[ntp:questions] ntp polling interval-- difference between NTP3 and 4?

Danny Mayer mayer at ntp.isc.org
Thu Feb 21 04:16:48 UTC 2008

Unruh wrote:
> There seems to be a conflict between ntp 3 and ntp 4 in the handling of the
> polling interval if the server does not respond. In the rfc for ntp 3 it
> says that the polling interval decreases if the server does not respond,
> while ntp 4 rfc  states 
> A client SHOULD increase the poll interval ... if the server does not
> respond within a reasonable time.
>  The ntp3 RFC1305 states.
> If valid data have been shifted into the filter register at least once
> during the prceding two poll intervals,... the valid data counter is
> incremented. .... Otherwise the valid data counter and poll interval are
> both decremented.
> which seems to indicate that if the server cannot be reached, the poll
> interval is decreased. 
> Is this a conflict or am I misreading the two standards?

You are misreading it. If there is no response you should ask less often 
since the chances are good that the next packet will also fail to get a 
response. You should never increase the frequency though there are 
clients that are known to do that.


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