The figure below illustrates the principal steps and design considerations for sizing a call center.
Figure 1. Unified CCX Design Process – Call Center Sizing
This figure is a general overview of the design considerations for call sizing. For a detailed description of the call center sizing design process, refer to the section on sizing call center resources in the Cisco Unified Contact Center Enterprise Solution Reference Network Design Guide, available online at the following URL:
There are similar basic call center sizing considerations and steps for Unified CCE, and they also can be used in sizing a smaller contact center for Unified CCX. This call-sizing approach will provide you with the minimum number of IVR ports to support the total BHCA.
In addition, you should include the following design considerations, specific to Unified CCX, in your call center sizing calculations:
At a minimum, plan on enough capacity to replace your existing system. The replacement system should perform at least as well as the one it is replacing.
After all of the Erlang (C and B) calculations are complete for the call center sizing, any changes in queue times or agents will affect the total number of trunks and IVR ports required for an Unified CCX solution.
As you increase the size of the agent pool, very small changes in the average queue time and percentage of queued calls will affect the required number of gateway trunks and IVR ports.
Even if you perform all of the calculations for a call center, there are still some variables that you cannot plan for but that will affect the ports needed on a Unified CCX system. For example, one or more agents could call in sick, and that would affect the port count and queue time for each call. Just two agents calling in sick could increase the port count by over 12%. This would affect the price of the system and, if not planned for, would affect the ability of the call center to meet caller requirements. Properly sizing call center resources is integral to designing an effective Unified CCX system.
Not all of the Unified CCX system limits are available at the same time.
If all of the call sizing information is available, the next step is to apply Unified CCX sizing limits to the call center requirements. For this step, use the Cisco Unified Communications Sizing Tool, available online at:
The Unified Communications downloadable sizing tools help you with the task of sizing Unified Communications deployments.