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[altq 44] Re: RED parameters
CCed to the altq mailing-list.
>> I saw the difference in RED paper and FREEBSD code for
>> dropping probability calculation. Can you please explain it ?
>> RED paper says
>> Pa = Pb/ (1 - count*Pb)
>> Pb = MAXp (avg - MINth)/(MAXth - MINth)
>> BSD code does this
>> for denominator
>> d = (2* (TH_MAX - TH_MIN) / MAXp)
>> so why we are having this extra 2 ?
This corresponds to the "wait" parameter set to "true" in the ns
simulator. In this mode, the drop probability starts from Pb/2
(instead of Pb) and provides larger spacing between drops.
The similar effect can be obtained by decreasing MAXp to MAXp/2.
>> Pa = Pb/ (2 - count*Pb)
>> Is it that we have arrived at this equation after simulations ?
I believe so. At least, it is the current default in ns.
>> also inverse of maximum prob. is set at 10. is it arrived at
>> to use Sally's recommended values (1/ 30) ?
The current default in ns is MAXp = 0.1.
As I recall, Sally said that it works better with short lived flows.
These parameters are briefly described in
"Ns Simulator Tests for Random Early Detection (RED) Queue Management"
>> One thing more, RED i understand is also implmented on
>> RTOS. Do we have any performance figures for that? Even if you give
>> pointers it is sufficient.
RTOS == Real Time Operating Systems?
The performance should not be different from a FreeBSD box.
>> Thanks in advance.