1.What is HDLC?
Ans: It is a bit oriented data link protocol designed to support both half duplex and full duplex
communication over point to point and multi point links.HDLC is characterized by their station
type,configuration and their response modes.
2.What do you mean by point to point protocol?
Ans: The point to point protocol was designed to provide a dedicated line for users who need
internet access via a telephone line or a cable TV connection. Its connection goes through three
phases: idle, establishing, authenticating, networking and terminating.
At data link layer it employs a version of HDLC.
3. What do you mean by point to point protocol stack?
Ans: Point to point protocol uses a stack of other protocol to use the link, to authenticate the
parties involved, and to carry the network layer data. Three sets of protocols are defined: link
control protocol, Authentication protocol, and network control protocol.
4.What do you mean by line control protocol?
Ans: It is responsible for establishing, maintaining, configuring, and terminating links.
55.What do you mean by Authentication protocol?
Ans: Authentication means validating the identity of a user who needs to access a set of
It is of two types
i)Password Authentication Protocol(PAP)
ii)Challenge Handshake Authentication Protocol(CHAP)
PAP is a two step process. The user sends a authentication identification and a password. The
system determines the validity of the Information sent.CHAP is a three step process. The system
sends a value to the user. The user manipulates the value and sends the result. The system
Verifies the result.
5.What do you mean by network control protocol?
Ans: Network control protocol is a set of protocols to allow the encapsulation of data coming
from network layer protocol that requires the services of PPP.
6. What do you mean by CSMA?
Ans: To reduce the possibility of collision CSMA method was developed. In CSMA each station
first listen to the medium (Or check the state of the medium) before sending. It can’t eliminate
7.What do you mean by Bluetooth?
Ans: It is a wireless LAN technology designed to connect devices of different functions such as
telephones, notebooks, computers, cameras, printers and so on. Bluetooth LAN Is an adhoc
network that is the network is formed spontaneously? It is the implementation of protocol
defined by the IEEE 802.15 standard.
8.What is IP address?
Ans: The internet address (IP address) is 32bits that uniquely and universally defines a host or
router on the internet.
The portion of the IP address that identifies the network is called netid. The portion of the IP
address that identifies the host or router on the network is called hostid.
9.What do you mean by subnetting?
Ans: Subnetting divides one large network into several smaller ones. It adds an intermediate
level of hierarchy in IP addressing.
10.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
12.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.
13.What are the propagation type of radio wave ?
Ans: Radio wave propagation is dependent upon frequency.There are five propagation type.
iv)Line of sight propagation
14.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.
15.What are the factors for evaluating the suitability of the media ?
Ans: The factors are cost,throughput,attenuation,Electromagneric interference(EMI),securtty.
16.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.
17.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:
18.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
19.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.
20.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.