One document matched: draft-ietf-sip-location-conveyance-00.txt
SIP Working Group James M. Polk
Internet Draft Cisco Systems
Expiration: Dec 17th, 2005 Brian Rosen
File: draft-ietf-sip-location-conveyance-00.txt Emergicom
Session Initiation Protocol Location Conveyance
June 17th, 2005
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Copyright Notice
Copyright (C) The Internet Society (2005).
Abstract
This document presents the framework and requirements for usage of
the Session Initiation Protocol (SIP) to convey user location
information from one Session Initiation Protocol (SIP) entity to
another SIP entity. We consider cases where location information is
conveyed from end to end, as well as cases where message routing by
intermediaries is influenced by the location of the session
initiator. We offer a set of solutions to the requirements, each
based on the scenario being addressed.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1 Conventions . . . . . . . . . . . . . . . . . . . . . . . 3
1.2 Changes from Prior Versions . . . . . . . . . . . . . . . 3
2. Location In the Body or in a Header . . . . . . . . . . . . . 6
3. Scope of Location in a Message Body . . . . . . . . . . . . . 7
4. Requirements for UA-to-UA Location Conveyance . . . . . . . . 8
5. Requirements for UA-to-Proxy Server Location Conveyance . . . 9
6. Additional Requirements for Emergency Calls . . . . . . . . . 10
7. Location Conveyance Using SIP . . . . . . . . . . . . . . . . 12
8. Location Conveyance UA-to-UA . . . . . . . . . . . . . . . . 13
8.1 UA-to-UA Using INVITE . . . . . . . . . . . . . . . . . . 13
8.1.1 UA-to-UA Using INVITE with Coordinate Format. . . . . 15
8.1.2 UA-to-UA Using INVITE with Civic Format . . . . . . . 17
8.2 UA-to-UA Using MESSAGE . . . . . . . . . . . . . . . . . 20
8.3 UA-to-UA Using UPDATE . . . . . . . . . . . . . . . . . . 23
8.4 UA-to-UA Using PUBLISH . . . . . . . . . . . . . . . . . 27
8.5 UA-to-UA Location Conveyance Using SUBSCRIBE and NOTIFY . 28
8.6 424 "Bad Location Information" Response Code . . . . . . 28
9. Special Considerations for Emergency Calls . . . . . . . . . 28
9.1 UA-to-Proxy Using INVITE . . . . . . . . . . . . . . . . 29
9.2 UA-to-Proxy Using UPDATE . . . . . . . . . . . . . . . . 34
9.3 425 "Retry Location Body" Response Code . . . . . . . . . 38
10. Meeting RFC 3693 Requirements . . . . . . . . . . . . . . . . 39
11. Open issues . . . . . . . . . . . . . . . . . . . . . . . . . 39
12. Security Considerations . . . . . . . . . . . . . . . . . . . 39
13. IANA Considerations . . . . . . . . . . . . . . . . . . . . 40
13.1 IANA Registration for Response Code 424 . . . . . . . . 40
13.2 IANA Registration for Response Code 425 . . . . . . . . 40
14. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 40
15. References . . . . . . . . . . . . . . . . . . . . . . . . . 40
15.1 Normative References . . . . . . . . . . . . . . . . . 40
15.2 Informative References . . . . . . . . . . . . . . . . . 40
16. Author Information . . . . . . . . . . . . . . . . . . . . . 41
1. Introduction
This document presents the framework and requirements for the usage
of the Session Initiation Protocol (SIP) [RFC3261] for conveyance of
user location information described by [RFC3693] from a SIP entity
to another SIP entity.
There are several situations in which it is appropriate for SIP to
be used to convey Location Information (LI) from one SIP entity to
another. This document specifies requirements when a SIP UAC knows
its location by some means not specified herein, and needs to inform
another SIP entity. One example is one user agent informing another
user agent where it is (i.e., you want to tell your friend where you
are).
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Another example is to reach your nearest pizza parlor. A chain of
pizza parlors may be contacted through a single well known uri
(sip:pizzaparlor.com). This SIP message could be forwarded to the
closest franchise by the pizzaparlor.com proxy server. The
receiving franchise UAS uses the location information of the UAC to
determine the location your delivery.
Another important example is emergency calling. A call to
sip:sos@example.com is an emergency call as in [ID-SIP-SOS]. The
example.com proxy server must route the call to the correct public
safety answering point (PSAP) determined by the location of the
caller. At the PSAP, the UAS must determine the correct
police/fire/ambulance/... service, which is also based on your
location. In many jurisdictions, precise location information of
the caller in distress is a required component of a call to an
emergency center.
A fourth example is a direction service, which might give you verbal
directions to a venue from your present position. This is a case
where only the destination UAS needs to receive the location
information.
This document does not discuss how the UAC discovers or is
configured with its location (either coordinate based such as from
[RFC3825] or civic based such as from [ID-CIVIC]). This document
will also not discuss the contents of the SIP message body part that
is the Location Object (LO) itself. We will specify the
requirements for SIP qualifying as a "using protocol" as defined by
Geopriv in [RFC3693].
Sections 7, 8 and 9 give specific examples (in well-formed SIP
messages) of SIP UA and Proxy behavior for location conveyance, the
last of which is a section devoted to the unique circumstances
regarding emergency calling. Section 10 addresses how this document
adheres to the requirements specified in [RFC3693] (Geopriv
Requirements). Section 11 lists the current open issues with
location conveyance in SIP, and the new open issues recently
discovered as a result of the added effort to this revision.
Section 13 IANA registers 2 new Response codes.
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 [RFC2119].
1.2 Changes from Prior Versions
[NOTE TO RFC-EDITOR: If this document is to be published as an RFC,
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this section is to be removed prior to that event.]
This is a list of the changes that have been made from the SIPPING
WG version -02 to this SIP WG item document version -00:
- Changed which WG this document is in from SIPPING to SIP due to
the extension of the protocol with new Response codes (424 and
425) for when there is an error involving the LO message body.
- Moved most of the well formed SIP messages out of the main body of
this document and into separate appendixes. This should clean up
the document from a readability point of view, yet still provide
the intended decode examples to readers of this document who wish
that level of detail per flow. The first few flows still have the
decoded SIP messages (unencrypted and encrypted).
- Removed some flow examples which no longer made sense
- Changed all references of "ERC" (Emergency Response Center) to
"PSAP" (Public Safety Answering Point) as a result of discussion
within the new ECRIT WG to define a single term
This is a list of the changes that have been made from the sipping-
01 working group version of this effort to the sipping-02 version:
- added requirements for 2 new 4XX error responses (Bad Location
Information) and (Retry Location Body)
- added "Bad Location Information" as section 8.6
- added "Retry Location Body " as section 9.3
- added support for session mode to cover packet sizes larger than
the single packet limit of 1300 bytes in the message body
- added requirement for a SIP entity to SUBSCRIBE to another for
location information
- added SUBSCRIBE and NOTIFY as section 8.5
- added requirement to have user turn off any tracking created by
subscription
- removed doubt about which method to use for updating location
after a INVITE is sent (update)
- cleaned up which method is to be used if there is no dialog
existing (message)
- removed use of reINVITE to convey location
- clarified that UAs include <provided-by> element of PIDF-LO when
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placing an emergency call (to inform PSAP who supplied Location
information)
- updated list of open issues
- added to IANA Considerations section for the two new 4XX level
error responses requested in the last meeting
This is a list of the changes that have been made from the sipping-
00 working group version of this ID to the sipping-01 version:
- Added the offered solution in detail (with message flows,
appropriate SIP Methods for location conveyance, and
- Synchronized the requirements here with those from the Geopriv
Working Group's (attempting to eliminate overlap)
- Took on the task of making this effort the SIP "using protocol"
specification from Geopriv's POV
- Refined the Open Issues section to reflect the progress we've made
here, and to indicate what we have discovered needs addressing,
but has not been to date.
This is a list of the changes that have been made from the -01
individual submission version to the sipping-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
This is a list of the changes that have been made from the
individual submission version -00 to the -01 version
- Added the IPR Statement section
- Adjusted a few requirements based on suggestions from the
Minneapolis meeting
- Added requirements that the UAC is to include from where it
learned its location in any transmission of its LI
- Distinguished the facts (known to date) that certain jurisdictions
relieve persons of their right to privacy when they call an PSAP,
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while other jurisdictions maintain a person's right to privacy,
while still others maintain a person's right to privacy - but only
if they ask that their service be set up that way.
- Made the decision that TLS is the security mechanism for location
conveyance in emergency communications (vs. S/MIME, which is still
the mechanism for UA-to-UA non-emergency location conveyance
cases).
- Added the Open Issue of whether a Proxy can insert location
information into an emergency SIP INVITE message, and some of the
open questions surrounding the implications of that action
- added a few names to the acknowledgements section
2. Location In the Body or in a Header
In determining where "location" is placed in a SIP message,
consideration is taken as to where the trust model is based on the
architecture involved.
If the user agent has the location stored within it, and one user
agent wants to inform another user agent where it is, it seems
reasonable to have this accomplished by placing the location
information (coordinate or civic) 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. This is location by-value.
Although SIP [RFC3261] does not permit SIP intermediaries to modify
or delete a message body, there is no restriction on viewing message
bodies. S/MIME protected message bodies, implemented on bodies for
communications between user agents only, would render the location
object opaque to a proxy server for any desired modification if it
is not correct or precise enough from that proxy's point of view
(were it to be able to view it). This problem is similar to that
raised in Session Policy [ID-Sess-Pol], where an intermediary may
need information in a body, such as IP address of media streams or
codec choices to route a call properly. Requirements in [ID-Sess-
Pol] are applicable to routing based on location, and are
incorporated in these requirements by reference.
It is conceivable to create a new header for location information.
However, [RFC3693] prefers S/MIME for security of Location
Information, and indeed S/MIME is preferable in SIP [RFC3261] for
protecting a message body. Accordingly, these requirements specify
location be carried in a body when it is known to/stored in a user
agent.
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It is the use of S/MIME however, that limits routing based on
location. Therefore, it seems appropriate to require that, where
routing is dependent on location, protection of the location
information object be accomplished by other mechanisms visible to
SIP proxies: here TLS ("sips:" from [RFC3261]). It is envisioned
that S/MIME SHOULD be used when location information is not required
by proxy servers, and TLS MUST be used when it is. The UAC will
need to know the difference in the call's intent as to which
security mechanism to engage for LI conveyance.
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 within the ECRIT WG.
3. Scope of Location in a Message Body
As concluded from the previous section, location information is to
be contained within a message body when the user agent has this
information locally. If either another body (SDP for example) is
also to be sent in the message, or the LI is to be protected with
S/MIME, the rules stated in section 7 of [RFC3261] regarding
multipart MIME bodies MUST be followed. The format and
privacy/security rules of [RFC3693] MUST too be followed.
User agents providing location can convey it incorrectly or
inappropriately. Therefore, there needs to be a new UAC error
response code created to inform the UAC by a UAS or Proxy of this
rejected
request message because of the location information in the message.
There needs to be two new response codes currently not defined in
SIP:
1) the first indicating the existing location information was not
considered good by the viewing SIP element.
There will be times in which the UAC does not know its location
information, or another SIP entity knows the UAC's location better
than the UAC itself. How this is determined is out of scope of this
document. In these times, a Proxy servers that know the location
of the UAC needs inform the UAC of its location information and have
that UAC include that message body in its next SIP message to the
same destination UA. This error code needs to be unique with
respect to the error code for merely incorrect location information
from the UAC.
2) a second new response code indicating the existing location
information was not considered good by the viewing SIP element,
one that includes a new message body with new location
information of the UAC to be used in a subsequent SIP Request by
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the UAC.
This second response code would be more applicable for cases in
which a SIP intermediary knows more about the location of the UAC
than the UAC, and needs to get the more appropriate LO into the SIP
message. This cannot occur with existing rules stating message
bodies cannot be modified or added by intermediaries. This new
response code message containing a new LO of the UAC appears the
best course of action.
If there can be more than one LO within the same SIP message is not
addressed in this document at this time.
If there can be more than one LO within the same SIP message and the
message is routed by a SIP Proxy based on the contents of an LO,
this document currently does not specify how the proxy determines
which LO to route the message based on. This is currently an open
question as to whether this topic is addressed in the SIP WG or in
the ECRIT WG, therefore this is left for future study at this time.
4. Requirements for UA-to-UA Location Conveyance
The following are the requirements for UA-to-UA Location Conveyance
Situations where routing is not based on the LI of either UA, and
location is stored/cached in the UAC:
U-U1 - Dialog-initiating SIP Requests and their responses MUST
support Location Conveyance
U-U2 - The SIP MESSAGE method [RFC3428] MUST support Location
Conveyance
U-U3 - Other SIP Requests SHOULD support Location Conveyance
U-U4 - UAC Location information SHOULD remain confidential e2e
to the destination UAS except when the session is to an
identifiable emergency endsystem.
U-U5 - UAC MUST not use S/MIME on the Location Object message body
if the message is a dialog related or MESSAGE Request
message unless the UAC has a pre-established association
with the routing SIP intermediary.
U-U6 - UAS Location information SHOULD remain confidential e2e
to the destination UAC except when the session is to/from an
identifiable emergency endsystem.
Emergency callback is one example where this may apply.
U-U7 - The privacy and security rules established within the
Geopriv Working Group that would categorize SIP as a 'using
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protocol' MUST be met [RFC3693]. See Section 10 for
analysis.
U-U8 - Location information MUST be contained in the location
Object as defined in [ID-PIDF-LO], which will satisfy all
format requirements for interoperability.
U-U9 - User Agents and Proxies SHOULD be able to handle SIP
messages in which Location Information is fragmented across
multiple packets.
U-U10 - There MUST be a unique UAC error response code informing
the UAC it did not provide applicable location information.
U-U11 - There MUST be a means for publishing location state
information for a particular presentity to a Presence
Compositor Server
U-U12 - User Agents and Proxies SHOULD be able to handle SIP
messages which contain more than one Location Object.
5. Requirements for UA-to-Proxy Server Location Conveyance
The following are the requirements for UA-to-Proxy Server Location
Conveyance situations:
U-PS1 - MUST work with dialog-initiating SIP Requests and
responses, as well as the SIP MESSAGE method [RFC3428], and
SHOULD work with most SIP messages.
U-PS2 - UAC location information SHOULD remain opaque to
intermediaries the message was not addressed to, but MUST
be useable (i.e. viewable) by intermediary proxy servers
requiring location knowledge of the UAC to properly route
the message.
U-PS3 - The privacy and security rules established within the
Geopriv Working Group which would categorize SIP as a
'using protocol' MUST be met [RFC3693].
U-PS4 - Proxy servers MUST NOT modify or remove an LO message body
part ([RFC3261] currently forbids this).
U-PS5 - A SIP message containing a Location Object MUST NOT be
rejected by a SIP intermediary because the message body
part or LO itself was not understood (except when the
intermediary complies with requirement U-PS7 below, or when
the SIP message is addressed to that intermediary).
With regards to requirement U-PS5, not all SIP Proxies are expected
to route messages based on the contained Location Object from the
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UAC. There will likely be a SIP Proxy able to perform this function
downstream, and the original SIP message needs to reach that
location enabled Proxy to route correctly.
U-PS6 - There MUST be a unique UAC error response code informing
the UAC it did not provide applicable location information.
U-PS7 - There MUST be a unique UAC error response code informing
the UAC it did not provide applicable location information,
and to include the location information contained in the
message body of the error message for usage in the UAC's
next attempt to the same UAS of the original message.
6. Additional Requirements for Emergency Calls
Emergency calls have requirements that are not generally important
to other uses for location 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 unacceptable number of callers to abandon the
call before it is completed. Two-second call completion time is a
goal of many existing emergency call centers. Allocating 25% of the
call set up for processing privacy concerns seems reasonable; 1
second would be 50% of the goal, which seems unacceptable; less than
0.5 second seems unachievable, therefore:
E-1 - Privacy mechanisms MUST add no more than 0.5 second of call
setup time when implemented in present technology UAs and
Proxy Servers.
It may be acceptable for full privacy mechanisms related to the
location of the UAC (and it's user) to be tried on an initial
attempt to place a call, as long as the call attempt may be retried
without the privacy mechanism present (or enabled) if the first
attempt fails. Abandoning privacy in cases of failure of the
privacy mechanism might be subject to user preference, although such
a feature would be within the domain of a UA implementation and thus
not subject to standardization. It should be noted that some
jurisdictions have laws that explicitly deny any expectation of
location privacy when making an emergency call, while others grant
the user the ability to remain anonymous even when calling an PSAP.
So far, this has been offered in some jurisdictions, but the user
within that jurisdiction must state this preference, as it is not
the default configuration.
E-2 û Privacy mechanisms MUST NOT be mandatory for successful
conveyance of location during an (sos-type) emergency call.
E-3 - It MUST be possible to provide a privacy mechanism (that does
not violate the other requirements within this document) to a
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user within a jurisdiction that gives that user the right to
choose not to reveal their location even when contacting an
PSAP.
E-4 û The retention and retransmission policy of the PSAP MUST be
able to be made available to the user, and override the
user's normal policy when local regulation governs such
retention and retransmission (but does not violate
requirement E-3). As in E-2 above, requiring the use of the
PSAP's retention and/or retransmission policy may be subject
to user preference; although in most jurisdictions, local
laws specify such policies and may not be overridden by user
preference.
Location information is considered so important during emergency
calls, that it is to be transmitted even when it is not considered
reliable, or might even be wrong. For example, some application
might know that the DHCP reply with location information was
overwritten recently (or exactly) when a VPN connection was
activated. This could, and likely will, provide any new location
information to the UA from somewhere far away from the UA (perhaps
the user's corporate facility).
E-5 - A call transfer between response centers MUST NOT be
considered a violation of the distribution privacy attribute
contained within the location object.
This transfer will likely be for legitimate reasons; for example,
the session was misrouted to the wrong PSAP, and is referred
[RFC3515] to the correct one.
E-6 Location information MUST be transmitted if known to the UAC,
in all calls to a PSAP, even in the case it is not considered
reliable.
With that in mind, it is important to distinguish the location
information learned locally from LI learned over a VPN; which in
itself is useful additional information to that PSAP operator.
E-7 THE UA must provide the actual LI of the endpoint, and not
location which might have been erroneously given to it by, e.g.
a VPN tunnel DHCP server.
E-8 A PSAP MAY wish to SUBSCRIBE to the UAC that initiated a
session. If this is supported by the UAC, all NOTIFY messages
MUST contain the UAC's location information.
This is a means for the emergency response centers to maintain a
location the callers in distress.
E-9 It MUST be possible that any UAC supporting E-8 be informed of
this subscription, as this will provide a means of alert to the
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user who does not wish this capability to remain enabled.
7. Location Conveyance using SIP
Geopriv is the IETF working group assigned to define a Location
Object for carrying within another protocol to convey geographic
location of an endpoint to another entity. This Location Object
will be supplied within SIP to convey location of a UA (or user of a
UA). The Location Object (LO) is defined in [ID-PIDF-LO]. Section
26 of [RFC3261] defines the security functionality SIPS for
transporting SIP messages with either TLS or IPsec, and S/MIME for
encrypting message bodies from SIP intermediaries that would
otherwise have access to reading the clear-text bodies. For UA-to-
UA location conveyance, using the PIDF-LO body satisfies the entire
format and message-handling requirements as stated in the baseline
Geopriv Requirements [RFC3693]. SIP entities that will carry an LO
MUST implement S/MIME for encrypting on an end-to-end basis the
location of a user agent, satisfying [RFC3693]'s security
requirements. The SIPS-URI from [RFC3261] SHOULD also be used for
further message protection (message integrity, authentication and
message confidentiality) and MUST be used when S/MIME is not used
(when not violating the requirements for emergency messaging
detailed in section 6 of this document). The entities sending and
receiving the LO MUST obey the privacy and security instructions in
the LO to be compliant with this specification.
Self-signed certificates SHOULD NOT be used for protecting LI, as
the sender does not have a secure identity of the recipient.
Several LOs MAY be included in a body. If the message length
exceeds the maximum message length of a single packet, session mode
is to be used.
Several SIP Methods are capable (and applicable) to carry the LO
message body. The Methods are divided into two groups, one for
those applicable for UA-to-UA location conveyance, and the other
group for UA-to-Proxy Location conveyance for routing the message.
The list of applicable Methods for UA-to-UA location conveyance is:
INVITE,
UPDATE,
MESSAGE,
SUBSCRIBE/NOTIFY, and
PUBLISH.
The list of applicable Methods for UA-to-Proxy location conveyance
is:
INVITE,
UPDATE, and
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MESSAGE
While the authors do not yet see a reason to have location conveyed
in the OPTIONS, ACK, PRACK, BYE, REFER and CANCEL Methods, we do not
see a reason to prevent carrying a LO within these Method Requests
as long as the SIP message meets the requirements stated within this
document.
A 200 OK to an INVITE MAY carry the UAS's LO back to the UAC that
provided its location in the INVITE, but this is not something
that can be required due to the timing of the INVITE to 200 OK
messages, with potential local/user policy requiring the called user
to get involved in determining if the caller is someone they wish to
give location to (and at what precision).
For UA-to-Proxy location conveyance, there are two cases: one in
which all proxies on the path from the UA to the proxy that requires
location can be trusted with the LI, and one in which intermediate
proxies may not be trusted. The former may be implemented with
"hop-by-hop" security as specified in [RFC3261] using sips: (i.e.
TLS security). In particular, emergency call routing requires
routing proxies to know location, and sips: protection is
appropriate. The latter case is under study by the SIPPING working
group under the subject "End to Middle" security [ID-End-Mid-Sec].
Regardless which scenario (UA-to-UA or UA-to-Proxy) is used to
convey location, SIP entities MUST adhere to the rules of [RFC3693],
specifically the retention and distribution (privacy) attributes of
a UA's location. When Alice is deciding how to transmit her
location, she should be keenly aware of the parameters in which she
wants her location to be stored and distributed. However, once she
sends that location information to Bob, he MUST also now obey
Alice's wishes regarding these privacy attributes if he is deciding
to inform another party about Alice. This is a fundamental
principle of the Geopriv Working Group, i.e. "PRIVACY".
8. User Agent-to-User Agent Location Conveyance
The offered solution here for the User-to-User location conveyance
between UAs is used with the INVITE, UPDATE, MESSAGE, SUB/NOT and
PUBLISH Methods in the following subsections.
Well formed SIP messages are only in the main body of this document
for the first few examples. All well formed SIP message flows are
in separate appendixes at the end of this document for brevity here,
while there providing a complete set of example flows to review and
comment on.
8.1 UA-to-UA using INVITE Method
Below is a common SIP session set-up sequence between two user
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agents. In this example, Alice will provide Bob with her geographic
location in the INVITE message.
UA Alice UA Bob
| INVITE [M1] |
|---------------------------------------->|
| |
| 200 OK [M2] |
|<----------------------------------------|
| |
| ACK [M3] |
|---------------------------------------->|
| |
| RTP |
|<=======================================>|
| |
Figure 1. UA-UA with Location in INVITE
User agent Alice invites user agent Bob to a session [M1 of Figure
1].
- Within this INVITE is a multipart body indication that it is
S/MIME encrypted [according to the rules of RFC3261] by Alice for
Bob. One body part contains the SDP offered by Alice to Bob.
Alice's location (here coordinate based) is the other body part
contained in this INVITE.
- Bob responses with a 200 OK [M2] (choosing a codec as specified by
the Offer/Answer Model [RFC3264]). Bob can include his location
in the 200 OK response, but this shouldn't be expected due to user
timing. If Bob wants to provide his location to Alice after the
200 OK, but before a BYE, the UPDATE Method [RFC3311] should be
used.
- Alice's UA replies with an ACK and the session is set up.
Figure 1. does not include any Proxies because in it assumed they
would not affect the session set-up with respect to whether or not
Alice's location is in a message body part, and Proxies don't react
to S/MIME bodies, making their inclusion more or less moot and more
complex than necessary.
The most relevant message in Figure 1 having to do with location is
(obviously) the message with the location object in it [M1]. So to
cut down on length of this document, only the INVITE message in this
example will be shown. Section 8.1.1 will give an example of this
well formed INVITE message using a Coordinate location format.
Section 8.1.2 will give an example of this well formed INVITE
message using the civic location format.
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8.1.1 UA-to-UA INVITE with Coordinate Location Using S/MIME
Below is a well-formed SIP INVITE Method message to the example in
Figure 1 in section 8.1.
[Message 1 in Figure 1]
INVITE sips:bob@biloxi.example.com SIP/2.0
Via: SIP/2.0/TLS pc33.atlanta.example.com
;branch=z9hG4bK776asdhds
Max-Forwards: 70
To: Bob <sips:bob@biloxi.example.com>
From: Alice <sips:alice@atlanta.example.com>;tag=1928301774
Call-ID: a84b4c76e66710@pc33.atlanta.example.com
CSeq: 314159 INVITE
Contact: <sips:alice@pc33.atlanta.example.com>
Content-Type: application/pkcs7-mime;
smime-type=enveloped-data; name=smime.p7m
Content-Disposition: attachment;
filename=smime.p7m handling=required
Content-Type: multipart/mixed; boundary=boundary1
--boundary1
Content-Type: application/sdp
v=0
o=alice 2890844526 2890844526 IN IP4 atlanta.example.com
c=IN IP4 10.1.3.33
t=0 0
m=audio 49172 RTP/AVP 0 4 18
a=rtpmap:0 PCMU/8000
--boundary1
Content-type: application/cpim-pidf+xml
<?xml version="1.0" encoding="UTF-8"?>
<presence xmlns="urn:ietf:params:xml:ns:pidf"
xmlns:gp="urn:ietf:params:xml:ns:pidf:geopriv10"
xmlns:gml="urn:opengis:specification:gml:schema-
xsd:feature:v3.0"
entity="pres:alice@atlanta.example.com">
<tuple id="sg89ae">
<timestamp>2005-11-11T08:57:29Z</timestamp>
<status>
<gp:geopriv>
<gp:location-info>
<gml:location>
<gml:Point gml:id="point96" srsName="epsg:4326">
<gml:coordinates>41.87891N
87.63649W</gml:coordinates>
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</gml:Point>
</gml:location>
<method>dhcp</method>
</gp:location-info>
<gp:usage-rules>
<gp:retransmission-allowed>no</gp:retransmission-allowed>
<gp:retention-expiry>2005-11-13T14:57:29Z</gp:retention-
expiry>
</gp:usage-rules>
</gp:geopriv>
</status>
</tuple>
</presence>
--boundary1--
8.1.1.1 UA-to-UA INVITE with Coordinate Location Not Using S/MIME
Below is a well-formed SIP INVITE Method message to the example in
Figure 1 in section 8.1. This message is here to show that although
the requirements are mandatory to implement proper security, it is
not mandatory to use. This message below is show for those cases
where hop-by-hop security is deployed.
[Message 1 in Figure 1]
INVITE sip:bob@biloxi.example.com SIP/2.0
Via: SIP/2.0/TCP pc33.atlanta.example.com
;branch=z9hG4bK74bf9
Max-Forwards: 70
From: Alice <sip:alice@atlanta.example.com>;tag=9fxced76sl
To: Bob <sip:bob@biloxi.example.com>
Call-ID: 3848276298220188511@atlanta.example.com
CSeq: 31862 INVITE
Contact: <sip:alice@atlanta.example.com>
Content-Type: multipart/mixed; boundary=boundary1
Content-Length: ...
--boundary1
Content-Type: application/sdp
v=0
o=alice 2890844526 2890844526 IN IP4 atlanta.example.com
c=IN IP4 10.1.3.33
t=0 0
m=audio 49172 RTP/AVP 0 4 18
a=rtpmap:0 PCMU/8000
--broundary1
Content-Type: application/cpim-pidf+xml
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<?xml version="1.0" encoding="UTF-8"?>
<presence xmlns="urn:ietf:params:xml:ns:pidf"
xmlns:gp="urn:ietf:params:xml:ns:pidf:geopriv10"
xmlns:gml="urn:opengis:specification:gml:schema-
xsd:feature:v3.0"
entity="pres:alice@atlanta.example.com">
<tuple id="sg89ae">
<timestamp>2005-11-11T08:57:29Z</timestamp>
<status>
<gp:geopriv>
<gp:location-info>
<gml:location>
<gml:Point gml:id="point96" srsName="epsg:4326">
<gml:coordinates>41.87891N
87.63649W</gml:coordinates>
</gml:Point>
</gml:location>
<method>dhcp</method>
</gp:location-info>
<gp:usage-rules>
<gp:retransmission-allowed>no</gp:retransmission-allowed>
<gp:retention-expiry>2005-11-13T14:57:29Z</gp:retention-
expiry>
</gp:usage-rules>
</gp:geopriv>
</status>
</tuple>
</presence>
--boundary1--
8.1.2 UA-to-UA INVITE with Civic Location Using S/MIME
Below is a well-formed SIP INVITE Method message to the example in
Figure 1 in section 8.1 using the civic location format.
[Message 1 in Figure 1]
INVITE sips:bob@biloxi.example.com SIP/2.0
Via: SIP/2.0/TLS pc33.atlanta.example.com
;branch=z9hG4bK776asdhds
Max-Forwards: 70
To: Bob <sips:bob@biloxi.example.com>
From: Alice <sips:alice@atlanta.example.com>;tag=1928301774
Call-ID: a84b4c76e66710@pc33.atlanta.example.com
CSeq: 314159 INVITE
Contact: <sips:alice@pc33.atlanta.example.com>
Content-Type: application/pkcs7-mime;
smime-type=enveloped-data; name=smime.p7m
Content-Disposition: attachment;
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filename=smime.p7m handling=required
Content-Type: multipart/mixed; boundary=boundary1
--boundary1
Content-Type: application/sdp
v=0
o=alice 2890844526 2890844526 IN IP4 atlanta.example.com
c=IN IP4 10.1.3.33
t=0 0
m=audio 49172 RTP/AVP 0 4 18
a=rtpmap:0 PCMU/8000
--boundary1
Content-type: application/cpim-pidf+xml
<?xml version="1.0" encoding="UTF-8"?>
<presence xmlns="urn:ietf:params:xml:ns:pidf"
xmlns:gp="urn:ietf:params:xml:ns:pidf:geopriv10"
xmlns:gml="urn:opengis:specification:gml:schema-
xsd:feature:v3.0"
entity="pres:alice@atlanta.example.com">
<tuple id="sg89ae">
<timestamp>2005-11-11T08:57:29Z</timestamp>
<status>
<gp:geopriv>
<gp:location-info>
<cl:civilAddress>
<cl:country>US</cl:country>
<cl:A1>Illinois</cl:A1>
<cl:A3>Chicago</cl:A3>
<cl:HNO>233</cl:HNO>
<cl:PRD>South</cl:PRD>
<cl:A6>Wacker</cl:A6>
<cl:STS>Drive</cl:STS>
<cl:PC>60606</cl:PC>
<cl:LMK>Sears Tower</cl:LMK>
<cl:FLR>1</cl:FLR>
<cl:civilAddress>
<method>dhcp</method>
<provided-by><nena>www.cisco.com</nena></provided-by/>
</gp:location-info>
<gp:usage-rules>
<gp:retransmission-allowed>no</gp:retransmission-allowed>
<gp:retention-expiry>2005-11-13T14:57:29Z</gp:retention-
expiry>
</gp:usage-rules>
</gp:geopriv>
</status>
</tuple>
</presence>
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--boundary1--
8.1.2.1 UA-to-UA INVITE with Civic Location Not Using S/MIME
Below is a well-formed SIP INVITE Method message to the example in
Figure 1 in section 8.1. This message is here to show that although
the requirements are mandatory to implement proper security, it is
not mandatory to use. This message below is show for those cases
where the sending user does not wish to use security mechanisms in
transmitting their coordinate location.
[Message 1 in Figure 1]
INVITE sip:bob@biloxi.example.com SIP/2.0
Via: SIP/2.0/TCP pc33.atlanta.example.com
;branch=z9hG4bK74bf9
Max-Forwards: 70
From: Alice <sip:alice@atlanta.example.com>;tag=9fxced76sl
To: Bob <sip:bob@biloxi.example.com>
Call-ID: 3848276298220188511@atlanta.example.com
CSeq: 31862 INVITE
Contact: <sip:alice@atlanta.example.com>
Content-Type: multipart/mixed; boundary=boundary1
Content-Length: ...
--boundary1
Content-Type: application/sdp
v=0
o=alice 2890844526 2890844526 IN IP4 atlanta.example.com
c=IN IP4 10.1.3.33
t=0 0
m=audio 49172 RTP/AVP 0 4 18
a=rtpmap:0 PCMU/8000
--broundary1
Content-type: application/cpim-pidf+xml
<?xml version="1.0" encoding="UTF-8"?>
<presence xmlns="urn:ietf:params:xml:ns:pidf"
xmlns:gp="urn:ietf:params:xml:ns:pidf:geopriv10"
xmlns:gml="urn:opengis:specification:gml:schema-
xsd:feature:v3.0"
entity="pres:alice@atlanta.example.com">
<tuple id="sg89ae">
<timestamp>2005-11-11T08:57:29Z</timestamp>
<status>
<gp:geopriv>
<gp:location-info>
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<cl:civilAddress>
<cl:country>US</cl:country>
<cl:A1>Illinois</cl:A1>
<cl:A3>Chicago</cl:A3>
<cl:HNO>233</cl:HNO>
<cl:PRD>South</cl:PRD>
<cl:A6>Wacker</cl:A6>
<cl:STS>Drive</cl:STS>
<cl:PC>60606</cl:PC>
<cl:LMK>Sears Tower</cl:LMK>
<cl:FLR>1</cl:FLR>
<cl:civilAddress>
<method>dhcp</method>
<provided-by><nena>www.cisco.com</nena></provided-by/>
</gp:location-info>
<gp:usage-rules>
<gp:retransmission-allowed>no</gp:retransmission-allowed>
<gp:retention-expiry>2005-11-13T14:57:29Z</gp:retention-
expiry>
</gp:usage-rules>
</gp:geopriv>
</status>
</tuple>
</presence>
--boundary1--
8.2 UA-to-UA Using MESSAGE Method
Anytime a user transmits location information outside a dialog, the
MESSAGE Method is to be used. The logic here is as follows:
- UPDATE isn't appropriate because it is for the updating of
session capabilities and parameters of a dialog (after the
INVITE included location information).
- reINVITE isn't appropriate because it is only used (or only
supposed to be used) for changing the parameters of an existing
dialog, and one might not exist in all cases of location
conveyance.
This leaves MESSAGE as the only viable Request Method for location
conveyance outside of a dialog between two users (Alice and Bob in
this case). The following is an example of this communication.
UA Alice UA Bob
| MESSAGE [M1] |
|---------------------------------------->|
| |
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| 200 OK [M2] |
|<----------------------------------------|
| |
Figure 2. UA-UA with Location in MESSAGE
Section 8.2.1 will give the well formed MESSAGE Method containing a
well formed Geopriv Location Object using the Coordinate location
format that fully complies with all security requirements - SIPS for
hop-by-hop security, and S/MIME for message body confidentiality
end-to-end, as well as adhering to the retention and distribution
concerns from [RFC3693]. Section 8.2.2 will show the Civic Location
format alternative to the same location, as conveyed from Alice to
Bob. This section does not adhere to confidentiality or integrity
concerns of [RFC3693], but does convey retention and distribution
indicators from Alice.
8.2.1 UA-to-UA MESSAGE with Coordinate Location Using S/MIME
Below is M1 from Figure 2 in section 8.2. that is fully secure and
in compliance with Geopriv requirements in [RFC3693] for security
concerns.
[Message 1 in Figure 2]
MESSAGE sips:bob@biloxi.example.com SIP/2.0
Via: SIP/2.0/TLS pc33.atlanta.example.com
;branch=z9hG4bK776asegma
Max-Forwards: 70
To: Bob <sips:bob@biloxi.example.com>
From: Alice <sips:alice@atlanta.example.com>;tag=1928301774
Call-ID: a84b4c76e66710@pc33.atlanta.example.com
CSeq: 22756 MESSAGE
Content-Type: application/pkcs7-mime;
smime-type=enveloped-data; name=smime.p7m
Content-Disposition: attachment;
filename=smime.p7m handling=required
Content-Type: multipart/mixed; boundary=boundary1
--boundary1
Content-Type: text/plain
Here's my location, Bob?
--broundary1
Content-Type: application/cpim-pidf+xml
Content-Disposition: render
Content-Description: my location
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<?xml version="1.0" encoding="UTF-8"?>
<presence xmlns="urn:ietf:params:xml:ns:pidf"
xmlns:gp="urn:ietf:params:xml:ns:pidf:geopriv10"
xmlns:gml="urn:opengis:specification:gml:schema-
xsd:feature:v3.0"
entity="pres:alice@atlanta.example.com">
<tuple id="sg89ae">
<timestamp>2005-11-11T08:57:29Z</timestamp>
<status>
<gp:geopriv>
<gp:location-info>
<gml:location>
<gml:Point gml:id="point96" srsName="epsg:4326">
<gml:coordinates>41.87891N
87.63649W</gml:coordinates>
</gml:Point>
</gml:location>
<method>dhcp</method>
</gp:location-info>
<gp:usage-rules>
<gp:retransmission-allowed>no</gp:retransmission-allowed>
<gp:retention-expiry>2005-11-13T14:57:29Z</gp:retention-
expiry>
</gp:usage-rules>
</gp:geopriv>
</status>
</tuple>
</presence>
--boundary1--
8.2.2 UA-to-UA MESSAGE with Civic Location Not Using S/MIME
Below is a well-formed SIP MESSAGE Method message to the example in
Figure 2 in section 8.2 when hop-by-hop security mechanisms are
deployed.
[Message 1 in Figure 2]
MESSAGE sip:bob@biloxi.example.com SIP/2.0
From: <sip:alice@atlanta.example.com>;tag=34589882
To: <sip:bob@biloxi.example.com>
Call-ID: 9242892442211117@atlanta.example.com
CSeq: 6187 MESSAGE
Content-Type: application/cpim-pidf+xml
Content-ID: <766534765937@atlanta.example.com>
Content-Disposition: render
Content-Description: my location
<?xml version="1.0" encoding="UTF-8"?>
<presence xmlns="urn:ietf:params:xml:ns:pidf"
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xmlns:gp="urn:ietf:params:xml:ns:pidf:geopriv10"
xmlns:gml="urn:opengis:specification:gml:schema-
xsd:feature:v3.0"
entity="pres:alice@atlanta.example.com">
<tuple id="sg89ae">
<timestamp>2005-11-11T08:57:29Z</timestamp>
<status>
<gp:geopriv>
<gp:location-info>
<cl:civilAddress>
<cl:country>US</cl:country>
<cl:A1>Illinois</cl:A1>
<cl:A3>Chicago</cl:A3>
<cl:HNO>233</cl:HNO>
<cl:PRD>South</cl:PRD>
<cl:A6>Wacker</cl:A6>
<cl:STS>Drive</cl:STS>
<cl:PC>60606</cl:PC>
<cl:LMK>Sears Tower</cl:LMK>
<cl:FLR>1</cl:FLR>
<cl:civilAddress>
<method>dhcp</method>
</gp:location-info>
<gp:usage-rules>
<gp:retransmission-allowed>no</gp:retransmission-allowed>
<gp:retention-expiry>2005-11-13T14:57:29Z</gp:retention-
expiry>
</gp:usage-rules>
</gp:geopriv>
</status>
</tuple>
</presence>
8.3 UA-to-UA Location Conveyance Using UPDATE
UPDATE MUST NOT be used to send location information from UA-to-UA
unless location has already been sent in an INVITE or corresponding
200 OK that was the first message exchange in the same dialog set-
up. The same security properties used in the INVITE MUST be used in
the UPDATE message.
The UPDATE Method is to be used any time location information is to
be updated between UAs setting up a dialog or after the dialog has
been established, no matter how long that dialog has been
operational. reINVITE is out of scope here, and the MESSAGE Method
is for non-dialog location conveyance between UAs only.
One reason for this message being generated is if either UA that
sent its location information to the other UA (say in the INVITE and
corresponding 200 OK) is if either UA determines that is has moved
while the dialog has remained operational. How this movement is
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determined is outside the scope of this document, but ultimately
should be configurable by local administration or the user of the
UA. By how much Alice has moved to trigger the "sense of movement"
(i.e. the need to send new location) to Bob is also outside the
scope of this specification, but ultimately should be configurable
by local administration or the user of the UA.
In Figure 3., we have an example message flow involving the UPDATE
Method. We are not including all the messages for space reasons. M1
is a well formed SIP message that contains Alice's location. During
the session set-up, Alice's UA knows it has moved while knowing too
the session has not been formally accepted by Bob. Alice's UA
decides to update Bob with her new location with an UPDATE Method
message. Messages M2, M3 and M4 have nothing to do with location
conveyance, therefore will not be shown in detail. Only M1 and M5
will be shown.
NOTE: A similar use for UPDATE is within the UA-to-Proxy Location
Conveyance section of this document.
UA Alice UA Bob
| INVITE [M1] |
|---------------------------------------->|
| |
| 183 (session Progress) [M2] |
|<----------------------------------------|
| |
| PRACK [M3] |
|---------------------------------------->|
| |
| ACK (PRACK) [M4] |
|<----------------------------------------|
| |
| UPDATE [M5] |
|---------------------------------------->|
| |
| ACK (UPDATE) [M6] |
|<----------------------------------------|
| |
| 200 OK (INVITE) [M7] |
|<----------------------------------------|
| |
| RTP |
|<=======================================>|
| |
Figure 3. UA-UA with Location in UPDATE
The following section will include the M1 and M5 messages in detail,
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but only in the civic format.
8.3.1 UA-to-UA UPDATE with Civic Location Not Using S/MIME
Here is the initial INVITE from Alice to Bob.
[M1 INVITE to Bob]
INVITE sips:bob@biloxi.example.com SIP/2.0
Via: SIP/2.0/TLS pc33.atlanta.example.com
;branch=z9hG4bK776asdhds
Max-Forwards: 70
To: Bob <sips:bob@biloxi.example.com>
From: Alice <sips:alice@atlanta.example.com>;tag=1928301774
Call-ID: a84b4c76e66710@pc33.atlanta.example.com
CSeq: 314159 INVITE
Contact: <sips:alice@pc33.atlanta.example.com>
Content-Type: application/pkcs7-mime;
smime-type=enveloped-data; name=smime.p7m
Content-Disposition: attachment;
filename=smime.p7m handling=required
Content-Type: multipart/mixed; boundary=boundary1
--boundary1
Content-Type: application/sdp
v=0
o=alice 2890844526 2890844526 IN IP4 atlanta.example.com
c=IN IP4 10.1.3.33
t=0 0
m=audio 49172 RTP/AVP 0 4 18
a=rtpmap:0 PCMU/8000
--boundary1
Content-type: application/cpim-pidf+xml
<?xml version="1.0" encoding="UTF-8"?>
<presence xmlns="urn:ietf:params:xml:ns:pidf"
xmlns:gp="urn:ietf:params:xml:ns:pidf:geopriv10"
xmlns:gml="urn:opengis:specification:gml:schema-
xsd:feature:v3.0"
entity="pres:alice@atlanta.example.com">
<tuple id="sg89ae">
<timestamp>2005-11-11T08:57:29Z</timestamp>
<status>
<gp:geopriv>
<gp:location-info>
<cl:civilAddress>
<cl:country>US</cl:country>
<cl:A1>Illinois</cl:A1>
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<cl:A3>Chicago</cl:A3>
<cl:HNO>233</cl:HNO>
<cl:PRD>South</cl:PRD>
<cl:A6>Wacker</cl:A6>
<cl:STS>Drive</cl:STS>
<cl:PC>60606</cl:PC>
<cl:LMK>Sears Tower</cl:LMK>
<cl:FLR>1</cl:FLR>
<cl:civilAddress>
<method>dhcp</method>
<method>802.11</method>
<provided-by>www.cisco.com</provided-by/>
</gp:location-info>
<gp:usage-rules>
<gp:retransmission-allowed>no</gp:retransmission-allowed>
<gp:retention-expiry>2005-11-13T14:57:29Z</gp:retention-
expiry>
</gp:usage-rules>
</gp:geopriv>
</status>
</tuple>
</presence>
--boundary1--
Alice moves locations (with her UA detecting the movement), causing
her UA to generate an UPDATE message ([M5] of Figure 3) prior to
her UA receiving a final response from Bob. Here is that message:
M5 UPDATE to Bob
UPDATE sips:bob@biloxi.example.com/TCP SIP/2.0
Via: SIP/2.0/TLS pc33.atlanta.example.com
;branch=z9hG4bK776asdhds
Max-Forwards: 70
To: Bob <sips:bob@biloxi.example.com>
From: Alice <sips:alice@atlanta.example.com>;tag=1928
Call-ID: a84b4c76e66710@pc33.atlanta.example.com
CSeq: 10197 UPDATE
Contact: <sips:alice@pc33.atlanta.example.com>
Content-Type: application/pkcs7-mime;
smime-type=enveloped-data; name=smime.p7m
Content-Disposition: attachment;
filename=smime.p7m handling=required
Content-Type: multipart/mixed; boundary=boundary1
--boundary1
Content-Type: application/sdp
v=0
o=alice 2890844526 2890844526 IN IP4 atlanta.example.com
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c=IN IP4 10.1.3.33
t=0 0
m=audio 49172 RTP/AVP 0 4 18
a=rtpmap:0 PCMU/8000
--boundary1
Content-type: application/cpim-pidf+xml
<?xml version="1.0" encoding="UTF-8"?>
<presence xmlns="urn:ietf:params:xml:ns:pidf"
xmlns:gp="urn:ietf:params:xml:ns:pidf:geopriv10"
xmlns:gml="urn:opengis:specification:gml:schema-
xsd:feature:v3.0"
entity="pres:alice@atlanta.example.com">
<tuple id="sg89ae">
<timestamp>2005-11-11T08:57:29Z</timestamp>
<status>
<gp:geopriv>
<gp:location-info>
<cl:civilAddress>
<cl:country>US</cl:country>
<cl:A1>Illinois</cl:A1>
<cl:A3>Chicago</cl:A3>
<cl:HNO>250</cl:HNO>
<cl:PRD>South Upper</cl:PRD>
<cl:A6>Wacker</cl:A6>
<cl:STS>Drive</cl:STS>
<cl:PC>60606</cl:PC>
<cl:NAM>Venice Cafe</cl:NAM>
<cl:FLR>1</cl:FLR>
<cl:civilAddress>
<method>dhcp</method>
<method>802.11</method>
<provided-by>www.t-mobile.com</provided-by/>
</gp:location-info>
<gp:usage-rules>
<gp:retransmission-allowed>no</gp:retransmission-allowed>
<gp:retention-expiry>2005-11-13T14:57:29Z</gp:retention-
expiry>
</gp:usage-rules>
</gp:geopriv>
</status>
</tuple>
</presence>
--boundary1--
8.4 UA-to-UA Location Conveyance Using PUBLISH
** This section could not be completed before submission time and
will be completed shortly after IETF61. A thousand and one pardons.
Polk & Rosen [Page 27]
Internet Draft SIP Location Conveyance June 17th, 2005
8.5 UA-to-UA Location Conveyance Using SUBSCRIBE and NOTIFY
This section was not completed in time for the ID cut-off, thus all
text was removed until it can be completed. The authors apologize.
8.6 424 "Bad Location Information" Error Response
In the case that a user agent server or SIP Proxy detects an error
in a message containing location information specific to that
message body, a new 4XX level error needs to be sent. This document
creates the new error code:
424 (Bad Location Information)
This will provide the UAC with directed feedback about the status of
location information it sent to that UAS or Proxy. The UAC MAY
attempt to retry sending the message providing its location.
This new error code will be IANA registered.
An example flow of this scenario will be included in the next
version of this internet draft.
9. Special Considerations for Emergency Calls
When a Proxy Server knows to look for a location message body to
route an emergency call as in [ID-EMER-ARCH].
Emergency calls, which might be detected as detailed in [ID-SIP-
SOS], have special rules for conveyance of location:
1. An emergency call MUST have all LI available to the UA, if any,
sent with the INVITE, and subsequent UPDATE or reINVITE messages
as a PIDF-LO in a body
2. The LO must be protected with sips: unless the attempt to
establish hop-by-hop TLS connection fails and cannot reasonably
be established in a very short (less than a second) time. In
such a case, the LO SHOULD be sent without TLS ONLY for those
hops that failed to support TLS establishment.
3. User Agents MUST NOT use S/MIME
4. User Agents MUST include the <provided-by> element in the PIDF-LO
(if known) to give the PSAP an indication as to who is
responsible for providing the UA with its location information.
Polk & Rosen [Page 28]
Internet Draft SIP Location Conveyance June 17th, 2005
Proxies MUST NOT remove a location message body at any time. In the
case where the Proxy knows the location of the UAC and does not
detect the UAC's location information message body in the message
(or determines the LO is bad), the Proxy generates a new 4XX (Retry
Location Body) error message that includes a location information
message body for that UAC to include in the subsequent message. The
user agent MUST include this message body in the subsequent
emergency message.
In the <provided-by> element of the PIDF-LO, the Proxy MUST identify
itself as the source of this location information. The user agent
MUST NOT alter this field's value if received from a Proxy server.
If the UAS of the PSAP receives a SIP request with multiple location
objects, it must determine which to use, since more than one may be
present. This specification does not limit the number of LOs in a
message, even in session mode.
9.1 UA-to-Proxy Routing the Message with INVITE (secure)
When Alice signifies "sos@" [per 3], her UA must understand this
message MUST NOT use S/MIME for the message body, because this is an
emergency call - otherwise the message will not properly route to
the correct destination. Two definite possibilities will exist for
how this message flow will occur [note: the message flows are not
being defined here, they are defined in [ID-EMER-ARCH], but two are
shown here to show the messages themselves]. The first possibility
has Alice sending her INVITE to her first hop Proxy, which
recognizes the message as an emergency message. The Proxy knows to
look into the message bodies for the location body; determine where
Alice is and route the call to the appropriate PSAP. This is shown
in Figure 4A.
UA Alice Proxy PSAP
| INVITE [M1] | |
|------------------>| |
| | INVITE [M2] |
| |-------------------->|
| | 200 OK [M3] |
| |<--------------------|
| 200 OK [M4] | |
|<------------------| |
| ACK [M5] |
|---------------------------------------->|
| RTP |
|<=======================================>|
| |
Figure 4A. UA-PROXY with Location in INVITE
Polk & Rosen [Page 29]
Internet Draft SIP Location Conveyance June 17th, 2005
[M1 of Figure 4A]
INVITE sips:sos@atlanta.example.com SIP/2.0
Via: SIP/2.0/TLS pc33.atlanta.example.com
;branch=z9hG4bK74bf9
Max-Forwards: 70
From: Alice <sips:alice@atlanta.example.com>;tag=9fxced76sl
To: <sips:sos@atlanta.example.com>
Call-ID: 3848276298220188511@atlanta.example.com
CSeq: 31862 INVITE
Contact: <sips:alice@atlanta.example.com>
Content-Type: multipart/mixed; boundary=boundary1
Content-Length: ...
--boundary1
Content-Type: application/sdp
v=0
o=alice 2890844526 2890844526 IN IP4 atlanta.example.com
c=IN IP4 10.1.3.33
t=0 0
m=audio 49172 RTP/AVP 0 4 18
a=rtpmap:0 PCMU/8000
--boundary1
Once the Proxy receives M1 and recognizes it as an emergency INVITE
Request, this proxy knows to look into the message body for a
location body part to determine the location of the UAC in order to
match the location to an PSAP. Once this look-up occurs, the
message is sent directly to the PSAP (in message [M2]).
[M2 of Figure 4A] - Proxy has determined when to send message
INVITE sips:sos@192.168.10.20 SIP/2.0
Via: SIP/2.0/TLS pc33.atlanta.example.com
;branch=z9hG4bK74bf9
Max-Forwards: 69
From: Alice <sips:alice@atlanta.example.com>;tag=9fxced76sl
To: <sips:sos@atlanta.example.com>
Call-ID: 3848276298220188511@atlanta.example.com
CSeq: 31862 INVITE
Contact: <sips:alice@atlanta.example.com>
Content-Type: multipart/mixed; boundary=boundary1
Content-Length: ...
--boundary1
Content-Type: application/sdp
v=0
o=alice 2890844526 2890844526 IN IP4 atlanta.example.com
Polk & Rosen [Page 30]
Internet Draft SIP Location Conveyance June 17th, 2005
c=IN IP4 10.1.3.33
t=0 0
m=audio 49172 RTP/AVP 0 4 18
a=rtpmap:0 PCMU/8000
--boundary1
Content-type: application/cpim-pidf+xml
<?xml version="1.0" encoding="UTF-8"?>
<presence xmlns="urn:ietf:params:xml:ns:pidf"
xmlns:gp="urn:ietf:params:xml:ns:pidf:geopriv10"
xmlns:gml="urn:opengis:specification:gml:schema-
xsd:feature:v3.0"
entity="pres:alice@atlanta.example.com">
<tuple id="sg89ae">
<timestamp>2005-11-11T08:57:29Z</timestamp>
<status>
<gp:geopriv>
<gp:location-info>
<cl:civilAddress>
<cl:country>US</cl:country>
<cl:A1>Illinois</cl:A1>
<cl:A3>Chicago</cl:A3>
<cl:HNO>233</cl:HNO>
<cl:PRD>South</cl:PRD>
<cl:A6>Wacker</cl:A6>
<cl:STS>Drive</cl:STS>
<cl:PC>60606</cl:PC>
<cl:LMK>Sears Tower</cl:LMK>
<cl:FLR>1</cl:FLR>
<cl:civilAddress>
<method>dhcp</method>
<method>802.11</method>
<provided-by>www.t-mobile.com</provided-by/>
</gp:location-info>
<gp:usage-rules>
<gp:retransmission-allowed>no</gp:retransmission-allowed>
<gp:retention-expiry>2005-11-13T14:57:29Z</gp:retention-
expiry>
</gp:usage-rules>
</gp:geopriv>
</status>
</tuple>
</presence>
--boundary1--
The second probability in message flows is in Figure 4B. in which
the first hop Proxy1 does not either: understand location, or does
not know where the appropriate PSAP is to route the message to. In
either case, that Proxy(1) forwards the message to another Proxy(2)
Polk & Rosen [Page 31]
Internet Draft SIP Location Conveyance June 17th, 2005
for proper message routing ([ID-EMER-ARCH] talks to how this
occurs).
UA Alice Proxy1 Proxy2 PSAP
| INVITE [M1] | | |
|------------>| | |
| | INVITE [M2] | |
| |------------>| |
| | | INVITE [M3] |
| | |------------>|
| | | 200 OK [M4] |
| | |<------------|
| | 200 OK [M5] | |
| |<------------| |
| 200 OK [M6] | | |
|<------------| | |
| ACK [M7] |
|---------------------------------------->|
| RTP |
|<=======================================>|
| |
Figure 4B. UA-PROXY with Location in INVITE
In message flows similar to 4A and/or 4B, the Record-Route header
could be added by the proxies, this is OPTIONAL in usage and left to
other documents to refine.
In the case of an identifiable emergency call, something that cannot
happen is for any Proxy to Challenge [per RFC3261] the INVITE
message. In fact, while usage of the SIPS URI is encouraged and
SHOULD be used, it MUST NOT be mandatory for successful message
routing. If the first SIPS INVITE fails for security property
reasons, the second attempt by Alice (in these examples) MUST be
allowed to be in the clear, not challenged, and routed properly.
Security mechanisms MUST NOT fail any call attempt, and if they do
once, they MUST NOT be mandatory for the subsequent attempt for a
successful session set-up to an PSAP. The results of this are that
the Proxy that failed the first attempt for security reasons MUST be
aware of this failed attempt for the subsequent attempt that MUST
process without failure a second time. It must be assumed that the
INVITE in any instance is considered "well formed".
The remaining messages in both 4A and 4B are not included at this
time. If the working groups wants these added, they will be in the
next revision of this document.
9.1.1 UA-to-Proxy Routing the Message with INVITE (unsecure)
Polk & Rosen [Page 32]
Internet Draft SIP Location Conveyance June 17th, 2005
Below can be considered the initial unsecure INVITE M1 from Figures
4A and 4A, or the second attempt message to an initial message that
was failed by a Proxy. This version of M1 is not using any security
measures and is using the civic format message body that is the
identical location to the previous example.
[Message M1 from Figure 4A]
INVITE sip:sos@atlanta.example.com SIP/2.0
Via: SIP/2.0/TCP pc33.atlanta.example.com
;branch=z9hG4bK74bf9
Max-Forwards: 70
From: Alice <sip:alice@atlanta.example.com>;tag=9fxced76sl
To: <sip:sos@atlanta.example.com>
Call-ID: 3848276298220188511@atlanta.example.com
CSeq: 31862 INVITE
Contact: <sip:alice@atlanta.example.com>
Content-Type: multipart/mixed; boundary=boundary1
Contact-Length: ...
--boundary1
Content-Type: application/sdp
v=0
o=alice 2890844526 2890844526 IN IP4 atlanta.example.com
c=IN IP4 10.1.3.33
t=0 0
m=audio 49172 RTP/AVP 0 4 18
a=rtpmap:0 PCMU/8000
--boundary1
Content-type: application/cpim-pidf+xml
<?xml version="1.0" encoding="UTF-8"?>
<presence xmlns="urn:ietf:params:xml:ns:pidf"
xmlns:gp="urn:ietf:params:xml:ns:pidf:geopriv10"
xmlns:gml="urn:opengis:specification:gml:schema-
xsd:feature:v3.0"
entity="pres:alice@atlanta.example.com">
<tuple id="sg89ae">
<timestamp>2005-11-11T08:57:29Z</timestamp>
<status>
<gp:geopriv>
<gp:location-info>
<cl:civilAddress>
<cl:country>US</cl:country>
<cl:A1>Illinois</cl:A1>
<cl:A3>Chicago</cl:A3>
<cl:HNO>233</cl:HNO>
<cl:PRD>South</cl:PRD>
<cl:A6>Wacker</cl:A6>
Polk & Rosen [Page 33]
Internet Draft SIP Location Conveyance June 17th, 2005
<cl:STS>Drive</cl:STS>
<cl:PC>60606</cl:PC>
<cl:LMK>Sears Tower</cl:LMK>
<cl:FLR>1</cl:FLR>
<cl:civilAddress>
<method>dhcp</method>
<method>802.11</method>
<provided-by>www.t-mobile.com</provided-by/>
</gp:location-info>
<gp:usage-rules>
<gp:retransmission-allowed>no</gp:retransmission-allowed>
<gp:retention-expiry>2005-11-13T14:57:29Z</gp:retention-
expiry>
</gp:usage-rules>
</gp:geopriv>
</status>
</tuple>
</presence>
--boundary1--
9.2 UA-to-Proxy Routing with UPDATE
If the previous example of the location contained in the INVITE were
to account for the movement of Alice (and her UA) before the PSAP
responded with a 200 OK, the UPDATE method is the appropriate SIP
Request Method to use to update the proxies and PSAP personnel that
Alice has moved locations from where she initially made her set-up
request.
In this scenario (shown in the call flow of Figure 5A), Alice
sending the UPDATE message here may cause the Proxy to CANCEL an
existing pending INVITE Request, and retransmit INVITE to a NEW
PSAP(2), for example, if she walked across a street into a new PSAP
coverage area. The Proxy MUST remain transaction stateful in order
to be aware of the 200 OK Response from PSAP1. Upon receiving the
UPDATE from Alice and analyzing the location provided by the message
looking for a location change, either forwarding that message to
PSAP1 if the change is still within PSAP1's coverage area, or
deciding to forward a message to another PSAP covering where Alice
is now (PSAP2 in this case) with her new location. If the latter
change in destinations is required, the Proxy MUST CANCEL the
pending INVITE to PSAP1 (with a 487 "terminated request" being the
specified response).
SIPS SHOULD be used by Alice initially. Upon any failure of the
initial Request, Alice's UA MUST decide to send the new message
without SIPS.
Polk & Rosen [Page 34]
Internet Draft SIP Location Conveyance June 17th, 2005
UA Alice Proxy PSAP1 PSAP2
| INVITE [M1] | | |
|---------------->| | |
| | INVITE [M2] | |
| |------------>| |
| 183 SP [M3] | | |
|<----------------| | |
| PRACK [M4] | | |
|---------------->| | |
| 200 OK (PR)[M5] | | |
|<----------------| | |
| UPDATE [M6] | | |
|---------------->| | |
| 200 OK (UP)[M7] | | |
|<----------------| | |
| | CANCEL [M8] | |
| |------------>| |
| | 487 [M9] | |
| |<------------| |
| | INVITE [M10] |
| |-------------------------->|
| | 200 OK (INV) [M11] |
| |<--------------------------|
|200 OK (INV)[M12]| |
|<----------------| |
| ACK [M13] |
|-------------------------------------------->|
| RTP |
|<===========================================>|
| |
Figure 5A. UA-PROXY with Location in UPDATE
** see new open issue #9 for the problems with messages 8 through 10
** of the above flow.
9.2.1 UA-to-Proxy Routing the Message with UPDATE (secure)
INVITE sip:sos@atlanta.example.com SIP/2.0
Via: SIP/2.0/TCP pc33.atlanta.example.com
;branch=z9hG4bK74bf9
Max-Forwards: 70
From: Alice <sip:alice@atlanta.example.com>;tag=9fxced76sl
To: <sip:sos@atlanta.example.com>
Call-ID: 3848276298220188511@atlanta.example.com
CSeq: 31862 INVITE
Contact: <sip:alice@atlanta.example.com>
Content-Type: multipart/mixed; boundary=boundary1
Contact-Length: ...
Polk & Rosen [Page 35]
Internet Draft SIP Location Conveyance June 17th, 2005
--boundary1
Content-Type: application/sdp
v=0
o=alice 2890844526 2890844526 IN IP4 atlanta.example.com
c=IN IP4 10.1.3.33
t=0 0
m=audio 49172 RTP/AVP 0 4 18
a=rtpmap:0 PCMU/8000
--boundary1
Content-type: application/cpim-pidf+xml
<?xml version="1.0" encoding="UTF-8"?>
<presence xmlns="urn:ietf:params:xml:ns:pidf"
xmlns:gp="urn:ietf:params:xml:ns:pidf:geopriv10"
xmlns:gml="urn:opengis:specification:gml:schema-
xsd:feature:v3.0"
entity="pres:alice@atlanta.example.com">
<tuple id="sg89ae">
<timestamp>2005-11-11T08:57:29Z</timestamp>
<status>
<gp:geopriv>
<gp:location-info>
<cl:civilAddress>
<cl:country>US</cl:country>
<cl:A1>Illinois</cl:A1>
<cl:A3>Chicago</cl:A3>
<cl:HNO>233</cl:HNO>
<cl:PRD>South</cl:PRD>
<cl:A6>Wacker</cl:A6>
<cl:STS>Drive</cl:STS>
<cl:PC>60606</cl:PC>
<cl:LMK>Sears Tower</cl:LMK>
<cl:FLR>1</cl:FLR>
<cl:civilAddress>
<method>dhcp</method>
<method>802.11</method>
<provided-by>www.cisco.com</provided-by/>
</gp:location-info>
<gp:usage-rules>
<gp:retransmission-allowed>no</gp:retransmission-allowed>
<gp:retention-expiry>2005-11-13T14:57:29Z</gp:retention-
expiry>
</gp:usage-rules>
</gp:geopriv>
</status>
</tuple>
</presence>
--boundary1--
Polk & Rosen [Page 36]
Internet Draft SIP Location Conveyance June 17th, 2005
Alice moves locations (with her UA detecting the movement), causing
her UA to generate an UPDATE message ([M5] of Figure 3) prior to her
UA receiving a final response from the PSAP. In this case, Alice
has walked across the South Wacker Drive to another building. Here
is that message:
[M5 UPDATE to PSAP]
UPDATE sips:bob@biloxi.example.com/TCP SIP/2.0
Via: SIP/2.0/TLS pc33.atlanta.example.com
;branch=z9hG4bK776asdhds
Max-Forwards: 70
From: Alice <sip:alice@atlanta.example.com>;tag=9fxced76sl
To: <sip:sos@atlanta.example.com>
Call-ID: 3848276298220188511@atlanta.example.com
CSeq: 10187 UPDATE
Contact: <sip:alice@atlanta.example.com>
Content-Type: multipart/mixed; boundary=boundary1
Contact-Length: ...
--boundary1
Content-Type: application/sdp
v=0
o=alice 2890844526 2890844526 IN IP4 atlanta.example.com
c=IN IP4 10.1.3.33
t=0 0
m=audio 49172 RTP/AVP 0 4 18
a=rtpmap:0 PCMU/8000
--boundary1
Content-type: application/cpim-pidf+xml
<?xml version="1.0" encoding="UTF-8"?>
<presence xmlns="urn:ietf:params:xml:ns:pidf"
xmlns:gp="urn:ietf:params:xml:ns:pidf:geopriv10"
xmlns:gml="urn:opengis:specification:gml:schema-
xsd:feature:v3.0"
entity="pres:alice@atlanta.example.com">
<tuple id="sg89ae">
<timestamp>2005-11-11T08:57:29Z</timestamp>
<status>
<gp:geopriv>
<gp:location-info>
<cl:civilAddress>
<cl:country>US</cl:country>
<cl:A1>Illinois</cl:A1>
<cl:A3>Chicago</cl:A3>
<cl:HNO>250</cl:HNO>
<cl:PRD>South Upper</cl:PRD>
<cl:A6>Wacker</cl:A6>
<cl:STS>Drive</cl:STS>
Polk & Rosen [Page 37]
Internet Draft SIP Location Conveyance June 17th, 2005
<cl:PC>60606</cl:PC>
<cl:NAM>Venice Cafe</cl:NAM>
<cl:FLR>1</cl:FLR>
<cl:civilAddress>
<method>dhcp</method>
<method>802.11</method>
<provided-by>www.t-mobile.com</provided-by/>
</gp:location-info>
<gp:usage-rules>
<gp:retransmission-allowed>no</gp:retransmission-allowed>
<gp:retention-expiry>2005-11-13T14:57:29Z</gp:retention-
expiry>
</gp:usage-rules>
</gp:geopriv>
</status>
</tuple>
</presence>
--boundary1--
9.2.2 UA-to-Proxy Routing the Message with UPDATE (unsecure)
left blank for now
9.3 425 "Retry Location Body" Error Response
In the case that a SIP Proxy detects an error in a SIP message
containing location information specific to that message body and
has the location of that UAC locally, a new 4XX level error needs to
be sent back to the UAC containing a new Location Object message
body of the UAC as the SIP intermediary understands where the UAC is
with the intent of the UAC including this LO message body in a
subsequent message to the originally addressed UAS. This document
creates the new error code:
425 (Retry Location Body)
The UAC MUST include the SIP intermediary provided LO message body
in the retransmission of the rejected message to the original UAS if
the UAC attempts this communication. User agents may conclude they
have already supplied a proper LO in the rejected request. That LO
can be resent, but the intermediary supplied LO MUST be included as
well.
This new error code will be IANA registered.
An example flow of this scenario will be included in the next
version of this internet draft.
Polk & Rosen [Page 38]
Internet Draft SIP Location Conveyance June 17th, 2005
10. Meeting RFC3693 Requirements
Section 7.2 of [RFC3693] details the requirements of a "using
protocol". They are:
Req. 4. The using protocol has to obey the privacy and security
instructions coded in the Location Object and in the
corresponding Rules regarding the transmission and storage of the
LO.
This document requires, in Section 7, that SIP entities sending or
receiving location MUST obey such instructions.
Req. 5. The using protocol will typically facilitate that the keys
associated with the credentials are transported to the respective
parties, that is, key establishment is the responsibility of the
using protocol.
[RFC3261] and the documents it references define the key establish
mechanisms.
Req. 6. (Single Message Transfer) In particular, for tracking of
small target devices, the design should allow a single
message/packet transmission of location as a complete
transaction.
This document specifies that the LO be contained in the body of a
single message.
11. Current Known Open issues
This is a list of open issues that have not yet been addressed to
conclusion:
1) Still have not determined how a SIP entity can request location
to be delivered in a certain format (civil vs. coordinate).
11.1 New Open Issues
These are new open issues to be addressed within this document or
the topics/areas dropped from consideration:
1) May add a section for end-to-middle in a services model
12. 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 or TLS). In cases
Polk & Rosen [Page 39]
Internet Draft SIP Location Conveyance June 17th, 2005
where a session set-up is routed based on the location of the UAC
initiating the session or SIP MESSAGE, securing the location with an
end-to-end mechanism such as S/MIME is problematic.
13. IANA Considerations
This section defines two new 4XX error response codes within the
sip-parameters section of IANA. [NOTE: RFC XXXX denotes this
document.
13.1 IANA Registration for Response Code 4XX
Reference: RFC-XXXX (this document)
Response code: 424
Default reason phrase: Bad Location Information
13.2 IANA Registration for Response Code 4XX
Reference: RFC-XXXX (this document)
Response code: 425
Default reason phrase: Retry Location Body
14. Acknowledgements
To Dave Oran for helping to shape this idea. To Jon Peterson and
Dean Willis on guidance of the effort. To Henning Schulzrinne,
Jonathan Rosenberg, Dick Knight, Mike Hammer and Keith Drage for
constructive feedback.
15. References
15.1 References - Normative
[RFC3261] J. Rosenberg, H. Schulzrinne, G. Camarillo, A. Johnston, J.
Peterson, R. Sparks, M. Handley, and E. Schooler, "SIP:
Session Initiation Protocol", RFC 3261, May 2002.
[RFC2119] S. Bradner, "Key words for use in RFCs to Indicate
Requirement Levels", RFC 2119, March 1997
[ID-SIP-SOS] H. Schulzrinne, "draft-ietf-sipping-sos-00.txt", Internet
Draft, Feb 2004, Work in progress
[RFC3428] B. Campbell, Ed., J. Rosenberg, H. Schulzrinne, C. Huitema,
D. Gurle, "Session Initiation Protocol (SIP) Extension for
Instant Messaging" , RFC 3428, December 2002
[RFC3825] J. Polk, J. Schnizlein, M. Linsner, "Dynamic Host
Polk & Rosen [Page 40]
Internet Draft SIP Location Conveyance June 17th, 2005
Configuration Protocol Option for Coordinate-based Location
Configuration Information", RFC 3825, July 2004
[ID-CIVIC] H. Schulzrinne, "draft-ietf-geopriv-dhcp-civic-06.txt",
Internet Draft, May 05, Work in progress
[RFC3693] J. Cuellar, J. Morris, D. Mulligan, J. Peterson. J. Polk,
"Geopriv Requirements", RFC 3693, February 2004
[RFC3311] J. Rosenberg, "The Session Initiation Protocol (SIP) UPDATE
Method", RFC 3311, October 2002
[RFC3903] Niemi, A., "Session Initiation Protocol (SIP) Extension
for Event State Publication", RFC 3903, October 2004.
[ID-PIDF-LO] J. Peterson, "draft-ietf-geopriv-pidf-lo-03", Internet
Draft, Sept 2004, work in progress
[RFC3264] J. Rosenberg, H. Schulzrinne, "The Offer/Answer Model with
Session Description Protocol", RFC 3264, June 2002
[RFC3515] R. Sparks, "The Session Initiation Protocol (SIP) Refer
Method", RFC 3515, April 2003
[RFC3265] Roach, A., "Session Initiation Protocol (SIP)-Specific
Event Notification", RFC 3265, June 2002.
16.1 References - Informative
[ID-End-Mid-Sec] "Requirements for End to Middle Security in SIP",
draft-ietf-sipping-e2m-sec-reqs-03.txt, Internet Draft, June
2004, work in progress,
[ID-Sess-Pol] J. Rosenberg, "Requirements for Session Policy for the
Session Initiation Protocolö, draft-ietf-sipping-session-
policy-req-00", Internet Draft, June, 2003, "work in
progress"
[ID-EMER-ARCH] H. Schulzrinne, B. Rosen, "draft-schulzrinne-sipping-
emergency-arch", Internet Draft, Feb 2004, work in progress
16. Author Information
James M. Polk
Cisco Systems
2200 East President George Bush Turnpike 33.00111N
Richardson, Texas 75082 USA 96.68142W
jmpolk@cisco.com
Polk & Rosen [Page 41]
Internet Draft SIP Location Conveyance June 17th, 2005
Brian Rosen 40.4N
br@brianrosen.net 80.0W
Appendix A. Additional stuff
This section is coming in the next release.
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Copyright Statement
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Polk & Rosen [Page 42]
Internet Draft SIP Location Conveyance June 17th, 2005
Acknowledgment
Funding for the RFC Editor function is currently provided by the
Internet Society.
The Expiration date for this Internet Draft is:
December 17th, 2005
Polk & Rosen [Page 43]
| PAFTECH AB 2003-2026 | 2026-04-21 23:21:51 |