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Internetworking Technologies. Shailendra S Shekhawat Chamber: DLPD 2152-B Email: [email protected] 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

Internetworking Technologies

Shailendra S Shekhawat

Chamber: DLPD 2152-B

Email: [email protected]

Website: http://discovery.bits-pilani.ac.in/discipline/csis/sshekhawat/index.html

slide2

Internetworking Technologies

  • TOPICS
  • Motivation
  • Introduction to Multimedia Communication Systems
  • Multimedia Communication Model
  • Elements of Multimedia Systems
  • Multimedia Network Requirement & related concepts
motivations for internetworking
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

slide4

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

example of multimedia applications
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
what is special about digital multimedia
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
some functions of mm applications
Some functions of MM Applications
  • Retrieval
  • Browsing
  • Summarisation
  • Creating and Editing Media
  • Information Conversion
  • Personalisation / Adaptation
5 components of mm communication model
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
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…

slide10

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

slide11

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
slide12

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

fundamental characteristics
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.
slide14

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

slide15

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
slide16

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!
slide17

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?
slide18

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”)

slide19

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
slide20

?

?

?

?

?

?

?

But multimedia apps requires

them to be effective!

?

?

?

?

Multimedia Over Today’s Internet

TCP/UDP/IP:“best-effort service”

  • no guarantees on delay, loss
slide21

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
slide22

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?

slide23

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
Principles of Communication
  • Communication is

The transfer of information

  • The transfer needs

A channel

  • Multimedia communication uses

Multiple channels

channels
Channels
  • Examples
    • Sound travels through the air
    • Light and radio waves are electromagnetic radiation
      • different frequencies give different channels
choice of channel
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
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

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
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
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
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
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
Models of communication
  • Models are used to describe the process of communication
  • In ideal conditions

User B

User A

Information

Information

models
Models
  • Information transfer may be slightly faulty

User B

User A

Information

Information

models36
Models
  • Noise affects information transfer

User B

User A

Information

Information

Noise

communication models
Communication Models
  • Data encoding is used to transfer information
  • Process model

User A

User B

Information

Information

Encoding

Decoding

Channel

models38
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

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
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
Principles of communication
  • Standards
  • Protocols
  • Error control, redundancy and accuracy
  • Channel
  • Context
  • Coding
standards
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
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
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
slide45

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

New Distribution Architectures

  • Extending client-server architecture
    • Proxy Caching
    • Content Distribution Networks (CDN)
  • Replacing client-server architecture
    • Peer-to-Peer Networks
slide47

Client

Client

Client

Client

Client

Client

Client

Server1

Server2

Proxy

Proxy

Proxy Caching for Streaming Media

Campus

ISP

Internet

slide48

Client

Client

Client

Client

Client

Client

Client

Server1

Server2

Server1

Server1

CDN for Streaming Media

Campus

ISP

Internet

slide49

Client

Client

Client

Client

Client

Client

Client

Server1

Server2

Peer-to-peer Streaming

ISP

Internet

slide50

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

slide51

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
slide52

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.

slide53

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)
slide54

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)
slide55

Multimedia Streams Synchronization

  • – Intra-media synchronization
  • – Inter-media synchronization
  • – Audio, shared tools, global pointer and video
  • – End-view Synchronization
slide56

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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