Switching in Computer Networks

Whenever we have multiple devices, we have the problem of how to connect them to make one-to-one communication possible. One solution is to establish point-to-point connection between each pair of devices using mesh topology. However, mesh topology is impractical for large number of devices, because the number of links increases exponentially with number of systems. That means we need n(n-1)/2 connections to establish a mesh networks with n systems. A better alternative is the use of switched network. In this model, the network consists of a set of interconnected nodes among which information are transmitted from source node to destination node through different routes, which is controlled by the switching mechanism. A switched network consists of a series of interlinked nodes, called switches. There exist three methods of switching techniques: circuit switching, packet switching, and message switching.

Taxonomy of switched Networks

Circuit Switching

Circuit switching creates a direct physical connection between two devices, such as computers or phones. A circuit-switched network is made of a set of switches connected by physical links, in which each link is divided into n channels. The circuit switching process involves three main activities,

1.     circuit establishment

2.     Data transfer

3.     Circuit disconnect

Thus, the actual physical connection between the source and destination host must be established before the data is transmitted. The connection ones established remains exclusively and continue for the entire duration of data exchange and the circuit becomes disconnected only when sender wants so.

The three phases are also known as setup phase, data transfer phase and teardown phase respectively. Circuit switched networks are not as efficient as the other two types of networks because resources are allocated during the entire duration of the connection. This may cause resource wastage. The delay in this type of network is minimal. Traditional telephone systems are use circuit switching in physical layer.

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