HP 800 HP DLPI Programmer's Guide - Page 21

Figure 1-1 Introduction to DLPI The Data Link Layer DLPI is an implementation of the first type of standard. It specifies an interface to the services of the data link layer. Figure 1-1 illustrates how DLPI performs this function. Abstract View of DLPI Data Link User Request/Response Primitives DLPI Indication/Confirmation Primitives Data Link Provider The data link interface is the boundary between the network and the data link layers of the OSI Reference Model. The network layer entity is the user of the services of the data link interface (DLS user), and the data link layer entity is the provider of those services (DLS provider). This interface consists of a set of primitives that provide access to the data link layer services. In addition, it provides the rules for using those primitives (state transition rules). A data link interface service primitive might request a particular service or indicate a pending event. To provide uniformity among the various UNIX system networking products, service interfaces that map to the OSI Reference Model are developed. A set of kernel-level interfaces, based on the STREAMS development environment, constitute a major portion of this development. The service primitives that make up these interfaces are defined as STREAMS messages. These messages are transferred between the user and provider of the service. DLPI is one such kernel-level interface, and is targeted for STREAMS protocol modules Chapter 1 21