[Iccrg] Re: [tcpm] ECN feedback discussion

[Steve Bauer]

> To have a better basis for such a decision, it could be useful to look at some data from the backbone, or from popular servers, on how many packets arrive with ECT0 or ECT1 set.

In our IMC 2011 paper,

Measuring the State of ECN Readiness in Servers, Clients, and Routers
http://rbeverly.net/research/papers/ecn-imc11.pdf

We reported that "Across all of our data sets, we see no instances of
ECN nonce support. Manual inspection of arriving packets with ECT1 set
reveals that these flows always set ECT1, even when ECN is not
negotiated by TCP."

So any packets with ECT1 set are evidence of something broken along the path.

Steven Bauer
MIT