[ntp:questions] any reason why NTP client would receive -10sec diff?

Blair Smith b.smith at irl.cri.nz
Mon Nov 10 02:43:03 UTC 2008

Hi all,
I'm a newbie timekeeper and I tried searching the lists and ntp docs for an answer to this problem but haven't found a clue so far.

This morning a client phoned me telling me that their server was being told it's clock was in advance of our ntp time by +10sec or else was being asked to step it's time backwards 10sec (i'm not exactly sure what the manifestation of the problem was because I was only given a rough verbal description of the trouble).  In any case this is unheard of in my limited time as an NTP admin!!  Naturally their ntpd wasn't going to accept a jump by -10sec, so subsequently their server started polled our tier-one server every second for a while before giving up, after which their time had drifted out of sync by about a minute.  They run a Windows network and it was critical that their time was in good sync (I cannot divulge the client for confidentiality reasons, but believe me it is a critical problem).  They've started using another tier two server and apparently have had no further problems so far.  I can't see any obvious problems with our servers, but maybe I'm missing something?  Their software using NTP was something called "Netware", which I'm not familiar with, so I was unable to help them.  One potential cause of problems at our end was a lightening strike at our facility on Friday 7th Nov, which affected other systems in the same building but not, as far as I know, the clocks or NTP servers.  The client started reporting this problem on that Friday evening, but that could be just a coincidence.

So my question is why might this client problem occur?  Any suggestions would be appreciated.  I'm a bit in the dark because they won't give me access to their system logs and they are instead suggesting there is a problem with our servers.

- Blair Smith

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