The effectiveness of a data communications system depends on following four fundamental characteristics.
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. For this purpose the destination address must be assigned for the data. Even if we need to convey some message to someone in a large gathering, we first announce the name of the person to whom we wish to talk or convey and then convey the message.
2. Accuracy :- The delivery to the intended destination must be accurate i.e. it must be delivered as it was conveying the same meaning as the sender would have communicated if communicated directly face-to-face. The data which gets altered during transmission would be unusable. Thus, the data transmitted must be accurate and unaltered.
3. 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.
4. Jitter :- It 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 30 ms. If some of the packets arrive with 30-ms delay and others with 40-ms delay, an uneven quality in the video is the result.
Data that is required to be communicated in a networked environment may be of the following types.
Textual:- The textual form of data constitute of characters patterns. One of the standard character set is American Standard Code for Information Interchange (ASCII). ASCII is a 7-bit or 8-bit that forms all character sets including Capital A-to-Z, Small a-to-z and special character including some punctuation marks, bracket, colon etc.
Another character set called Unicode character set. It is a 16-bit character set designed to cover all the world’s major living languages, in addition to scientific symbols and dead languages that are the subject of scholarly interest. It eliminates the complexity of multi byte character sets that are currently used on UNIX and Windows to support Asian languages. Unicode was created by a consortium of companies including Apple, Microsoft, HP, Digital and IBM and merged its efforts with the ISO-10646 standard to produce a single standard in 1993
Numeric:- Numeric data contains the data formed with numeric digits. Different types of numeric data mat be formed using Hexadecimal, Decimal, Octel or Binary number system. Numeric data is converted from one system to binary by using mathematical algorithm.
Picture and Images:- Pictures and Images are formed using picture elements in short called as “pixel”. Each element (pixel) is then assigned bit pattern. If only one bit is assigned to a pixel, then it will be displayed in only two shared, a black and a white. Here bit value ‘1’ represent a white colour and the value ‘0’ represent the black colour.
By assigning more bits to a picture element, picture may be seen in more shades and hence more clarity of the picture. For example, if three bits are assigned to a pixel then picture can have eight shades.
Resolution of the picture is the number of pixels in a given size of picture or image. Thus an image having 10000 pixels has more resolution than a picture having 1000 pixels in the same size.
Audio:- Audio is the recording of sound. Audio is a continuous signal. We make use of the microphone for converting the acoustic signals to electrical signals.
Video:- Recording of picture or movie is called video. It is recorded using a high quality camera. it can be a combination of images, each a discrete entity, arranged to convey the idea of motion.