ECN

Posted on January 20, 2007 by ward

Explicit Congestion Notification (ECN, RFC 3168) has been around for quite a while now, but there are still lots of devices and hosts out there that don’t support it properly. For instance, http://www.npr.org, and apparently all HP’s ILO and ILO2 baseboard management systems.

If you’re on a GNU/Linux system, just try it:

echo 0×1 > /proc/sys/net/ipv4/tcp_ecn

Now you can’t go to NPR’s website.

echo 0×0 > /proc/sys/net/ipv4/tcp_ecn

And now you can. If you compile your own kernels, you might have noticed that ECN is on by default these days. I can’t seem to find the configuration option to disable it anymore in the latest 2.6.20rc kernels, but the proc interface is still there.

I’ve left a message on NPR’s tech support page, let’s see if they fix this. As for HP’s ILO’s, maybe I can ask an acquaintance to forward this bug report to the right group/person…

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3 Responses to ECN

  1. ward says:
    January 23, 2007 at 1:58 am

    Turns out that NPR listens. I got a response to my query, which stated that they are aware of the problem and are working to resolve it.

    Yay NPR! Good work.

  3. ward says:
    February 22, 2007 at 8:46 pm

    Thanks Ben! Indeed, it works now. I really appreciate how NPR listens to its listeners :)

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