About switching techniques - Librarians Portal

There are three major forms of switching techniques used in telecommunication networks

1) Circuit Switching

2) Packet Switching

3) Cell Switching

Circuit switching is the oldest technique and has been in existence for over 120 years. Packet switching is about 50 years old. Cell switching is the most recent one evolved during mid 1990s.

A channel is defined as an information pipe with some specified characteristics like bandwidth, capacity, level of attenuation and noise immunity. A channel is a one-way link.

A circuit is a two-way link and comprises two channels that enable two-way information flow between two entities.

circuit switching, a circuit, i.e.,, channels both ways, is established between the source and destination entities before information transfer begins. In other words an end-to-end connection is established first. Here, the network causes no delay and only propagation delay is experienced in information transfer. Hence, circuit switching is ideally suited for real time services.

Packet switching is a switching technique in which large size data is broken as packets and transferred across networks. It is a special form of a broader class of switching known as Store & Forward (S&F) switching. S&F switching is precisely what is practised in the postal system. The switching nodes store user messages, analyse destination addresses (sorting) and forward the sorted messages on different output links towards the intended destination. It is more flexible and allows more efficient use of network resources.

 Cell switching is a switching technique in which information is cast in the form of small cells and transported over broadband ISDN networks. It combines the desirable aspects of both circuit and packet switching. It is designed to cause minimal network delay ensuring at the same time efficient utilisation of network resources. Cell switching is extremely fast and works on a very reliable network infrastructure. Reliable infrastructure reduces the S&F overheads and increases the speed of switching. For this reason, cell switching is sometimes called fast packet switching.