Correlation between RTT and distance

Can anyone explain to 开发者_开发百科me the correlation between RTT and distance as well as how to calculate it please?

You mean physical distance in miles? There's no such correlation, not even an approximate one. RTT depends on the number of switchers and routers which are responsible for 99.99% of RTT, and their load. Otherwise signal travels at the light speed.

I realize this has been inactive for several years but I stumbled on it and thought I would help anyone else that lands here:

RTT (datagram round trip time) is certainly impacted by physical distance. we use the following equation to calculate the minimum RTT over the given distance of a P2P circuit:

minimum RTT is two times of the propagation delay on the link: minimum RTT = 2 * Distance / Speed of propagation

Keep in mind that the speed of propagation would be = the speed of light for an optical circuit (3*10^8 m/s) and that the distance used for the calculation should be in miles for all things to be balanced in the equation (or you can use the metric equation for light speed if you wish)

This is in fact a very important part of calculating actual throughput over a link for an individual TCP conn. That seems to be something few people grasp as even experienced network engineers will seem baffled at why they can't transfer data at "wirespeed" over a 200 mile optical circuit.

At any rate I hope this helps someone out there :)