LAPD primitives

The following table summarizes the supported LAPD primitives:

Message type

Description

DL_DA_IN

Indicates that the trunk from the remote party has received a packet of acknowledged data.

DL_DA_RQ

Requests that the stack transmit a packet of acknowledged data. Sent by the application to the NMS ISDN protocol stack.

DL_EST_CO

Indicates that equipment on the remote side of the ISDN trunk has acknowledged a SABME message sent by the ISDN protocol stack, and has sent back a UA message indicating that the data link is established.

DL_EST_IN

Indicates that the NMS ISDN protocol stack has received a SABME message. The stack automatically acknowledges the message by sending back a UA message, and establishes the data link.

DL_EST_RQ

Requests that the stack establish a data link. The stack transmits a SABME message over the trunk. Sent by the application to the NMS ISDN protocol stack.

DL_REL_IN

If the NMS ISDN software is in the IDLE state, this message indicates that an establishment request sent by the NMS ISDN protocol stack was not successfully answered. If the software is in the DATA_LINK_ESTABLISHED state, this message indicates that the data link has been broken.

DL_U_DA_IN

Indicates that the trunk from the remote party has received a packet of unacknowledged data.

DL_U_DA_RQ

Requests that the stack transmit a packet of unacknowledged data. Sent by the application to the NMS ISDN protocol stack