[Bloat] What is fairness, anyway? was: Re: finally... winning on wired!

Justin McCann jneilm at gmail.com
Sun Feb 5 12:53:55 EST 2012


On Sun, Feb 5, 2012 at 2:39 AM, Eric Dumazet <eric.dumazet at gmail.com> wrote:
> Le dimanche 05 février 2012 à 02:43 +0200, Jonathan Morton a écrit :
>> 2) Implement TCP *receive* window management.  This prevents the TCP
>> algorithm on the sending side from attempting to find the size of the
>> queues in the network.  Search the list archives for "Blackpool" to
>> see my take on this technique in the form of a kernel patch.  More
>> sophisticated algorithms are doubtless possible.
>>
> You can tweak max receiver window to be really small.
>...
> Basically you can delay some flows, so that TCP acks are also delayed.

I was thinking of suggesting this (delaying ACKs to avoid cwnd
increase), but doesn't that simply increase the RTT and/or RTT
variance, and basically do the same thing we're trying to avoid? I
suppose you could delay a bit, and then drop some earlier ACKs in case
the sender only increases cwnd per ACK (and not by the number of
segments the ACK covers), but that per-ACK behavior just seems like a
bug to me.

      Justin



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