[Iccrg] congestion control and visability to the user

[Mikael Abrahamsson]

On Mon, 29 Mar 2010, Damon Wischik wrote:

> Mikael Abrahamsson wrote:
>> The core router world is more and more going to smaller buffers (< 50ms, 
>> often much lower than that) which makes WRED/ECN less and less usable.
>
> Could you explain this? I thought that ECN was more and more useful, the 
> smaller the buffer. The idea is to run a virtual queue, with capacity e.g. 
> 90% of the link speed, and to mark packets when the virtual queue builds up. 
> This way, the link should be able to maintain a stable utilization of about 
> 90%, and the flows should never see packet drops.

So basically a 90% link speed policer would set ECN on any packets that 
exceed 90% of link speed? Yes, that would work even on cheap L3 equiment 
if they were capable of that action in their policer implementation.

Still haven't seen any implementations doing this, but it makes sense. 
This has nothing to do with buffering though, this can be done on a device 
regardless of size of buffers.

Otoh it would involve actually dropping non-ECN packets at 90% of 
link speed to be effective, right?

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