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Re: sysctl should disable ECN by default

Zitiere Eduard Bloch <edi@gmx.de>:

> Neil Spring wrote on Sat Sep 01, 2001 um 12:34:40PM:
> > being turned off behind my back.  ECN doesn't need any
> > more inertia slowing its deployment.  It's already an 
> > experimental, off by default, addition to the kernel.
> Why do many people think that it is OFF by default?
> The fact is, it is ON (see kernel docs) and it breaks with many sites.
> We could live long without this experimental feature, so why _force_
> the users to use the feature now and make a stable distribution with
> limited networking ability?

Incidentaly I'd today filled a *critical* bugreport against
kernel-image-2.4.8 just because of that.

It's not only *sites* that do not work with ECN. It's also *routers*. That
means if you have *one* router between you and your destination, that does not
support ECN, then you'll get *very* strange behaveour like hanging TCP
connections that somehow get halfway through but do hang never the less while
ping works. Please check my bugreport #110862. And amongst the broken equipment
are f.ex. (older?) Zyxel ISDN routers which are *very* popular.

The first *experimental* rfc for ECN dates from 1999. That's not like ages.
There's a lot of equipment online from that time.

If it'd be trivial to find out what's going on, like the kernel log saying:
"attention someone on your route doesn't understand ECN" then that wouldn't
be a problem. But the fact is that there's *nothing* that would tell you
what's wrong. The packages do not arive, that's all. Mind I couldn't even
find a mention of ECN in the kernel docu.

So you're in front of a network, where the windozes work, the SuSE on your left
side works, you can see your lan, you can telnet the router but this *one*
Debian box is not able to get out of the lan.

I've sent a patch to netbase to have an option disable_tcp_ecn that's set by
default (==disable!).

If someone wants ECN he *has* to understand what he's doing, because he'll
potentially break his system. ECN has to be *off* by default!

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