
4. Mention the common name of the computers connected in a Network?
Workstation / Nodes / Clients
Server
5. Define Server
The master computer is known as server
6. Define Client
Computer attached to the master computer is known as client
7. Draw the diagram of Network


Page 2

8. What is NIC?


It is a device attached to each client and server.
Helps to make connections within the network.
Each NIU has a unique number identifying it called Node Address.
NIU is also called Terminal Access Point (TAP).
Each NIC is given a unique physical address called MAC address.
9. Give the Expansion of NIC, MAC and TAP
NIC – Network Interface Card
MAC – Machine Access Code
TAP – Terminal Access Point
10. The computer on the network may be linked through ____________?
Cables
Telephone Lines
Radio Waves
Satellites
Infrared Light Beams.


Page 3

Lecture #2 Network Components


1. What are the components needed for building a Network?
Network Interface Card
Repeaters
Network Hub
Network Bridge
Network Switch
Router
2. Define Repeaters
A repeater is an electronic device that receives a low power signal and
retransmits it at a higher power level
Repeaters are required for cable runs longer than 100 meters.

3. Define Hub
A hub contains multiple ports.
When a packet arrives at one port, it is copied unmodified to all ports of
the hub for transmission.


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4. Define Switch


A switch is a device that forwards and filters datagram's between ports
Switches work at Physical, Data link, Network, or Transport Layers

5. Define Multilayer Switch
A device that operates simultaneously at more than one layer is called a multilayer
switch.
6. Define Router
Router is a specialized network device used to interconnect different
types of computer network that uses different protocols
Routers work at the network layer
7. Define Bridge
A network bridge connects two LANS having same protocol.


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8. What are the available types of Bridge?


Local Bridge
Remote Bridge
Wireless Bridge

9. What is the use of Local Bridge?
It is used to connect directly local area networks (LANs).
10. What is the use of Remote Bridge?
It can be used to create a wide area network (WAN) link between LANs
11. What is the use of Wireless Bridge?
It can be used to connect remote stations to LANs.


Page 3


Lecture #3 Network Topology
1. Define Topology.

The way in which the computers are interconnected together is known as TOPOLOGY
2. What are the types of Network Topology?
1. Physical Topology – How the cable are used
2. Logical Topology – How the messages travel
3. What are the types of Physical Topology?
Bus / Linear

-

Both Physical and Logical

Ring

_


Star

-

Physical

Tree

-


Mesh

-


4. Draw the diagram of Bus Topology?


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5. Draw the diagram of Ring Topology?


6. Draw the diagram of Star Topology?


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7. Draw the diagram of Mess Topology


7. Draw the diagram of Tree Topology


Page 3

8. Explain Bus Topology


9. Explain Ring Topology


Page 4

10. Explain Star Topology


11. Explain Mess Topology


Page 5

Lecture #4 OSI Reference Model


1. What is the Expansion of OSI
Open System Interconnection
2. What is OSI?
An open system is a set of protocol that allows any two different systems to
communicate regardless of their underlying architectures.
It was designed by ISO-International Organization for Standardization in
late1970s.
It is a seven-layer model.
3. What are the types of layers in OSI?
Physical Layer
Data Link Layer
Network Layer
Transport Layer
Session Layer
Presentation Layer
Application Layer
Physical Layer
The physical layer is responsible for transmitting bits from one node to the next
Data Link layer
The data link layer is responsible for transmitting frames from one node to the next

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Network Layer


The network layer is responsible for the delivery of packets from the original source to
the final destination
Transport Layer
The transport layer is responsible for delivery of a message from one process to
another (process-to-process delivery)
Session Layer
The session layer is the network dialog controller. It establishes, maintains, and
synchronizes the interaction between communicating systems
Presentation Layer
The presentation layer is concerned with the syntax and semantics of the information
exchanged between two systems
Application Layer
The application layer enables the user to access the network. It provides user interfaces
and support for services


Page 2

4. Draw the diagram of OSI Model


Page 3

Lecture #5 Data Transmission Modes


Definition:
Data transmission is the physical transfer of data (a digital bit stream) over a point-to-point or
point-to-multipoint communication channel. Communication channel is any physical media like
cables etc.

Transmission Modes:

Data transmission has been categorized into two type’s namely Parallel and Serial Transmission.
Serial transmission is further classified into Synchronous and Asynchronous Transmission.

Parallel Transmission:
1. In parallel transmission of data, all the bits of a byte are transmitted simultaneously on
separate wires.
2. This type requires multiple circuits for interconnecting the two devices.
3. It is practically possible only if two devices are close to each other.
4. This diagram represents parallel transmission of an 8-bit digital data.
5. This will require 8 wires for connecting two devices.


Page 1


Advantages of Parallel transmission:
1. All the data bits will be transmitted simultaneously, so time required for transmission of N
number of bits will be only one clock cycle.
2. Due to transmission in only one clock cycle, clock frequency can be kept low without affecting
speed of operation.

Disadvantages of Parallel transmission:
1. Transmission of N bits will require N number of wires.
2. With increase of users these wires will be too many to handle.

Serial Transmission:
1. In serial transmission of data, all the bits of a byte are transmitted serially one after the other on
same wire.
2. This type doesn’t require multiple circuits for interconnecting the two devices, indeed it just
requires 1 wire to connect.
3. It is practically possible in all sorts of situations close or far.
4. This diagram represents serial transmission of an 8-bit digital data.
5. This will require only one wire for connecting two devices.


Page 2


Advantages of serial transmission:
1.

Only one wire is required.

2.

Reduced cost due to less number of conductors.

Disadvantages of serial transmission:
1.

Speed of data transfer is low.

2.

To increase speed of data transfer, clock frequency needs to be increased.

Types of Serial Transmission:
In data communication, Timing control of the reception of bits is important.
There are two methods of timing control for reception of bits.

Asynchronous Data Transfer
1.

In asynchronous transmission, the transmitter transmits data bytes at any instant
of time.

2.

Only one byte is sent at a time. There is ideal time between two data bytes.

3.

Transmitter and Receiver operate at different clock frequencies.

4.

To help receiver ‘start’ and ‘stop’ bits are used along with data in middle.

5.

Ideal time between byte is not constant. They are also known as gaps.

6.

In asynchronous transmission timing of signal is not important.


Page 3


Advantages of asynchronous transmission:
1. Synch between devices is not necessary.
2. It is cheap scheme.

Disadvantages of synchronous transmission:
1. Use of ‘start’ and ‘stop’ bits and gaps between data makes transmission slow.
2. Timing error can take place.

Synchronous Data Transmission

1. In synchronous transmission, data transmission is carried out under the control
of a common master clock.
2. Bytes are transmitted as a block in a continuous stream of bits.
3. Transmitter and Receiver operate at synchronized clock frequencies.
4. No ‘start’ and ‘stop’ bits are used.
5. No need of ideal time between data bytes.
6. In synchronous transmission timing of signal is important.


Page 4


Advantages of asynchronous transmission:
1. Speed of data is much higher because of no ‘start’ and ‘stop’ bits and continuity.
2. Timing errors are reduced due to synch.

Disadvantages of synchronous transmission:
1. Accuracy of data is entirely dependent on timing.
2. Transmitter and Receiver needs to be properly synchronized.


Page 5

Lecture #6 Data Transmission Media


I. Introduction


On any network, the various entities must communicate through some form of media.



Just as humans can communicate through telephone wires or sound waves in the air,
computers can communicate through cables, light, and radio waves.



Communication is possible only if information is encoded in a signal, and the signal is carried
on a transmission the characteristics of the signal and of the medium both determine the
quality of the communication medium.



There are two main groups of transmission media, namely the Guided Medium and the
Wireless Medium / Unguided Medium.



For the guided medium, there is a physical path (such as a cable) for electromagnetic wave
propagation.



For the wireless medium, however, the electromagnetic wave is transmitted through air,
water, or vacuum.

II. Characteristics


A good transmission medium should provide communication with good quality at long
distance.



For voice communication, quality of communication is determined by the voice quality.



For data communication, however, the quality of communication is mainly determined by the
effective data rate of communication.

III. Factors Affecting Data Communication of a Medium


Communication bandwidth of the medium



Interference



The transmission impairments



The bandwidth of a medium determines the signal frequencies that can be carried in the
medium.


Page 1

IV. Reasons for Transmission Impairence


Attenuation



Distortion during signal propagation




Noises

V. Design Factors for Transmission Media
Bandwidth: All other factors remaining constant, the greater the band-width of a signal, the
higher the data rate that can be achieved.
Transmission impairments: Limit the distance a signal can travel.
Interference: Competing signals in overlapping frequency bands can distort or wipe out a
signal.
Number of receivers: Each attachment introduces some attenuation and distortion, limiting
distance and/or data rate.

TYPES OF TRANSMISSION MEDIA
1. Guided Media :
Use a conductor such as a wire or a fiber optic cable to move the signal from sender to
receiver.
2. Wireless or Unguided Media:
Use radio waves of different frequencies and do not need a wire or cable conductor to transmit
signals.

Guided Transmission Media
Guided media includes everything that ‘guides’ the transmission. That usually takes the form
of some sort of a wire. Usually copper, but can also be an optical fiber
Transmission capacity depends on the distance and on whether the medium is point-to-point
or multipoint
Examples:

Page 2

o Twisted Pair Wires


o Coaxial Cables
o Fiber Optical Cable

A. Twisted Pair Wires
A transmission medium consisting of pairs of twisted copper wires arranged in a regular spiral
pattern to minimize the electromagnetic interference between adjacent pairs
Often used at customer facilities and also over distances to carry voice as well as data
communications
Low frequency transmission medium
We can transmit 1 Mbps over short distances (less than 100m).
They are mainly used to transmit analog signals, but they can be used for digital signals.

Twisted Pair Advantages
Inexpensive and readily available
Flexible and light weight
Easy to work with and install

Page 3

Twisted Pair Disadvantages
Susceptibility to interference and noise


Attenuation problem
 For analog, repeaters needed every 5-6km
 For digital, repeaters needed every 2-3km
Relatively low bandwidth (3000Hz)
Applications
They are used in telephone lines to provide voice and data channels.
Local area networks, such as 10 Base-T and 100 Base-T also use twisted-pair cables.

B. Coaxial Cable (or Coax)
In its simplest form, coaxial consists of a core made of solid copper surrounded by insulation,
a braided metal shielding, and an outer cover.
A transmission medium consisting of thickly insulated copper wire, which can transmit a
large volume of data than twisted wire.
Coax Advantages
Higher bandwidth
 400 to 600Mhz
 up to 10,800 voice conversations
Much less susceptible to interference than twisted pair
Coax Disadvantages
High attenuation rate makes it expensive over long distance
Bulky


Page 4


Applications
 It is used in cable TV networks
 It is used in traditional Ethernet LANs.

C. Fiber Optic Cable
Relatively new transmission medium used by telephone companies in place of long-distance
trunk lines
Also used by private companies in implementing local data communications networks
Require a light source with injection laser diode (ILD) or light-emitting diodes (LED)
Optical fiber consists of a glass core, surrounded by a glass cladding with slightly lower
refractive index.
In most networks fiber-optic cable is used as the high-speed backbone, and twisted wire and
coaxial cable are used to connect the backbone to individual devices.
Fiber Optic Advantages
Greater capacity (bandwidth of up to 2 Gbps).
Smaller size and lighter weight.

Page 5

Lower attenuation.


immunity to environmental interference.
highly secure due to tap difficulty and lack of signal radiation.
Fiber Optic Disadvantages
expensive over short distance
requires highly skilled installers
adding additional nodes is difficult

Applications
The fiber optic cable is often found in backbone networks because its bandwidth is cost
effective.
Used in TV companies.
LAN such as 100 Base-FX Network


Page 6


Wireless (Unguided Media) Transmission
Transmission and reception are achieved by means of an antenna
Directional
 Transmitting antenna puts out focused beam
 Transmitter and receiver must be aligned
Omni directional
 Signal spreads out in all directions
 Can be received by many antennas
Wireless Examples
Terrestrial Microwave
Satellite Microwave
Broadcast Radio
Infrared

A. Microwaves
Electromagnetic waves having frequency between 1 and 300 GHz are called as Micro waves.
Micro waves are unidirectional.
Microwave propagation is line of sight.
Very high frequency Micro waves cannot penetrate walls.
The microwave band is relatively wide, almost 299 GHz
Terrestrial Microwave


Page 7

Used for long-distance telephone service.


Uses radio frequency spectrum, from 2 to 40 Ghz.
Parabolic dish transmitter, mounted high.
Used by common carriers as well as private networks.
Requires unobstructed line of sight between source and receiver.
Curvature of the earth requires stations (repeaters) ~30 miles apart.

B. Satellite Microwave
A microwave relay station in space
Can relay signals over long distances
Geostationary satellites
 Remain above the equator at a height of 22,300 miles (geosynchronous orbit)
 Travel around the earth in exactly the time the earth takes to rotate
Applications
They are used in Cellular phones.
They are used in satellite networks.
They are used in wireless LANs.


Page 8

C. Radio
Radio waves particularly those waves that

propagate in the sky mode , can travel long

distances .This makes Radio waves a good candidate for long distance broadcasting such as
AM Radio
Radio is a general term often used to encompass frequencies in the range 3 kHz to 300 GHz.
Mobile telephony occupies several frequency bands just under 1 GHz.
Radio waves are Omni directional.
Application
The omnidirectional characteristics of Radio waves make them useful for multicasting, in
which there is one sender but many receivers.
AM and FM Radio, television, maritime radio, cordless phone, and paging are examples of
multicasting.

D. Infrared
Infrared waves, with frequencies from 300GHz-400THz can be used for short range
communication.
When we use our Infrared control, we do not interfere with use of the remote by our
neighbors.
We cannot use Infrared waves outside a building because the sun rays Contain Infrared waves
that can interfere with communication.
Uses transmitters/receivers (transceivers) that modulate no coherent infrared light.
Transceivers must be within line of sight of each other (directly or via reflection).
Unlike microwaves, infrared does not penetrate wallshaving high frequencies.

Page 9

Application


The infrared band almost 400 THz has an excellent potential for data transmission.

Such a wide bandwidth can be used to transmit digital data with a very high data rate.
Infrared waves are used in communication between devices such as Keyboard, PCs and
Printers.


Page 10

Lecture #7 Data Encryption


I. Definition
Encryption is the process of transforming information (referred to as Plaintext) using an algorithm
(called Cipher) to make it unreadable to anyone except those possessing special knowledge, usually
referred to as a Key.
The result of the process is encrypted information (in cryptography, referred to as cipher text).
Decryption is the process to make the encrypted information readable again


Page 1


II. Process diagram of Encryption
Plain Text

Key

Cyber Text

Process diagram of Decryption

Cyber Text

Key

Plain Text

III. Types of Encryption
1. Manual Encryption
2. Transparent Encryption
3. Symmetric Encryption
4. Asymmetric Encryption

IV. Methods of Encryption
1. Stream Encryption
-

Plain text encrypted character by character

2. Block Cyber Encryption
-

Plain text encrypted block by block

V. Uses of Encryption
1. Protect information on your computer
2. Protect information over network transmission
3. Wireless Phones
4. E-Mail Programs
5. Digital Signature
6. Confidentiality of medical, personal and bank transaction records


Page 2

Lecture #8 Internet Service Providers


1. Define ISP
A specialized company that connects customers with PCs and browsers to the Internet
The ISP gives you a software package, a user name and password, and an access phone number to connect to the Internet
for the payment.

2. What are the types of Service Providers?
Internet Service Provider (ISP)
Application Service Provider (ASP)
Business Service Provider (BSP)
Wholesale Service Provider (WSP)
Wireless Application Service provider (WASP
3. What are the types of Web Hosting Services?
1. Dial-Up Access
2. Developer’s Hosting
3. Industrial Strength Hosting
4. What are the 3 major target markets of ISP?
1. Residential
2. Commercial
3. Public
5. What is meant by DNS (Domain Name Service)?
A repository where the domain name for each ISP is stored
6. What are the services provided by ISP?
WWW Server
FTP
Internet Relay Chat (IRC)
News Server
HTTP Proxy Service
Broadband Connection
Local Loop


Page 1

Lecture #9Packet Switching


1. Define Packet Switching
•

Packet Switching refers to technologies in which messages are divided into packets before
they are sent.

•

Each packet is then transmitted individually and can even follow different routes to its
destination

•

Once all the packets forming a message arrive at the destination, they are recompiled into their
original form

2. What are the types in Packet Switching?

TCP/IP
X.25
Frame Relay
3. Draw the diagram of TCP/IP

4. Define X.25

•

X.25 is an open standard WAN technology for packet-switching networks.

•

It is one of the earliest international standards for packet switching.

•

It defines layers 1, 2, and 3 in the OSI Reference Model

5. Define Frame Relay

•

Frame Relay is a packet-switching protocol for connecting devices on a WAN.

•

It operates at layer two or the Data Link layer in the OSI model.

•

It is used in applications such as LAN interconnection, public and private wide area networks
and gradually replacing X.25


Page 1

Computer Network PDF - Course Material 2013

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