Rajiv Gandhi Proudyogiki Vishwavidyalaya 2008-3rd Sem M.C.A Computer Aplications .(ester) ,e, - exam paper

MCA-305(N)
M.C.A.(Third Semester) EXAMINATION,June,2008
(New Course)
COMPUTER NETWORKS
[MCA-305(N)]
Time : 3 Hours
Maximum Marks : 100
Minimum Pass Marks :40

Note : Attempt all ques. by attempting any 2 parts from every ques.. All ques.
carry equal marks.

1.(a) Differentiate ranging from the subsequent :
(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 three KHz channel whose signal-to-noise ration is 20 dB,
what is the maximum achievable data rate ?
(ii) Consider building a CSMA/CD network running at one Gbps over a one 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 two-dimensional even parity sends a block of eight bytes. How many redundant
bits are sent per block ? What is the ration of useful bits of total bits ?
(ii) What is the remainder found by dividing x8 + x6 + x5 + one by the generator polynomial
x5 + x3 + one using modulo-2 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 GO-Back-N protocol. How does it differ from the selective-
repeat ?
3.(a) A 4-Mbps token ring has token-holding 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) discuss 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 ranging from the subsequent :
(i) Hubs, switches and routers
(ii) Transparent and source routing bridge
(iii) Repeaters and gateways

4.(a) Consider the subnet of the subsequent network :

Distance vector routing is used and the subsequent 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 five respectively. What is C's new routing table ? provide both the outgoing
line to use and the expected delay.
(b) What do you mean by congestion in computer networks ? elaborate the different methods to control
it ? provide an argument why the leaky bucket algorithm should allow just 1 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 ranging from the subsequent :
(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 1 is more efficient and by how much ?
(b) Using the RSA public key cryptosystem with a = 1,b = two etc........
(i) if p = seven and q = 11, list 5 legal values for d.
(ii) Using p = 5, q=11 and d = 27, obtain e and encrypt 'abcdef'
(c) Write brief notes on the subsequent :
(i) SNMP
(ii) Virtual terminal protocol
(iii) e-mail

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Earning:   Approval pending.