer 7
Location Configuration Protocol; Problem Statement and
Requirements", draft-ietf-geopriv-l7-lcp-ps-03 (work in
progress), July 2007.
[I-D.ietf-sip-location-conveyance]
Polk, J. and B. Rosen, "Location Conveyance for the
Session Initiation Protocol",
draft-ietf-sip-location-conveyance-08 (work in progress),
July 2007.
[I-D.ietf-ecrit-framework]
Rosen, B., "Framework for Emergency Calling using Internet
Multimedia", draft-ietf-ecrit-framework-02 (work in
progress), July 2007.
[I-D.ietf-ecrit-lost]
Hardie, T., "LoST: A Location-to-Service Translation
Protocol", draft-ietf-ecrit-lost-06 (work in progress),
August 2007.
[I-D.marshall-geopriv-lbyr-requirements]
Marshall, R., "Requirements for a Location-by-Reference
Mechanism used in Location Configuration and Conveyance",
draft-marshall-geopriv-lbyr-requirements-02 (work in
progress), July 2007.
[I-D.ietf-ecrit-service-urn]
Schulzrinne, H., "A Uniform Resource Name (URN) for
Emergency and Other Well-Known Services",
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draft-ietf-ecrit-service-urn-07 (work in progress),
August 2007.
[I-D.ietf-geopriv-http-location-delivery]
Barnes, M., "HTTP Enabled Location Delivery (HELD)",
draft-ietf-geopriv-http-location-delivery-01 (work in
progress), July 2007.
Authors' Addresses
Henning Schulzrinne
Columbia University
Department of Computer Science
450 Computer Science Building
New York, NY 10027
US
Phone: +1 212 939 7004
Email: hgs+ecrit@cs.columbia.edu
URI: http://www.cs.columbia.edu
Laura Liess
Deutsche Telekom Networks
Deutsche Telekom Allee 7
Darmstadt, Hessen 64295
Germany
Phone:
Email: Laura.Liess@t-systems.com
URI: http://www.telekom.de
Hannes Tschofenig
Nokia Siemens Networks
Otto-Hahn-Ring 6
Munich, Bavaria 81739
Germany
Email: Hannes.Tschofenig@nsn.com
URI: http://www.tschofenig.com
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