It might help to elaborate a little - are you asking about how your device would be connected to the computer (USB, Ethernet etc.) or how each end of those protocols is implemented, or something else? And what do you mean by "high bandwidth"? I'm not really qualified to answer you anyway, but I know you can implement things like USB and Ethernet in an FPGA, or you can use separate ICs that handle these things by exposing a serial or parallel interface to your FPGA (UART, SPI etc.).