Code: D-21 / DC-11                               Subject: DATA COMMUNICATION & NETWORKS

Time: 3 Hours                                                 June 2006                                                     Max. Marks: 100

NOTE: There are 9 Questions in all.

· Question 1 is compulsory and carries 20 marks. Answer to Q. 1. must be written in the space provided for it in the answer book supplied and nowhere else.

· Out of the remaining EIGHT Questions answer any FIVE Questions. Each question carries 16 marks.

· Any required data not explicitly given, may be suitably assumed and stated.

Q.1       Choose the correct or best alternative in the following:                                         (2x10)

a. ITU–T’s X.200 standard describes   

(A)  TCP/IP model                              (B)  ATM Networks

(C)   OSI model                                  (D)  ISDN Networks

b. If s(t) = s(t+T) where  then s(t) is

(A) aperiodic signal.                            (B)  periodic signal.

(C)  impulse.                                        (D)  discrete signal.

             c.   A channel bandwidth of 8 MHz results in a data rate of

(A) 4 Mbps.                                       (B)  2 Mbps.

(C)  8 Mbps.                                       (D)  16 Mbps.

             d.   Delay distortion in a signal occurs due to its

(A)  amplitude                                    (B)  phase

(C)  frequency                                    (D)  velocity of propagation           

             e.   An amplifier has a 30 dB voltage gain.  Its  is

(A) 30                                                (B)  15

(C)  31.622                                         (D)  30.55

             f.    Multilevel signalling of data encoding helps in improving

(A) bandwidth efficiency                     (B)  signal-to-noise ratio

(C)  modulation efficiency                    (D)  recovered signal quality

             g.   Datagram and virtual circuits are the two methods to design _______ networks.

(A) space division                               (B)  packet switched

(C)  message switched                         (D)  circuit switched

h.   LLC protocol is for

(A) WAN’s                                        (B) MAN’s

(C) Internets                                        (D) LAN’s

             i.    Multicasting is supported by _________ IP address

(A) Class A                                        (B) Class B

(C) Class D                                         (D) Class C

             j.    UDP is a ___________ protocol

(A)  connection oriented                      (B)  connection less

(C)  connection rejection                      (D)  connection abortion

Answer any FIVE Questions out of EIGHT Questions.

Each question carries 16 marks.

Q.2     a.   With reference to the subnetworks, describe the working of TCP and IP protocols.            (8)

             b.   What are the salient features of Mobile IP?                                                         (4)

             c.   In a BPSK system, the  is 8.4 dB, with a BER , noise temperature = and data rate 2400 bps.  Calculate the received signal level in watts.                                                        (4)

Q.3     a.   What is stop and wait flow control protocol.                                                       (8)

             b.   Compute the bandwidth efficiency for ASK, FSK, PSK and QPSK systems for a bit error rate of on a channel with an SNR of 12 dB.  Given =14.2 dB for ASK and FSK and 11.2 dB for PSK.                                                           (8)

Q.4     a.   With neat block diagrams of transmitter and receiver, describe a synchronous TDM system.                                                                      (6)

b.   Write a brief note on Token ring.                                                                        (4)

             c.   Describe ADSL and XDSL technologies.                                                           (6)

Q.5     a.   Describe the salient features of Frame Relay protocol.                                        (6)

     b.   Discuss any one-error detection/correction method used at data link layer.          (4)

             c.   What are the real time and non real time services offered by ATM networks?                     (6)

  Q.6     a. What are the various network topologies? List the factors that affect the choice of a topology and transmission medium in a LAN.            (8)

             b.   With a neat diagram describe the IEEE 802.3 frame structure. Is it same as Ethernet frame structure? Explain your answer.                                        (8)

Q.7     a.   Discuss the salient features of IPv4 addressing.                                                   (6)

b.   Compare and contrast IPV4 and IPv6.                                                               (4)

             c.   What is multicasting?  What are its applications?                                                 (6)

Q.8     a.   Describe the TCP header format.                                                                     (10)

             b.   Briefly explain the following TCP mechanisms:

(i)    Connection establishment.             (ii)  Data transfer.

                   (iii)  Connection termination.                                                                               (6)

Q.9           Write short notes on ANY TWO of the following:

(i) SMTP

(ii) Circuit switching

(iii) WWW

(iv) Different transmission media used in computer communication.

(v) Routing protocols.                                                                 (8+8)