[ntp:questions] synchronization distance

David Woolley david at ex.djwhome.demon.invalid
Sat Dec 4 19:10:42 UTC 2010

David L. Mills wrote:
> 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.

To a large extent I would agree with you, but the net effect of this is 
to say "if you work for a marketing led company (probably true of most 
of the Fortune 500), do not use NTP as it is almost certain that your IT 
department has a strict Microsoft policy for their core systems, and are 
not time synchronisation experts".
> 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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