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END TERM EXAMINATION
Exam Roll No. aquimenu
Paper Code: MCA207
THIRD SEMESTER [MCA] DECEMBER-2012
Time : 3 Hours
Subject: Data Communication &
Maximum Marks :60
Note: Attempt five questions including Q.no. 1 which is compulsory.
Select one question from each unit.
(a) What are two reasons for using layered protocols?
(b) What is the principal difference between connectionless and connection-oriented
(c) What is the main difference between TCP and UDP?
(d) List two advantages and two disadvantages of having international standards for
(e) Differentiate between static and dynamic channel allocation.
(f) When web pages are sent out, they are prefixed by MIME headers. Why?
g) The maximum payload of a TCP segment is 65,495 bytes. Why was such a strange
(h) If a binary signal is sent over a 3-kellz channel whose signal-to-noise ratio is 20dBP
What is the maximum achievable data rate?
i) What is the key difference between 2G and 3G mobile networks?
(j) Describe the characteristics of 10 Base 5 and 10 Base 2 ethernet cables (2x10-20)
(a) Explain the OSI reference model of computer networks with focus on the main
protocols at each layer.
(b) What is the essential difference between message switching and packet switching? (3)
(a) Encode the following data into digital signals:-
1 1001010. Use NRZ-L, NRZ-1, bipolar-AMI, Manchester and Differential Manchester
(b) Describe AM, FM and PM.
(a) A bit stream 10011101 is transmitted using the standard CRC method. The
generator polynomial x3+1 is used. Show the actual bits transmitted. Suppose the
third bit from the left is inverted during transmission. Show that this error is
detected at the receiver's end.
(b) Data link protocols almost always put the CRC in a trailor rather than in a header.
Explain the following data link protocols:-
(a) Why does congestion take place in computer networks? How is congestion control
done in Datagram Subnets?
(b) Describe the count-to-infinity problem.
(a) Differentiate between adaptive and nonadaptive routing algorithms with examples. (5)
(b) Differentiate between classful addressing and classless addressing Give examples. (5
(a) What are the characteristics of TCP? What services does TCP provide for data
(b) Why does TCP use the three way handshake and four way handshake?
(a) Differentiate between public key encryption and private key encryption
(b) What are the Digital Signatures? How are they used for data security?
(c) Discuss the types of DNS messages....
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