2008 Rajiv Gandhi Proudyogiki Vishwavidyalaya(Technical University) Computer M.C.A M.C.A.(Third Semester) EXAMINATION,June,2008 Question paper
MCA305(N) M.C.A.(Third Semester) EXAMINATION,June,2008 (New Course) COMPUTER NETWORKS [MCA305(N)] Time : Three Hours Maximum Marks : 100 Minimum Pass Marks :40
Note : Attempt all questions by attempting any two parts from each question. All questions carry equal marks.
1.(a) Differentiate between the following : (i) Frequency, Amplitude and Phase modulation. (ii) Pube amplitude and Pulse code modulation and Differential pulse code modulation. (iii) Time division, statistical time division and frequency division multiplexing. (b) Measurements of a slotted ALOHA channel with an infinite number of users show that 10 percent of the slots are idle : (i) What is the channel load G ? (ii) What is the throughput ? (iii)Is the channel underloaded or overloaded ? (c)(i) If a binary signal is sent over a 3 KHz channel whose signaltonoise ration is 20 dB, what is the maximum achievable data rate ? (ii) Consider building a CSMA/CD network running at 1 Gbps over a 1 km cable with no repeaters. THe signal speed in the cable is 200000 km/sec. What is the minimum frame size ? 2.(a) (i) A system using twodimensional even parity sends a block of 8 bytes. How many redundant bits are sent per block ? What is the ration of useful bits of total bits ? (ii) What is the remainder obtained by dividing x8 + x6 + x5 + 1 by the generator polynomial x5 + x3 + 1 using modulo2 arithmetic. (b) What do you mean by protocol correctness ? Construct a finite state diagram for a full duplex channel that never loses frames. (c) Write the complete procedure of GOBackN protocol. How does it differ from the selective repeat ? 3.(a) A 4Mbps token ring has tokenholding timer value of 10 m sec. What is the longest frame that can be sent on this ring ? Does the use of a wire centre have any influence on the performance of a token ring ? (b) Explain the working of FDDI protocol. A large FDDI ring has 100 stations and a token rotation time of 40 m sec. The token holding times is 10 m sec. What is the maximum achievable efficiency of the ring ? (c) Differentiate between the following : (i) Hubs, switches and routers (ii) Transparent and source routing bridge (iii) Repeaters and gateways
4.(a) Consider the subnet of the following network : Distance vector routing is used and the following vectors have just come into router C: from B(5,0,8,12,6,2) : from D: (16,12,6,0,9,10) and from E : (7,6,3,9,0,4). The measured delays to B,D and E are 6,3 and 5 respectively. What is C's new routing table ? Give both the outgoing line to use and the expected delay. (b) What do you mean by congestion in computer networks ? What are the various methods to control it ? Give an argument why the leaky bucket algorithm should allow just one packet per tick, independent of how large the packet is. (i) Convert the IP address whose hexadecimal representation is C 22 F1 582 to dotted decimal notation. (ii) Differentiate between the following : (1) TCP and UDP (2) Deadlocks and Livelocks
5.(a) Compare Cipher block chaining with Cipher feedback mode in terms of the number of encryption operations needed to transmit a large file. Which one is more efficient and by how much ? (b) Using the RSA public key cryptosystem with a = 1,b = 2 etc........ (i) if p = 7 and q = 11, list five legal values for d. (ii) Using p = 5, q=11 and d = 27, find e and encrypt 'abcdef' (c) Write brief notes on the following : (i) SNMP (ii) Virtual terminal protocol (iii) email
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