APPLICATIONS
Term-End Examination
December, 2006
CS-68: COMPUTER NETWORKS
Time : 3 hours Maximum Marks : 75
Note : Question number 1 is compulsory. Answer any three questions from the rest.
1. (a) List and describe five examples of WAN applications you have seen.(5)
(b) Explain the functioning of 7 layers of OSI model.What is the necessity of using 7 layers concept in OSI model ? (10)
(c) How is Selective Repeat better than Go Back N ? (3)
(d) Differentiate between the following : (4)
(i) Bit rate and Baud rate
(ii) IEEE 802.4 and IEEE 802.5
(e) Enlist two factors that cause congestion in the Subnet. (2)
(f) Describe basic types of ISDN services. (2)
(g) Compare and contrast Packet and Cell switching. (4)
2. (a) Explain how Slotted Aloha improves the performance of system over Pure Aloha. (3)
(b) Explain the use of the following devices in computer networks : (4)
(i) Hub
(ii) Bridges
(iii) Switches
(iv) Gateways
(c) Let a system use 9600 bps channel for sending call setup request to a base station. Suppose that packets are 120 bits long, that the time-out is 20 ms. What is maximum throughput possible with Aloha and with Slotted Aloha ? (8)
3. (a) Explain the function of Modem with the help of a suitable diagram.(4)
(b) Differentiate between Guided and Unguided transmission media. Give one example of each. Also
describe any one guided transmission media in detail. 6
(c) Explain Sliding Window Protocol with the help of an appropriate diagram.(5)
4. (a) Explain the functioning of spanning tree bridges. (4)
(b) Define multiplexing. Discuss the need for multiplexing in networked system. (4)
(c) Describe the format of TCP Header. (7)