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]

Stephen Hurd schrieb am 18.02.2010 17:09 (localtime):
...
> A TCP SHOULD implement a delayed ACK, but an ACK should not be 
> excessively delayed; in particular, the delay MUST be less than 0.5 
> seconds, and in a stream of full-sized segments there SHOULD be an ACK 
> for at least every second segment.

That's why I asked for help understandig TCP. I'm surely wrong then. I 
thought the ACK segment gets sent after the transfer of n segments 
equals windows-size. I don't undesrtand that window size yet... I'm back 
into my books

> The idea of delayed ACKs is to allow an ACK to be sent with data if 
> there will be data sent right away, not to combine ACKs... leaving out 
> ACKs makes calculation of RTT problematical which causes performance 
> problems all over the place... maybe the dearth of ACKs from the windows 
> system is causing the problem?

The problem is not with the windows box, these transfer rates are 
sensible. The problem is with two RELENG_8 machines.

I'm doing this whole thing because I observed slowdowns under 20MB/s and 
I try to reproduce and investigate this. But first I have to get the 
idea right... If I don't understamd things going on when transfers make 
sense, I won't be able to determine what happens when transfers are 
slowed down...

Thanks,

-Harry

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