Tuesday, October 13, 2009


PART A( 10 * 2=20marks)

1.state the purpose of layering in networks?

2.At which level of OSI model does repesters,bridges,routers and gateways operate?

3.state the different between token ring and FDDI?

4.give the structure of encoder and decoder in error coorection

5.what is meant by IP spoofing?how can be router be used to prevent IP sppofing?

6.what kind of routing information do router exchange among themselves while running

distance vector algorithm? in particular,

briefly describe the format of routing information that is exchanged?

7.briefly describe 2 advantages of using packet switching for data transmission.

8.explain how tcp flow control works.

9.why id DNS nessary?state it's significance

10.what is security parameter index?

part B(5 *16=80marks)


(i)list four properties by which transmission media can differ(8 marks)

(ii)3 packet -switiching networks each contaion n nodes.the networks has a star


with a central switch, a ring respectively and a third is fully interconnected with a wire

from every node to every other node.

what are the best,averabge and worst case transmission paths in hops?(8 marks)



(i)describe the key elements of protocols and the standards.(8 marks)

(ii)explain in detail the data transmission in OSI reference model(8 marks)


(i)how does the 802.11 media access control protocol ensure that the receiver has a

greater chance to transmit the

acknowledgement frame before any other wireless stations grab the media?

does it always guarantee that the acknowledgment frame sent by the receiver will not

collide with another frame transmitted by another wireless station?(8 marks)

(ii)describe the collision avoidance mechanism used in 802.11 wireless LAN.

in particular,how such a mechanism solves the hidden terminal problem(8 marks)


b.describe 2 approaches by which packet loss is detected in a

Go back -N ARQ protocol and seletcive repear protocol.(16 marks)


(i)how is the looping problem solved by switches and by rou ters.

how do switches/routers handle link failure?(8 marks)

(ii)explain the IP addressing(8 marks)


b.(i)compare and contrast link state and distance vector algorithma(8 marks)

(ii)in the virtual circuit network service model,before a virtual circuit is set up, the soure

router needs to specify a path

(eg. shortest path)from the source to the destination

what additional information do we need to maintain in the

routing table to support this function?

write down the resulting routing table(8 marks)

14.aif UDp does not provide any service guarantees or reliable transfer,

why can't application directly access IP and do without it?

explain UDP in details(16 marks)


b.what is QOS in internetworking?state the techniques to improve QOS(16 marks)

15.a.what are the following acronym SMPT,FTP,WWW and HTTP stand for?

explain their uses and state the strengths and weakness of each of them(16 marks)


b.(i)explain the role of a DNS on computer networks,

including its involvment in the process of a user accessing a web page(8 mark)

(ii)describe about symmetric -key cryptography(8 marks)

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