1. CS 447 Networks and Data Communication
Comparison of Circuit-Switching, Virtual-Circuit and
Datagram Data Transmissions
Department of Computer Science
Southern Illinois University Edwardsville
Fall, 2015
Dr. Hiroshi Fujinoki

2. CS 447 Networks and Data Communication
Circuit Switching Data Transmission
Host A
Host X
Host Y
Host B
Switch S1
Switch S2
Switch S3
Switch S4
Switch S5
Signaling Message
(Path Setup)
Routing
Routing
ACK
ACK
ACK
ACK
Routing
Routing

3. CS 447 Networks and Data Communication
Circuit Switching Data Transmission
File
Host A
Host X
Host Y
Host B
Switch S1
Switch S2
Switch S3
Switch S4
Switch S5
Dedicated Pipe (path)
Blocked

4. CS 447 Networks and Data Communication
Circuit Switching Data Transmission
 Path set-up is required before data transmission starts
Major Properties:
 Data will be transferred as a continuous stream of bits
 All data (all bits) follow exactly the same path
(order of bits transmitted by a sender is preserved at a receiver)
 No resource sharing (a path is dedicated resource for your transmission)
 Path set-up delay is always required
 Once data transmission starts, no overhead (i.e., node major switching
delay) at each switch on a path (since the path is set up).
 Transmission rate is guaranteed (your data will be delivered within
certain amount of time).
 Highest cost data transmission
(= highest quality)

5. CS 447 Networks and Data Communication
Datagram Data Transmission 1 2 3
File
Host A
Host X
Host Y
Host B
Switch S1
Switch S2
Switch S3
Switch S4
Switch S5 3 2 1
Routing

6. CS 447 Networks and Data Communication
Datagram Data Transmission
Host A
Host X
Host Y
Host B
Switch S1
Switch S2
Switch S3
Switch S4
Switch S5 3 2 1
Routing

7. CS 447 Networks and Data Communication
Datagram Data Transmission
Host A
Host X
Host Y
Host B
Switch S1
Switch S2
Switch S3
Switch S4
Switch S5
Routing 3 2 1
Routing

8. CS 447 Networks and Data Communication
Datagram Data Transmission
Host A
Host X
Host Y
Host B
Switch S1
Switch S2
Switch S3
Switch S4
Switch S5 1 3 2

9. CS 447 Networks and Data Communication
Datagram Data Transmission
Host A
Host X
Host Y
Host B
Switch S1
Switch S2
Switch S3
Switch S4
Switch S5 3 1 2

10. CS 447 Networks and Data Communication
Datagram Data Transmission
Host A
Host X
Host Y
Host B
Switch S1
Switch S2
Switch S3
Switch S4
Switch S5 2 3 1

11. CS 447 Networks and Data Communication
Datagram Data Transmission
Host A
Host X
Host Y
Host B
Switch S1
Switch S2
Switch S3
Switch S4
Switch S5 1 2 3 1 2 3

12. CS 447 Networks and Data Communication
Datagram Data Transmission
More packets than S1 can handle could arrive
Host A
Host X
Host Y
Host B
Switch S1
Switch S2
Switch S3
Switch S4
Switch S5 3 2 1 3 2 1

13. CS 447 Networks and Data Communication
Datagram Data Transmission
Switches in datagram networks
are called “routers”
Host A
Host X
Host Y
Host B
Switch S1
Switch S2
Switch S3
Switch S4
Switch S5
Packet Dropped 3 3 2 2 1 1
NACK (Error)

14. CS 447 Networks and Data Communication
Datagram Data Transmission
Major Properties:
 Path set-up is NOT required before data transmission starts
 Data will be transferred as a collection of packets
 All packets may not follow the same path
(order of bits transmitted by a sender is NOT preserved at a receiver)
 Network resource is shared
 Path set-up delay is NOT required
 After data transmission starts, high overhead (i.e., major switching delay)
at each switch on a path (error control and flow control are performed for
each packet plus “routing” now have to be performed for every packet).
 Transmission rate is NOT guaranteed (“Best-Effort Service).
 Lowest cost data transmission
(= lowest quality)

15. CS 447 Networks and Data Communication
Datagram Data Transmission
Dropped packet
Host A
Host X
Host Y
Host B
Switch S1
Switch S2
Switch S3
Switch S4
Switch S5
NACK (Error) 3
Even a NACK message could be lost

16. CS 447 Networks and Data Communication
Virtual Circuit Data Transmission
Path set-up is same as Circuit-Switching
Host A
Host X
Host Y
Host B
Switch S1
Switch S2
Switch S3
Switch S4
Switch S5
Signaling Message
(Path Setup)
Routing
ACK

17. CS 447 Networks and Data Communication
Virtual Circuit Data Transmission 1 2 3
File
Host A
Host X
Host Y
Host B
Switch S1
Switch S2
Switch S3
Switch S4
Switch S5 3 2 1 1 2 1 2 3 1 3 2
Shared Pipe 1 1 2 3 2
(High priority is to
host A - but X can send data as best-effort service)

18. CS 447 Networks and Data Communication
Virtual Circuit Data Transmission
Major Properties:
 Path set-up is required before data transmission starts
 Data will be transferred as a collection of packets
 All data (all packets) follow exactly the same path
(order of bits transmitted by a sender is preserved at a receiver)
 Network resource can be shared (because data is transferred as packets)
 Path set-up delay is required
 After data transmission starts, some overhead (i.e., some switching delay)
at each switch on a path (error control and flow control are performed for
each packet).
 Transmission rate is guaranteed (your data will be delivered within
certain amount of time).
 Medium cost data transmission
(= medium quality)

19. CS 447 Networks and Data Communication
Factors
Circuit-Switching
Virtual Circuit
Datagram
ISDN,
ATM,
Examples
Public Telephone
Internet
Frame Relay
Resource Sharing NO
YES
YES
Dedicated Paths
YES NO NO
Continuous
Transmission
YES NO NO
Path-setup
in advance
YES
YES NO
Busy signal
if dest. busy
YES
YES NO
Major delay
Path setup delay
Path setup delay
Packet routing

20. CS 447 Networks and Data Communication
Factors
Circuit-Switching
Virtual Circuit
Datagram
No overhead
after TX starts?
YES
YES NO
(Packet header)
(Packet header)
Routing delay? NO No
(Almost 0)
YES
(High)
Guaranteed Tx
Bandwidth?
YES
YES NO
Advantages
Guaranteed Quality
Guaranteed Quality
Resource sharing
Resource sharing
Low cost
Non-blocking
High cost
Best Effort Service
Disadvantages
High cost
Poor security
Blocking service
Blocking service
Reliable,
Delay-sensitive
Service that needs
To be available 24Hrs
Applications
Delay-sensitive
Text-base