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

ADCA / MCA (II Yr)

1. (a) An analog signal is limited to 4 kHz. It is converted to a PCM signal using 8 bit/sample. What is the bit rate on the transmission line? (3)

(b) Make a timing diagram and show the differences between manchester encoding and differential manchester encoding for the bit stream 10001011011. (4)

(c) Calculate the number of networks that can exist in Class A, B and C IP addresses. Also, calculate the number of hosts a network in each class can have. (6)

(d) What happens in a token bus network if a station accepts the token and then crashes immediately? How does protocol handle this situation? (6)

(e) Answer the following questions with respect to a TCP header: (6)
(i) Why is the TCP header length required? Explain this.
(ii) What is the need of a variable size sliding window?

(f) What is a subnet? How is subnetting implemented? Explain this with the help of an example. (5)

2. (a) Explairl the TCP connection establishment procedures both in the normal case and in the call-collision case, with the help of a diagram each. (5)

(b) Explain two important reasons for having a minimum frame length in CSMA/CD. Explain this diagrammatically. (5)

(c) Derive the throughput expressions for ALOHA and Slotted ALOHA. (5)

3. (a) Sketch a Network Address Translation (NAT) Box, and explain its operations. (5)

(b) Why is there a need for compression? Differentiate between JPEG and MPEG standards. (4)

(c) Give at least three functions of a modem. (3)

(d) How does UDP handle flow control, error control or retransmission upon receipt of a bad segment? (5)

4. (a) Explain the operation of an FDDI token ring, with the help of a diagram. Also, list the two key differences between FDDI and IEEE 802.5. (7)

(b) Explain the functioning of the HDLC protocol for the following: (8)
(i) Busy condition
(ii) Error recovery using REJ command
(iii) Two-way data exchange
(iv) Link setup and disconnection

5. Write any three differences between the following pairs. (15)
(i) Circuit switching and Packet switching
(ii) Connection oriented and Connectionless services
(iii) ARP and RARP
(iv) Upward multiplexing and Downward multiplexing
(v) X.25 and Frame relay