Cisco Unified Contact Center Enterprise Solution Reference ...

Chapter 3 Design Considerations for High Availability
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Cisco Unified CallManager and CTI Manager Design Considerations
PSTN from routing new calls to the failed voice gateway. When the failed voice gateway comes back
on-line and the circuits are back in operation, the PSTN automatically starts delivering calls to that voice
gateway again.
With H.323 voice gateways, it is possible for the voice gateway itself to be operational but for its
communication paths to the Cisco Unified CallManager servers to be severed (for example, a failed
Ethernet connection). If this situation occurs in the case of a H.323 gateway, you can use the
busyout-monitor interface command to monitor the Ethernet interfaces on a voice gateway. To place a
voice port into a busyout monitor state, use the busyout-monitor interface voice-port configuration
command. To remove the busyout-monitor state on the voice port, use the no form of this command. As
noted previously, these gateways also provide additional processing options if the call control interface
is not available from Cisco Unified CallManager to reroute the calls to another site or dialed number or
to play a locally stored .wav file to the caller and end the call.
With MGCP-controlled voice gateways, when the voice gateway interface to Cisco Unified CallManager
fails, the gateway will look for secondary and tertiary Cisco Unified CallManager subscribers from the
redundancy group. The MGCP gateway will automatically fail-over to the other subscribers in the group
and periodically check the health of each, marking it as available once it comes back on-line. The
gateway will then fail-back to the primary subscriber when all calls are idle or after 24 hours (whichever
comes first). If no subscribers are available, the voice gateway automatically busies-out all its trunks.
This action prevents new calls from being routed to this voice gateway from the PSTN. When the voice
gateway interface to Cisco Unified CallManager homes to the backup subscriber, the trunks are
automatically idled and the PSTN should begin routing calls to this voice gateway again (assuming the
PSTN has not permanently busied-out those trunks). The design practice is to spread the gateways across
the Cisco Unified CallManager call processing servers in the cluster to limit the risk of losing all the
gateway calls in a call center if the primary subscriber that has all the gateways registered to it should
fail.
Voice gateways that are used with Cisco Unified Survivable Remote Site Telephony (SRST) option for
Cisco Unified CallManager follow a similar failover process. If the gateway is cut off from the
Cisco Unified CallManager that is controlling it, the gateway will fail-over into SRST mode, which
terminates all trunk calls and resets the gateway into SRST mode. Phones re-home to the local SRST
gateway for call control, and calls will be processed locally and directed to local phones. While running
in SRST mode, it is assumed that the agents also have no CTI connection from their desktops, so they
will be seen as not ready within the Unified CCE routing application. Therefore, no calls will be sent to
these agents by Unified CCE. When the data connection is re-established to the gateway at the site, the
Cisco Unified CallManager will take control of the gateway and phones again, allowing the agents to be
reconnected to the Unified CCE.
Cisco Unified CallManager and CTI Manager Design
Considerations
Cisco CallManager Release 3.3(x) and later uses CTI Manager, a service that acts as an application
broker and abstracts the physical binding of the application to a particular Cisco Unified CallManager
server to handle all its CTI resources. (Refer to the Cisco Unified Communications Solution Reference
Network Design (SRND) guide for further details about the architecture of the CTI Manager.) The CTI
Manager and Cisco Unified CallManager are two separate services running on a Cisco Unified
CallManager server. Some other services running on a Cisco Unified CallManager server include TFTP,
Cisco Messaging Interface, and Real-time Information Server (RIS) data collector services.
The main function of the CTI Manager is to accept messages from external CTI applications and send
them to the appropriate resource in the Cisco Unified CallManager cluster. The CTI Manager uses the
Cisco JTAPI link to communicate with the applications. It acts like a JTAPI messaging router. The JTAPI
Cisco Unified Contact Center Enterprise 7.x SRND
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