Delays in Computer Networks | Formulas

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Delays in Computer Networks-



  • 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.



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




2. Propagation Delay-


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



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




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-




Total delay in sending one data packet or End to End time

= Transmission delay + Propagation delay + Queuing delay + Processing delay




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.




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.




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




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

(Remember while solving numerical problems)




  • 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


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Delays in Computer Networks | Formulas
Article Name
Delays in Computer Networks | Formulas
Delays in Computer Networks- There are different types delay in computer networks- Transmission delay, Propagation delay, Queuing delay and Processing delay. These delays are discussed with their formula.
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Gate Vidyalay
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