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Real Time Communications

Real Time Communications. Presented by Sebastian Neaga. Presentation Overview. Introduction Applications and Technologies Instant Messaging and Chat Video Conferencing VoIP and IP Telephony Grid Computing In-depth look at VoIP. Today. Applications: Instant Messaging and Chat.

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Real Time Communications

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  1. Real Time Communications Presented by Sebastian Neaga

  2. Presentation Overview • Introduction • Applications and Technologies • Instant Messaging and Chat • Video Conferencing • VoIP and IP Telephony • Grid Computing • In-depth look at VoIP

  3. Today

  4. Applications: Instant Messaging and Chat • Communication Prerequisites • Architecture • Client/Server • Mixed Client/Server and Client-to-Client • Pear-to-pear • Standards • Internet Relay Chat (IRC) • T.120 (Data protocol for multimedia)

  5. Applications: Video Conferencing • What is Video Conferencing • Problems with NAT and Firewall? • International Telecommunication Union

  6. Applications: Video Conferencing (cont.) • H.310 Broadband audiovisual communication systems and terminals • H.320 Narrow-band visual telephone systems and terminal equipment • H.321 Adaptation of H.320 visual telephone terminals to B-ISDN environments • H.322 Visual telephone systems and terminal equipment for local area networks which provide a guaranteed quality of service • H.323 Packet-based multimedia communications systems • H.324 Terminal for low bit-rate multimedia communication • T.120 Data protocols for multimedia conferencing

  7. Applications: VoIP and IP Telephony • VoIP and IP Telephony are forms of communications over Internet Protocols (IP) rather than over the Public Switched Telephone Network (PSTN) • VoIP focuses on LAN’s where the IP Telephony focuses on replacing the PSTN networks

  8. Applications: VoIP and IP Telephony (cont.) • Basic Concepts • Conversion analog signals to digital format using CODECs from the G.7xx family • Translation of digital signals to IP packets • Transmission of IP packets over the Internet • Communication Concepts • Easy way to setup and end a call • Making calls should be as simple as dialing • Directory services

  9. Applications: VoIP and IP Telephony (cont.) • VoIP implementation

  10. Applications: VoIP and IP Telephony (cont.) • IP Telephony Implementation • Media Gateway (MG) • provides translations between circuit switched networks and packet switched networks in terms of media flows • sends notification to the MGC about endpoint events • execute commands from the MGCs • Media Gateway Controller or call agent (MGC) • provides call signaling, control and processing intelligence to the gateway • sends and receives commands to/from the gateway • Signaling Gateway (SG) • provides signalling translations between circuit switched networks and packet switched networks.

  11. Applications: Grid Computing • Distributed Computing • Point of Sale terminals • Virtual Organization (VO) • Third Party Data Manipulation

  12. VoIP • Aproaches • Complex Protocol/Simple Architecture • Complex Architecture/Simple Protocol • Standards • H.323 is a standard developed by the International Telecommunications Union which defines a group of protocols over the Packet Based Networks (PBN) which may not necessarily provide guarantee quality of service

  13. VoIP • H.323 Specification of the architecture • H.225 Call control, call setup, and packetization and synchronization of media stream • H.235 Security protocol for authentication, integrity, privacy, etc. • H.245 Capability exchange communication and mode switching • H.450 Supplementary services including call holding, transfer, forwarding, etc. • H.246 Interoperability with circuit-switched services • H.332 For large size conferencing • H.26x Video codecs (H.261, H.263) • G.7xx Audio codecs (G.711, G.723, G.729, etc.)

  14. VoIP • Standards Session Initiation Protocol (SIP) developed by The Internet Engineering Task Force (IETF) is an application layer protocol that defines the initiation, modification and termination of multimedia communications

  15. VoIP • UAC (User Agent Client)- the end-user system sending SIP requests (initiating or terminating a call); • UAS (User Agent Server)- the end-user system handling call requests (receiving or terminating a call); • UA (User Agent) - the combination of UAC and UAS; • Proxy Server (PS)) - a network server handling UA requests and responses in proxy mode (acting as both a server and a client to make requests on behalf of other clients); • Redirect Server (RS)- a network server handling user location services in redirect mode (unlike the PS that initiates its own SIP request); • Registar Server - a network server able to accept UA registrations; • Location Server - a network server able to provide user location services (in order to obtain information about a called party's possible location).

  16. VoIP • SIP Protocol • INVITE • BYE • CANCEL • OPTIONS • ACK • REGISTER

  17. VoIP • H.323 or SIP?

  18. Questions

  19. G.711 PCM A-Law/u-Law 64 Kbps (DS0) • G.726 ADPCM 16, 24, 32, 40 Kbps • G.727 E-ADPCM 16, 24, 32, 40 Kbps • G.729 CS-ACELP 8 Kbps • G.728 LD-CELP 16 Kbps • G.723.1 CELP 6.3/5.3 Kbps Variable

  20. Sources • PCWorld • http://pcworld.com/article/id,119940-page,1/article.html • GNRT • http://gnrt.terena.nl/content.php?section_id=5 • Wikipedia • http://en.wikipedia.org/wiki/Voice_over_IP • Progia • http://www.contentbyexperts.com/

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