One document matched: draft-marshall-geopriv-lbyr-requirements-01.txt
Differences from draft-marshall-geopriv-lbyr-requirements-00.txt
GeoPriv R. Marshall, Ed.
Internet-Draft TCS
Intended status: Standards Track March 4, 2007
Expires: September 5, 2007
Requirements for a Location-by-Reference Mechanism used in Location
Configuration and Conveyance
draft-marshall-geopriv-lbyr-requirements-01
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Copyright (C) The IETF Trust (2007).
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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 . . . . . . . . . . . . . . . . . . . 5
3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 6
3.1. Terms . . . . . . . . . . . . . . . . . . . . . . . . . . 6
4. Examples of various LRI Model . . . . . . . . . . . . . . . . 8
5. High-Level Requirements . . . . . . . . . . . . . . . . . . . 12
6. Security Considerations . . . . . . . . . . . . . . . . . . . 14
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 15
8. Contributors . . . . . . . . . . . . . . . . . . . . . . . . . 16
9. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 17
10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 18
10.1. Normative References . . . . . . . . . . . . . . . . . . . 18
10.2. Informative References . . . . . . . . . . . . . . . . . . 18
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 20
Intellectual Property and Copyright Statements . . . . . . . . . . 21
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1. Introduction
This document identifies the individual requirements underlying how a
Location-by-Reference (LbyR) mechanism is to be used over the
Internet, applied to either a Conveyance protocol or to a
Configuration protocol. The LbyR approach is in contrast to the
Location-by-Value (LbyV) model, which uses a "location object" (e.g.,
PIDF-LO) exclusively. Examples using the Location-by-Value method
are beyond the scope of this document.
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.
[http://www.ietf.org/internet-drafts/
draft-ietf-sip-location-conveyance-07.txt] For an application of LbyR
Conveyance, we choose to use the example of SIP signaling within an
emergency services context, though we also talk about LbyR in a more
general sense. In this case, a SIP user agent, or SIP proxy server
acting on behalf of a user agent, to another user agent via the SIP
protocol [RFC3261]. In place of the actual value for a "Location", a
Location Reference ID (LRI) is used to represent the "value" of the
location, stored in some Internet-connected host, which we call a
location server.
For a LbyR Configuration protocol mechanism, even for the emergency
service context mentioned, many different protocol choices exist.
These include DHCP, LLDP-MED, and several Layer 7 protocols being
considered for standardization. Regardless of the variety of
choices, the general concept of how LbyR is used for configuration,
is not specific to any particular protocol choice.
A Location which is referenced can be either Geographic location [RFC
3693] (e.g., lat/lon), or a Civic location (e.g., street address).
We reintroduce a few basic entities [RFC3693] into the Location-by-
Reference discussion. These include a "target" as the entity whose
location is being transmitted, (e.g., a user agent's (UA) location.
A "using protocol", defined as how a "location server" transmits a
"location reference identifier" to a "location recipient". Privacy
of a target's location, with repect to identity is important to
protect, hence all examples shown assume that any user identity
associated with the target is not included with location.
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Location can be pushed from one host to another, as part of a
signaling protocol, in order to be used for location-based routing
(or other purposes, outside the scope here), or it can alternatively
be queried via a client request to a server which provides location
[ref. drafft-sip-conveyance- TBD]. In the case of LbyR Conveyance,
the actual location (i.e., location object) never gets pushed along,
but is replaced by a Location Reference Identifier. In the case of a
client which queries a server for location, the query is either to
obtain a Location Reference Identifier, or to obtain an actual
Location (e.g., location object) based the input of an LRI in the
query.
The draft-sip-conveyance- document details how SIP proxies treat LbyV
or LbyR scenarios for conveying location via the SIP protocol.
Whereas location objects are readily consumable by the hosts that
using protocols deliver to, a Location Reference ID must first go
through a dereference step in order to be useful.
In our SIP example, for LbyR, instead of having a content identifier
(cid:) pointing to a location object within a SIP body, the LRI is
carried in the Geolocation header of a SIP message which is used to
get a location via a dereference.
A common example use case is the "emergency services call" case,
where an request for emergency services is initiated over the
Internet via the SIP protocol (i.e., a '9-1-1' or '1-1-2' call). In
order to route the call to the appropriate PSAP, the UA client
location is required.
This document uses as a baseline scenario, the example of an
emergency call, where an request for emergency services is initiated
over the Internet using the SIP protocol (e.g., a '9-1-1' or '1-1-2'
call). In order to route the call to the appropriate PSAP, since
PSAPs are divided regionally, the UA client location is required.
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" in this document are to be interpreted as described in
RFC 2119 [RFC2119].
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3. Terminology
3.1. Terms
Several of the terms presented below are based on RFC3693, and in
some cases, extended to include additional language to support the
Location-by-Reference model.
Dereference Protocol: A protocol which is used to query a Location
server based on an LRI as input.
Location Reference Identifier (LRI): An identifier (e.g., URI) which
is a pointer to a target's location record on a remote host (e.g.,
location server), and is used by a dereferencing protocol for
retrieval of that specific location.
Location Server (LS): A network host which is designed to store
location and to provide that same location to appropriate location
client requests. May also be referred to as a Location
Information Server (LIS).
LoST Mapping Server (LMS): A network host which provides a URI
response based on input of a location and service identifier [ref.
draft-ecrit-lost-].
Using Protocol: A protocol that carries a Location Object or an
Location Reference Identifier (i.e., LRI).
Target: A person or other entity whose location is communicated by a
Geopriv Location Object.
Location Recipient (LR): The entity that receives location
information. It may have asked for this location explicitly (by
sending a query containing an LRI to a location server), or it may
receive this location asynchronously. Also may be referred to as
a Dereference client within this document, in the context of the
Location-by-Reference model.
Location Server (LS): The entity to which a LG publishes location
objects, the recipient of queries from location receivers, and the
entity that applies rules designed by the rule maker. Also may be
referred to as a Dereference server within this document, in the
context of the Location-by-Reference model.
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.
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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.
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. Examples of various LRI Model
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), P (Proxy), LS (Location Server), and a UA at the PSAP
(UA2).
This section outlines which entities will be considered in the
referernce/dereference scenarios discussed.
<t>
<figure anchor="LRI Indirection" title="LRI query/response - where
Target = Location Recipient.">
<artwork><![CDATA[
+--------+ +--------+
| Target |<---------response w/LO-------| |
| == | | LS |
| LR |-----------query w/LRI------->| |
+--------+ +--------+
Figure 1: Framework for referencing or de-referencing location in a
SIP session.
Above figure shows simplest LRI interaction, when target happens to
also be the Location Recipient [ref. RFC3693 terms]
+--------+ +--------+ +--------+
| | | | | |
| Target |<----------acquire LO---------| LS |<--deref--| LR |
| | | | LRI | |
+--------+ +--------+ +--------+
| |
+----------------convey LRI--------------------------------->+
Figure 2: Setup showing LRI indirection.
The above interaction reduces to two basic interactions: 1. Location
provision from LS/LIS to target by reference (LRI). 2. Location
indirection by the LS/LIS, at the request of the Target. Location
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updates, are possible in either case.
+--------+ +--------+ +--------+
| | | | | |-------LO------+
| Target |<........>| LG |--LI/LO-->| LS/DS | |
| | | | | |<---LRI---+ |
+--------+ +--------+ +--------+ | |
| |
| v
+--------+ +--------+ +--------+
| | | | | |
| LRG |---LRI--->| LT |--LRI-->| LR/DC |
| | | | | |
+--------+ +--------+ +--------+
Figure 3: General Setup - LG interaction.
Definitions: Target, LG, LR, LI, LO as in RFC 3693. LRG = Location
Reference Generator (creates reference) LT = Location Transmitter
(one party to Conveyance Protocol) DS/DC = Dereference Server /
Client Protocols: Dereference Protocol is between DS and DC
Conveyance Protocol is between LT and LR
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+--------+
| |
+--------------| LS |-----------------------------------+
| | | |
| + -------+ |
LCP ^ LDP
| LDP |
V V V
+--------+ +--------+ +--------+ +--------+
| | | | | | | |
| UA1 |--------->| P1 |--------->| P2 |--------->| UA2 |
| | | | | | | |
+--------+ +--------+ +--------+ +--------+
^
LMP
V
+--------+
| |
| LMS |
| |
+--------+
Figure 4: Example of a SIP call.
Definitions: LS = Location Server (as in RFC 3693) LCP = Location
Configuration Protocol LDP = Location Dereference Protocol LMP =
Location Mapping Protocol Sequence: 1. UA1 acquires LRI from its LS
(acting as LRG) 2. UA1 sends an INVITE to a service URN via P1 3.
P1 dereferences the LRI and uses it to get a URI from the LMS 4. UA2
may also wish to dereference the LRI, e.g., to get the current
location of UA1.
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.
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:
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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 Reference Identifier as a URI: The dereferencing
protocol MUST support an LRI in URI form, and may support other
non-URI forms.
Rq2. Dereference Protocol Confidentiality: The dereferencing
protocol MUST support mechanisms for encrypting messages sent
between client (Location recipient) and server (Location server).
Rq3. Dereference Protocol Transparancy: The dereferencing protocol
MUST support the exchange of messages without encryption (i.e., in
plaintext).
Motivation: In the case where encrypted message exchange is
unsuccessful, there must be a way to try to dereference a location
reference identifier with less restriction (e..g., in the
emergency service case, where every call always needs answered).
Rq4. Location Reference Expiry: The dereference protocol MUST
support specification of a finite period of validity for the LRI.
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.
Rq5. Dereference Protocol Transport: The de-reference protocol MUST
support TCP/IP and MAY support UDP/IP.
Motivation: Practical, near-term deployment issues may make TCP/IP
implementations unachievable.
Rq6''. Dereference 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.
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Rq7. Location Privacy: The dereference protocol MUST support the
application of privacy rules to the dissemination of a requested
location object.
Rq8. Dereferenced 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.
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6. Security Considerations
Considerations for security to a Location-by-Reference model for the
dereference protocol, include, 1. Privacy Privacy of the LRI itself
Privacy of the dereferenced location object 2. Expiry Expiry of the
LRI. Expiry of the dereferenced location object. 3. Theft Theft of
a LRI. Theft of a dereferenced location object. 4. Replay/Reuse
Replay of a stolen LRI to perform a dereference operation. Reuse
using the dereference location object. 5. Impact of the two forms of
location reference. Location provision from LIS by reference.
Location indirection by the LIS, at the request of the Target. May
also reference security considerations found within document
[I-D.ietf-geopriv-l7-lcp-ps].
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7. IANA Considerations
This document does not require actions by the IANA.
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8. Contributors
Andrew Newton, James Polk, Martin Thompson, Richard Barnes, Barbara
Stark, James Winterbottom, Hannes Tschofenig
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
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
10.2. Informative References
[I-D.hardie-ecrit-lost]
Hardie, T., "LoST: A Location-to-Service Translation
Protocol", draft-hardie-ecrit-lost-00 (work in progress),
March 2006.
[I-D.ietf-ecrit-requirements]
Schulzrinne, H. and R. Marshall, "Requirements for
Emergency Context Resolution with Internet Technologies",
draft-ietf-ecrit-requirements-12 (work in progress),
August 2006.
[I-D.ietf-ecrit-security-threats]
Taylor, T., "Security Threats and Requirements for
Emergency Call Marking and Mapping",
draft-ietf-ecrit-security-threats-03 (work in progress),
July 2006.
[I-D.ietf-geopriv-dhcp-civil]
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.
[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-00 (work in
progress), January 2007.
[I-D.ietf-sipping-toip]
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.
[RFC3261] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston,
A., Peterson, J., Sparks, R., Handley, M., and E.
Schooler, "SIP: Session Initiation Protocol", RFC 3261,
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June 2002.
[RFC3351] 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.
[RFC3693] Cuellar, J., Morris, J., Mulligan, D., Peterson, J., and
J. Polk, "Geopriv Requirements", RFC 3693, February 2004.
[RFC3825] Polk, J., Schnizlein, J., and M. Linsner, "Dynamic Host
Configuration Protocol Option for Coordinate-based
Location Configuration Information", RFC 3825, July 2004.
[RFC3860] Peterson, J., "Common Profile for Instant Messaging
(CPIM)", RFC 3860, August 2004.
[RFC3966] Schulzrinne, H., "The tel URI for Telephone Numbers",
RFC 3966, December 2004.
[RFC4103] Hellstrom, G. and P. Jones, "RTP Payload for Text
Conversation", RFC 4103, June 2005.
[RFC4119] Peterson, J., "A Presence-based GEOPRIV Location Object
Format", RFC 4119, December 2005.
[RFC4412] Schulzrinne, H. and J. Polk, "Communications Resource
Priority for the Session Initiation Protocol (SIP)",
RFC 4412, February 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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Full Copyright Statement
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