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

[David Schinazi]

Hi Dave,

If I'm understanding you correctly, you want Babel to say it's an
ECN-capable transport to have it land in a shorter fq_codel queue.
I'm not familiar with what configuration knobs fq_codel offers, but
couldn't you instead configure fq_codel to filter based on DiffServ
when deciding which queue a packet goes in? Barring that you
could also imagine filtering on the UDP port number, but that
sounds even less likely to be supported.

I think I agree with Juliusz here, I'd prefer Babel stay truthful and
instead change how fq_codel reacts to it.

David


> On Sep 27, 2018, at 09:30, Dave Taht <dave.taht at gmail.com> wrote:
> 
> 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
> 
> _______________________________________________
> Babel-users mailing list
> Babel-users at alioth-lists.debian.net
> https://alioth-lists.debian.net/cgi-bin/mailman/listinfo/babel-users