Test Papers / Previous Question Papers of IGNOU CS09 Data Communications and Networking June 2006

1. (a) Explain the utility of an FDDI dual counter rotating ring. Is the FDDI solution the best among all other similar technologies? Justify your answer. (4)

(b) What is the importance of a router and a bridge for applications in a network? Can bridging be used along with routers? Explain this. (4)

(c) An analog signal is limited to 8 kHz. It is converted to a PCM signal using 12 bits/sample. What is the bit rate on the transmission line? (3)

(d) Make a timing diagram and show the differences between Manchester encoding and Differential Manchester encoding for the bit stream: 10100010111 (4)

(e) What is the 'count to infinity' problem? Why does it happen in the distance vector routing algorithm? Illustrate this through an example. (5)

(f) Explain the significance of the following two fields of the IPv4 Header: (6)
(i) Fragment offset
(ii) TTL

(g) What is the difference between asynchronous and synchronous transmission? In asynchronous transmission how does a receiving device determine the presence of a start bit? (4)

2. (a) Explain, using diagrams, how the processes of formation and pruning of a spanning tree take place in multicast routing. (5)

(b) What are the problems with a 2-way handshake in a connection establishment and a connection termination? How does a 3-way handshake resolve them? (5)

(c) Why is the size of an ATM cell 53 bytes? How does AAL5 work? (5)

3. (a) Explain how the Go Back N sliding window protocol maintains the flow control, with the help of a diagram. (5)

(b) What are the general principles of congestion control? Explain how the token bucket algorithm provides the congestion control. (6)

(c) Write any three advantages of a coaxial cable to be used in LAN implementation. Also list the categories of UTP. (4)

4. (a) Give the shortest path routing algorithm, as proposed by Djikstra. Explain it, using an example. (8)

(b) What is CSMA/CD? Write any three differences between CSMA/CD and token passing access methods. Also, explain how collision can be avoided on a CSMA/CD network. (7)

5. Write any three differences between the following: (15)
(i) PPP frame format and HDLC frame format
(ii) AAL1 and AAL2 protocols
(iii) Virtual Circuit Subnet and Datagram Subnet
(iv) Pulse code modulation and Delta modulation
(v) 1-persistent CSMA and Non-persistent CSMA