[ntp:questions] ntpdate function

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Thu Apr 11 19:51:14 UTC 2013


David Woolley wrote:> BlackList wrote:
>>  ICMP echo may have a lower priority than NTP;
>>
>
> ICMP echo is likely to be handled by the interrupt
>  service routine, with no process scheduling delays.

AFAIK, It depends on the device.

Some (many? most?) routers rate limit ICMPs through them
   (as low as 2 per sec per interface on some IOS flavors)

  ICMPs are also sometimes handled by routers via a lower
   priority process switch where if the router is very busy
   it could take awhile before the router gets around to
   handling the packet;  as compared to fast path switch
   {e.g. Cisco Express Forwarding / Multilayer Switching)
   for normal traffic.  IIRC, some WAPs do this too.


  As well as when the destination is the router itself,
   {which are sometimes used as NTP servers},
   on a very busy router it could be even longer before
   the router gets around to sending a ICMP reply (if ever).



If I guess correctly though, this would be the opposite of
 what the OP is seeing with whatever he is using.

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