RELENG_8 ignoring TCP window size? [Was: Re: Help for TCP understanding wanted, ACK-MSS-Window [Was: Re: best practice to watch TCP parms of established sockets]]

[Stephen Hurd]

Harald Schmalzbauer wrote:
> Some experimental results:
> When rsyncing with windows, and FreeBSD is receiver, I see the same 
> ACK ever two segemnts, but speed is at 72MB/s.
> When FreeBSD is sender and Windows is receiver, it looks more I 
> expected. There are about 20 data segments before a ACK is returned. 
> And there are  TCP Window Update Segments, reflecting smaller receiver 
> buffers on the windows side. But this happens at a throughput of 
> 82MB/s!!! So the windows machine is behaving like I understand the TCP 
> flow control.
> Any explanation why the FreeBSD machine seems to ignore window size?

IIRC, the delayed ACK RFC requires an ACK at least every second segment.