On Sat, Aug 03, 2002 at 10:31:17PM +0200, Tony Earnshaw wrote:
> With the help of a Linux colleagure in Portugal, the fault was traced to
> ECN (Explicit Congestion Notification) being set to "on" in my kernel.
> ECN uses TCP flags originally assigned to TOS - it's a "new invention.
>
> '/bin/echo "0" > /proc/sys/net/ipv4/tcp_ecn' cured the Sun mail server
I don't remember whether I mentionned that since it's not much related to
exim, but yes, I traced the problem to TCP ECN right away, I know all about
it, don't worry.
That said, it's not a problem with linux or TCP ECN, it's a problem with SUN
using broken networking equipment. I have already Emailed them, and I think
they have ignored me (or they may just be slow).
Personally, I don't care, I refuse to cripple my systems because some people
don't care about RFCs (RFC 3168, on the standards track to be precise)
More details on how to fix the faulty networking equipment (cisco pix and
so forth) can be found here:
http://gtf.org/garzik/ecn/
> Sun's mail servers are (mostly, as far as i could find out?) Solaris 7&8
> machines, but some of the web servers were MS IIS machines, leading to
> the conclusion that routers between my ISP and them were also confused
> by ECN.
Not quite. Routers don't care about ECN. It was written to work over the
current infrastucture, like TCP sliding windows or timestamps.
There is just a few stupid outdated network devices (mostly firewalls) that
junk the packets.
> I don't think this can be an Exim problem, since for me it's now
There was a problem in exim's retry code with many MXes that got triggered
by 6 out of their 7 MXes not being ECN uncompliant
> way; Hotmail was another.
and they fixed it quickly after many complaints from users.
That was also a year ago IIRC.
People who are still broken today have much less of an excuse.
Marc
--
"A mouse is a device used to point at the xterm you want to type in" - A.S.R.
Microsoft is to operating systems & security ....
.... what McDonalds is to gourmet cooking
Home page: http://marc.merlins.org/ | Finger marc_f@??? for PGP key
