Notes and Study Materials

Data Communications and Its Characteristics:

Data communications means the exchange of data between two devices via some form of transmission medium such as a wire cable. For data communications to occur, the communicating devices must be part of a communication system made up of a combination of hardware (physical equipment) and software (programs).

The effectiveness of a data communications system depends on four fundamental characteristics: delivery, accuracy, timeliness, and jitter.

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Different Characteristics of Networks

 

A network is a set of devices (often referred to as nodes) connected by communication links. A node can be a computer, printer, or any other device capable of sending and/or receiving data generated by other nodes on the network.

 

A network must be able to meet a certain number of criteria. The most important of these are performance, reliability, and security.

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Protocols and Standards

 

I.Protocols:

In computer networks, communication occurs between entities in different systems. An entity is anything capable of sending or receiving information.

 

A protocol is a set of rules that govern data communications. A protocol defines what is communicated, how it is communicated, and when it is communicated. The key elements of a protocol are syntax, semantics, and timing.

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Different Data Flow Directions

 

Communication between any two devices can be simplex, half-duplex, or full-duplex.

 

1. Simplex:

In simplex mode, the communication is unidirectional, as on a one-way street. Only one of the two devices on a link can transmit; the other can only receive which can be represented in the following figure.

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Different Types of Connections

 

A network is two or more devices connected through links. A link is a communications pathway that transfers data from one device to another. For communication to occur, two devices must be connected in some way to the same link at the same time.

 

There are two possible types of connections: point-to-point and multipoint.

 

1.Point-to-Point:

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Types of Topologies:

 

The term physical topology refers to the way in which a network is laid out physically.

 

Two or more devices connect to a link; two or more links form a topology. The topology of a network is the geometric representation of the relationship of all the links and linking devices (usually called nodes) to one another.

There are four basic topologies possible: mesh, star, bus, and ring which are shown in the following figure.

 

1.Mesh Topology:

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