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]]

Harald Schmalzbauer h.schmalzbauer at
Thu Feb 18 16:04:38 UTC 2010

Stephen Hurd schrieb am 18.02.2010 17:01 (localtime):
> 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.

Good hint, but disabling leads to ACK after every single data segment ?!?



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