Re: [tcpm] Fwd: Probing the viability of TCP extensions

Adam Langley <> Wed, 23 June 2010 01:11 UTC

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From: Adam Langley <>
To: "Scheffenegger, Richard" <>
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Cc: Multipath TCP Mailing List <>,, Hannes Tschofenig <>
Subject: Re: [tcpm] Fwd: Probing the viability of TCP extensions
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On Tue, Jun 22, 2010 at 7:13 PM, Scheffenegger, Richard <> wrote:
> Adam is a member of the TCPM list :)

Er, yea, hi :)

> I am curious, out of the 1,07% of Hosts where ECN negotiation was
> successful, is there any indication that internet routers are actually
> making use of the ECT / CE codepoints in the IP header?

I didn't look for it. The prober didn't progress beyond the initial
TCP handshake.

> Also, your research was done in 2008 - Microsoft has introduced ECN
> support with Windows Vista / 7, is there any indication of rising levels
> of public ECN support, or still a falling trend?
> I'm asking as there seems to be renewed interest in having
> ECN-singalling in private networks again...

I haven't retried the experiment since the initial investigation.
However, there wasn't anything special about it: I did it from a
standard hosting company VPS machine (after clearing it with them
first). The only sensitive bit was the list of hostname from the
Google index. You could just download the .com zone and achieve much
the same effect I'm sure.


Adam Langley