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+8  Q: 

Theoretical minimum round-trip-time for a packet to travel over/under the North Atlantic Sea?

I'm doing some performance tuning and capacity planning for a low-latency application and have the following question:

What is the theoretical minimum round-trip time for a packet sent between a host in London and one in New York connected via optical fiber?

+7  A: 

I believe the index of refraction of fiber is around 1.5, and the internet reports it's around 5600 km from NY to London, so the theoretical minimum one-way is 5600 km / (c/1.5) =~ 28 ms. Round-trip is double that, 56 ms.

Up to you to do the real work of estimating latency through your routers and all.

P.S. The cables might not be straight :p

Edit: A bit of the wikipedia article on optical fiber pretty much contains all this information.

Jefromi  2010-03-16 17:56:04
The theoretical minimum round trip time is actually twice that, so 56ms. For comparison with reality: I'm in Belgium and www.nyi.net has a ping of 89ms for me. Surprisingly low isn't it!
Wim Coenen  2010-03-16 18:05:45
Oh, round-trip, my bad. Fixed!
Jefromi  2010-03-16 18:08:02

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