Subject: [tcpm] ECN re-survey

From: "Scheffenegger, Richard" <[email-masked]>
Date: Mon, 10 Mar 2014 10:19:56 +0000

Hi,

anyone interested in re-visiting and evaluating the data collection about ECN prevalence and support? [1]

My first go indicates, that today the server-side support of ECN is up from ~30% (Aug 2012) to 40% (Mar 2014) - the top 20k alexa sites sampled so far.

But the more interesting aspect, which wasn't mentioned in [1] is that in particular the larger sites apparently are more likely to have broken web-front end load balancing servers / proxys / gateways...

The observed behavior matches what RFC3168 describes as broken TCP stacks, simply reflecting all unknown TCP options (which is why ECN TCP negotiation is <SYN,ECE,CWR> / <SYN,ACK,ECE>).

My initial thought is that some large vendor of such load balancers - affordable only by large scale sites, most notably one former behemoth which is currently struggling a bit - has a flawed TCP implementation. Perhaps someone wants to help me identify the vendor, to get that invalid TCP behavior rectified?

The farther down in the alexa list the sampling (thus, ever more smaller sites, with less traffic), the higher the prevalence of proper ECN support, and also fewer and fewer broken TCP stacks are observed...

(For now, I'm only samping TCP ECN on port 80, with the primary motivation in AccECN actually).

[1] http://www.ikr.uni-stuttgart.de/Content/Publications/Archive/Kue_PAM13_40160.pdf

Richard Scheffenegger

NetApp
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