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

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 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 mmcom_imess_e.fm 1 16.December.04

Scope www.kom.tu-darmstadt.de www.httc.de KN III (Mobile Networking), Distributed Multimedia Systems ( MM I and MM II ), Telecooperation II,III. ...; Embedded Systems Terminal Inst.-Msg. Applications IP-Tel. Peer-to- access access E-mail Peer Web File L5 Application Layer SIP & (Anwendung) H.323 Transport Layer Internet: Transport Netw. Transitions L4 UDP, TCP, SCTP QoS - RTP (Transport) Addressing Security Network Layer Internet: Network L3 IP QoS (Vermittlung) Data Link Layer LAN, MAN L2 High-Speed LAN (Sicherung) Physical Layer L1 Queueing Theory & Network Calculus (Bitübertragung) Introduction Legend: KN I KN II mmcom_imess_e.fm 2 16.December.04

Overview www.kom.tu-darmstadt.de www.httc.de 1. Basics, Principles and State of the Art 2. Future Enhancements - Open Issues mmcom_imess_e.fm 3 16.December.04

1. Basics, Principles and State of the Art www.kom.tu-darmstadt.de www.httc.de 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 mmcom_imess_e.fm 4 16.December.04

Instant Messaging - User View www.kom.tu-darmstadt.de www.httc.de Buddy List online Alice online Bob Buddy List online Oscar Alice Alice online Bob online direct message to Bob Oscar hidden Alex Buddy List Bob Oscars state is hidden to Alex Alex online Bob online store+forward message to Jack Jack offline Oscar • 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 mmcom_imess_e.fm 5 16.December.04

Instant Messaging - System View www.kom.tu-darmstadt.de www.httc.de IM server store+forward state and profile database message to Jack Bob online Buddy List (PUSH) login Alex online 2. 1. Bob online Jack offline 3. direct message to Bob Oscar Bob 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 mmcom_imess_e.fm 6 16.December.04

Programs and Products www.kom.tu-darmstadt.de www.httc.de 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, ... mmcom_imess_e.fm 7 16.December.04

2. Future Enhancements - Open Issues www.kom.tu-darmstadt.de www.httc.de 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 mmcom_imess_e.fm 8 16.December.04

Future Enhancements - Context Integration www.kom.tu-darmstadt.de www.httc.de central message or SMS distributed architecture email 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 mmcom_imess_e.fm 9 16.December.04

Instant Messaging with SIP www.kom.tu-darmstadt.de www.httc.de 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” mmcom_imess_e.fm 10 16.December.04

Instant Messaging with SIP (2) www.kom.tu-darmstadt.de www.httc.de 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 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) mmcom_imess_e.fm 11 16.December.04

Instant Messaging with SIP l (3) www.kom.tu-darmstadt.de www.httc.de Watcher IM Server User SUBSCRIBE (Event: presence) 200 OK NOTIFY 200 OK Update presence NOTIFY 200 OK SUBSCRIBE • 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 mmcom_imess_e.fm 12 16.December.04