Introduction to DLPI
DLPI Services
Figure 1-22 Message Flow: Simultaneous DLS User & DLS Provider Invoked Connection Release
DL_DISCONNECT request
DL_OK acknowledge
DL_DISCONNECT indication
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.
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