occasional 1.5 second latency on a particular Sun Ray
From: CJT (abujlehc_at_prodigy.net)
Date: 03/29/04
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Date: Mon, 29 Mar 2004 03:57:38 GMT
I've got three Sun Rays scattered around my house, and am
quite happy with their performance, but I have noticed that
the one in one of my rooms experiences high latency at
random times.
It doesn't happen very often (on average about twice per
day) but the curious thing is that the latency reported
by utcapture is always nearly the same -- it's always in
the range 1502-1505 ms. Some days it doesn't happen at all,
and on other days it has happened as many as four times.
I don't think I've ever been sitting at the affected
device during an incident, so I don't know whether there's
anything perceptible when it happens.
The time of day when it happens seems to be random, and not
correlated with any cron activity or any other load on the
system or the individual Ray. And it only affects ONE of
the Rays, which are all on the same server and (dedicated)
subnet. I have confirmed that they are all running the same
firmware version (even though I don't know how they could
be otherwise, given the automatic firmware update of the Sun
Ray system).
When I swap the offending Ray with one of the others, the
problem stays in the room rather than following the Ray,
which suggests a cabling problem, but I've carefully checked
the punch-downs on the keystones and can't detect a problem,
and have tried switching drop cables. Plus, millions of
packets can be exchanged without any indication of a problem
between incidents (I often use them to play music, which
results in lots of packets being transferred).
Switching ports on my ethernet switch has no effect.
I've also considered the possibility that the surge protector
in that room may have been generating RF, and tried removing
it -- no change. I'm not aware of anything else along the cable
run that might be generating noise. In fact, for much of its
length, the implicated cable runs parallel to one to another
room which does not exhibit the problem. I do not know whether
the AC outlet in the affected room is on the same side of the
AC line as the others, but doubt that should make a difference
(has anybody ever seen a ground loop or ground imbalance affect
a Sun Ray?). One thing that suggests some sort of interference
is that the errors sometimes appear in burst pairs close
together in time (i.e. a high latency will be detected by
utcapture followed by another a few seconds later -- e.g. the
two most recent ones on my screen right now happened yesterday
at 9:42:29 and 9:42:44, both about 28 hours ago).
It's more an annoyance than anything, since I've never actually
seen that Ray malfunction as a result, but the consistency of
the length of the latency suggests to me that it's something
that could be solved if I could identify it precisely. It's
annoying enough I may just run another cable the next time the
attic is cool enough to spend some time up there, but I'd hate
to do that and still have the annoyance.
Does anybody have any suggestions?
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