New New Basic of Networking

8/13/2019 New New Basic of Networking

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Srinivas Institute of Management Studies , Mangalore Second Semester BCA

CONTENTS

Unit I

Chapter 1 Introduction to Networks

1.1 Overview of Networking

1.2 Need for Networking

1.3 Network Communication Standards

1.4 Open Systems Interconnect OSI! "eference #ode$

1.% &C'(I' "eference #ode$

1.) *ssignment 1

Chapter 2 Network Topologies

2.1 Overview of Network &opo$ogies

2.2 +asic &opo$ogies

2.3 +us &opo$ogy

2.4 "ing &opo$ogy

2.% Star &opo$ogy

2.) Comp$e, &opo$ogies

2.- #esh &opo$ogy

2. /y0rid &opo$ogy

2. *ssignment 2

C/*'&" 3 *N Components

3.1 *N Ca0$es and Connectors

3.2 Ca0$es

3.3 Coa,ia$ Ca0$es

3.4 &wisted'air Ca0$es

3.% Optica$ 5i0er Ca0$es

3.) Connectors

3.- *N 6evices

3. "epeaters

3. /u0s

3.17 Switches

3.11 Network Interface Cards NICs!


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3.12 8ire$ess *Ns 8*Ns!

3.13 *ssignment 3

UNIT IIChapter 4 *N 'rotoco$s

4.1 owerayer 'rotoco$s

4.2 *"Cnet

4.3 thernet

4.4 &oken "ing

4.% 5i0er 6istri0uted 6ata Interface 566I!

4.) #idd$eayer 'rotoco$s

4.- &ransmission Contro$ 'rotoco$(Internet 'rotoco$ &C'(I'!

4. Internetwork 'acket ,change(Se9uenced 'acket ,change I':(S':!

4. Net+ios nhanced ;ser Interface N&+;I!

4.17 /igherayer 'rotoco$s

4.11 /yper &e,t &ransfer 'rotoco$ /&&'!

4.12 5i$e &ransfer 'rotoco$ 5&'!

4.13 Simp$e #ai$ &ransfer 'rotoco$ S#&'!

4.14 *ssignment 4

Chapter % Networking *ddressing

%.1 Introduction to Network *ddressing

%.2 &C'II' *ddressing Scheme

%.3 Components of I' *ddress

%.4 I' *ddress C$asses

%.% I' Su0netting

%.)


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UNIT III

Chapter ) Introduction to 8*N

).1 8*N Connectivity Options).2 'O&S

).3 eased ines

).4 Integrated Services 6igita$ Network IS6N!

).% ateways

-.% 8*N 'rotoco$s

-.) 'ointto'oint 'rotoco$ '''!

-.- :.2%

-. 5rame "e$ay

-. *synchronous &ransfer #ode *!

-.17 *ssignment -

UNIT IV

Chapter 8 Networking Operating System

.1 Overview of Network Operating Systems

.2 8indows 2777 Server

.3 5eatures of 8indows 2777 Server

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.4 ;ser *ccounts

.% >roup ;ser *ccounts ?

.) 5i$e and 6evice Sharing.- Nove$$ Netware

. 5eatures of Nove$$ Netware

. 8indows 2777 Server and Nove$$ Netware

.17 *ssignment

Chapter 9 cti!e "irectory

.1 *ctive 6irectory Services

.2 Internet &oo$s and Services

.3 6omain Name System 6NS!

.4 8indows Internet Naming Service 8INS!

.% 6ynamic /ost Configuration 'rotoco$ 6/C'!

.) *ssignment

UNIT#IChapter#$

Introduction to Networks

$%$O!er!iew o& Networking

/uman communication is a process that invo$ves peop$e communicating with each other. &his

process invo$ves four components@ the sender of the informationA the receiver of the

informationA the $anguageA and the medium through which communication is esta0$ished.

Networking is a concept of connecting mu$tip$e computers so that resourcesA such as printersA

hard disksA and fi$es can 0e shared. * typica$ network is depicted in 5igure 1.1.



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5igure @Computer Network

5igure@ 1.1 +asic Networking

&he users of these networked computers can share data and other information. OrganiBationsmay use networks for many reasons 0esides the speed and re$ia0i$ity of data transfer.

&he most o0vious reason is that a network provides an improved communication $ink0etween usersA ensuring that information is avai$a0$e to users at the right time and the

right p$ace. 5o$$owing are some areas where networking p$ays a maor ro$e@

$%' Need &or Networking

Speed( Dou can 9uick$y access fi$es and other resources avai$a0$e on the network.

If the network is not avai$a0$eA accessing the fi$es wi$$ take time 0ecause you wi$$

re9uire physica$ media such as f$oppy or e,terna$ device to transfer the data.

5or e,amp$eA the head office of an organiBation needs to retrieve some important

data from one of its 0ranches. It wi$$ 0e $ess time consuming to access the dataif the offices are connected through a network.

)esource sharing( #ost organiBations have a $arge num0er of computersA and insta$$ing

software on each computer is e,pensive. &o reduce this costA you can insta$$ thesoftware on a one of the computers in the networkA and a$$ow the users to insta$$

the software from this computer. In additionA networking he$ps in reducing the cost

spent on purchasing new hardware. "esources such as printersA fa, machinesA emai$serversA 8e0 serversA fi$e serversA and scanners are e,pensiveA usua$$y too e,pensive for

sma$$ organiBations. 'roviding a$$ the a0ove e9uipments to each user in the organiBation

is not feasi0$e. &hereforeA the 0est option is to shareA and make these resources

accessi0$e to every user on the network.

Communication &acilities@ Networking he$ps in sending and receiving emai$

messages anywhere in the wor$d. *n emai$ message can contain voiceA videoA andpictures. &he service is more costeffective and faster than posta$ services. 8ith

networkingA you can a$so communicate with peop$e on$ine using the chat service.


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In a networkA the communication 0etween two computers occurs in the form of signa$s. &he

data from a source computer is converted into signa$s and transmitted to the destinationcomputer. On the destination computerA these signa$s are converted 0ack to data. &o connect two

computers in a networkA you .need certain hardware and software components. &he hardware

components used for networking inc$ude@

Ca0$es@ Ca0$es are common$y used as a medium for transmitting data across networks.

&he most common$y used ca0$es are coa,ia$A twistedpairA and optica$ fi0er ca0$es.

Figure 1.2: types of cables

$%- Network Communication Standards(

5or the two computers to communicate with each otherA they need to fo$$ow certain

communication standards. &he fo$$owing topics in this section descri0e two such standards

that ena0$e two computers to communicate with each other on a network.

$%. Open Systems Interconnect /OSI0 )e&erence 1odel

&he Internationa$ Standards OrganiBation ISO! deve$oped the OSI mode$ in 13. &his mode$

connects systems that are open to communicate with each other regard$ess of the protoco$s thateach system uses. &his mode$ a$$ows computers from different manufacturers to communicatewith each other without re9uiring any $ogica$ changes to the hardware and software. &he OSI

mode$ is

represented in seven



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$ayers that define the entire process of communication 0etween two computers on a

network.

5igure@ 1.3 OSI "eference #ode$

5igure 1.4@ 'rocess of 6ata &ransfer in the OSI #ode$

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5or

e,amp$eA you want to transfer some data from computer * to computer +. In this caseA theapp$ication $ayer first receives the data and sends it to the presentation $ayer. &he

presentation $ayer attaches the presentation header to the data. &he data is then sent to the

session $ayer. &his process of sending data continues unti$ it reaches the physica$ $ayer ofcomputer *. &he data is then transferred to the physica$ $ayer of computer + through a

transmission medium. &he physica$ $ayer on computer + converts the signa$s to data

and sends the data to the data $ink $ayer. &he data $ink $ayer removes the data $inkheader and sends the data to the network $ayer. &his process of receiving data on

computer + continues unti$ it reaches the app$ication $ayer. 8hen the data reaches the

app$ication $ayerA it is interpreted 0y the app$ication $ayer and is avai$a0$e on computer

+.5igure shows the process of data transfer 0etween two computers using the OSImode$.

2hysical 3ayer

&he physica$ $ayer is the first $ayer in the OSI mode$. &his $ayer transmits data in the form of

raw 0its using physica$ media such as coa,ia$ ca0$esA twistedpair ca0$esA or fi0er optic

ca0$es. 6uring transmissionA the data is converted into an e$ectrica$(optica$ signa$ 0efore it issent to the receiving device. &he receiving device converts the signa$ into data. &he physica$

$ayer views the type of connection@ thernetA &oken "ingA or 5i0er 6istri0uted 6ata

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Interface 566I! esta0$ished 0etween the devices on a network. &he network components

such as repeatersA hu0sA and amp$ifiers are part of this $ayer.

&he physica$ $ayer@

Identifies the medium used to esta0$ish a connection 0etween two computers on a

network.

&ransfers 0its 0etween devices in the form of e$ectrica$(optica$ signa$s.

"ata 3ink 3ayer

&he data $ink $ayer receives the data from the network $ayerA packages it into framesAand then sends it 0it0y0it on to the physica$ $ayer. &he data $ink $ayer ensures that the data

transmitted a$ong the physica$ medium is error free. In other wordsA the data $ink $ayer does

error detection and data framing.

&o make the data error freeA the data $ink $ayer 0reaks the data into frames. &he frames

are then transmitted se9uentia$$y from the sender system. &he data $ink $ayer on the receiver

system acknow$edges the frame that has successfu$$y arrived. Since the frame receivedfrom the physica$ $ayer on the destination computer is not structuredA the data $ink

$ayer creates the frame 0oundaries 0y adding 0itpattern information at the 0eginning

and end of every frame.

The data link layer(

F *dds a header to the frame if the frame is to 0e sent to another computer on

the same network. If the frame is sent to some other networkA the address of the

device that connects the two networks is considered as the receiver address. 5ore,amp$eA if a router connects two networksA then the address of the router on the

network is used as the receivers address. &he router then forwards the data to the

destination computer.

F Contro$s the f$ow of data received from the sender. &his is referred to as f$ow

contro$. 5igure 1.3@ 'rocess of 6ata &ransfer in the OSI #ode$

F Checks for errors that occur during the transmission of data. It checks for the damaged

and $ost frames and retransmits those frames. &he data $ink $ayer maintains the device address

that determines the particu$ar device on the network. &his is known as the physica$ addressor the #edia *ccess Contro$ #*C! addressA which is uni9ue to a NIC card. *

computer may have severa$ NIC cards. 8hen the data is transmitted from the physica$

$ayerA the destination $ogica$network addresses are trans$ated into the corresponding

#*C addresses. It is not possi0$e for the source computer to transmit packets over anetwork without the destination #*C address.

Network 3ayer

&he network $ayer resides a0ove the data $ink $ayer. &his $ayer is responsi0$e for the de$ivery of

data from the source to the destination computer. &his can 0e achieved 0y arranging the datainto data packets and adding a header to it. &his data packet is a$so referred to as datagram.

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&he header contains the source and destination addresses of the data packet. &his $ayer is a$so

responsi0$e for finding the path through with the data packets can 0e routed to the destinationcomputer. &o de$iver the data packetA this $ayer fo$$ows two processes routing and forwarding.

"outing is the process of finding the path through which the data packet can 0e de$ivered.

5orwarding is the process of using the path provided 0y routing and forwarding it to the

destination computer. &his $ayer in no way is concerned with the re$ia0$e and orderedde$ivery of packets from the source to the destination.

Transport 3ayer

&he transport $ayer in the OSI mode$ is a0ove the network $ayers. &his $ayer is responsi0$e forensuring errorfree endtoend data transfer to the destination computer.

&he transport $ayer@

*cknow$edges the successfu$ transmission of data packets.

"etransmits the data packets if they are not error free. #anages the f$ow of data packets 0etween computers across mu$tip$e networks.

&he data packet is transmitted from the sender computer on$y when it receives an

acknow$edgement from the destination computer. 8hen the connection is esta0$ished

0etween the two computers it uses the connectionoriented or connection$ess protoco$s.In case of connectionoriented protoco$A the data packet carries the path of destination

a$ong with it. It guarantees the de$ivery of data packet at the destination computer. &he

connection is terminated after a$$ the data packets are de$ivered. &hereforeA the connectionoriented protoco$s are considered more re$ia0$e as compared to connection$ess protoco$s. In

case of connection$ess protoco$A the de$ivery of data packets to the destination computer

is not guaranteed.

8hen data is transferred from the source computer to the destination computerA the transport

$ayer adds rror Correction Code CC! to each packet and forms a package. &he CC

is typica$$y a Cyc$ic "edundancy Checksum C"C!A which is an errordetecting scheme. On thereceiver systemA the error in transmission is identified when the C"C at the destination

computer does not match with the C"C p$aced in the data packet. *s a resu$tA data is transmitted

area.

&he network component gateway is part of this $ayer. &he protoco$s used at this $ayer

are Net+;IA &C'A S':A and N8 $ink.

Session 3ayer

&he session $ayer he$ps in esta0$ishing interaction 0etween two computers on a network. &hisinteraction 0etween two computers is referred to as a session. &he session $ayer a$$ows

app$ications to organiBe and to manage data e,change. In additionA the session $ayer a$$ows

users to $ogon to remote computers on a network for transferring fi$es.

&he session $ayer provides the fo$$owing services@

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6ia$ogue contro$@ &he session $ayer manages data traffic on a network. ;sua$$yA

the data traffic f$ows in 0oth directions on a networkA 0ut with a sessionA thef$ow of data is on$y in one direction at a timeA ensuring an order$y e,change

of data.

&here are two dia$ogue contro$ methods@

/a$fdup$e,@ In this methodA each device can either send or receive data.

6up$e,@ In this methodA each device can receive and transmit data simu$taneous$y.

&oken management@ If tokens are usedA here is where they are hand$ed. * session

connection consists of tokens. * token is an attri0ute assigned to a session. &here

are protoco$s on the network that do not permit an operation to 0e carried outsimu$taneous$y 0y two interacting computers. In other wordsA the session $ayer

a$$ows traffic in on$y one direction. &o reso$ve this pro0$emA the session $ayer

provides tokens that can 0e e,changed 0etween two computers on a network. &hecomputer that ho$ds the token can perform the operation at that time.

SynchroniBation and recovery@ SometimesA the data that you want to transfermay not 0e transferred in one attempt. 5or e,amp$eA you want to transfersome fi$es that take an hour to comp$ete. 6uring this processA if the source

machine crashesA the comp$ete data needs to 0e transferred again. &his pro0$em

wi$$ continue if the source computer crashes again. &o so$ve this pro0$emA the

session $ayer inserts checkpoints into the data stream. * data stream is thecontinuous f$ow of data from the source to the destination. &hese checkpoints

ensure that after a crash on$y the data after the $ast checkpoint needs to 0e

transmitted.

&he network component gateway is a part of this $ayer. * protoco$ that works at this $ayeris Net+IOS.

2resentation 3ayer

&he presentation $ayer specifies how the information is presented to the app$ication $ayer

and is concerned with the synta, of the transferred data. Not every computer uses the same

data encoding scheme. &he presentation $ayer encodes the data in a standard format to so$ve

this pro0$em. &he data can 0e encoded 0y the fo$$owing two methods@

"irect translation( In this methodA the *merican Standard Code for Information

Interchange *SCII! code from the source computer is trans$ated into ,tended

+inary Coded 6ecima$ Interchange Code +C6IC! on the destinationcomputer.

Indirect translation@ In this methodA the *SCII code is trans$ated into standard

format at the source computer and then trans$ated to +C6IC on the destination

computer. &his method is recommended 0y OSI and is ca$$ed the *0stract Synta,

Notation I *SN.I! mode$.

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The presentation layer per&orms the &ollowing &unctions(

Encryption and decryption( &he pro0a0i$ity of the data 0eing intercepted 0y

unauthoriBed users is high when the data is transferred through various wire$ess

media such as microwave or sate$$ite. &he data needs to 0e encrypted at the sender=s

end and decrypted at the receiver?s end. &he encryption and decryption ofdata is imp$emented at the presentation $ayer.

"ata compression(6ata compression is essentia$ on a network when the amount

of data 0eing transferred is very $arge. +efore transmissionA the data is compressedA

and on 0eing receivedA the data is decompressed. nsuring speedy de$ivery of dataA

this techni9ue is used most$y for transmitting audio and video fi$es.

pplication 3ayer

&he app$ication $ayer is c$osest to the end user. &he protoco$s at this $ayer he$p the app$icationsto access network resources. &he app$ication $ayer does not inc$ude any user app$icationsA

0ut it provides network services such as fi$e transfer and emai$ to the end users or to thecomputer app$ication.

&he computer app$ications can 0e divided as fo$$ows@

Network applications@ &hese app$ications are programs designed to work on a

network. 5or e,amp$eA you can access a remote computer using the &e$net program.

Standalone applications(&hese app$ications are programs designed for individua$

accessA for e,amp$eA the So$itaire game avai$a0$e with 8indows.

Em4edded applications(&hese app$ications consist of other network app$ications

that are 0ui$t in with the app$ication. 5or e,amp$eA #S8ord a$$ows you to activateemai$ or a 8e0 site reference from the #S8ord document itse$f.

$%5 ssignment 6uestion $

1. 8hat is networkingG

2. 8hat is the need of networkingG

3. 8hat network standard communicationG

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4. /ow physica$ $ayer he$ps in OSI #ode$G

%. /ow data$ink ayer sends the dataG

). 8hat is Network ayerG

-. 8hat are the two processes that fo$$ow Network ayerG

. /ow &ransport ayer worksG

17. 8hat are the two things that transport ayer haveG

11. &wo things a0out session ayerG

12. 8hat are the services of Session ayerG

13. 8hat is 'resentation ayerG

14. 8hat are two methods of 6ata ncodingG

1%. 8hat is the 5unction of presentation of presentation ayerG

1). 8hat is *pp$ication ayerG

1-. Component of *pp$ication ayerG

1.,p$ain differences 0etween ISO and &C'(I' $ayeringG 2713

1 6ifferentiate ha$f dup$e, and fu$$ dup$e, communication. 2713

27 8hat do you mean 0y 0roadcastingG /ow it happens in thernet communicationG 2713

21. ,p$ain the services provided 0y 'hysica$ and 6ata ink $ayers. 2713

Chapter#'

NET7O) TO2O3OIES

'%$ O!er!iew o& Network Topologies

To set up a network: you need to concentrate on the &ollowing points(



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&he hardware and software components to 0e used in the network.

&he datacommunication standards such as OSI and &C'(I' reference mode$s.

&he different types of network topo$ogies to 0e used in designing the $ayout of the

network.

In this chapterA you wi$$ $earn a0out the different types of network topo$ogies that can 0e usedin a network. &he topo$ogy of a network is concerned with the structure of connection

0etween two computers on the network and the $ayout in which the network devices

are connected to each other. &he network topo$ogy is a$so concerned with the type ofwiring used in a network and various factors that affects the network ca0$ing such as

whether the ca0$e wi$$ run through f$oorA wa$$sA or cei$ing. On comp$etion of this chapterA you

wi$$ 0e a0$e to create computer networks using different topo$ogies.

'%' *asic Topologies

&he 0us topo$ogy is the simp$est of a$$ the topo$ogies. In this topo$ogyA a$$ the devices on

the network are connected to each other through a centra$ ca0$e ca$$ed the 0us. ;singshared 0andwidth and una0$e to support speeds 0eyond 17 m0psA the 0us topo$ogy is

good for a sma$$ group of 1%27 computers. If the num0er goes a0ove 27 computersA thenetwork s$ows down to a craw$ since on$y one machine can send data.

'%+ *us Topologies

&he 0us topo$ogy is economica$ 0ecause it uses a sing$e coa,ia$ ca0$eA instead of severa$

ca0$es for connecting a$$ the computers. &he 0us topo$ogy uses a sing$e $ength of ca0$eand does not use a concentrator hu0 or switch!H thereforeA the cost is further reduced.

&he tradeoff is $ow speeds and any fai$ure in the ca0$e at any point can ha$t the entire

network. &rou0$eshooting of the network is a$so very trou0$esome since the point offai$ure cannot 0e direct$y pointed out.

Signa$s on coa,ia$ ca0$es can trave$ up to %77 m without amp$ification. &hereforeA

computers in a 0us topo$ogy can 0e used for connecting computers far apart from eachother. +ecause coa,ia$ ca0$es are used for the 0us topo$ogyA the advantages of these

ca0$es are avai$a0$e to networks that fo$$ow the 0us topo$ogy. /oweverA the same

advantages wi$$ 0e avai$a0$e to a$$ network topo$ogies that use these ca0$es. Coa,ia$ ca0$es areresistive to e,terna$ e$ectromagnetic interferences and therefore can 0e used in hosti$e

environments. &he connection 0etween the ca0$e and the NIC of the computer is accomp$ished

with the & connector.

In the 0us topo$ogyA the data signa$s are avai$a0$e to a$$ the computers a$ong the 0us. &hisdata signa$ carries the address of the destination computer. ach computer on the network

checks the destination address as the data signa$ that passes a$ong the 0us. &hecomputer in the networkA whose address matches the destination address of the data

signa$A makes a copy of the signa$ and converts it into data. &he origina$ signa$ sti$$

transmits a$ong the 0us. If the signa$ is not a0sor0ed or destroyedA it is ref$ected 0ack ontothe network. &his ref$ected signa$ interferes with the ne,t data signa$A and therefore



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the ref$ected signa$ must 0e prevented from trave$ing 0ack a$ong the ca0$e. &o

a0sor0 such signa$sA a device ca$$ed terminator is attached at the ends of the 0usnetwork.

thernet is the most common$y used protoco$ in networks with 0us topo$ogy. thernet

uses Carrier Sense #u$tip$e *ccess with Co$$ision 6etection CS#NC6! to provide mediaaccess.

5igure @ 2.1 +us &opo$ogy

&he advantages of the 0us topo$ogy are as fo$$ows@

*$$ the computers in the 0us topo$ogy network are connected to each other

through a ca0$e. &hereforeA this topo$ogy is easy to imp$ement.

&his topo$ogy is e,tenda0$e 0ecause new devices can 0e easi$y added to the

e,isting 0us network.

&his topo$ogy is not very e,pensive 0ecause on$y one centra$ ca0$e is re9uired

for setting up the networkA therefore e$iminating the cost of purchasing severa$

ca0$es.&he disadvantages of the 0us topo$ogy are as fo$$ows@

&he network co$$apses if the ca0$e is damaged.

&he $imited $ength of the ca0$e in a network may restrict the num0er of devices that

can 0e connected.

&he network s$ows down if additiona$ computers are connected to the network.

*s additiona$ computers and devices are addedA the amount of data transmitted

increases resu$ting in increase of the network traffic. /igh network traffic s$owsdown the network considera0$y.

'%- )ing Topology(

O4;ecti!e

&he ring topo$ogy makes use of two concentric rings to transmit the signa$ around the network.



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"ing topo$ogy uses the token passing method to provide media access to the devices in the

network. * computer that needs to transmit data waits for the token. 8hen the tokenarrivesA it adds the data and the address of the destination computerA and sends the data

a$ong the ring.

On receiving the signa$A the destination computer sends an acknow$edgement signa$ to thesource computer. &henA the source computer re$eases the token so that it can 0e used 0y other

computers in the network. &he ring topo$ogy supports coa,ia$A twistedpair as we$$ as fi0eropticca0$es. NowadaysA howeverA twistedpair and optica$ fi0er ca0$es are common$y used. &he

common protoco$s used to imp$ement ring topo$ogy are &oken "ingA and 5i0er 6istri0uted 6ata

Interface 566I.

5igure@ 2.1 "ing &opo$ogy

&he main advantage of the ring topo$ogy is that a$$ the computers on the network have

e9ua$ access to the token. ach computer on ring network gets an opportunity to transmitdata signa$s 0ecause on$y the computer that has the token can transmit dataA un$ike the

thernet imp$ementation where any computer can transmit data if the network is not 0eing

uti$iBed. &he main disadvantage of the ring topo$ogy is that adding or moving devices affects

the entire network.

'%. Star Topology(

In the star topo$ogyA a$$ the network devices are connected to each other through a centra$concentrator forming a star$ike structure. &he common devices used as the centra$

concentrators are hu0s or switches. &he computers can 0e connected to the hu0 or switch using

;&'A S&'A or optica$ fi0er ca0$es.



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&he cost incurred to set up a star network is high compared to a 0us network since each device

on the network wi$$ uti$iBe an individua$ $ength of ca0$e from the concentrator to its$ocation.

6ue to this $ayoutA fai$ure of a sing$e device e,cept the concentrator! does not ha$t the

entire networkA and trou0$eshooting is very easy. On the downsideA fai$ure of the concentratorcan ha$t the entire segment connected to it. &he concentrator at each $ocation itse$f adds to the

cost.

5igure@ 2.3 star &opo$ogy

&he advantages of the star topo$ogy are as fo$$ows@

In this topo$ogyA you can e,tend the network 0y attaching new devices to the centra$

concentrator.

6ue to the star structure of this topo$ogyA there is no distur0ance when devices

are added to or removed from the network.

It is easy to trou0$eshoot the defects in the network. &he defective device can 0e

removed without affecting the entire network.

&he fai$ure of one device usua$$y does not affect the network.

&he disadvantages of the star topo$ogy are as fo$$ows@

&he $ength of ca0$e re9uired for this topo$ogy is greater than that re9uired for the 0us

topo$ogy.

&he entire network goes down if the centra$ concentrator fai$s.

'%< Comple= Topologies

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In the previous sectionA you $earned a0out the 0asic network topo$ogies. In this sectionA you

wi$$ $earn a0out the comp$e, network topo$ogies used in networking. &he comp$e,topo$ogies are those topo$ogies that use one or more 0asic topo$ogies in a network.

'%5 1esh Topology(

In the mesh topo$ogyA separate ca0$es are used to connect individua$ devices on the

network. &his topo$ogy is e,pensive 0ecause of the num0er of ca0$es used in the network.&he mesh topo$ogy is of two typesA fu$$mesh and partia$mesh.

>ull#1esh

In this topo$ogyA each device is interconnected with a$$ the devices on the networkA 0y a

dedicated ca0$e. If one device fai$sA the data trave$ing a$ong the network can 0e routed

through another device attached to the active device. &he structure of the network iscomp$e, 0ecause the devices in the network are interconnected.

5igure@ 2.4 5u$$#esh topo$ogy

2artial#1esh

In this topo$ogyA each device on the network is not connected to other devices. On$y a few

devices on the network are connected using the fu$$mesh topo$ogyA and the others areconnected to one or more devices on the network.

'%8 ,y4rid Topology

Basic of networking #!


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O0ective

6escri0e the working and features of the hy0rid topo$ogy.

&his topo$ogy is a com0ination of 0usA starA and ring networks. In other wordsA this topo$ogy

com0ines mu$tip$e topo$ogies to form a $arge topo$ogy. &he hy0rid topo$ogy is wide$yimp$emented in 8ide *rea Networks 8*Ns!.

5igure@ 2.% /y0rid star+uses &opo$ogy

5igure 2.% shows two networksA * and +A on a star topo$ogy. /oweverA the connection 0etween

the two networks is esta0$ished using the 0us topo$ogy. In a star0us topo$ogyA the star topo$ogyof each network is $inked to the 0us topo$ogy. If any of the computers fai$s on the star

topo$ogyA it wi$$ not affect the entire network. /oweverA if the centra$ hu0 in the star topo$ogyfai$sA then the entire network goes down 0ecause the ca0$es are connected direct$y to the centra$

hu0 of the star network. *s a resu$tA computers on the network are not a0$e to communicate with

each other.

Basic of networking #"


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5igure 2.)@ hy0rid star ring &opo$ogy

Basic of networking 2$


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2. ssignment 6uestion '

1. 8hat does u mean 0y network &opo$ogiesG

2. 8hat are the +asic &opo$ogiesG

3. *dvantages of +us &opo$ogiesG

4. 6isadvantages of +us &opo$ogiesG

%. /ow "ing &opo$ogies is formedG

). *dvantages of "ing &opo$ogiesG

-. /ow star &opo$ogies is madeG

. 8hat are the Comp$e, &opo$ogiesG

. 8hat is mesh &opo$ogiesG

17. 8hat is 5u$$ mesh &opo$ogiesG

11. 8hat is partia$ mesh &opo$ogiesG

12. 8hat is /y0rid &opo$ogiesG

13. /ow star and "ing &opo$ogies is madeG

14. 8rite any two disadvantages of star topo$ogy. 2713

1%. 8hat do you mean 0y /y0rid topo$ogyG >ive e,amp$e. 2713

1-. ,p$ain the structure and working of +us topo$ogy.

Chapter#+

Basic of networking 2#


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3N Components

3.1 LAN Cables and Connectors

In the previous chaptersA you $earned a0out the need for networkingA the communication

standards used in networksA and the topo$ogies imp$emented in a network. Dou o0served that atopo$ogy defines the manner in which computers and devices are connected in a network. &o

esta0$ish a connection 0etween two computers or devicesA you need hardware as we$$ assoftware components. &he hardware components are usua$$y ca0$esA hu0sA Network Interface

Cards NICs!A and switchesH the software components are protoco$s such as thernetA &oken

"ingA &C'(I' and I':(S':. In this chapterA you wi$$ $earn a0out the different hardwarecomponents used to connect computers and devices in networksA more specifica$$y in a

oca$ *rea Network *N!. &he ne,t chapter wi$$ detai$ the protoco$s used in *N.

&he hardware components of a *N are devices operating at the physica$ $ayer or the data$ink $ayer and are responsi0$e for transmission of e$ectric signa$s from one device to another.

&o transmit e$ectric signa$sA the fo$$owing devices are common$y used in *Ns@

Ca4les

)epeaters

,u4s

Switches

Network Inter&ace Cards

+%' Ca4les

&he common ca0$e types used to connect computers and devices in a *N are@

Coa=ial ca4les

Twisted#pair ca4les

Optical &i4er ca4les

3.3 Coaxial Cables

Identi&y the &eatures o& coa=ial ca4les%

3ist the ad!antages and disad!antages o& coa=ial ca4les%

* coa,ia$ ca0$e consists of two concentric conductors separated 0y insu$ation. &he innerconductor transmits e$ectric signa$sA and the outer conductor acts as a ground. &he entire

assem0$y is wrapped in a sheath of &ef$on or '


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5igure 3.2@ coa,ia$ ca0$e

&he conductor used in coa,ia$ ca0$es is copper wire. It is used for 0oth the inner and outerconductors. +ecause the signa$ is transmitted over the surface of the inner copper wireA

increasing the crosssection of the inner copper wire and thereforeA the entire coa,ia$ ca0$e!

increases the amount of signa$ that can 0e transmitted 0y the ca0$e. &hereforeA a thicker coa,ia$

ca0$e can transmit more data than a thinner one.

&he advantage of coa,ia$ ca0$es is that they support high 0andwidths and can transmit signa$s

up to17 ki$ometers. In factA coa,ia$ ca0$es were the origina$ transmission medium specified 0yI for use with thernet

+%- twisted#pair ca4le

* typica$ twistedpair ca0$e consists of four pairs of thin copper wires coated with '


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5igure 3.3@ Shie$ded &wisted pair Ca0$e

S&' is more e,pensive than ;&' and is genera$$y used in networks where ca0$es pass

c$oser to devices that cause high #I . In additionA the presence of shie$ding increases

the resistance to the signa$ andA thereforeA restricts the ca0$e $ength and thethroughput offered 0y S&'.

Unshielded !isted "air #U"$

;&' ca0$es are the most common$y used communication medium in *Ns. Of the four pairs

in a ;&' ca0$eA howeverA on$y two pairs are actua$$y used for communication in *Ns

and provide speeds of up to177 #0ps. *$$ the four pairs are used on$y for higher transmissionrates such as 1A777 #0ps. 5igure 3.4 shows a crosssection of the ;&' ca0$e.

5igure 3.4@ CrossSection of ;&' Ca0$e


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Category% Cat%!@ Cat% is used for networks that re9uire data transfer rates higher

than that supported 0y Cat3. Cat % supports data transfer rates up to 177 #0ps and isused with 5ast thernet. .

In addition to these category specificationsA Cat) and Cat-A which support higher

0andwidth and data transfer ratesA have a$so 0een deve$oped. ike Cat%A Cat) a$sosupports data transfer rates of up to 1A777 #0ps. /oweverA Cat ) works at a differentfre9uency range than

Cat%. In a networkA a ca0$e may sometimes pickup a signa$ intended for another ca0$e.

&his is ca$$ed crossta$k. Cat) is more resistant to crossta$k than Cat%.

*ny $ight from escaping the core. &he function of c$adding is to ref$ect the $ight 0ack into thecore.

3.% &ptical fiber cable:

5igure 3.%@ CrossSection of Optica$ ca0$e

F Sheath or outer jacket: &he core and c$adding are covered with a sheathA usua$$y made ofp$asticA to protect the fi0er from damage.

;n$ike coa,ia$ ca0$es and twistedpair ca0$esA which transmit data in the form of e$ectric signa$sA

optica$ fi0er ca0$es transmit data in the form of $ight. &hereforeA the data to 0etransmitted is converted into $ight 0y a codec coder and decoder! present at each end ofthe fi0er. &he codec converts the data from the computer into $ightA and the $ight is then

transmitted across the ca0$e with the he$p of either a ight mitting 6iode 6! or an

Inection aser 6iode I6!. *t the destination computerA a decode receives the $ight 0eamand converts it into data. If an 6 is used to transmit $ightA the transmission is ca$$ed mu$ti



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mode transmissionA whereas and I6 is used or sing$emode transmission. &hese transmissions

are detai$ed in the fo$$owing su0topics.

#u$ti#ode &ransmission

* mode is defined as the? ang$e at which a ray of $ight enters the core of the optica$ fi0er ca0$e.

If the $ight enters the core at different ang$esA it is ca$$ed mu$timode transmission. #u$timodetransmission occurs when an 6 is used as the $ight source.

*n 6 is not a concentrated $ight sourceA andA thereforeA the rays of the $ight 0eam disperseafter trave$ing a certain distance through the fi0er. /oweverA not a$$ the rays of the $ight 0eam

disperse.

+%< CONNECTE)?s

&o connect a coa,ia$ ca0$e to an NICA the fo$$owing connectors are re9uired@

@ *NC Connector

5igure 3.)@ +NC Connector

the end of the coa,ia$ ca0$e that p$ugs into a computer is connected to a +NC connector.

* +NC connector connects the coa,ia$ ca0$e to the &connectorA which is p$ugged theend of the coa,ia$ ca0$e that p$ugs into a computer is connected to a +NC connector. *

+NC connector connects the coa,ia$ ca0$e to the &connectorA which is p$ugged

Twisted#2air Ca4le Connectors(

;&' and S&' use different connectors to connect with the NIC. * ;&' ca0$e connects to an

NIC with an "4% connectorA whereas an S&' ca0$e uses a 6she$$ or 6+! connector.

Shows the 6+ connectorA which is used with S&' and an "4% connector used with ;&'.



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5igure 3.-@ &wisted 'air Ca0$e Connectors

Optical >i4er Connectors(

Optica$ fi0er ca0$es use either screwmounted adapters S#*! or spring$oad twist S&!

connectors. S#* uses a screw to connect to the end of the ca0$eA and S& c$aps to connect to the

end of the ca0$e. S& connectors are more popu$ar than S#* connectors 0ecause connector $ossdue to S& connectors is $ess than S#* connectors. Connector $oss is defined as the $oss of

signa$ at the interface 0etween the connector and the NIC. Connector $oss occurs if the end of

the connector is not tight$y p$ugged to the port on the NIC. S& connectors are spring$oadedA andthereforeA p$ug tight$y into the NIC.

5igure 3.@ S& and S#* Connectors

In this sectionA you have $earned a0out the different types of ca0$es used to connect computers

and devices in a *N. Dou have a$so $earned a0out their advantages and disadvantages and the

different types of connectors used for these ca0$es.

+%5 3N "e!ices

* concentrator is a device with two or more ports through which computers and devices can 0e

connected. &he fo$$owing are the two main functions of a concentrator@

&o 0oost the signa$ to restore its origina$ strength.

&o provide an interface to connect mu$tip$e computers and 6evices in a network.



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ImagineA for e,amp$eA an office spread across three f$oors in a 0ui$ding. &he $ength of the ca0$e

re9uired to connect computers on different f$oors may 0e more than the ma,imum supported$ength. In such casesA the signa$ needs to 0e amp$ified. &he simp$est concentrator that can 0e

used to 0oost signa$s over $ong distances is a repeater.

+%8 )epeaters

"epeaters amp$ify a weak signa$ so that the signa$ stays as strong as the origina$ one. 5ore,amp$eA imagine a network in which two computers a0out 377 m apart are connected with a

;&' ca0$e. If one computer sends a signa$ to the otherA the signa$ starts attenuatingA and after a

distance of 1% mA the signa$ strength fa$$s to such an e,tent that the second computer may not

receive any signa$ at a$$. In such casesA you can use a repeater every 1% m 0etween the

computers to 0oost the signa$.

5igure 3.@ "epeaters ;sed to *mp$ify signa$ strength

In additionA repeaters can a$so 0e used to connect two segments of the same network. Segments

refer to $ogica$ sections of the same networkA whereas different networks means that the

networks are $ocated in geographica$$y different areas. 5or e,amp$eA suppose an organiBationhas offices on the first and fifth f$oors of a 0ui$dingA and the computers on 0oth the f$oors

are connected in the same network. In this caseA the computers on the first f$oor form a

segmentA and the computers on the fifth f$oor form another segment. * repeater can

0e used on one of the intermediate f$oors to connect the segments.

+%9 ,u4s

* hu0 is $ike a repeater 0ut with mu$tip$e ports. /u0s operate at the physica$ $ayer of the OSI

reference mode$. /u0s can 0e used to connect mu$tip$e segments of the same network and

transfer data from one segment to another .*$soA hu0s are used to connect computers to aserver in networks that use the star topo$ogy.

Basic of networking 2!


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5igure3.17@

/u0 with 5our ports

&hereforeA it is important to determine the type of ca0$es in the network 0efore you purchase a

hu0. you a$so need to determine the num0er of network segments or the num0er of computers

to 0e connected so that you can purchase a hu0 with the re9uired num0er of ports. &hetype of ca0$es used andA thereforeA the type of ports on the hu0! and the num0er of ports

usua$$y determine the cost of a hu0.

+ased on their functionsA hu0s can 0e c$assified as fo$$ows@

Passive hub@ * passive hu0 does not regenerate or amp$ify the signa$. It on$y actsas an interface 0etween two segments of a network or 0etween different computersin a network. * passive hu0 is used when the network is divided into mu$tip$e

segmentsA 0ut the segments are sufficient$y c$ose to prevent signa$ attenuation.

'assive hu0s genera$$y do not re9uire e$ectrica$ power.

Active hub@ *n active hu0 is a powered device that amp$ifies the signa$ to its

origina$ strength. *ctive hu0s are the most common type of hu0s used innetworks. &hey are usefu$ when the segments of the network are not c$ose to

one another and the signa$s may re9uire amp$ification.

Inte$$igent or #anagea0$e! hu0@ *n inte$$igent hu0 is an active hu0 with additiona$

features such as network monitoring capa0i$ities. 5or e,amp$eA an inte$$igent hu0supporting Simp$e Network #anagement 'rotoco$SN#'!can provide

information a0out such things as activity on each port or network error $ogs.

In additionA an inte$$igent hu0 can a$so 0e used to prevent unauthoriBedcomputers from connecting to the segments of the network.

/u0s are ine,pensive devices. /oweverA hu0s can considera0$y increase network traffic

0ecause they 0roadcast data to the devices connected on a$$ the ports.

Basic of networking 2"


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5igure 3.11@ segments of Network Connected using /u0

In 5igure if Node * in Segment1! sends data to Node 6 in Segment 2!A the data reaches'ort 1 of the hu0. &he hu0 then transmits the signa$ to a$$ the portsA thereforeA to a$$ computers

in Segment 2. Node 6 in Segment 2 picks up the signa$A which is then converted into data.

In the preceding e,amp$eA you can see that a$though the signa$ was addressed to on$y onecomputer in a particu$ar segmentA it is transmitted to a$$ the computers in the segment. If thereare mu$tip$e segments connectedA the signa$ is transmitted to a$$ the segmentsA resu$ting in

increased network traffic. In thernet *NsA unnecessary network traffic increases the chances

of co$$isionsA and degrades network performance.

+%$A Switches (

ike hu0sA switches a$so connect computers in a network or different segments of thesame network. /oweverA un$ike hu0sA which work at the physica$ $ayerA switches work at the

data $ink $ayer of the OSI reference mode$. &hereforeA switches treat data in the form of

frames and not as signa$sA which is the case with physica$ $ayer devices $ike hu0s. * data

frame contains information a0out the #*C address of the destination computer "efer to&opicA Network Interface CardsA for information on #*C address.! Switches can read this

#*C address andA as a resu$tA forward the data on$y to the port that is associated with this

#*C address. 5or this purposeA switches maintain a $ist of #*C addresses and the portnum0er associated with each #*C address.

5igure

3.12@

computers connected using switch

5igure shows a network in which four computers are connected using a switch. *ssume that

Node * sends data to Node C. &he data from Node * reaches the switch from 'ort 1 in the

form of a data frame. &he switch then reads the destination #*C addressA and from the



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$ist of #*C addressesA the switch knows that the data is meant for Node C. *s

Node C is associated with 'ort 3A the switch forwards the data on$y to 'ort 3. &he data isconverted 0ack into a signa$ and transmitted to Node C.

Switches use any of the following two methods to transmit data:

Cut-through switching:In this methodA the switch reads the destination #*C addressof a data frame and immediate$y forwards the frame to the respective port.

Store-and-forward switching: In this methodA the switch receives a$$ the data

frames corresponding to a particu$ar transmission. &he frames are then checkedfor integrity and errors. If the frames are found to 0e errorfreeA the switch forwards

the frames to the respective port. If the frames are corruptA they are not

forwarded to the destinationA and the source device has to resend the frames.

6epending on the re9uirements of the networkA you can se$ect an appropriate method ofswitching. 5or e,amp$eA if the speed of the network is the primary concernA you can se$ect cut

through switching. #ost switchesA howeverA have the a0i$ity to se$ect an appropriate switching

method depending on the network conditions. Initia$$yA the switch uses cutthroughswitchingA 0ut if it finds that the num0er of corrupt data frames is highA it automatica$$y

se$ects storeand forward switching. *fter some timeA if the switch o0serves that the num0er of

corrupt data frames is $owerA the switch reverts 0ack to cutthrough switching. &his is ca$$ed as

auto switching.

+%$$ Network Inter&ace Card /NIC0( NIC is a hardware device that acts as an interface

through which a computer connects to a network. NIC is usua$$y an e,pansion card on thecomputer with a port to p$ug in the network ca0$e. NIC converts the data into e$ectrica$ optica$

signa$s and transfers them through ca0$es from one computer to another on the network. On

receiving the dataA the NIC on the destination computer converts the e$ectrica$ signa$s 0ack to

data.

*n NIC is a hardware device that acts as an interface through which a computer connects to anetwork. NICs work at 0oth the data $ink and the physica$ $ayers of the OSI reference mode$.

*t the data $ink $ayerA the NIC converts the data packets into data frames and adds the

#*C address to the data frameH at the physica$ $ayerA it is responsi0$e for convert in the

data into signa$sA and transmitting them across the communication medium. &he #*C addressis a uni9ue hardware num0er present on the NIC and is specified 0y the NIC manufacturer.

#*C addresses are g$o0a$$y uni9ue.

8hen a computer needs to send dataA the NIC receives data packets from the computerA

converts them into data framesA and passes them across the ca0$e as signa$s. &his ro$e

of the NIC in most 'C environments can 0e divided into the fo$$owing tasks@

,ost#to#card communication(&he NIC communicates with the computer using I"J

Interrupt "e9uest! and receives data present in the memory of the computer for

transmission.



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*u&&ering( &he data received from the computer is not immediate$y transmitted.

InsteadA a$$ the data is 0ufferedA or stored temporari$yA on the NIC 0eforetransmission. +uffering ensures that the NIC has the comp$ete data packet 0efore

converting it into framesA thus preventing incomp$ete data transmissions.

>rame creation(Once the NIC has a$$ the data that needs to 0e transmittedA it dividesthe data into frames. * frame has three parts@ headerA dataA and trai$er. &he header

contains the source and destination #*C addressesH the data part contains the

actua$ data 0eing transmitted across the networkH and the trai$er contains errorchecking information such as Cyc$ic "edundancy Check C"C!.

2arallel#to#serial con!ersion(&he NIC receives data from the computer in para$$e$

form. 5or e,amp$eA a 'CI card receives 32 or )4 0its simu$taneous$y. &he num0er of

0its depends on the mother0oard 0us architecture. /oweverA the data must 0e

converted into seria$ form 0ecause *Ns genera$$y transmit data 0it after 0itA

and not mu$tip$e 0its at a time.

Encoding( &he seria$ 0its are converted into e$ectrica$ signa$s for transmission

across the ca0$e.

In additionA the NIC a$so needs to have an appropriate connector to access the ca0$e. 5or

e,amp$eA coa,ia$ ca0$es use +NC and 6& connectorsA whereas ;&' ca0$es use " 4%

connectors.

#ost NICs provide on$y one type of connector. /oweverA NICs with mu$tip$e connectorsA

such as one &connector and one "4% connectorA are a$so avai$a0$e.

NICs are a$so responsi0$e for determining the speed of the data transfer. NICs may support

different data transfer speedsA for e,amp$eA 17 #0ps or 177 #0ps. &hereforeA when you se$ectan NICA the ca0$es used in a networkA the speed of the networkA and the $ayer 2 protoco$used in the network must 0e considered.

;n$ike other network devicesA such as hu0s or switchesA that perform independent$yA theperformance of an NIC depends on the configuration of the computer. &he fo$$owing factors

affect the performance of an NIC@

*us speed(&he type of e,pansion s$ot on the computer determines the 0us speed. 5or

e,amp$eA IS* s$ots work at a speed of or 1) K+psA whereas 'CI s$ots have a

speed of 32 or )4 K+ps. &hereforeA a 'CI network card offers 0etter performancethan an IS* network card.

1emory( #emory affects the overa$$ performance of a computer to an e,tent.

&hereforeA NICs on computers with more memory perform 0etter than those on

computers with $esser memory.

1emory#access methods(&he NIC can access the main memory using different

methods such as 6irect #emory *ccess 6#*! or Input(output $(O!. In (OA the



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NIC re9uests information from the main memory. &his re9uest shou$d 0e accepted

0y the processorA and then the NIC can access the data. In 6#*A howeverA a6#* contro$$er present on the mother0oard a$$ows the NIC to access the

main memory direct$y. &hereforeA NICs on computers that use 6#* are faster

than NICs on computers that use $(O.

+%$'7ireless 3Ns /73Ns0

8*NsA as the name suggestsA does not use a physica$ medium to connect devices and

computers in the network. InsteadA wire$ess media such as radio and infrared are used.

&hereforeA in a 8*NA the computers or devices have an infrared portA or an NIC thatsupports wire$ess communication. &he popu$ar techno$ogies used for wire$ess communication

are radio wavesA infraredA and +$uetooth. &hese techno$ogies differ in their interna$ working.

/oweverA 8*N is a generic term used to signify the a0sence of ca0$esA and can use any of

these wire$ess techno$ogies. &hereforeA some 8*Ns may 0e using radio whi$e others mayuse +$uetooth techno$ogies.

+$uetooth is a radiofre9uency specification deve$oped 0y a group of organiBations across thewor$dA known as the +$uetooth Specia$ Interest >roup that manufactures e$ectronic components.

+$uetooth specifies standards for the physica$ and data $ink $ayer of the OSI reference mode$.

#u$tip$e computers in a 8*N are connected with the he$p of an *ccess 'oint *'!. *n *'performs the same function as the hu0A as shown in 5igure.

5igure 3.13@ Computer connected wire$ess$y in *N

*n *' typica$$y performs the fo$$owing three functions@

"eceives data frames from computers and devices connected to it.



34/143


+uffers the data frames and checks their integrity.

&ransmits the data frames to the destination device.

8*Ns were first deve$oped in the ear$y 17s. /owever the use of 8*Ns was $imited due

to the cost of devices invo$ved as we$$ as the $imited 0andwidth offered. NowadaysAhoweverA the cost of devicesA such as *'sA has decreased considera0$y and wire$ess

techno$ogies such as +$uetooth offer speeds of 1 #0ps. In additionA 8*N s offers the

fo$$owing 0enefits over conventiona$ *Ns that use physica$ connectivity@

)esistance to E1II)>I( 8*Ns uses radio or infrared waves to transmit

dataA and are thereforeA resistant to phenomena such as signa$ attenuation anddistortion due to #I and "5I.

Easy installation(&he a0sence of physica$ medium to connect computers great$y

reduces the time re9uired to insta$$ a *N. *$soA the time re9uired to configure

the devices and *'sA is near$y the same as that re9uired to configurecomputers in a conventiona$ *N.

1o4ility(&he a0sence of physica$ connectivity provides users the f$e,i0i$ity to

move computers and devices within the network. &his is he$pfu$ for emp$oyees

who may need to access uptodate data in meetings and conferences.

>le=i4ility(8*Ns can connect computers and devices in areas where ca0$ing is

not possi0$e. 5or e,amp$eA in factories that have heavy machineryA ;&' ca0$es

cannot 0e used 0ecause they are prone to #. * 8*N can 0e imp$emented in

such cases.

E=pansion( * conventiona$ *N can 0e e,panded with the he$p of an *'I #ost*'s support transfer of data 0etween a conventiona$ *N and a 8*N.

&hereforeA *Ns can 0e e,panded to accommodate more computers without incurring any

additiona$ ca0$ing cost. 6ue to these advantagesA 8*Ns are very popu$ar. &he common

use of 8*Ns is in the fo$$owing areas@

,ome users(#ost home users are not comforta0$e with insta$$ation of ca0$es. 8*Ns

provide an easy way to connect mu$tip$e devices and set up a home network.

eneral access(NowadaysA trave$ing emp$oyees of organiBations need to access their

corporate network from p$aces such as an airportA a hote$A or an auditorium ha$$. #ost of

these 0ui$dings are 0ui$t without a provision for connecting computers. It is not practica$to provide connectivity 0y insta$$ing ca0$es in such $ocations. *s a resu$tA 8*Ns are

preferred.

7N connecti!ity(8ire$ess techno$ogies such as radioA infraredA and microwave

are popu$ar options to connect *Ns in situations where connectivity options such

as $eased $inesA or IS6N are not avai$a0$e .



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+%$+ SSIN1ENT +

1. 8hat are the different kinds of ca0$esG

2. /ow coa,ia$ ca0$e madeG

3. 8hat are advantages of coa,ia$ ca0$esG4. /ow are made twisted pair ca0$esG

%. 8hat are the different types of twisted pair areG

). 8hat is S&'A ;&'G-. 8hat is #I L "5IG

. /ow S&' is protected from #I L "5IG

. /ow is made 5i0er Optica$ Ca0$eG17. 8hat are the *dvantages of 5i0er Optica$ Ca0$esG

11. 8hat is NICG

12. /ow NIC is supported for NetworkingG

>i!e and Eight 1arks 6uestionB

1. 6escri0e the networkingG /ow networking is he$pfu$G

2. 8hat is the difference 0etween a hu0 and a switchG

3. ,p$ain a0out OSI #ode$G

4. /ow is a data packet routed to the destination computerG%. 8hy does the transport $ayer add rror Correction Code CC! to each packetG

). 8hat is the ro$e of NIC at the physica$ $ayerG-. 8hy is Carrier Sense #u$tip$e *ccess with Co$$ision 6etection CS#NC6! used in 0us

topo$ogyG

. 8hy is token passing used in the ring topo$ogyG

. 8hat is the advantage of ring topo$ogyG



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17. In 5u$$ #esh topo$ogyA if one device fai$sA the data trave$ing a$ong the network can

0e routed through another device. ustify your answer.11. In Star+us &opo$ogyA if any of the computers fai$s on the star topo$ogyA it wi$$ not

affect the entire network. ustify your answer.

12. 8hy is 0andwidth and distance important considerations for transmitting signa$s over a

transmission mediumG13. ;sing switches prevents distortion of signa$s. &rue(5a$se. ustify your answer.

14. 8hat are the disadvantages of Optica$ fi0er ca0$esG1%. 8hat are the advantages of using inte$$igent hu0sG

1). 6ifferentiate 0etween cutthrough switching and storeandforward switching.

1-. * 'CI NIC is faster than an IS* NIC. &rue(5a$se. ustify your response.

1. Sketch and e,p$ain OSI reference mode$. 27131. ,p$ain two types of twisted pair ca0$es with diagram. 2713

27 ,p$ain the services provided 0y 'hysica$ and 6ata ink $ayers. 2713

21. ,p$ainA how the transmission of data occurs in optica$ fi0ers in detai$.

Chapter#-

NET7O) 2)OTOCO3S.

-%$3ower#3ayer 2rotocols

In the previous chapterA you $earned a0out the different hardware components used in *N sAsuch as ca0$esA hu0sA and switchesA to esta0$ish connectivity among computers. Dou o0servedthat these devices transmit signa$s 0etween computers and sometimes increase the signa$

strength. In a *NA there are mu$tip$e computers that need to communicate with one another.

5or e,amp$eA consider the network represented in 5igure in which five computers are connected0y using a switch.



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5igure4.1@ Computer connected using a switch

Suppose Node * sends data to Node +. In this caseA Node * is the source nodeA and Node + isthe destination node. &hereforeA when sending dataA the source node shou$d provide the address

of the destination node so that data reaches the destination correct$y. In additionA the destination

node shou$d 0e a0$e to inform the source node a0out the receipt of data. &his addressing and

transmission of data 0etween computers on a network is hand$ed 0y network protoco$s.

* network protoco$ is defined as the ru$esA or communication formatsA that have 0een agreed

upon 0y the devices that need to communicate. Network protoco$s main$y define the fo$$owingaspects of communication@

FAddressing method used by the devices:5or e,amp$eA in 5igure 4.1A the computers can addresseach other 0y their names or 0y the address assigned to each computer. Node * can 0e

addressed as 1A Node + as 2A and Node C as 3.

!ata format:Computers and devices shou$d send and receive data in a format that can 0eunderstood 0y one another.

F "eliability of data transfer:In some casesA network protoco$s ensure that data transfers on anetwork are re$ia0$e.

F Speed of communication:Network protoco$s p$ay an important ro$e in determining the speed

of data transfer on the network.

In additionA some network protoco$s define the manner in which users access network data. 5ore,amp$eA if a user visits a 8e0 site on the InternetA data is transmitted 0etween the 8e0 site and

the user?s computer. Network protoco$s such as /&&' /yper &e,t &ransfer 'rotoco$! define the

manner in which the data is presented to the user.



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*s network protoco$s need to perform mu$tip$e tasksA it is practica$$y impossi0$e to deve$op a

sing$e protoco$ that can manage a$$ these tasks. &hereforeA different protoco$s have 0eendeve$oped to operate at various $ayers of the OSI reference mode$. 5or e,amp$eA protoco$s at the

transport $ayer ensure re$ia0$e transmission of data on the networkA whereas the network $ayer

protoco$s are responsi0$e for addressing data to computers on a network. 'rotoco$s at the

app$icationA sessionA and presentation $ayers determine the kind of data that is accessi0$e to usersand the manner of accessing the data. +ased on the $ayers at which the protoco$s operateA

network protoco$s are 0road$y c$assified as fo$$ows@

Lo!er'layer protocols@(iddle'layer protocols

)igher'layer protocolsower$ayer protoco$s operate at the physica$ and the data$ink $ayers of the OSI reference

mode$ and perform the fo$$owing functions@

F &ransmitting data 0etween two devices on a network on a pointtopoint 0asis.

F nsuring that the data transmission 0etween the devices on a network is error free.

8hen a device sends data to another device on a networkA the data is converted into data packets

at the network $ayer and then passed on to the data$ink $ayer. &he protoco$ operating at the data$ink $ayer converts these packets into frames and then reads the destination address on the data

packets. &he protoco$ then adds the #*C address of the destination device to the data frames

and passes the frames to the physica$ $ayer. *t the physica$ $ayerA the frames are converted into

signa$s and transmitted across the network. On reaching the destinationA signa$s are converted0ack into data frames. If the data frames are received correct$yA an acknow$edgement frame may

0e sent to the source. If the acknow$edgement frame is not receivedA the source resends the data

frames for a fi,ed num0er of retriesA after which the connection is timed out.

ower$ayer protoco$s a$so provide media access to the devices when they need to send data.

&he media used on a network can 0e physica$ mediaA such as ca0$es or wire$ess mediaA such asinfrared and radio waves. 5or a device to transmit dataA it needs to access the transmission

medium on the network. /oweverA there may 0e mu$tip$e devices that need to send dataA and a$$

these devices may access the ca0$e simu$taneous$y. #edia access on a network needs to 0eregu$ated 0ecause mu$tip$e devices may transmit signa$s simu$taneous$y over the ca0$eA resu$ting

in a co$$ision of signa$s. &his co$$ision resu$ts in corruption of signa$s and $oss of data.

5o$$owing are the common $ower$ayer protoco$s used in *Ns@

@ )C net

@ Ethernet@ Token )ing

@ >i4er "istri4uted "ata Inter&ace />""I!

&he fo$$owing topics detai$ the features of each of these protoco$s. &he functions and features ofthe common midd$e$ayer and higher$ayer protoco$s used in *Ns are detai$ed in the ne,t

sections.

Basic of networking 3!


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*.1 A+C net

*"C net or *ttached "esource Computer Network is one of the o$dest $ower$ayer protoco$s

used in *Ns. *"C net was deve$oped in the $ate 1-7s 0y an organiBation ca$$ed 6ata point.

Initia$$yA *"C net used to support data transmission rates from 1%) K0ps to 2.% #0ps. aterA

howeverA *"C net supported speeds of up to 17 #0ps. *"C net uses the tokenpassing schemeto provide media access to the devices on the network.

&he frame format used 0y *"C net to transmit data can 0e 0road$y divided into the fo$$owing

three parts@

F /eader@ Contains information a0out the source and destination nodes.

F 6ata@ Contains information a0out the siBe of data and the actua$ data.

F &rai$er@ Contains Cyc$ic "edundancy Checks C"Cs! for error detection.

SO/ SI6 6I6 Count 6ata C"C

5igure 4.2@ *"C net 6*&* 5rame

In 5igure you can o0serve that the header consists of three components@ SO/ Start of /eader!A

SI6 Source I6!A and 6I6 6estination I6!. &o a destination deviceA the SO/ indicates the

0eginning of the header. &he SI6 contains the address of the source deviceA whereas the 6I6contains the address of the destination device.

6ata part consists of two componentsA Count and 6ata. &he Count component contains

information a0out the siBe of data whi$e the 6ata component contains the actua$ information to0e transmitted. 5or e,amp$eA a va$ue of %) in the Count 5ie$d indicates that the frame contains

%) 0ytes of data. &he destination devices use the information in the Count 5ie$d to check

whether the entire data is received.

&he fo$$owing are the main features of *"C net@

F *"C net supports coa,ia$ and twistedpair ca0$es as we$$ as optica$fi0er ca0$es.

F *"C net supports the starA 0usA and ring topo$ogies. 6epending on the re9uirement of thenetworkA an appropriate topo$ogy can 0e se$ectedA there0y optimiBing ca0$e $engths.

F *"C net uses the token passing systemA which prevents co$$isions on the network. *s a resu$tA

there is no data $oss due to co$$isions.

/oweverA *"C net has the fo$$owing disadvantages@

F &he ma,imum frame siBe supported 0y *"C net is %7 0ytes. &hereforeA mu$tip$e data frames

need to 0e generated if the amount of data to 0e transferred is $arge. 5or e,amp$eA to transfer a

27 K+ fi$eA *"C net generates appro,imate$y 47 frames.

F *"C net re9uires an *CK frame in response to every 6ata frame. &hereforeA if the . *mount

of data transferred is $argeA the num0er of *CK frames is a$so highA resu$ting in increased

Basic of networking 3"


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network traffic. In additionA the time re9uired for a data transfer increases 0ecause the source

node re$eases the token on$y after it receives the *CK frames for a$$ the 6ata frames sent.&hereforeA other devices on the network need to wait $onger for the token.

F &he ma,imum num0er of nodes supported in a sing$e *"C net *N is 2%%.

F *"C net supports a ma,imum datatransfer speed of 17 #0ps.

&he disadvantages of *"C net severe$y affect the network performance if the amount of data

transferred is highA and the traffic generated in *"C net *Ns may s$ow down the network

considera0$y. &hereforeA newer protoco$s such as thernet and &oken "ing are preferred over*"C net.

*.2 ,thernet

thernet is the most popu$ar $ower$ayer protoco$ used in *Ns. thernet was first deve$oped in

1-2 at the :ero, 'a$o *$to "esearch Center '*"C!. &his version of thernet supported a data

transfer speed of 2.4 #0ps. &here have 0een severa$ enhancements to the origina$ version ofthernetA and the current versions support network transmission speeds ranging from 17 #0ps

to 1A777 #0ps.

thernet uses a techni9ue ca$$ed the Carrier Sense #u$tip$e *ccess(Co$$ision 6etection

CS#*(C6!A a$so known as I 72.3A to provide media access to devices on the network.

* carrier is a signa$ containing some specific data. CS#*(C6 works in the fo$$owing manner@

F &he device that needs to send data checks the ca0$e for any signa$s. &his is ca$$ed the Carrier

Sense.

F If no carrier is foundA the device accesses the medium and transmits data signa$sA 0ut it is

possi0$e that mu$tip$e devices start transmitting signa$s simu$taneous$y. &his is ca$$ed #u$tip$e*ccess.

F 8hen mu$tip$e devices transmit signa$s simu$taneous$yA a co$$ision occurs. &he device nearestto the point of co$$ision detects the co$$ision and informs a$$ the devices a0out the co$$isionA

which is ca$$ed Co$$ision 6etection. &he devices then wait for a random period of time 0efore

retransmitting the data.



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5igure 4.3 @ #edia *ccess in thernet

In 5igure 4.3A Node * as we$$ as Node C needs to send data. In Step 1A 0oth these computers

check for any signa$s in the ca0$e. &he nodes do not detect any signa$ and 0egin data transfer

simu$taneous$yA as shown 0y Step 2. &his resu$ts in a co$$isionA as shown 0y Step 3. 8hen aco$$ision occursA the device nearest to the point of co$$isionA which is Node +A informs a$$ the

devices on the network a0out the co$$ision. *s a resu$tA Nodes * and C wait for a random periodof timeA 0efore retransmitting the data.

5rom the e,amp$e discussed in 5igure 4.3A it is c$ear that a device in an thernet *N cannotsend and receive data simu$taneous$y. 5or e,amp$eA when Node * transmits dataA the ca0$e

carries the signa$ and thereforeA the other devices cannot transmit simu$taneous$y. &his type of

communication is ca$$ed ha$fdup$e, communicationA which means that a device on a networkcan either send data or receive dataA 0ut cannot send and receive different data simu$taneous$y.

/a$fdup$e, communication can 0e e,treme$y s$ow if the network contains a $arge num0er ofnodes. 5or e,amp$eA imagine an thernet *N with 1%7 computers. ach computer needs tosend as we$$ as receive data from other computers or devices on the network. *s there are 1%7

computers on the networkA the pro0a0i$ity of the ca0$e carrying a signa$ at a given point oftime

is high. &hereforeA the nodes need to wait for an additiona$ time period 0efore they can accessthe ca0$e. In additionA the increase in the num0er of nodes a$so increases the pro0a0i$ity of



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co$$isions. &o overcome these $imitations of ha$fdup$e, communicationA fu$$dup$e,

communication was introduced.

In fu$$dup$e, communicationA the nodes on the network can send and receive data

simu$taneous$y. /oweverA fu$$dup$e, communication does not use the CS#*$C6 techno$ogy

for providing media access to devices. InsteadA fu$$dup$e, communication is accomp$ished withthe he$p of a device that can transmit data 0ased on the destination address. ;sua$$yA a switch is

used in fu$$dup$e, communication. &o understand fu$$dup$e, communication in thernet*NsA consider the network represented in 5igure 4.4.

5igure 4.4@ 5u$$6up$e, Communication in thernet

5igure represents a *N in which four computers are connected 0y using a switch. Consider the

segment of the network 0etween Nodes * and the switch. &he ca0$e in this segment is used

either 0y Node * or the switch 0ut not 0y other devices on the network. In fu$$dup$e,communicationA one pair of the ;&' ca0$es is used for transmitting data from Node * to the

switch whi$e the other pair transmits data from the switch to Node *. *s separate pairs are used

for sending and receiving dataA co$$isions can 0e comp$ete$y avoided. &he other nodes on the

network communicate with the switch in a simi$ar mannerA and thereforeA co$$isions areprevented in the entire network.

5rom 5igure you can o0serve that the switch p$ays an important ro$e in forwarding data framesto their destination. *$$ the computers on the network send data frames to the switch. &he switch

checks the destination #*C addresses of these data frames and forwards them to the

corresponding ports. 5or e,amp$eA the data for Node * is forwarded to 'ort 1 whi$e the data forNode + is forwarded to 'ort 2.



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In additionA fu$$dup$e, communication dou0$es the effective throughput 0ecause sending and

receiving of data takes p$ace simu$taneous$y. 5or e,amp$eA a 17 #0ps ;&' ca0$e can producean effective throughput of 27 #0ps.

Ethernet Communication

In thernet *NsA the source node sends data to a$$ the nodes on the network and not on$y to the

destination node. &his process is known as 0roadcasting. *$$ the nodes check the destination#*C address on the data frame. &he device with the corresponding #*C address accepts the

data whi$e the other devices ignore it.

5igure 4.%@ 6ata 5rames +roadcast in thernet *N

In 5igure 4.%A Node * needs to send data to Node +. Node * creates a data frame and inc$udesthe destination #*C address of Node + in the frame and 0roadcasts the frame across the

network. *$$ the devices check the destination #*C address of the data frame. *s the

destinationA #*C address corresponds to Node +A on$y Node + accepts the data.

*$though the origina$ thernet standards provides speeds of up to 17#0psA newer deve$opments

to the thernet standard have resu$ted in speeds of 177 #0psA ca$$ed 5ast thernetA and 1777

#0psA ca$$ed >iga0it thernet. &hese newer standards are discussed in the fo$$owing su0topic.

Fast ,thernet and -igabit ,thernet

*$though 17#0ps was once sufficientA the demand for higher 0andwidth $ed to the deve$opment

of a newer standardA ca$$ed 5ast thernetA which provides datatransfer speeds of up to 177

#0ps. 5ast thernet a$so uses CS#*(C6 to provide media access to devices on the network.&he fo$$owing are the important features of 5ast thernet@



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F ac/!ard co0patibility:5ast thernet is 0ackward compati0$e with the 17#0ps thernet

standard. &hereforeA the NICs and switches that are compati0$e with 5ast thernet can a$so 0eused with 17 #0ps thernet.

F nteroperability: 5ast thernet a$$ows interopera0i$ity with e,isting 17 #0ps thernet

networks. 5or e,amp$eA if a *N is divided into three segmentsA one segment can use 5astthernetA whi$e the other two segments can use the 17 #0ps thernet standard. &his is

e,treme$y he$pfu$ when computers in a particu$ar segment need to communicate at a faster ratethan the computers in the other segments. /oweverA for interconnecting the two standardsA a

C$ass I repeater is re9uired. 5ast thernet divides repeaters into the fo$$owing types@

Class repeater:*cts as an interface 0etween the 5ast thernet and thernet standards

0ut does not amp$ify the signa$.

Class repeater:*mp$ifies the signa$ 0ut cannot connect the two standards.

Full'duplex operation: 5ast thernet a$so supports fu$$dup$e, communication for

*Ns.

&hereforeA the effective throughput 0etween two devices can 0e up to 277 #0ps.

Star topology( 5ast thernet supports on$y the star topo$ogy for connecting

computers and devices on the network. >iga0it thernet was deve$oped to connect*N 0ack0one networks. NowadaysA >iga0it thernet is a$so used on *N

workstations. >iga0it thernet a$so uses the CS#*(C6 techno$ogy for providing

media access and is 0ackward compati0$e with the 5ast thernet and thernetstandards.

Dou have $earned a0out the features of thernet and many of the thernet standards used in*Ns. thernet is the most popu$ar protoco$ used in *N for the fo$$owing reasons@

Supports coa,ia$A twistedpairA and optica$fi0er ca0$es.

Supports the 0us and star network topo$ogies.

Costs $ess to set up than *"C netA &oken "ingA or 566I *Ns.

In most *NsA devices need to transmit data intermittent$y and not on a continuous

0asis.

&he CS#*(C6 method of providing media access is 0est suited for this situation.

Newer standards such as 5ast thernet and >iga0it thernet offer network administrators

the f$e,i0i$ity to se$ect these standards on network segments where speed is important.

&he fo$$owing are the disadvantages of thernet@

It is impossi0$e to predict the e,act period of time a node needs to wait 0efore it can starttransmitting data. &hereforeA thernet cannot 0e used in *Ns where the de$ays can 0e

predicted. &his is an inherent $imitation of thernet.

Nodes in an thernet *N 0roadcast data across the networkA resu$ting in an increase of

network traffic. In networks with a $arge num0er of computersA 0roadcasting

significant$y increases network traffic. &he network needs to 0e divided into mu$tip$e



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0roadcast domains to overcome this issue. &his issue is usua$$y overcome with the he$p

of switches for interconnecting nodes and segments.In most *N sA speed is the primary considerationA and thereforeA the disadvantages of thernet

are not fe$t. *s a resu$tA thernet remains the most popu$ar protoco$ for *N s. 5or *N s that

re9uires 0etter performance in terms of data transferA protoco$s such as &oken "ing and 566I

are preferred.

-%- Token )ing

&oken "ing was deve$oped 0y I+# in the 1-7s as an a$ternative to thernet and to overcome

the disadvantages of thernet. Initia$$yA &oken "ing offered speeds of 4 #0psA which was $aterupdated to 1) #0ps.

ike *"C netA &oken "ing a$so uses the tokenpassing scheme to provide media access to the

network devices. /oweverA &oken "ing manages the token access to the network devices in adifferent manner. In &oken "ing *NsA an empty token circu$ates among the different devices

on the network. On receiving the tokenA a device appends data to the token and transmits it

across the network. &he other devices on the network check the destination addressA and thedevice with the corresponding destination address makes a copy of the data. &he origina$ data

frame continues circu$ating on the network and reaches the source device. &he source device

checks the data frame and recogniBes that the data had originated from it and then re$eases thetoken for other devices to use. &hereforeA in &oken "ing *NsA a device can ho$d the token on$y

unti$ the origina$ data frame comes 0ack to the source device. *s a resu$tA it is possi0$e that a

device may need to re$ease ? the token 0efore it is a0$e to transmit a$$ the data framesA &he device

then waits for its turn and the remaining framesA &his in contrast to *"C net where the token isre$eased on$y after the data transfer is comp$eteA In 5igure the media access and data

transmission occur as fo$$ows@



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5igure@ #edia *ccess in token "ing



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F Step 1@ Node * needs to transmit data frames 'A JA "A and S to Node 6. Node * receives the

empty token anti starts transmitting the frames one after the other.

Step 2@ 5rame ' is read 0y Node 6A which makes a copy of the frame. In the meantimeA Node *

has a$ready transmitted frames J and ".

Step 3@ 5rame ' reaches Node * 0efore it can transmit frame S. Node * re$eases the tokenA and

frame " needs to wait ti$$ Node * receives the empty token again.

&he &oken "ing *N represented in 5igure 4.) uses the ring topo$ogy. /oweverA &oken "ing

*Ns can support the star topo$ogy too. In factA most &oken "ing *Ns are imp$emented usingthe star topo$ogy with the he$p of devices ca$$ed #u$tistation *ccess ;nits #*;s!A which are

the &oken "ing e9uiva$ent of thernet hu0s.

5igure represents a &oken "ing *N in which computers are connected using #*;s

5igure 4.)@ &oken "ing *N with #*;s

Dou have $earned a0out the mediaaccess method used 0y &oken "ing. &he ne,t su0topic

detai$s the &oken "ing frame format. &oken "ing 5rame 5ormat &oken "ing uses two types of

frames to transmit data across the network@ token and data frame. &he token is the empty framethat circu$ates around the network to provide media access. 6evices that need to send data

convert the token into a data frame and send it across the network. 8hen the data transmission

is comp$eteA the source device destroys the data frame and re$eases a new token frame. &hetoken consists of the fo$$owing components@

tarting deli0iter:Indicates the 0eginning of the token.

FAccess control field:6efines the access of devices to the token. &his fie$dA in turnA consists of

the fo$$owing@



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"riority field:Contains a va$ue 0etween 777 and 111A which is set 0y the device that

re$eases the token into the network. 5or a network that is set up for the first timeA thisva$ue is set 0y the network server. On$y devices whose priority va$ue is greater than this

va$ue may use the token. 5or e,amp$eA if the token circu$ating on the network has a

priority va$ue of 771A on$y those devices with an e9ua$ or higher priority va$ue may use

this token. &he priority va$ues of devices are assigned 0y the network administrator.

Token &ield(On receiving an empty tokenA a device modifies this fie$d 0efore sending

the data to indicate that the token is not empty. &his fie$d can take a va$ue of either 7 or1. 7 indicates an empty frame whi$e 1 indicates that the token is in use.

1onitor &ield(&he network serverA or the *ctive #onitorA uses this fie$d to monitor the

token activity. &he *ctive #onitor sets this va$ue to 1 when generating a token. &he

va$ue is reset to 7 when a device uses the frame. &hereforeA an empty token can 0e

recogniBed 0y a token fie$d va$ue of 7 and a monitor fie$d va$ue of 1.

)euest 2riority &ield(On a networkA there may 0e devices that may need to send highpriority information. Such devices can use this fie$d to get faster access to the token. *

device can change the "e9uest 'riority fie$d to its priority va$ue and inform the device

that is re$easing the token to increase the va$ue of the 'riorit

New New Basic of Networking

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