JNTU Previous Papers-B Tech -III-Year-Computer Networks-Aug/Sep 2008

JNTU III B.Tech II Semester

Supplimentary Examinations, Aug/Sep 2008



1. (a) Explain in detail ISO-OSI reference model.

(b) Write short notes on interface, service and protocol.


2. (a) The following data fragment occurs in the middle of a data stream for which the character-stuffing algorithm described in the text is used: DLE, STX, A, DLE, B, DLE, ETX. What is the output after stuffing?

(b) When bit stuffing is used, is it possible for the loss, insertion, or modification of a single bit to cause an error not detected by the checksum? If not, why not? If so, how? Does the checksum length play a role here?

(c) Data link protocols almost always put the CRC in a trailer, rather than in a header. Why?


3. (a) Explain the operation of source Routing Bridges.

(b) Compare and contrast Transparent and Source routing bridges.


4. (a) What is Broadcasting? With an example, explain about Reverse path forwarding

(b) With an example, explain multicast Routing Algorithm.


5. (a) Imagine that a two-way handshake rather than a three-way handshake were used to set up connections. In other words, the third message was not required. Are deadlocks now possible? Give an example or show that none exist.

(b) Datagram fragmentation and reassembly are handled by IP and are invisible to TCP. Does this mean that TCP does not have to worry about data arriving in the wrong order?


6. (a) Briefly discuss about connection less Internetworking.

(b) Explain firewalls, packet filter and a proxy in detail.


7. (a) What is Nagle’s algorithm? Explain the problem of silly window syndrome: suggest a solution to this problem.

(b) Briefly discuss about TCP timer management.


8. (a) What is the difference between message confidentiality and message integrity?

Can you have one without the other? Justify your answer.

(b) What is a key distribution centre? What is a certificate authority?

(c) In what way does a public key encrypted message digest provide a “better” digital signature than using public key encrypted message?

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