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Re: Transatlantic response times.
### On Mon, 25 Mar 2002 09:13:20 -0600, "Pistone, Mike" ### <[email protected]> casually decided to expound upon ### "'[email protected]'" <[email protected]> the following thoughts about ### "Transatlantic response times.": MP> I was curious if anybody would share what they consider to be average or MP> acceptable transatlantic ping response times over a T1. MP> I know there are tons of variables here, but I am looking for ballpark MP> figures. MP> Assume that utilization on the circuit is extremely low, and you are MP> measuring point to point across the line. You can also assume no other MP> bottlenecks effecting the response times (router performance, or what not). MP> Should you see a ~150ms trip? 250ms? 450ms??? Well, I've been seeing around 70ms (+/- 5ms) RTT pings from NYC to LON across AC-1 (Global Crossing) as normal. Granted this is on an OC-48 but bandwidth should not matter much to RTT if the load is light and all you're measuring is ICMP ping. MP> Is there any equation to estimate response times? For example, if your MP> circuit from A to Z has a 500ms avg response, than that equates to a circuit MP> distance of aprox. 5000 miles or something? Assuming you exclude switching latency in the hardware, latency induced by regenerators, etc... spead of light in a medium is a simple distance-rate-time equation with a slight twist: c = nL/t, where n is the refractive index, L is the length, and t is the transmission time difference (double this for RTT). The rest is just simple math. So expected one way time should be: t = nL/c Note -- I believe most fiber optic cables have a refractive index somewhere on the order of 1.4. -- /*===================[ Jake Khuon <[email protected]> ]======================+ | Packet Plumber, Network Engineers /| / [~ [~ |) | | --------------- | | for Effective Bandwidth Utilisation / |/ [_ [_ |) |_| N E T W O R K S | +=========================================================================*/