Cisco Cisco IP Contact Center Release 4.6.1 プリント

(no trunks available) out of the total BHCA. For example, a grade of service of 0.01 means that 1% of 
calls in the busy hour would be blocked. A 1% blockage is a typical value to use for PSTN trunks, but 
different applications might require different grades of service.

A blocked call is a call that is not serviced immediately. Callers are considered blocked if they are 
rerouted to another route or trunk group, if they are delayed and put in a queue, or if they hear a tone 
(such as a busy tone) or announcement. The nature of the blocked call determines the model used for 
sizing the particular resources.

This term is a standard in the contact center industry, and it refers to the percentage of the offered call 
volume (received from the voice gateway and other sources) that will be answered within x seconds, 
where x is a variable. A typical value for a sales call center is 90% of all calls answered in less than 
10 seconds (some calls will be delayed in a queue). A support-oriented call center might have a different 
service level goal, such as 80% of all calls answered within 30 seconds in the busy hour. Your contact 
center’s service level goal determines the number of agents needed, the percentage of calls that will be 
queued, the average time calls will spend in queue, and the number of PSTN trunks and Unified IP IVR 
ports needed. For an additional definition of service level within Unified CCE products, refer to the 
Unified CCE glossary available online at 

When agents are busy with other callers or are unavailable (after call wrap-up mode), subsequent callers 
must be placed in a queue until an agent becomes available. The percentage of calls queued and the 
average time spent in the queue are determined by the service level desired and by agent staffing. Cisco's 
Unified CCE solution uses a Unified IP IVR to place callers in queue and play announcements. It can 
also be used to handle all calls initially (call treatment, prompt and collect – such as DTMF input or 
account numbers – or any other information gathering) and for self-service applications where the caller 
is serviced without needing to talk to an agent (such as obtaining a bank account balance, airline 
arrival/departure times, and so forth). Each of these scenarios requires a different number of 
Unified IP IVR ports to handle the different applications because each will have a different average 
handle time and possibly a different call load. The number of trunks or gateway ports needed for each 
of these applications will also differ accordingly. (See the section on 

, for examples on how to calculate the 

number of trunks and gateway ports needed.) 

The focus of this chapter is on sizing the following main resources in a call center:

Agents

Gateway ports (PSTN trunks)

Unified IP IVR ports.

It is helpful first to understand the anatomy of an inbound call center call as it relates to the various 
resources used and the holding time for each resource. 

 shows the main resources used and the 

occupancy (hold/handle time) for each of these resources.