It is more complex than that. The general formula is the max-min fair-rate.

The formula Toke has provided works only if you have one single sparse flow s and all the others are bottlenecked at this link.

I.e. the experiment he has reported.

If you have N_s sparse flows and each consumers R_s,i and N_b bottlenecked flows the max-min fair-rate is

(R - sum_i R_s,i) / N_b

The simplest way to compute max-min fair-rates is using the water filling procedure (starting for low rate upwards) which

sets the threshold to determine if a given flow is in N_s or N_b.

BTW, this is well known literature. Search max-min rates calculations.

On Tue, Apr 17, 2018 at 2:22 PM, Toke Høiland-Jørgensen <toke@toke.dk> wrote:

Y via Cake <cake@lists.bufferbloat.net> writes:

> From: Y <intruder_tkyf@yahoo.fr>
> Subject: Re: [Cake] A few puzzling Cake results
> To: cake@lists.bufferbloat.net
> Date: Tue, 17 Apr 2018 21:05:12 +0900
>
> Hi.
>
> Any certain fomula of fq_codel flow number?

Well, given N active bulk flows with packet size L, and assuming the
quantum Q=L (which is the default for FQ-CoDel at full-size 1500-byte
packets), the maximum rate for a sparse flow, R_s, is bounded by

R_s < R / ((L/L_s)(N+1))

Where R is the link rate and L_s is the packet size of the sparse flow.
This assumes that the sparse flow has constant spacing between its
packets, which is often the case for a VoIP flow...

-Toke

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