Show understanding of circuit switching
14.2 Circuit Switching & Packet Switching 📞📦
What is Circuit Switching?
Think of a telephone call. When you pick up the phone, a dedicated path is created between you and the person you’re calling. This path stays open for the entire conversation, giving you a constant, guaranteed bandwidth. 📞
Key points:
- 🔗 A fixed route is established before data starts flowing.
- 🛡️ The route is reserved for the duration of the call.
- ⚡ Data travels at a constant rate; no sharing with other users.
- ❌ If the line is busy, you can’t start a new call until the current one ends.
Mathematically, the bandwidth \(B\) you get is constant: \(B = \text{fixed}\) for the whole session.
Exam Tip: Circuit Switching
When answering exam questions, remember to mention:
- Dedicated path creation.
- Guaranteed bandwidth.
- Potential inefficiency when the path is idle.
Use the phrase “dedicated circuit” to show you understand the concept.
Packet Switching 📦🌐
Now imagine sending a letter in multiple envelopes. Each envelope (packet) can take a different route to the destination, and they’re reassembled once they arrive. This is packet switching—the backbone of the internet.
- 📦 Packets are independent; they can share the same network links.
- 🚦 No fixed path—routers decide the best route each time.
- ⚖️ Bandwidth is shared; some packets may experience delays.
- 🛠️ Allows for error checking and re‑transmission if packets are lost.
Exam Tip: Packet Switching
Highlight:
- Dynamic routing.
- Shared bandwidth.
- Reliability features (re‑transmission, error correction).
Use the phrase “stateless packets” to show you grasp the concept.
| Feature | Circuit Switching | Packet Switching |
|---|---|---|
| Path Setup | Dedicated, fixed path established before data transfer. | No fixed path; each packet routed independently. |
| Bandwidth Allocation | Guaranteed, constant bandwidth. | Shared among all users; variable bandwidth. |
| Efficiency | Can be wasteful if the path is idle. | Highly efficient; resources shared. |
| Reliability | High, but no error checking per se. | Includes error detection and re‑transmission. |
Quick Review Questions
- What is the main difference between a dedicated circuit and a shared network?
- Why might circuit switching be less efficient for data that is sent intermittently?
- Explain how packet switching can recover from a lost packet.
Revision
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