[Bloat] Bufferbloat in high resolution + non-stationarity

[Mikael Abrahamsson]

On Thu, 30 Nov 2017, Jonathan Morton wrote:

> I submit that to provide *deployable* QoS schemes, you must either solve 
> the classification problem elegantly (which is a Hard Problem), or else 
> show that your scheme works adequately in the absence of classification. 
> I'm taking the latter approach with Cake, even though it *also* supports 
> Diffserv awareness to enhance its performance where classification is 
> straightforward.

In IETF INT-AREA, there is now discussion about allocating a new diffserv 
codepoint for "less-than-best-effort" traffic. I have been advocate for 
this for quite a while, and I actually believe that this is incrementally 
deployable and has a chance to actually get ISP buy-in.

The idea is to use TOS 0, but use the last 3 diffserv bits to indicate 
that this is less-than-BE. Non-implementing networks will treat this as 
BE, implementing networks can use some kind of DRR scheme to give this 
traffic less bandwidth in case of congestion, or just drop it earlier when 
there is queue buildup.

I think this is the only chance we have to get internet-wide coordination 
for a diffserv codepoint that people will do anything with, and the 
recommendation should be to only act on this at the customer access line 
(the one connecting the ISP to the residential gateway) or perhaps within 
the customer network. The hope is that ISPs will not mangle/bleach this 
codepoint, because it actually indicates traffic should get lower 
priority, not higher.

I am in complete agreement with you that any scheme that relies on 
Internet-wide QoS scheme based on diffserv/TOS is a no-go. No ISP will 
listen to this and act on it, as it's a DoS vector.

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