---
title: "Causes of packet delay"
subject: "Computer Networks and Security"
chapter: 1
key: "semester_7/computer_networks_and_security:packet-delay-causes"
source: https://www.bctengineer.com/q/semester_7/computer_networks_and_security/packet-delay-causes
site: BCT Engineering
---

# Causes of packet delay

Computer Networks and Security · Chapter 1: Introduction to Computer Network

- Asked in: 2074 Asoj, 2 marks
- Video: [Delays in Computer Networks || Lesson 55 || Computer Networks || Learning Monkey ||](https://www.youtube.com/watch?v=dA4Bwz0gXQI) — Wisdomers - Computer Science and Engineering 
- 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/packet-delay-causes
- Whole chapter: https://www.bctengineer.com/md/semester_7/computer_networks_and_security/chapter-1

## Question

What are the causes of packet delay in computer networks?

## Short answer

Packet delays are processing, queuing, transmission (L/R), and propagation (d/s). Nodal delay is their sum. For example, a 1000-byte packet on a 1 Mbps link has 8 ms transmission delay.

## Answer

A packet passing through a network suffers four kinds of delay at each node. Total nodal delay is the sum of these.

1. **Processing delay:** time to examine the packet header, check for bit errors and decide the output link. It is usually microseconds.
2. **Queuing delay:** time the packet waits in the output buffer before transmission. It depends on traffic load and varies; heavy congestion makes it large.
3. **Transmission delay:** time to push all bits of the packet onto the link = L/R, where L is packet length in bits and R is link rate in bps.
4. **Propagation delay:** time for a bit to travel along the link = d/s, where d is link length and s is propagation speed (about 2 × 10⁸ m/s in cable).

**d_nodal = d_proc + d_queue + d_trans + d_prop**

For example, a 1000-byte packet on a 1 Mbps link has a transmission delay of 8000/10⁶ = 8 ms.

## Check yourself

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

1. Which four delays make up total nodal delay?
   A. Processing, queuing, transmission, propagation
   B. Encoding, routing, framing, switching
   C. Setup, release, hold, transfer
   D. Processing, encryption, queuing, compression
   Answer: A. d_nodal = d_proc + d_queue + d_trans + d_prop. (Key point: Delay components)

2. What is the transmission delay formula and its meaning?
   A. d/s: link length over propagation speed
   B. L/R: packet length in bits over link rate
   C. Always microseconds
   D. Depends on traffic load
   Answer: B. Transmission delay = L/R, the time to push all bits onto the link; d/s is propagation delay. (Key point: Transmission delay)

3. A 1000-byte packet on a 1 Mbps link has what transmission delay?
   A. 1 ms
   B. 8 ms
   C. 80 ms
   D. 0.8 ms
   Answer: B. L = 8000 bits, R = 10^6 bps, so 8000/10^6 = 8 ms. (Key point: Transmission delay calculation)

## Related in Computer Networks and Security

- [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×
- [How packet filtering firewall works](https://www.bctengineer.com/question.md?key=semester_7%2Fcomputer_networks_and_security%3Apacket-filtering-firewall) — Computer Networks and Security, chapter 8
- [Five uses of networks in daily life](https://www.bctengineer.com/question.md?key=semester_7%2Fcomputer_networks_and_security%3Anetworks-in-life) — Computer Networks and Security, chapter 1
- [What is a computer network](https://www.bctengineer.com/question.md?key=semester_7%2Fcomputer_networks_and_security%3Acomputer-network-definition) — Computer Networks and Security, chapter 1

## Related in other subjects

- [Queuing theory in delay systems](https://www.bctengineer.com/question.md?key=semester_8%2Ftelecommunications%3Aqueuing-theory-delay-systems) — Telecommunications, chapter 6