Transport Protocols

Sandwiched between the NDIS interface and the TDI are transport protocol device drivers. These drivers communicate with a network adapter card via a NDIS-compliant device driver.

Figure 1.6 Transport Protocols

Windows NT includes these transports:

• NBF is a transport protocol derived from NetBEUI and provides compatibility with existing LAN Manager, LAN Server, and MS-Net installations. (For more information, see Chapter 6, "Using NBF with Windows NT.")
• TCP/IP is a popular routable protocol for wide-area networks.
• NWLink is an NDIS-compliant version of Internetwork Packet Exchange (IPX/SPX) compatible protocol. It can be used to establish connections between Windows NT computers and either MS-DOS, OS/2, Windows, or other Windows NT computers via RPC, Sockets, or Novell NetBIOS.
• Microsoft Data Link Control (DLC) provides an interface for access to mainframes and network attached printers. (For more information, see Chapter 7, "Using DLC with Windows NT.")
• AppleTalk supports Services for Macintosh in Windows NT Server. Developers using Windows NT Workstation can also install the AppleTalk protocol, as needed, when developing AppleTalk-compliant programs.

Transport Protocols and Streams

Windows NT supports Streams-compliant protocols provided by third parties. These protocols use Streams as an intermediary between the protocol and next interface layer (NDIS on the bottom and TDI on top). Calls to the transport protocol driver must first go through the upper layer of the Streams device driver to the protocol, then back through the lower layer of Streams to the NDIS device driver.

Using Streams makes it easier for developers to port other protocol stacks to Windows NT. It also encourages protocol stacks to be organized in a modular, stackable style, which is in keeping with the original OSI model.