HP UX 11i v2 Networking Software manual Dlpi Addressing, Connectionless-mode Service

Introduction to DLPI

The Data Link Layer

Connectionless-mode Service

The connectionless mode service does not use the connection establishment and release phases of the connection mode service. The local management phase is still required to initialize a stream. Once initialized, however, the connectionless data transfer phase is immediately entered. Because there is no established connection, however, the connectionless data transfer phase requires the DLS user to identify the destination of each data unit to be transferred. The destination DLS user is identified by the address associated with that user.

DLPI Addressing

Each user of DLPI must establish an identity to communicate with other data link users. This identity consists of two pieces. First, the DLS user must somehow identify the physical medium over which it will communicate. This is particularly evident on systems that are attached to multiple physical media. Second, the DLS user must register itself with the DLS provider so that the provider can deliver protocol data units destined for that user. Figure 1-2 illustrates the components of this identification approach, which are explained below.

Figure 1-2 Data Link Addressing Components

DLS Users

DLSAP

DLS

Provider

PPA

Physical Media

Physical Attachment Identification

The physical point of attachment (PPA in Figure 1-2) is the point at which a system attaches itself to a physical communications medium. All communication on that physical medium funnels through the PPA. On systems where a DLS provider supports more than one physical medium, the DLS user must identify which medium it will communicate through.

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