Re: [lwip-users] why ACK is happen every package

[Kieran Mansley]

On Wed, 2010-03-10 at 13:02 +0800, yueyue papa wrote:
> Hi All,
> 
> The lwIP 1.3.2 is used.  I found the my lwIP ack the data every TCP
> segment.  Why i meet this result?
> 
> The ACK should not happen every TCP segment. The lwipopts.h is
> attached.

I think the ACKs are being sent because there has been a significant
change in the available receive window.  Before each ACK there is zero
window available, and so once a certain amount becomes available it
makes sense to tell the sender about it straight away.  There is a
configuration option for this: TCP_WND_UPDATE_THRESHOLD.  The default
value for this is TCP_WND/4  (despite the comment in tcp.c saying it is
TCP_WND/2!).  If you want to send window updates less frequently, you
can make that value bigger by adding it to your lwipopts.h, at the risk
of reduced performance.

Kieran