David Schwartz wrote:
>"Brad Knowles" wrote in message
>news:mailman.29.1111192970.588.questions@lists.ntp.isc.org...
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>>At 3:16 PM -0800 2005-03-18, David Schwartz wrote:
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>>> The assumption is that you have three servers, two of which are
>>>working
>>> and one of which is not. If two of them are working, then their
>>>intervals
>>> *must* overlap.
>>>
>>>
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>>They can't overlap, since it takes two machines to *define* an interval.
>>If you have three machines, you may have as many as two different
>>intervals. If one of those machines is insane, then you're back to the
>>well-known two-machine problem.
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> A machine reports a time of X and it reports its own accuracy as Y and
>the round trip time is Z. Why does this one machine not define an interval
>X+Y+Z to X-Y-Z?
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>>> Obviously if you have three servers and no two of them
>>>are
>>> reliable, you are screwed.
>>>
>>>
>>You're pretty much screwed if you have just three servers and any one of
>>them is unreliable.
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> I don't see why. Common sense say that if you have three servers and
>they report:
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>10:11
>10:11
>12:03
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> The time is probably 10:11.
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> DS
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Ummm.... When is the last time you saw two servers reporting exactly
the same time? The difference is usually in the range 0.5 to 40
milliseconds but it's there. If they do happen to agree, is it random
chance or do they both actually have the correct time?
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