[plug] Explicit Congestion Notification

[Arkem]

On Thu, 29 Nov 2001 10:39, Anthony Jones wrote:
> 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.
>

ECN only causes problems when your packets are routed through routers 
that don't support it, slowly more routers are having this fixed and 
eventually it will work well. At the moment the best option is to 
turn it off by echoing "0" to the /proc/sys/net/ipv4/tcp_en the only 
other solution is to compile a kernel without ECN support which does 
practically the same thing (in a round about manner). To make it so 
that this command is run on boot you can create a script in 
/etc/rc2.d/ called S50whateverhere with the command in it which will 
be run every time you reach run level 2 (multi-user mode?) which is 
every time your computer is booted normally. The more accepted debian 
way of accomplishing this is to place the script in /etc/init.d/ and 
link it to /etc/rc2.d/S#name where # = a number between 0 and 99 (I 
think this indicates priority and load order) and name is whatever 
you want it to be called.

Anyway enough rambling, the idea is that ECN causes problems because 
of bad router software out on the net. Hopefully there will be a time 
when all routers support this but in the mean time its best to either 
turn it off or compile a kernel without it in.

Regards.
Paul