switching.ppt

8/9/2019 switching.ppt

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Outline

11 INTRODUCTION INTRODUCTION

2 2 CIRCUIT-SWITCHED NETWORKCIRCUIT-SWITCHED NETWORK

3 3 PACKET-SWITCHING PACKET-SWITCHING

4 4 STRUCTURE OF A SWITCH STRUCTURE OF A SWITCH


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INTRODUCTION INTRODUCTION

A network is set o! connecte" "e#ices$

Whene#er we h#e %&'ti('e "e#ices) we h#e the

(ro*'e% o! how to connect the% to %ke one-to-

one co%%&niction (ossi*'e$

The so'&tion is switching$ A switche" network

consists o! series o! inter'inke" no"es) c''e"switches$


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Switche" network


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Three +etho"s o! Switching Three +etho"s o! Switching

Tr"ition'',) three %etho"s o! switching h#e *eenc'ssi!ie" s circ&it switching) (cket switching) n"

%essge switching$

The !irst two re co%%on', &se" to",$ The thir" hs*een (hse" o&t in gener' co%%&nictions *&t sti'' hs

(('ictions$

Pcket switching cn !&rther *e "i#i"e" into two

s&*ctegories) #irt&'-circ&it ((roch n" "tgr%

((roch


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Switching n" TCP.IP /,ers Switching n" TCP.IP /,ers

Switching cn h((en t se#er' ',ers o! the TCP.IP (rotoco' s&ite t the (h,sic' ',er) t the "t-'ink

',er) n" t the network ',er$


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Switche" networks


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CIRCUIT-SWITCHED NETWORKSCIRCUIT-SWITCHED NETWORKS

A circ&it-switche" network consists o! set o! switches

connecte" *, (h,sic' 'inks$

A connection *etween two sttions is "e"icte" (th%"e o! one or %ore 'inks$

Howe#er) ech connection &ses on', one "e"icte"

chnne' on ech 'ink$

Ech 'ink is nor%'', "i#i"e" into n chnne's *, &sing

FD+ or TD+$


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A tri#i' circ&it-switche" network


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As a trivial example, let us use a circuit-switched network to

connect eight telephones in a small area. Communication is

through 4-kHz voice channels. We assume that each link

uses F! to connect a maximum o" two voice channels.

#he $andwidth o" each link is then % kHz. Figure %.4 shows

the situation. #elephone & is connected to telephone '( ) to*( + to %( and 4 to . " course the situation ma change

when new connections are made. #he switch controls the

connections.

Example 1


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As another example, consider a circuit-switched network

that connects computers in two remote o""ices o" a private

compan. #he o""ices are connected using a #-& line leased

"rom a communication service provider. #here are two 4 / %

04 inputs and % outputs1 switches in this network. For each

switch, "our output ports are "olded into the input ports toallow communication $etween computers in the same o""ice.

Four other output ports allow communication $etween the

two o""ices. Figure %.* shows the situation.

Example 2


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Circ&it-switche" network &se" in E0%('e 1


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Three PhsesThree Phses

The ct&' co%%&niction in circ&it-switche"network re2&ires three (hses

connection set&()

"t trns!er) n"

connection ter"own$


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Circ&it-switche" network &se" in E0%('e 3


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E!!icienc, E!!icienc,

The circ&it-switche" networks re not s e!!icient s the

other two t,(es o! networks *ec&se reso&rces re ''octe"

"&ring the entire "&rtion o! the connection$

These reso&rces re &n#i'*'e to other connections$

In te'e(hone network) (eo('e nor%'', ter%inte the

co%%&niction when the, h#e !inishe" their

con#erstion$


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De', De',

A'tho&gh circ&it-switche" network nor%'', hs 'owe!!icienc,) the "e', in this t,(e o! network is %ini%'$

D&ring "t trns!er the "t re not "e',e" t ech

switch4 the reso&rces re ''octe" !or the "&rtion o!the connection$

Dela in a circ it s itched


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Delay in a circuit-switchednetwork

Data transfer


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Dtgr% Networks Dtgr% Networks

In "tgr% network) ech (cket is trete"

in"e(en"ent', o! '' others$

E#en i! (cket is (rt o! %&'ti(cket trns%ission)

the network trets it s tho&gh it e0iste" 'one$

Pckets in this ((roch re re!erre" to s "tgr%s$


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A Dtgr% network with !o&r switches 6ro&ters7

4 3 2 1 1

4

3

2

1

1

2

3

4432 1


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Ro&ting t*'e in "tgr% network


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De',s in "tgr% network


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8irt&'-Circ&it Networks8irt&'-Circ&it Networks

A #irt&'-circ&it network is cross *etween circ&it-

switche" network n" "tgr% network$

It hs so%e chrcteristics o! *oth$


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8irt&'-circ&it network


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8irt&'-circ&it i"enti!ier


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Switch n" t*'e !or #irt&'-circ&it network

So&rce to "estintion "t trns!er in circ&it switch


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So&rce-to-"estintion "t trns!er in circ&it-switch

network


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Set&( re2&est in #irt&'-circ&it network


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Set&( cknow'e"g%ent in #irt&'-circ&it network


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De', in #irt&'-circ&it network

switching.ppt

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