Download Switching (Wide Area Network) - Department of Computer Engineering

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Transcript 
Switching
ดร. อนันต์ ผลเพิม่
Anan Phonphoem, Ph.D.
[email protected]
http://www.cpe.ku.ac.th/~anan
Computer Engineering Department
Kasetsart University, Bangkok, Thailand
Switching

Point-to-point connection (Mesh)


Multipoint connection (Bus)



wasteful
Distance (collision Domain)
Number of devices
Switch
2
Switched Network
3
Switching Methods
Circuit switching
Packet switching
Message switching
Circuit switched network
5
Switch
Creates a temporary connection between input/output
6
A folded switch
7
Switching Methods
Circuit switching
Space-division
Packet switching
Time-division
Message switching
Space-Division Switches:
Crossbar Switches
•Using electronic micro-switches (transistors)
•Low efficiency (<25% use)
9
Multistage Switch
• More efficiency
• Blocking
10
Switching path
• Also provide multiple paths
11
Switching Methods
Circuit switching
Space-division
Packet switching
Time-division
Message switching
TDM
Time-slot interchange (TSI)
13
Time-slot interchange
14
Space VS. Time-Division

Space-division switching
+ Instantaneous
- # of cross points

Time-division switching
+ No cross point
- Create delay
15
Time-space-time (TST) switch
Other combinations: TSST, STTS, etc.
16
Switching Methods
Circuit switching
Packet switching
Datagram
Message switching
Virtual circuit
SVC
PVC
Circuit switching weakness

Design for voice (telephone)


Data rate


Non-voice transmission is bursty
Assume a single data rate for both ends
Inflexibility

Same path (no adaptation)
18
Datagram approach
Each packet is treated independently
Packet is called Datagram
19
Multiple channels
in datagram approach
B
AX
BY
20
Switching Methods
Circuit switching
Packet switching
Datagram
Message switching
Virtual circuit
SVC
PVC
Virtual Circuit


Same route – choose at start
PVC (Permanent VC)


Leased Line
SVC (Switched VC)

Dial-up
22
Switched virtual circuit (SVC)
23
Switched virtual circuit (SVC)
24
Switched virtual circuit (SVC)
25
Circuit-switched
VS. Virtual-circuit connection
Circuit-switched connection


Virtual-circuit connection
Path VS. route
Dedicated VS. sharing
26
Virtual Circuit in WAN
27
VCI
28
VCI Phases
29
Switching
30
Source-to-destination data
transfer
31
SVC setup request
32
SVC setup acknowledgment
33
Switching Methods
Circuit switching
Packet switching
Message switching
Message switching
35
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