Making one-to-one communication between multiple devices is a big concern of computer network. Point-to point connection between each pair of device or with a central device can be the solution for that problem. But this is totally impractical and costly for a very large network. As well as other typologies are ruled out because the distance between devices and the total number of devices increase beyond the capacities of the media and equipment Switching is the better solution for this problem.
These are:
Circuit switching, message switching and packet switching.
Circuit switching
In this technique, first the complete physical connection between two computers is established and then data are transmitted from the source computer to the destination computer. That is, when a computer places a telephone call, the switching equipment within the telephone system seeks out a physical copper path all the way from sender telephone to the receiver’s telephone. The important property of this switching technique is to setup an end-to-end path (connection) between computers before any data can be sent.
Packet Switching
With message switching, there is no limit on block size, in contrast, packet switching places a tight upper limit on block size. A fixed size of packet which can be transmitted across the network is specified. Another point of its difference from message switching is that data packets are stored on the disk in message switching whereas in packet switching, all the packets of fixed size are stored in main memory. This improves the performance as the access time (time taken to access a data packet) is reduced, thus, the throughput (measure of performance) of the network is improved.
Message switching:
In this technique, the source computer sends data or the message to the switching office first, which stores the data in its buffer. It then looks for a free link to another switching office and then sends the data to this office. This process is continued until the data are delivered to the destination computers. Owing to its working principle, it is also known as store and forward. That is, store first (in switching office), forward later, one jump at a time.
