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(a) List three techniques for securing your data in a distributed
environment. [3]
-Encryption/decryption
-Public/private key protocols
-Digital signatures/certificates (1 mark each)
Give credit for valid alternative answers.
(b) Explain the two ways in which an application on one host can
send message to multiple hosts. Which one of the two is less efficient,
and why? [4]
- Multicast: the copy of same message is
sent to different hosts
separately (1 mark)
- Broadcast: would send just one message, which would be picked by
multiple users (1 mark)
- Multicast is less efficient (1 mark)
- Because the same message is sent more than once with different
destination address (1 mark)
Give credit for valid alternative answers.
(c) Explain in detail how it is possible to update or pass information
from a client to a server on the Web. [4]
- Forms enable clients to pass information
to the server (1 mark)
- Also forms activate server procedure to process this information
(1
mark)
- These server procedures are scripted in Common Gateway Interface
(CGI) language (1 mark)
- Hence forms enable web servers to provide powerful multi-media
front end to complex information. (1 mark)
Give credit for valid alternative answers.
(d) A ‘smart’ web application (Java applet) could compress
data before transmitting it to the server. What would be the advantages
and disadvantages in doing so? [4]
Advantage: smaller quantity of data transmitted;
good for the network (1 mark)
potentially faster (1 mark)
Disadvantage: compression using Java will be time-consuming (1 mark)
so not much time may be gained over all (1 mark)
Allow credit for other reasonable advantages and disadvantages.
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