August
1999 QUESTION 3 Total Marks: 20 Marks |
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questions
SUGGESTED SOLUTIONS |
| (a) | Define and explain the following terms. (i) LAN (ii) WAN (iii) MAN |
[2] [2] [2] |
| (i) LAN Local Area Network. A communications network that serves users within a confined geographical area.
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| (ii) WAN Wide Area Network. A communications network that covers a wide geographical area, such as state or country.
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| (iii) MAN Metropolitan Area Network. A communications network that covers a geographical area such as a city or suburb.
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| (b) | What are the three conventional LAN technologies? | [9] |
| Ethernet. A shared
media LAN. All messages are broadcast to all nodes on the network segment. Token Passing Ring. A communications network access methods that uses a continuously repeating frame (the token) that is transmitted onto the network by the controlling computer. When a terminal or computer wants to send a message, it waits for an empty token. When it finds one, it fills it with the address of the destination station and some or all of its message. FDDI. (Fibre Distributed Data Interface). An ANSI standard token passing network that uses optical fibre cabling and transmits at 100Mbits/sec up to 2 kilometers.
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| (c) | Explain what compression is, and why it is commonly used for video data transmission. | [5] |
| Compression is the
activity of taking data and using some encoding technique to make it occupy less space, so
that it occupies less store, or so that it can be transmitted more quickly. The encoding
may be two-way (giving lossless compression) or one-way (giving lossy compression). The
choice of which to use depends on the use of the data. Compression is used for video because the transmission of uncompressed video data over a computer network requires very high bandwidth. The video data must be compressed before transmission so that frame rate is not compromised. Compression can be done either in hardware or in software. Award marks for these or other valid points.
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