December
1999 QUESTION 3 Total Marks: 15 Marks |
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Switching is needed in data communications
because it is not possible to have a point-to-point connection between
all computers on most networks. |
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| (a) |
List the three steps in circuit switching.
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[3] |
| (b) |
Both message and packet switching techniques
employ the ‘store and forward ’ technique.Describe the differences
between these two techniques. |
[4] |
| (c) |
A public switched telephone network is
circuit-switched.This technique dedicates a physical path between
the two parties.Does circuit switching provide good bandwidth utilization?Explain
your answer. |
[3] |
| (d) |
Suppose you have to send a 4 096 byte message.You may use a virtual circuit which has a set-up time of three seconds and a transmission rate of 256 bytes per second. Each packet has a 2-byte VC number as an overhead. Alternatively,you could use a datagram network where each packet may contain up to 240 bytes of data and 16 bytes of overheads and addressing information.Assume that one packet takes one second to pass through the network. Which approach will be more efficient?Justify
your answer by showing your working. State any additional assumptions
you make. |
[5] |