[altq 66] Re: bandwidth oscillation

[Kenjiro Cho <kjc@csl.sony.co.jp>]

Geoffrey CRISTALLO said:
>> The bandwith is equally divided among these 4 flows (they all receive a
>> little bit more than 20 % and the bandwidth for each flow is stable)

>> But if I add a fifth flow (from S to R), the bandwidth of the individual
>> flows start to oscillate. Although the total bandwith remains smooth.  

>> I've tried several combinations of source-destination pair, but the
>> oscillations always appear when I add the fifth flow.

>> I was wondering if these oscillations were typical TCP behaviour. Can
>> somebody justify them ?

I suspect that the oscillations are caused by process scheduling at
the receiver.
Up to 4 flows, the receiver app is able to call read() before the next 
packet arrives, and thus, the app processes one packet at one time.
Once the app is getting behind, it has to handle multiple packets at
one time.  This, in turn, interferes with other apps.

-Kenjiro