[ntp:questions] synchronization distance

David L. Mills mills at udel.edu
Sat Dec 4 16:28:06 UTC 2010


David,

I'm not making myself absolutely crystal clear and you are obscuring the 
point.

Windows has an awesome protocol that sets the time. It happens to use 
the NTP packet header format, but is not otherwise compliant with the 
NTPv4 specification, especially the 36-h poll interval limitation, which 
is an engineering parameter based on the expected wander of a commodity 
crystal oscillator. All that doesn't matter at all, other than Windows 
servers are compatible with Windows clients. What does matter is that 
Windows servers are NOT compatible with NTPv4 clients, which SHOULD NOT 
BE USED. Use one of the SNTP variants instead.

As a diehard workaround, use the tos maxdist command to set the distance 
threshold to something really high, like ten seconds. There is nothing 
whatsoever to be gained by this, as the expected error with update 
intervals of a week will be as bad or worse than with SNTP..

Dave

David Woolley wrote:

> David L. Mills wrote:
>
>> BlackList,
>>
>> I say again with considerable emphasis: this is a Microsoft product, 
>> not the NTPv4 distribution that leaves here. What you see is what you 
>> get, 
>
>
> But it is often NTPv4 reference version that is used as the client and 
> fails to synchronize because the root dispersion is too high.
>
> Corporate politics are such that it is difficult to get a Unix system, 
> or even Windows running the reference version, near the root of the 
> time distribution  tree.  People deeper in the tree then see the 
> effects, even if they are using the reference implementation.
>
>> warts and all. I doubt it has anything to do with root distance, or 
>> any other public specification, but that doesn't make any difference 
>> if the customer is satisfied with the performance. Just don't compare 
>> it with anything in the NTP distribution, documentation or 
>> specification.
>>
>> Dave
>>
>> E-Mail Sent to this address will be added to the BlackLists wrote:
>>
>>> David L. Mills wrote:
>>>  
>>>
>>>> I had no idea somebody would try to configure current
>>>> NTPv4 with a poll interval of a week.
>>>> The current maximum allowed is 36 h.
>>>>   
>>>
>>>
>>> <http://technet.microsoft.com/en-us/library/cc773263%28WS.10%29.aspx>
>>> <BlockQuote>
>>> SpecialPollInterval
>>> This entry specifies the special poll interval in seconds
>>>  for manual peers. ...
>>> The default value on stand-alone clients and servers is 604,800.
>>> </BlockQuote>
>>>
>>> {7 days}
>>>
>>>
>>>  
>>>
>
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