One document matched: draft-marshall-geopriv-lbyr-requirements-00.txt
GeoPriv R. Marshall, Ed.
Internet-Draft TCS
Expires: August 9, 2007 February 5, 2007
Requirements for a Location-by-Reference Mechanism used in Location
Configuration and Conveyance
draft-marshall-geopriv-lbyr-requirements-00
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Abstract
This document defines terminology and enumerates requirements for a
location-by-reference approach to location configuration and
conveyance interactions useful for emergency call routing for voice-
over-IP (VoIP) and general Internet multimedia systems, where
Internet protocols are used end-to-end.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Requirements Terminology . . . . . . . . . . . . . . . . . . . 4
3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 5
3.1. Terms . . . . . . . . . . . . . . . . . . . . . . . . . . 5
3.2. Actors . . . . . . . . . . . . . . . . . . . . . . . . . . 5
3.3. Location . . . . . . . . . . . . . . . . . . . . . . . . . 5
4. Basic Actors . . . . . . . . . . . . . . . . . . . . . . . . . 7
5. High-Level Requirements . . . . . . . . . . . . . . . . . . . 9
6. Security Considerations . . . . . . . . . . . . . . . . . . . 11
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 12
8. Contributors . . . . . . . . . . . . . . . . . . . . . . . . . 13
9. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 14
10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 15
10.1. Normative References . . . . . . . . . . . . . . . . . . . 15
10.2. Informative References . . . . . . . . . . . . . . . . . . 15
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 17
Intellectual Property and Copyright Statements . . . . . . . . . . 18
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1. Introduction
A mechanism for either (or both) location configuration and location
conveyance may rely on either a location-by-value approach,
containing and transporting location information along every leg of
the signaling path, or alternatively, a different approach, using a
location-by-reference technique, which may be used to reference a
location with some identifier, and to de-reference the location when
needed for a location-based decision.
This document uses as a baseline condition, the primary example of an
emergency call, which includes a request for emergency services via a
SIP-enabled end device, connecting through the Internet to an IP-
enabled PSAP (Public Service Answering Point).
We first define terminology in Section 3. The document then outlines
baseline requirements (Section 5), around the referencing and
dereferencing of location via some location identifier in lieu of the
emergency caller's actual location.
Identification of the caller, as associated information to location
or location reference, either in conveyance or configuration, is out
of scope in this document.
Location-by-reference is a mechanism which is in use in VoIP 9-1-1
systems at the time of this writing, and justified based on the
requirements listed in this document.
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2. Requirements Terminology
In this document, the key words "MUST", "MUST NOT", "REQUIRED",
"SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY",
and "OPTIONAL" are to be interpreted as described in RFC 2119 [1],
with the qualification that unless otherwise stated these words apply
to the design of the location-by-reference mechanism, and not its
implementation or application.
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3. Terminology
3.1. Terms
Location Reference Identifier (LRI): An identifier (could be of the
form of any URI) which is designed to represent a location object.
Location Server (LS): A network host which is designed to store
location and to provide that same location to appropriate location
client requests.
Location-to Mapping Server (LMS): A network host which provides a
URI mapping service based on an input location and service
identifier.
Call Server/Proxy (CS/P): A network host which plays the role of a
SIP Proxy.
3.2. Actors
de-reference protocol client: The term to describe the entity
requesting a Location Object in exchange for a Location Reference
Identifier provided.
de-reference protocol server: The term to describe the entity
providing a Location Object as an output based on a Location
Reference Identifier input.
3.3. Location
Location: A geographic identification assigned to a region or
feature based on a specific coordinate system, or by other precise
information such as a street number and name. It can be either a
civic or geographic location.
Civic location: A described location based on some reference system,
such a jurisdictions or postal delivery. A street address is a
common example.
Geographic location: A reference to a point which is able to be
located as described by a set of defined coordinates within a
geographic coordinate system, such as latitude and longitude
within the WGS-84 datum. For example, 2-D geographic location is
defined as an (x,y) coordinate value pair according to the
distance north or south of the equator and east or west of the
prime meridian.
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Location-by-Value: The mechanism of representing location either in
conveyance protocols or configuration protocols as fully
specified, (i.e., including the actual location value itself).
Location-by-Reference: The mechanism of representing location either
in conveyance protocols or configuration protocols as an
identifier which refers to a fully specified location, (i.e.,
including a pointer to the actual location value itself).
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4. Basic Actors
To support the referencing or de-referencing of a location, it is
appropriate to describe a diagram consisting of network elements
around which this might be done. These elements include, the UA
(User Agent), CS/P (Call Server/Proxy), a LS (Location Server), and a
PSAP UA.
This section outlines which entities will be considered in the
referernce de-reference scenarios discussed.
+-------+
| | |-------------------------------
| LMS |---|---------------- \
| | |--- \ \
+-------+ \ \ \
\ \ \
\ \ \
\ \ \
+-------+ +-------+ +-------+ +-------+
| | | | | | | |
| UA1 |------| P1 |------| P2 |------| UA2 |
| | | | | | | |
+-------+ +-------+ +-------+ +-------+
| / / /
| / / /
| / / /
+-------+ / / /
| | |-- / /
| LS |---|---------------- /
| | |------------------------------
+-------+
Figure 1: Framework for referencing or de-referencing location in a
SIP session.
Figure 1 shows the interaction between the entities involved in the
call, as to how location is referenced and subsequently de-
referenced. The figure proposes that location reference is conveyed
from the endpoint-to-endpoint via each middlebox (SIP Proxy), and
undergoes a de-referencing operation at each step. The figure also
depicts a LMS (Location-to-Mapping Server) element which is used to
determine the next target destination, based on the de-referenced
location.
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At the PSAP, the end device also receives a location reference, (as
indicated in this figure), and executes a de-reference quiery.
Various potential interactions between the entities depicted in
Figure 1 are described below:
1. Location information might be generated by the end host itself,
in which case it may then request reference identifier based on
the location that it generated and provided to the LS.
2. Alternately, location information might be either generated,
provisioned, or stored by the LS (Location Server), and
represented to the end device as a location reference, via a
location configuration protocol (e.g., using DHCP or some L7LCP
(Layer 7 Location Configuration Protocol).
3. The location reference is only useful to mask the actual
location, but must be de-referenced in order to be useful for
location-based routing. Once the location is de-referenced at
the LS and returned to the requestor, it can then be used as
input to a location-to-mapping service (e.g., LoST). The mapping
server returns a URI which can be used to establish the signaling
to the next target destination. This returned target identifier
may be the URI of the next SIP Proxy (or any other element along
the routing path), or may be the URI of the appropriate IP-based
PSAP.
4. The PSAP, consistent with the figure, may choose to de-reference
the location identifier, once it is received, in order to view
the location, and to request subsequent location-based actions.
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5. High-Level Requirements
Below, we summarize high-level design requirements needed for a
location-by-reference mechanism.
Rq1. Location Conveyance By Value (LbyV): The conveyance protocol
MUST support the conveyance of location information in its fully-
contained form, i.e., a PIDF-LO. (I know this isn't a requirement
for LbyR, but is included for balance.)
Rq2. Location Conveyance By Reference (LbyR): The conveyance
protocol MAY support the conveyance of a location information
reference identifier, in the form of 'any URI', which can be used
to de-reference the location into its fully-contained form, (e.g.,
a PIDF-LO).
Rq3. Location Conveyance Duality: The location conveyance protocol
MAY support both location value and location reference identifier
in the same message.
Rq4. Private Location Reference Id.: The dereferencing protocol
MUST support the encryption of a location reference identifier.
Rq5. Public Location Reference Id.: The dereferencing protocol MAY
convey a location reference identifier in plaintext.
Rq6. Location Reference Expiry: There MUST exist, a location
reference uri format that includes a specified, finite period of
validity.
Motivation: Location references are not intended to represent a
location forever, and the identifier eventually may need to be
recycled, or may be subject to a specific window of validity,
after which the location reference fails to yield a location, or
the location is determined to be kept confidential. An expiry
timer for a location reference ensures that the location reference
becomes invalid based on configuration.
Rq7. de-reference Protocol Transport: The de-reference protocol MUST
support TCP/IP and MAY support UDP/IP.
Rq8. LRI Distribution: The location reference standard MUST allow
construction of location references that can be distributed to and
de-referenced by multiple parties, and MAY support references that
are restricted to a single de-referencer"
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Rq9''. de-reference Protocol Authentication: The dereferencing
protocol MUST support both client-side and server-side
authentication.
Motivation: It is reasonable to expect implementations of
authentication to vary. Some implementations may choose to
support both client-side and server-side authentication, might
support one only, or may support neither.
Rq10. Location Privacy: The de-reference protocol MUST support the
application of privacy rules to the dissemination of a requested
location object. The entity that receives requests through the
de-reference protocol MUST obey all privacy rules that apply to a
requested location object.
Rq11. De-referenced PIDF-LO Result: The dereferencing of an LRI
MUST result in a well-formed PIDF-LO.
Motivation: This is in order to ensure adequate privacy rules can
be adhered to, since the PIDF-LO format comprises the necessary
structures to maintain location privacy.
Rq12. Expiry of de-referenced Location: The de-referenced location,
in PIDF-LO format, MUST include a configurable expiry timer to
signal the point after which the PIDF-LO contained location is no
longer considered usable.
Motivation: Once the location is de-referenced, it would be
difficult to keep it from being passed around further 'as a plain
old PIDF-LO', hence a timer expiry is specified. (This technique
does not prevent would-be 'black-hats' from reusing the PIDF-LO,
but provides some additional functionality within a proper use
context.
Rq13. De-reference Protocol Selection: Location by reference
systems MUST support at least one, and MAY support multiple
dereferencing protocols.
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6. Security Considerations
Threats and security requirements are discussed in a separate
document document [11].
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7. IANA Considerations
This document does not require actions by the IANA.
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8. Contributors
[TBD]
The contributors can be reached at:
Name user@example.com
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9. Acknowledgments
[TBD]
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10. References
10.1. Normative References
[1] Bradner, S., "Key words for use in RFCs to Indicate Requirement
Levels", BCP 14, RFC 2119, March 1997.
10.2. Informative References
[2] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston, A.,
Peterson, J., Sparks, R., Handley, M., and E. Schooler, "SIP:
Session Initiation Protocol", RFC 3261, June 2002.
[3] Charlton, N., Gasson, M., Gybels, G., Spanner, M., and A. van
Wijk, "User Requirements for the Session Initiation Protocol
(SIP) in Support of Deaf, Hard of Hearing and Speech-impaired
Individuals", RFC 3351, August 2002.
[4] Cuellar, J., Morris, J., Mulligan, D., Peterson, J., and J.
Polk, "Geopriv Requirements", RFC 3693, February 2004.
[5] Polk, J., Schnizlein, J., and M. Linsner, "Dynamic Host
Configuration Protocol Option for Coordinate-based Location
Configuration Information", RFC 3825, July 2004.
[6] Peterson, J., "Common Profile for Instant Messaging (CPIM)",
RFC 3860, August 2004.
[7] Schulzrinne, H., "The tel URI for Telephone Numbers", RFC 3966,
December 2004.
[8] Hellstrom, G. and P. Jones, "RTP Payload for Text
Conversation", RFC 4103, June 2005.
[9] Peterson, J., "A Presence-based GEOPRIV Location Object
Format", RFC 4119, December 2005.
[10] Schulzrinne, H. and J. Polk, "Communications Resource Priority
for the Session Initiation Protocol (SIP)", RFC 4412,
February 2006.
[11] Taylor, T., "Security Threats and Requirements for Emergency
Call Marking and Mapping", draft-ietf-ecrit-security-threats-03
(work in progress), July 2006.
[12] Schulzrinne, H. and R. Marshall, "Requirements for Emergency
Context Resolution with Internet Technologies",
draft-ietf-ecrit-requirements-12 (work in progress),
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August 2006.
[13] Hardie, T., "LoST: A Location-to-Service Translation Protocol",
draft-hardie-ecrit-lost-00 (work in progress), March 2006.
[14] Schulzrinne, H., "Dynamic Host Configuration Protocol (DHCPv4
and DHCPv6) Option for Civic Addresses Configuration
Information", draft-ietf-geopriv-dhcp-civil-09 (work in
progress), January 2006.
[15] Wijk, A. and G. Gybels, "Framework for real-time text over IP
using the Session Initiation Protocol (SIP)",
draft-ietf-sipping-toip-07 (work in progress), August 2006.
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Author's Address
Roger Marshall (editor)
TeleCommunication Systems, Inc.
2401 Elliott Avenue
2nd Floor
Seattle, WA 98121
US
Phone: +1 206 792 2424
Email: rmarshall@telecomsys.com
URI: http://www.telecomsys.com
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