- Call Setup - User Side

When an ISDN call is set up and answered and the SIP caller goes on hold, the host sends a PPL Event Request message (0x44) with event SUSPEND to the CSP.

The PPL Event Request is verified and ACKed. When the SUSPEND has been processed, the CSP will send a PPL Event Indication message (0x43) signifying success, rejection, or timeout.

Call Flows

The following are call flows for the various scenarios:

Figure 3 Successful SUSPEND Request

Figure 4 SUSPEND Request Rejected

Figure 5 SUSPEND Request Times Out

Re-establishing the call

When the user wants to re-establish the call, the host will send a PPL Event Request message (0x44) with event RESUME to the CSP. The PPL Event Request will be verified and ACKed. When the RESUME has been processed the CSP will send a PPL Event Indication message (0x43) signifying success, rejection or timeout.