Test Papers / Previous Question Papers of IGNOU CS09 Data Communications and Networking December 2005

ADCA / MCA (II Yr)
Term-End Examination

December, 2005

CS09 (S): Data Communications and Networking

Time: 3 hours
Maximum Marks: 75

1. (a) Explain the three general principles of congestion control. (3)

(b) List the various services offered by BISDN. (3)

(c) A binary signal is sent over a 3 kHz channel whose signal to noise ratio is 20 dB. What is the maximum achievable data rate ? (3)

(d) Discuss 802-3 frame format. Explain its various fields. (4)

(e) Dfferentiate datagrams and virtual circuits. (5)

(f) Make the timing diagram of Manchester coding of bit stream : 1010000111 and mention its advantages over other coding schemes. (3)

(g) Television channels are 6 MHz wide. How many bits/sec can be sent, if eight level digital signals are used ? Assume the channel is noiseless. (4)

(h) Explain the RSA algorithm used in cryptography. (5)

2. (a) Derive the throughput expression for Aloha and Slotted Aloha. (6)

(b) What is the advantage of differential pulse code modulation over pulse code modulation ? How is digital transmission done through PCM ? Discuss. (6)

(c) What is 'bit stuffing' ? Why is it used ? Illustrate through an example. (3)

3. (a) The data b(t) consists of the bit stream : 001010011010. Assume that the bit rate f_b is equal to the canier frequency f_o and sketch V_BPSK(t). (3)

(b) What is a Subnet ? How do you implement subnetting ? Explain through an example. (6)

(c) What is count infinity problem ? How does it happen in distance vector routing algorithm ? Illustrate through an example. (6)

4. (a) Make a comparison ol channel utilization vs. load for various random access protocols. llustrate through a diagram. (7)

(b) A 4 mbps token ring has a token holding time value of 10 m sec. What is the longest frame that can be sent on this ring ? (5)

(c) List three differences between IPv4 and IPv6. (3)

5. (a) Briefly describe the token bucket algorithm through a proper illustration. How is it different from leaky bucket algorithm ? (10)

(b) In a network that has a maximum TPDU size of 128 k bytes. a maxrmurn TPDU lifetime of 30 sec, and an 8 bit sequence number, what is the maximum data rate per connection ? (5)

6. Write short notes on any three: (15)

(a) SNMP protocol
(b) Electronic mail
(c) Network news transfer protocol
(d) Hyper text transfer protocol