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The Data Link Provider Interface (DLPI) is a UNIX STREAMS standard that defines the interface to the Data Link Layer of the OSI reference model. For SCO UnixWare 1 and 2 systems, DLPI is used to implement network adapters.
For UnixWare 7 and SCO OpenServer, the DLPI driver is separate from the network card driver interface; network adapters are implemented with the MDI, and DLPI is used only to implement support for different media types. Instances of a DLPI ``module'' are linked to individual MDI drivers to provide common media-dependent services. DLPI exists as a driver that is separate from the network adapter driver. It is accessed through the netX device node (where X is the number of the associated network adapter). The network adapter has a separate device node that is an open-once type device which the DLPI support daemons hold open. MDI commands can be passed through the DLPI device down to the MDI network adapter device.
For example, if two Western Digital 8013 network adapters are configured, the first one uses the net0 DLPI device and the /dev/mdi/wdn0 MDI device. The second network adapter that is configured uses the net1 DLPI device and the /dev/mdi/wdn1 MDI device. If the second MDI device is a different type of network adapter, the MDI device node would be 0, so /dev/mdi/cet0 might be the MDI device node that corresponds to the net1 DLPI device.
The UnixWare 7 and SCO OpenServer DLPI supports all SCO UnixWare 2.0 protocol stacks. Most SCO UnixWare 2.0 DLPI drivers can be installed and executed on UnixWare 7 systems but cannot be rebuilt and will probably not be portable to future releases of the operating system.
For more information about the DLPI module, see the dlpid(1M) manual page.