Identify your NIC

The documentation for the hardware should describe the type of chipset used.

If you don't know what type of chipset you're using, you can identify it using pci -vvv.

Find the entry for the Network controller and it'll give you details on the manufacturer/vendor ID and device ID. Either find the information on the manufacturer's website, or use the vendor ID and device ID to cross-reference it with this online site: