[j-nsp] Tail drop on EX3400

[Philippe Girard]

Hi

Been going back and forth with JTAC on an output drop issue. I have two
ex3400-48t in a VC configuration and I got some ports reporting tail drop
from time to time, but lately one customer pulling max 80m on a 1000M
connection is generating some level of drops all day long. No complaints
yet but enough for monitoring to trigger.

The suggesting from TAC is to configure class-of-service shared-buffer
percent 100. I'm used to QFX5k switches allowing you to clearly see the
allocation and change it a bit, but this really isn't clear to me when I
run // show system buffers or show interfaces queue, etc.

I've been trying to ask, what's the default precentage allocation? Where
does the rest of the unclaimed percentage live while it's not explicitely
called for? Does calling out 100% take it away from ingress or some other
important queue? Is round robin possible by configuring class-of-service?
Would it avoid dedicating 100% of something to just one direction?

I've asked all of those questions but I can't seem to get a clear answer.

Thanks for your help.
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Philippe Girard