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- 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.

See Integrated Services Digital Network.
Session-Initiation Protocol. A signaling protocol used for establishing sessions in an IP network. A session could be a simple, two-way telephone call, or it could be a collaborative multi-media conference session.
See Programmable Protocol Language.
In PPL, a condition that, when met, drives a state machine (PPL Component) from one state to another, by invoking an associated Primitive. In PPL files, an Event is marked by an arrow and text.
A condition that, when met, drives a state machine from one state to another. A condition that drives a Component out of its current state by invoking an associated primitive.