[Cerowrt-devel] please kill the ECN thread from hell here and take it to aqm

Dave Taht dave.taht at gmail.com
Sun Mar 22 00:57:39 EDT 2015

On Fri, Mar 20, 2015 at 5:15 PM, Michael Welzl <michawe at ifi.uio.no> wrote:

> I think it's about time we finally turn it [ecn] on in the real world.

Please start with turning it on as fully as possible on *your* networks.

Advocacy with *actual experience* I approve of, otherwise it's just
religion and a rathole.

I only once been so tempted to shut a thread down on these email
lists. (the other time was a near-discussion of systemd)

This thread started off usefully discussing the docsis 3.1 deployment
and other deployment issues and if I could invoke godwins law on ecn,
I would. Hell, let me try that. Only a nazi would inflict such a
controversial technology on others without comprehensively trying it
themselves on all their own traffic. For years.

The ecn debate is a 21 year old bikeshed from hell.  There is no
comprehensive data from actual deployments.

Start with getting some from yours! And from whoever else you can
convince to try it, at scale, and not in manifestos that have so far
as I can tell, a multiplicity of false premises and wishful thinking,
not backed by any operational experience with the actual code

Go ahead, convince your org(s) to deploy it, get everyone using your
network to use it on every operating system available, have meet ups
for every new student entering your uni to turn it on, have a black
hat take the existing aqm algs apart, and then write a document
describing those experiences. *Then* write the rfc.

*I* deployed it. I gave my feedback already.

My conclusions 3 years back were:

1) ECN is safe to deploy given the bottleneck links had fq + aqm
w/ecn, and the links were high enough bandwidth to not slow other
traffic. But at lower rates, it clears congestion fastest, and uses
less memory, to drop packets.

2) It might be safe in limited well controlled environments (e.g. in
data center, and especially in long RTT environements in space or
satellites), but a wide range of testing on actual traffic mixes on
things like DCTCP - and what happens when things like DCTCP
accidentally escape the datacenter needs to also be carefully

3) It is not safe to deploy on the wild and wooly internet with any of
the pure aqm algorithms currently available.

I have seen no data to come close to challenging these conclusions,
nor tests, nor deployments, and until that happens...

...In addition to getting off the aqm mailing list, I am now sending
anything I get with the evil " ecn " in it directly to /dev/null  -
until prague or I get way better BP meds. I got way better things to

Dave Täht
Let's make wifi fast, less jittery and reliable again!


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