---
title: "Circuit switch vs packet switch"
subject: "Telecommunications"
chapter: 8
key: "semester_8/telecommunications:circuit-vs-packet-switch"
source: https://www.bctengineer.com/q/semester_8/telecommunications/circuit-vs-packet-switch
site: BCT Engineering
---

# Circuit switch vs packet switch

Telecommunications · Chapter 8: Data Communication

- Asked in: 2075 Chaitra, 4 marks
- 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_8/telecommunications/circuit-vs-packet-switch
- Whole chapter: https://www.bctengineer.com/md/semester_8/telecommunications/chapter-8

## Question

Differentiate between circuit switch and packet switch.

## Short answer

Circuit switching sets up a dedicated fixed path for the whole call, reserving bandwidth, and is best for real-time voice. Packet switching breaks data into packets, uses store-and-forward with shared links, and is efficient for bursty data. Examples: PSTN versus Internet IP.

## Answer

In a **circuit switch** a dedicated end-to-end path is set up for the whole call, as in the PSTN. In a **packet switch** data is broken into packets that share links and are stored and forwarded at each node, as in the Internet.

| Point | Circuit switching | Packet switching |
|---|---|---|
| Path | Dedicated, fixed for whole call | Shared; per packet or per VC |
| Set-up | Call set-up needed | None (datagram) or VC set-up |
| Bandwidth | Reserved, wasted in silence | Used on demand, efficient |
| Delay | Only at set-up; then fixed, low | Queuing delay at each node, variable |
| Store and forward | No | Yes |
| Congestion effect | Call blocked (busy tone) | Packets delayed or dropped |
| Billing | By time and distance | By data volume |
| Speed/code conversion | Not possible | Possible |
| Best for | Real-time voice | Bursty data |
| Example | PSTN, GSM voice | Internet (IP), X.25 |

```text
Circuit:  A ==[S1]==[S2]==[S3]== B   (one fixed path)
Packet:   A --[S1]--[S2]-------- B
               \     /
                [S4]                 (packets may differ)
```

## Check yourself

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

1. Why is circuit switching less efficient for bursty data than packet switching?
   A. It uses store and forward at each node
   B. Reserved bandwidth is wasted during silence or idle periods
   C. It has variable queuing delay
   D. It breaks data into packets
   Answer: B. A circuit reserves bandwidth for the whole call even when idle; packet switching uses links on demand. (Key point: Bandwidth use)

2. What happens under congestion in each technique?
   A. Circuit: packets dropped; packet: call blocked
   B. Both block the call
   C. Circuit: call blocked (busy tone); packet: packets delayed or dropped
   D. Neither is affected
   Answer: C. A circuit network refuses new calls when no path is free, while a packet network queues or drops packets. (Key point: Congestion behaviour)

3. Which statement about delay is correct?
   A. Circuit: delay at set-up then fixed and low; packet: queuing delay at each node, variable
   B. Circuit: variable queuing delay; packet: fixed delay
   C. Both have identical delay
   D. Packet switching has no delay since there is no set-up
   Answer: A. Once set up, a circuit gives fixed low delay; packets wait in queues at each node so delay varies. (Key point: Delay characteristics)

4. Which pairing of technique with best use is correct?
   A. Circuit - bursty data; packet - real-time voice
   B. Circuit - real-time voice; packet - bursty data
   C. Packet - billing by time and distance
   D. Circuit - billing by data volume
   Answer: B. Circuit switching suits real-time voice (PSTN); packet switching suits bursty data (Internet). (Key point: Best use)

## Related in Telecommunications

- [Datagram vs virtual circuit switching](https://www.bctengineer.com/question.md?key=semester_8%2Ftelecommunications%3Adatagram-vs-virtual-circuit) — Telecommunications, chapter 8
- [Marconi transmitter, mobile vs nomadic, Telecom Act](https://www.bctengineer.com/question.md?key=semester_8%2Ftelecommunications%3Amarconi-mobile-nomadic-act) — Telecommunications, chapter 1
- [TST vs STS and three-stage design](https://www.bctengineer.com/question.md?key=semester_8%2Ftelecommunications%3Atst-sts-design-crosspoints) — Telecommunications, chapter 4
- [Multistage switching; TST vs STS](https://www.bctengineer.com/question.md?key=semester_8%2Ftelecommunications%3Amultistage-tst-sts-compare) — Telecommunications, chapter 4
- [Telephone exchange structure; TST vs STS](https://www.bctengineer.com/question.md?key=semester_8%2Ftelecommunications%3Aexchange-structure-tst-sts) — Telecommunications, chapter 4
- [Space and time switches; STS vs TST](https://www.bctengineer.com/question.md?key=semester_8%2Ftelecommunications%3Aspace-time-switch-sts-tst) — Telecommunications, chapter 4

## Related in other subjects

- [Circuit vs packet switching](https://www.bctengineer.com/question.md?key=semester_7%2Fcomputer_networks_and_security%3Acircuit-vs-packet-switching) — Computer Networks and Security, chapter 2, asked 3×
- [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
- [BJT as a switch in power circuit](https://www.bctengineer.com/question.md?key=semester_7%2Fpower_electronics%3Abjt-as-power-switch) — Power Electronics, chapter 1, asked 2×