Re: [aqm] AQM schemes: Queue length vs. delay based

[Michael Welzl <[e-mail]>]

On 18. nov. 2013, at 13:44, Scheffenegger, Richard wrote:

> [chair hat off]
> 
> Hi Michael,
> 
>> 
>> ------------------------------------------
>>>>>>>>> RP:  Again, the tight delay control comes from narrow-band bang-bang control with hard drops. The scenarios >that throughputs are good are in higher congestion scenarios where there are enough packets showing up to fill the >pipe. That is not the effectiveness of AQM. Tail drop with shallow buffer will have high throughput in those cases >too. Try a scenario when link is congested and a burst comes, see how many packets of that burst can go through.
>> ------------------------------------------
>> 
>> Maybe we disagree about the goals... why would you want to allow a burst on an already congested link?
> 
> How do you define congested link?
> 
> You will want to be burst-tolerant on a link running at full capacity - but is such a link already congested?

I'd say no, this is just perfectly saturated. I was thinking of a link running at full capacity + a non-empty queue.

BTW, there was talk about how to define congestion and how to define congestion control at the AQM meeting, during Fred's presentation. If we need text for this, it's worth looking at the ICCRG archives, I remember a long and boring discussion about these definitions early in the life of ICCRG.


> In any case, defining a scenario that would lead to excessive buffering delay in the drop-tail case, and comparing this for various AQMs should be documented.

Sure

Cheers,
Michael