Publication of Partial Presence Information
RFC 5264
Network Working Group A. Niemi
Request for Comments: 5264 M. Lonnfors
Category: Standards Track Nokia
E. Leppanen
Individual
September 2008
Publication of Partial Presence Information
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) Extension for Event State
Publication describes a mechanism with which a presence user agent is
able to publish presence information to a presence agent. Using the
Presence Information Data Format (PIDF), each presence publication
contains full state, regardless of how much of that information has
actually changed since the previous update. As a consequence,
updating a sizeable presence document with small changes bears a
considerable overhead and is therefore inefficient. Especially with
low bandwidth and high latency links, this can constitute a
considerable burden to the system. This memo defines a solution that
aids in reducing the impact of those constraints and increases
transport efficiency by introducing a mechanism that allows for
publication of partial presence information.
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RFC 5264 Partial Publication September 2008
Table of Contents
1. Introduction ....................................................2
2. Definitions and Document Conventions ............................3
3. Overall Operation ...............................................3
3.1. Presence Publication .......................................3
3.2. Partial Presence Publication ...............................4
4. Client and Server Operation .....................................5
4.1. Content-Type for Partial Publications ......................5
4.2. Generation of Partial Publications .........................5
4.3. Processing of Partial Publications .........................7
4.3.1. Processing <pidf-full> ..............................7
4.3.2. Processing <pidf-diff> ..............................7
5. Security Considerations .........................................8
6. Examples ........................................................8
7. Acknowledgements ...............................................12
8. References .....................................................12
8.1. Normative References ......................................12
8.2. Informative References ....................................13
1. Introduction
The Session Initiation Protocol (SIP) Extension for Event State
Publication [RFC3903] allows Presence User Agents ('PUA') to publish
presence information of a user ('presentity'). The Presence Agent
(PA) collects publications from one or several presence user agents,
and generates the composite event state of the presentity.
The baseline format for presence information is defined in the
Presence Information Data Format (PIDF) [RFC3863] and is by default
used in presence publication. The PIDF uses Extensible Markup
Language (XML) [W3C.REC-xml], and groups data into elements called
tuples. In addition, [RFC4479], [RFC4480], [RFC4481], [RFC4482], and
[RFC5196] define extension elements that provide various additional
features to PIDF.
Presence publication by default uses the PIDF document format, and
each publication contains full state, regardless of how much of the
presence information has actually changed since the previous update.
As a consequence, updating a sizeable presence document especially
with small changes bears a considerable overhead and is therefore
inefficient. Publication of information over low bandwidth and high
latency links further exacerbates this inefficiency.
This memo specifies a mechanism with which the PUA is after an
initial full state publication able to publish only those parts of
the presence document that have changed since the previous update.
This is accomplished using the partial PIDF [RFC5262] document format
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RFC 5264 Partial Publication September 2008
to communicate a set of presence document changes to the PA, who then
applies the changes in sequence to its version of the presence
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