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VU CS601 – DATA COMMUNICATION FINALTERM solved unsolved past papers Spring 2010

VU CS601 – DATA COMMUNICATION FINALTERM Solved Unsolved Past Papers Spring 2010

FINALTERM  EXAMINATION

Spring 2010

CS601- Data Communication

Time: 90 min

Marks: 60

Student Info
Student ID:
Center:
Exam Date:

 

 

For Teacher’s Use Only

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Question No: 1      ( Marks: 1 ) – Please choose one

 

 

__________representation of links that connect nodes is called as physical topology.

 

       ► geometrical

 

       ► logical

 

       ► physical

 

 

 

Question No: 2      ( Marks: 1 ) – Please choose one

 

 

The internet model consists of _________ layers.

 

       ► three

 

       ► two

 

       ► five

 

       seven

 

 

 

Question No: 3      ( Marks: 1 ) – Please choose one

 

 

Encryption and encoding are the same terms.

 

       ► True

 

       False

 

 

 

Question No: 4      ( Marks: 1 ) – Please choose one

 

 

The amplitude of a digital signal depends upon the________ to represent a bit.

 

       ► phase

 

       ► voltage

 

       ► wavelength

 

 

 

Question No: 5      ( Marks: 1 ) – Please choose one

 

 

The inversion of the level at 1 bit is called as __________

 

       ► NRZ-L

 

       NRZ-I

 

       ► RZ

 

 

 

Question No: 6      ( Marks: 1 ) – Please choose one

 

 

Modulation of an analog signal can be accomplished through changing the ___________ of the carrier signal.

 

       ► amplitude

 

       ► frequency

 

       ► phase

 

       all of the given

 

 

 

Question No: 7      ( Marks: 1 ) – Please choose one

 

 

If FCC regulations are followed, the carrier frequencies of adjacent AM radio stations are ____________ apart.

 

       ► 5 KHz

 

       ► 10 KHz

 

       ► 200 KHz

 

       ► 530 KHz

 

 

 

Question No: 8      ( Marks: 1 ) – Please choose one

 

 

Category 5 UTP cable is used for data transmission of upto__________.

 

       100 Mbps

 

       ► 200 Mbps

 

       ► 250 Mbps

 

       ► 400 Mbps

 

 

 

Question No: 9      ( Marks: 1 ) – Please choose one

 

 

The RG number gives us information about ________.

 

       Twisted pairs

 

       Coaxial cables

 

       ► Optical fibers

 

       ► all of the given

 

 

 

Question No: 10      ( Marks: 1 ) – Please choose one

 

 

The inner core of an optical fiber is __________ in composition.

 

       Glass plastic

 

       Copper

 

       ► Bimetallic

 

       ► Liquid

 

 

 

Question No: 11      ( Marks: 1 ) – Please choose one

 

 

All of popular Fiber optic connectors are ___________ shaped.

 

       ► Conical

 

       ► Barrel

 

       ► Circular

 

       ► Rectangular

 

 

 

Question No: 12      ( Marks: 1 ) – Please choose one

 

 

The VLF and LF bands use _________ propagation for communications.

 

       ► Ground

 

       ► Sky

 

       ► Line of sight

 

       ► Space

 

 

 

Question No: 13      ( Marks: 1 ) – Please choose one

 

 

Multiplexing is the set of techniques that allows simultaneous TX of multiple signals across  ___________ data link

 

 

       ► Single

 

       ► Multi

 

       ► Single and Multi

 

       ► none of the given

 

 

 

Question No: 14      ( Marks: 1 ) – Please choose one

 

 

A portion of the path that carries TX b/w a given pair of devices is known as __________.

 

       ► Node

 

       ► Bridge

 

       Channel

 

       ► Gateway

 

 

 

Question No: 15      ( Marks: 1 ) – Please choose one

 

 

Which error detection method involves polynomials?

 

       ► Checksum

 

       ► Two-dimensional parity check

 

       ► CRC

 

       ► Simple parity check

 

 

 

Question No: 16      ( Marks: 1 ) – Please choose one

 

 

If the ASCII character G is sent and the character D is received, what type of error is this?

 

       Single-bit

 

       ► Multiple-bit

 

       ► Burst

 

       ► Recoverable

 

 

 

Question No: 17      ( Marks: 1 ) – Please choose one

 

 

Which error detection method involves the use of parity bits?

 

       ► Simple parity check & two dimensional parity check

 

       ► CRC

 

       ► Two-dimensional parity check

 

       Simple parity check

 

 

 

Question No: 18      ( Marks: 1 ) – Please choose one

 

 

Which error detection method can detect a single-bit error?

 

       ► Simple parity check

 

       ► Two-dimensional parity check

 

       ► CRC

 

       ► All of the given

 

 

 

Question No: 19      ( Marks: 1 ) – Please choose one

 

 

The Hamming code is a method of __________

 

       ► Error detection

 

       Error correction

 

       ► Error ecapsulation

 

       ► Error detection & Error encapsulation

 

 

 

Question No: 20      ( Marks: 1 ) – Please choose one

 

 

Sliding window requires that data frames be transmitted _______________

 

       Sequentially

 

       ► Frequently

 

       ► Synchronously

 

       ► Asynchronously

 

 

 

Question No: 21      ( Marks: 1 ) – Please choose one

 

 

In selective-reject ARQ, only the specific damaged or lost frame is_____________.

 

       ► Retransmitted

 

       ► Forwarded

 

       ► Selected

 

       ► Rejected

 

 

 

Question No: 22      ( Marks: 1 ) – Please choose one

 

 

Which of the following sublyer, resolves the contention for the shared media

 

       ► MAC

 

       ► LLC

 

       ► Physical

 

 

 

Question No: 23      ( Marks: 1 ) – Please choose one

 

 

The PDU  has no flag fields, no CRC, and no station address

 

       ► TRUE

 

       ► FALSE

 

 

 

Question No: 24      ( Marks: 1 ) – Please choose one

 

 

IEEE divides the base band category into  ______ standards.

 

       5

 

       ► 4

 

       ► 3

 

       ► 6

 

 

 

Question No: 25      ( Marks: 1 ) – Please choose one

 

 

Like 10 Base 5, 10 Base 2 is a _________ topology LAN

 

       ► Ring

 

       ► Mesh

 

       ► Star

 

       Bus

 

 

 

Question No: 26      ( Marks: 1 ) – Please choose one

 

 

Check sum method is used for _______________ layers.

 

       ► Physical

 

       ► Application

 

       ► Transport

 

       ► Datalink

 

 

 

Question No: 27      ( Marks: 1 ) – Please choose one

 

 

Repeater works on __________     layer.

 

       ► Data Link

 

       Physical

 

       Network

 

       ► Application

 

 

 

Question No: 28      ( Marks: 1 ) – Please choose one

 

 

Trunks are transmission media such as _________ that handle the telephone to the nearest end office.

 

       ► Satellite links

 

       ► Twisted-pair & Fiber-optic

 

       ► Twisted-pair

 

       ► Fiber-optic

 

 

 

Question No: 29      ( Marks: 1 ) – Please choose one

 

 

Which of the following ___________ uses a series of filters to decompose multiplexed signal into its constituent signals.

 

       ► MUX

 

       ► DEMUX

 

       ► Switch

 

       ► Bridge

 

 

 

Question No: 30      ( Marks: 1 ) – Please choose one

 

 

In Fast Ethernet, data rate can be increased by _______________ collisions.

 

       ► Increasing

 

      Decreasing

 

       ► Keeping Constant

 

       ► None of the given

 

 

 

Question No: 31      ( Marks: 2 )

 

 

What are the advantages of a multipoint connection over a point-to-point connection?

Answer:

Point-to-point connection is limited to two devices, where else more than two devices share a single link in multipoint connection. Multipoint connection can be used for fail-over and reliability.

 

 

Question No: 32      ( Marks: 2 )

 

 

What’s the name of the telephone service in which there is no need of dialing.

 

Answer:

 

DSS (digital data service)   is the telephone service in which there is no need of dialing.

 

 

 

 

Question No: 33      ( Marks: 2 )

 

 

Which type of frames are present in BSC frames?

 

Answer:

There are two types of frames that are present in BSC.

  1. Control Frames and
  2. Data Frames

 

 

 

 

Question No: 34      ( Marks: 2 )

 

 

What methods of line discipline are used for peer to peer and  primary secondary communication?

Answer:

Line discipline is done in two ways:

  1. ENQ/ACK      (Enquiry Acknowledgement)

 

This is used for peer to peer communication.

  1. Poll/ Select

This method is used for primary secondary communication.

 

 

Question No: 35      ( Marks: 3 )

 

 

How does the checksum checker know that the received data unit is undamaged? [3]

 

Answer:

 

Checksum Checker or generator:

The sender subdivides data units into equal segments of ‘n’ bits(16 bits)

  1. These segments are added together using one’s complement.
  2. The total (sum) is then complemented and appended to the end of the original data unit as redundancy bits called CHECKSUM.
  3. The extended data unit is transmitted across the network.
  4. The receiver subdivides data unit and adds all segments together and complement the result.
  5. If the intended data unit is intact, total value found by adding the data segments and the checksum field should be zero.
  6. 6.      If the result is not zero, the packet contains an error & the receiver rejects it.

 

 

 

 

 

 

 

Question No: 36      ( Marks: 3 )

 

 

Which one has more overhead, a repeater or a bridge? Explain your answer. [3]

 

Answer:

A bridge has more overhead than a repeater. A bridge processes the packet at two

layers ; a repeater processes a frame at only one layer. A bridge needs to search a

table and find the forwarding port as well as to regenerate the signal; a repeater

only regenerates the signal. In other words, a bridge is also a repeater (and more); a

repeater is not a bridge.

 

 

Question No: 37      ( Marks: 3 )

 

 

Write down disadvantages of Ring Topology.

 

Answer:

Disadvantages of Ring Topology

 

Unidirectional Traffic

A break in a ring that is a disabled station can disable the entire network

 

Can be solved by using:

Dual Ring or

A switch capable of closing off the Break

 

 

 

Question No: 38      ( Marks: 3 )

 

 

How parity bits are counted in VRC error detection method technique in case of odd parity generator?

 

Answer:

For example:

We want to TX the binary data unit 1100001

Adding together the number of 1’s gives us 3, an odd number

Before TX, we pass the data unit through a parity generator, which counts the 1’s and appends the parity bit (1) to the end

The total number of 1’s is now 4, an even number

The system now transfers the entire expanded across the network link

 

When it reaches its destination, the RX puts all 8 bits through an even parity checking function

If the RX sees 11100001, it counts four ones, an even number and the data unit passes

When the parity checker counts the 1’s, it gets 5 an odd number

The receiver knows that an error has occurred somewhere and therefore rejects the whole unit

Some systems may also use ODD parity checking

The principal is the same as even parity

 

 

 

 

 

 

 

Question No: 39      ( Marks: 5 )

 

 

How are lost acknowledgment and a lost frame handled at the sender site? [5]

 

Answer:

At some error rates (16%-20%) the protocol hung up in an infinite loop, while it worked fine for other error rates. On examining the code it was determined that this problem resulted from improper variable initialization. On these certain error rates the pseudo-random number generator caused the very first frame sent to be lost or damaged. The receiver used a variable to keep track of the last in sequence frame received. This was erroneously initialized to 0. Therefore if the first frame got lost (sequence no 0), when the receiver received the second frame (sequence number 1) it sent an acknowledgment for the last in sequence frame  received, which had been initialized to 0. Therefore the sender received an acknowledgement for sequence number 0 and moved its window up accordingly. It caused everything to get out of synch, and caused the protocol to go into infinite loop.  This was resolved by initializing the variable to remember the last in sequence frame received to an out of range sequence number.

 

 

 

 

 

Question No: 40      ( Marks: 5 )

 

 

Explain Protocol Data Unit (PDU)?

 

 

Answer:

Protocol data unit (PDU) is an OSI term that refers generically to a group of information added or removed by a particular layer of the OSI model. In specific terms, an LxPDU implies the data and headers defined by layer x. Each layer uses the PDU to communicate and exchange information. The PDU information is only read by the peer layer on the receiving device and then stripped off, and data is handed over to the next upper layer.

 

 

 

 

 

VU CS601 – DATA COMMUNICATION FINALTERM Solved Unsolved Past Papers Spring 2010

VU CS601 – DATA COMMUNICATION FINALTERM solved unsolved past papers Spring 2009

VU CS601 – DATA COMMUNICATION FINALTERM Solved Unsolved Past Papers Spring 2009

FINALTERM  EXAMINATION

Spring 2009

CS601- Data Communication

Ref No: 656191

Time: 120 min

Marks: 80

 

 

For Teacher’s Use Only

Q No.

1

2

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Question No: 1      ( Marks: 1 ) – Please choose one

 

 

Which is not an element of protocol

 

 

       ► semantics

 

       timing

 

       ► communication service module

 

 

 

Question No: 2      ( Marks: 1 ) – Please choose one

 

 

Layers 5, 6 and 7 also called as network support layers.

 

       ► True

 

       ► False

 

 

 

Question No: 3      ( Marks: 1 ) – Please choose one

 

 

Fourier transform tells us that any digital signal can be decomposed into infinite number of periodic signals

 

       ► True

 

       ► False

 

 

 

Question No: 4      ( Marks: 1 ) – Please choose one

 

 

Time domain plot show changes in signal phase with respect to time.

 

       ► True

 

       ► False

 

 

 

Question No: 5      ( Marks: 1 ) – Please choose one

 

 

Analog to digital conversion is also termed as modulating an analog signal.

 

       ► True

 

       ► False

 

 

 

Question No: 6      ( Marks: 1 ) – Please choose one

 

 

DC component is also termed as Direct current component or a component with non-zero frequency.

 

       ► False

 

       ► True

 

 

 

Question No: 7      ( Marks: 1 ) – Please choose one

 

 

Manchester is a type of ____________encoding.

 

       ► biphase

 

       ► polar

 

       ► biphase & polar

 

       ► none of the given

 

 

 

Question No: 8      ( Marks: 1 ) – Please choose one

 

 

The inversion of the level at 1 bit is called as __________

 

       ► NRZ-L

 

       ► NRZ-I

 

       ► RZ

 

 

 

Question No: 9      ( Marks: 1 ) – Please choose one

 

 

PCM is the first process of PAM.

 

       ► True

 

       ► False

 

 

 

Question No: 10      ( Marks: 1 ) – Please choose one

 

 

In 4PSK each phase change represents ______bits.

 

       ► 3

 

       ► 6

 

       ► 2

 

       ► 4

 

 

 

Question No: 11      ( Marks: 1 ) – Please choose one

 

 

In RS 422 Balanced mode two lines carry ________ signals which are not identical to each other.

 

       ► same

 

       ► different

 

       ► digital

 

       ► analog

 

 

 

Question No: 12      ( Marks: 1 ) – Please choose one

 

 

A ______________ converts an analog signal into a digital signal.

 

       ► Demodulator

 

       ► Modulator

 

       ► Digital-to-analog converter

 

 

 

Question No: 13      ( Marks: 1 ) – Please choose one

 

 

Which of the following is an example of ITU-T modem standards:

 

       ► T-series

 

       ► X-series

 

       ► N-series

 

       ► V-series

 

 

 

Question No: 14      ( Marks: 1 ) – Please choose one

 

 

The maximum data rate in the uploading direction is still ____________.

 

 

       ► 26.6 Kbps

 

       ► 33.6 Kbps

 

       ► 36.6 Kbps

 

       ► 46.6 Kbps

 

 

 

Question No: 15      ( Marks: 1 ) – Please choose one

 

 

Which of the following primarily uses guided media

 

       ► Cellular telephone system

 

       ► Local telephone system

 

       ► Satellite communications

 

       ► Radio broadcasting

 

 

 

Question No: 16      ( Marks: 1 ) – Please choose one

 

 

When a beam of light travels through media of two different densities, if the angle of incidence is greater than the critical angle, ____________occurs.

 

       ► Reflection

 

       ► Refraction

 

       ► Incidence

 

       ► Criticism

 

 

 

Question No: 17      ( Marks: 1 ) – Please choose one

 

 

When we talk about unguided media, usually we are referring to _________.

 

 

       ► Metallic wires

 

       ► Nonmetallic wires

 

       ► The air

 

       ► Water

 

 

 

Question No: 18      ( Marks: 1 ) – Please choose one

 

 

Optical fibers are defined by the ratio of the ___________ of their core to the diameter of their cladding.

 

       ► Diameter

 

       ► Radius

 

       ► Length

 

       ► Width

 

 

 

Question No: 19      ( Marks: 1 ) – Please choose one

 

 

All of popular Fiber optic connectors are ___________ shaped.

 

       ► Conical

 

       Barrel

 

       ► Circular

 

       ► Rectangular

 

 

 

Question No: 20      ( Marks: 1 ) – Please choose one

 

 

Radio wave transmission utilizes ___________ different types of propagation.

 

       ► Four

 

       ► Three

 

       ► Two

 

       ► Five

 

 

 

Question No: 21      ( Marks: 1 ) – Please choose one

 

 

dB is ____________ if a signal is amplified.

 

       ► Negative

 

       ► Positive

 

       ► Null

 

       ► Zero

 

 

 

Question No: 22      ( Marks: 1 ) – Please choose one

 

 

A prism can deflect the light depending upon the angle of ____________ and the frequency.

 

 

       ► Deviation

 

       ► Incident

 

       ► Refraction

 

       ► Reflection

 

 

 

Question No: 23      ( Marks: 1 ) – Please choose one

 

 

Asynchronous TDM is efficient only when the size of the time slot is kept relatively _______________

 

       ► Large

 

       ► Small

 

       ► Medium

 

       ► None of the given

 

 

 

Question No: 24      ( Marks: 1 ) – Please choose one

 

 

The local loop has ___________ cable that connects the subscriber telephone to the nearest end office.

 

       ► Twisted-pair

 

       ► Coaxial

 

       ► Fiber-optic

 

       ► None of the given

 

 

 

Question No: 25      ( Marks: 1 ) – Please choose one

 

 

Data from a computer are ____________; the local loop handles _________ signals.

 

       ► Analog; analog

 

       ► Analog; digital

 

       ► Digital; digital

 

       ► Digital; analog

 

 

 

Question No: 26      ( Marks: 1 ) – Please choose one

 

 

Which error detection method uses ones complement arithmetic?

 

       ► Simple parity check

 

       ► Two-dimensional parity check

 

       ► CRC

 

       ► Checksum

 

 

 

Question No: 27      ( Marks: 1 ) – Please choose one

 

 

Flow control is needed to prevent ____________

 

       ► Bit errors

 

       ► Overflow of the sender buffer

 

       ► Overflow of the receiver buffer

 

       ► Collision between sender and receiver

 

 

 

Question No: 28      ( Marks: 1 ) – Please choose one

 

 

____________ coordinates the amount of data that can be sent before receiving acknowledgment

 

       ► flow control

 

       ► error control

 

       ► data control

 

 

 

Question No: 29      ( Marks: 1 ) – Please choose one

 

 

Error control is both error _________ and error ___________

 

       ► detection; correction

 

       ► detection; deletion

 

       ► detection; avoidance

 

       ► detection; forwarding

 

 

 

Question No: 30      ( Marks: 1 ) – Please choose one

 

 

Addressing is not needed in _______________ configuration.

 

       Point to Point

 

       ► Multipoint

 

       ► Point to point and multipoint

 

 

 

Question No: 31      ( Marks: 1 ) – Please choose one

 

 

In a Go-Back-N ARQ, if the window size is 63, what is the range of sequence number?

 

       ► 0 to 63

 

       ► 0 to 64

 

       ► 1 to 63

 

       ► 1 to 64

 

 

 

Question No: 32      ( Marks: 1 ) – Please choose one

 

 

A timer is set when ___________ is sent out.

 

       ► A data frame

 

       ► An ACK

 

       ► A NAK

 

 

 

Question No: 33      ( Marks: 1 ) – Please choose one

 

 

Sliding window requires that data frames be transmitted _______________

 

       ► Sequentially

 

       ► Frequently

 

       ► Synchronously

 

       ► Asynchronously

 

 

 

Question No: 34      ( Marks: 1 ) – Please choose one

 

 

In Y-MODEM Multiple files can be sent simultaneously

 

       ► True

 

       ► False

 

 

 

Question No: 35      ( Marks: 1 ) – Please choose one

 

 

BLAST stands for :

 

       ► Blocked asynchronous transmission

 

       ► Blocked synchronous transmission

 

       ► Barrel asynchronous transmission

 

       ► Below asynchronous transmission

 

 

 

Question No: 36      ( Marks: 1 ) – Please choose one

 

 

HDLC is an acronym for ______________.

 

       ► High-duplex line communication

 

       ► High-level data link control

 

       ► Half-duplex digital link combination

 

       ► Host double-level circuit

 

 

 

Question No: 37      ( Marks: 1 ) – Please choose one

 

 

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

 

 

       ► Flag

 

       ► Address

 

       ► Control

 

       ► FCS

 

 

 

Question No: 38      ( Marks: 1 ) – Please choose one

 

 

_________ is the access protocol used by traditional Ethernet.

 

       ► CSMA/CD

 

       ► CSMA/CA

 

       ► Token Ring

 

       ► CSMA

 

 

 

Question No: 39      ( Marks: 1 ) – Please choose one

 

 

Bridges can divide a large ________ into smaller segments

 

       ► Network

 

       ► Packet

 

       ► Frame

 

       ► Address

 

 

 

Question No: 40      ( Marks: 1 ) – Please choose one

 

 

Like VRC, LRC and CRC, Checksum is also based on _______________.

 

       ► Redundency

 

       ► Decimal Division

 

       ► Encryption

 

       ► Encoding

 

 

 

Question No: 41      ( Marks: 2 )

 

 

What are the conditions for the polynomial used by the CRC generator?

 

CRC generator:

CRC generator (the divisor) is most often represented not as a1’s and 0’s but as an algebraic polynomial.

conditions for the polynomial:

it should have following properties:

It should not be divisible by “x”.

It should not be divisible by “x+1”.

The first condition guarantees that all burst error of a length equal to degree of the polynomial is detected.

The 2nd condition guarantees that all burst error affecting an odd number of bits are detected.

 

 

Question No: 42      ( Marks: 2 )

 

 

What are intelligent modems?

Intelligent modems:

 

A modem that responds to commands and can accept new instructions during online transmission. It was originally developed by Hayes.

Example:

  • Automatic answering,
  • Dialing etc.

 

Question No: 43      ( Marks: 2 )

 

 

What is the basic purpose of Router?

 

Basic purpose of Router:

“A router is a device that extracts the destination of a packet it receives, selects the best path to that destination, and forwards data packets to the next device along this path. They connect networks together;

a LAN to a WAN for example, to access the Internet.
“A more precise definition of a router is a computer networking device that interconnects separate logical subnets.”

 

Question No: 44      ( Marks: 3 )

 

 

What are the fractional T Lines?

 

The fractional T Lines:

Many subscribers don’t need the entire capacity of the T-line.

For example,

A small business may need only one-fourth of the capacity of T-line. if four business of same size lie in the same building, they can share  T-line.DSU/CSU allow the capacity of T-line to be interleaved in to four channels

 

 

Question No: 45      ( Marks: 3 )

 

 

 

What are the light sources used for optic fiber?

 

  • light sources used for optic fiber:
  • The light source can weather be an LED or ILD
  • LED (Light emitting diode) cheaper but provide unfocused light that strikes the boundaries of channel at uncontrollable angles.
  • Limited to short distance use.
  • LASSER
  • Can be focused to a narrow range allowing control over angle of incidence.

 

 

 

 

 

 

Question No: 46      ( Marks: 3 )

 

 

What is Multi Access Unit (MAU) in Token Ring?

 

 

 

Multi Access Unit (MAU) in Token Ring:

  • Individual automatic switches are combined in to a hub
  • One MAU can support up to 8 stations.
  • Although it looks like a star, it is in fact a ring.

 

 

 

Question No: 47      ( Marks: 5 )

 

 

Give characteristics of Dual Ring, if necessary then draw the diagram. [5]

 

 

 

 

 

 

Characteristics of Dual Ring:

A network topology in which two concentric rings connect each node on a network instead of one network ring that is used in a ring topology. Typically, the secondary ring in a dual-ring topology is redundant. It is used as a backup in case the primary ring fails. In these configurations, data moves in opposite directions around the rings. Each ring is independent of the other until the primary ring fails and the two rings are connected to continue the flow of data traffic.

 

 

 

 

 

 

 

 

 

 

 

 

Node

Node

Node

Node

Node

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Question No: 48      ( Marks: 5 )

 

 

 

 

 

What the receiver will receive if the checksum method is applied to the following

 

bit.

10101001  00111001

 

 

 

 

 

 

 

 

Ans:

 

 

the receiver will receive the checksum method is applied to the following bit.

10101001  00111001

10101001  00111001

Sum of 2 bits are

10101001

00111001

——————-

11100010

00011101       1’s complement

1

————–

00011110        2’s complement

———–

10101001      00111001    ==>  00011110

So the data transmitted which will receiver get:
10101001 00111001 00011110

 

Question No: 49      ( Marks: 5 )

 

 

What is rafraction in terms of optic fiber? Give one example.

 

 

Refraction:

Light travels in a straight line as long as it is moving through a single uniform structure If a ray of light traveling through one substance enters another (more or less dense) substance, its speed changes abruptly causing the ray to change direction. This phenomenon is called Refraction.

 

Refraction in terms of optic fiber:

 

the propagation of light in an optical fiber which in its simplest form consists of a circular core of uniform refractive index surrounded by a cladding of slightly lower refractive index. The light is launched into the entrance face of the fiber.

The light is propagated by the total internal reflection at the interface between core and cladding. However the rays incident at angles larger than a certain angle, called the cut-off angle, suffer both refraction and reflection at the interface between the core and the cladding.

They, therefore, are not guided. Due to this the optical fiber has a numerical aperture. The numerical aperture is given by the square root of (n12-n22). Typical values of numerical aperture lie between 0.1 and 0.3.

 

The refractive indices of the core and the cladding are n1 and n 2 respectively. The fiber is normally in air (n0=1) but could also be in a medium of refractive index n0.

 

 

 

Question No: 50      ( Marks: 10 )

 

 

What are the asynchronous protocols in data link layer? Discuss in detail with examples.  [10 marks]

 

 

Asynchronous protocols in data link layer:

Asynchronous communication at the data link layer or higher protocol layers is known as statistical multiplexing or packet mode communication,

For example :

Asynchronous transfer mode (ATM). In this case the asynchronously transferred blocks are called data packets,

Async protocols in Data link layer is called statistical multiplexing. for example ATM cells.

The opposite is circuit switched communication, which provides constant bit rate, for example ISDN and SONET/SDH.

The packets may be encapsulated in a data frame, with a frame synchronization bit sequence indicating the start of the frame, and sometimes also a bit synchronization bit sequence, typically 01010101, for identification of the bit transition times. Note that at the physical layer, this is considered as synchronous serial communication.

Examples of packet mode data link protocols that can be/are transferred using synchronous serial communication are the

  • HDLC,
  • Ethernet,
  • PPP and
  • USB protocols.

 

VU CS601 – DATA COMMUNICATION FINALTERM Solved Unsolved Past Papers Spring 2009

VU CS601 – DATA COMMUNICATION FINALTERM solved unsolved past papers Fall 2009

VU CS601 – DATA COMMUNICATION FINALTERM Solved Unsolved Past Papers Fall 2009

FINALTERM  EXAMINATION

Fall 2009

CS601- Data Communication

Ref No: 1140267

Time: 120 min

Marks: 85

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Exam Date:

 

 

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Question No: 1      ( Marks: 1 ) – Please choose one

 

 

The information to be communicated in a data communications system is the

 

       ► Medium

 

       ► Protocol

 

       ► Message

 

       ► Transmission

 

 

 

Question No: 2      ( Marks: 1 ) – Please choose one

 

 

A set of devices connected by communication links is called networking

 

       ► True

 

       ► False

 

 

 

Question No: 3      ( Marks: 1 ) – Please choose one

 

 

Internet with small “i” specifies the world wide Network the actual internet.

 

       ► True

 

       ► False

 

 

 

Question No: 4      ( Marks: 1 ) – Please choose one

 

 

Data chunk at data link layer is called________

 

       ► frame

 

       ► packet

 

       ► datagram

 

 

 

Question No: 5      ( Marks: 1 ) – Please choose one

 

 

Data synchronization is a function related with ___________

 

       ► session layer

 

       ► presentation layer

 

       ► transport

 

 

 

Question No: 6      ( Marks: 1 ) – Please choose one

 

 

When data are transmitted from device A to device B, the header from A’s layer 4 is read by B’s __________ layer.

 

       ► physical

 

       ► transport

 

       ► application

 

       ► none of the given

 

 

 

Question No: 7      ( Marks: 1 ) – Please choose one

 

 

Data must be converted into__________ before transmission.

 

 

       ► signal

 

       ► wave

 

       ► electric pulse

 

 

 

Question No: 8      ( Marks: 1 ) – Please choose one

 

 

PCM is the first process of PAM.

 

       ► True

 

       ► False

 

 

 

Question No: 9      ( Marks: 1 ) – Please choose one

 

 

In _____________ transmission, bits are transmitted over a single wire, one at a time.

 

       ► Asynchronous serial

 

       ► Synchronous serial

 

       ► Parallel

 

       ► Asynchronous & Synchronous serial

 

 

 

Question No: 10      ( Marks: 1 ) – Please choose one

 

 

EIA 232 allows for a maximum bit rate of __________Kbps.

 

       ► 40

 

       ► 30

 

       ► 20

 

       ► 10

 

 

 

Question No: 11      ( Marks: 1 ) – Please choose one

 

 

When a beam of light travels through media of two different densities, if the angle of incidence is greater than the critical angle, ____________occurs.

 

       ► Reflection

 

       ► Refraction

 

       ► Incidence

 

       ► Criticism

 

 

 

Question No: 12      ( Marks: 1 ) – Please choose one

 

 

A parabolic dish antenna is a(n) ______________ antenna.

 

       ► Omnidirectional

 

       ► Bidirectional

 

       ► Unidirectional

 

       ► Horn

 

 

 

Question No: 13      ( Marks: 1 ) – Please choose one

 

 

Ultra high-frequency waves always use __________ propagation.

 

       ► Ground

 

       ► Sky

 

       ► Line of Sight

 

       ► Space

 

 

 

Question No: 14      ( Marks: 1 ) – Please choose one

 

 

Middle frequency waves having range 300 KHz-3 MHz always use __________ propagation.

 

 

       ► Ground

 

       ► Sky

 

       ► Line of Sight

 

       ► Space

 

 

 

Question No: 15      ( Marks: 1 ) – Please choose one

 

 

dB is ____________ if a signal is attenuated.

 

       ► Negative

 

       ► Positive

 

       ► Null

 

       ► Zero

 

 

 

Question No: 16      ( Marks: 1 ) – Please choose one

 

 

Which multiplexing technique involves signals composed of light beams?

 

 

       ► FDM

 

       ► TDM

 

       ► WDM

 

       ► none of the given

 

 

 

Question No: 17      ( Marks: 1 ) – Please choose one

 

 

Multiplexing has long been used as an essential tool in the ____________.

 

 

       ► Electronic industry

 

       ► Telephone industry

 

       ► Space science

 

       ► VLAN

 

 

 

Question No: 18      ( Marks: 1 ) – Please choose one

 

 

A telephone network is an example of a __________ network.

 

       ► Packet-switched

 

       ► Circuit-switched

 

       ► Message-switched

 

       ► none of the given

 

 

 

Question No: 19      ( Marks: 1 ) – Please choose one

 

 

The local loop has ___________ cable that connects the subscriber telephone to the nearest end office.

 

       ► Twisted-pair

 

       ► Coaxial

 

       ► Fiber-optic

 

       ► None of the given

 

 

 

Question No: 20      ( Marks: 1 ) – Please choose one

 

 

Which error detection method involves polynomials?

 

       ► Checksum

 

       ► Two-dimensional parity check

 

       ► CRC

 

       ► Simple parity check

 

 

 

Question No: 21      ( Marks: 1 ) – Please choose one

 

 

In CRC there is no error if the remainder at the receiver is ____________

 

       ► Equal to the remainder at the sender

 

       ► Zero

 

       ► Nonzero

 

       ► The quotient at the sender

 

 

 

Question No: 22      ( Marks: 1 ) – Please choose one

 

 

In CRC the quotient at the sender _____________

 

       ► Becomes the dividend at the receiver

 

       ► Becomes the divisor at the receiver

 

       ► is discarded

 

       ► is the remainder

 

 

 

Question No: 23      ( Marks: 1 ) – Please choose one

 

 

Which error detection method can detect a bust error?

 

       ► The parity check

 

       ► Two-dimensional parity check

 

       ► CRC

 

       ► Two-dimensional parity check and CRC

 

 

 

Question No: 24      ( Marks: 1 ) – Please choose one

 

 

At the CRC checker, ________ means that the data unit is damaged

 

       ► A string of 0s

 

       ► A string of 1s

 

       ► A string of alternating 1s and 0s

 

       ► A nonzero remainder

 

 

 

Question No: 25      ( Marks: 1 ) – Please choose one

 

 

Error control is both error _________ and error ___________

 

       ► detection; correction

 

       ► detection; deletion

 

       ► detection; avoidance

 

       ► detection; forwarding

 

 

 

Question No: 26      ( Marks: 1 ) – Please choose one

 

 

In line discipline the initiator first transmits a frame called an ________

 

       ► Enquiry

 

       ► Acknowledgment

 

       ► NAK

 

       ► Request

 

 

 

Question No: 27      ( Marks: 1 ) – Please choose one

 

 

In line discipline after the data transmission, the sending system finishes with an _____________ frame

 

       ► EOT

 

       ► EKT

 

       ► ENT

 

       ► ESP

 

 

 

Question No: 28      ( Marks: 1 ) – Please choose one

 

 

In primary-secondary communication ______________ is always the initiator of a session

 

       ► Primary

 

       ► Secondary

 

       ► Sender

 

       ► Receiver

 

 

 

Question No: 29      ( Marks: 1 ) – Please choose one

 

 

Primary device uses ____________ to receive transmission from the secondary devices.

 

       ► ACK

 

       ► ENQ

 

       ► POLL

 

 

 

Question No: 30      ( Marks: 1 ) – Please choose one

 

 

In a Go-Back-N ARQ, if the window size is 63, what is the range of sequence number?

 

       ► 0 to 63

 

       ► 0 to 64

 

       ► 1 to 63

 

       ► 1 to 64

 

 

 

Question No: 31      ( Marks: 1 ) – Please choose one

 

 

Sliding window requires that data frames be transmitted _______________

 

       ► Sequentially

 

       ► Frequently

 

       ► Synchronously

 

       ► Asynchronously

 

 

 

Question No: 32      ( Marks: 1 ) – Please choose one

 

 

Data link protocols can be divided into ______________ sub-groups.

 

       ► two

 

       ► three

 

       ► four

 

       ► five

 

 

 

Question No: 33      ( Marks: 1 ) – Please choose one

 

 

XMODEM is a ______________ protocol designed for telephone-line communication b/w PCs.

 

       ► file transfer

 

       ► hardware

 

       ► software

 

       ► application exchange

 

 

 

Question No: 34      ( Marks: 1 ) – Please choose one

 

 

In Y-MODEM Multiple files can be sent simultaneously

 

       ► True

 

       ► False

 

 

 

Question No: 35      ( Marks: 1 ) – Please choose one

 

 

Which of the following combines features of the other two.

 

       ► ZMODEM

 

       ► YMODEM

 

       ► XMODEM

 

       ► None of given

 

 

 

Question No: 36      ( Marks: 1 ) – Please choose one

 

 

BLAST stands for :

 

       ► Blocked asynchronous transmission

 

       ► Blocked synchronous transmission

 

       ► Barrel asynchronous transmission

 

       ► Below asynchronous transmission

 

 

 

Question No: 37      ( Marks: 1 ) – Please choose one

 

 

Which one of the following uses full duplex operation with sliding window flow control.

 

       ► BLAST

 

       ► XMODEM

 

       ► YMODEM

 

       ► ZMODEM

 

 

 

Question No: 38      ( Marks: 1 ) – Please choose one

 

 

HDLC is an acronym for ______________.

 

       ► High-duplex line communication

 

       ► High-level data link control

 

       ► Half-duplex digital link combination

 

       ► Host double-level circuit

 

 

 

Question No: 39      ( Marks: 1 ) – Please choose one

 

 

The DSAP and SSAP are addresses used by _________ to identify the protocol stacks.

 

       ► LLC

 

       ► MAC

 

       ► Network

 

 

 

Question No: 40      ( Marks: 1 ) – Please choose one

 

 

The PDU  has no flag fields, no CRC, and no station address

 

       ► TRUE

 

       ► FALSE

 

 

 

Question No: 41      ( Marks: 1 ) – Please choose one

 

 

Which of the following is a bus topology LAN that uses base band signaling and has a max. segment length of 500 meters

 

       ► 10 Base5

 

       ► 10 Base2

 

       ► 100 Base2

 

       ► 100 Base5

 

 

 

Question No: 42      ( Marks: 1 ) – Please choose one

 

 

Token Bus has no commercial application in data communications

 

       ► True

 

       ► False

 

 

 

Question No: 43      ( Marks: 1 ) – Please choose one

 

 

The BNC-T connector is a T-shaped device with _______ ports

 

       ► Three

 

       ► Two

 

       ► Four

 

       ► Five

 

 

 

Question No: 44      ( Marks: 1 ) – Please choose one

 

 

_________ is the access protocol used by traditional Ethernet.

 

       ► CSMA/CD

 

       ► CSMA/CA

 

       ► Token Ring

 

       ► CSMA

 

 

 

Question No: 45      ( Marks: 1 ) – Please choose one

 

 

When a collision is detected in a network using CSMA/CD. _________

 

       ► The frame is immediately resent

 

       ► A jam signal is sent by the station

 

       ► The backoff value is set to 0

 

       ► The backoff value is decremented by 1

 

 

 

Question No: 46      ( Marks: 1 ) – Please choose one

 

 

Like VRC, LRC and CRC, Checksum is also based on _______________.

 

       ► Redundency

 

       ► Decimal Division

 

       ► Encryption

 

       ► Encoding

 

 

 

Question No: 47      ( Marks: 1 ) – Please choose one

 

 

Check sum method is used for _______________ layers.

 

       ► Physical

 

       ► Application

 

       ► Transport

 

       ► Datalink

 

 

 

Question No: 48      ( Marks: 1 ) – Please choose one

 

 

Repeater works on __________     layer.

 

       ► Data Link

 

       ► Physical

 

       ► Network

 

       ► Application

 

 

 

Question No: 49      ( Marks: 1 ) – Please choose one

 

 

When systems share a point to point link, then protocols used are called ___________ protocols.

 

       ► Direct

 

       ► Indirect

 

       ► Monolithic

 

       ► structured

 

 

 

Question No: 50      ( Marks: 1 ) – Please choose one

 

 

_________ requires more bandwidth.

 

       ► FSK

 

       ► ASK

 

       ► PSK

 

       ► QAM

 

 

 

Question No: 51      ( Marks: 2 )

 

 

Whether Hamming code is the technique used for error detection or error correction?

 

 

Question No: 52      ( Marks: 2 )

 

 

What are Guard Bands in Multiplexing?

 

 

Question No: 53      ( Marks: 2 )

 

 

Which type of frames are present in BSC frames?

 

 

Question No: 54      ( Marks: 3 )

 

 

What are the fractional T Lines?

 

 

Question No: 55      ( Marks: 3 )

 

 

What are the light sources used for optic fiber?

 

 

Question No: 56      ( Marks: 3 )

 

 

Write names of Link Access Protocols developed by ITU-T?

 

 

Question No: 57      ( Marks: 5 )

 

 

 

Question No: 58      ( Marks: 5 )

 

 

What is Troposphere and Ionosphere?

 

 

Question No: 59      ( Marks: 10 )

 

 

What is CSMA/CD. Why it is needed?

 

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