Presence in the IP Multimedia Subsystem

© 2008 Institute of Broadband Communication Vienna University of TechnologySlide 1

Presencein the IP Multimedia Subsystem

Happenhofer MarcoJune 26, 2008


Switched of your mobile phone?

Will only prevent ringing of your phone, butit will not prevent the caller to call you andthe caller will not know why he did not reach you


Imaging:

“You could inform your friends and buddies, if you are going to accept call now.”

Would it be useful?Would you use this service?And, would you pay for it ?


Agenda

Meaning of Presence Architecture Presence in SIP Presence in IMS Business Model and relevance to LTE Conclusions


Agenda



Definition of Presence

“A presence [..] system allows users to subscribe to each other and be notified of changes in state, [..].”[IETF]

„In computer and telecommunications networks, presence information is a status indicator that conveys ability and willingness of a potential communication partner - for example a user to communicate.“Wikipedia[en]

“Presence describes the social willingness and technical possibilities (of a subscriber) to accept a connection.”

“A Presence Service is a software system whose role is to collect and disseminate presence information, subject to a wide variety of controls.“ OMA


History

Presence was no topic in plain old telephone systems, because no display possibilities and analogue processing

With Internet chats Presence become popular, because computer could display this state and manage buddy lists (e.g. ICQ)

Skype as first telephone system uses also Presence to display the current state of the buddies

IETF specified also mechanisms to convey presence information


Standardisation bodies

IETF (Internet Engineering Task Force)specifies IP, SIP, PIDF, XCAP, etc. mostly technologies used by presence. www.ietf.org

3GPP (3th Generation Partnership Project) specifies the practical implementation of IMS. www.3gpp.org

OMA (Open Mobile Alliance) concentrates on services and enablers. www.oma.org


Agenda



What information carries Presence

Presence describes the state of a buddy binary with „online“ or „offline“.

in a homogen communication system


What information could be carried by Presence

Presence state with open/closed and comments like (busy, call proceeding, etc.)

Communication media (text, audio or video) Communication capabilities (like video telephone,

resolution, etc.) Supported Codecs Communication protocols (sip, smtp, etc. ) Addresses (IP, URIs, etc. ) Location (e.g. @office) / Local Time Mood / present activities (e.g. in lecture) / Timetable Privacy aspects


Architecture & Roles

OnlineBusy


Agenda



SIP and the Event Notification Framework

B. Roach, „ Session Initiation Protocol (SIP)-Specific Event Notification“, IETF, RFC 3265J. Rosenberg, „ A Presence Event Package for the Session Initiation Protocol (SIP)”, IETF, RFC 3856


Presence encoding - PIDF

<?xml version="1.0" encoding="UTF-8"?>

<presence entity="pres:[email protected]">

<tuple id="bs35r9">

<status>

<basic>open</basic>

</status>

<contact priority="0.8">sip:[email protected]</contact>

<note xml:lang="en">Don't Disturb Please!</note>

<timestamp>2001-10-27T16:49:29Z</timestamp>

</tuple>

</presence>H. Sugano, S. Fujimoto, G. Klyne, A. Bateman, W. Carr, J. Peterson, „ Presence Information Data Format (PIDF)“, IETF RFC 3863


Problems

Problem

complexity 1:m on the UE connection from each presentity to each watcher

high bandwidth requirements on the UE

presence changes has to be announced to each watcher

changes last long for many watcher size of one change message ~16 kBit => 12,5 sec @ 64kbit (50w)

needs a lot of computation power on UE

user equipment has not powerful processors

executing policies Access to presence state is executed at UE

only single presence source Presence state is defined by a single device


Solution of these problems

A. Niemi, Ed., „ Session Initiation Protocol (SIP) Extension for Event State Publication“, IETF, RFC 3909A. B. Roach, B. Campbell, J. Rosenberg, „ A Session Initiation Protocol (SIP) Event Notification Extension for Resource Lists“, IETF, RFC 4662


Solutions

Problem

complexity 1:m on the UE Only 2 connections (1 announce, 1 notify)

high bandwidth requirements on the UE

reduced bandwidth due only 2 connections (all overhead from SIP/IP)

changes last long for many watcher reduced delay because only one announcement to the server

needs a lot of computation power on UE

fewer connection fewer processing power required

executing policies policies executed on server

only single presence source Several UE can define the presence state


Agenda



IMS

E-CSCF

P-CSCF

S-CSCF MGCF

HSS Cx

IP Multimedia Networks

IMS-MGW

CS Network

Mn

Mb

Mg

Mm

MRFP

Mb

Mr

Mb

Legacy mobile signalling Networks

I-CSCF

Mw

Mw

Gm

BGCF Mj Mi

BGCF

Mk Mk C, D,

Gc, Gr

UE

Mb

Mb

Mb

MRFC

SLF Dx

Mp

CS

CS

Rx

Mm

LRF

Ml

Le

BGCF

Mi

LCS Client

Cx

Dx

AS

Sh

Ut

Mw

ISC

IBCF Mx

Mx

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Dh

TrGW Izi

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3GPP TS 23.002


IMS

Stores account data (HLR)

Executes service relevant tasks

Access point for other IMS systems

Access point for own subscriber executes policies and security tasks

User Equipmenty


Components in IMS

Presence Source:Entity which creates presence information(presentity)

Watcher:Entity which wants to follow the presence state

Presence Server:Entity which stores the presence state of several entities

Resource List Server:Entity which collects presence information for the watcher

Presence XDMS:Entity which stores which watcher is allowed to see which data

RLS XDMS:Entity which stores buddylists for watcher

Clients, for creating and presenting presence information

Server which process presence information

Servers which store policies


The Architecture in IMS

My buddies?

List of Alice buddies?

Alice buddies:BobCarol

Get Bob state

Get Carol state

Policy for Alice from Bob?

Policy for Alice from Carol?

Accepted Accepted


Useability

Updating the presence state (by the user)“I am online, but I am still in a meeting!”

Configuring police rules for all watcher ”What are the watchers allowed to see?”


Privacy and Law

presence is a person related information and should be protected against unauthorized access

presence server executes policies, which are configured by the presentity

watcher could forward the presence information

network operator known about the presentity

Datenschutzgesetz 2000


Agenda



LTE

LTEOffers:High bandwidthlow latency

Requires:Packet switched signalling

Requires:Return of invest

IMS

Requires:High bandwidthlow latencyOffers:

Packet switched signalling

Offers:End2end signalling, QoS, charging, service interfaces

Requires:Return of invest

customerOffers:fees

Offers:fees

“Requires”:Services

legacyservices

Requires:End2end signalling, charging, QoS

Offers:Services

packet based

services

Requires:End2end signalling, charging, service interfaces

Offers:Services

Cashcow Killerapplication


Presence as Cashcow

could get very hard to sell basic presence

have to pay for all buddies over about 20 buddies (social aspects, removing old friends)

Does presence reduce the number of voice minutes (fewer voice box calls) ?

Extend presence functionality for paying customers (DSG2000)


Presence as Killerapplication for LTE/IMS

Killerapplication = driver for a new technology (WWW was the killerapplication for the internet)

UMTS had no killerapplication (most thought video telephony is it, but pure internet was it)

Needs a critical number of user in this service, before there is no possibility to sell

Offer as bundle with 4G/telephone account Maybe presence gateways for 3G to 4G presence


Agenda



Conclusions

presences indicates if somebody if wiling to accept a connection

P2P Presence works, but Server based scales Easy configuration, intuitive meaning and easy usage of

presence privacy & DSG2000 not realistic to sell as a stand alone service (extend it) could motivate people to switch from 3G/ISDN to 4G/IMS


References

J. Rosenberg, H. Schulzrinne, G. Camarillo, A. Johnston, J. Peterson, R. Sparks, M. Handley, E. Schooler, „SIP: Session Initiation Protocol“, IETF, RFC 3261

M. Day, J. Rosenberg, H. Sugano, „ A Model for Presence and Instant Messaging”, IETF, RFC 2778 A. B. Roach, „ Session Initiation Protocol (SIP)-Specific Event Notification“, IETF, RFC 3265 J. Rosenberg, „ A Presence Event Package for the Session Initiation Protocol (SIP)”, IETF, RFC 3856 J. Rosenberg, „ A Watcher Information Event Template-Package for the Session Initiation Protocol (SIP)”, IETF, RFC 3857 H. Sugano, S. Fujimoto, G. Klyne, A. Bateman, W. Carr, J. Peterson, „ Presence Information Data Format (PIDF)“, IETF RFC 3863 A. Niemi, Ed., „ Session Initiation Protocol (SIP) Extension for Event State Publication“, IETF, RFC 3909 E. Burger, Ed., „ A Mechanism for Content Indirection in Session Initiation Protocol (SIP) Messages“, IETF, RFC 4483 H. Khartabil, E. Leppanen, M. Lonnfors, J. Costa-Requena, „ Functional Description of Event Notification Filtering”, IETF, RFC 4660 A. B. Roach, B. Campbell, J. Rosenberg, „ A Session Initiation Protocol (SIP) Event Notification Extension for Resource Lists“, IETF, RFC

4662 J. Rosenberg, „ The Extensible Markup Language (XML) Configuration Access Protocol (XCAP)“, IETF, RFC 4825 3rd Generation Partnership Project; Technical Specification Group Services and System Aspects;Presence Service;Architecture and

functional description(Release 8), TS 23.141 V8.1.0 (2008-06) 3rd Generation Partnership Project;Technical Specification Group Core Network and Terminals;Presence service using the IP Multimedia

(IM) Core Network (CN) subsystem;Stage 3 (Release 8), TS 24.141 V8.1.0 (2008-06) Presence SIMPLE Architecture (Candidate Version 1.1 – 28 Jan 2008), Open Mobile Alliance (OMA-AD-Presence_SIMPLE-V1_1-

20080128-C) Enabler Release Definition for OMA Presence SIMPLE (Candidate Version 1.1 – 28 Jan 2008), Open Mobile Alliance (OMA-ERELD-

Presence_SIMPLE-V1_1-20080128-C) XML Document Management Architecture (Candidate Version 2.0 – 24 Jul 2007), Open Mobile Alliance (OMA-AD-XDM-V2_0-20070724-

C) Enabler Release Definition for XML Document Management (Candidate Version 2.0 – 24 Jul 2007), Open Mobile Alliance(OMA-ERELD-

XDM-V2_0-20070724-C)


Thank you for your attention.

Busyready f. questions


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Presence in the IP Multimedia Subsystem