Computer Communication Networks - May 2015

Electronics Engineering (Semester 7)

TOTAL MARKS: 80
TOTAL TIME: 3 HOURS (1) Question 1 is compulsory.
(2) Attempt any three from the remaining questions.
(3) Assume data if required.
(4) Figures to the right indicate full marks.

Answer the following briefly:

1 (a) Distinguish between Logical Addressing. Physical Addressing and Port addressing. Give an example for each type. Also name the layer at which each of them operate. (5 marks)

1 (b) What are transmission impairments? Explain each briefly. Which transmission medium is better as a communication channel and why? (5 marks)

1 (c) Explain the working of TSI Switch. (5 marks)

1 (d) Compare TCP and UDP. (5 marks)

1 (e) What is meant by data transparency? How s it implemented in HDLC? Give an example. (5 marks)

2 (a) Explain the need for layered architecture. Explain TCP/IP, mentioning the functions of each layer. Also mention the Protocols for each layer. (10 marks)

2 (b) Explain the functions of each of these interconnecting devices: Hubs, Repeaters, Switches, Bridges, Routers and Gateways. (10 marks)

3 (a) Consider that Primary station A, is intending to set uo communication link in normal response mode with two secondary Stations, B and C. Which frames are exchanged between Primary and Secondary stations for the following situations? Show with frame flow diagram, the following sequence:
i) Primary A wants to set up a normal response mode with secondary stations B and C and both stations B,C send an positive Acknowledgement frame to A.
ii) Station A wants to know whether B and C have some data to send to Primary and in response B sends 2 data frames, while C indicates that it has no data to send.
iii) Primary station sends acknowledgement to B for the data received.
iv) Primary sends 'Select' command to Band 'C' to check whether any stations is ready to receive the data. B indicates that it is Busy and not ready, while C indicates it is ready to receive the data.
v) Primary sends 3 data frames to C and C sends positive acknowledgement to A. (10 marks)

3 (b) What is meant by error control? Show, with flow diagrams, how error control is implemented in each ARQ technique for the following situations:
i) lost or damaged frames,
ii) delayed acknowledgements and
iii) lost or damaged acknowledgements. (10 marks)

4 (a) What is meant by 'blocking' in circuit switching networks? Bring out the advantages of multi stage space division switching over single stage switching.
i) Sketch a 3-stage Space division switch wit N=15, group size of n=5, K=2, what is the condition required to make it non-blocking?
ii) For the same specifications sketch three-stage TST switch using TSI modules. (10 marks)

4 (b) Explain ADSL with respect to channel configuration and modulation technique. Compare the different DSL technologies. (10 marks)

5 (a) Explain LAN Protocol architecture with reference to IEEE 802. Sketch the frame format of MAC Sub-layer and explain the functions of each field. (10 marks)

5 (b) What is the difference between Congestion Control and Flow control? Explain congestion control methods. (10 marks)

6 (a) Compare Circuits switching, Datagram switching and Virtual circuit Packet switching. (10 marks)

6 (b) Apply Dijkstra's algorithm to given network to find the least cost path from node 4 to all other nodes (state the steps in the algorithm). (10 marks)

Write short notes on (any four):

7 (a) ISDN (5 marks)

7 (b) Piggybacking with an example (5 marks)

7 (c) Berkeley API. (5 marks)

7 (d) SONET / SDH (5 marks)

7 (e) LAN topologies. (5 marks)