Re: [lwip-users] LWIP on a gigabit LAN

[Jonathan Larmour]

Jacob Gorm Hansen wrote:
> On Tue, 2007-04-24 at 14:50 -0700, Roger Cover wrote:
> > Sorry, 8 megabytes. 
>
> In my first tests I seem to be getting around 25-30 megabytes per
> second. I suppose that to get better performance I need TCP Window
> Scaling and perhaps SACK. I found mention of SACK in LwIP here:
> http://edin.no-ip.com/html/?q=node/57 , but am not sure how to find the
> patch for it. Has anyone experimented with Window Scaling?

The patch is in that link! It appears to implement reception (but not 
generation) of SACKs, and window scaling. It would be interesting to 
experiment with, although perhaps my experience with window scaling is 
limited, but the patch doesn't look entirely right, e.g.:

+        pcb->snd_scale = scale;
+        pcb->rcv_scale = 2;

It sets the receiver's scaling to 2, but that is never advertised in the 
SYN (indeed no window scaling is supported for transmission in this patch).

And it all has rather non-deterministic consequences for memory use that 
cannot be limited by the user. Still, this patch looks pretty close.

Jifl
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