Computer Network

Introduction

Types of Network

Classification of Network Architecture

Network Topology

A computer network is a telecommunications

network that allows computers to exchange data.

The connection between networked computing

devices is established using either wired media or

wireless media.

The best-known computer network is the

internet.

Based on the size and the coverage area, networks are

categorized into the following types:

Personal Area Networks (PANs)

Local Area Networks (LANs)

Metropolitan Area Networks (MANs)

Wide Area Networks (WANs)

A personal area network (PAN) is a computer network used for

communication among computer and different information

technological devices close to one person.

Is a small network established for communication between different

devices, such as laptops, computers and mobiles.

A pan may include wired and wireless devices.

The reach of a pan typically extends to 10 meters.

A local area network (LAN) is a network that connects computers

and devices in a limited geographical area such as a home, school,

office building, or closely positioned group of buildings.

Each computer or device on the network is a node.

Wired LANs are most likely based on Ethernet technology.

It is relatively larger than LAN and extends across a

city or a metropolitan.

It is created by connecting two or more LANs

located at different locations in a city.

A wide area network (WAN) is a computer network that covers a large

geographic area such as a city, country, or spans even intercontinental distances.

A WAN uses a communications channel that combines many types of media

such as telephone lines, cables, and air waves.

A WAN often makes use of transmission facilities provided by common

carriers, such as telephone companies.

One of the most prominent examples of the existing wans is the Internet.

On a network built using the client-server architecture, the devices

communicate to other devices through a central computer referred to as a

server.

The server is a terminal with high processing power, which provides services

for the other computers on the network.

Hardware Components

Servers −Servers are high-configuration computers that manage the resources of the

network. The network operating system is typically installed in the server and so they give

user accesses to the network resources. Servers can be of various kinds: file servers,

database servers, print servers etc.

Clients / Workstations− Clients are computers that request and receive service from the

servers to access and use the network resources.

Transmission Media − Transmission media are the channels through which data is

transferred from one device to another in a network. Transmission media may be guided

media like coaxial cable, fibre optic cables etc; or maybe unguided media like microwaves,

infra-red waves etc.

Connecting Devices − Connecting devices act as middleware between networks or

computers, by binding the network media together. Some of the common connecting devices

are:

a. Routers

b. Bridges

c. Hubs

d. Repeaters

e. Gateways

f. Switches

Software Components

Networking Operating System − Network Operating Systems is typically installed in

the server and facilitate workstations in a network to share files, database,

applications, printers etc.

Protocol Suite − A protocol is a rule or guideline followed by each computer for data

communication. Protocol suite is a set of related protocols that are laid down for

computer networks. The two popular protocol suites are −

a. OSI Model ( Open System Interconnections)

b. TCP / IP Model

The pattern of interconnection of nodes in a network is

called the Topology.

This layout also determines the manner in which

information is exchanged within the network.

The different types of network topologies that can be used to set up a network are:

✓ Bus Topology

✓ Star Topology

✓ Ring Topology

✓ Tree Topology

✓ Hybrid Topology

Bus topology

A bus topology is a topology for a Local Area Network (LAN) in which

all the nodes are connected to a single cable. The cable to which the

nodes connect is called a "backbone". If the backbone is broken, the

entire segment fails. Bus topologies are relatively easy to install and

don't require much cabling compared to the alternatives.

Advantages of Bus Topology

1.It is simple, reliable and easy to use.

2.It is easy to extend any number of computers can be added using

the connector in a bus topology.

3.It is less expensive than another arrangement

Disadvantages of Bus Topology

1.If the cable fails, then the entire system fails to respond to the user.

2.Since the cable is one, fault finding and troubleshooting become

very difficult.

3.Data traffic is high.

Ring topology

A ring topology is a topology for a Local Area Network (LAN) in which every

device has exactly two neighbors for communication purposes.

Advantages of ring topology

1. All data flows in one direction, reducing the chance of packet

collisions.

2. A network server is not needed to control network connectivity

between each workstation.

3. Data can transfer between workstations at high speeds.

4. Additional workstations can be added without impacting

performance of the network.

Disadvantages of ring topology

1.All data being transferred over the network must pass through each

workstation on the network, which can make it slower than a star

topology.

2. The entire network will be impacted if one workstation shuts down.

3. The hardware needed to connect each workstation to the network is

more expensive than Ethernet cards and hubs/switches.

Star topology

A star topology is a topology for a Local Area Network (LAN) in which all

nodes are individually connected to a central connection point, like a hub or

a switch. A star takes more cable than e.g. a bus, but the benefit is that if a

cable fails, only one node will be brought down.

Advantages of star topology

1. It is very reliable – if one cable or device fails then all the others

will continue to work

2. It is high-performing as no data collisions can occur

3. Easy to extend

Disadvantages of star topology

1. It is expensive to install as this type of network uses the most

cable (network cable is expensive)

2. Extra hardware is required (hubs or switches) which adds to cost

3. If a hub or switch fails, all the devices connected to it will have

no network connection

A tree topology combines characteristics of linear bus and star topologies. It consists of

groups of star-configured workstations connected to a linear bus backbone cable. Tree

topologies allow for the expansion of an existing network, and enable schools to

configure a network to meet their needs.

Tree topology

Advantages of a Tree Topology

1. Point-to-point wiring for individual segments.

2. Supported by several hardware and software venders.

Disadvantages of a Tree Topology

1. Overall length of each segment is limited by the type of cabling

used.

2. If the backbone line breaks, the entire segment goes down.

3. More difficult to configure and wire than other topologies.