[ntp:questions] Failure of NIST Time Servers

David L. Mills mills at udel.edu
Sat Jun 4 14:30:23 UTC 2011

Eugen ,

The remote NIST servers do not use the ACTS driver in the distribution. 
They use an algorithm called lockclock that functions as a modem device 
driver. I assume the unhealthy indication provided in the ACTS timecode 
is translated to the NTP LI indicator via the local clock driver, but 
Judah is using a relatively old and much modified version of the NTP 
reference implementation, so it is not clear how this is done.


Eugen COCA wrote:

>In my opinion, transmitting the time with an offset of about 680
>seconds with "... some of the systems transmitted the wrong time
>without this indication." (unhealthy indicator), is a bit
>unprofessional. Of course, it is the users' sole responsibility to
>configure his/her time servers in order to avoid these things.
>I'm thinking for you to post a messages stating that "such a behavior
>will never happen in the future as we discovered the bug and corrected
>On May 27, 11:16 pm, jlevine <jlev... at boulder.nist.gov> wrote:
>>The primary and backup ACTS servers that are used to synchronize the
>>Internet time servers to the atomic clock ensemble in Boulder failed
>>on Wednesday 24 May at about 1900 UTC (1300 MDT). The failure
>>11 of the 35 NIST Internet time servers, and the time transmitted by
>>the affected servers was wrong by up to 680 seconds. In most cases,
>>the incorrect time was accompanied by the unhealthy indicator, but
>>of the systems transmitted the wrong time without this indication. The
>>other 24 servers were not affected. In some cases, one of the physical
>>servers at a site was affected while the others were not, so that
>>repeated requests to the public site address resulted in time messages
>>that differed by up to 680 seconds.
>>The ACTS servers have been fully repaired as of 27 May, 1800 UTC (1200
>>and all of the servers should be resynchronized within a few hours.
>>may be a transient error of up to 10 milliseconds during this period.
>>I apologize for this failure, and I regret the problems and
>>that have resulted.
>>Judah Levine
>>jlev... at boulder.nist.gov
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