Intro of computer_network

BY: AANAND BOHARA
Introduction to Computer
Networks

What is a computer network?
1
A computer network is a computer system comprising of
two or more computers that are linked together by a
telecommunication medium.
It is the interconnection of computers that are able to
communicate and share resources.
From a software perspective, a computer network is a
collection of the applications, protocols, services and
standards that govern how two or more computers
interact to share resources.

Protocols, services and standards:
2
Protocols are the rules that govern how network services
are requested and offered.
Network services are the functions that are performed by
the network on behalf of the applications (users).
Network services will include functions such as
composing a message, error checking, moving messages
from point A to B, and so on.
Network standards define the accepted level of operation
of the different network services.
They act as a benchmark for the services requested and
offered.

A sample computer network
3
Network
Hosts
Network
Cable

Network hosts & peripherals
4
The computers connected to a network a generally
referred to as network hosts.
The printer in figure above is referred to as a
peripheral, or a shared resource.
 If a printer has the capability to connect to the network
directly, it is called a network enabled printer, and in this case
it is a host.
The term networking is used to refer to the process
of creating and configuring a network.

Server and client machines
5
Network hosts can be classified into two
 Server
 Client
A client computer is one that uses a shared resource
owned by another host.
A server computer is one that owns or contains a
shared resource on a network.
In our sample network, we have two servers and
three clients.
 A print server
 A file server

Why computer networks:
6
Consider your mobile phone handset:
 Why do you need it?
 Why should it be on a network?
 What do you use it for?
We are living in a connected world where people work
through collaborations.
For example: each member of a project team generates a
report on a given part of the project. These are then
consolidated to get the final project report. It makes work
easy
Collaboration makes work easy and keeps people in
touch.

7
We need computer networks for two main reasons:
 Resource sharing
 Communication.
Using networks we share hardware, software and data
resources with others
For example:
 We share a network printer across a network
 We can upload, download or read shared files
 Software update can be shared across a network from a common
server
We stay in touch with each other using computer
networks: email, VoIP, Video conferencing, etc.

8
In a specific way, computer networks enable individuals
and organizations to achieve the following:
 Communication within an organization
 Communication between an organization and another
 Sharing data and information
 Sharing hardware and peripherals
 Sharing software
 Centralized administration and control
These benefits are not easily achieved in a non-
networked environment.
Thus we generally refer to a network as a shared
environment.

9
Communication within an organization:
The employees within an organization are able to
communicate effectively by sending electronic mail
(e-mail) messages to each other in real time.
Individuals are also able to call each other or send
short messages (SMS) to each other.

10
Communication between organizations:
With the help of a network, the employees in an
organization are able to communicate with employees in
other organizations.
The dean of student at KeMU can send an e-mail to the
principle of Meru Technical Training Institute (MTTI)
without having to go there, as long as each of them has a
computer that is connected to the shared network.
To achieve this, this requires the interconnection of the
networks of the two organizations.
We refer to such a interconnection as an Internetwork (or
internet).

11
Sharing data and information:
The value of a computer system is its ability to process
the required information.
Once the information is processed, it is used in an
organization to achieve its goals.
The data/files that are created by one employee in an
organization can be shared by other employees through a
computer network.
This enables collaboration in the achievement of the
objectives of the organization.
It reduces the time required in completing different tasks
within the organization.

12
Sharing hardware and peripherals:
Peripheral devices such as printers are essential in
the operation of an organization, but they are also
costly.
Since it is not possible for each employee to have
their own printer, a single printer can be shared by
several employees effectively across a computer
network.
Users can also share the space on the hard disk drive
to store data.

13
Sharing software:
A computer network makes it possible to store
software on one machine and then share it on the
other computer across a network.
It also allows the sharing of software licenses.

14
Centralized administration and control:
The administration and control of the hardware and
software within an organization can easily and
effectively be achieved over a computer network.
System administrators are able to install and
configure both hardware and software from a remote
location.
Software updates are also easily deployed across the
network, reducing the amount of time involved.
User access can also be managed.

Types of computer networks:
15
Six ways to classify computer networks:
 By the scope or size of the networks
 By ownership of the network Infrastructure
 By the topology: (topologies are covered in module 2)
 Classification by Transmission media
 By the mode of managing the connection
 By transmission technology used

16
Classification by the scope or size of the networks:
 Local Area Networks (LAN)
 Personal Area Network (PAN)
 Metropolitan Area Networks (MAN)
 Campus Area Networks (CAN)
 Wide Area Networks (WAN)

17
Classification by ownership of the network
Infrastructure:
 Private networks – A private network is one where
both the equipment and infrastructure are entirely
owned by a single person or organizations.
 Public Networks – this is a type of network where the
interconnection devices and infrastructure is owned and
maintained by the state on behalf of a people. No single
person or institution can claim ownership or control of a
public network. It is available for all and shared by all.

18
Classification by the topology: (topologies are
covered in module 2)
 Bus Networks – this is a network where the devices are
connected using the bus topology and its associated
technologies.
 Ring Networks – in these networks, the devices are
connected to form a ring.
 Star Networks – the devices in this network are
connected based on a star topology.
 Hybrid Networks – in these networks, there is a
combination of two or more topologies in the organization of
the devices in the network.

19
Classification by the transmission medium used:
(transmission media is covered in module 2)
 Wired Networks – these are networks where the
devices are connected using some form of cables.
 Wireless Networks – in these networks, no cables are
used. The signal is transmitted through the air from one
point to the next.

20
Classification by the mode of managing the connection:
 Peer-to-peer Networks – these are computer networks
where each node manages its end of the connection and its
local resources while sharing the resources with the other
networks hosts. No single host controls the network. These
networks are also referred to as workgroup networks.
 Client-Server networks – in a client-server network, one
host is dedicated as the server to the network, and controls
how the other hosts communicate and share resources. All the
other hosts are clients. In certain cases, there can be two or
more servers in a client-server network, each dedicated to a
different resource.

21
Classification by transmission technology used:
 Broadcast Networks – broadcast networks
communicate by sending the packets to the shared
media, then allowing each node to sample a get a copy
where necessary. The packets move along the shared
medium until it reached the intended recipients.
Broadcast networks are based on shared medium
protocols.
 Point-to-Point Networks – in point-to-point
networks, a packet is sent directly to a single destination.
In such networks there is a direct path between any two
communicating devices. Each connection is shared by
only two devices, which it connects.

Network components:
22
Like any other computer system, a computer
network comprises of hardware and software
components.
The hardware comprise of the computers, peripheral
devices, cables/interconnection medium, and the
interconnection devices.
Computer software comprise of the operating
systems, server applications, client applications, as
well as the protocols and standards that govern the
delivery of network services.

Intro of computer_network

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Intro of computer_network