[ntp:questions] Re: The asymmetry strikes again!
David J Taylor
david-taylor at blueyonder.co.not-this-bit.nor-this-part.uk.invalid
Wed Jul 20 16:06:16 UTC 2005
Matt Kinard wrote:
> I'm still researching NTP issues over an asymmetric network, and I was
> wondering if I could get some suggestions as to what sort of accuracy
> I'm looking at sacrificing.
>
> Are we talking 20 ms or are we talking about 1 or 2 seconds? Is it
> contingent upon how asymmetric my network is? What is the threshold?
>
> For the particular application I'm studying, there is some acceptable
> risk in terms of lost accuracy, but I need some more concrete ideas.
How asymmetrical is the network you are considering? I think you will
need to know that to answer the question.
FWIW: I saw one NTP server in Europe which had an asymmetrical path to its
reference source in the US. The error was (I can't remember) either the
full difference on the send and receive times or half the difference. One
path was via satellite and one via landline, I believe, so the offset was
less than 100ms.
(You might ask, as I did: why did NTP prefer the server with the greater
network distance, and why didn't the operators of the server use European
sources).
Cheers,
David
More information about the questions
mailing list