LAN Topology or Network Topology - Bus - Ring - Star

Network topology (LAN topology)The arrangement or connection pattern of computers or nodes and other devices of the network is called network topology.

The three basic topologies are:Bus Topology

Ring Topology

Star Topology

Bus topologyThe network topology in which computers and other devices are arranged in linear format which uses a common backbone or wire to connect all the computers and devices is called bus topology.

The advantages of bus topology are:

It is easy to set up computers and other devices in bus topology, because all the devices are connected through a single wire.

It requires fewer cable media, so it is cheaper than other topologies.

It is easy to add new node to the network.

The disadvantages of disadvantages are:

The whole network system collapses if the cable or backbone is damaged.

The network slows down if additional computers are connected.

The limited length of the cable in a network may restrict to connect the workstation or devices.

Ring topology (Loop topology)

The network topology in which computers are connected in the shape of a circle without any end points is called ring topology. Each workstations contains two neighbours for communication or an input and output connections.

Advantages of ring topology are:

It is easy to set up and reconfigure.

Each computer gets equal opportunity to access the network resources.

Disadvantages of ring topology are:

Failure of any cable or single computer may affect the entire network.

It is difficult to detect the errors in this type of network.

Adding or removing the devices affects the entire network.

Star topology

The network topology in which all computers or other devices are connected through a central device called hub or switch is called star topology.

The advantages of star topology are :It is easy to detect errors in star topology.

It is set up and configure.

Failure of a single computer or cable does not affect the entire network.

The disadvantages of star topology are: It requires more cable in comparison of bus topology so it is costlier.
Failure of central devices (hub or switch) break down the whole system.

Network Architecture - Client / Server Network and Peer to Peer Network

Network Architecture [Models of Computer Network]

The arrangement of the computers on the network which is based on the computing model is called network architecture.

Its types are

Centralized computing network

Client / Server Network

Peer to Peer Network

Centralized computing network

A centralized computing network is a network in which a central host computer performs data processing and storage on behalf of clients.

Client/Server networkClient/ server network is a type of network architecture that consists of at least one server and one or more clients or workstations, where users do their work. 

It provides central security administration and the network administrator is responsible for data security and other resources management of the network.

Peer-to-Peer networkPeer-to-Peer network is a group of computers, which function both as servers and workstations to share data, information and other resources of the network. 

It lacks centralized network administration, where the network administrator needs to manage security on each computer. 

It provides no reliable security and might put data in higher risks.

Network Categories - LAN, MAN, WAN

Network Categories

}LAN (Local Area Network)

}MAN (Metropolitan Area Network)

}WAN (Wide Area Network)

LAN

}It is a network which covers small area i.e. within a room, building, or short distance.

}It is controlled by a single organization.

}It uses private connection media.

}LAN offers bandwidth of 10-100 Mbps.

}E.g.: network in a school, college or cyber café.

MAN

}A MAN is a network of computer is computers which are spread over a metropolitan area such as within a city.

}It is controlled by single or group of organization.

}It uses private or public connection media.

E.g.: interconnection between different branches of banks of same branch, ISP Providing internet services.

WAN

}The network system of connecting two or more computers generally across the wide geographical area is called WAN.

}It is controlled by group of organization.

}It uses public connection media such as telephone lines and wireless technology.

}Eg. Internet

Software components of computer network

The software components of computer network are:

Network operating system

Device drivers

Network protocol

Network Operating System

The group of programs that manages the resources on the network is called the network operating system.

Examples of network operating system are Novell Netware, Microsoft Windows NT, Linux, Unix etc.

ProtocolsProtocols are set of rules that the computers on the network must follow to communicate and to exchange data with each other.

Some examples of protocols are TCP/IP, ARP, HTTP, FTP etc.

Device driver

Device driver is a program that controls the functionality of the hardware device.

Example NIC driver controls the functionality of NIC

Hardware Components of Computer Network

Hardware Components

Physical parts and devices used to connect computers in the network environment are called hardware components.

The hardware components of a network are:

Server

Workstation

Connectors

Cables

NIC

Hub

Repeater

Bridge

Switch

Router

Gateway

MODEM

Server

Server is the main computer that provides services, data and other resources to other computers in the network environment.

The server computer uses networking operating software like Novell Netware Server, Windows NT Server, Linux, UNIX, etc.

Different types of servers are file server, print server, application server etc.

The differences between Dedicated Server and Non-dedicated Server are:

Dedicated Server	Non-dedicated Server
A server computer that controls and provides services hardware and software resources to other computers on the network is called dedicated server.	A computer on a network that allows a user to use it as a workstation and provides facilities of sharing its resources to other computers on the network is called non-dedicated server.
It controls and provides resources to the client computers on the network but does not allow a user to use it as a workstation.	It controls and provides resources to the other computers on the network as well as allows a user to use it as a workstation.

WorkstationWorkstation is a computer, where the client works which requests services, data and other resources available on the server.

The client computer uses operating system like Windows 98, Windows XP,  Red Hat Linux Workstation,etc.

Node

Each computer or device in a network is called node.

CablesCables are commonly used mediums for physical channel for transmitting data across network.

Examples of cables are coaxial, twisted pair and fiber optic cable.

NIC

A Network Interface Card (NIC) is a hardware device that acts as an interface through which a computer is connected to a network.

The function of NIC is to convert data into electronic signals and transfer them through cables and vice-versa.

ConnectorsConnectors acts as an interface between the NIC of the computer and the cable that passes data from one computer to another.

Examples of connectors are BNC used with coaxial cable, RJ 45 used with UTP cable, ST used with fiber optic cable etc.

Hub

A hub is a network device with multiple points or ports which acts as a central point from where different computers and other devices are connected.

Hub is mostly used in physical star topology.

It cannot determine source and destination device of the data. 

Hub broadcasts the electric signals

Switch

A switch is a networking device that has multiple connecting ports which is often used interchangeably with the bridge.

It can determine source and destination device of data.

RepeaterRepeater is a device that amplifies the incoming signals, creates a copy of it and transmits the signals on network.

Bridge

A bridge is a device that connects two or more similar types of network which filters the data or inspects incoming signals and decides whether to forward the signals or discard them.

Router

Router is an intelligent device that connects two different networks which uses the address for filtering and forwarding the data as well as it has an ability to determine the best route for destination.

Gateway

Gateway is an interconnecting device that connects two dissimilar networks.

MODEM

MODEM is a device which is used to transfer the data of one computer to another computer using telephone lines.

The role of MODEM in data transmission is that it transfers data from one computer to another through telephone line. It also converts the digital signal into analog and vice versa.

Modulation

The process of translating digital signals of a computer to analog signals, which are then transmitted across the standard telephone lines, is known as modulation.

Demodulation

The process of translating analog signals from a phone line and converts then into digital signals for the computer is known as demodulation.

How does MODEM help in transmission of data in computer network?

MODEM helps in transmission of data in computer network by transferring the data of one computer to another using a telephone line. It converts the discrete stream of digital ON-OFF electrical pulses used by computers into the continuously variable analog wave patterns over existing telephone lines and vice versa.

Mention the importance of MODEM in computer network.

The importance of MODEM in computer network is that it enables a computer to transmit data and files over a telephone line. It can convert digital signals into analog signals and vice-versa.

Modes of Transmission and its types [Simplex, Half Duplex and Full Duplex]

CommunicationCommunication means sending and receiving information between two or more persons.

TelecommunicationTelecommunication is a system of transmission of sounds, images, texts or data in the form of electronic signals.

Data communication

A data communication system is the collection of hardware, software and other devices that allows to exchange data, information and voice between two or more devices through a wire or radio waves.

The components of data communication are data, sender, medium, receiver and protocol.

Any two examples of data communication are e-mail and chat

Data transmission mode

Data transmission mode is the way of transmitting data from one device to another.

The modes of data transmission are simplex mode, half duplex mode, full duplex mode

Simplex mode

The mode of transmission where transmission can take place in only one direction is called simplex mode.

Examples of simplex mode are TV Broadcasting, Radio transmission and Newspaper.

Half-duplex mode

The mode of transmission where data can be transmitted to both directions, but only to one direction at a time is called half-duplex mode.

Examples of half-duplex mode are Wireless handset and Walky-talky

Full-duplex mode

The mode of transmission which allows simultaneous transmission of data to both directions is called full-duplex mode.
Example of full-duplex mode is telephone

BandwidthBandwidth can be defined as the maximum volume of data that can be transmitted through the communication medium.

We can measure bandwidth in digital devices by bits per second and in analogue devices by cycles per second or Hertz (Hz).