[Pool] [ntp:questions] 4000 packets a second?
David L. Mills
mills at udel.edu
Wed Sep 1 03:43:56 UTC 2010
The code I wrote in ntp_monitor.c has apparently been rewritten. The MRU
resolution is in seconds. The original interpretation of minimum was
that any headway less than this would be dropped. Setting that to zero
would mean nothing would be dropped. Apparently, the current code is
contrary to the original intent and documentation.
I didn't check to see if the probabilistic choice to preempt old entries
if the list is full remains. My earlier experience is that this is
important for the busiest servers.
Dave Hart wrote:
>On Wed, Sep 1, 2010 at 00:42 UTC, David L. Mills <mills at udel.edu> wrote:
>>Did you intend the discard minimum 0? That effectively disables the rate
>>control defense mechanism. you should leave it out.
>That has not been my experience on the pool server I'm involved with:
>hart at pool1> fgrep discard /etc/ntp.conf
># discard minimum 0 (power of 2 like poll interval) is needed
>discard minimum 0 average 3
>hart at psp-fb1> ntpq -c sysstats
>sysstats reset: 1059862
>packets received: 263004216
>current version: 144454930
>older version: 99867648
>bad length or format: 18635251
>authentication failed: 316799
>rate limited: 56970859
>KoD responses: 1405175
>processed for time: 76220
>hart at pool1> ntpdc -c sysstats
>time since restart: 1059868
>time since reset: 1059868
>packets received: 263005578
>packets processed: 76220
>current version: 144455895
>previous version: 99867947
>access denied: 14857
>bad length or format: 18635348
>bad authentication: 316800
>rate exceeded: 56971000
>hart at pool1>
>A bit over 20% of incoming traffic has exceeded rate limits with
>"discard minimum 0" used (1s minimum).
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