[Bloat] RED against bufferbloat

[Mikael Abrahamsson]

On Wed, 25 Feb 2015, Toke Høiland-Jørgensen wrote:

> While the academic side of me enjoys studying AQMs (and I'm still far 
> from anything resembling a thorough understanding of them), the 
> practical "I just want my network to work" side of me has become 
> increasingly convinced (in part by doing the experiments in the above 
> mentioned talk) that FQ is more important than AQM in many scenarios. As 
> such, I think that excluding FQ from the conversation is mostly of, 
> well, academic interest ;)

To me, FQ is important especially for lower speeds. This also maps well 
into the CPU based nature of FQ (that it's hard to do in "silicon").

We're not going to see FQ_CODEL on a 200 interface large router designed 
to push 100 gigabit/s of traffic, at least not in any interesting price 
point.

So one question that I would be interested in understanding is this 
scenario:

INTERNET----AR---CPE--HOST

Let's now say the AR has a stupid token bucket based policer (which 
doesn't queue, just drops packets) rate-limiting the traffic input/output 
towards the CPE to, let's say 120 megabit/s averaged with 1 second worth 
of burst bytes (because the ISP wants to make sure the customer can 
speed-test to 100 megabit/s of TCP throughput).

Can we do bidirectional traffic FQ_CODEL on the CPE to try to achieve 
basically zero loss in the AR policer for any normal kind of use scenario 
using TCP. I have not seen any simulations looking at this.

What about 12 megabit/s policer to a 10 megabit/s service? What about a 
12 megabit/s FIFO shaper (that would actually delay packets, but because 
it's FIFO we just rarely want to see buffering there).

Because my belief is that even though we might say we love FQ here, we're 
not going to see high speed FQ on higher end ISP aggregation routers. So 
if we want FQ, we're going to have to do it in the CPEs.

I am using terminology that is explained in this article:
http://www.cisco.com/c/en/us/support/docs/quality-of-service-qos/qos-policing/19645-policevsshape.html

-- 
Mikael Abrahamsson    email: swmike at swm.pp.se