Limitations

•A least one TPO in the cluster must be in Active state when the turret's user logs -in.

If a turret's user logs-in when no  TPO is in Active state and after a while a TPO is Active, this user must log-out then log-in to register to this  TPO.

•Only TCP transport and bulk registration are supported on the Cisco call manager.

•Network infrastructure must ensure SIP PUBLISH messages are allowed over UDP between turrets and TPOs to ensure TPO hot-backup works properly

•Intermittent cuts of network (Flip/Flop state) may cause TPO Split Brain (several TPOs running the same Group ID).

•Incoming call are saved however if remote party hangup between TPO1 failure and TPO2 recovery or after TPO2 recovery then the turret cannot be notified that the call has disappeared, user will try to accept the incoming call and the call will then be cleaned up.

•TPO is not able to recover current ongoing calls for a specific scenario

- CuCM: CuCM1 publisher and CuCM2 subscriber

- TPO cluster: TPO1 Active, TPO2 Passive and TPO3 Passive

1.TPO1 registers to CuCM1

2.TPO1 has several ongoing calls

3.CuCM1 is out of service

4.TPO1 registers to CuCM2

5.TPO1 fails

6.TPO2 becomes active => the current ongoing calls are not preserved.

•User is unable to log in a second time on FlexGo after 10 minutes between first login and second one in specific scenario

- TPO cluster: TPO1 Active, TPO2 Passive and TPO3 Passive

1. User logs on FlexGo at time X

2. (Optional) User calls IPPhone

3. (Optional) IPPhone answers and call is established between User and IPPhone

4. TPO1 fails

5. TPO2 becomes active. (Optional) Call between User and IPPhone is preserved

6. (Optional) User or IPPhone ends call

7. User logs out

8. User logs in at time Y

If (Y - X) < 10 minutes, user cannot logs in because FlexGo has DNS cache of 10 minutes. Otherwise, user can logs in.

•In Session Persistency, there MUST be at least one witness node  for successful failover to take place

1. For example, TPO cluster: TPO1 Active, TPO2 Passive and TPO3 Passive

2. When TPO1 is dead due to Network issue/Application crash, TPO2 becomes Active, TPO3 stays Passive

3. Before recovering TPO1, If TPO2 is also dead due to Network issue/Application crash then TPO3 remains Passive as there is no witness TPO  to support TPO3 transition to Active role.