Code: AC12 / AT10                               Subject: DATA COMMUNICATION & NETWORKS

Time: 3 Hours                                                                                                     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. Which topology required a central controller or hub?

(A)  Mesh                                           (B)  Star

(C)   Bus                                             (D)  Ring

b. The physical layer is concerned with the transmission of __________ over the physical medium.

(A) Programs                                     (B)  Dialogs

(C)  Protocols                                     (D)  Bits

             c.   Unipolar, bipolar and polar encoding are types of ___________ encoding.

(A) Line                                             (B)  Block

(C)  NRZ                                            (D)  Manchester

             d.   Transmission media are usually categorized as  ___________.

(A) Fixed or unfixed                           (B) Guided or unguided

(C) Deterministic or Indeterministic      (D)  Metallic or non-metallic

             e.   How many crosspoints are needed in a single-state switch with 40 inputs and 50 outputs?

(B) 40                                                (B)  50

(C)  90                                                (D)  2000

             f.    In a SONET system, ________ can remove signals from a path.

(A) An STS multiplier                         (B)  A regenerator

(C)  An add/drop multiplexer               (D)  A repeater

             g.   The HDLC _____________ field defines the beginning and end of a frame.

(A) Flag                                             (B)  Address

(C)  Control                                        (D)  FCS

h.   __________  is the access protocol used by IEEE 802.3.

(A) CSMA                                         (B)  CSMA/CD

(C)  CSMA/CA                                  (D)  Token Ring

             i.    An FHSS wireless LAN has a spread spectrum of 1 GHz. The bandwidth of the original signal is 250 MHz and there are ____________ hops per cycle.

(A) 1                                                  (B) 2

(C) 3                                                   (D) 4

             j.    UDP and TCP are both __________  layer protocols. 

(A)  Physical                                        (B)  Data Link

(C)  Network                                      (D)  Transport

Answer any FIVE Questions out of EIGHT Questions.

Each question carries 16 marks.

Q.2     a.   Describe the TCP/IP reference model; Discuss the function of each layer.           (8)

             b.   How are communication channels characterized? Explain with suitable figures.                    (8)

Q.3     a.   Assuming that a PSTN has a bandwidth of 3000Hz and a typical S/N ratio of 20dB, find the maximum theoretical information rate that can be achieved.                                                                (5)

             b.   Explain with suitable diagrams binary phase modulation.                                      (6)

c.   Discuss the basic principles of WDM with suitable illustrations.                           (5)

Q.4     a.   Discuss the operation of a signalling network; How is an intelligent network superior to a conventional signaling network?                               (4+2)

b.   With a block schematic, explain the operation of a cellular network.                    (6)

             c.   A channel is operating at 4800 bps and the propagation delay is 20msec. What should be the minimum frame size for stop-and-wait flow control to get 50% link utilization efficiency?                             (4)

Q.5     a.   What are the basic elements of ARQ protocol? Explain with a diagram.              (6)

     b.   What is the need for framing? Discuss the frame structure of PPP frame.             (6)

c.   In a CSMA/CD network at 1 Gbps over 1 Km with no repeaters, find the minimum frame size. Assume the signal speed in the cable as 200 meters per microsecond.                                                   (4)

  Q.6     a. Explain carrier sense multiple access with collision detection with relevant diagrams.            (8)

             b.   What is FDDI? Discuss the working of a FDDI network with the help of frame structure.                (1+7)

Q.7     a.   Explain with an example the principle of Bellman-Ford algorithm.                        (7)

b.   Find the shortest path from the node A to D using shortest path algorithm for the network shown.                                                              (5)

c. Explain the basic structure of TCP/IP protocol suite.                                          (4)

Q.8     a.   How is subnet mask useful in IP addressing? Explain with an example.                (5)

             b.   Discuss the usefulness of extension headers in IPv6.                                            (5)

c.   Explain routing for mobile hosts.                                                                         (6)

Q.9           Write explanatory notes on:-               

(i) PNNI Routing

                   (ii) RSVP architecture

                   (iii) Little’s Formula                                                                                   (6+6+4)