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(a) Explain the term routing. What essential
data structure is present in every
router to make routing possible? [2]
- Routing is the process of finding path
from a source to a destination
across the network (1 mark)
- The basis for all the routing techniques is the routing table, which
is
present in every router to tell where to forward the incoming packet.
(1 mark)
Give credit for valid alternative answers.
(b) Assuming that all routers and hosts
are working properly and that all software in both is free of all
errors, is there any chance that a packet will be delivered to the
wrong destination? Explain your answer. [2]
- Yes
- A large noise burst could garble a packet (1 mark), leaving it
sufficiently well-formed for it still to be delivered, but to a wrong
destination (1 mark).
Do not award a mark simply for `yes’ without any attempt at explanation.
(c) Give three examples of protocol
parameters that might be negotiated when a network connection is set-up.
[3]
-Window size for flow control
-Maximum packet Size for congestion control
-Timer values for acknowledgement (1 mark each)
(d) Border Gateway Protocol version
4 and Open Shortest Path First are the
examples of hierarchical routing protocols used on the Internet. Identify
the
type of hierarchical routing they represent and their purpose. [4]
Border Gateway Protocol version 4:
- Is an example of Exterior gateway protocol (1 mark)
- Provides routing between Autonomous systems or domains or
Zones(1 mark)
Open Shortest Path First:
- Is an example of Interior gateway protocol (1 mark)
- Provides routing within the Autonomous system or domain or Zone
(1 mark)
Give credit for valid alternative answers.
(e) Explain why it is necessary to use
both logical and physical addresses in
networks. [4]
Logical Address:
- Is a temporary one and changes when the machine location changes.
(1 mark)
- Provided by Network Information Centre to identify the machine
uniquely across networks (1 mark)
Physical Address:
- Is a permanent one and changes only when the NIC card changes. (1
mark)
- Provided by the manufacture of NIC card (1 mark)
Allow full credit for valid alternative answers.
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