There are two fundamental ways to move data in a network: circuit switching and packet switching. Circuit switching reserves resources before communication begins, whereas packet switching sends data without any prior reservation and shares network resources dynamically.
Difference: circuit switching is planned and dedicated, packet switching is on-demand and shared.
Resource Reservation vs On-Demand Use
In circuit-switched networks, bandwidth and buffers along the entire path are reserved for the full duration of the session. In packet-switched networks, no such reservation exists, so packets may experience queuing delays when the network is busy.
Difference: circuit switching guarantees resources, packet switching may cause waiting.
Reservation Analogy
A circuit-switched network is like a restaurant that requires reservations—> you prepare in advance and get immediate service. A packet-switched network is like a walk-in restaurant—> you can enter anytime but might have to wait.
Difference: circuit switching offers certainty, packet switching offers flexibility.
Telephone Networks as Circuit Switching
Traditional telephone networks use circuit switching. Before communication starts, a dedicated end-to-end circuit is established, and switches along the path maintain connection state.
Difference: circuit switching maintains a fixed connection, packet switching does not maintain per-session state in the network.
Guaranteed Transmission Rate
Once a circuit is established, a constant transmission rate is reserved on every link, ensuring steady data transfer throughout the session. Packet-switched networks cannot guarantee such a constant rate.
Difference: circuit switching provides guaranteed bandwidth, packet switching provides best-effort service.
Sharing Links Using Circuits
In a circuit-switched network, each link is divided into a fixed number of circuits, limiting the number of simultaneous connections. Packet-switched networks allow many users to share the same link dynamically.
Difference: circuit switching has fixed capacity per connection, packet switching has dynamic sharing.
Example of Fixed Bandwidth
If a 1 Mbps link has four circuits, each connection gets 250 kbps for the entire call, even if it is not fully used. In packet switching, bandwidth is used only when packets are transmitted.
Difference: circuit switching may waste unused bandwidth, packet switching uses bandwidth efficiently.
Packet Switching and Best Effort Delivery
In packet-switched networks like the Internet, packets are sent without reserving resources and may face delays due to congestion. The network makes no strict guarantees on delivery time or rate.
Difference: circuit switching guarantees performance, packet switching prioritizes scalability and efficiency
