Switching Techniques (Circuit, Packet)

1. Circuit Switching

A dedicated communication path is established between sender and receiver BEFORE any data is transmitted. The path remains exclusively reserved for the entire duration of the communication, regardless of whether data is actively being sent.

• Example: Traditional telephone networks (PSTN). When you call someone, a physical circuit is established through the switches for the duration of the call.
• Pros: Guaranteed bandwidth, constant latency, no congestion once established.
• Cons: Extremely wasteful. If you pause during a phone call, the circuit is idle but still reserved. Resources are blocked even when no data flows.

2. Packet Switching

Data is broken into small chunks called Packets. Each packet is individually routed through the network. Different packets from the same message may take different paths. The network is shared among all users.

• Example: The Internet. Every web page, email, and video stream is broken into packets.
• Pros: Efficient resource utilization (bandwidth is shared). Robust (if one path fails, packets are rerouted).
• Cons: Variable latency (packets may arrive out of order). Possible congestion during peak usage.

Store-and-Forward

Each intermediate router receives the entire packet, stores it in a buffer, checks it for errors, and then forwards it to the next hop. This adds latency but ensures data integrity.

Cut-Through Switching

The switch begins forwarding the packet as soon as it reads the destination address (before receiving the entire frame). Lower latency but cannot detect corrupted frames before forwarding.

3. Message Switching

The entire message is sent as a single unit (no fragmentation). Each intermediate node stores the entire message until the next link is free. Essentially "store-and-forward" at the message level.

• Cons: Requires massive storage at intermediate nodes. Very high latency. Largely obsolete.

4. Comparison