Communication Networks II www.kom.tu-darmstadt.de www.httc.de - - PowerPoint PPT Presentation

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Feb 02, 2023 379 likes •509 views

Communication Networks II www.kom.tu-darmstadt.de www.httc.de Multimedia Communications / QoS Specific Topics: Instant Messaging Prof. Dr.-Ing. Ralf Steinmetz TU Darmstadt - Technische Universitt Darmstadt, Dept. of Electrical Engineering

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Communication Networks II

Prof. Dr.-Ing. Ralf Steinmetz

TU Darmstadt - Technische Universität Darmstadt,

Dept. of Electrical Engineering and Information Technology, Dept. of Computer Science

KOM - Multimedia Communications Lab

Merckstr. 25, D-64283 Darmstadt, Germany, Ralf.Steinmetz@KOM.tu-darmstadt.de

Tel.+49 6151 166151, Fax. +49 6151 166152

httc - Hessian Telemedia Technology Competence-Center e.V

Merckstr. 25, D-64283 Darmstadt, Ralf.Steinmetz@httc.de

Multimedia Communications / QoS Specific Topics: Instant Messaging

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Scope

KN III (Mobile Networking), Distributed Multimedia Systems (MM I and MM II), Telecooperation II,III. ...; Embedded Systems

L5

Applications Terminal access File access E-mail Web Peer-to- Peer Inst.-Msg. IP-Tel. Application Layer (Anwendung) SIP & H.323

L4

Transport Layer (Transport) Internet: UDP, TCP, SCTP

Netw. Transitions

Security Addressing Transport QoS - RTP

L3

Network Layer (Vermittlung) Internet: IP Network QoS

L2

Data Link Layer (Sicherung) LAN, MAN High-Speed LAN

L1

Physical Layer (Bitübertragung) Queueing Theory & Network Calculus Introduction

Legend: KN I KN II

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Overview

1. Basics, Principles and State of the Art
2. Future Enhancements - Open Issues

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1. Basics, Principles and State of the Art

Instant Messaging (IM)

tries to feature real-time direct conversation
comparable to SMS / pager services or person to person chat
using text messages
different from email
"instant" content sending and delivery
immediate transport if possible
by "leaving" it for the receiver otherwise
usually coupled with presence mechanisms

Frequently enhanced with additional services like

buddy lists
all users I want to communicate with
chat rooms (private/public)
notification of e.g. email
news ticker
file transfer

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Instant Messaging - User View

let other people "see" my presence (if I do allow that)
let me see the presence of other people
reach available persons immediately or leave them a message

Alex Alice Bob Buddy List Alice Bob Oscar Oscar Buddy List Alice Bob Oscar Buddy List

Alex

Bob Jack Oscars state is hidden to Alex direct message to Bob store+forward message to Jack

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ffline

hidden

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Instant Messaging - System View

Communication protocol

client / server model combined with server push mode
centralized databases allow to retrieve "profile / buddy list information"
from whatever client somebody is currently using (e.g. PC at work, home,..)

Message Transfer Alternatives

direct:

after learning partners point of presence from infrastructure

proxied:

through infrastructure (makes coping with firewalls easier)

store and forward

Oscar Bob Buddy List direct message to Bob store+forward message to Jack IM server state and profile database login Bob online (PUSH) 1. 2. 3. Alex

Bob Jack

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Programs and Products

Global Players

AOL
AOL Proprietary Messenger
AOL Instant Messenger (AIM) Standalone
ICQ
Microsoft
MSN Messenger (Netmeeting / H.323)
Windows Messenger (UPnP / SIP)
Yahoo! Messenger
T-Online Messenger

Clients and protocols

proprietary and incompatible

Alternative approach

Jabber Software Foundation (XML, Open Protocol)
various clients like Gabber, ...

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2. Future Enhancements - Open Issues

privacy and data security

encryption of data
ensure that data will not be monitored / sold
granting, managing and retracting permissions

interoperable clients

increasing number of polyglot clients caused by
competition, reverse engineering
ongoing modifications, enhancements

access from multiple devices

PC, wireless devices, PDA, IP phones

scalability

hundreds of
millions of users
billions of messages/notifications per day
possible speed limits for the propagation of states in distributed systems

Telephony integration

many services require voice integration industry mandates

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Future Enhancements - Context Integration

New Approaches

include location and context awareness
where is the user
at the moment
in near future
what is the user doing
which are
the available and most suitable communication devices and media
use implicit and explicit states
derive state from known attributes

message SMS email central

distributed architecture

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Instant Messaging with SIP

Use SIP infrastructure for Instant Messaging

provides signaling framework
SIP
servers route messages
registrars provide means for adressing and locating users
covers some security aspects inherently already

New aspects to SIP

Instant Messaging
problem
possible congestion on SIP signaling path

through large amount of SIP messages carrying user payload

solution:
to define new MESSAGE method

which is sent direct to the target and not through SIP server

Presence
use SIP event concept
SUBSCRIBE / NOTIFY
new event type “presence”

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Instant Messaging with SIP (2)

SIP MESSAGE method for Instant Messaging

addressing uses SIP or IM URIs
200 OK
only indicates the message was accepted by the User Agent (UA)
payload transport
must support at least content type text/plain
may support MIME type content including text/cpim
(Common Presence and Instant Message Format)

MESSAGE sip:Bob SIP/2.0 Via: SIP/2.0/TCP proxy;branch=xxx From: sip:Alice;tag=yyy To: sip:Bob Call-ID: xyz CSeq: 1 MESSAGE Content-Type: text/plain Content-Length: 15 Bob, come here! 200 OK

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Instant Messaging with SIPl (3)

subscribe to specific event source "presence"

NOTIFY

PUSH message about status changes from the SIP server
presence information in message body with some non-SIP means
e.g. Content-Type: application/cpim-pidf+xm

SUBSCRIBE (Event: presence)

Watcher IM Server User

200 OK NOTIFY 200 OK Update presence NOTIFY 200 OK