HP UX 11i v2 Networking Software manual Modes of Communication, Connection-mode Service

Introduction to DLPI

The Data Link Layer

endpoint between a DLS user and the DLS provider. After the stream is created, the DLS user and DLS provider communicate via messages discussed later.

DLPI is intended to free data link users from specific knowledge of the characteristics of the data link provider. Specifically, the definition of DLPI hopes to achieve the goal of allowing a DLS user to be implemented independent of a specific communications medium. Any data link provider (supporting any communications medium) that conforms to the DLPI specification may be substituted beneath the DLS user to provide the data link services. Support of a new DLS provider should not require any changes to the implementation of the DLS user.

Modes of Communication

Although DLPI supports three modes of communication, Hewlett-Packard supports connection and connectionless modes. The connection mode is circuit-oriented and enables data to be transferred over a pre-established connection in a sequenced manner. Data may be lost or corrupted in this service mode due to provider-initiated resynchronization or connection aborts.

The connectionless mode is message-oriented and supports data transfer in self-contained units with no logical relationship required between units. Because there is no acknowledgment of each data unit transmission, this service mode can be unreliable in the most general case. However, a specific DLS provider can provide assurance that messages will not be lost, duplicated, or reordered.

Raw mode interface is also supported. Raw mode allows the DLS user to send and receive packets with complete LLC and MAC header information.

Connection-mode Service

The connection-mode service is characterized by four phases of communication:

•Local Management

•Connection Establishment

•Data Transfer

•Connection Release

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