Re: [Bloat] sigcomm wifi

[Michael Welzl <michawe@ifi.uio.no>]

On 24. aug. 2014, at 07:14, David Lang wrote:

> On Sat, 23 Aug 2014, Hal Murray wrote:
> 
>>>> Yep... I remember a neat paper from colleagues at Trento University that
>>>> piggybacked TCP's ACKs on link layer ACKs, thereby avoiding the collisions
>>>> between TCP's ACKs and other data packets - really nice. Not sure if it
>>>> wasn't just simulations, though.
>> 
>>> that's a neat hack, but I don't see it working, except when one end of the
>>> wireless link is also the endpoint of the TCP connection (and then only for
>>> acks  from that device)
>> 
>> That could be generalized to piggybacking any handy small packet onto the
>> link layer ACK.
>> 
>> Of course, then you have to send back a link layer ACK for the extra info.
>> Does that converge?
> 
> if you aren't talking between the two endpoints of the wireless connection, probably :-)
> 
> but fairness would be an issue for something like this. what constitues a 'small amount of data' to try and piggyback, and what happens if you are talking between endpoints, are the two allowed to monopolize the airtime?

I agree - there'd have to be a size limit placed on what you really do piggyback on link layer ACKs. TCP ACK size can vary, depending on SACK...


> but backing up a step, finding airtime for the ack is just as hard as finding airtime for the next transmission.

I think not, don't link layer ACKs get to use a smaller CW? Or is this just me remembering it wrongly?

Cheers,
Michael