What is circuit switching?

All currently existing telecommunications network to provide the required functions can use two kinds of communication - circuit switching and (or) packages. What is it and how do they differ from one another?

Let's Start with how networks work switched. They appeared before their counterparts switched packets, so, not surprisingly, is more simple to implement. A vivid example of a network that uses circuit switching – a telephone line connection. It is obvious that in order for two parties can start communication, you must establish a connection between them. The initiating subscriber dials a number that is essentially a command to the telephone exchange equipment (PBX) located between them, properly connect the two lines – from the initiator and the Respondent (to take an example, when subscribers are served by one station). Previously used mechanical probes, the simplest position sensors, then, with the advent of digital solutions, the implementation has changed, although the principle remains the same. Circuit switching provides subscribers with an independent line, which remains assigned to them until the end of the session. The advantages are obvious: high reliability, no need to transmit control packets. However, this method of connection with the increase in the number of subscribers gets too wasteful, because the number of channels is physically limited. Even attempt to solve this problem by the use of seals is only a temporary measure, certain interim solution. Furthermore, circuit switching has one significant drawback-the line is busy all the time, even if the exchange of information between subscribers no. For example, during a telephone conversation you can hang up next to the machine and go about their business – the channel will be reserved for them until the go signal to break the connection.

That is why later on change the commutation channels came the way of packet switching. The principle of operation involves the encoding and splitting of the transmitted data stream into a number of separate packages according to a common communication line transmitted to the recipient and there merged into the original thread. To understand the differences of the two ways, you can use the analogy with the transmission line: when the switching line is represented by a train track, and the flow of data – part of the many cars. It is quite clear that EN route delays are extremely rare, and reliability one of the highest. At the same time, on the track at the same time I can't move several squads. But the lines with packet switching – highway with multilane traffic. The goods transported (transmitted packets) is divided into several machines which, moving in the flow of other types of transport reached its destination, where the Assembly of the original design. In this example, the road – is a communication channel, and the cars represent the packets of data. They peacefully coexist on the same road, almost not interfering with the movements of each other. Exceptions – congestion, traffic lights and emergency situation (this is delay). Even if a car has not arrived to the receiver, the copy request may be resubmitted. The total volume transferred per unit time information in packet-switching are significantly higher than in the case of channels.

In General, switching is a switching of something, changes. In the network technique, it generates a route for the passage of data. Feature is the way it is managed. Switching is not to be confused with the routing, which aims to find the optimal path.