Propagation Delay

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Equation / Last modified by KurtHeckman on 2018/10/24 00:24
JustinLiller.Propagation Delay

The Propagation Delay calculator compute the propagation delay based on the positions of two routers and the propagation speed.

INSTRUCTIONS: Choose units and enter the following:

  • (A) This is the position of router A on the network
  • (B) This is the position of router B on the network
  • (S) This is the propagation speed

Propagation Delay (PD): The calculator returns the delay in milliseconds (ms).  However this can be automatically converted to compatible units via the pull-down menu.

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The Math / Science

The formula for propagation delay is:

    PD = ( A - B) / S


  • PD is the propagation delay
  • A is the position of router A
  • B is the position of router B
  • S is the propagation speed

Once a bit is pushed into the link, it needs to propagate to router B. The time required to propagate from the beginning of the link to router B is the propagation delay. The bit propagates at the propagation speed of the link. The propagation speed depends on the physical medium of the link (that is, fiber optics, twisted-pair copper wire, and so on) and is in the range of `2*10^8 "meters/sec" to 3* 10^8 "meters/sec"` which is equal to, or a little less than, the speed of light. The propagation delay is the distance between two routers divided by the propagation speed.