[Bloat] ECN blocking router found

[Brian Clapper]

On 04/14/2011 12:44 AM, Dave Taht wrote:
> In my travels this month I have been testing ECN enablement at homes and
> hotels everywhere I go.
>
> Until today, I was able to have the following settings for ECN on my laptop
> everywhere I've been.
>
> net.ipv4.tcp_ecn=1
> #net.ipv6.tcp_ecn=0
> net.ipv4.tcp_sack=1
> net.ipv4.tcp_dsack=1
>
> However, I got to visit Brian Clapper [1] (friend/co-author of gnugol)
> tonight, and discovered that his fairly recently purchased router, a:
>
> Etherfast Cable/DSL router Model BEFSR41
> Firmware version 2.0.0.4

NOTE: Per the support web site for this device, firmware revision 2.00.4 is 
the latest.

> flat out refused to pass ECN enabled connection attempts (returning an ICMP
> unreachable message)
>
> He'd not noticed the problem because ubuntu 10.4 (at least, he also runs bsd)
> has tcp_ecn=2, which so far as I know "tries" a ECN enabled connect then falls
> back to not using it.
>
> I'm bummed that such a recent router doesn't pass ECN, and will look into the
> problem further in the morning.
>
> So I think we must use tcp_ecn = 1 to TEST to make sure ECN is being passed,
> and tcp_ecn=2 as the default recommendation.
>
> Perhaps we can synthesize TCP streams to more directly test ECN capability in
> the future somehow as part of our testing tools. Are there any tools that
> synthesize TCP/ip we could use as a starting point?
>
> [1] http://brizzled.clapper.org/
>


-- 
Brian Clapper, bmc at ardentex.com
President & Principal Consultant: ArdenTex, Inc.
610.247.4395 (phone)
484.932.1270 (fax)
www.ardentex.com