[Bloat] About LEDBAT, µTP and BitTorrent

[Luca Dionisi]

On Fri, Feb 4, 2011 at 11:18 AM, Luca Dionisi <luca.dionisi at gmail.com> wrote:
> On Fri, Feb 4, 2011 at 11:04 AM, Juliusz Chroboczek <jch at pps.jussieu.fr> wrote:
>>> I think that the 2 things have to be carried on independently,
>>
>> Yes.
>>
>>> The problem is that one cannot make sure that end users will act
>>> fairly, by adjusting their sending rate.  The only way to do this is
>>> dropping packets, so that they are obliged to send again.
>>
>> Well, the issues of increased delay and greedy, unresponsive flows are,
>> to a certain extent, distinct.  One can image AQMs that are only
>> concerned with penalising unresponsive flows but don't do anything to
>> reduce buffer size when all flows are well-behaved.  Conversely, one can
>> imagine solving the buffer bloat problem on the assumption that all
>> flows are TCP-friendly.
>
> I don't get it. Why do we need to make such an assumption?
> If the routers keep a low buffer size (better if dynamically, if I am
> correct) and much better if they *also* implement a AQM which
> rate-limit the unresponsive flows, then we will have almost solved the
> problem and *also* actually discouraged unfair behavior from clients.
>

Ah, I got. You say that if routers penalize unresponsive flows than we
discourage unfair behavior.
Ok.
But then, since we must enable routers to use AQM, why not also make
them reduce their buffer size.
Anyway, the end-to-end solution alone is not sufficient.