You are here: CSP Developer’s Guide: Common Channel Signaling > 8 ISDN > LAPD Example Call Flows
TEI Denied Procedure
The procedure below shows an ID Request from the user side, requesting TEI 11. Management checks the Configuration database but cannot find TEI 11 listed, so it issues an ID Denied. Management sends a PPL Event Indication message to the local host to indicate that this TEI failed assignment procedures.
TEI Already Assigned Procedure
The procedure below shows a check procedure being initiated when a TEI is already assigned. The ID Check Response message returns the same TEI, and the TEI failure is propagated to the host.
The figure below illustrates a query for the state of a specific TEI/SAPI combination on a D channel. The PPL Event Request message contains the following:
• addresses a slot
• D channel number
• SAPI
• TEI
The result appears in a PPL Event Indication message containing an LAPD Status ICB.
