DLPI Programmer's Guide

Chapter 1 31
Introduction to DLPI
DLPI Services
Attach Service
The attach service assigns a physical point of attachment (PPA) to a
stream. This service is required for style 2 DLS providers to specify the
physical medium over which communications will occur. The DLS
provider indicates success with a DL_OK_ACK message and failure with
a DL_ERROR_ACK message. The normal message sequence is
illustrated in Figure 1-4.
Figure 1-4 Message Flow: Attaching a Stream to a Physical Line
A PPA may be disassociated with a stream using the
DL_DETACH_REQ. The normal message sequence is illustrated in
Figure 1-5.
Figure 1-5 Message Flow: Detaching a Stream to a Physical Line
Bind Service
The bind service associates a data link service access point (DLSAP) with
a stream. The DLSAP is identified by a DLSAP address.
DL_BIND_REQ requests that the DLS provider bind a DLSAP to a
stream. It also notifies the DLS provider to make the stream active with
respect to the DLSAP for processing connectionless data transfer and
connection establishment requests. DL_SUBS_BIND_REQ provides the
added capability on binding on multiple DLSAP addresses.
DL_ATTACH
request
DL_OK
acknowledge
DL_DETACH
request
DL_OK
acknowledge