[Bloat] AQM & Net Neutrality

Holland, Jake jholland at akamai.com
Thu Jun 3 05:23:15 EDT 2021

Hi Stuart,

On 05-24, 12:18 PM, "Stuart Cheshire via Bloat" <bloat at lists.bufferbloat.net> wrote:
> Delay reduction is not an either/or choice. In order for some traffic to benefit other traffic doesn’t have to suffer. It’s not a zero-sum game. Eliminating standing queues in network buffers benefits all traffic. This can be hard to communicate because it seems counter to human intuition. It sounds too good to be true. In normal human life this is uncommon. When first class passengers board the plane first, all economy passengers wait a little bit longer as a result. Computer network queueing doesn’t operate like that, which makes it hard to explain by analogy to everyday experiences that most people understand.

This is a great point and maybe worth expanding on.  It made me
think of a few such analogies in the real world that maybe could be
easier for people to intuitively grasp.

For example, there's some good videos on traffic handling like this
one that can show the difference between 2 intersecting 4-lane roads
with an intersection having a traffic flow of 191 (at the start), vs.
2 intersecting 4-lane roads with a stack interchange doing an almost
6x better 1099 (at the 6-minute mark):

I feel like if you told people that's kinda like the difference
between using a router with and without AQM, they'd have a useful
model that would make some sense to them, even though the dynamics
aren't quite the same.  The point is that by setting up a nicely
optimized infrastructure, it prevents people from getting in each
others' way and makes it better and faster for everyone.

But I don't think that's the only example, there's other real-world
scenarios people can maybe follow, like comparing the Steffan airplane
boarding method to back-to-front.  There's some short and sweet videos
that can make the point, perhaps in a way that non-experts can more or
less follow and see how it helps:
(Even when there's a first class section with special treatment, this
could still help in coach, if only there were enough luggage space...)

Likewise with some other IRL queue-tuning strategies like how to
set up checkout lines at stores, there's some videos that do a good
job explaining why it helps and how it works (though IIRC this trades
off maximum delay vs. average delay, so it's not quite the same
"everybody just purely wins" point):

But maybe some of these are too far away from networking, I dunno.
So another also-ran on "accessible explanation" is this adorable video
from RIPE in 2016, which is nice because it's actually talking about
the right thing.  It says the same thing about helping everyone, but
only quickly and in-passing.  I feel like something along these lines
that harps on the "helps everyone" point a bit more might be the right
kind of thing:

Anyway, it's an excellent point that this non-zero-sum aspect might be
a barrier to understanding, and I bet it's worthwhile to try to get
the "everybody benefits from a good AQM" point across more explicitly
and more often, especially if people are mistaking this for priority/
net neutrality issue.

And just a quick side note:

> This is why I’ve been advocating for making low delay available for *any* traffic that chooses to opt-in to this smarter queue management, not selectively for just some privileged traffic. 

AQM at a network bottleneck is not an opt-in thing, it just applies
to all the traffic passing through.  (ECN helps a little at the app
layer from loss avoidance, but usually not as much as the lower queue
target by far.)

Best regards,

More information about the Bloat mailing list