draft-ietf-geopriv-sip-lo-retransmission-01.txt   draft-ietf-geopriv-sip-lo-retransmission-02.txt 
Internet Engineering Task Force J. Peterson Internet Engineering Task Force J. Peterson
Internet-Draft NeuStar, Inc. Internet-Draft NeuStar, Inc.
Intended status: Informational T. Hardie Intended status: Informational T. Hardie
Expires: April 29, 2009 Qualcomm Expires: September 10, 2009 Qualcomm
J. Morris J. Morris
CDT CDT
October 26, 2008 March 9, 2009
Implications of 'retransmission-allowed' for SIP Location Conveyance Implications of 'retransmission-allowed' for SIP Location Conveyance
draft-ietf-geopriv-sip-lo-retransmission-01 draft-ietf-geopriv-sip-lo-retransmission-02
Status of this Memo Status of this Memo
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Abstract Abstract
This document explores an ambiguity in the interpretation of the This document explores an ambiguity in the interpretation of the
<retransmission-allowed> element of the Presence Information Data <retransmission-allowed> element of the Presence Information Data
Format for Location Objects (PIDF-LO) in cases where PIDF-LO is Format for Location Objects (PIDF-LO) in cases where PIDF-LO is
conveyed by the Session Initiation Protocol (SIP). It provides conveyed by the Session Initiation Protocol (SIP). It provides
recommendations for how the SIP location conveyance mechanism should recommendations for how the SIP location conveyance mechanism should
adapt to these ambiguities. adapt to these ambiguities.
Documents standardizing the SIP location conveyance mechanisms will Documents standardizing the SIP location conveyance mechanisms will
be standards-track documents processed according to the usual SIP be standards-track documents processed according to the usual SIP
process. This document is intended primarily to provide the SIP process. This document is intended primarily to provide the SIP
working group with a statement of the consensus of the GEOPRIV working group with a statement of the consensus of the GEOPRIV
working group on this topic. It secondarily provides tutorial working group on this topic. It secondarily provides tutorial
information on the problem space for the general reader. information on the problem space for the general reader.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
2. Problem Statement . . . . . . . . . . . . . . . . . . . . . . 3 2. Problem Statement . . . . . . . . . . . . . . . . . . . . . . 4
3. Recommendation . . . . . . . . . . . . . . . . . . . . . . . . 5 3. Recommendation . . . . . . . . . . . . . . . . . . . . . . . . 6
3.1. Goals . . . . . . . . . . . . . . . . . . . . . . . . . . 6 3.1. Goals . . . . . . . . . . . . . . . . . . . . . . . . . . 7
3.2. Core Semantics . . . . . . . . . . . . . . . . . . . . . . 6 3.2. Core Semantics . . . . . . . . . . . . . . . . . . . . . . 7
3.3. Limiting Access . . . . . . . . . . . . . . . . . . . . . 6 3.3. Limiting Access . . . . . . . . . . . . . . . . . . . . . 7
3.3.1. Limiting Access using Public Key Encryption . . . . . 6 3.3.1. Limiting Access using Public Key Encryption . . . . . 7
3.3.2. Limiting Access using Location-by-Reference . . . . . 7 3.3.2. Limiting Access using Location-by-Reference . . . . . 8
3.3.3. Refraining from Including Location Information . . . . 8 3.3.3. Refraining from Including Location Information . . . . 9
3.4. Choosing Among the Available Mechanisms . . . . . . . . . 8 3.4. Choosing Among the Available Mechanisms . . . . . . . . . 9
3.5. Indicating Permission to Use Location-Based Routing in 3.5. Indicating Permission to Use Location-Based Routing in
SIP . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 SIP . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
3.6. Behavior of Back-to-Back User Agents . . . . . . . . . . . 10 3.6. Behavior of Back-to-Back User Agents . . . . . . . . . . . 11
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 11 4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 12
5. Security Considerations . . . . . . . . . . . . . . . . . . . 11 5. Security Considerations . . . . . . . . . . . . . . . . . . . 12
6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 11 6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 12
7. Informative References . . . . . . . . . . . . . . . . . . . . 11 7. Informative References . . . . . . . . . . . . . . . . . . . . 12
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 11 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 12
Intellectual Property and Copyright Statements . . . . . . . . . . 13
1. Introduction 1. Introduction
The Presence Information Data Format for Location Objects (PIDF-LO The Presence Information Data Format for Location Objects (PIDF-LO
[RFC4119]) carries both location information (LI) and policy [RFC4119]) carries both location information (LI) and policy
information set by the Rule Maker, as is stipulated in [RFC3693]. information set by the Rule Maker, as is stipulated in [RFC3693].
The policy carried along with LI allows the Rule Maker to restrict, The policy carried along with LI allows the Rule Maker to restrict,
among other things, the duration for which LI will be retained by among other things, the duration for which LI will be retained by
recipients and the redistribution of LI by recipients. recipients and the redistribution of LI by recipients.
skipping to change at page 10, line 21 skipping to change at page 11, line 21
reference or by value, insert a "Location-Routing-Allowed header if reference or by value, insert a "Location-Routing-Allowed header if
one is not already present. If one is present, it should not be one is not already present. If one is present, it should not be
over-ridden by the SIP element inserting the location. over-ridden by the SIP element inserting the location.
We recommend that any SIP element not the originator of a message and We recommend that any SIP element not the originator of a message and
not inserting a location be enjoined from inserting a "Location- not inserting a location be enjoined from inserting a "Location-
Routing-Allowed" header. Routing-Allowed" header.
3.6. Behavior of Back-to-Back User Agents 3.6. Behavior of Back-to-Back User Agents
While the behavior of back-to-back user agents (B2BUAs) is outside Back-to-back user agent behavior is often difficult to proscribe.
the scope of SIP standardization, there are nevertheless ways that a There are many uses of B2BUAs, and the rules that apply to location
B2BUA might approach conveyed location information and the would depend on the actual use case. This section suggests what any
<retransmission-allowed> flag that will have better results than SIP mechanism arising from this document might wish to consider with
others. This section documents the consequences of B2BUA behavior regard to B2BUA behavior.
interacting with <retransmission-allowed>.
Typically, B2BUAs are described as terminating one session and In most uses of B2BUAs, they act as a simple intermediary between the
originating a new one. From that perspective, a B2BUA receiving LI nominal originating and nominal terminating UAs, that is, a proxy
on one of its "backs" might treat itself as terminating the flow of that does something proxies aren't allowed to do. In such cases, the
information and thus view itself as a recipient for the purposes of B2BUA must conform to any new routing-allowed mechanism if it chooses
<retransmission-allowed>. In that case, it should originate a new an outgoing route. As this document advises proxies,
information flow containing that LI by value in the other direction <retransmission-allowed> does not apply to the B2BUA in this case and
only if the PIDF-LO it receives permitted it (i.e. if the B2BUA must copy the LI, the new routing-allowed and existing
<retransmission-allowed> is set to 'yes'). If the PIDF-LO it <retransmission-allowed> values.
receives is encrypted, it can pass it onward with the understanding
that a recipient capable of decrypting it is authorized; the B2BUA
does not seem to be a recipient in this instance.
Note that this case is also easier to handle using the location-by- Where the B2BUA in fact does act as an endpoint (terminating the
reference model. Since the passing of location-by-reference does not session and originating a different session), <retransmission-
properly include the location itself, it can pass a location-by- allowed> applies to it, and it must not copy location if
reference pointer in the new direction with the understanding that <retransmission-allowed> is "no". If it chooses a route for the
the dereferencing protocol handles the determination of whether those outgoing leg, any new routing-allowed mechanism applies to it.
dereferencing the location are authorized recipients or not.
If both sides of a B2BUA speak SIP, note that failing to copy any Encryption lets the originator control who, including B2BUAs, is
"Location-Routing-Allowed" header value found in the input flow when allowed to see location. On the other hand, using encryption with LI
it re-originates the flow will neglect the policies of the Rule which is needed for routing is problematic, in that it is often
Maker. difficult to know in advance which elements do location based
routing. Similarly, using location-by-reference instead of location-
by-value provides additional control to the originator over B2BUA
behavior by controlling who can dereference. See Section 3.4 for
more guidance on this trade off.
4. IANA Considerations 4. IANA Considerations
This memo includes no request to IANA. This memo includes no request to IANA.
5. Security Considerations 5. Security Considerations
The privacy and security implications of distributing location The privacy and security implications of distributing location
information are the fundamental subject of this document. information are the fundamental subject of this document.
6. Acknowledgements 6. Acknowledgements
James Polk provided a series of questions regarding the specifics of James Polk provided a series of questions regarding the specifics of
the Location-Routing-Allowed mechanism, and this resulted in the the Location-Routing-Allowed mechanism, and this resulted in the
recommendations in Section 3.4. recommendations in Section 3.4. Thanks to Brian Rosen for the text
on B2BUAs.
7. Informative References 7. Informative References
[I-D.ietf-sip-location-conveyance] [I-D.ietf-sip-location-conveyance]
Polk, J. and B. Rosen, "Location Conveyance for the Polk, J. and B. Rosen, "Location Conveyance for the
Session Initiation Protocol", Session Initiation Protocol",
draft-ietf-sip-location-conveyance-10 (work in progress), draft-ietf-sip-location-conveyance-13 (work in progress),
September 2008. March 2009.
[RFC3261] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston, [RFC3261] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston,
A., Peterson, J., Sparks, R., Handley, M., and E. A., Peterson, J., Sparks, R., Handley, M., and E.
Schooler, "SIP: Session Initiation Protocol", RFC 3261, Schooler, "SIP: Session Initiation Protocol", RFC 3261,
June 2002. June 2002.
[RFC3693] Cuellar, J., Morris, J., Mulligan, D., Peterson, J., and [RFC3693] Cuellar, J., Morris, J., Mulligan, D., Peterson, J., and
J. Polk, "Geopriv Requirements", RFC 3693, February 2004. J. Polk, "Geopriv Requirements", RFC 3693, February 2004.
[RFC4119] Peterson, J., "A Presence-based GEOPRIV Location Object [RFC4119] Peterson, J., "A Presence-based GEOPRIV Location Object
skipping to change at page 13, line 4 skipping to change at line 525
Email: jon.peterson@neustar.biz Email: jon.peterson@neustar.biz
Ted Hardie Ted Hardie
Qualcomm Qualcomm
Email: hardie@qualcomm.com Email: hardie@qualcomm.com
John Morris John Morris
CDT CDT
Email: jmorris@cdt.org Email: jmorris@cdt.org
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