[Ecn-sane] [Bloat] abc congestion control on time varying wireless links

[Jonathan Morton]

> On 11 Dec, 2019, at 9:54 pm, Dave Taht <dave.taht at gmail.com> wrote:
> 
> The DC folk want a multibit more immediate signal, for which L4S is
> kind of targetted, (and SCE also
> applies). I haven't seen any data on how well dctcp or SCE -style can
> work on wildly RTT varying links as yet, although it's been pitched at
> the LTE direction, not at wifi.

It turns out that a Codel marking strategy for SCE, with modified parameters of course, works well for tolerating bursty and aggregating links.  The RED-ramp and step-function strategies do not - and they're equally bad if the same test scenario is applied to DCTCP or TCP Prague.

The difference is not small; switching from RED to Codel improves goodput from 1/8th to 80% of nominal link capacity, when a rough model of wifi characteristics is inserted into our usual Internet-path scenario.

We're currently exploring how best to set the extra set of Codel parameters involved.

 - Jonathan Morton