Delays in Computer Networks | Formulas

Delays in Computer Networks-

 

Consider-

• Two hosts A and B are connected over a transmission link / transmission media.
• A data packet is sent by the Host A to Host B.

 

Following different types of delay occur during transmission-

 

 

1. Transmission delay
2. Propagation delay
3. Queuing delay
4. Processing delay

 

1. Transmission Delay-

 

Time taken to put the data packet on the transmission link is called as transmission delay.

 

Mathematically,

• Transmission delay ∝ Length / Size of data packet
• Transmission delay ∝ 1 / Bandwidth

 

Thus,

 

2. Propagation Delay-

 

Time taken for one bit to travel from sender to receiver end of the link is called as propagation delay.

 

Mathematically,

• Propagation delay ∝ Distance between sender and receiver
• Propagation delay ∝ 1 / transmission speed

 

Thus,

 

3. Queuing Delay-

 

Time spent by the data packet waiting in the queue before it is taken for execution is called as queuing delay.

 

• It depends on the congestion in the network.

 

4. Processing Delay-

 

Time taken by the processor to process the data packet is called as processing delay.

 

• It depends on the speed of the processor.
• Processing of the data packet helps in detecting bit level errors that occurs during transmission.

 

Important Points-

 

Note-01:

 

Total delay in sending one data packet or End to End time = Transmission delay + Propagation delay + Queuing delay + Processing delay

 

Note-02:

 

In optical fibre, transmission speed of data packet = 2.1 x 108 m/sec

 

• In optical fibre, signals travel with 70% speed of light.

70% speed of light

= 0.7 x 3 x 10⁸ m/sec

= 2.1 x 10⁸ m/sec

• So, consider transmission speed = 2.1 x 10⁸ m/sec for calculations when using optical fibre.

 

Note-03:

 

Both queuing delay and processing delay are dependent on the state of the system.

 

This is because-

• If destination host is busy doing some heavy processing, then these delays will increase.
• If destination host is free, then data packets will be processed immediately and these delays will decrease.

 

Note-04:

 

• For any particular transmission link, bandwidth and transmission speed are always constant.
• This is because they are properties of the transmission medium.

 

Note-05:

 

Bandwidth is always expressed in powers of 10 and data is always expressed in powers of 2.

(Remember while solving numerical problems)

 

Examples-

 

• 1 kilo bytes = 2¹⁰ bytes
• 1 kilo bits = 2¹⁰ bits
• 1 Mega bytes = 2²⁰ bytes
• 1 kilo bytes per second = 10³ bytes per second
• 1 kilo bits per second = 10³ bits per second
• 1 Mega bytes per second = 10⁶ bytes per second

 

To gain better understanding about delays in computer networks,

Watch this Video Lecture

 

Next Article- Types Of Channels in Computer Networks

 

Get more notes and other study material of Computer Networks.

Watch video lectures by visiting our YouTube channel LearnVidFun.