Cambridge A-Level Computer Science (9618) · lesson 8 of 15 · 25 min
Circuit Switching
In circuit switching, a dedicated physical path is established between sender and receiver for the entire duration of the communication. Resources (bandwidth) are reserved exclusively for that connection.
Example: Traditional telephone (PSTN) networks. When you dial, a circuit is established through the exchange — no one else can use those resources until you hang up.
Advantages: Guaranteed bandwidth, constant latency, no congestion once connected.
Disadvantages: Wasteful if the circuit is idle (silence in a phone call), slow to set up, poor scalability.
Packet Switching
In packet switching, data is broken into packets. Each packet is routed independently through the network — different packets may take different paths and arrive out of order. The receiver reassembles them.
Example: The Internet. Every web request, email, and video stream uses packet switching.
Advantages: Efficient use of network resources (bandwidth shared), resilient to failures (packets reroute), scales to billions of devices.
Disadvantages: Variable latency (jitter), packets may arrive out of order, overhead from headers.
Comparison
In circuit switching, bandwidth is:
- Shared among all users
- Reserved exclusively for the connection
- Allocated dynamically
- Not required
- Answer: 1
Circuit switching reserves a dedicated path — bandwidth is not shared.
Why is packet switching more resilient than circuit switching?
- Packets are encrypted
- Packets can be rerouted around failures
- Packets are smaller
- Packet switching uses more bandwidth
Answer: Packets can be rerouted around failures
Each packet is routed independently — if one path fails, packets take alternative routes.
Which switching method does the Internet use?
- Circuit switching
- Packet switching
- Message switching
- Cell switching
Answer: Packet switching
The Internet is built on packet switching — TCP/IP breaks data into packets routed independently.
Previous lesson: Network protocols and the TCP/IP stack
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