Data Communications

"Notes of Computer Networks"

Things to remember before going on computer networks To understand the concept of networking or network, first we have to understand the concept of data communications. Because the main purpose of the network is to transmit the data between all the computers connected to the network. To fully grasp about the network, we must understand the data communication components, how data can be represented in various form, and how to create a data flow. Data communications between the remote parties can be established through the process networking, by involving the connection of computers, networking devices, media etc. Mainly there are two types of networks: Local Area Networks(LANs) and Wide Area Networks(WANs). These two types of networks have distinct characteristic and different functionalities.  Protocols and standards are other two main components of computer network and are vital to the implementation of data communications and networking. Protocols refers to the rules and standard is a protocol that has been adopted by the vendors and manufacturers.Network models serve to organize, unify, and control the hardware and software components of data communications and networking.

Data Communications While we communicate, we are sharing something i.e, information. This sharing can be local or remote. Between individuals, local communications usually takes places face to face, while remote communication occurs over distance. The term telecommunication(taken from Greek word tele : "far"), which includes telephony, telegraphy, and television, means communication at a distance. The word data refers to information presented in whatever from which is shared among the networking devices connected to the networks. Data communication is the process of exchange of data between two devices through some form of transmission medium such as a wire cable. For data communications to occur, the communicating devices must be the part of the communication system made up of a combination of hardware (physical equipment) and software (programs). The effectiveness of the data communication system depends on four major and fundamental characteristics; delivery, accuracy, timeliness and jitter. Delivery: The system must deliver the 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 the data in a timely manner. Data delivered late are useless. In the case of video and audio, timely delivery means delivering data as soon as they are produced, in the same order that they are produced, and without any 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 consider 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.