Cisco Unified Contact Center Enterprise Solution Reference ...

Understanding Failure Recovery
Unified ICM
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Cisco Unified Contact Center Enterprise 7.x SRND
Chapter 3 Design Considerations for High Availability
The Unified ICM is a collection of services and processes running on Unified ICM servers. The failover
and recovery process for each of these services is unique and requires carefully examination to
understand the impact to other parts of the Unified CCE solution, including another Unified ICM service.
As stated previously, all redundant Unified ICM servers discussed in this chapter must be located at the
same site and connected through a local private LAN or crossover cable. You can provide the private
LAN by installing a second network interface card (NIC) in each server (sides A and B) and connecting
them with a crossover cable. By doing so, you can eliminate all external network equipment failures.
Cisco Unified CallManager PG and CTI Manager Service
When the active CTI Manager Service or PG software fails, the PG JTAPI Gateway/PIM detects an
OUT_OF_SERVICE event and induces a failover to the redundant (duplex) PG. Because the redundant
PG is logged into the backup Cisco Unified CallManager subscriber CTI Manager Service already, it
registers the IP phones and configured dialed numbers or CTI route points automatically. This
initialization service takes place at a rate of about 5 devices per second. The agent desktops show them
as being logged out or not ready, and a message displays stating that their routing client or peripheral
(Cisco Unified CallManager) has gone off-line. (This warning can be turned on or off, depending on the
administrator's preference.) All agents lose their desktop third-party call control functionality until the
failure recovery is complete. The agents can recognize this event because call control action buttons on
the desktop will gray out, and they will not be able to do anything with the desktop. Any existing calls
should remain active without any impact to the caller.
Note Agents should not push any buttons during desktop failover because these keystrokes can be buffered
and sent to the CTI server when it completes its failover and restores the agent states.
Once the CTI Manager service or PG completes its failover, the agents return to their previous state. At
this point, the agents should also be able to release, transfer, or conference calls.
Unified ICM Voice Response Unit PG
When a Voice Response Unit (VRU) PG fails, all the calls currently in queue or treatment on that
Unified IP IVR (CRS) are dropped. Calls queued in the Unified CVP are not dropped and will be
redirected to a secondary CVP or number in the H.323 dial plan, if available. The redundant (duplex)
VRU PG side will connect to the Unified IP IVR (CRS) or CVP and begin processing calls upon failover.
Upon recovery of the failed VRU PG side, the currently running VRU PG continues to operate as the
active VRU PG. Therefore, having redundant VRU PGs adds significant value because it allows an
IP IVR or CVP to continue to function as an active queue point or to provide call treatment. Without
VRU PG redundancy, a VRU PG failure would block use of that IP IVR even though the IP IVR is
working properly. (See Figure 3-21.)
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