These multiple-choice questions related to computer science. These Mcqs are given from the book which will helps to prepare you for the test and learn basic knowledge about Computer Networks
1.Protocols are
(a) agreements on how communication components and DTE’s are to communicate
(b) logical communication channels used for transferring data
(c) physical communication channels used for transferring data
(d) none of the above
2.The method of communication in which transmission takes place in both directions. but only In one direction at a time is called
(a) simplex
(b) four wire circuit
(c) hill duplex
(d) half duplex
3.Error detection at the data link level is achieved by
(a) bit stuffing
(b) cyclic redundancy codes
(c) Hamming codes
(d) equalization
4.Which of the following is a wrong example of a network layer?
(a) Internet Protocol (IP)-ARPANET
(b) X.25 Packet Level Protocol (PLP)-ISO
(c) Source routing and domain naming•USENET
(d) X.25 level 2-ISO
5.The topology with the highest reliability is
(a) bus topology
(b) star topology
(c) ring topology
(d) mesh topology
6.Baud means
(a) the number of bits transmitted per unit time
(b) the number of bytes transmitted per unit time
(c) the rate at which the signal changes
(d) none of the above
7.Start and stop bits are used in serial communication for
(a) error detection
(b) error confection
(c) synchronization
(d) slowing down the communication
8.Unmodulated signal coming from a transmitter is known as
(a) carrier signal
(b) baseband signal
(c) primary signal
(d) none of the above
9.Manchester code is a
(a) Bi-polar code
(b) non return to rem code
(c) polar code
(d) none of the above
10.Pick the incorrect statements.
(a) Another name for primary/secondary protocol is master/slave.
(b) Peer to peer protocol provides equal status to all sites on the channel.
(c) Priority. non-priority types come under master/slave protocol.
(d) TDM is a primary/secondary non-priority system.
11.Pick the correct statements.
(a) A switched circuit is a dial-up circuit rat may encounter blockage (busy signal).
(b) Non switched leased line supports higher data volume and quality than switched lines.
(c) Non switched lines are expensive for high volume data.
(d) Switched circuit provides faster response time.
12.Pick the incorrect statements that pertain to error retransmission used in continuous ARQ method.
(a) Go-back-N method requires more storage at the receiving site.
(b) Selective Repeat involves complex login than Go-back-N.
(c) Go-back-N has better line utilisation.
(d) Selective Repeat has better line utilisation.
13.In the carrier sense network if the prevailing condition is a ‘channel busy’, then which of the following are correct?
(a) If the technique used is non-persistent then it results in randomised wait and sense.
(b) If the technique used is 1-persistent then the channel is continually sensed.
(c) If the technique used is p-persistent then randomised retransmission is done.
(d) If the method used is non-persistent then continuous sensing results.
14.Which of the following are non-polling systems?
(a) TDMA
(b) Stop and Wait
(c) Xon/Xof f
(d) Continuous ARQ
15.Pick the systems that can be used in both priority and non-priority modes.
(a) TDM
(b) Register insertion
(c) Carrier sense systems
(d) Token passing
16.How many characters per sec (7 bits + 1 parity) can be transmitted over a 2400 bps line if the transfer is synchronous (1 start and 1 stop bit)?
(a) 300
(b) 240
(c) 250
(d) 275
27.Which one of the following network uses dynamic or adaptive routing?
(a) TYMNET
(b) ARPANET
(c) SNA (IBM’s System Network Architecture)
(d) None of the above
28.The number of cross point needed for 10 lines in a cross point switch which is full duplex in nature and there are no self connection is
(a) 100
(b) 45
(c) 50
(d) 90
29.A terminal multiplexer has six 1200 bps terminals and M’ 300 bps terminals connected to it. The outgoing line is 9600 bps. What is the maximum value of n?
(a) 4
(b) 16
(c) 8
(d) 28
30.The difference between a multiplexer and a statistical multiplexer is:
(a) Multiplexers use TDM (time division multiplexing). while statistical multiplexer uses EOM (frequency division multiplexing).
(b) Multiplexers often waste the output link capacity, while statistical multiplexers optimize its use.
(c) Statistical multiplexers need buffers while multiplexers do not need buffers.
(d) Multiplexers use the X.25 protocol, while statistical multiplexers use the ALOHA protium!.
31.A modem constellation diagram has data points at (0, I) and (0, 2). What type of modulation does the modem use?
(a) Phase modulation
(b) Amplitude modulation
(c) Both (a) and (b)
(d) None of the above
32.
33.Maximum data rate of a channel for a noiseless 3-kHz binary channel is
(a) 3000 bps
(b) 6000 bps
(a) 1500 bps
(d) none of the above
34.The maximum data rate of a channel of 3000•Hz bandwidth and SNR of 30 dB is
(a) 15.000 bps
(b) 60,000 bps
(c) 30.000 bps
(d) 3.000 bps
35.In time division switches if each memory access takes 100 ns and one frame period is 125 micro second. then the maximum number of lines that can be supported is
(a) 625 lines
(b) 1250 lines
(c) 2300 lines
(d) 318 lines
36.If the bit string 01 1 1 1 01 1 1 1 1 0 1 1 1 11 1 0 is subjected to bit stuffing for the flag string 0 1 1 1 1 11 0. the output string is
(a) 011110111110011111010
(b) 01111011111011111100
(c) 01111011111011111010
(d) 0111101111101111110
44.The measures the number of lost or garbled messages as a fraction of the total sent in the sampling period.
(a) Residual Error rate
(b) Transfer failure probability
(c) Connection release failure probability
(d) Connection establishment failure probability
45.In session layer, during data transfer, the data stream responsible for the control purpose (i.e. control of the session layer itself) is
(a) regular data
(b) typed data
(c) capability data
(d) expedited data
46.The minimum number of bits required to represent B is
(a) 1
(b) 2
(c) 3
(d) 4
47.The minimum number of bits required to represent all the symbols together is
(a) 14
(b) 11
(c) 12
(d) 15
48.The average code length of the given problem is
(a) 2
(b) 2.25
(c) 2.45
(d) 3
49.In cryptography. the following uses transposition ciphers and the keyword is LAYER. En-crypt the following message. (Spaces are omitted during encryption) WELCOME TO NETWORK SECURITY!
(a) WHEKREETS I LTWETCOOCYONRU I
(b) EETS /COOCYWMEKRONRU !LTWET
(c) LTWETONRU ! WMEKRCOOCYEETSI
(d) ONRU ! COOCYLTWETEETS IWMEKR
50.Encrypt NEKEWNINRROGTTI using the above keyword in Transposition cipher method.
(a) INTERWORKINGNET
(b) INTERNETWORKING
(c) WORKINGINTERNET
(d) None of the above
51.Assuming that for a given network layer implementation. connection establishment overhead is 100 bytes and disconnection overhead is 28 bytes. What would be the minimum size of a packet the transport layer needs to keep up. if it wishes to implement a datagram service above the network layer and needs to keep its overhead to a maximum of 12.5%. (Ignore transport layer overhead.)
(a) 512 bytes
(b) 768 bytes
(c) 1152 bytes
(d) 1024 bytes 52. Which of the following is not a standard RS-232C signal?
(a) RTS
(b) CTS
(c) DSR
(d) VDR 53. A high speed communication equipment typically would not be needed for
(a) E-mail
(b) transferring large volume of data
(c) supporting communication between nodes in a LAN
(d) all of the above
54.Which of the following ISO level is more closely related to the physical communications facilities?
(a) Application
(b) Session
(c) Network
(d) Data link
55.Which of the following is not a field in the Ethernet message packet?
(a) Type
(b) Data
(c) Pin-code
(d) Address
56.The network topology that supports bi-directional links between each possible node is
(a) ring •
(b) star
(c) tree
(d) mesh
57.In a broad sense, a railway track is an example of
(a) simplex
(b) half-duplex
(c) kill-duplex
(d) an of the above
58.The frequency range at which the land coaxial cables will be used is
(a) 106 to 108 Hz
(b) 1010 to 10″ Hz
(c) 103 to le Hz
(d) 10″ to 1013 Hz
59.If the data rate of ring is 20 Mbps, signal propagation speed is 200 mists, then the number of bits that can be placed on the channel of 200 km is
(a) 2000 bits
(b) 20,000 bits
(c) 1.000 bits
(d) none of the above
60.ICI (interface control information) is
(a) used to transfer user data from layer to layer
(b) used to exchange information by peer entities at different sites on the network to instruct an entity to perform a service function
(c) a combination of service data unit (SDU) and protocol control information (PCI) (d) a temporary parameter passed between N and N – 1 layers to involve service functions
between two layers
61.Match the following
2.Data link layer
3.Physical layer
4.Presentation layer
5.Network layer
(i) the lowest layer whose function is to activate, deactivate and maintain the cir-cuit between DM and. DCE
(ii) performs routing and communication
(iii) detection and recovery from errors in the transmitted data
(iv) Provides for the syntax of the data
(a) 1-(iii), 2-(i). 3-(iv).4-(ii)•
(b) 1-(ii). 2-(i). 3-(iv), 4-(iii)
(c) 2-(i), 3-(ii), 4-(iii)
(d) 1-(ii), 2-(i), 4-(iv)
(i) the lowest layer whose function is to activate, deactivate and maintain the cir-cuit between DM and. DCE
(ii) performs routing and communication
(iii) detection and recovery from errors in the transmitted data
(iv) Provides for the syntax of the data
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