Code: AC-12 / AT-10                             Subject: DATA COMMUNICATION & NETWORKS Flowchart: Alternate Process: JUNE 2007

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.       In a network with 25 computers, which topology would require the most extensive cabling ___________.

 

                   (A)  Mesh                                           (B)  Star

(C)    Bus                                             (D)  Ring

       

b.      Which of the following is an application layer service?  ___________

 

(A)    Remote log-in                               (B)  File transfer and access

(C)  Mail service                                  (D)  all of (A), (B) and (C)

            

             c.   If the frequency spectrum of a signal has a bandwidth of 500 Hz with the highest frequency at 600 Hz, what should be the sampling rate, according to Nyquist theorem?  ___________.

                                                                                                                                               

(A)     200 samples/sec                           (B)  500 samples/sec

(C)  1000 samples/sec                         (D)  1200 samples/sec

 

             d.   If the baud rate for a QAM signal is 1800 and the bit rate is 9000, how many bits are there per signal unit? ___________.

 

(A)    3                                                      (B) 4

(C)  5                                                 (D) 6

 

             e.   Transmission media are closest to the _____________________ layer.

                  

(A)  Physical                                        (B)  Network

(C)  Transport                                     (D)  Application

 

             f.    The ________ is a device that connects n inputs to m outputs.

 

(A)     crossbar                                       (B)  cross point

(C)  Modem                                        (D)  RAM

 

             g.   A timer is set when _____________  is (are) sent out.

 

(A)  A data frame                                (B)  An ACK

(C)  A NAK                                       (D)  All of (A), (B) and (C)

 

             h.   When a primary device asks a secondary device, if it has data to send, this is called __________ .

 

(A)    Polling                                          (B)  Selecting

(C)  Reserving                                     (D)  Backing off

 

             i.    In IPv6, the ______________ field in the base header restricts the lifetime of a datagram.

 

(A)   Version                                        (B) Priority

(C) Next-header                                  (D) Hop limit

 

             j.    A  __________  is a differentiated services traffic conditioner. 

 

(A)  Meter                                           (B)  Marker

(C)  Shaper                                         (D)  All of (A), (B) and (C)

 

 

Answer any FIVE Questions out of EIGHT Questions.

Each question carries 16 marks.

 

  Q.2     a.   Discuss the operating principles of OSI reference model with a diagram showing headers and trailers added as the block of user data moves.          (8)

 

             b.   A system has an N-layer protocol hierarchy. Applications generate message of length M bytes. At each of the layers, a h-byte header is added. What fraction of the network bandwidth is filled with header? (4)

 

c.       What do you mean by the term repeater? Why is an equalizer used in an analog repeater; explain in brief.                                                               (1+3)

                                                                

  Q.3     a.   What are the different transmission media used in computer communication? Compare with data rates.                                                           (2+6)

 

             b.   Find the CRC for a frame 1010001101 and G(x) =x5+x4+x2+1. Check if there are errors in the code word transmitted.                                          (6)                                                             

 

             c.   Define a circuit switched network with an example.                                             (2)

 

  Q.4     a.   What is time division switching? Discuss the time slot interchange (TSI) technique with a diagram.                                                              (2+5)

 

             b.   Explain the service model in a given layer for (i) connection oriented transfer service and (ii) connectionless transfer service.                                   (3+3)

 

             c.   What are the various approaches to share a transmission medium?                      (3)

   

  Q.5     a.   A 100 Km cable runs at the T-1 data rate. The propagation speed in the cable is 200,000 Km/sec. How many bits fit in the cable?                     (6)

 

             b.   Discuss token-ring protocol with suitable diagrams and IEEE 802.5 token and frame structure.                                                                  (4+6)

 

  Q.6     a.   How are routing algorithms classified? Explain shortest path algorithm with an example.                  (2+7)

 

             b.   Discuss the basic queueing model with arrival processes and service times.          (7)

 

  Q.7     a.   What are the different classes of IP addressing? Explain subnet addressing with an example.                                                                      (5+3)   

 

             b.   Instead of using 16 bits for the network part of class B address, 20 bits are used. How many class B networks would there be?                    (4)

 

             c.   What is multicast routing?                                                                                   (4)

            

  Q.8     a.   Discuss PNNI signalling with an example.                                                           (8)

 

             b.   What is RSVP? Explain it’s architecture with a block schematic.                     (1+7)

 

  Q.9           Write explanatory notes on:-

                   (i) ATM service categories

                   (ii) Network Management

                   (iii) MPLS                                                                                                 (5+5+6)