Den Wednesday 11 March 2009 00.40.44 skrev Fons Adriaensen:
Hello all,
Today I had a strange problem when using the
WFS system here.
The 'master' PC sends a multicast message every
1024 samples (21.333 ms) to all 'render' PCs.
This has to arrive on time, and when it's late
the renderers will mute their output and report
the error in their status messages.
Today I used some ssh -X logins from my laptop
in the WFS room to the WFS master to run Ardour
and some other apps for a demo. All this worked
well all the time, as it has done before.
I left everything running when going for lunch
with our visitors, and when I returned restarted
Ardour to listen again. I got a lots 'of 'message
too late' errors from the rendering machines, and
interrupted sound. Strange enough this seemed to
be related to the _volume_ of the sounds...
In other words to Ardour's level meters.
Restarting Ardour in a new ssh login did not
help, but running it directly on the WFS master
solved the problem. So apparently the network
traffic required to update Ardour's meters was
causing the delays. And clearly the whole remote
X session was slower than normal. CPU loads
looked normal.
Now all this should be peanuts for a Gbit
network that has no other traffic at all,
and it worked perfectly before. I just never
left it running for such a long time.
Anyone an idea as to what is happening here,
and how it could be cured ?
I can't say that I can help you but 19 years as a network engineer can come in
handy.
The most obvious is that the network is overloaded in some way. Doesn't need
to be in terms of bandwidth. It can be things like spanning-tree going
heywire in switches. Redirects is another thing that comes to my mind. A
sophisticated (there are things like slow pings of IPv6 addresses that fills
up the table in a switch) DoS might also be the case.
If we assume it's the network that causes the problem you obviously have the
switches and the routers that can cause the problems not to say firewalls.
What network set up (equipment and such) do you have?
Is the network protected in some way?
Have you made some performance tests? iperf is handy.
TCP:
server:> iperf -s
client:> iperf -c server
UDP:
server:> iperf -su
client:> iperf -c server -u
/bengan