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.