When we communicate, we are sharing information. This sharing can be local or remote. Between individuals, local communication usually occurs face to face, while remote communication takes place over distance.
Data communications are the exchange of data between two devices via some form of transmission medium.
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;
Delivery - The system must deliver data to the correct destination. Data must be received by the intended device or user and only by that device or user.
Accuracy - The system must deliver the data accurately. Data that have been altered in transmission and left uncorrected are unusable.
Timeliness - The system must deliver data in a timely manner. Data delivered late are useless. In the case of video and audio, timely delivery means delivering data as they are produced, in the same order that they are produced, and without significant delay. This kind of delivery is called real-time transmission.
Jitter - Jitter refers to the variation in the packet arrival time. It is the uneven delay in the delivery of audio or video packets. For example, let us assume that video packets are sent every 3D ms. If some of the packets arrive with 3D-ms delay and others with 4D-ms delay, an uneven quality in the video is the result.
