# Propagation Delay

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PD =
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ID
JustinLiller.Propagation Delay
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b24b1d79-e5d3-11e3-b7aa-bc764e2038f2

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.

#### The Math / Science

PD = ( A - B) / S

where:

• 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.