Windows NT has a netdtect.sys support driver that allows user applications to perform a narrow range of physical I/O and memory operations. The driver exports its capabilities to user applications running in the Win32 subsystem. This is accomplished through the netdtect.dll, which verifies that interface resources, such as IRQs, are available for use.
Every NIC has an associated DLL that instructs the support driver DLL on how to interact with that network adapter. This allows the installer to interact directly with a NIC even though the NIC-specific driver has not been loaded.
The Windows NT NIC level DLL interface allows a variety of NICs to be controlled by a single DLL. For information on the entry points for the NIC detection DLLs, see Chapter 9.