Cisco Unified Contact Center Enterprise Solution Reference ...
Cisco Unified Contact Center Enterprise Solution Reference ...
Cisco Unified Contact Center Enterprise Solution Reference ...
You also want an ePaper? Increase the reach of your titles
YUMPU automatically turns print PDFs into web optimized ePapers that Google loves.
Understanding Failure Recovery<br />
3-38<br />
<strong>Cisco</strong> <strong>Unified</strong> <strong>Contact</strong> <strong>Center</strong> <strong>Enterprise</strong> 7.x SRND<br />
Chapter 3 Design Considerations for High Availability<br />
to store in the system database. Because the Call Routers are synchronized, the Logger data is also<br />
synchronized. In the event that the two Logger databases are out of synchronization, they can be<br />
resynchronized manually by using the <strong>Unified</strong> ICMDBA application over the private LAN. The<br />
Logger also provides a replication of its historical data to the customer Historical Database Server<br />
(HDS) Administrative Workstations over the visible network.<br />
In the event that one of the <strong>Unified</strong> ICM Call Routers should fail, the surviving server will detect the<br />
failure after missing five consecutive TCP keep-alive messages on the private LAN. The Call Routers<br />
generate these TCP keep-alive messages every 100 ms, so it will take up to 500 ms to detect this failure.<br />
Upon detection of the failure, the surviving Call Router will contact the Peripheral Gateways in the<br />
system to verify the type of failure that occurred. The loss of TCP keep-alive messages on the private<br />
network could be caused by either of the following conditions:<br />
Private network outage — It is possible for the private LAN switch or WAN to be down but for both<br />
of the <strong>Unified</strong> ICM Call Routers to still be fully operational. In this case, the Peripheral Gateways<br />
will still see both of the <strong>Unified</strong> ICM Call Routers even though they cannot see each other over the<br />
private network. In this case, the Call Routers will both send a Test Other Side message to the PGs<br />
to determine if the Call Router on the other side is still operational and which side should be active.<br />
Based upon the messages from the PGs, the Call Router that previously had the most active PG<br />
connections would remain active in simplex mode, and the Call Router on the other side would go<br />
idle until the private network is restored.<br />
Call Router hardware failure — It is possible for the Call Router on the other side to have a physical<br />
hardware failure and be completely out of service. In this case, only the surviving Call Router would<br />
be communicating with the Peripheral Gateways using the Test Other Side message. The Peripheral<br />
Gateways would report that they can no longer see the Call Router on the other side, and the<br />
surviving Call Router would take over the active processing role in simplex mode.<br />
During the Call Router failover processing, any Route Requests sent to the Call Router from a Carrier<br />
Network Interface Controller (NIC) or Peripheral Gateway will be queued until the surviving Call<br />
Router is in active simplex mode. Any calls in progress in the IVR or at an agent will not be impacted.<br />
If one of the <strong>Unified</strong> ICM Logger and Database Servers were to fail, there would be no immediate impact<br />
except that the local Call Router would no longer be able to store data from call processing. The<br />
redundant Logger would continue to accept data from its local Call Router. When the Logger server is<br />
restored, the Logger will contact the redundant Logger to determine how long it had been off-line. If the<br />
Logger was off-line for less than 12 hours, it will automatically request all the transactions it missed<br />
from the redundant Logger while it was off-line. The Loggers maintain a recovery key that tracks the<br />
date and time of each entry recorded in the database, and these keys are used to restore data to the failed<br />
Logger over the private network.<br />
If the Logger was off-line for more than 12 hours, the system will not automatically resynchronize the<br />
databases. In this case, resynchronization has to be done manually using the <strong>Unified</strong> ICMDBA<br />
application. Manual resynchronization allows the system administrator to decide when to perform this<br />
data transfer on the private network, perhaps scheduling it during a maintenance window when there<br />
would be little call processing activity in the system.<br />
The Logger replication process that sends data from the Logger database to the HDS Administrative<br />
Workstations will automatically replicate each new row written to the Logger database when the<br />
synchronization takes place as well.<br />
There is no impact to call processing during a Logger failure; however, the HDS data that is replicated<br />
from that Logger would stop until the Logger can be restored.<br />
Additionally, if the <strong>Unified</strong> OUTD is used, the Campaign Manager software is loaded on only one of the<br />
Logger platforms (typically Logger A). If that platform is out of service, any outbound calling will stop<br />
until the Logger can be restored to operational status.<br />
OL-8669-05