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SIMPLE WG                                                    M. Lonnfors
Internet-Draft                                     Nokia Research Center
Expires: April 2, 2004                                  J. Costa-Requena
                                                             E. Leppanen
                                                            H. Khartabil
                                                                   Nokia
                                                         October 3, 2003


      Requirements for Efficient Delivery of Presence Information
                draft-ietf-simple-presinfo-deliv-reg-01

Status of this Memo

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

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF), its areas, and its working groups. Note that other
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   This Internet-Draft will expire on April 2, 2004.

Copyright Notice

   Copyright (C) The Internet Society (2003). All Rights Reserved.

Abstract

   A Presence service implemented using SIMPLE has some constraints for
   delivering presence information to devices with low data processing
   capabilities, small display, and limited battery power. Other
   limitations can be caused by the interface between the terminal and
   the network, i.e. if presence information is delivered over radio
   links with high latency and low bandwidth. This memo presents
   requirements for a solution that can aid to reduce the impacts of
   these constrains and helps to increase efficiency.




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Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
   2.  Conventions  . . . . . . . . . . . . . . . . . . . . . . . . .  3
   3.  Requirements . . . . . . . . . . . . . . . . . . . . . . . . .  4
   3.1 General requirements . . . . . . . . . . . . . . . . . . . . .  4
   3.2 Performance requirements . . . . . . . . . . . . . . . . . . .  4
   3.3 Client and server requirements . . . . . . . . . . . . . . . .  4
   4.  Example use cases  . . . . . . . . . . . . . . . . . . . . . .  5
   4.1 Case 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . .  5
   4.2 Case 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . .  5
   4.3 Case 3 . . . . . . . . . . . . . . . . . . . . . . . . . . . .  5
   5.  Security Considerations  . . . . . . . . . . . . . . . . . . .  5
   6.  Acknowledgements . . . . . . . . . . . . . . . . . . . . . . .  5
       References . . . . . . . . . . . . . . . . . . . . . . . . . .  6
       Authors' Addresses . . . . . . . . . . . . . . . . . . . . . .  6
       Intellectual Property and Copyright Statements . . . . . . . .  8


































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1. Introduction

   SIP extensions for presence [6] allow users ('watchers') to subscribe
   to other users ('presentities') presence information. The presence
   information is composed of multiple pieces of data (tuples) that are
   delivered to the watcher.  Model for presence information delivery
   that is defined in [2] and in [6] specify that watchers always
   receive all presence data related to a presentity. The size of the
   presence information can potentially become large (i.e. presence
   document may contain an arbitrary number of elements called tuples
   that may convey data). It may not be reasonable to send complete
   presence information over low bandwidth and high latency links when
   only part of that information has changed. This may end up in
   degrading the presence service and causing bad perception at the
   watcher side. Thus, it is necessary to provide solutions to overcome
   this problem.

   Presence based applications in wireless terminals have certain
   processing and bandwidth limitations. It is foreseen that the
   presence information may have a considerable size, especially if
   non-ACSII content (for example a picture) is included in presence
   information. Requirements of wireless environments are addressed in
   [3].

   There are some mechanisms, which might be used to help the problem,
   such as signaling compression [4] and content indirection [5].
   However, none of the existing solutions are optimal because they may
   set additional requirements on basic network functionalities such as
   security and cause difficulties in implementing some charging models.
   SIGCOMP helps to reduce the transported data size if data can be
   compressed. However, if data cannot be compressed (for example
   pictures in jpeg format) use of SIGCOMP doesn't provide much help.
   Some of the existing solutions (e.g. content indirection) require
   having a specific server to store the requested presence information
   until the terminal fetches it using another protocol (e.g. HTTP) and
   therefore increases possible security concerns.

   This memo discusses the requirements for an approach where the
   Presence Server (PS) can deliver to the watchers only the part of the
   presence information that has changed compared to the previous
   notification. This mechanism is called partial notification. The
   partial notification is already identified as a potential approach by
   the SIP Extensions for Presence document [6].                                        .

2. Conventions

   In this document, the key words "MUST", "MUST NOT", "REQUIRED",
   "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY",



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   and "OPTIONAL" are to be interpreted as described in RFC 2119 [1]
   and indicate requirement levels for compliant implementations.

3. Requirements

3.1 General requirements

   REG1: The subscriber MUST have a mechanism to limit the overall
   content size delivered in the notifications.

   REQ2: The presence service MUST allow mechanisms for efficient
   handling of large contents of presence documents.

   RE3: The mechanism MUST allow the subscriber to get information about
   presence information changes (modifications, removals, and additions)
   compared to last notification.

   REQ4: The mechanism MUST NOT affect the requirements of basic network
   functionalities such as security.

3.2 Performance requirements

   REQ5: The presence service MUST allow efficient utilization of the
   network resources (radio links). The presence service MUST be able to
   avoid additional or unnecessary round-trips for receiving changed
   presence information.

   REQ6: The presence service MUST be able to avoid transmission of
   unnecessary information (over radio links) when notifying the
   presence information change to watcher.

   REQ7: The presence service MUST be able to be utilized by devices
   with low data processing capabilities, small display, limited memory
   size and limited battery power.

3.3 Client and server requirements

   REQ8: The subscriber MUST be able to negotiate, during the
   subscription phase, to receive only changes of the presence document.

   REQ9: The subscriber MUST be able to indicate support to receive only
   changes of the presence information.

   REQ10: The subscriber SHOULD be able to request, during the
   subscription phase, that the Presence Agent sends only changes to the
   presence document.

   REQ11: The subscriber capable of receiving only changes to presence



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   documents MUST be able to use the presence service with full state
   notifications.

4. Example use cases

4.1 Case 1

   Presence service charging for a subscriber is based on the received
   data volume. Thus the subscriber requires from the presence server
   that only the changed content is delivered after the first
   notification.

4.2 Case 2

   The watcher and the presentity have network subscriptions for
   different operators. Presentity's presence information contains
   non-ASCII data like pictures. One option to deliver pictures could be
   implemented by using content indirection mechanism [5] but
   presentity's operator may not be willing to store content that will
   be delivered to customer of some other operator. To enable efficient
   handling of non-ACSII data and to limit the network load operator can
   support partial notifications instead.

4.3 Case 3

   The presentity's presence data is composed of the normal status
   information and it also contains a picture. The watcher using a
   wireless terminal subscribes to presentity's presence information.
   Due to limitations in wireless environment the watcher would like to
   limit the amount of transferred data over wireless links. Using the
   partial notifications presence server can send only changed presence
   information thus limiting the amount of data transferred over
   wireless links.

5. Security Considerations

   This document provides requirements for efficient delivery of
   Presence information. Because of this no security consideration apply
   directly to this document. However, solution is likely to build on
   top of presence delivery mechanisms defined in IMPP and in SIMPLE
   working group all security considerations defined in PIDF [2] and in
   [6] will apply to the solution.

6. Acknowledgements

   The authors would like to thank Juha Kalliokulju for his valuable
   comments.




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References

   [1]  Bradner, S., "Key words for use in RFCs to Indicate Requirement
        Levels", BCP 14, RFC 2119, March 1997.

   [2]  Day, M., Rosenberg, J. and H. Sugano, "A Model for Presence and
        Instant Messaging", RFC 2778, February 2000.

   [3]  Kiss, K., "Requirements for Presence Service based on 3GPP
        specifications and wireless environment characteristics",
        draft-kiss-simple-presence-wireless-reqs-02 (work in progress),
        Febryary 2003.

   [4]  Price, R., "Signaling Compression (SigComp)", RFC 3320, January
        2003.

   [5]  Olson, S., "A Mechanism for Content Indirection in Session
        Initiation Protocol (SIP) Messages",
        draft-ietf-sip-content-indirect-mech-02, November 2002.

   [6]  Rosenberg, J., "Session Initiation Protocol (SIP) Extensions for
        Presence",  draft-ietf-simple-presence-10.txt, May 2002.


Authors' Addresses

   Mikko Lonnfors
   Nokia Research Center
   Itamerenkatu 00180
   Helsinki
   Finland

   Phone: + 358 71 8008000
   EMail: mikko.lonnfors@nokia.com


   Jose Costa-Requena
   Nokia
   Valimotie 9 00380
   Helsinki
   Finland

   Phone: +358 71 8008000
   EMail: jose.costa-requena@nokia.com







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   Eva Leppanen
   Nokia
   P.O BOX 785
   Tampere
   Finland

   Phone: +358 7180 77066
   EMail: eva-maria.leppanen@nokia.com


   Hisham Khartabil
   Nokia
   P.O. Box 321
   Helsinki
   Finland

   Phone: +358 7180 76161
   EMail: hisham.khartabil@nokia.com

































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Intellectual Property Statement

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   HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
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Acknowledgement

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   Internet Society.











































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