A switched network consists of a series of interlinked switches. Switches are hardware/software devices capable of creating temporary connections between two or more devices to the switch but not to each other. Switching mechanisms are generally classified into three methods: circuit switching , packet switching and message switching.





1. Circuit Switching.
==============
It creates a direct physical connection between two devices such as telephones or computers. Once a connection is made between two systems, circuit switching creates a dedicated path between two end users. The end users can use the path for as long as they want.


2. Packet Switching.
===============
It is one way to provide a reasonable solution for data transmission. In a packet-switched network, data are transmitted in discrete units of variable-length blocks called packets. Each packet contains not only data, but also a header with control information. The packets are sent over the network node to node. At each node, the packet is stored briefly before being routed according to the information in its header.
In datagram approach to packet switching, each packet is treated independently of all others as though it exists alone. In the virtual circuit approach to packet switching, if a single route is chosen between sender and receiver at the beginning of the session, all packets travel one after another along that route. Although these two approaches seem the same, there exists a fundamental difference between them. In circuit switching, the path between the two end users consists of only one channel. In the virtual circuit, the line is not dedicated to two users. The line is divided into channels and each channel can use one of the channels in a link.


3. Message Switching.
================
It is known as the store and forwarding method. In this approach, a computer (or a node) receives a message, stores it until the appropriate route is free, then sends it out. This method has now been phased out.