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 manages calls through CAF_Call_interface is able to deal with call legs re-synchronization.

This article contains an overview of how resynchronization works. For more details, please refer to the following section:

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 loses 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 its 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 rebuilt like they were before toolpack_engine was restarted

CAF application

The CAF call control application that was disconnected from toolpack_engine will update (or rebuild) its call leg contexts by getting information automatically pushed by toolpack_engine upon reconnection.

All active (answered) calls will be resynchronized from toolpack_engine.

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

Example scenarios

Example scenario: Initial state

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

• Leg-A: Ringing
• Leg-B: Terminating
• Leg-C: Active (answered)
• Leg-D: Active (answered)
• Leg-E: Active (answered)
• Leg-C and Leg-D are joined (connected) together
• Mixer-1: Ready
• Leg-E and Mixer-1 are joined (connected)

Scenario 1: toolpack_engine quickly restarted

Example scenario 1

• CAF Application is notified
  • OnCmcLibNotReady()
  • OnSyncLost() for Leg-A, Leg-B, Leg-C, Leg-D and Leg-E
  • OnMixerSyncLost() on Mixer-1
• toolpack_engine restarts
  • Queries information from all TMedia units
  • Drop incomplete legs and mixers (here Leg-A and Leg-B)
  • Re-build contexts for active legs and mixers (here Leg-C, Leg-D, Leg-E and Mixer-1)
  • Re-build connections between legs/mixers (here Leg-C with Leg-D, Leg-E with Mixer-1)
• toolpack_engine pushes information to CAF library:
  • Legs: Leg-C, Leg-D and Leg-E
  • Mixers: Mixer-1
  • Connections: Leg-C with Leg-D, Leg-E with Mixer-1
• CAF library compares with it's own contexts:
  • OnCallLegTerminated() for Leg-A and Leg-B
  • OnSyncDone() for Leg-C, Leg-D and Leg-E
  • OnMixerSyncDone() for Mixer-1
• Ready to continue
  • OnCmcLibReady()

Scenario 2: toolpack_engine stopped (disconnected) for more than 10 seconds

Example scenario 2

• CAF Application is notified
  • OnCmcLibNotReady()
  • OnSyncLost() for Leg-A, Leg-B, Leg-C, Leg-D and Leg-E
  • OnMixerSyncLost() on Mixer-1

(... 10 seconds elapse...)

• CAF Application declares toolpack_engine "dead", destroys all it's local contexts:
  • OnCallLegTerminated() for all legs: Leg-A, Leg-B, Leg-C, Leg-D and Leg-E
  • OnMixerTerminated() for all mixers: Mixer-1

(... some time elapse...)

• toolpack_engine is restarted
  • Queries information from all TMedia units
  • Drop incomplete legs and mixers (here Leg-A and Leg-B)
  • Re-build contexts for active legs and mixers (here Leg-C, Leg-D, Leg-E and Mixer-1)
  • Re-build connections between legs/mixers (here Leg-C with Leg-D, Leg-E with Mixer-1)
• toolpack_engine pushes information to CAF library:
  • Legs: Leg-C, Leg-D and Leg-E
  • Mixers: Mixer-1
  • Connections: Leg-C with Leg-D, Leg-E with Mixer-1
• CAF library compares with it's own contexts (none!):
  • OnCallLegSync() for Leg-C, Leg-D and Leg-E
    • Application may refuse them: RefuseLeg()
    • Application may re-allocate new contexts for these legs
  • OnMixerSync() for Mixer-1
    • Application may refuse: RefuseMixer()
    • Application may re-allocate new contexts for these mixers
  • OnLinkSync() for Leg-C with Leg-D
    • Application may refuse: RefuseLink()
    • Application may re-allocate new "call flow" contexts, re-bind legs to them (BindCallLeg)
  • OnMixerLinkSync() for Leg-E with Mixer-1
    • Application may refuse: RefuseMixerLink()
    • Application may re-allocate new "call flow" contexts, re-bind legs/mixers to them (BindCallLeg, BindMixer)
• Ready to continue
  • OnCmcLibReady()

Scenario 3: CAF application is restarted

Example scenario 3

• If the application is quitting in a 'clean' manner
  • 'OnLegFreed()' is called for all call legs (Leg-A, Leg-B, Leg-C, Leg-D and Leg-E)
  • Destructor of all call flows is called
• When the application is restarted
  • => This is exactly the same scenario as the end of Scenario 2 after step 'toolpack_engine pushes information to CAF library'.

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