COMPUTER NETWORKS!
A network is a system of interconnecting computers, which are located away from each other through a communication media like wire cable and other networking devices. The main goal of having a network is to achieve data communication between two devices. It can also be used to share the resources available in system with others. Examples for resources available with a computer are: CPU, memory, printers and files.
Data Communication:
This is a process of exchanging the data, a valuable resource in any network, between two devices via some form of transmission media such as wire cable or optical fiber. The data available in a computer may be of different forms which include text, numbers, images, audio and video. In networks, data communication takes place with the help of communication devices, which are made up of hardware (physical equipment) and software (programs).
The effectiveness of a data communication system depends on four fundamental characteristics: Delivery, Accuracy, Timeliness and Jitter.
Delivery: This characteristic refers to the probability of data delivered to the correct destination. The sent data must be received by the intended device or user and only by it.
Accuracy: It refers to the possibility of sending the data accurately between two systems. Data that have been altered in transmission and left uncorrected are unusable.
Timeliness: This characteristic determines the timely delivery of data in its transmission. 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: It refers to the variation in the packet arrival time. It is the uneven delay in the delivery of audio or video data. For e.g., let us assume that video packets arrive at a time delay of 30 ms. If some packets take 40 ms for their arrival, it results in an uneven quality in the video.
Components of a Network:
A network – a carrier for data communication, comprises of five major components namely message, sender, receiver, transmission media and protocol. They are explained with a picture as follows:
Message: The message is the information to be communicated. It may be in any one of the five popular formats: text, numbers, pictures, audio and video.
Sender: The sender is the device that sends the message. It can be a computer, a telephone handset, video camera and so on.
Receiver: The receiver is the device that receives the message. It can be a computer, a telephone handset, video camera and so on.
Transmission Media: It is the physical path by which a message travels from the sender to the receiver. Some examples of transmission media include twisted-pair cable, coaxial cable, fiber-optic cable and radio waves.
Protocol: A protocol is a set of rules that govern data communication. It represents an agreement between the communication devices. It is in both abstract and concrete forms. Logically, a protocol is defined as a set of rules, but physically it is implemented either in hardware or software.
Fig.: Five components of a network
Without a protocol, two devices may be connected but not communicating the data across. For two devices to communicate successfully, they must speak the same language. The protocol specifies the rules for what is communicated, how it is communicated, and when it is communicated between two devices.
The key elements of a protocol are as follows:
Syntax: Includes such things as data format and signal levels.
Semantics: Includes control information for coordination and error handling.
Timing: Includes speed matching and sequencing.
