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Overview of Data Communication

and Computer Networks

01204325: Data Communication and Computer Networks

Asst. Prof. Chaiporn Jaikaeo, Ph.D.chaiporn.j@ku.ac.th

http://www.cpe.ku.ac.th/~cpjComputer Engineering Department

Kasetsart University, Bangkok, Thailand

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Outline Data Communication Overview

Definition Components Protocols and standards

Network Overview Connectivity Categories Internetworks

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Motivations Efficient way to share resources

Cost – less expensive Accessibility – easier

Efficient way to exchange information Time – faster Size – bigger Correctness – more accurate

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Data Communication: Definition

Data Communication:

Transfer of data from one device to another via some form of transmission medium.

Transfer of data from one device to another via some form of transmission medium.

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Data Communication

Hi, how are you?

01010001

Hi, how are you?

UserComputer

you?

how

are

Hi,

you?

how

are

Hi,

01010001

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Components in Communication

Hi, how are you?

5 Protocol

4 Medium

3 Receiver2 Sender

1 Message

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Data Representation Numbers

8/16/32 bit integers floating point

Text ASCII, Unicode

Images Bit patterns, Graphics formats

JPG/GIF/etc Audio Samples of continuous signal Video Sequence of bitmap images

150

2

255

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Protocols and Standards Protocol

A set of rules governing data communications

Syntax: format of data block Semantics: meaning of each section Timing: speed and sequencing

Standards De facto (in practice) standards

not approved but widely adopted De jure (in law) standards

approved by an organization

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Standards Organizations Creation Committees

ISO, ITU-T, ANSI, IEEE, EIA Forums Regulatory Agencies

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Direction of Data Flow Simplex: One direction only

Server Monitor

data flow

Keyboard

data flow

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Direction of Data Flow Half Duplex: Both directions, one at a

time

E.g., walkie-talkies

data flow at time 1

data flow at time 2

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Direction of Data Flow Full Duplex: Both directions

simultaneously

E.g., telephone

Can be emulated on a single communication link using various methods

data flow

data flow

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Networks Network: a set of devices connected

by media links

Media Links

Printer

Workstation

Laptop

Scanner

Server

SD

iMac

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Types of Connections Point-to-point Multipoint (multidrop)

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Point-To-Point Connection

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Multipoint Connection

Wireless

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Topology Topology: physical or logical

arrangement of devices Point-to-point Mesh Star Bus Ring Hybrid

Point-to-Point Connection

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Fully Connected Mesh Topology

A

CB

D

E

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Fully Connected Mesh Topology

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Fully Connected Mesh Topology

Pros: Dedicated links Robustness Privacy Easy to identify

fault Cons:

A lot of cabling I/O ports Difficult to move

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Star Topology

Hub

A D

B CDrop

Drop

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Star Topology

Switch

A D

B C

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Star Topology

Hub

A D

B C

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Star Topology Pros:

One I/O port per device

Little cabling Easy to install Robustness Easy to identify

fault

Cons: Single point of

failure More cabling still

required

Hub

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Bus Topology

Dropline

Tap

Terminator

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Bus Topology

A B C D

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Bus Topology

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Bus Topology Pros:

Little cabling Easy to install

Cons: Difficult to modify Difficult to isolate fault Break in the bus cable stops all

transmission

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Ring Topology

A

B

C

D

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Ring Topology

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Ring Topology

Pros: Easy to install Easy to identify fault

Cons: Delay in large ring Break in the ring stops

all transmission

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Hybrid Topologies

ACTACT10M100M

1 2 3 4

13 14 15 16

5 6 7 8

17 18 19 20

9 10 11 12

21 22 23 24

UPLINK

1 2 3 4 5 6 7 8 9 101112

131415161718192021222324COLCOL

PWR

SWITCH

ACTACT10M100M

1 2 3 4

13 14 15 16

5 6 7 8

17 18 19 20

9 10 11 12

21 22 23 24

UPLINK

1 2 3 4 5 6 7 8 9 101112

131415161718192021222324COLCOL

PWR

SWITCH

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Network Categories Local Area Network (LAN) Wide Area Network (WAN) Metropolitan Area Network (MAN)

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Local Area Networks Network in a single office, building,

or campus

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Wide Area Networks Network providing long-distance

communication over a country, a continent, or the whole world

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Metropolitan Area Networks Network extended over an entire city

Bangkhen Kampangsaen

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Switching Dedicated circuits Circuit switching

Telephone switchesestablish circuitsfor communication

Packet switching Data are put into

packets Each stamped with

source and destinationaddresses

Routers know where toforward packets

telephone

switch

Router

Packet

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Network of Networks

Company A

Company D

Network Interface Card (NIC)

Company B

Company C

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Internetworking How to allow devices from different

standards to communicate Gateways/routers – devices

capable of communicating in several standards

These become "network of networks"

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Internetworks Two or more networks connected

become an internetwork, or internet

Example: The Internet

Network1 Network2

Gateway

Network3

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The Internet The largest internetwork (network of

networks) in the world Devices communicating with TCP/IP

protocol suite

UCLA

Stanford

UC Santa Barbara

U. of Utah

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Summary Data communication

Protocols and standards Computer networks

Topologies LAN/MAN/WAN

Internetworks (networks of networks)