Cisco Cisco Unified Contact Center Enterprise 9.0(1) Design Guide

At this time, no tool exists that specifically addresses communication between the Unified IP IVR or 
Unified CVP PG and the Unified IP IVR or Unified CVP. However, the tool mentioned in the previous 
section produces a fairly accurate measurement of bandwidth needed for this communication. 
Bandwidth consumed between the Unified ICM Central Controller and Unified IP IVR or Unified CVP 
PG is very similar to the bandwidth consumed between the Unified IP IVR or Unified CVP PG and the 
Unified IP IVR or Unified CVP.

The VRU Peripheral Gateway to ICM Central Controller Bandwidth Calculator tool is available (with 
proper login authentication) through the Cisco Steps to Success Portal at 

If the Unified IP IVR or Unified CVP PGs are split across the WAN, total bandwidth required would be 
double what the tool reports: once for Unified ICM Central Controller to Unified IP IVR or Unified CVP 
PG and once for Unified IP IVR or Unified CVP PG to Unified IP IVR or Unified CVP.

The worst case for bandwidth utilization across the WAN link between the CTI OS and CTI Server 
occurs when the CTI OS is remote from the CTI Server. A bandwidth queue should be used to guarantee 
availability for this worst case. 

For this model, the following simple formula can be used to compute worst-case bandwidth 
requirements:

With no Extended Call Context (ECC) or Call Variables:

BHCA 

 20 = bps

With ECC and/or Call Variables

BHCA 

 (20 + ((Number of Variables  Average Variable Length) / 40) = bps

Example: With 10,000 BHCA and 20 ECC variables with average length of 40 bits:

10,000 

 (20 + ((20  40) / 40) = 10,000  40 = 400,000 bps = 400 kbps

The bandwidth required for Intra-Cluster Communication Signaling (ICCS) between Unified CM 
subscriber nodes is significantly higher when Unified CCE is deployed, due to the number of call 
redirects and additional CTI/JTAPI communications encompassed in the intra-cluster communications. 
The following formulae may be used to calculate the required bandwidth for the ICCS and database 
traffic between Unified CM subscriber nodes when they are deployed with Unified CCE.

Unified CM releases prior to 6.1

Intra-Cluster Communications Signaling (ICCS)

BHCA 

 200 = bps

This is the bandwidth required between each Unified CM subscriber that is connected to voice 
gateways, agent phones, and Agent PGs.

Database and other communications

644 kbps for each subscriber remote from the publisher.