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Switching
ดร . อนั�นัต์� ผลเพิ่ �มAnan Phonphoem, Ph.D.
[email protected]://www.cpe.ku.ac.th/~anan
Computer Engineering DepartmentKasetsart University, Bangkok, Thailand
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Switching Point-to-point connection (Mesh)
wasteful Multipoint connection (Bus)
Distance (collision Domain) Number of devices
Switch
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Switched Network
Switching Methods
Circuit switching Message switchingPacket switching
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Circuit switched network
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Switch
Creates a temporary connection between input/output
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A folded switch
Switching Methods
Circuit switching Message switchingPacket switching
Space-division Time-division
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Space-Division Switches:Crossbar Switches
•Using electronic micro-switches (transistors)•Low efficiency (<25% use)
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Multistage Switch
• More efficiency• Blocking
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Switching path
• Also provide multiple paths
Switching Methods
Circuit switching Message switchingPacket switching
Space-division Time-division
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TDMTime-slot interchange (TSI)
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Time-slot interchange
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Space VS. Time-Division Space-division switching
+ Instantaneous- # of cross points
Time-division switching + No cross point
- Create delay
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Time-space-time (TST) switch
Other combinations: TSST, STTS, etc.
Switching Methods
Circuit switching Message switchingPacket switching
Datagram Virtual circuit
SVC PVC
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Circuit switching weakness Design for voice (telephone)
Non-voice transmission is bursty Data rate
Assume a single data rate for both ends
Inflexibility Same path (no adaptation)
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Datagram approach
Each packet is treated independentlyPacket is called Datagram
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Multiple channels in datagram approach
A XB Y
B
Switching Methods
Circuit switching Message switchingPacket switching
Datagram Virtual circuit
SVC PVC
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Virtual Circuit Same route – choose at start PVC (Permanent VC)
Leased Line SVC (Switched VC)
Dial-up
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Switched virtual circuit (SVC)
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Switched virtual circuit (SVC)
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Switched virtual circuit (SVC)
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Circuit-switched VS. Virtual-circuit connection
Path VS. route Dedicated VS. sharing
Circuit-switched connection Virtual-circuit connection
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Virtual Circuit in WAN
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VCI
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VCI Phases
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Switching
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Source-to-destination data transfer
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SVC setup request
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SVC setup acknowledgment
Switching Methods
Circuit switching Message switchingPacket switching
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Message switching
