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Implications of 'retransmission-allowed' for SIP Location Conveyance
RFC 5606

Network Working Group                                        J. Peterson
Request for Comments: 5606                                 NeuStar, Inc.
Category: Informational                                        T. Hardie
                                                                Qualcomm
                                                               J. Morris
                                                                     CDT
                                                             August 2009

  Implications of 'retransmission-allowed' for SIP Location Conveyance

Abstract

   This document explores an ambiguity in the interpretation of the
   <retransmission-allowed> element of the Presence Information Data
   Format for Location Objects (PIDF-LO) in cases where PIDF-LO is
   conveyed by the Session Initiation Protocol (SIP).  It provides
   recommendations for how the SIP location conveyance mechanism should
   adapt to this ambiguity.

   Documents standardizing the SIP location conveyance mechanisms will
   be Standards-Track documents processed according to the usual SIP
   process.  This document is intended primarily to provide the SIP
   working group with a statement of the consensus of the GEOPRIV
   working group on this topic.  It secondarily provides tutorial
   information on the problem space for the general reader.

Status of This Memo

   This memo provides information for the Internet community.  It does
   not specify an Internet standard of any kind.  Distribution of this
   memo is unlimited.

Copyright Notice

   Copyright (c) 2009 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents in effect on the date of
   publication of this document (http://trustee.ietf.org/license-info).
   Please review these documents carefully, as they describe your rights
   and restrictions with respect to this document.

   This document may contain material from IETF Documents or IETF
   Contributions published or made publicly available before November
   10, 2008.  The person(s) controlling the copyright in some of this
   material may not have granted the IETF Trust the right to allow

Peterson, et al.             Informational                      [Page 1]
RFC 5606                Location Retransmission              August 2009

   modifications of such material outside the IETF Standards Process.
   Without obtaining an adequate license from the person(s) controlling
   the copyright in such materials, this document may not be modified
   outside the IETF Standards Process, and derivative works of it may
   not be created outside the IETF Standards Process, except to format
   it for publication as an RFC or to translate it into languages other
   than English.

Table of Contents

   1. Introduction ....................................................2
   2. Problem Statement ...............................................3
   3. Recommendation ..................................................5
      3.1. Goals ......................................................5
      3.2. Core Semantics .............................................5
      3.3. Limiting Access ............................................6
           3.3.1. Limiting Access Using Public Key Encryption .........6
           3.3.2. Limiting Access Using Location-by-Reference .........7
           3.3.3. Refraining from Including Location Information ......8
      3.4. Choosing among the Available Mechanisms ....................8
      3.5. Indicating Permission to Use Location-Based Routing
           in SIP .....................................................8
      3.6. Behavior of Back-to-Back User Agents ......................10
   4. Security Considerations ........................................10
   5. Acknowledgements ...............................................10
   6. Informative References .........................................11

1.  Introduction

   The Presence Information Data Format for Location Objects (PIDF-LO
   [RFC4119]) carries both location information (LI) and policy
   information set by the Rule Maker, as is stipulated in [RFC3693].
   The policy carried along with LI allows the Rule Maker to restrict,
   among other things, the duration for which LI will be retained by
   recipients and the redistribution of LI by recipients.

   The Session Initiation Protocol [RFC3261] is one proposed Using
   Protocol for PIDF-LO.  The conveyance of PIDF-LO within SIP is
   specified in [LOC-CONVEY].  The common motivation for providing LI in
   SIP is to allow location to be considered in routing the SIP message.
   One example use case would be emergency services, in which the

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