[e2e] Linux, firewalls and ECN deployment

[Michael Welzl]

Hi all,

Here's something that I've been wondering about for quite
a while ... this may actually not be the perfect forum, but
I've not been involved in any Linux mailing lists yet and don't
know what they're like (I'm afraid of all the traffic I'll get
by subscribing  :)   ) ... and, as end2end-_INTEREST_, it should
at least be of interest    :)

So here it goes:

When I recompile my (most recent) Linux kernel, there's ECN
support somewhere under "advanced networking". By default,
it is disabled, and there is a recommendation to disable it
because some misconfigured firewalls will disable access if
you turn it on.

Now, my questions are:

1. is this still true? are there any measurements that show this?

2. WHY doesn't my Linux kernel try without ECN after a while
if I enable it? This way, it would be incrementally deployable ...
users would have an incentive to turn it on, or it could even
be turned on by default, which would lead to an incentive to
correct these firewall bugs ...

I just don't understand this.

Cheers,
Michael