[Bloat] when does the CoDel part of fq_codel help in the real world?

[jf at jonathanfoulkes.com]

>>If I can restate that in a more concrete way: the queue may not drain at a smooth, constant rate.  There are several real-world link technologies which exhibit this behaviour - wifi and DOCSIS come to mind, not to mention 3G/4G with variable signal strength.

This!  

Also, bottlenecks can move, such as when a DSLAMs backhaul reaches saturation for minutes/hours in the evenings as everyone tries to stream, and end-point connections drop to less than 50% of the local sync-rate worth of effective capacity.
Therefore AQM settings about link capacity should be thought of as a Max not necessarily current link capacity.

BTW- Amazing discussion, loving it.

Jonathan Foulkes

-----Original Message-----
From: Bloat <bloat-bounces at lists.bufferbloat.net> On Behalf Of Jonathan Morton
Sent: Friday, November 30, 2018 6:05 AM
To: Luca Muscariello <luca.muscariello at gmail.com>
Cc: bloat <bloat at lists.bufferbloat.net>
Subject: Re: [Bloat] when does the CoDel part of fq_codel help in the real world?

> On 30 Nov, 2018, at 12:32 pm, Luca Muscariello <luca.muscariello at gmail.com> wrote:
> 
> Two last comments: one should always used fluid approximation with 
> care, because they are approximations, the real model is more complex. Nobody considers that the RTT varies during the connection lifetime and that ACK can be delayed.
> So CWD increases in a non simple way.

If I can restate that in a more concrete way: the queue may not drain at a smooth, constant rate.  There are several real-world link technologies which exhibit this behaviour - wifi and DOCSIS come to mind, not to mention 3G/4G with variable signal strength.

 - Jonathan Morton

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