cs553 st7 ch01-overview

8/9/2019 CS553 ST7 Ch01-Overview

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William Stallings

Data and ComputerCommunications

7th Edition

Chapter 1Data Communications and

Networks Overview



A Communications Model

• Source—generates data to be transmitted

• Transmitter—Converts data into transmittable signals

• Transmission System—Carries data

• Receiver

—Converts received signal into data• Destination

— Takes incoming data



Communications asks

Transmission systemutilization

Addressing

Interfacing Routing

Signal generation Recovery

Synchronization essage formatting

!"change management Security

!rror detection and correction #et$ork management

%lo$ control



Simpli!ied Communications

Model " Diagram



Simpli!ied Data

Communications Model



Networking

• &oint to 'oint communication not usually'ractical

—Devices are too far a'art

—(arge set of devices $ould need im'racticalnumber of connections

• Solution is a communications net$ork

—)ide Area #et$ork *)A#+

—(ocal Area #et$ork *(A#+



Wide Area Networks

• (arge geogra'hical area• Crossing 'ublic rights of $ay

• Rely in 'art on common carrier circuits

• Alternative technologies—Circuit s$itching

—&acket s$itching

—%rame relay

—Asynchronous Transfer ode *AT+



Circuit Switching

• Dedicated communications 'athestablished for the duration of theconversation

• e,g, tele'hone net$ork



#acket Switching

• Data sent out of se-uence• Small chunks *'ackets+ of data at a time

• &ackets 'assed from node to node

bet$een source and destination• .sed for terminal to com'uter and

com'uter to com'uter communications



$rame %ela&

• &acket s$itching systems have largeoverheads to com'ensate for errors

• odern systems are more reliable

• !rrors can be caught in end system• ost overhead for error control is stri''ed

out



As&nchronous rans!er Mode

• AT• !volution of frame relay

• (ittle overhead for error control

• %i"ed 'acket *called cell+ length• Anything from /0b's to 1b's

• Constant data rate using 'acket s$itching

techni-ue



'ocal Area Networks

• Smaller sco'e—2uilding or small cam'us

• .sually o$ned by same organization as

attached devices• Data rates much higher

• .sually broadcast systems

• #o$ some s$itched systems and AT arebeing introduced



'AN Con!igurations

• S$itched—S$itched !thernet

• ay be single or multi'le s$itches

—AT (A#

—%ibre Channel

• )ireless

—obility

—!ase of installation



Metropolitan Area Networks

• A#• iddle ground bet$een (A# and )A#

• &rivate or 'ublic net$ork

• 3igh s'eed• (arge area



Networking

Con!iguration



$urther %eading

• Stallings4 ), 560078 Data and Com'uterCommunications *9th edition+4 &rentice3all4 .''er Saddle River #:4 cha'ter /

• )eb site for Stallings book

—htt';<<$illiamstallings,com<DCC9e,html

http://williamstallings.com/DCC7e.html

http://williamstallings.com/DCC7e.html

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