> NTP never sets the clock backwards (see 2, above).
*BZZT* WRONG!
Xntpd, version 3 (I think 3.92 or 3.93, but don't quote me), would OFTEN
set the clock backwards.
More to the point, if the offset is small, the time deamon adjusts the
drift rate. If the offset is large, it takes a lump jump.
If you are on a phone line connection, and you are downloading files
when it decides to check the time, it will get it wrong. 5 wrong polls,
and it will synch to the wrong time, and do a jump step. That can be as
quick as 5.5 minutes (download one browser update, one game demo, etc.)
I solved this for my system by drastically dropping the synch threshold
from "1" to ".005" (if my memory is correct) -- this prevented synchs
unless the daemon was certain that things were correct.
However, I have seen 600,000 ms jumps in the clock (that's 6/10th of a
second!). These happen more often in times of war (more precisly, about
a 2 week period before war activities start, or after they stop. Someone
told me that the GPS satellites can be moved to provide more accurate
tracking in an area, and they are the source of network time nowadays.)
Jumps of 100,000 are common (more than once per month, about every two
weeks if I remember correctly, even on a DSL line connection). And they
go backwards as often as forwards.
