Re: sysctl should disable ECN by default
On Sat, Sep 01, 2001 at 10:23:05PM +0200, Eduard Bloch wrote:
> #include <hallo.h>
Hi there.
My main point first, then assorted discussion about whether
ECN is enabled by default.
I think this should be a bug filed against
kernel-image-2.4.8, as it appears ECN was turned on
for official Debian kernels. I agree with you that ECN
is not yet appropriate for widely distributed kernels:
people should have to choose to make the statement that
bad firewalls that block ecn and bad for the internet.
Apparently Tomas Pospisek's patch in #110862 would do
what you suggest and print a message to the console saying
"Disabling TCP/IP Explicit Congestion Notification" which
seems fine.
It seems like y'all can manipulate the bug tracking
system to merge 110862 and the one you filed against
procps(?) with the wishlist item #98228 already in netbase.
My only desire is to make sure the user's configuration
is respected wherever possible.
Now for the sundries about ECN being enabled or disabled
by default:
> Why do many people think that it is OFF by default?
from the linux-2.4.9 top level directory:
"grep -r CONFIG_INET_ECN *"
shows the following:
arch/i386/defconfig:# CONFIG_INET_ECN is not set
from make config on a clean untar:
IP: TCP Explicit Congestion Notification support (CONFIG_INET_ECN) [N/y/?]
this is not universal, a few architectures' defconfig's
have ECN enabled. I don't know why this isn't uniform.
I apologize, however, it seems I was wrong about it being
experimental. It probably should have been, given that
it implements an Experimental RFC.
> The fact is, it is ON (see kernel docs) and it breaks with many sites.
which kernel docs are you looking at?
The Configure.help file (the only thing that matched
ECN in the Documentation subtree) includes:
TCP Explicit Congestion Notification support
CONFIG_INET_ECN
Explicit Congestion Notification (ECN) allows routers to notify
clients about network congestion, resulting in fewer dropped packets
and increased network performance. This option adds ECN support to the
Linux kernel, as well as a sysctl (/proc/sys/net/ipv4/tcp_ecn) which
allows ECN support to be disabled at runtime.
Note that, on the Internet, there are many broken firewalls which
refuse connections from ECN-enabled machines, and it may be a while
before these firewalls are fixed. Until then, to access a site behind
such a firewall (some of which are major sites, at the time of this
writing) you will have to disable this option, either by saying N now
or by using the sysctl.
If in doubt, say N.
> 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?
I have no wish to force ECN and a lack of connectivity
on anyone. The default should be off, but it should be
easy to turn it on.
-neil
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