In the ReadMe.txt file,
<div class='quotetop'>QUOTE </div>
--- Quote Start ---
- lwipopts.h: Default values and features for building the LWIP stack.
This set will work for most applications. Care must be taken to fully
understand the implications of changing any default value. Refer to
/lwip-0.7.1/src/include/lwip/opt.h for other features or values that can
have a default in lwipopts.h.[/b]
--- Quote End ---
There are also options that you can try at the HAL level (on the system library properties page) that will reduce the memory footprint.
I've not tried any of this, myself, but it seems like a reasonable place to start.
Cheers,
slacker