[plug] Explicit Congestion Notification

[Anthony Jones]

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Everyone,

I don't know whether anyone has mentioned this or whether anyone else has had 
the same problem as me, but I have had trouble accessing some sites such as 
www.pbs.org.  I had previously never had any trouble accessing this site.  I 
only got my modem going once I got to Australia.  And until now have had 
trouble accessing this site (and others).

I thought I was going crazy or that my ISP was doing something wrong - I even 
tried using their caching proxy server but this did not seem to help.  I did 
find out that their proxy server had five IP addresses, only two of which 
worked - they have since improved it and they have three IP addresses, still 
only two of which work.  This means you get a two out of three chance of 
getting a caching proxy.

Through the caching proxy I had occasional success - I could read 
www.pbs.org/cringely but I suspect only when someone else on my ISP had 
brought it into the cache for me.

I found out (by asking the right people) that the problem is caused by ECN.  
On Debian Woody it is turned on by default and the firewall at www.pbs.org 
spits the dummy when it gets a packet with ECN enabled.  Clearly they and the 
other 10% of sites that I've looked at on the Internet need to upgrade their 
firewalls.  For now, I have to do this:

echo "0" > /proc/sys/net/ipv4/tcp_ecn

Has anyone else been suffering from this problem?  I guess you guys have 
already seen this problem and solved it many times before.

TTFN

Anthony Jones 
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