RE: [lwip-users] Which opt.h options effect TCP receive throughput?

[Bill Auerbach]

Thanks Kieran.

> There are I suppose a couple of theoretical limits:
>  - your physical layer bandwidth minus the TCP/IP header overhead
> (likely to be a few percent)
> 
>  - if you are window limited: bandwidth = TCP_WND / round trip time.
> i.e. if you can increase the TCP_WND or decrease the round trip time you
> should get increased bandwidth.

Isn't 65535 the maximum value for TCP_WND?  I got the nice warning added to
init.c when I went above this.  I do not know how to decrease the round trip
time.

> You say that "98% of the processor is processing lwIP timers and
> checking for Ethernet packets".  That seems like a lot, and if your CPU
> is saturated like that you're probably at the limit of your performance
> without offloading something like checksum calculation if you aren't
> already.

Sorry, I mean 98% of the processor is dedicated to supporting TCP/IP.
Eventually I have to process the incoming data (which will be a small
fraction of CPU time) but for now, nothing else is going except to receive a
2MB image and copy it to a contiguous memory space.

Bill