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8/10/2019 Chap8 Circuit Switching
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Spring 2006 Data Communications, Kwangwoon University 8-1
Chapter 8
Circuit Switching & Telephone Network
1. Circuit switching
2. Telephone network
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Spring 2006 Data Communications, Kwangwoon University 8-2
Switching
Whenever we have multiple devices, we have the
prolem o! how to connect them to make one"one"
one communication possile.
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Spring 2006 Data Communications, Kwangwoon University 8-3
Circuit"switched Network
# Creates a direct ph$sical connection etween two devices
such as phones or computer
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Spring 2006 Data Communications, Kwangwoon University 8-4
% Circuit Switch
# evice with n inputs and m outputs that creates atemporar$ connection etween an input link and outputlink
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% 'olded Switch
# n"$"n !olded switch can connect n lines in !ull"duple(
mode
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Spring 2006 Data Communications, Kwangwoon University 8-6
Circuit Switching Technologies
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Spring 2006 Data Communications, Kwangwoon University 8-!
Crossar Switch
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Spring 2006 Data Communications, Kwangwoon University 8-8
Crossar Switches) *rolem
# The numer o! switches is huge.
+ connect n inputs $ m output "" reuire n - m
crosspoint.
+ ( ) 1/// input, 1/// output 0 1,///,/// crosspoint
# ne!!icient
+ !ewer than 23 o! the crosspoints are in use at a given
time.
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Spring 2006 Data Communications, Kwangwoon University 8-"
4ultistage Switch
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Spring 2006 Data Communications, Kwangwoon University 8-10
Switching *ath
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Spring 2006 Data Communications, Kwangwoon University 8-11
4ultistage Switches) %dvantage
# %dvantage) The numer o! crosspoints+ single"stage switch
5 need 22 crosspoint61 - 17
+ multistage switch
5 !irst"stage ) 1/ crosspoint6 - 27 - 9 / crosspoint
5 second"stage ) : crosspoint6 -7 - 2 9 18 crosspoint
5 third"stage ) 1/ crosspoint6 - 27 - 9 / crosspoint
total numer o! crosspoint ) ;8
# isadvantage) Call locking
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Spring 2006 Data Communications, Kwangwoon University 8-12
T4, with and without TS
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Spring 2006 Data Communications, Kwangwoon University 8-13
Time"Slot nterchange
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Spring 2006 Data Communications, Kwangwoon University 8-14
T4
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Spring 2006 Data Communications, Kwangwoon University 8-1
Cominations
# Space ivision SW ) Simple 6=7, Crosspoints 6>7
# Time ivision SW ) *rocessing dela$ 6>7
# Space"and Time"ivision Switching cominations
take advantage o! the est o! oth
+ TST6time"space"time7
+ TSST6time"space"space"time7
+ STTS6space"time"time"space7
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Spring 2006 Data Communications, Kwangwoon University 8-16
TST Switch
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Spring 2006 Data Communications, Kwangwoon University 8-1!
% Telephone S$stem
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Spring 2006 Data Communications, Kwangwoon University 8-18
Telephone Companies)
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Spring 2006 Data Communications, Kwangwoon University 8-1"
A%T%s
# % A%T% can e a small or large metropolitan area
# ntra"A%T% services are provided $ local
e(change carriers
+ AC 6ncument Aocal (change Carriers7
+ CAC 6Competitive Aocal (change Carriers7
# nter"A%T% services are handled $ >Cs 6nter"
(change Carriers7+ Called long"diatance companies
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Spring 2006 Data Communications, Kwangwoon University 8-20
Switching =!!ices in a A%T%
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Spring 2006 Data Communications, Kwangwoon University 8-21
*=* 6*oint o! *resence7
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Spring 2006 Data Communications, Kwangwoon University 8-22
Botar$ and Touch"Tone ialing