Re: [aqm] I-D Action: draft-ietf-aqm-ecn-benefits-04.txt

[Dave Taht <[e-mail]>]

for many positive bullet points in the present document I can think of
a negative counter-example in the real world that needs to be defeated
in detail. Just off the top of my head:

3.2 tinc, when carrying tos, encapsulates the ecn markings also and
does not apply them properly according to the various rfcs.
3.3 recently: one large providers equal cost multipath implementation
used the full 8 bit tos field as part of the tuple. This worked fine,
until CE started getting exerted by new aqms in the path, which led to
massive packet re-ordering. Fixing it required fixing a ton of pretty
modern vendor gear.
3.4: thus far, even with multiple queues, on the aqms I have, ECN
marked traffic causes extra loss and delay in non ecn marked traffic.
I agree that we should ecn mark sooner than drop, work is progressing.

I would like it if non-traditional (ab)uses of ecn were covered - 1)
attacks using ecn marked packets on dns servers, for example - and 2)
future protocols that could use it (say, Quic).
3) as an example of something I've been fiddling with for a long time,
coupling a routing protocol's metrics to something other than packet
loss, and getting better "signal strength" by using ecn marked packets
for more reliable communications under congestion.

the draft touches upon voip uses (where I kind of think ecn is not the
best idea), but does not touch upon videoconferencing well, where I
think ecn protection of iframes would be a very good idea. So the
guidance in sec 2.4 is a bit vague.

aggregating transports with retries (e.g. wifi) could use ecn
basically "for free" when experiencing trouble at the lowest layers of
the stack.

I know I have a tendency to accumulate the negatives (I do LIKE ecn),
but would certainly like to have a fora, or a living document or wiki
for potential sysadmins, vendors, and deployers to have a clear grip
on what can go wrong when attempting to roll out ecn stuff.

So I am mostly in favor of this document getting published, so long as
someone steps up to also be an "ecn news central", chock full of user
generated content on the pitfalls, tips, and tricks - and benefits! -,
to guiding ecn deployment further along.

ecn is inevitable. finally.