[Babel-users] [PATCH 2/3] Add ECN support to babel messages

[Dave Taht]

On Wed, Sep 26, 2018 at 3:36 PM Juliusz Chroboczek <jch at irif.fr> wrote:
>
> > -    const int ds = 0xc0;        /* CS6 - Network Control */
> > +    const int ds = 0xc2;        /* CS6 - Network Control + ECN */
>
> Nope.  If we start lying about ECN, people will start disabling ECN in
> routers, which would not be a good thing.

I appreciate the moral stance, and to a huge extent I share it (
https://www.bufferbloat.net/projects/ecn-sane/wiki/dtaht_ecn_editorial/
)

On the other hand the characteristics of ECN'd babel traffic (single
low volume flows) interact with fq_codel
well, only imparting delay on overload to those flows and affecting
other traffic minimally. It makes l3 based routing info behave more
like a control plane, and more similarly to 802.11s which does stuff
at the management frame layer underneath layer 2 with no congestion
control applied at all.

I had at one point a patch that attempted to do more of the right
thing ( increasing the metric as per loss but not ever going infinite
) but it was invasive. At some point in the coming year or two maybe
we'll be able to sit down and do more science on the ecn front but
it's quite a long list (
https://www.bufferbloat.net/projects/ecn-sane/wiki/  ) with the usual
lack of bodies and funding.

In the interim, I'd welcome more data from more deployments. Including mine.



I

-- 

Dave Täht
CEO, TekLibre, LLC
http://www.teklibre.com
Tel: 1-669-226-2619