2.1 NLI Overview

The Solstice X.25 Network Layer Interface provides access to the X.25 Packet Layer Protocol (PLP). The NLI defines the format that STREAMS messages must take when interfacing to the network layer. This allows for the easy construction of user level library software, and means that applications map conveniently onto the STREAMS format.

Solstice X.25 applications use the putmsg and getmsg system calls to interact with the PLP driver.

Figure 2-1 NLI and STREAMS

Messages passed using NLI have both a control and a data part. Primitives and associated parameters are passed to the X.25 driver using the control part of the message. Data, if there is any, is contained in the data part of the message.

Figure 2-2 NLI Message Format

Solstice X.25 NLI provides the following:

• NLI messages

  These determine the format of the control parts of putmsg and getmsg, and are used to communicate with the network.

• A series of ioctls

  These communicate with the Solstice X.25 code, rather than with the network.

• A series of library functions

  These are not part of the NLI, but can be used along with it.