[ntp:questions] Under which circumstances a reply comes 126 seconds later?

David L. Mills mills at udel.edu
Thu Mar 6 05:01:58 UTC 2008


How true. But, are you ready for this? The minimum average headway 
constraint, introduced to protect very busy servers, must be at least 16 
s by default, but allow for a temporaty 8-packet burst. So, if somebody 
configures a symmetric active association with iburst and autokey and 
minpoll 16 (!), the server will fight back and constrain the reply rate. 
I doubt anybody will ever attempt to climb that steep hill, but if so I 
would like to hear what they think about it. The issues are discussed on 
the rate management page in the current documentation.


Brian Utterback wrote:

> Danny Mayer wrote:
>> NTP never delays sending replies unless something is preventing it 
>> from running. I have never heard of a "limited" option in ntp.conf. 
>> What version of ntp are you running, on what platform, what does your 
>> ntp.conf look like and what else could be prempting ntp?
>> Danny
> Not strictly true. The response packet for a symmetric association can 
> come back an arbitrarily long time after the request was sent. The ntpd 
> program does not immediately respond to symmetric packets, instead 
> waiting until the peer polling interval expires.
> Brian Utterback

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