The Presence-Specific Static Dictionary for Signaling Compression (Sigcomp)
RFC 5112

 
Document Type RFC - Proposed Standard (January 2008; No errata)
Was draft-garcia-simple-presence-dictionary (individual in rai area)
Last updated 2013-03-02
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IESG IESG state RFC 5112 (Proposed Standard)
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Responsible AD Jon Peterson
Send notices to miguel.an.garcia@nokia.com
Network Working Group                                   M. Garcia-Martin
Request for Comments: 5112                        Nokia Siemens Networks
Category: Standards Track                                   January 2008

                The Presence-Specific Static Dictionary
                  for Signaling Compression (Sigcomp)

Status of This Memo

   This document specifies an Internet standards track protocol for the
   Internet community, and requests discussion and suggestions for
   improvements.  Please refer to the current edition of the "Internet
   Official Protocol Standards" (STD 1) for the standardization state
   and status of this protocol.  Distribution of this memo is unlimited.

Abstract

   The Session Initiation Protocol (SIP) is a text-based protocol for
   initiating and managing communication sessions.  The protocol is
   extended by the SIP-events notification framework to provide
   subscriptions and notifications of SIP events.  One example of such
   event notification mechanism is presence, which is expressed in XML
   documents called presence documents.  SIP can be compressed by using
   Signaling Compression (SigComp), which is enhanced by using the SIP/
   Session Description Protocol (SDP) dictionary to achieve better
   compression rates.  However, the SIP/SDP dictionary is not able to
   increase the compression factor of (typically lengthy) presence
   documents.  This memo defines the presence-specific static dictionary
   that SigComp can use in order to compress presence documents to
   achieve higher efficiency.  The dictionary is compression-algorithm
   independent.

Garcia-Martin               Standards Track                     [Page 1]
RFC 5112            Presence Dictionary for SIGCOMP         January 2008

Table of Contents

   1. Introduction ....................................................2
   2. Terminology .....................................................3
   3. Design Considerations ...........................................3
   4. Binary Representation of the Presence-Specific Static
      Dictionary ......................................................5
   5. Security Considerations ........................................12
   6. Acknowledgements ...............................................12
   Appendix A. Input Strings to the Presence-Specific
               Static Dictionary......................................13
   References ........................................................22
      Normative References ...........................................22
      Informative References .........................................22

1.  Introduction

   The Session Initiation Protocol (SIP) [4] is extended by the
   SIP-events framework [5] to provide subscriptions and notifications
   of SIP events.  One example of such an event-notification mechanism
   is presence.  The presence information is typically carried in
   Extensible Markup Language (XML) [22] documents that are compliant
   with a given XML schema [23].  The Presence Information Data Format
   (PIDF) [8] defines the format for the basic presence document that
   supplies presence information.  Typically, PIDF is used in
   combination with other extensions to provide a richer user
   experience, among others:  the Presence Data Model [10], Rich
   Presence Extensions to PIDF (RPID) [11], Contact Information in PIDF
   (CIPID) [12], the SIP Event Notification Extension for Resource Lists
   [19] and the SIP User Agent Capability Extensions to PIDF [20], or
   the Location Object in PIDF [16].

   Typically, presence documents can contain large amounts of data.  The
   size of this data is dependent on the number of presentities that a
   watcher is subscribed to and the amount of information supplied by
   the presentity.  This can impose a problem in environments where
   resources are scarce (e.g., low bandwidth links with high latency)
   and the presence service is offered at low or no cost.  This is the
   case, e.g., of some wireless networks and devices.  It is reasonable
   to try to minimize the impact of bringing the presence service to
   wireless networks under these circumstances.

   Work has been done to mitigate the impact of transferring large
   amounts of presence documents between endpoints.  For example, the
   Partial PIDF [15] reduces the amount of data transferred between the
   endpoints.

Garcia-Martin               Standards Track                     [Page 2]
RFC 5112            Presence Dictionary for SIGCOMP         January 2008

   On the other hand, the signaling compression mechanisms specified in
   the SigComp framework (RFC 3320) [2] provide a multiple compression/
   decompression algorithm framework to compress and decompress
   text-based protocols, such as SIP.  When compression is used in SIP,
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