3. COMPUTER NETWORK
Computer network consists of
two or more computers that are
connected together
to share information and resources.
The resources may include
• Printers
• Hard disks
• Programs etc.
Computers are connected through
communication media.
Communication media can be
Physical wire OR wireless connection.
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4. USES / BENEFITS OF
COMPUTER NETWORK
Networks are used to
• Access shared data
• Share different devices (such as printers , hard-disks )
• Send e-mail with attachments files.
• Communicate different people all over the world.
• One copy of software shared by multiple users.
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5. WORKGROUP COMPUTING
Workgroup:-
Is a group of persons working together
by sharing information through computer network.
Workgroup Computing:-
The process of
Sharing information
by using a computer network
is called workgroup computing.
It is also called collaborative computing.
Groupware:-
Is a software used for workgroup computing.
It is used on computer network.
Researchers use it to search information about projects online.
Individuals can use it to collaborate with friends and colleagues.
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6. SERVER/CLIENT COMPUTER
Server:-
Server is a computer.
that provide services
to computers and other devices
which connected to network.
Server is more powerful than other computers in network.
Different Services Provided are follows
• Control access to hardware, software and data.
• Centralized Storage for software , data & information.
• Processing Data
• Sharing Software
• Managing Network Traffic
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7. SERVER/CLIENT COMPUTER
Client :-
Client is a computer
in a network
that is connected to server
to access different resources.
Client computer sends request to server
for resources.
Server computer provides requested resource
to client computer.
Client computer is less powerful than server computer.
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8. NETWORKS MODELS
There are two models for computer networks.
1. Client-Server Model
2. Peer-to-Peer Model
1. Client-Server Model:-
In C-S Model
One or more computers work as server.
and other work as Clients.
At Server Side
Server computer controls whole network.
Server is used to store data and programs
to be shared among computers in network.
It may also share printer attached with it.
Server is more powerful than other computers in network.
Server performs most of processing.
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9. NETWORKS MODELS
1. Client-Server Model:-
At Client Side
Client computer requests a service from server computer.
Then
Server computer provide services to client computer.
Some servers are called dedicated servers.
Dedicated Server:-
Is used to perform a specific task.
E.g ( printer server is used to manage printers and printing tasks.)
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Advantages
Reduce the volume of data traffic on
network.
Provides Faster responses to clients.
It use less powerful client computer
because most processing done by
Server
Disadvantages
It is expensive model because
server computers are costly.
All operations stop all over network
when server goes down.
11. NETWORKS MODELS
2. Peer-to-Peer Model:-
All computers have same level in this model.
There is no server computer.
Each computer can have
access to devices and files on other computers.
Each computer independently store its own
software and information.
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Advantages
It is easy to setup.
It is easy to maintain.
It does not required expensive server
computer.
It is suitable for
small office of ten or less computer.
Disadvantages
Heavy use can slow down network
speed.
It provide less security of data
because
files are stored in different
locations.
12. NETWORK STANDARDS
Definition:-
The standards are documents that contain
technical and physical specifications about network
being designed.
Networks can reliable and efficient if
follows these standards.
-: Types :-
1. De Facto Standard
It means tradition or by Facts.
These standards designed without formal planning.
These standards come into existence due to historical developments.
These are still used in many organizations.
SNA is an example of De Facto standard.
2. De Jure Standard
De Jure means according to law or regulation.
These Standards are developed with
proper research
to fulfill requirement of data communication.
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14. NETWORK TOPOLOGIES
A network can be
Configured and arranged in different ways.
The physical layout or arrangement of
Connected devices in a network
is called network topology.
It is shape of network.
-: Types :-
1. Bus Topology
2. Ring Topology
3. Star Topology
4. Tree Topology
5. Mesh Topology 14
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15. BUS TOPOLOGY
It is simplest type of network.
It supports small number of computers.
In bus topology
All computers or network nodes are connected to
common communication medium.
This medium is a central wire known as bus.
Terminators are used at the end of bus
to absorb a signal.
A collision can occur in bus topology
if two computers transmit data at same time.
Bus topology is mostly used in peer-to-peer networks.
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16. Working of Bus Network:-
Sending computer sends
Data and destination address through the bus.
The data and address move from
One computer to other in a network.
Each computer checks the address.
If computer matches the address
Computer keeps the data.
Otherwise
Data moves to next computer.
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BUS TOPOLOGY
Advantages
1. It is simple and easy to use.
2. It requires small length of cable.
3. It is less expensive.
4. It is easy extend a bus.
5. It allows more computer to join.
6. If one node fails , it does not affect
the network.
Disadvantages
1. It is difficult to troubleshoot.
2. It only supports small number
of computers.
3. Network speed slows down
as the
Number of computers increases.
17. STAR TOPOLOGY
All computers in star topology are
Connected with central device
called hub or switch.
It is mostly used in client-server networks.
Working of Star Network:-
Sending computer sends data to
central device.
then
The central device sends data to
receiving computer.
Each computer communicates with central device. 17
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18. 18
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Advantages
1. It is easy to
maintain & modify.
2. Adding or removing computers
can be done without disturbing
the network.
3. Finding faults becomes very
simple.
4. Single computer failure does not
down the whole network.
5. It is more flexible than other
topologies.
Disadvantages
1. If central hub fails , network
breaks down.
2. It requires
large length of cable
to connect computers.
3. It is more expensive.
STAR TOPOLOGY
19. RING TOPOLOGY
In ring topology
each computer connected to next computer
&
last one connected to the first.
Thus ring of computers is formed.
Working Of Ring Topology:-
Every computer is connected to next computer.
Each computer receive message from
previous computer & then
transmits it to next computer .
The message flows in one direction.
Message is passed around the ring network until
it reaches the correct destination computer.
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20. 20
Advantages
1. It is less expensive than star
topology.
2. Every computer has equal access to
network.
Disadvantages
1. Failure of one computer can
affect the whole network.
2. It is difficult to troubleshoot
3. Adding or removing computers
affects the whole network.
RING TOPOLOGY
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21. TREE TOPOLOGY
Tree topology is combines characteristics of
Bus and Star topologies.
It consists of
Different groups of computers
attached in star topology.
The groups are then connected to
bus backbone cable.
It is used for expansion of existing network.
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Advantages
1. It provides
point-to-point wiring for
individual segments.
2. It is supported by several
software and hardware
vendors.
Disadvantages
22. ROUTERS
Router is a device
that connects
Multiple networks
using similar or different protocols.
It manages best route between
any two communication networks.
Routers are used
When several networks are connected together.
It can connect networks of different countries.
It transfer data in less time.
A router is an intelligent device because
it uses algorithms to find the best path to transfer data.
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23. GATEWAY
Gateway is a device
that connects
Two or more networks
with different types of protocols.
Two different types of networks
requires a gateway
to communicate each other.
It receives data from one network
and converts it according to
protocol of other network.
Example:-
Computers on LAN require gateway to access Internet.
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24. BRIDGES
A network bridge can be used in computer networks to
Interconnect
two LAN’s and to separate network segments.
A segment is a section of a network.
When a bridge receives a signal,
It determines the segment where the signal should be sent.
It reads the addresses of
sending and receiving computers.
The bridge does not pass the signal to other segment
if sending and receiving computers are both in same
segment.
it reduces network traffic and
increases network performance.
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25. LAN
LAN stands for local area network.
It is most common type of network.
It covers a small area.
It usually connects the
computers and other devices
within one office or in buildings.
LAN is often used as share resources such as
printers , hard disks and programs.
Data transfer speed:-
LAN can transmit data at very high speed.
Data transmission speed from 10 Mbps to 1000 Mbps.
It is much faster than data transmission over telephone lines.
LAN can transmit data in a limited distance.
There is also a limit on
number of computers can attached to LAN.
-:Example:-
Network in a computer lab of a college.
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26. USES AND ADVANTAGES OF LAN
One copy of software can be shared by all users
in a LAN.
System resources like
printers and hard disks can be shared
between users in LAN.
It is easy to manage the data stored on a
centralized computer in LAN.
The data is more secure from being copied or
destroyed.
Data can be shared by all users using LAN.
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27. DIFFERENT COMPONENTS OF A NETWORK
1. Communication Media:-
Communication media is used to transfer
data from one computer to another computer.
Low-cost LAN’s are connected with
twisted wire pair.
Many LAN’s use
coaxial or fiber-optic cables. (These cables are
expensive but provide faster communication)
Some LAN’s use wireless transmission media.
It uses infrared or radio ways to
connect computers.
Wireless networks are easy to setup and maintain.
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28. 2. Network Interface Card :-
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DIFFERENT COMPONENTS OF A NETWORK
29. 2. NIC :-
Stands for network interface card.
It is also known as LAN adapter.
It is used to connect a computer with network.
It is circuit board installed on mother board.
Now a day’s most computer system have
network card built into the mother board.
Each computer on network
must have network card.
Different types of network cards are available.
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DIFFERENT COMPONENTS OF A NETWORK
30. WAN (WIDE AREA NETWORK)
WAN stands for wide area network.
It covers a large area.
It usually connects the
computers and other devices
in different cities and countries.
WAN usually consists of
several LAN’s connected together.
Computers in WAN often connected with telephone
lines.
Also connected through leased line or satellite.
Data transfer speed:-
Data transmission speed from 56 Kbps to 50 Mbps.
WAN is expensive than LAN.
It is not fast as LAN.
Internet is the largest WAN in the world.
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31. WAN (WIDE AREA NETWORK)
Mainframe and minicomputers are used in WAN
are designed to be accessed by terminals.
A personal computer must appear as a terminal
to communicate with large computers in WAN.
Terminal emulation software is used to allow a PC
to appear as terminal.(In this way personal computer can connec
with larger computer).
Larger computer is known as host computer.
A personal computer attached to host computer
to upload and download data.
Uploading:- (Transfer of data from PC to HC )
Downloading:- (Transfer of data from HC to PC )
File transfer software is used to upload and download data.
-:EXAMPLES:-
Network connecting ATM’s of bank located in different cities.
Network connecting NADRA offices in different cities in Pakistan.
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32. MAN (METROPOLITAN-AREA NETWORK)
MAN stands for metropolitan-area network.
It covers an area of a city.
MAN is larger than LAN but
smaller than WAN.
It usually used to connect two or more LAN’s
in a city or town.
-: Examples:-
Network connecting different branches of company in same city.
Cable TV network in a city.
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Advantages
MAN covers a larger area
than LAN.
It provide higher speed than
LAN.
Disadvantages
It is more expensive than
LAN.
It is difficult to maintain than
LAN.
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34. NETWORK PROTOCOL
Network protocol or communication protocol
is a set of rules
for exchanging information between computers on
network.
The devices in a network cannot communicate without a
protocol.
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35. TYPES OF NETWORK PROTOCOL
Different LAN protocols are follows:
1. Ethernet
2. Token Ring
3. ARCnet 35
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36. TYPES OF NETWORK PROTOCOL
1. Ethernet:-
Ethernet is most commonly used LAN protocol.
It uses a
high speed network cable
&
bus topology.
It is inexpensive easy to install and manage.
All computers in Ethernet
uses same cable to send and receive data.
They must follow same rules for communication.
If two or more computers sends data at same time
the messages can be lost.
A computer checks the cable before transmitting data.
* Computer waits if cable is being used.
* Computer starts transmitting data when cable is free.
This process is also called CSMA/CD.
Data transfer speed is 10 Mbps to 100 Gbps.
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37. TYPES OF NETWORK PROTOCOL
3. ARCnet:-
ARCnet stands for Attached Resource Computer network.
It is a LAN protocol.
It was introduced in 1977.
It uses twisted-pair, coaxial cable and fiber-optic media.
ARCnet uses
star , bus or combination of these topologies.
Original ARCnet was very slow.
Data transfer speed 2.5 Mbps.
It became popular because it was
inexpensive and reliable.
It is also easy to setup and expand.
Fast ARCnet provide speed 100 Mbps.
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39. TYPES OF NETWORK PROTOCOL
2. Token Ring:-
Is a network standard that is used in LAN.
It allows network devices to access network
by passing special signal called token.
Token is like ticket.
A device can transmit data over network if
it has token.
Only one token is available in one network.
That’s why no collision is occur. (But transmission is slow)
When a computer wants to send message, it
1. Gets the token
2. Puts the data in token
3. Adds the address of receiving computer
Token ring is based on
ring topology & also can be used star topology
The token passes from computer to computer.
The computer whose address matches gets the data
It returns message to sending computer
& indicate that data has been received.
Data transfer speed from 4 Mbps to 1 Gbps.
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40. TCP/IP
TCP/IP stands for transmission control protocol/ Internet
protocol.
It is most widely used communications protocol today.
It is used to transfer data over Internet.
It consists of two protocols
TCP ( is responsible for the delivery of data)
IP ( provides addresses and routing information)
TCP/IP uses packet switching to transmit data.
In this process
Data is divided into small pieces called packets
and transferred over internet.
The packets are reassembled (decoded)
when they reach destination.
These packets travel via devices called routers.
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41. VARIOUS LINES FOR COMMUNICATION
1. ISDN:
ISDN stands for Integrated Services Digital Network.
It
Provides faster transfer rates than dial-up telephone lines
for small business and home user.
is a set of standards
for digital transmission of data
over standard telephone lines.
One telephone line can carry three or more signals
at one time using same line.
Its data transfer rate up to 1.54 Mbps.
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42. VARIOUS LINES FOR COMMUNICATION
2. DSL:
DSL stands for Digital Subscriber Line.
It uses standard telephone line for fast speed data transmission
DSL easy to install and provides
high data transfer rate than ISDN.
The user needs to connect to a DSL
with (ISP) Internet Services Provider
to use the internet.
It provide transfer rate 128 Kbps to 10 Mbps.
It allows the user to use phone and Internet at same time.
DSL works better when user close to ISP office.
DSL most widely used in small business and home user.
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43. DIFFERENT METHODS OF ETHERNET TO ACCESS
NETWORK
1. CSMA / CD:
It is local area access method.
It resolves the contention
between two or more stations by collision detection.
If two stations transmit data at same time
they both stop and generate signal
(collision has occurred )
Each station waits and retransmit signal.
2. CSMA / CS:
In this
Node listens to bus for specific number of time
before transmitting.
It waits until the node has completed the transmission.
3. CSMA / CR:
It allows multiple devices to talk at same time.
A protocol is used to determine the
priority of a device.
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44. WHAT IS INTERNET?
Internet is a large collection of computers
all over the world
that are connected to one another.
It is global network of computers.
These computers connected through different links like
i. Phone Lines
ii. Fiber Optics Lines
iii. Satellites and wireless connection
Internet is used to find information which
Stored on computers called hosts or servers.
These computers used common protocol called TCP/IP.
Each computer connected to internet act as a host.
A host computer provides information to people.
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45. HISTORY OF INTERNET?
Work started in 1960’s.
( War of Russia and America)
Four computers network.
DARPA. (Defense Advanced Research Project Agency)
Different universities and researchers started
development of own network.
1989 all previous network replaced by
NSFNET of National Science Foundation.
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46. SERVICES OF INTERNET
1. World wide web
2. E-mail
3. Telnet
4. File Transfer Protocol (FTP)
5. Gopher
6. Chat Groups
7. Intranet
8. Extranet
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47. SERVICES OF INTERNET
1. World wide web:-
WWW is a collection of millions of websites.
A website contains
different web pages containing information.
www organizes this information such a way that
users can easily search and access information.
2. Email:-
Email stands for electronic mail.
Email is
Exchange of messages and files using internet.
Message can be graphics , sounds video clips etc.
It is fast way of sending messages
anywhere in the world in very short time.
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48. SERVICES OF INTERNET
3. Telnet:-
Is a program that is used to connect
to remote computer on internet.
A computer can act like a terminal
directly connect to remote computer.
It allows the user to logon to remote computer.
User can logon to computer and use it as
if he is connected computer directly.
4. File Transfer Protocol (FTP):-
Is used to transfer files over internet.
Audio , video , graphics and data files
can be uploaded or downloaded using FTP.
Downloading (Process of transferring file from remote
computer to local computer)
Uploading (Process of transferring file from local computer
to remote computer)
CuteFTP and WS_FTP are examples of FTP software.
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49. SERVICES OF INTERNET
5. Gopher:-
Is a menu based system
for exploring the internet and its resources.
It provides the facility of
Search and file retrieval on internet.
It organizes resources such a way that
finding becomes easier on internet.
6. Chat Groups:-
Chatting is a process of
exchanging views on internet using chat groups.
Chat group is a group of users with similar interest.
The user can interact with
one another in real-time.
It means they are online at same time.
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50. SERVICES OF INTERNET
7. Intranet:-
Is a private and secure business network.
It uses
internet technology
to provide information to employees of organization.
The information can be protected from unauthorized users.
It is designed to meet internal needs for sharing information
within a single organization.
8. Extranet:-
Is a collection of two or more intranets.
It can be accessed by authorized users
From outside the organization.
Different organizations can use extranet
Share information
of their intranets.
An organization can apply security measures to
provide limited access to extranet.
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51. E-MAIL
2. Email:-
Email stands for electronic mail.
Email is
Exchange of messages and files using internet.
Message can be graphics , sounds video clips etc.
It is fast way of sending messages
anywhere in the world in very short time.
Sender and receiver may be sitting in
same building or anywhere in world.
One email message can sent to many people.
Email facility is provided by many ISP’s or
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52. ADVANTAGES OF E-MAIL
E-mail is very fast and timely.
It is very cheap and inexpensive.
People can send and receive messages
anywhere in the world.
People can share information.
It is possible to send and receive email
through mobile phones.
Email gives us the facility to send
pictures , sounds and videos.
Email messages does not disturb the
recipient.
It can be stored on server and can be read at
any time.
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53. HTTP
HTTP stands for Hyper Text Transfer Protocol.
It is communication protocol used to connect
to server on world wide web.
Primary function of HTTP is
establish a connection
with web server and transmit HTML pages
to user’s browser
It allows computer users to
access the internet.
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54. OSI MODEL
OSI stands for Open System Interconnection.
An open system is a model
that allows two systems to communicate
even if their architectures are different.
OSI model was developed by
International Standards Organization (ISO) in 1983.
It provides
logical frame work for data communication
processes to interact across networks.
The standards were created for computer industry
to allow different networks to work together.
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55. OSI MODEL
OSI model consists of seven layers.
Each layer perform specific function in network.
Layers divided into two groups
1. Upper Layer
i. Focus on user applications
ii. How files are represented on computers
2. Lower Layer
i. How communication across network actually
occurs.
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57. OSI MODEL
-:Layers of OSI Model:-
7. Application Layer
6. Presentation Layer
5. Session Layer
4. Transport Layer
3. Network Layer
2. Data Link Layer
1. Physical Layer
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59. APPLICATION LAYER
Top most layer of OSI model.
Service direct to user application
It provide user interfaces
It perform basic 3 functions
(i). File Transfer
(ii). Mail Services
(iii). Directory Services
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60. APPLICATION LAYER
Is the top-most layer of OSI model.
It provides services directly to user applications.
It enables/allows the user to access the network.
It provides user interfaces.
It support for services such as
email, remote file access and transfer, shared database
and other distributed information services.
1.File Transfer :- It allows the user to
Access , retrieve and manage files in a remote
computer.
2. Mail Service:- It provides the basis for
email forwarding & storage facilities.
3. Directory Services:- it provides
Distributes database sources
access for global information
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61. PRESENTATION LAYER
It perform three basic functions.
1. Data Reformatting.
2. Encryption.
3. Compression.
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Bit Stream Changed
Encoding Techniques apply
Change data according to
Sender’s Format.
Change data according to
Receiver's Format.
Sender Transform Original
information into another form.
Receiver again Transform into
original form.
62. SESSION LAYER
It perform two major function.
1. User Connections are
2. Synchronization.
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Establishes
Manages
Terminates
Use of Check points
If failure occurs (data send from last check point)
If 1000 pages want to send
check point after 100 pages
Error at page 320.
The pages from 301 will be retransmitted.
63. TRANSPORT LAYER
Control the flow of data
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Ensure message delivered error free.
Divides large message into Small
packets
Packets are
* reassembled
* checked for errors
* acknowledgment
* retransmit
64. NETWORK LAYER
It perform two major function.
1. Network Connections are
2. Manages delivery of data.
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Establishes
Manages
Terminates
Determine Logical path
May be many networks between S & R.
Manages send data from S to D.
65. DATA LINK LAYER
Is Responsible for
establish physical link with Layer 1.
It must decide
1. Framing
2. Flow Control
3. Error Control
4. Access Control
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Divides stream of bits into
manageable data
If rate of sending data more
than receiving data.
Imposes flow control
Detects and retransmit
damaged or lost frames
Prevent duplication of frames.
Determine
which device
has control over
the link.
66. PHYSICAL LAYER
Bottom layer of OSI model.
Transmit stream of bits.
Define (how the data transmit)
(what control signals are used)
Main function ( How the stream of bit send and receive)
1. Framing
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If rate of sending data more
than receiving data.
Imposes flow control
