R5

Code No: R5310505

III B.Tech I Semester(R05) Supplementary Examinations, November 2010 COMPUTER NETWORKS (Common to Computer Science & Engineering and Information Technology) Time: 3 hours Max Marks: 80 Answer any FIVE Questions All Questions carry equal marks ????? 1. Differentiate between the following: (a) WAN and Internet (b) Connection oriented service and Connection less service (c) OSI Vs TCP/IP.

[5+5+6]

2. (a) Television channels are 6MHz wide. How many bits/sec can be sent if four level digital signals are used? Assume a noiseless channel (b) How does a virtual circuit differ from a physical circuit? What advantages would a virtual circuit provide? [8+8] 3. Explain in detail the two data link protocols widely used in the Internet?

[16]

4. (a) Discuss about the file key assumptions in case of dynamic channel allocation in LANs and WANs? (b) Discuss in detail the working of token bus?

[8+8]

5. What are the services provided by Network layer to Transport layer. Explain.

[16]

6. (a) Explain how fragmentation is done and how fragments are reassembled. (b) What are the advantages of hierarchical addressing over flat addressing? (c) What is Three bears problem? Explain it.

[6+4+6]

7. (a) Suggest modifications to TCP to make it suitable for short data transfers. (b) UDP provides only connectionless service. For applications which use UDP how you provide reliability. [10+6] 8. (a) What is cipher block chaining? Why it is used. What are its advantages & disadvantages? (b) What is cipher feedback mode? Why it is used? ?????

[10+6]