[tcpm] [Iccrg] Re: ECN feedback discussion

[Mikael Abrahamsson]

On Fri, 9 Nov 2012, Emmanuel Lochin wrote:

> Ok, ECN might be not used inside the whole network but who cares? All
> my core devices are ECN compliant so why not using inside my own
> network?

What core devices are that? When I last looked at platforms such as Cisco 
CRS-1 / ASR9k, Juniper MX/P-series, Huawei 5000, none of them supported 
ECN. This was a few years ago, so I'd be happy to be enlightened about 
progress! The only platform I have encountered so far that does ECN are 
Cisco processor based platforms such as the 7200.

> We know, following "The power of explicit congestion notification", A.
> Kuzmanovic, Sigcomm05, that even a partial deployment of ECN brings
> out benefit for the end-user. My GNU/Linux stack does not react to
> ECN? Not a problem ... my access network does.

What devices are those?

> On my side, I use specific mechanisms conjointly with ECN inherited
> from the QoS epoch. For instance, I can shape ECN feedbacks to slow
> down connexions or to give a delay penalty to a specific flow.
> Basically I use ECN like an "alert".

But how many flows do you have that are ECN enabled? What host systems 
uses ECN by default?

I have this on my linux boxes:

$ grep -i ecn /etc/sysctl.conf
net.ipv4.tcp_ecn = 1
net.ipv6.tcp_ecn = 1

(I believe the ipv6 line is redundant, just put it in there to be future 
proof). I do not believe this is the standard setting? Please correct me 
if I'm wrong.

-- 
Mikael Abrahamsson    email: swmike at swm.pp.se