Cisco Unified Contact Center Enterprise Solution Reference ...

Chapter 2 Deployment Models
Treatment and Queuing
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IPT: Multi-Site with Distributed Call Processing
The Unified ICM Central Controller provides the capability to create a single enterprise-wide queue.
The Unified ICM Central Controller provides consolidated reporting for all sites.
Best Practices
The PG, Cisco Unified CallManager cluster, and Unified IP IVR must be co-located at the contact
center site.
The communication link from the Unified ICM Central Controller to the PG must be sized properly
and provisioned for bandwidth and QoS. (For details, refer to the chapter on Bandwidth
Provisioning and QoS Considerations, page 11-1.)
Gatekeeper-based call admission control could be used to reroute calls between sites over the PSTN
when WAN bandwidth is not available. It is best to ensure that adequate WAN bandwidth exists
between sites for the maximum amount of calling that can occur.
If the communication link between the PG and the Unified ICM Central Controller is lost, then all
contact center routing for calls at that site is also lost. Therefore, it is important to implement a
fault-tolerant WAN. Even when a fault-tolerant WAN is implemented, it is important to identify
contingency plans for call treatment and routing when communication is lost between the Unified
ICM Central Controller and PG. For example, in the event of a lost Unified ICM Central Controller
connection, the Cisco Unified CallManager CTI route points could send the calls to Unified IP IVR
ports to provide basic announcement treatment or to invoke a PSTN transfer to another site. Another
alternative is for the Cisco Unified CallManager cluster to route the call to another Cisco Unified
CallManager cluster that has a PG with an active connection to the Unified ICM Central Controller.
For more information on these options, refer to the chapter on Design Considerations for High
Availability, page 3-1.
While two intercluster call legs for the same call will not cause unnecessary RTP streams, two
separate call signaling control paths will remain intact between the two clusters (producing logical
hairpinning and reducing the number of intercluster trunks by two).
Latency between Unified ICM Central Controllers and remote PGs cannot exceed 200 ms one way
(400 ms round-trip).
Initial call queuing is done on a Unified IP IVR co-located with the voice gateways, so no transcoding
is required. When a call is transferred and subsequent queuing is required, the queuing should be done
on a Unified IP IVR at the site where the call is currently being processed. For example, if a call comes
into Site 1 and gets routed to an agent at Site 2, but that agent needs to transfer the call to another agent
whose location is unknown, the call should be queued to a Unified IP IVR at Site 2 to avoid generating
another intercluster call. A second intercluster call would be made only if an agent at Site 1 was selected
for the transfer. The RTP flow at this point would be directly from the voice gateway at Site 1 to the
agent’s phone at Site 1. However, the two Cisco Unified CallManager clusters would still logically see
two calls in progress between the two clusters.
Cisco Unified Contact Center Enterprise 7.x SRND
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