Delays in Computer Networks and Communication Formulas with Examples – Transmission, Propagation, Processing, and Queuing Delay

In this article, you will learn about the different types of Delays in Computer Networking and Communications, along with formulas to better understand the topic.

Communication Formulas with Examples

What is a Delay in Computer Communication?

In computer communication and networking, a packet must go from the sender to the receiver. A packet travels from a source and passes through routers, switches, and hubs before reaching its destination. Going from one node, such as a Host or Router, to another takes time, which is the Delay we will discuss in this article.

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Types of Delays in Computer Communication

In this article, we will discuss the four main types of delays in computer communication:

  • Transmission Delay
  • Propagation Delay
  • Queuing Delay
  • and Processing Delay

1- Transmission Delay

Transmission Delay is the time that every bit of a packet takes onto the outbound link. In the formula below, R is for transmission rate/bandwidth, and L is the size of the packet being sent.

The formula for Transmission Delay is

Ttrans = L / R

Example of Transmission Delay

What is the transmission delay if the bandwidth is 5 Mbps and the number of bytes in the packet is 2000?

Ttrans =L / R = (2 × 8× 10-3)/5 = 0.0032 seconds or 3.2 milliseconds.

2- Propagation Delay

The Propagation delay is the time that requires a single bit to travel from a link to the destination. In computer communication, when a bit is transmitted onto the link, it has to propagate through a transmission medium to reach the destination.

The distance between the sender and receiver plays a role in calculating the propagation delay and the link’s propagation speed. In the formula below, the distance between the sender and the destination receiver is D, while the propagation speed of the link is S.

The formula for Transmission Delay is:

Tprop = D / S

To calculate the propagation speed, we should know the medium of the link between the sender and receiver. For example, the propagation speed of optical fiber is 2.1 X 108 ms

Example of Propagation Delay

In an optical fiber link, find the Delay of the packet to travel 2500 KM to reach the destination.

Tprop = D/S = 2500×106/ 2.1×108 = seconds or milliseconds.

3- Queuing Delay

After a packet reaches the destination, it will be placed in a queue before it gets processed. For many reasons, packets are placed in the buffer until other packets are cleared.

The queuing Delay is the time required for a packet to stay in the buffer, which varies from one packet to another. Thus, there is no specific formula to calculate it.

4 – Processing Delay

The last important type of Delay in computer communication is the processing delay, which is the time the processor needs to process a packet. The processor inspects the packet, determines the destination, and checks bit-level error before processing a packet, which sums up the processing delay.

Like queueing Delay, the processing delay does not have a formula as it depends on the processor speed.

Nodel Delay

The nodal Delay is the sum of all four delays:

Tnodal = Ttrans + Tprop + Tqueue + Tproc

Some networks have negligible Nodel delay, such as fiber optic networks, while others may face significant delays. The network architecture plays a role in increasing and decreasing the Delay, and it’s essential to design and architect your network carefully to avoid significant delays and packet loss.


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