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Internetworking Technologies. Shailendra S Shekhawat Chamber: DLPD 2152-B Email: shailu@bits-pilani.ac.in Website: http://discovery.bits-pilani.ac.in/discipline/csis/sshekhawat/index.html. Internetworking Technologies. TOPICS Motivation Introduction to Multimedia Communication Systems

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Internetworking Technologies


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    1. Internetworking Technologies Shailendra S Shekhawat Chamber: DLPD 2152-B Email: shailu@bits-pilani.ac.in Website: http://discovery.bits-pilani.ac.in/discipline/csis/sshekhawat/index.html

    2. Internetworking Technologies • TOPICS • Motivation • Introduction to Multimedia Communication Systems • Multimedia Communication Model • Elements of Multimedia Systems • Multimedia Network Requirement & related concepts

    3. Motivations for internetworking • No single network can serve all users • Users desire universal interconnection TCP/IP Diverse underlying physical nets must be connected by hardware

    4. Definition of Multimedia Systems “The power of multimedia systems originates in their ability to represent disparate information as a bit stream … every form of representation, from video to text, can be stored, processed and communicated using the same device: a computer.” Some examples of multimedia data Image – photographs and graphics Audio – speech, music, sound effects Text - .doc, .pdf, .html Video – image sequences (+audio) (+text) PLUS, combinations of all of the above; PowerPoint presentations, CD-ROMs, web-pages, interactiveTV Jain (1994), IEEE Multimedia vol. 1(2), p.3

    5. Example of multimedia applications • WWW, M-email, M-new • Video-on-demands • Medical Multimedia Systems • Internet Telephony (audio only) • Interactive Games,Desktop video conferencing • Distance Learning, • Interactive vs. non-interactive, virtual classrooms

    6. What is special about DIGITAL multimedia? • SOME ANSWERS… • Different kinds of information are stored and shared in the same way i.e facilitates the combination • The multimedia information can be computed • Multiple and remote access • Personalised presentation • Interaction • Scale

    7. Some functions of MM Applications • Retrieval • Browsing • Summarisation • Creating and Editing Media • Information Conversion • Personalisation / Adaptation

    8. 5 Components of MM Communication Model • Partitioning of complex information objects into distinct information types for easier communication, storage and processing. • Standardization of service components as per information type, possibly with several levels of quality per information type • Creation of platforms at 2 levels • -Network service platform and • -Multimedia communication level platform • 4. Definition of generic applications • - generic, applicable in various domains • 5. Specific applications • -Domain specific

    9. MM Systems Communication Modes • MM Systems use two key communication modes; • Person to person communication • Eg: teleconferencing, video-phones, distance learning and shared workspace scenarios. • Person to machine communication mode • Eg: Access of business meeting notes, access of broadcast video and document archives from digital library etc Contd…

    10. User Interface User Interface Processing, Storage and retrieval User Interface Transport • Person to person communication Transport User Interface: Creates and allows user to interact with multimedia signals in an easy to use manner Transport or preserves mm signal from one user location to some or all other user locations associated 2. Person to machine communication mode

    11. Multimedia Internetworking: Key issue is Media Streaming i.e • Media (audio/video) at source • transmission to client • streaming: client playout begins before all data has arrived

    12. MM Internetworking Applications Broadly three different classes: 1) Streaming stored audio and video 2) Streaming live audio and video 3) Real-time interactive audio and video

    13. Fundamental characteristics: • Typically delaysensitive • end-to-end delay • delay jitter • But loss tolerant: infrequent losses cause minor glitches • Opposite to data, which are loss intolerant but delay tolerant.

    14. streaming: at this time, client playing out early part of video, while server still sending later part of video Streaming Multimedia: What’s it ? Cumulative data time

    15. Stored Multimedia Interactivity • VCR-like functionality: client can pause, rewind, FF, push slider bar • 10 sec initial delay OK • 1-2 sec until command effect OK • RTSP often used (more later) • timing constraint for still-to-be transmitted data: in time for playout

    16. Live Multimedia Examples: • Internet radio talk show • Live sporting event Streaming • playback buffer • playback can lag tens of seconds after transmission • still have timing constraint Interactivity • fast forward impossible • rewind, pause possible!

    17. Real-Time Multimedia- Interactive • applications:IP telephony, video conference, distributed interactive worlds • end-end delay requirements: • audio: < 150 msec good, < 400 msec OK • includes application-level (packetization) and network delays • higher delays are noticeable, impair interactivity • session initialization • how does callee advertise its IP address, port number, encoding algorithms?

    18. QoS network provides application with Quality-of-Service needed for application to function. When media meet Internet … Multimedia applications:network audio and video (“continuous media”)

    19. Internet: Vehicle for Media Distribution • Heterogeneous network • Protocols, routing, links, network technologies, end-hosts, bandwidth, delay, etc • Best effort service • Available BW is unknown and variable • Loss rate and loss pattern are unknown and variable • Resources are shared • TCP/IP is the dominating protocol stack

    20. ? ? ? ? ? ? ? But multimedia apps requires them to be effective! ? ? ? ? Multimedia Over Today’s Internet TCP/UDP/IP:“best-effort service” • no guarantees on delay, loss

    21. The Reality • Rapid growth of multimedia streaming • Popularity of the Web and the Internet • High-bandwidth access (Cable, DSL,ISDN, LAN) • High overhead imposed on the Internet • Long, high-bandwidth streams • Unfriendly to traditional TCP traffic • Poor and inconsistent quality of streams • Small picture size • Low frame rate • Fluctuation in quality

    22. How should the Internet evolve to better support multimedia? • no major changes.. • more bandwidth when needed.. • Fundamental changes in Internet so that apps can reserve end-to-end bandwidth • Fewer changes to Internet infrastructure, yet provide 1st and 2nd class service. What’s your opinion?

    23. Alternatively… Media adaptation • Can media (audio/video) adapt to network ? • How to do ? • Network monitoring • Adaptive coding • … • Where to do ? • Source • Enroute • …

    24. Internet Multimedia Communication

    25. Principles of Communication • Communication is The transfer of information • The transfer needs A channel • Multimedia communication uses Multiple channels

    26. Channels • Examples • Sound travels through the air • Light and radio waves are electromagnetic radiation • different frequencies give different channels

    27. Choice of channel • Will depend on: • Availability of channel • Availability of equipment • Ability to use channel • Ability to understand message • Economic considerations • Time problems (time zones)

    28. Matching the channel to the information • Example – A Tennis match • Score only - use text or speech • More precise information - pictures can illustrate (e.g. racket shape, players, logos etc) • Full transmission of all available information would need video • multiple channels if including many camera angles

    29. Complexity Video Image High quality sound Speech quality sound Text Size of object Media type and use • More complex information leads to bigger data objects • Communication of these requires bigger channels • i.e. more “capacity” or “bandwidth”

    30. Information • Data is the “raw” quantity • Information is data with “meaning” and “structure” • Examples DataInformation 242325 Telephone number of a friend 270RP333031 BITS House number and postcode 2894251992 Product code of a compact disc

    31. Information structure • Data uses symbols Examples Name Symbols Binary numbers 0 1 Numbers 0 1 2 3 4 5 6 7 8 9 English alphabet a b c d e f g h i j k l m n o p q r s t u v w x y z Symbols can be different but represent similar information E.g Greek, Cyrillic, Arabic or English alphabets all represent sounds

    32. In computer communication, a message might be 234556671+25+23456673+100+23456688+10 This could be Order Part Number Quantity 234556671 25 23456673 100 23456688 10 Digital Information

    33. Communication of Information • Communication may involve errors • In digital communication where binary is used errors cause • 1 to become 0 and • 0 to become 1 • To detect or correct errors requires extra information (redundancy)

    34. Models of communication • Models are used to describe the process of communication • In ideal conditions User B User A Information Information

    35. Models • Information transfer may be slightly faulty User B User A Information Information

    36. Models • Noise affects information transfer User B User A Information Information Noise

    37. Communication Models • Data encoding is used to transfer information • Process model User A User B Information Information Encoding Decoding Channel

    38. Models • Mostly multiple levels are used User B User A Information Information High-level encoding High-level decoding Intermediate decoding Intermediate encoding Low-level decoding Low-level encoding Channel

    39. Information Information Models • Multimedia uses multiple encodings User A User B High-level decoding High-level encoding High-level encoding High-level decoding Intermediate decoding Intermediate encoding Intermediate encoding Intermediate decoding Low-level decoding Low-level encoding Low-level encoding Low-level decoding Media decoding Media encoding Channel

    40. Example • Levels of encoding • An electronic mail message • High level • Language of the communication • Written symbols used • Computer representation of the symbols (ASCII) • Electronic binary signals (0 and 1)

    41. Principles of communication • Standards • Protocols • Error control, redundancy and accuracy • Channel • Context • Coding

    42. Standards • These can define a communication in some or all areas Example In an email message • The text will be in a standard language • Message format will be standard • Needs standard protocols for transfer

    43. Digital communication • All information used by computers is digitally encoded • In multimedia these are Video Audio Speech Sound and music Image Graphics Picture Text Free format Structured information

    44. Summary • Communication is about information • Information takes many forms • Multimedia communication is about encoding different forms of information on one or more channels with links between the different information types

    45. Client Client Client Internet Server Architecture: Client-Server? Limited scalability • Single point of failure • Limited & unstable quality • Asynchronous access could be inefficient • Increasing network capacity doesn’t solve these problems? • Multicasting ?

    46. New Distribution Architectures • Extending client-server architecture • Proxy Caching • Content Distribution Networks (CDN) • Replacing client-server architecture • Peer-to-Peer Networks

    47. Client Client Client Client Client Client Client Server1 Server2 Proxy Proxy Proxy Caching for Streaming Media Campus ISP Internet

    48. Client Client Client Client Client Client Client Server1 Server2 Server1 Server1 CDN for Streaming Media Campus ISP Internet

    49. Client Client Client Client Client Client Client Server1 Server2 Peer-to-peer Streaming ISP Internet

    50. Multimedia Traffic Characteristics Throughput • Constant bit rate (CBR) • Variable bit rate (VBR) Time • Video conferencing => Real-time • Video-on-demands => streaming Symmetry • Symmetric => video conferencing • Asymmetric => video-on-demand