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...

For 10-Mbit/s link rate and 32 bulk flows with 1500-byte packets this formula gives roughly 25 pps (packets per second) as maximum for a sparse flow. A VoIP flow is typically 50 pps (20 ms voice payload).

Does this mean that cake sets the quantum to less than 750 bytes for a 10-Mbit/s link?

Do you see any benefit with cake diffserv if you increase the number of flows?

Does the adjusted quantum also explain the "*way* higher" TCP RTT for cake? How?

/Jonas