CAF: Call Legs Resync

Call Legs Resynchronization

Since the Toolpack framework has been designed for HA (High_Availability_Overview), it's mandatory that an application that manage calls through CAF_Call_interface is able to deal with call legs re-synchronization.

The current page contains an overview of how re-synchronization works. For more details, please refer to the following page:

CAF:_Working_With_Caf_Call_Legs#Re-synchronizing_with_toolpack_engine

Situations where call leg resynchronization is required

Call legs re-synchronization is required whenever the CAF application looses communication with toolpack_engine:

• The CAF application was restarted
• The toolpack_engine was restarted
• Network connection between CAF application and toolpack_engine was momentarily down

General principles of call legs re-sync

Toolpack Engine

The toolpack_engine application, when restarted, will re-build it's call leg contexts by querying information on the TMedia Units.

• Transient calls (not yet answered) will be dropped
• Terminating calls will be dropped
• Active (answered) calls will be re-build like they were before toolpack_engine was restarted

CAF application

The call control application based on the CAF_Call_interface API will re-build it's call leg contexts by getting information from toolpack_engine.

All active (answered) calls will be re-synchronized from toolpack_engine.

• Calls already known by the application will remain valid
• Calls unknown by the application will be re-constructed (or refused): OnCallLegSync, OnLinkSync
• Calls known by the application, but no more present in toolpack_engine are terminated: OnCallLegTerminated

Re-sync timeout

Upon disconnection with toolpack_engine, the CAF_Call_interface API has a 10 seconds internal timeout waiting for a re-connection.

• During these 10 seconds, call contexts remain valid
• After these 10 seconds, call contexts are locally destroyed (OnCallLegTerminated)
• Calls that would still be present upon a later re-connection with toolpack_engine can be re-constructed (OnCallLegSync)

Note: After 10 seconds of disconnection with toolpack_engine, it makes sense that an application "forgets" about active calls, and writes CDR "END" logs, for example, to avoid billing users for calls that may no more be connected.

Example scenarios

In all the scenarios below, let's consider the following situation:

In this situation, the CAF application was restarted (on purpose, or after a crash). It does a cold start up, without any call leg contexts.

For more information...

The current page contains an overview of how re-synchronization works. For more details, please refer to the following page:

CAF:_Working_With_Caf_Call_Legs#Re-synchronizing_with_toolpack_engine