December
1998 QUESTION 2 Total Marks: 20 Marks |
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| (a) | Briefly describe an advantage and a disadvantage
of message switching.
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| (b) | The message switching technique is
subject to two kinds of delays. What are these delays?
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| (c) | Briefly compare circuit switching and packet
switching.
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| (d) | Packet switching may use the
datagram technique or the virtual circuit technique. The first form does not guarantee that packets will be delivered in order, and requires that they be acknowledged. Explain why this is the case, and why the same concerns do not apply to the virtual circuit approach.
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| (e) | Suppose you have to send a 2048-byte message.
You may use a virtual circuit which has a set-up time of 2 seconds and a transmission rate
of 256 bytes per second. Alternatively, you could use a packet-switched network where each
packet may contain up to 256 bytes in total, and on average one packet takes one second to
pass through the network. Decide which will be the more efficient approach. Show your working. You will need to make an additional assumption in order to do the calculation. State your assumption carefully. |
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