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Traffic shaping for 95th percentile

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Hello, all.  We are trying to figure out how to shape our colocated
traffic to conform to 95th percentile billing, i.e., where the top 5% of
traffic samples are discarded but the very next rate in the samples for
the month becomes the billable rate for the month.  So, if I have 100
samples, 5 of which are 45 Mbps and the rest under 1.5 Mbps, I am only
charged for a T1 but if I have 6 samples at 45 Mbps, I am charged for a
T3.

How can I shape my traffic to ensure I do not violate my guaranteed rate
(we'll use the above numbers for this email)?

I think this may be an interesting application for using a dilinear HFSC
curve for ul but that is only a best guess and presents some serious
issues.  Let's assume a five minute sampling interval so I can have up
to 36 hours in a month which are over my committed rate.

Let's say I set my ul to m1 45mbits d 20m m2 1.5mbits, I'd get a nice 20
minute burst for major downloads, backups, etc., but what if my queue
continually clears and backlogs? Theoretically, I could run at 45 mbits
for 20 minutes, have an instant of dead time where the queue clears, and
then start at 45mbits again crashing through my 95th percentile.
Conversely, if the queue never fully drains, I will have capped my queue
for the entire month when that was unnecessary. I'll also need to ensure
I use SFQ on the back end or I'll have massive buffer bloat when the
capacity changes suddenly.

I suppose I could try to get our monitoring system to monitor 95th
percentile and dynamically change ul as we get dangerously close but
that is going to be somewhat complicated and does not give a stand-alone
solution.

Is there a viable way to do this with traffic shaping alone or is the
only way by integrating it with a monitoring system? Thanks - John

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