Anna University Chennai 2006 B.E DATA COMMUNICATION

Code: C-12 Subject: DATA COMMUNICATION & COMPUTER NETWORKS
Time: three Hours Max. Marks: 100
NOTE: There are 11 ques. in all.
ques. one is compulsory and carries 16 marks. ans to Q. 1. must be written in the space given for it in the ans book supplied and nowhere else.
ans any 3 ques. every from Part I and Part II. every of these ques. carries 14 marks.
Any needed data not explicitly given, may be suitably presumed and said
Q.1 Choose the accurate or best option in the following: (2x8)

a. How many OSI layers are covered in the X.25 standard?
(A) 2 (B) Three
(C) 7 (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 subsequent TCP/IP protocol allows an application program on 1 machine to send a datagram to an application program on another?
(A) RARP (B) ARP
(C) TCP (D) FTP

f. Which of the subsequent 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
ans any 3 ques.. every ques. carries 14 marks.
Q.2 a. What is the difference ranging from a confirmed service and an unconfirmed service? (6)
b. For every 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? provide 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 discuss working of PCM system (6)
c. Compare FM and AM. (4)

Q.4 a. With the help of a block diagram and necessary expressions discuss the working of QPSK system. (6)
b. Derive the expression for probability of fault in BPSK system. (5)
c. Compare ASK and FSK system. (3)

Q.5 a. With the help of block diagram discuss the working of T1 carrier, 30 channel multiplexing system. (6)
b. How does a single bit fault differ from a burst error? (3)
c. Explain RS232C interface. (5)
Q.6 a. One way of detecting fault is to transmit data as a block of n rows of k bits per row and adding parity bits to every row and every column. Will this scheme be able to detect all single bit errors? Double bit errors? Triple bit errors? Justify your ans. (5)

b. In a token ring the sender removes the frame. What changes 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
ans any 3 ques.. every ques. 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 type of applications are likely to use it. (4)

c. What are public key data encryption algorithms? (5)

Q.8 a. What is congestion control? discuss how the subsequent policies help in congestion control (8)

(i) Pre allocation of buffers.
(ii) Packet discarding.
(iii) Flow control.
b. Describe and compare the subsequent routing algorithms (6)

(i) Shortest path routing.
(ii) Flooding.
Q.9 a. Differentiate ranging from LAN, MAN and WAN. (5)

b. What are the IEEE 802.3, 802.4 and 802.5 standards ? discuss the subsequent aspects for an Ethernet system.
(i) Access protocol
(ii) Topology and media
(iii) Response time Q.10 a. Describe the working procedure for the subsequent data link layer protocols.
(i) Stop and wait
(ii) Selective Repeat
(iii) Go Back n (6)

b. Find the performance expression for any 1 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)

Earning:   Approval pending.