Circuit Switching

Circuit switching is a telecommunications method where a dedicated communication path or circuit is established between two network nodes before they start exchanging data. This means that for the entire duration of the communication session, a unique channel is reserved solely for the two parties communicating, ensuring they have full access to the available bandwidth of that channel.

Imagine making a phone call; when you dial a number, the telephone network sets up a direct connection between your phone and the recipient's phone. This connection remains active and exclusive until the call ends. During this time, no other calls can use the same circuit; it is reserved exclusively for your conversation.

The key advantage of circuit switching is the consistent data transfer rate because the dedicated path remains constant throughout the session. This eliminates delays and interruptions, providing a steady and reliable communication line. For example, once the circuit is established, the bit delay remains constant, ensuring smooth and uninterrupted data flow.

One of the main applications of circuit switching was in traditional telephone networks. When you made a call, the network would create a continuous electrical circuit from your phone to the recipient's, maintaining this direct physical link for the call's duration. Even if there is silence on the line, the circuit remains dedicated and cannot be used for any other purpose.

However, circuit switching is relatively inefficient compared to other methods. The dedicated circuit cannot be shared, meaning that if there's no communication, the reserved bandwidth is wasted. Additionally, if any part of the circuit is disrupted, the call will be dropped, and the process of establishing a new connection must begin again.

Alternatives to circuit switching include message switching and packet switching. In message switching, entire messages are stored and forwarded one hop at a time, while packet switching divides data into packets that can travel over various paths to the destination. Packet switching is more efficient for data networks as it allows multiple communication sessions to share the same network links.

Examples of circuit-switched networks include the Public Switched Telephone Network (PSTN), where each call gets a dedicated circuit, and ISDN (Integrated Services Digital Network) B channels, which provide digital transmission over the traditional phone network.