IBPS Specialist (IT) Officers Professional Knowledge Study Material - Data Communication & Computer Network (Lesson 1)

Data Communication & Computer Network

Computer Network

Computer Network is a telecommunication channel through which we can share our data. It is also called data network. The best example of computer network is Internet.

A network must be able to meet certain criteria, these are mentioned below:

Performance
Reliability
Scalability

PERFORMANCE

It can be measured in following ways :

Transit time : It is the time taken to travel a message from one device to another.
Response time : It is defined as the time elapsed between enquiry and response.

Other ways to measure performance are :

Efficiency of software
Number of users
Capability of connected hardware

RELIABILITY

It decides the frequency at which network failure take place. More the failures are, less is the network's reliability.

SECURITY

It refers to the protection of data from the unauthorised user or access. While travelling through network, data passes many layers of network, and data can be traced if attempted. Hence, security is also a very important characteristic for Networks.

PROPERTIES OF GOOD NETWORK

Interpersonal Communication : We can communicate with each other efficiently and easily example emails, chat rooms, video conferencing etc.
Resources can be shared : We can use the resources provided by network such as printers etc.
Sharing files, data : Authorised users are allowed to share the files on the network.

BASIC COMMUNICATION MODEL

Communication model is used to exchange data between two parties. For example communication between a computer, server 4. and telephone (through modem).

Source

Data to be transmitted is generated by this device, example: telephones, personal computers etc.

Transmitter

The data generated by the source system are not directly transmitted in the form they are generated. The transmitter transforms and encodes the information in such a form to produce electromagnetic waves or signals.

Transmission System

A transmission system can be a single transmission line or a complex network connecting source and destination.

Receiver

Receiver accepts the signal from the transmission system and converts it to a form which is easily managed by the destination device.

Destination

Destination receives the incoming data from the receiver.

DATA COMMUNICATION

The exchange of data between two devices through a transmission medium is Data Communication. The data is exchanged in the form of 0's and l's. The transmission medium used is wire cable. For data communication to occur, the communication device must be part of a communication system. Data Communication has two types Local and Remote which are discussed below :

Local : Local communication takes place when the communicating devices are in the same geographical area, same building, face-to-face between individuals etc.

Remote : Remote communication takes place over a distance i.e. the devices are farther. Effectiveness of a Data Communication can be measured through the following features :

Delivery : Delivery should be done to the correct destination.
Timeliness : Delivery should be on time.
Accuracy : Data delivered should be accurate.

COMPONENTS OF DATA COMMUNICATION

Message : It is the information to be delivered.
Sender : Sender is the person who is sending the message. Receiver : Receiver is the person to him the message is to be delivered.
Medium : It is the medium through which message is to be sent for example modem.
Protocol : These are some set of rules which govern data communication.

LINE CONFIGURATION IN COMPUTER NETWORKS

Network is a connection made through connection links between two or more devices. Devices can be a computer, printer or any other device that is capable to send and receive data. There are two ways to connect the devices :

Point-to-Point connection
Multipoint connection

1. POINT-TO-POINT CONNECTION

It is a protocol which is used as a communication link between two devices. It is simple to establish. The most common example for Point-to-Point connection (PPP) is a computer connected by telephone line. We can connect the two devices by means of a pair of wires or using a microwave or satellite link.

2. MULTIPOINT CONNECTION

It is also called Multidrop configuration. In this connection two or more devices share a single link.

There are two kinds of Multipoint Connections :

If the links are used simultaneously between many devices, then it is spatially shared line configuration.
If user takes turns while using the link, then it is time shared (temporal) line configuration.

TYPES OF NETWORK TOPOLOGY

Network Topology is the schematic description of a network arrangement, connecting various nodes(sender and receiver) through lines of connection.

BUS TOPOLOGY
Bus topology is a network type in where every computer and network device is connected to single cable.

Features of Bus Topology

It transmits data only in one direction.
Every device is connected to a single cable

RING TOPOLOGY
It is called ring topology because it forms a ring as each computer is connected to another computer, with the last one connected to the first. Exactly two neighbours for each device.

Features of Ring Topology

A number of repeaters are used and the transmission is unidirectional.
Date is transferred in a sequential manner that is bit by bit.

STAR TOPOLOGY

In this type of topology all the computers are connected to a single hub through a cable. This hub is the central node and all others nodes are connected to the central node.

Features of Star Topology

Every node has its own dedicated connection to the hub.
Acts as a repeater for data flow.
Can be used with twisted pair, Optical Fibre or coaxial cable.

MESH TOPOLOGY

It is a point-to-point connection to other nodes or devices. Traffic is carried only between two devices or nodes to which it is connected. Mesh has n (n-2)/2 physical channels to link hn devices.

Types of Mesh Topology

Partial Mesh Topology : In this topology some of the systems are connected in the same fashion as mesh topology but some devices are only connected to two or three devices.
Full Mesh Topology : Each and every nodes or devices are connected to each other.

Features of Mesh Topology

Fully connected.
Robust.
Not flexible.

TREE TOPOLOGY

It has a root node and all other nodes are connected to it forming a hierarchy. It is also called hierarchical topology. It should at least have three levels to the hierarchy.

Features of Tree Topology

Ideal if workstations are located in groups.
Used in Wide Area Network.

HYBRID TOPOLOGY

It is two different types of topologies which is a mixture of two or more topologies. For example if in an office in one department ring topology is used and in another star topology is used, connecting these topologies will result in Hybrid Topology (ring topology and star topology).