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All computer network Interview Questions
61.What are the advantages of fiber optics cable ?
Ans: The advantages of fiber optics cable over twisted pair cable are Noise resistance-As they use light so external noise is not a factor. Less signal attenuation-fiber optics transmission distance is significantly greater than that of other guided media.Higher bandwidth-It can support higher bandwidth.
62.What are the disadvantages of fiber optics cable?
Ans: The disadvantages of fiber optics cable over twisted pair cable are
Cost-It is expensive Installation/maintenance-Any roughness or cracking defuses light and alters the signal Fragility-It is more fragile.
63.What are the propagation type of radio wave ?
Ans: Radio wave propagation is dependent upon frequency.There are five propagation type.
i)surface propagation
ii)Tropospheric propagation
iii)Ionospheric propagation
iv)Line of sight propagation
v)space propagation
64.What do you mean by Geosynchronous Satellites ?
Ans: Satellite communication uses a satellite in geosynchronous orbit to relay signals.The Satellite must move at the same speed as the earth so that it seems to remain fixed above a certain spot..Only one orbit can be geosynchronous.This orbit occurs at the equatorial plane and is approximately 22,000 miles from the surface of earth.
65.What are the factors for evaluating the suitability of the media ?
Ans: The factors are cost,throughput,attenuation,Electromagneric interference(EMI),securtty.
66.What do you mean by medium access control(MAC) sublayer.
Ans: The protocols used to determine who goes next on a multi-access channel belong to a sublayer of the data link layer is called the multi-access channel(MAC) sublayer.It is the buttom part of data link layer.
67.What do you mean by ALOHA ?
Ans: It is the method used to solve the channel allocation problem .It is used for:
i)ground based radio broadcasting
ii)In a network in which uncoordinated users are competing for the use of single channel.
It is of two types:
1.Pure aloha
2.Slotted aloha
68.What is pure ALOHA?
Ans: It lets users transmit whenever they have data to sent.Collision may occur but due to feedback property sender can know the status of message.conflict occur when at one time more bits are transmitted.The assumptions are :
i)all frame size is same for all user.
ii)collision occur when frames are transmitted simultaneously
iii)indefinite population of no of user.
iv)N=number of frames/frame time
iv)it obeys poisson’s distribution if N>1 there will be collision 0<1
69.What is slotted ALOHA?
Ans: In this method time is divided into discrete intervals,each interval corresponding to one frame.It requires user to agree on slot boundaries.Here data is not send at any time instead it wait for beginning of the next slot.Thus pure ALOHA is tuened into discrete one.
70.What do you mean by persistent CSMA(carrier sense multiple access) ?
Ans: When a station has data to send,it first listens to the channel to see if anyone else is transmitting at that moment.If channel is busy it waits until the station becomes idle. When collision occurs it waits and then sends.It sends frame with probability 1 when channel is idle.
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