UNIT-1
1 Computer network
A computer network is a set of devices connected through links. A node can be computer, printer, or any
other device capable of sending or receiving the data. The links connecting the nodes are known as
communication channels.Computer Network uses distributed processing in which task is divided among
several computers. Instead, a single computer handles an entire task, each separate computer handles a
subset.
o Computer Network is a group of computers connected with each other through wires, optical
fibres or optical links so that various devices can interact with each other through a network.
o The aim of the computer network is the sharing of resources among various devices.
o In the case of computer network technology, there are several types of networks that vary from
simple to complex level.
Goals of Computer Networks: The following are some important goals of computer networks:
Resource Sharing – Many organization has a substantial number of computers in operations,
which are located apart. Ex. A group of office workers can share a common printer, fax,
modem, scanner, etc.
High Reliability – If there are alternate sources of supply, all files could be replicated on two
or more machines. If one of them is not available, due to hardware failure, the other copies
could be used.
Inter-process Communication – Network users, located geographically apart, may converse
in an interactive session through the network. In order to permit this, the network must
provide almost error-free communications.
Flexible access – Files can be accessed from any computer in the network. The project can
be begun on one computer and finished on another.
Other goals include Distribution of processing functions, Centralized management, and
allocation of network resources, Compatibility of dissimilar equipment and software, Good
network performance, Scalability, Saving money, Access to remote information, Person to
person communication, etc.
Saving Money- The second goal of a computer network is saving money. Small computers
have a much excellent value proportion than higher ones. Mainframes are approximately a
method ten times quicker than the quickest single-chip microprocessors, but they cost a huge
number of times more.
Improve Performance- The fourth goal of a computer network is to improve accessibility and
the performance of the system. A system’s performance can be improved by inserting one or
more processors into it as its workload grows.
Communication Medium-The computer network offers a powerful communication medium.
The different user on the network can immediately identify a document that has been refreshed
on a network.
Application of computer network: Some of the network applications in different field are the following:
Marketing and sales– Computer networks are widely used in both marketing sales firms. These
are used by marketing professionals to collect, exchange, and analyzes data relating to
customer requirements and product development cycles. Teleshopping is also important part of
sales applications that use order-entry computers or telephones connected to an order-
processing network, and on-line reservation services for hotels airline and so on.
, Manufacturing– Now days, computer networks are used in a several aspects of manufacturing,
including the manufacturing process itself. Two applications which use a network to provide
necessary services are computer-assisted manufacturing (CAM) and computer –assisted
designing (CAD) both of which permit multiple users to work on a project simultaneously.
Financial Services– In Present, Financial services are completely dependent on computer
networks. Main applications are credit history searches, foreign exchange and investment
services, and Electronic Funds Transfer (EFT) that permits a user to transfer money without
going into bank.
Teleconferencing– With The help of teleconferencing conferences are possible to occur without
the participants being in the same place. Applications include simple text conferencing, voice
conferencing, and video conferencing.
Cable Television- Future Services provided by cable television network can include video on
request, as well as the same information, financial and communications services currently
provided by the telephone companies and computer networks.
Information Services- Network information services include bulletin boards and data banks. A
World Wide Web site offering the technical specifications for a new product is an information
service.
Electronic Messaging– Electronic mail (e-mail) is the most widely used network application.
Electronic Data Interchange (EDI)– EDI permits business information to be transferred without
using paper.
Directory services – By using directory services, it is possible to store the last of files in a
central location to speed worldwide search operations.
Cellular Telephone: – In the past, two parties desiring to use the services of the telephone
company had to be linked by a fixed physical connection. But, in present cellular network make
it possible to maintain wireless phone connections even while travelling over large distances.
2 Types of computer network
A computer network is a group of computers linked to each other that enables the computer to
communicate with another computer and share their resources, data, and applications. Computer
network divided into two categories called wired and wireless.
Types of CN
Based on Based on
Based on
geographical communication
structure
area medium
Peer-2-Peer LAN Wired
Client/Server MAN Wireless
WAN
NOTE- All the networks can be of wired and wireless type.
, Wired Network: As we all know, “wired” refers to any physical medium made up of cables.
Copper wire, twisted pair, or fiber optic cables are all options. A wired network employs wires
to link devices to the Internet or another network, such as laptops or desktop PCs.
Wireless Network: “Wireless” means without wire, media that is made up of electromagnetic
waves (EM Waves) or infrared waves. Antennas or sensors will be present on all wireless
devices. Cellular phones, wireless sensors, TV remotes, satellite disc receivers, and laptops with
WLAN cards are all examples of wireless devices. For data or voice communication, a wireless
network uses radiofrequency waves rather than wires.
S.N Wired Network Wireless Network
A wired network employs wires to “Wireless” means without wire, media that is made
link devices to the Internet or up of electromagnetic waves (EM Waves) or infrared
another network, such as laptops or waves. Antennas or sensors will be present on all
1. desktop PCs. wireless devices
2. Faster transmission speed Slow transmission speed
3. Propagation delay is Low Propagation delay is high
4. More Secure & hence Reliable Less Secure & hence less Reliable
5. Devices must be hard-wired Installation is Quick
6. Less Expensive More Expensive
High installation & maintenance
7. cost Low installation & maintenance cost
8. Hub, Switch, etc. devices are used Wireless routers, access points, etc. are used.
LAN (Local Area Network)
Local Area Network is a group of computers connected to each other in a small area such as
building, office.
LAN is used for connecting two or more personal computers through a communication
medium such as twisted pair, coaxial cable, etc.
It is less costly as it is built with inexpensive hardware such as hubs, network adapters, and
ethernet cables.
The data is transferred at an extremely faster rate in Local Area Network.
Local Area Network provides higher security.
, PAN (Personal Area Network)
o Personal Area Network is a network arranged within an individual person, typically within a range
of 10 meters.
o Personal Area Network is used for connecting the computer devices of personal use is known as
Personal Area Network.
o Thomas Zimmerman was the first research scientist to bring the idea of the Personal Area
Network.
o Personal Area Network covers an area of 30 feet.
o Personal computer devices that are used to develop the personal area network are the laptop,
mobile phones, media player and play stations.
Wireless Personal Area Network is developed by simply using wireless technologies such as WiFi,
Bluetooth. It is a low range network. Wired Personal Area Network is created by using the USB.
Examples of Personal Area Network:
Body Area Network: Body Area Network is a network that moves with a person.
1 Computer network
A computer network is a set of devices connected through links. A node can be computer, printer, or any
other device capable of sending or receiving the data. The links connecting the nodes are known as
communication channels.Computer Network uses distributed processing in which task is divided among
several computers. Instead, a single computer handles an entire task, each separate computer handles a
subset.
o Computer Network is a group of computers connected with each other through wires, optical
fibres or optical links so that various devices can interact with each other through a network.
o The aim of the computer network is the sharing of resources among various devices.
o In the case of computer network technology, there are several types of networks that vary from
simple to complex level.
Goals of Computer Networks: The following are some important goals of computer networks:
Resource Sharing – Many organization has a substantial number of computers in operations,
which are located apart. Ex. A group of office workers can share a common printer, fax,
modem, scanner, etc.
High Reliability – If there are alternate sources of supply, all files could be replicated on two
or more machines. If one of them is not available, due to hardware failure, the other copies
could be used.
Inter-process Communication – Network users, located geographically apart, may converse
in an interactive session through the network. In order to permit this, the network must
provide almost error-free communications.
Flexible access – Files can be accessed from any computer in the network. The project can
be begun on one computer and finished on another.
Other goals include Distribution of processing functions, Centralized management, and
allocation of network resources, Compatibility of dissimilar equipment and software, Good
network performance, Scalability, Saving money, Access to remote information, Person to
person communication, etc.
Saving Money- The second goal of a computer network is saving money. Small computers
have a much excellent value proportion than higher ones. Mainframes are approximately a
method ten times quicker than the quickest single-chip microprocessors, but they cost a huge
number of times more.
Improve Performance- The fourth goal of a computer network is to improve accessibility and
the performance of the system. A system’s performance can be improved by inserting one or
more processors into it as its workload grows.
Communication Medium-The computer network offers a powerful communication medium.
The different user on the network can immediately identify a document that has been refreshed
on a network.
Application of computer network: Some of the network applications in different field are the following:
Marketing and sales– Computer networks are widely used in both marketing sales firms. These
are used by marketing professionals to collect, exchange, and analyzes data relating to
customer requirements and product development cycles. Teleshopping is also important part of
sales applications that use order-entry computers or telephones connected to an order-
processing network, and on-line reservation services for hotels airline and so on.
, Manufacturing– Now days, computer networks are used in a several aspects of manufacturing,
including the manufacturing process itself. Two applications which use a network to provide
necessary services are computer-assisted manufacturing (CAM) and computer –assisted
designing (CAD) both of which permit multiple users to work on a project simultaneously.
Financial Services– In Present, Financial services are completely dependent on computer
networks. Main applications are credit history searches, foreign exchange and investment
services, and Electronic Funds Transfer (EFT) that permits a user to transfer money without
going into bank.
Teleconferencing– With The help of teleconferencing conferences are possible to occur without
the participants being in the same place. Applications include simple text conferencing, voice
conferencing, and video conferencing.
Cable Television- Future Services provided by cable television network can include video on
request, as well as the same information, financial and communications services currently
provided by the telephone companies and computer networks.
Information Services- Network information services include bulletin boards and data banks. A
World Wide Web site offering the technical specifications for a new product is an information
service.
Electronic Messaging– Electronic mail (e-mail) is the most widely used network application.
Electronic Data Interchange (EDI)– EDI permits business information to be transferred without
using paper.
Directory services – By using directory services, it is possible to store the last of files in a
central location to speed worldwide search operations.
Cellular Telephone: – In the past, two parties desiring to use the services of the telephone
company had to be linked by a fixed physical connection. But, in present cellular network make
it possible to maintain wireless phone connections even while travelling over large distances.
2 Types of computer network
A computer network is a group of computers linked to each other that enables the computer to
communicate with another computer and share their resources, data, and applications. Computer
network divided into two categories called wired and wireless.
Types of CN
Based on Based on
Based on
geographical communication
structure
area medium
Peer-2-Peer LAN Wired
Client/Server MAN Wireless
WAN
NOTE- All the networks can be of wired and wireless type.
, Wired Network: As we all know, “wired” refers to any physical medium made up of cables.
Copper wire, twisted pair, or fiber optic cables are all options. A wired network employs wires
to link devices to the Internet or another network, such as laptops or desktop PCs.
Wireless Network: “Wireless” means without wire, media that is made up of electromagnetic
waves (EM Waves) or infrared waves. Antennas or sensors will be present on all wireless
devices. Cellular phones, wireless sensors, TV remotes, satellite disc receivers, and laptops with
WLAN cards are all examples of wireless devices. For data or voice communication, a wireless
network uses radiofrequency waves rather than wires.
S.N Wired Network Wireless Network
A wired network employs wires to “Wireless” means without wire, media that is made
link devices to the Internet or up of electromagnetic waves (EM Waves) or infrared
another network, such as laptops or waves. Antennas or sensors will be present on all
1. desktop PCs. wireless devices
2. Faster transmission speed Slow transmission speed
3. Propagation delay is Low Propagation delay is high
4. More Secure & hence Reliable Less Secure & hence less Reliable
5. Devices must be hard-wired Installation is Quick
6. Less Expensive More Expensive
High installation & maintenance
7. cost Low installation & maintenance cost
8. Hub, Switch, etc. devices are used Wireless routers, access points, etc. are used.
LAN (Local Area Network)
Local Area Network is a group of computers connected to each other in a small area such as
building, office.
LAN is used for connecting two or more personal computers through a communication
medium such as twisted pair, coaxial cable, etc.
It is less costly as it is built with inexpensive hardware such as hubs, network adapters, and
ethernet cables.
The data is transferred at an extremely faster rate in Local Area Network.
Local Area Network provides higher security.
, PAN (Personal Area Network)
o Personal Area Network is a network arranged within an individual person, typically within a range
of 10 meters.
o Personal Area Network is used for connecting the computer devices of personal use is known as
Personal Area Network.
o Thomas Zimmerman was the first research scientist to bring the idea of the Personal Area
Network.
o Personal Area Network covers an area of 30 feet.
o Personal computer devices that are used to develop the personal area network are the laptop,
mobile phones, media player and play stations.
Wireless Personal Area Network is developed by simply using wireless technologies such as WiFi,
Bluetooth. It is a low range network. Wired Personal Area Network is created by using the USB.
Examples of Personal Area Network:
Body Area Network: Body Area Network is a network that moves with a person.
