Re: SAT-3 / WASC

[Brian Candler <B.Candler at pobox.com>]

On Sat, May 31, 2003 at 12:36:38PM -0700, S Woodside wrote:
> Here's a breakdown of the end traceroute from Europe, N.A., Australia 
> to the site. Note that the jump from BT's concert.net delay of 100 ms 
> to telkom where it's 274 ms delay. Only 175 ms increase - that's not a 
> satellite hop! The speed of light in fibre is about 200 000 000 m/s and
> 
> the SAT-3 is about 15 000 000 m long so that about 75 ms lost just to 
> the speed of light. I suppose the other 100 ms comes from the repeaters
> 
> or something.

Traceroute measures a round-trip delay: the total time for there and back.
(Or did you already double the SAT-3 length to take account of that?)

The other thing to consider if you see an odd-sized step in latency is
assymetric routing, e.g. perhaps fibre one way and satellite back the other.
If there's a looking-glass at the destination that can be helpful.

Cheers,

Brian.

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