Atom what your asking really doesn't have any thing to do with that chip. It just sends data and receives data. The Uc that's controlling it handles the type translation.
So the tcip/ip stack would be based on what chip you use and if its a arm or pic.
What uC is controlling it then? If you are refering to what ever micro i decide to use then how is that possible? Why is this SPI then? What are the SPI Commands?