K-root Zone Propagation Delay
Between 07:30 UTC on July 16 2013 and 21:30 UTC on July 22, one server of the Amsterdam instance of K-root had disk drive problems, which prevented it from updating its copy of the root zone, and it got stuck on serial 2013071501. This may have caused some caches to receive stale responses to DNS queries, and may have caused some DNSSEC validation failures for some top-level domains.
This failure went unnoticed because we were in the middle of switching to a new monitoring system, and the check for fresh serial numbers was not carried over to the new monitoring system. We have corrected this now. We apologise for any inconvenience caused by this failure.