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

[Jonathan Morton <[e-mail]>]

> On 18 May, 2015, at 18:27, Simon Barber <[e-mail]> wrote:
> 
> Apparently a significant chunk of bittorrent traffic and Windows updates use these techniques to deprioritise their traffic. Widespread adoption of AQM will remove their ability to avoid impacting the network at peak times. Use of DSCP could be one way to mitigate this problem with AQM, and this merits further study.

I’m working on a comprehensive algorithm (including AQM, FQ and Diffserv support and a shaper in one neat package) which does address this problem, or at least provides a platform for doing so.  Some information here:

	http://www.bufferbloat.net/projects/codel/wiki/Cake

This is working code, albeit still under development.  I’m actively dogfooding it, and I’m not the only one doing so.

The Diffserv layer provides a four-class system by default, corresponding in principle with the 802.1p classes - background, best-effort, video and voice.  It does not inherit the naive mapping from DSCPs to those classes, though - only CS1 (001000) is mapped to the background class.

An important part of the Diffserv support in Cake is that the enhanced priority given to the video and voice classes applies only up to given shares of the overall bandwidth.  If traffic in those classes exceeds that allocated share, deprioritisation occurs.  This ensures that improperly marked traffic cannot starve the link, and attempts to incentivise correct marking.

 - Jonathan Morton