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

Question

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?

Colure

How many routers? How fast are the routers? Or are you asking about the speed of a signal through copper wire? – Laritalariviere

I think you might need some definition of "theoretical". I'm guessing you're probably not allowed to lay your own cable and put your application on computers hooked up directly to it. – Barncard

@Jefromi: You can hope, but the question doesn't say, making it hard to answer. – Laritalariviere

@S.Lott: What I mean is, anything built in "modern" times uses fiber, not wire. – Barncard

Yes, it's fiber :-) I've updated the question with that assumption. – Colure

Aside: 1 foot/ns is a decent approximation to the speed of light in vacuum. Both wire and fiber have effective indexes of refraction around 1.5, giving 8 inches/ns at the physical layer. Useful thing to know when you're wiring up plug-board computers. – Philanthropic

Answer 1

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.

Barncard

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! – Shafting

Oh, round-trip, my bad. Fixed! – Barncard

Answer 2

Just ask Hibernia, they currently are at 72ms and presently looking at 60ms by mid-2012.

http://www.a-teamgroup.com/article/andrews-blog-laying-cable-and-the-low-latency-gauntlet/

Aquiculture

Link is dead and unavailable in The Wayback Machine :( – Buddy