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
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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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