Cisco Cisco Unified Contact Center Enterprise 9.0(2) Guía De Diseño

Determine the protocols to be used.

Determine redundancy requirements.

Determine all other customer requirements for Cisco Unified Communications that will share a 
Unified CM cluster with a Unified CCE deployment (such as Cisco Unified IP Phones, applications 
that are not part of Unified CCE, route patterns, and so forth).

Once you have completed these tasks, you can begin to accurately size the necessary Unified CM 
cluster(s). Many factors impact the sizing of a Unified CM cluster, and the following list mentions some 
of those factors:

Number of office phones and the busy hour call attempt (BHCA) rate per phone

Number of inbound agent phones and the BHCA rate per phone

Number of CTI ports and the BHCA rate on those VoIP endpoints (can be zero if CVP is used for 
call treatment, self service, and queueing)

Number of voice gateway ports and the BHCA rate on those VoIP endpoints

Number of outbound agent phones, outbound dialing mode, and BHCA rate per phone

The number of outbound dialer ports, number of IVR ports for outbound campaigns, and the BHCA 
rate per port for both

The number of mobile agents and the BHCA rate per mobile agent

Number of voicemail ports and the BHCA rate to those VoIP endpoints

Signaling protocol(s) used by the VoIP endpoints

Percent of agent call transfers and conferences

Dial plan size and complexity, including the number of dialed numbers, lines, partitions, calling 
search spaces, locations, regions, route patterns, translations, route groups, hunt groups, pickup 
groups, route lists, and so forth

Amount of media resources needed for functions such as transcoding, conferences, encryption, and 
so forth

Co-resident applications and services such Auto Attendant, CTI Manager, E-911, and Music On 
Hold

Unified CM release (sizing will vary per release)

Desired hardware server model (sizing will vary per hardware server model)

Other factors can affect cluster sizing, but the above list shows the most significant factors in terms of 
resource consumption.

The general process to sizing a Unified CM cluster is to estimate the resource consumption (CPU, 
memory, and I/O) for each of these factors and then to choose hardware that will satisfy the resource 
requirements.

It is important to gather information with regards to the factors listed above before attempting to size a 
cluster with any accuracy. To assist in calculating these numbers that relate to Unified CCE, Cisco 
recommends using the Unified CCE Resource Calculators, discussed in the chapter on 

In prior releases of the Unified CM software, Cisco utilized various schemes to calculate the capacity of 
a cluster using device weights, BHCA multipliers, and dial-plan weights. With Unified CM Releases 4.x, 
5.x, and later, these approaches have been replaced by the Cisco Unified CM Capacity Tool and the 
Unified Communications Sizing Tool to allow for more accurate planning of the system. The next section 
describes these tools.