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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 l.jpg

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


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Internetworking Technologies

  • TOPICS

  • Motivation

  • Introduction to Multimedia Communication Systems

  • Multimedia Communication Model

  • Elements of Multimedia Systems

  • Multimedia Network Requirement & related concepts


Motivations for internetworking l.jpg
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


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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


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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


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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


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Some functions of MM Applications

  • Retrieval

  • Browsing

  • Summarisation

  • Creating and Editing Media

  • Information Conversion

  • Personalisation / Adaptation


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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


  • Mm systems communication modes l.jpg
    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…


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    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


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    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


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    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


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    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.


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    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


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    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


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    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!


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    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?


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    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”)


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    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


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    ?

    ?

    ?

    ?

    ?

    ?

    ?

    But multimedia apps requires

    them to be effective!

    ?

    ?

    ?

    ?

    Multimedia Over Today’s Internet

    TCP/UDP/IP:“best-effort service”

    • no guarantees on delay, loss


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    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


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    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?


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    Alternatively

    Media adaptation

    • Can media (audio/video) adapt to network ?

    • How to do ?

      • Network monitoring

      • Adaptive coding

    • Where to do ?

      • Source

      • Enroute



    Principles of communication l.jpg
    Principles of Communication

    • Communication is

      The transfer of information

    • The transfer needs

      A channel

    • Multimedia communication uses

      Multiple channels


    Channels l.jpg
    Channels

    • Examples

      • Sound travels through the air

      • Light and radio waves are electromagnetic radiation

        • different frequencies give different channels


    Choice of channel l.jpg
    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)


    Matching the channel to the information l.jpg
    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


    Media type and use l.jpg

    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”


    Information l.jpg
    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


    Information structure l.jpg
    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


    Digital information l.jpg

    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


    Communication of information l.jpg
    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)


    Models of communication l.jpg
    Models of communication

    • Models are used to describe the process of communication

    • In ideal conditions

    User B

    User A

    Information

    Information


    Models l.jpg
    Models

    • Information transfer may be slightly faulty

    User B

    User A

    Information

    Information


    Models36 l.jpg
    Models

    • Noise affects information transfer

    User B

    User A

    Information

    Information

    Noise


    Communication models l.jpg
    Communication Models

    • Data encoding is used to transfer information

    • Process model

    User A

    User B

    Information

    Information

    Encoding

    Decoding

    Channel


    Models38 l.jpg
    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


    Models39 l.jpg

    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


    Example l.jpg
    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)


    Principles of communication41 l.jpg
    Principles of communication

    • Standards

    • Protocols

    • Error control, redundancy and accuracy

    • Channel

    • Context

    • Coding


    Standards l.jpg
    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


    Digital communication l.jpg
    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


    Summary l.jpg
    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


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    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 ?


    Slide46 l.jpg

    New Distribution Architectures

    • Extending client-server architecture

      • Proxy Caching

      • Content Distribution Networks (CDN)

    • Replacing client-server architecture

      • Peer-to-Peer Networks


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    Client

    Client

    Client

    Client

    Client

    Client

    Client

    Server1

    Server2

    Proxy

    Proxy

    Proxy Caching for Streaming Media

    Campus

    ISP

    Internet


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    Client

    Client

    Client

    Client

    Client

    Client

    Client

    Server1

    Server2

    Server1

    Server1

    CDN for Streaming Media

    Campus

    ISP

    Internet


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    Client

    Client

    Client

    Client

    Client

    Client

    Client

    Server1

    Server2

    Peer-to-peer Streaming

    ISP

    Internet


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    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


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    • Networked Multimedia Challenges

    • Network Capacity – effective throughput

    • How good Internet best-effort could be?

      • • Dynamic behavior-- network congestion

      • • resource management

      • • Best effort vs. QoS networks

      • • fairness

    • Error Control

      • • error-tolerant media (e.g., video)

      • • error-sensitive media (e.g., audio)

      • • real-time error recovery


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    Dynamic Delay and Jitter

    • transmission+propagation+network/Queuing

    • Jitter: delay variation due to dynamic network condition or system load

    • Problems-- audio/video synch: how much to buffer in streaming.


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    • Networked Multimedia Requirements

    • MAC Level Support

      • • network capacity

      • • synchronous vs. randomized media: token bust vs.CSMA/CD vs. ISDN

    • Network Performance Guarantees

      • • QoS (reservation or priority-based service): guaranteed bandwidth, bounded delay and jitter

      • • QoS-based routing

      • • Multi-point Communication (multicast routing)

      • Transport Level Support

      • • TCP vs. UDP: TCP problems (slow start and congestion control)

      • • Error recovery (unreliable, full-reliable and semi-reliable, FEC)


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    • Transport Level Support (cont.)

      • • Adaptive buffer control

      • • Adaptive rate/flow control

      • • Reliable Multicasting (why)

    • Application Level

      • • Session Control: session advertisement, initiation,

      • authentication, termination and billing

    • • Floor Control: conference resource management

      • – Controlled vs. uncontrolled

      • – Distributed vs. centralized (RMP-based vs. server-based)


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    • Multimedia Streams Synchronization

    • – Intra-media synchronization

    • – Inter-media synchronization

    • – Audio, shared tools, global pointer and video

    • – End-view Synchronization


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    References

    Multimedia Communication Systems, K R Rao etal, Pearson Education, 2002, ISBN 81-7808-793-6

    Multimedia Information Networking, Nalin Sharda, Prentice Hall, 1999, ISBN 013258773.


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