Andhra University 2003 M.Sc Computer Science Data Communications - Question Paper

M.Sc. DEGREE exam - Computer Science
First Year 1st Semester

Data Communications - November 2003


Time: 3 hours
Maximum: 75 marks

First ques. is compulsory.
ans any 4 from the remaining.
All ques. carry equal marks.
ans all parts of any ques. at 1 place.

1. a. define public switched telephone network (PSTN)

b. With the aid of sketch, discuss the effect on a transmitted binary signal of the attenuation.

c. Distinguish ranging from roll call polling and hub polling.

d. discuss the difference ranging from connectionless and connection-oriented transmission.

e. describe logical link control.

2. a. Identify various applications of computer communication networks. discuss how communication networks are useful in those applications.

b. discuss lome standard protocol suites that are based on the ISO protocols.

3. define different kinds of physical layer interface standards.

4. Deduce the maximum theoretical info rates associated with the subsequent transmission channels:-

a. Telex network with a bandwidth of 500Hz and a signal to noise ratio of 5dB.

b. Switched telephone network with a band width of 3100 Hz and a signal to noise ratio of 20dB.

5. a. define how frame synchronization is achieved with asynchronous and character oriented synchronous transmission.

b. What is Dynamic Huaffman coding? discuss how it is useful in data compression.

6. discuss the principle of operation of a CRC fault detection method. By means of an example, show how:-

a. The fault detection bits are generated

b. The received frame is checked for transmission errors use the generator polynomial: x4+x3+1

7. discuss the operation of the Idle RQ fault control schemes and produce frame sequence diagrams to illustrate these operations.

8. Assuming the HDLC protocol, distinguish ranging from the NRM and ABM modes of working. Sketch typical frame sequences to show how a link is 1st setup and then cleared for every mode. Clearly show the various frame kinds used and the use of the address and poll/final bit in every frame.

Earning:   Approval pending.