Re: [lwip-users] Duplicate acks

[Kieran Mansley]

On Thu, 4 Mar 2004, Leon Woestenberg wrote:

> Hello Kieran,
>
> Kieran Mansley wrote:
>   >
> > The second ACK probably differs from the first in that it will contain a
> > larger advertised window.  It can do this as you've called tcp_recved and
> > so processed some data and so it is safe to increase the window.
> >
> > So, what happens is (or should be) something like this:
> >
> Thanks for the clear explanation Kieran.
>
> Could you please commit a small comment at that spot in the code which
> summarizes this? :-) Thanks!

Done.  Now reads...

    /*
     * We send an ACK here (if one is not already pending, hence
     * the above tests) as tcp_recved() implies that the application
     * has processed some data, and so we can open the receiver's
     * window to allow more to be transmitted.  This could result in
     * two ACKs being sent for each received packet in some limited cases
     * (where the application is only receiving data, and is slow to
     * process it) but it is necessary to guarantee that the sender can
     * continue to transmit.
     */

Kieran