Cisco Cisco Unified Contact Center Management Portal 8.5 Leaflet

PG side A detects a failure and induces a failover to PG side B.

Depending on the configuration of the Peripheral in Unified ICM, the CTI OS or CAD server will 
keep the agent logged in but "gray out" their desktop controls until the PG has completed its failover 
processing. The agents might not have to log in again but might have to manually make themselves 
"ready" or "available" to ensure they are aware the call processing functionality has been restored.

PG side B becomes active and registers all dialed numbers and phones, and call processing 
continues.

As noted above, when the PG fails-over, the ICM Call Router will write a Termination Call Detail 
Record (TCD) in the ICM database for any active calls. If the call is still active when the PG 
fails-over to the other side, a second TCD record will be written for this call as if it were a "new" 
call in the system and not connected to the prior call that was recorded in the database.

When Unified CM subscriber A recovers, all idle phones and gateways re-home to it. Active devices 
wait until they are idle before re-homing to the primary subscriber.

PG side B remains active, using the CTI Manager on Unified CM subscriber B.

After recovery from the failure, the PG does not fail back to the A side of the duplex pair. All CTI 
messaging is handled using the CTI Manager on Unified CM subscriber B, which communicates 
with Unified CM subscriber A to obtain phone state and call information.

ICM synchronzation messages
Unified CM intra-cluster messages
JTAPI messages
H323 or MGCP messages
SCCP messages

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Unified CM B

Unified CM A

Fails

Agent PG A

Agent PG B