West Bengal Institute of Technology (WBIT) 2009-6th Sem B.Tech Electronics and Communications Engineering Electronics & Comm ( - ) Computer Communication and Networking - Question Paper

i .

tv) For noiseless channel, the Nyqulst bit rate formula defines the

a)    practical maximum bit rate

b)    theoretical maximum bit rate

c)    practical minimum bit rate.    1 ............1

v)    In asynchronous serial transmission, we send..... ,

a)    one start bit 0 and one or more stop bit 1 at the end of each byte

b)    one start bit 1 and one or more stop bit 0 at the end of each byte

c)    one start bit 1 and one or more stop bit 1 at the end of each byte.

vi)    In synchronous TDM, the data rate of link is

a)    n times faster ( where n denotes no. of connection of the link )

b)    n times slower

c)    2 times faster.

vii)    The physical layer devices are

a)    Hub and Switch

b)    Hub and Multiplexer

c)    ATM switch and MUX.

viii)    ADSL modem ( broadband modem) data rates is higher because it uses

a)    256 channel each of 4*312 kHz

b)    250 channel each bf 5-312 kHz

c)    25 channel each of 4*312 kHz. fist) Vulnerable time for C8MA-protocol is

a)    twice of average frame transmission time

b)    average frame transmission time

c)    propagation time.

x) The example of controlled access protocol is '

a)    Aloha protocol

b)    Polling

c)    CSMA/CD.

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xi)    A network has IP address 129.34.234.12,

a)    the address is class A address

b)    the address Is class B address

c)    the address is class C address.    -

xii)    In Ethernet MAC frame consists of destination address 4A.3B.45.78.C5.67 which

,    is    ' "     .

a)    broadcast address

b)    unicast address

c)    multicast address.    -

xiii)    The layer which responsible for encryption technique in data communication is

a)    network layer

b)    presentation layer

c)    data link layei.    *--

xlv) Advantage of layering includes

a) multi*vender , integration . b) data hiding and encapsulation

c) easy testing    d) all of these.    I-

GROUP-B (Short Answer Type Questions )

Answer any three of the following questions.    3x5 = 15

2.    Explain the difference between point-to-point and multi-point connection.

3.    Explain the link state routing.

4.    Derive the expression of the efficiency of pure ALOHA. Compare it with slotted ALOHA.

5.    Explain CDMA technique with a suitable example.

6.    Briefly explain leaky bucket algorithm for congestion control.

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CS/B.TECH(ECE-NKW)/8EM-6/BC-602/09    6

'    GROUP-C

(Long Answer Type Questions)

Answer any three of the following questions.    3x15 = 45

7.    a) What are the differences between packet switching and circuit switching ?

b)    Explain with the diagram, how the lost frame, delayed and lost acknowledgements are handled in Go-Back - N ARQ.

c)    What do you understand by data privacy ? How can authentication, integrity and non-repudiation be implemented by the digital signature technique ? 4 + 5 + 6

8.    a) tf the received string is 110110111011, then calculate the actual data string. The

data Is encoded by 1 bit error correcting code ( Hamming code ).

b) Briefly explain the selective flooding routing algorithm. Why does It differ from flooding routing algorithm ? Why does it differ from flooding technique ?

, c) Describe 802.3 header format. Why padding is required ?

d)    What are the differences between TCP & UDP ?    3 + 5 +3+ 4

9.    Explain CRC code with an example. Derive the poll scan time for serial and hub polling. What is the difference between bit oriented and byte oriented protocol ?    9 + 4 + 2

10.    a) What is the default mask and broadcast address for class B ? Specify the private

IP range for class A address.    '

b)    Why is dynamic routing preferred over static routing algorithm in a network, which changes continuously ?

c)    What is digital signature ? Explain in brief RSA algorithm.

' . *>

d)    Describe any one guided and one unguided media with diagram. 2 + 2 + 8 + 3 6664 (05/061

'11. Write short notes on any three of the following :    3x5