---
title: "Circuit vs packet switching"
subject: "Computer Networks and Security"
chapter: 2
key: "semester_7/computer_networks_and_security:circuit-vs-packet-switching"
source: https://www.bctengineer.com/q/semester_7/computer_networks_and_security/circuit-vs-packet-switching
site: BCT Engineering
---

# Circuit vs packet switching

Computer Networks and Security · Chapter 2: Physical Layer

- Asked in: 2074 Asoj, 6 marks; 2074 Chaitra, 4 marks; 2069 Chaitra, 4 marks (asked 3 times)
- Video: [Circuit Switching vs Packet Switching](https://www.youtube.com/watch?v=G7n8thqwO2c) — PowerCert Animated Videos
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_7/computer_networks_and_security/circuit-vs-packet-switching
- Whole chapter: https://www.bctengineer.com/md/semester_7/computer_networks_and_security/chapter-2

## Question

Differentiate between circuit switching and packet switching.

## Short answer

Circuit switching sets up a dedicated path before transfer, guaranteeing constant delay but wasting bandwidth when idle. Packet switching breaks data into packets that share links dynamically, giving efficient use but variable delay and possible out-of-order delivery.

## Answer

In **circuit switching** a dedicated path is set up between sender and receiver before data transfer and held until the call ends (telephone network). In **packet switching** the message is broken into packets that are sent independently and share links on demand (Internet).

| Point | Circuit switching | Packet switching |
|---|---|---|
| Path | Dedicated physical path for the whole session | No dedicated path; each packet is routed separately |
| Phases | Setup, data transfer, release | No setup in datagram; setup only in virtual circuit |
| Bandwidth | Reserved, wasted when idle | Shared dynamically, efficient use |
| Delay | Setup delay, then constant and small | Variable delay (queuing at routers) |
| Order of data | Always in order | May arrive out of order (datagram) |
| Congestion | Call blocked at setup time | Packets delayed or dropped |
| Store and forward | No | Yes |
| Reliability | If a node fails the call is lost | Packets can be rerouted |
| Suitable for | Real-time voice | Data (bursty traffic) |
| Header overhead | None after setup | Each packet has a header |
| Example | PSTN | Internet, X.25, Frame Relay |

## Check yourself

The answer's key points as multiple-choice questions, with the correct option and why.

1. Which statement about the path is correct?
   A. Circuit: dedicated path for whole session; packet: each packet routed separately
   B. Circuit: each packet routed separately; packet: dedicated path
   C. Both use dedicated paths
   D. Neither uses paths
   Answer: A. Circuit switching reserves a path; packet switching shares links. (Key point: Path)

2. Which is more bandwidth-efficient for bursty data, and why?
   A. Circuit, because bandwidth is reserved
   B. Packet, because bandwidth is shared dynamically
   C. Circuit, because of store and forward
   D. Neither
   Answer: B. Reserved circuit bandwidth is wasted when idle, whereas packet switching shares links on demand. (Key point: Bandwidth use)

3. Which pair is right?
   A. Circuit: variable delay, out of order; packet: constant delay, in order
   B. Circuit: setup delay then constant, in order; packet: variable delay, may be out of order (datagram)
   C. Both identical
   D. Packet has no queuing
   Answer: B. Circuit gives constant small delay after setup and in-order data; packet has queuing delays and possible reordering. (Key point: Delay and ordering)

4. Which pairs examples correctly?
   A. Circuit: Internet; Packet: PSTN
   B. Circuit: PSTN; Packet: Internet, X.25, Frame Relay
   C. Both: PSTN
   D. Both: Internet
   Answer: B. PSTN uses circuit switching; the Internet, X.25 and Frame Relay use packet switching. (Key point: Examples)

## Related in Computer Networks and Security

- [Virtual circuit switching](https://www.bctengineer.com/question.md?key=semester_7%2Fcomputer_networks_and_security%3Avirtual-circuit-switching) — Computer Networks and Security, chapter 2

## Related in other subjects

- [Circuit vs packet switching](https://www.bctengineer.com/question.md?key=semester_5%2Fdata_communication%3Acircuit-vs-packet-switching) — Data Communication, chapter 7, asked 4×
- [Switching, circuit vs packet, X.25 layers](https://www.bctengineer.com/question.md?key=semester_5%2Fdata_communication%3Aswitching-define-compare-x25-layers) — Data Communication, chapter 7
- [Packet vs message switching](https://www.bctengineer.com/question.md?key=semester_5%2Fdata_communication%3Apacket-vs-message-switching) — Data Communication, chapter 7
- [Circuit switch vs packet switch](https://www.bctengineer.com/question.md?key=semester_8%2Ftelecommunications%3Acircuit-vs-packet-switch) — Telecommunications, chapter 8