ISUP service function summary

The ISUP service provides the following asynchronous functions:

Connection establishment functions

Function	Description
ISUPConnectReq	Requests the establishment of a circuit switched connection.
ISUPConnectResp	Signals the far exchange that an incoming call was answered.
ISUPConnectStatusReq	Sends connection status information to the far exchange during the connection establishment phase.
ISUPStatusReq	Sends a global or circuit-specific message to the far exchange.

Data transfer functions

Function	Description
ISUPDataReq	Sends user-to-user information associated with an established connection to the far exchange.
ISUPResumeReq	Resumes a suspended connection (cancels timer T2) and sends a resume message to the far exchange.
ISUPSuspendReq	Sends a suspend message to the far exchange and starts the suspend timer T2.

Connection clearing functions

Function	Description
ISUPReleaseReq	Clears or denies the establishment of a circuit switched connection.
ISUPReleaseResp	Responds to a release indication from a far exchange.

Miscellaneous functions

Function	Description
ISUPFacilityReq	Sends a facility request message to the far exchange.
ISUPGetApiStats	Retrieves congestion level activity statistics from the ISUP service.
ISUPRawReq	Sends an application-encoded ISUP packet.
ISUPRetrieveMessage	Retrieves the next message from the ISUP layer.