DLPI Programmer's Guide

Chapter 1 41
Introduction to DLPI
DLPI Services
Figure 1-22 Message Flow: Simultaneous DLS User & DLS Provider Invoked
Connection Release
Reset Service
The reset service may be used by the DLS user to resynchronize the use
of a data link connection, or by the DLS provider to report detected loss
of data unrecoverable within the data link service.
Invocations of the reset service will unblock the flow of DLSDUs if the
data link connection id congested; DLSDUs may be discarded by the DLS
provider. The DLS user or users that did not invoke the reset will be
notified that a reset has occurred. A reset may require a recovery
procedure to be performed by the DLS users.
The interaction between each DLS user and the DLS provider will be one
of the following:
• a DL_RESET_REQ from the DLS user, followed by a
DL_RESET_CON from the DLS provider,
• a DL_RESET_IND from the DLS provider, followed by a
DL_RESET_RES from the DLS user.
The DL_RESET_REQ acts as a synchronization mark in the stream of
DLSDUs that are transmitted by the issuing DLS user; the
DL_RESET_IND acts as a synchronization mark in the stream of
DLSDUs that are received by the peer DLS user. Similarly, the
DL_RESET_RES acts as a synchronization mark in the stream of
DLSDUs that are transmitted by the responding DLS user; the
DL_RESET_CON acts as a synchronization mark in the stream of
DLSDUs that are received by the DLS user which originally issued the
reset.
The resynchronizing properties of the reset service are:
• No DLSDU transmitted by the DLS user before the synchronization
mark in that transmitted stream will be delivered to the other DLS
user after the synchronization mark in that received stream.
DL_DISCONNECT
request
DL_DISCONNEC
T
indication
DL_OK
acknowledge