What is a Computer Network? Uses of
Computer Networks.
During
20th century the most important technology has been the information gathering,
its processing and distribution. The computers and communications have been
merged together and their merger has had a profound effect on the manner in
which computer systems are organized.
The
old model in which a single computer used to serve all the
computational needs of an organization has been replaced by a new one in which
a large number of separate but interconnected computers do the job. Such
systems are called as computer
networks.
• Two computers are said to
be interconnected if they interchange information. The connection between
the separate computers can be done via a copper wire, fiber optics, microwaves
or communication satellite.
•
A printer, computer, or any machine that is capable of communicating on
the network is referred to as a device or node.
•
We can also say that computer network is an interconnection of various
computers to share software, hardware and data through a communication medium
between them. The computers connected in a network share files, folders,
applications and resources like scanner, web-cams, printers etc.
•
The best example of computer network is the Internet.
Computer Network
Properties
• Scope: A network architecture should
solve so many general problems as possible.
• Scalability:
A network must work well independently of the number of nodes that compose it.
• Robustness:
The design of a network should allow it to function correctly, even though
there are defective nodes.
• Self-configuration
and Optimization: A network should have a minimal intervention of the
administrator. In turn, you must have a series of parameters that allow the
administrator to adjust them to obtain an optimal configuration for some and other
networks according to their characteristics.
• Migration:
If you decide to change networks, migration should not be affected in its
properties and operation.
• Determinism:
Under the same conditions, the network must always work the same.
Computer Network
Model
A computer networks communication
can be based on centralized, distributed or collaborative computing.
Centralized computing involves many workstations or terminals, connected to one
central mainframe or other powerful computer. Distributed computing
interconnects one or more personal computers and allows various services like
Data sharing, hardware sharing resources sharing or network sharing.
The collaborative computing is the combination of centralized and distributed
computing.
Centralized
computing
• It is also known as
client-server computing.
•
In this type of system, multiple computers are joined to one powerful mainframe computer.
•
The server or mainframe computer has huge storage and processing capabilities.
• The computers that are
connected to the mainframe or server are called Clients or Nodes.
•
These nodes are not connected
to each other; they are only connected to server.
Distributed computing
• If one computer can
forcibly start, stop or control another the computers are not autonomous. A
system with one control unit and many slaves, or a large computer
with remote printers and terminals is not called a computer network, it is
called a Distributed System.
•
Distributed computing means that the task is divided among multiple computers.
•
Distributed computing interconnects one ore more personal computers or
Workstations.
•
In distributed computing, the nodes are capable of processing their own data
and rely on network for services other than data processing.
•
It allows various services like network sharing, hardware sharing and file
sharing.
Collaborative computing / Hybrid computing
•
It is the combination of centralized and distributed computing
•
In collaborative computing, the nodes are able to serve the basic needs of
their users but they are dependent on some other computers for processing some
specific request.
Computer Network Classification
The local
area network communication can be constructed by using server based model or peer
to peer model. In peer to peer networks, the individual clients share data and
resources but no one computer is treated as server.
Networks
can be classified into local area Networks, metropolitan area Networks and wide
area networks. Local area network is the small network that cover a small area
of Network. Metropolitan area networks are created by combining various local
area networks. Wide area networks are the biggest networks that provide
connectivity across the globe.
Computer Network topology
The
physical arrangement of computers in a communication network is called as
topology. In star topology, every system on the network is connected to a
central controller called Hub and all the data is transmitted through this.
Star topology is very easy to install and configure. In bus topology, a single
cable acts as a backbone of the communication network and all the nodes or
computers are attached to it by using T connectors.
Uses of Computer Networks
The
computer networks are playing an important role in providing services to large
organizations as well as to the individual common man.
Service Provided by
the Network for Companies:
•
Many organizations have a large number of computers in operation. These
computers may be within the same building, campus, city or different cities.
•
Even though the computers are located in different locations, the organizations
want to keep track of inventories, monitor productivity, do the ordering and
billing etc.
•
The computer networks are useful to the organizations in the following ways:
1.
Resource sharing.
2.
For providing high reliability.
3.
To save money.
4.
It can provide a powerful communication medium.
Resource sharing
• It
allows all programs, equipment and data available to anyone on the network
irrespective of the physical location of the resource and the user.
•
Show in Fig (a) and (b) which shows a printer being shared and
different information being shared.
High reliability
due to alternative sources of data
• It
provides high reliability by having alternative sources of data. For e.g. all
files could be replicated on more than one machines, so if one of them is
unavailable due to hardware failure or any other reason, the other copies can
be used.
•
The aspect of high reliability is very important for military, banking, air
traffic control, nuclear reactor safety and many other applications where
continuous operations is a must even if there are hardware or software failures.
Money saving
• Computer
networking is an important financial aspect for organizations because it saves
money.
•
Organizations can use separate personal computer one per user instead
of using mainframe computer which are expensive.
•
The organizations can use the work-group model (peer to peer) in which all the
PCs are networked together and each one can have the access to the other for
communicating or sharing purpose.
•
The organization, if it wants security for its operation it can go in for the
domain model in which there is a server and clients. All the clients can
communicate and access data through the server.
•
The whole arrangement is called as client -server model.
Client: The
individual workstations in the network are called as clients.
Server
The
central computer which is more powerful than the clients and which allows the
clients to access its software and database is called as the server .
•
Server computers typically are more powerful than client computers or are
optimized to function as servers.
Communication in
client-server configuration:
•
The client places a request on the server machine when he wants an access to
the centralized resources.
•
The server responds to this request and sends the signal accordingly to the
client.
•
The software run at the client computer is called as client program. This
software configures the computer to act as a client.
•
Similarly the software run on the server computer IS called as server program.
It configures a computer to act as a server.
Communication
medium
•
A computer network provides a powerful communication medium among widely
separated employees.
•
Using network it is easy for two or more employees, who are separated by
geographical locations to work on a report, document or R and D simultaneously
i.e. on -line.
Networks for People:
•
Starting in 1990s, the computer networks began to start delivering services to
the private individuals at home.
•
The computer networks offer the following services to an individual person:
1.
Access to remote information
2.
Person to person communication
3.
Interactive entertainment.
Access to remote information
Access to
remote information involves interaction· between a person and a remote database.
Access to remote information comes in many forms like:
(i)
Home shopping, paying telephone, electricity bills, e-banking, on line share
market etc.
(ii)
Newspaper is. On-line and is personalized, digital library consisting of books,
magazines, scientific journals etc.
(iii)
World wide web which contains information. about the arts, business, cooking,
government, health, history, hobbies, recreation, science, sports etc.
Person to person communication
Person to
person communication includes:
(i)
Electronic-mail (e-mail)
(ii)
Real time e-mail i.e. video conferencing allows remote users to communicate
with no delay by seeing and hearing each other. Video-conferencing is being
used for remote school, getting medical opinion from distant specialists etc.
(iii)
Worldwide newsgroups in which one person posts a message and all other
subscribers to the newsgroup can read it or give their feedback’s.
Interactive entertainment
Interactive
entertainment includes:
(i)
Multi-person real-time simulation games.
(ii)
Video on demand.
(iii)
Participation in live TV programmes likes quiz, contest, discussions etc.
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