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Posted By: jothi vignesh Member Level: Gold Posted Date: 06 Jul 2008
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2006 Anna University B.E DATA COMMUNICATION & COMPUTER NETWORKS Question paper
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Code: C-12 Subject: DATA COMMUNICATION & COMPUTER NETWORKS
Time: 3 Hours Max. Marks: 100
NOTE: There are 11 Questions in all.
Question 1 is compulsory and carries 16 marks. Answer to Q. 1. must be written in the space provided for it in the answer book supplied and nowhere else.
Answer any THREE Questions each from Part I and Part II. Each of these questions carries 14 marks.
Any required data not explicitly given, may be suitably assumed and stated
Q.1 Choose the correct or best alternative in the following: (2x8)
a. How many OSI layers are covered in the X.25 standard?
(A) Two (B) Three
(C) Seven (D) Six
b. The transmission signal coding method of T1 carrier is called
(A) Bipolar. (B) NRZ.
(C) Manchester. (D) Binary.
c. The area of coverage of a satellite radio beam is known as
(A) Footprint. (B) Circular polarization.
(C) Beam width. (D) Identity.
d. Error detection at a data link level is achieved by
(A) Bit stuffing. (B) Cyclic redundancy codes.
(C) Hamming Code. (D) Equalization.
e. Which of the following TCP/IP protocol allows an application program on one machine to send a datagram to an application program on another?
(A) RARP (B) ARP
(C) TCP (D) FTP
f. Which of the following communications lines is best suited to interactive processing applications?
(A) NarrowBand channels (B) Simplex lines
(C) Full-duplex lines (D) Mixed band channels
g. ARQ stands for
(A) Automatic Repeat Quantization
(B) Automatic Repeat Request
(C) Automatic Retransmission Request
(D) Acknowledge Repeat Request
h. A distributed data processing configuration in which all activities must pass through a centrally located computer is called a
(A) Ring network. (B) Star network.
(C) Tree network. (D) Mesh network.
PART I
Answer any THREE Questions. Each question carries 14 marks.
Q.2 a. What is the difference between a confirmed service and an unconfirmed service? (6)
b. For each of the following, tell whether it might be a confirmed service, an unconfirmed service, both, or neither. (3)
(i) Connection establishment
(ii) Data transmission
(iii) Connection release
c. What does "negotiation" mean when discussing network protocols? Give an example of it. (5)
Q.3 a. Derive the expression for throughput of slotted ALOHA. Why is slotted ALOHA performance better than pure ALOHA? (4)
b. With the help of block diagram explain working of PCM system (6)
c. Compare FM and AM. (4)
Q.4 a. With the help of a block diagram and necessary expressions explain the working of QPSK system. (6)
b. Derive the expression for probability of error in BPSK system. (5)
c. Compare ASK and FSK system. (3)
Q.5 a. With the help of block diagram explain the working of T1 carrier, 30 channel multiplexing system. (6)
b. How does a single bit error differ from a burst error? (3)
c. Explain RS232C interface. (5)
Q.6 a. One way of detecting error is to transmit data as a block of n rows of k bits per row and adding parity bits to each row and each column. Will this scheme be able to detect all single bit errors? Double bit errors? Triple bit errors? Justify your answer. (5)
b. In a token ring the sender removes the frame. What modifications to the
system would be needed to have the receiver remove the frame instead and
what would be the consequences? (4)
c. Explain circuit switching. Compare it with packet switching. (5)
PART II
Answer any THREE Questions. Each question carries 14 marks.
Q.7 a. Explain how the sender and receiver communicate using OSI model? (5)
b. Why is a virtual terminal protocol needed? What kind of applications are likely to use it. (4)
c. What are public key data encryption algorithms? (5)
Q.8 a. What is congestion control? Explain how the following policies help in congestion control (8)
(i) Pre allocation of buffers.
(ii) Packet discarding.
(iii) Flow control.
b. Describe and compare the following routing algorithms (6)
(i) Shortest path routing.
(ii) Flooding.
Q.9 a. Differentiate between LAN, MAN and WAN. (5)
b. What are the IEEE 802.3, 802.4 and 802.5 standards ? Explain the following aspects for an Ethernet system.
(i) Access protocol
(ii) Topology and media
(iii) Response time Q.10 a. Describe the working procedure for the following data link layer protocols.
(i) Stop and wait
(ii) Selective Repeat
(iii) Go Back n (6)
b. Find the performance expression for any one of them and draw the graph
showing the effect of packet size on performance. (8)
Q.11 a. Explain the working principles of e-mail. Compare the mailing protocols -
SMTP and MIME. (7)
b. Explain structure and protocols of ISDN. (7)
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