Re: [lwip-devel] TCP ack timing

[K.J. Mansley]

On Fri, 2004-04-30 at 14:02, Leon Woestenberg wrote:
> Hello,
> 
> K.J. Mansley wrote:
> 
> > This suggests that the second limit is not being obeyed.  Having had a
> > look at the code, lwIP uses a slightly different algorithm: it sends the
> > ACK if *two ACKs* have been requested, not if *two MSS of data need
> > ACKing*.  This could result in the behaviour you're seeing if you have a
> >
> At what place in the lwIP code do we have those numbers available to 
> check against? (Note: I am not very familiar with lwIP TCP, *still*).
> 
> I mean the amount of received data that still has to be acknowledged.

In my fork of lwIP I compare pcb->rcv_nxt to pcb->last_ack_sent, but
maybe last_ack_sent is something I added myself long ago and have since
forgotton, as I don't see it in the savannah tree!

Anyway, I think that even with that change the original poster would see
the same problem, as the max segment size must be less than half the
receive window for the algorithm to work.

Kieran