NTP timewarp


Mills@UDEL.EDU
Sat, 19 Mar 88 16:56:13 EST


Folks,

At the moment both the ISI and NCAR radio clocks have failed, while the UDel
radio clock is down for repair. This leaves only the UMd and Ford radio
clocks online. Unfortunately, sometime since Friday evening the NTP primary
time-server network, which usually thrives when one or more radio clocks
fail, went nuts and may have delivered bogus time. I believe I have found
and fixed the bug, which turned out to be subtle indeed and bit only in
an interesting and unusual scenario involving broken spanning trees. As
of now (Saturday afternoon) all primary servers ISI, NCAR, UDel, UMd, Ford
and DECWRL have been fixed. Note that all except UMd and Ford are running
at stratum two, since they have automatically resynchronized to the remaining
radio clocks. Secondary servers at Linkabit and Rice, now operating at their
usual stratum two, have also been fixed.

There is at least one Unix site that crashed due the broken time. Since the
bug was due to my own error and not due to the protocol design or Mike Petry's
NTP daemon, I do apologize for any inconvenience. When a new NTP daemon
conforming to the latest protocol revision becomes available, even this latest
bug will not cause timewarps, should something like it ever happen again.

Dave



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