Define standard. State and explain the characteristics of data communication system.

Standard: Standards are required to govern the physical, electrical & procedural characteristics of communication equipment. Computer from different vendors must communicate with each other & with the ongoing evolution of protocol standards, customers will no longer accept special-purpose protocol conversion software development.

Organization of standards:

(i) Internal society

(ii) ISO

(iii) ITU-T

(iv) ATM-Forum 

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

(i) 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.

(ii) Accuracy: The system must deliver the data accurately. Data that have been altered in transmission and left uncorrected are unusable.

(iii) 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, and without significant delay. This kind of delivery is called real-time transmission.

(iv) 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.