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
Figure 3-5 CTI Manager Device Request to a Remote Cisco Unified CallManager
ICM
PG
Subscriber
(CTI Manager
and
Cisco
CallManager)
Request: IPCC
agent ext. 101
Device not on local
Cisco CallManager
Publisher
(CTI Manager
and
CallManager)
Forward request
Subscriber
(CTI Manager
and
Cisco
CallManager)
Device
found
IP IP
IP phone ext. 100
IP phone ext. 101
Although it might be tempting to register all of the Unified CCE devices to a single subscriber in the
cluster and point the Peripheral Gateway (PG) to that server, this configuration would put a high load on
that subscriber. If the PG were to fail in this case, the duplex PG would connect to a different subscriber,
and all the CTI Manager messaging would have to be routed across the cluster to the original subscriber.
It is important to distribute devices and CTI applications appropriately across all the call processing
nodes in the Cisco Unified CallManager cluster to balance the CTI traffic and possible failover
conditions.
The external CTI applications use a JTAPI user account on the CTI Manager to establish a connection
and assume control of the Cisco Unified CallManager devices registered to this JTAPI user. In addition,
given that the CTI Managers are independent from each other, any CTI application can connect to any
CTI Manager to perform its requests. However, because the CTI Managers are independent, one CTI
Manager cannot pass the CTI application to another CTI Manager upon failure. If the first CTI Manager
fails, the external CTI application must implement the failover mechanism to connect to another CTI
Manager in the cluster.
For example, the Agent PG handles failover for the CTI Manager by using its duplex servers, sides A
and B, each of which is pointed to a different subscriber in the cluster, but not at the same time. The PG
processes are designed to prevent both sides from trying to be active at the same time. Additionally, both
of the duplex PG servers use the same JTAPI user to log into the CTI Manager applications. However,
only one Cisco Unified CallManager PG side allows the JTAPI user to register and monitor the user
devices to conserve system resources in the Cisco Unified CallManager cluster. The other side of the
Cisco Unified CallManager PG stays in hot-standby mode, waiting to be activated immediately upon
failure of the active side.
Figure 3-6 shows two external CTI applications using the CTI Manager, the Agent PG, and the
Unified IP IVR (CRS). The Cisco Unified CallManager PG logs into the CTI Manager using the JTAPI
account User 1, while the Unified IP IVR (CRS) uses account User 2. Each external application uses its
own specific JTAPI user account and will have different devices registered and monitored by that user.
For example, the Cisco Unified CallManager PG (User 1) will monitor all four agent phones and the
inbound CTI Route Points, while the Unified IP IVR (User 2) will monitor its CTI Ports and the CTI
Route Points used for its JTAPI Triggers. Although multiple applications could monitor the same
devices, this method is not recommended because it can cause race conditions between the applications
trying to take control of the same physical device.
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