wdiff draft-polk-sipping-location-requirements-00.txt draft-polk-sipping-location-requirements-01.txt

Internet Engineering Task Force James M. Polk
Internet Draft Cisco Systems
Expiration: Dec 23rd, April 27th, 2003 Brian Rosen
File: draft-polk-sipping-location-requirements-00.txt draft-polk-sipping-location-requirements-01.txt Marconi

Session Initiation Protocol Location Requirements

June 23rd, Conveyance

October 27th, 2003

Status of this Memo

This document is an Internet-Draft and is in full conformance
with all provisions of Section 10 of RFC2026.

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Abstract

This document presents the framework and requirements for an
extension to the Session Initiation Protocol (SIP) [1] for
conveyance of user location information from one a Session Initiation
Protocol (SIP)
User Agent user agent to another SIP User Agent. The idea that in some entity. We consider cases
the UAC's
where location could affect proper information is conveyed from end to end, as well as
cases where message routing by intermediaries is influenced by the
location of the SIP message
is explored as well. session initiator.

Table of Contents

1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1 Conventions . . . . . . . . . . . . . . . . . . . . . . . 3
2. In the Body or in a Header . . . . .
1.2 Changes from -00 . . . . . . . . . . . . 3
3. Scope of Location in a Message Body . . . . . . . . 3
2. In the Body or in a Header . . . . . 4
4. Scope of Location in a Message Header . . . . . . . . . . . . 4
4.1 3
3. Scope of Location in a Single Header . . Message Body . . . . . . . . . . . . . 4
4.2
4. Requirements for UA-to-UA Location in Separate Message Headers . . Conveyance . . . . . . . . 5 4
5. Requirements for UA-to-UA UA-to-Proxy Server Location Conveyance . . . . . . . . 5
6. Additional Requirements for Proxy-Routed Location Conveyance Emergency Calls . . . . . . . 6
7. Security Considerations . . 5
7. Current Known Open issues . . . . . . . . . . . . . . . . . 7 . 6
8. IANA Security Considerations . . . . . . . . . . . . . . . . . . . . 7 6
9. Acknowledgements . . IANA Considerations . . . . . . . . . . . . . . . . . . . . 8 7
10. References Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 7
11. References . . . 8
11. Author Information . . . . . . . . . . . . . . . . . . . . . 8 . 7
12. Full Copyright Statement Author Information . . . . . . . . . . . . . . . . . . . . . 8

1. Introduction

This document presents the framework and requirements for an
extension to the Session Initiation Protocol (SIP) [1] for
conveyance of user location information object described by [7] from one Session Initiation Protocol (SIP)
a SIP User Agent to another SIP User Agent.

While reasonable people will initially lean strongly towards
having any location conveyance entity.

There are several situations in the message body only (where
location confidentiality can which it is appropriate for SIP to
be maintained), this used to convey Location Information (LI) from one SIP entity to
another. This document
examines usage cases where intermediaries must act on the specifies requirements when a SIP UAC knows
its location information in order by some means not specified herein, and needs to determine where the session gets
routed. inform
another SIP entity. One such example is to reach your nearest pizza
parlor. A chain of this pizza parlors may have a single well known uri
(sip:pizzaparlor.com), that is US e911-type emergency
sessions (voice or instant messaging). With this in mind, both
instances will be looked at here forwarded to determine if the requirements
are in fact different enough closest franchise by
the pizzaparlor.com proxy server. The receiving franchise UAS uses
the location information of the UAC to necessitate two or more
solutions.

To be clear, schedule your delivery.

Another important example is emergency calling. A call to
sip:sos@example.com is an emergency call as in [3]. The example.com
proxy server must route the two cases that need call to be looked at are the
following:

1. one involving a user correct emergency response
center (ERC) determined by the location of a User Agent wanting to transmit
his/her the caller. At the ERC,
the UAS must determine the correct police/fire/ambulance/...
service, which is also based on your location. In many
jurisdictions, accurate location to another user information is a required component
of a user agent for
whatever reason (I want call to tell an emergency center.

A third example is a direction service, which might give you where I am); and

2. verbal
directions to a venue from your present position. This is a second case involving
where only the UAC including its location in
order to allow an appropriate Emergency Response Center
(ERC) destination UAS needs to be contacted, such as a US e911 Public Safety
Answering Point (because that User Agent has signaled for
help); receive the location
information.

This document does not discuss how the UAC discovers or is
configured with its Location location (either coordinate based or civil
based). That work is being accomplished in It also does not discuss the Geopriv Working
Group. contents of the Location
Object (LO). It does specify the requirements for the "using
protocol" in [7].

1.1 Conventions used 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 [2].

1.2 Changes from -00 Version

This is a list of the changes that have been made from the -00
version of this ID:

- Brian Rosen was brought on as a co-author

- Requirements that a location header were negatively received in
the previous version of this document. AD and chair advice was to
move all location information into a message body (and stay away
from headers)

- Added a section of "emergency call" specific requirements

- Added an Open Issues section to mention what hasn't been resolved
yet in this effort

2. In the Body or in a Header

When one user agent wants to inform another user agent where they
are, it seems reasonable to have this accomplished by placing the
location information (coordinate or civil) in an S/Mime registered
and encoded message body, and sending it as part of a SIP request or
response. No routing of the request based on the location
information is required in this case; therefore no SIP Proxies
between these two UAs need to view the location information
contained in the SIP messages.

However, it may be infeasible

Although SIP [1} does not permit a proxy server to place modify or delete
a body, there is no restriction on viewing bodies. However, S/MIME
protection implemented on bodies is only specified between UAS and
UAC and if engaged, would render the location object opaque to a
proxy server. This problem is similar to that raised in Session
Policy [8], where an intermediary may need information in
the message body of requests where/when message routing is a body,
such as IP address of
particular importance for proper session establishment with the
intended party media streams or parties (i.e. calling an ERC).

SIP message bodies are not viewed by Proxy Servers [per 1] in order codec choices to do proper route a call routing. The current proposal
properly. Requirements in front of the
SIPPING WG is [8] are applicable to use the mechanism described routing based on
location, and are incorporated in [3] to universally
signal for help. This "sos@example.com" URI these requirements by reference.

It is proposed conceivable to describe
many, if not all ERCs in create a region or country - regardless new header for location information.
However, [7] prefers S/MIME for security of the
original home domain that UA is from. This poses a particular
problem when a User Agent is signaling via a Proxy that Location Information,
and indeed S/MIME is not
within the civil boundaries of the appropriate PSAP preferable in SIP for that user.
For example, a large enterprise has a campus that spans more than protecting one PSAP jurisdiction, part of a UA initiates
message. Accordingly, these requirements specify location be
carried in a session containing body.

It is the To
header "sos@example.com". Where will use of S/MIME however, that Proxy route the SIP
Request to? The problem limits routing based on
location. Therefore, it seems appropriate to require that, where
routing is compounded if a managed domain only has
Proxies in one location dependent on location, protection of a multi site infrastructure - including the possibility of traversing state or country boundaries in cases
in which the UA is mobile.

Routing a session set-up or instant message, such as SIP MESSAGE location
information object be accomplished by other mechanisms, probably TLS
("sips:" from [4], becomes an Achilles Heel for SIP if the user agent [1]). It is
unaware of the correct ERC routing and expects the correct ERC to envisioned that S/MIME SHOULD be
selected used
when location information is not required by the SIP proxy routing machinery.. servers, and TLS
SHOULD be used when it is.

This document does not address the behavior or configuration of SIP
Proxy Servers in these cases in order to accomplish location-
sensitive routing. That is out of scope, and left for further
(complementary) efforts.

3. Scope of Location in a Message Body

If the location information is to be contained within a message
body, and either another body (SDP for example) is also to be sent
in the message, or the LO is to be protected with S/MIME, the rules
stated in section 7 of [1] regarding multipart MIME bodies MUST be
followed. The format and privacy/security rules of the location
information SHOULD be defined within the Geopriv WG.

4. Scope of Location in a Message Header

If the location information of the UAC is to be contained within the
SIP message header (verses a message body as stated above), one
design issue is whether location field(s) are contained within a
single header, or multiple headers. The following 2 subsections
cover both of these choices for discussion.

4.1 Location in a Single Header

Placing location information within a single header of a SIP message
has some big advantages:

- it is easier to specify the semantics when there are missing
fields

- it makes readability much easier when reviewing all the location
fields contained within the SIP message header ordered as if in a
list

- an order of the location fields can be specified within this
single header (ex: Datum, then Latitude, then Longitude, then
Altitude, then... or country, then state/province, then
county/region, then city, then district/borough...)

This might be important if section 7.3.1 of [1] is still true
expedited parsing in Proxies and at the destination.

There exist two documents on Location Configuration Information
within the Geopriv Working Group, one for Coordinate based location
representation (Lat, Long, Alt, Datum, etc) in [5] and one for Civil
based Location representation (country, State/province, city, etc)
in [6]. Each of these documents should be looked to as a basis for
consistency in fields present as well as scope of the fields.

If a field is missing, it probably was left out intentionally by the
UAC (either because that device didn't know what to populate a
particular field with, or a policy prevented it from being included
within that SIP message).

Any location privacy policy of a user agent within a particular
domain should allow the most precise location available be presented
as an S/MIME body in the SIP Request or response message once a
verifiable ERC is determined to be the intended destination of that
session.

4.2 Location in Separate Message Headers

Creating separate SIP headers for each location field type
(latitude, longitude, country, city, etc) does make each header
clean and concise. A grouping of these location headers should occur
for readability when viewing the location headers within a SIP
message header. And since expediting the processing of emergency
calls is important, the header placement considerations of section
7.3.1 of [1] apply to these headers when making emergency calls

Each of the message headers should be unique in name within a
location conveyance type.

In providing location information, the UAC should provide as much
information as possible within a certain type of location field
group (coordinate or civil), and not mix between groups. In other
words, a Latitude header should be used if a coordinate location is
being provided by the UAC, but is not by itself realistically
valuable information if a complete set civil location headers is
also present.

If a desire of the SIP working group is to limit the number of
headers that require IANA registration (and coding for), then
fulfilling this requirements document will add as little as 2 to
that process (1 for coordinate location and 1 for civil location),
or as many as 30+ if each location field requires a unique header.

5. Requirements for UA-to-UA Location Conveyance

The following are the requirements for UA-to-UA Location Conveyance
situations:

REQ UU1

U-U1 - MUST work with dialog-initiating SIP Requests and responses,
as well as the SIP MESSAGE method[4]

REQ UU2 - the precision of resolution of the location given by the
UAC is determined by the UAC, method[4], and SHOULD be based on who
the UAC is sending this location information to (most
likely via local policy)

REQ UU3 work with
most SIP messages.

U-U2 - UAC Location information SHOULD remain confidential in route
to the destination UA

REQ UU4

U-U3 - The privacy and security rules established within the
Geopriv Working Group which that would categorize SIP as a 'using
protocol' MUST be followed met [7]

REQ UU5 - The first sub-field must be what type of location
information it is (coordinate, civil, GPS, other)

5. Requirements for Proxy-Routed UA-to-Proxy Server Location Conveyance

The following are the requirements for Proxy-Routed UA-to-Proxy Server Location
Conveyance situations:

REQ PR1

U-PS1 - MUST work with dialog-initiating SIP Requests and
responses, as well as the SIP MESSAGE method[4]

REQ PR2 method[4], and SHOULD
work with most SIP messages.

U-PS2 - a mechanism UAC location information SHOULD be remain confidential in place
route to hide this location
header from unwanted observation while in transit to,
form, the destination, but MUST be useable by
intermediary proxy servers.

U-PS3 - The privacy and among security rules established within the
Geopriv Working Group which would categorize SIP intermediaries; but as a
'using protocol' MUST NOT be
mandatory for successful conveyance met [7]

U-PS4 - Modification or removal of location (don't
want the SIP Request to fail without this mechanism used
during emergencies)

REQ PR3 LO by proxy servers MUST NOT
be required

U-PS5 - any mechanism used to prevent unwanted observation of this
Location Header(s) CANNOT fail the SIP Request if not
understood by intermediary SIP entities or the destination
UAS

REQ PR4 - There SHOULD

U-PS6 � It MUST be a mechanism possible for the ERC a proxy server to request assert the
UAC's location information (perhaps more precise
location information) after the original SIP Request has
been received without failing the original SIP Request
(which is the most important aspect
validity of this document:
that the session is received location information provided by the proper ERC)

It UA.
Alternatively, it is possible acceptable for a Proxy to determine the proper ERC there to route
the SIP Request be a mechanism
for a proxy server to (based on the included location information
within supplied by the UAC), yet create the situation where the
ERC does not know enough assert a location information object itself.

6. Additional Requirements for personnel
response Emergency Calls

Emergency calls have requirements that are not generally important
to the emergency.

REQ PR5 - A SIP other uses for location Header field (probably the first if there in SIP:

Emergency calls presently have between 2 and 8-second call setup
times. There is ample evidence that the longer call setup end of
the range causes an order established unacceptable number of callers to abandon the headers) MUST be what
type of location information type
call before it is (coordinate,
civil, GPS, other)

REQ PR6 - SHOULD have the complete location (coordinate or civil)
contained within completed. Two-second call completion time is a single header

REQ PR7 -
goal of many existing emergency call centers. Allocating 25% of the most precise resolution (defined in [5])SHOULD
call set up for processing privacy concerns seems reasonable; 1
second would be
given by 50% of the UAC when sending its location to an ERC (or
equivalent facility)

REQ PR8 goal, which seems unacceptable; less than
0.5 second seems unachievable, therefore:

E-1 - proxies SHOULD NOT partially remove location
information, but MAY remove it in its entirety Privacy mechanisms MUST add no more than 0.5 second of call
setup time when
crossing a trust boundary to preserve implemented in present technology UAs and
Proxy Servers.

It may be acceptable for full privacy

REQ PR9 - proxies MAY add location information unknown mechanisms related to the
location of the UAC
if known (and it's user) to be tried on an initial
attempt to place a call, as long as the proxy

REQ PR10 - call attempt may be retried
without the mechanism if section 7.3.1 the first attempt fails. Abandoning
privacy in cases of [1] needs failure of the privacy mechanism might be
subject to user preference, although such a feature would be followed, within
the
Location Header SHOULD domain of a UA implementation and thus not subject to
standardization. It should be near the top noted that some jurisdictions have
laws that explicitly deny any expectation of the SIP
message header for rapid parsing purposes

REQ PR11 - mixed or additional location fields CAN privacy when
making an emergency call.

E-2 � Privacy mechanisms MUST NOT be present
providing more precise mandatory for successful
conveyance of location information, but MUST during an (sos-type) emergency call.

E-3 � The retention and retransmission policy of the ERC must be
uniquely identifiable
able to be made available to the user, and SHOULD override the
user's normal policy when local regulation governs such
retention and retransmission. As in E-2 above, requiring the
use of the ERC's retention and/or retransmission policy may
be relevant

An example subject to user preference although in most jurisdictions,
local laws specify such policies and may not be overridden by
user preference.

7. Current Known Open issues

This is a list of open issues that have not yet been addressed to
conclusion:

- Whether self signed S/MIME bodies can work in both directions in
the emergency call scenario (to and from an ERC) as in [9]. It
appears that document covers self-signed certs from the UA to ERC
direction, but it is not clear it solves communications in the
reverse direction.

- If S/MIME is chosen as a SHOULD (in general, vs. TLS), this doc
might be using the coordinate consider stipulating a special purpose Proxy (an "emergency
services" proxy) that can process location
header information (a Geopriv
LO) and adding an identifiable cube or office number field
at route the end of message directly to the coordinate header.

7. appropriate ERC.

At Issue: plain "vanilla" proxies probably won't have the
capabilities to route based on location information in the
near future, but should that timing be considered here?

8. Security Considerations

Conveyance of geo-location of a UAC is problematic for many reasons.
This document calls for that conveyance to normally be accomplished
through secure message body means (like S/MIME). S/MIME or TLS). In cases
where a session set-up is routed based on the location of the UAC
initiating the session or SIP MESSAGE, containing the location in a message
body does no good. At the same time, securing the location in a
header might fail in certain times that is detrimental to that
session (user). These times are those of emergency sessions (like to
a US e911-like service).

Although not advocated, this document therefore requires that
location conveyance in deterministic times of emergency not be bound
to being confidential universally, with an
end-to-end mechanism such as that process might fail and
could cost lives.

8. S/MIME is problematic.

9. IANA Considerations

There are no IANA considerations within this document at this time.

10. Acknowledgements

To Dave Oran for helping to shape this idea

10. idea. To Jon Peterson and
Dean Willis on guidance of the effort.

11. References - Normative

[1] J. Rosenberg, H. Schulzrinne, G. Camarillo, A. Johnston, J.
Peterson, R. Sparks, M. Handley, E. Schooler, "SIP: Session
Initiation Protocol ", RFC 3261, June 2002

[2] S. Bradner, "Key words for use in RFCs to indicate requirement
levels," RFC 2119, Mar. 1997.

[3] H. Schulzrinne, "draft-schulzrinne-sipping-sos-04.txt", Internet
Draft, Jan 03, Work in progress

[4] B. Campbell, Ed., J. Rosenberg, H. Schulzrinne, C. Huitema, D.
Gurle, "Session Initiation Protocol (SIP) Extension for Instant
Messaging" , RFC 3428, December 2002

[5] J. Polk, J. Schnizlein, M. Linsner, " draft-ietf-geopriv-dhcp-lci-
option-01.txt",
option-02.txt", Internet Draft, June Aug 2003, Work in progress

[6] H. Schulzrinne, "draft-schulzrinne-geopriv-dhcp-civil-01.txt",
Internet Draft, Feb 03, Work in progress

[7] J. Cuellar, J. Morris, D. Mulligan, J. Peterson. J. Polk, "draft-
ietf-geopriv-reqs-03.txt", Internet Draft, Mar 03, Work in
progress

11.

[8] J. Rosenberg, "Requirements for Session Policy for the Session
Initiation Protocol�, draft-ietf-sipping-session-policy-req-00",

[9] C. Jennings, "draft-jennings-sipping-certs-01.txt", Internet
Draft, "work in progress", July 2003

12. Author Information

James M. Polk
Cisco Systems
2200 East President George Bush Turnpike
Richardson, Texas 75082 USA
jmpolk@cisco.com

12. Full Copyright Statement

Brian Rosen
Marconi Communications, Inc.
2000 Marconi Drive
Warrendale, PA 15086
Brian.rosen@marconi.com

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The Expiration date for this Internet Draft is:

Dec 23rd, 2003

April 27th, 2004