Introduction to computer networks

INTRODUCTION TO COMPUTER
NETWORKS
By: Nicholas K. Riungu, BSc, MSc IS

WHAT IS A COMPUTER NETWORK?
 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.
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IntroductionToComputerNetworks

PROTOCOLS, SERVICES AND STANDARDS:
 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.
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A SAMPLE COMPUTER NETWORK
Network
Hosts
Network
Cable
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NETWORK HOSTS & PERIPHERALS
 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.
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SERVER AND CLIENT MACHINES
 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
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WHY COMPUTER NETWORKS_1:
 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.
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 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.
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 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.
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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.
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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).
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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.
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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.
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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.
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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.
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TYPES OF COMPUTER NETWORKS_1:
 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
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 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
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 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.
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 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.
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 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.
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 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.
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 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.
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NETWORK COMPONENTS:
 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.
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Next Class
 Network Hardware Concepts
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Introduction to computer networks

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