TDI Interface

Software programs that rely on NBFP for network communication require a transport driver that exposes the NetBIOS interface. However, instead of exposing the NetBIOS interface, the Windows 2000–based transport drivers expose the more flexible Windows 2000 TDI interface, which in addition to supporting NBF, also serves as a common interface to support protocols such as IPX and TCP/IP.

Figure 16.2 shows how NBFP is exposed through the Transport Driver Interface (TDI).

Figure 16.2 Transport Driver Interface (TDI) and NBF

Windows 2000 TDI provides a NetBIOS emulator that maps NetBIOS commands to TDI commands to support applications designed for use with NBFP. NetBIOS commands are formatted as network control blocks (NCBs). When a program running on a Windows 2000–based computer creates an NCB, the NetBIOS command is first processed by the Windows 2000–based NetBIOS driver (Netbios.sys). Netbios.sys processes the NCB by mapping it to the corresponding TDI commands, and sends the TDI command to the Windows 2000–based NetBEUI driver (Nbf.sys). TDI calls implement the same general semantics as NetBIOS NCBs, but are optimized for a 32-bit kernel interface.

Note

Legacy 16-bit Windows 2000 and Microsoft® MS-DOS® transport clients send NCBs directly to the NetBEUI driver.