HP UX 11i v2 Networking Software Figure, Abstract View of DLPI

Introduction to DLPI

The Data Link Layer

Figure 1-1 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, plus 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, an effort is underway to develop service interfaces that map to the OSI Reference Model. A set of kernel-level interfaces, based on the STREAMS development environment, constitute a major portion of this effort. The service primitives that make up these interfaces are defined as STREAMS messages that are transferred between the user and provider of the service. DLPI is one such kernel-level interface, and is targeted for STREAMS protocol modules that either use or provide data link services. In addition, user programs that wish to access a STREAMS-based data link provider directly may do so using the putmsg(2) and getmsg(2) system calls.

Referring to Figure 1-1, the DLS provider is configured as a STREAMS driver, and the DLS user accesses the provider using open(2) to establish a stream to the DLS provider. The stream acts as a communication

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