HP 800 HP DLPI Programmer's Guide - Page 24

Introduction to DLPI The Data Link Layer Figure 1-2 Connection Release This phase enables either the DLS user or the DLS provider to break an established connection. The release procedure is considered abortive. Therefore, any data that has not reached the destination user when the connection is released may be discarded by the DLS provider. 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, the connectionless data transfer phase is immediately entered. Since there is no established connection, the connectionless data transfer phase expects 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 in the sections that follow. Data Link Addressing Components DLS Users DLSAP PPA Physical Media DLS Provider 24 Chapter 1