Overview of Data Link Control

The DLC protocol driver is provided with Microsoft® Windows® 95, Microsoft® Windows® 98, Microsoft® Windows NT® version 4.0 and earlier, and Windows 2000. This driver enables the computer to communicate with other computers running the DLC protocol stack, such as IBM mainframes; and network peripherals, such as print devices that use a network adapter to connect directly to the network. The DLC protocol driver provides access to Institute of Electrical and Electronics Engineers, Inc. (IEEE) 802.2 class I and class II services. It also provides a direct interface to send and receive 802.3 and other Ethernet-type network frames, as well as raw 802.5 frames.

The interface consists of a dynamic-link library (DLL) and a device driver. These services are available with network cards that use Windows network driver interface specification (NDIS)–compliant drivers. Windows 2000–based DLC works with either Token Ring or Ethernet Media Access Control Drivers, and can transmit and receive Digital Intel Xerox (DIX) format frames when bound to Ethernet Media Access Control.

Windows 2000–based DLC contains an 802.2 logical link control (LLC) finite state machine which is used when transmitting and receiving type 2 connection-oriented frames. DLC can also transmit and receive type 1 connectionless frames, such as unnumbered information frames. Type 1 and 2 frames can be transmitted and received simultaneously.

The DLC interface can be accessed from 32-bit Windows 2000–based programs as well as from 16-bit MS-DOS-based and 16-bit Windows-based programs. The 32-bit interface conforms largely to the Command Control Block (CCB) 2 interface, in which the segmented 16-bit pointers are replaced with flat 32-bit pointers. The 16-bit interface conforms to the CCB1 interface.

Windows 2000–based DLC does not support the transport driver interface (TDI) as other Windows 2000–based transport protocols do. Because of this, DLC cannot be used for communication with TDI client applications such as the Windows 2000 redirector and server. Because the redirector cannot use DLC, this protocol is not used for normal session communication between Windows 2000–based computers.