Re: [lwip-users] Re: Desired - reference netconn_write() to external memory

[Çağlar AKYÜZ]

Kieran Mansley yazmış:
> On Wed, 2006-10-11 at 16:25 +0300, Çağlar AKYÜZ wrote:
>
>   
> > Actually I think this will not improve the performance of MAC. Because 
> > ACK'ing of TCP frames is one of the major drawbacks which degrades 
> > performance ( thanks to Delayed ACK algorithm!).
> >     
>
> Only in a very limited set of circumstances will the delayed ACK
> algorithm result in poorer performance.  Namely, when the TCP window has
> been set to a very small value.  Changing this configuration option will
> remove any bottleneck that the delayed ACK algorithm is imposing.  
I tried to increase recieve window but it always resulted in a poorer 
performance with my SAM7X. ( Maybe I'm too low in memory?) . is TCP 
window size related to somewhat pbufs? I don't know if I have to 
increase number of buffers as well.
> There
> are TCP extensions such as the "quickack" mode in linux's TCP stack that
> stop the use of delayed ACK during the slow start phase of TCP
> connections, but the performance difference that this is likely to lead
> to in lwIP is minimal.
>   
Actually I didn't mean to say that problem is related to LWiP. I wanted 
to say that delayed ACK algorithm is slowing TCP connections in our case 
and my Windows machine do not provide me any way to change this setting. 
( Thanks to Linux as you noted. )
> ACKing of packets can be arguably said in fact to increase performance,
> as without it the sender couldn't discover the maximum rate it could
> send without packet loss, and so if it didn't wish to lose data would
> have to be more conservative with how fast it sent packets.
>   
Thanks for this quote. I'll remember this.

Çağlar