Cisco Unified Contact Center Enterprise Design Guide, Release 10.0(1)
Sizing Unified CCE Components and Servers
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Sizing Unified CCE Components and Servers

Sizing Unified CCE Components and Servers

Sizing Considerations for Unified CCE

Proper sizing of your Cisco Unified Contact Center Enterprise (Unified CCE) solution is important for optimum system performance and scalability. Sizing considerations include the number of agents the solution can support, the maximum busy hour call attempts (BHCA), and other variables that affect the number, type, and configuration of application servers required to support the deployment. Regardless of the deployment model chosen, Unified CCE is based on a highly distributed architecture, and questions about capacity, performance, and scalability apply to each element within the solution as well as to the overall solution.

This chapter presents design practices focusing on scalability and capacity for Unified CCE deployments. The design considerations and capacities presented in this chapter are derived primarily from testing and, in other cases, extrapolated test data. This information is intended to enable you to size and provision Unified CCE solutions appropriately.

This chapter refers to sizing tools that are available online. The sizing tools are available to Cisco internal employees and Cisco partners only, and proper login authentication is required.

Core Unified CCE Components

When sizing Unified CCE deployments, Cisco Unified Communications components are a critical factor in capacity planning. Good design, including multiple Cisco Unified Communications Managers and clusters, must be utilized to support significant call loads. For additional information about Cisco Unified Communications Manager capacity and sizing of Cisco Unified Communications components, see the latest version of the Cisco Collaboration System Solution Reference Network Designs at http:/​/​​go/​ucsrnd.

Additionally, because of varying agent and skill group capacities, consider proper sizing of the Agent PG, including Finesse and CTI OS Desktop servers, together with the Cisco Unified Communications components.

Finally, the remaining Unified CCE components, while able to scale extremely well, are affected by specific configuration element sizing variables that also have an impact on the system resources. These factors, discussed in this section, must be considered and included in the planning of any deployment.


Unless otherwise explicitly noted, the capacity information presented in Operating Conditions specifies capacity for inbound calls only and does not apply equally to all implementations of Unified CCE. The data is based on testing in particular scenarios, and it represents the maximum allowed configuration. This data, along with the sizing variables information in this chapter, serves only as a guide. As always, be conservative when sizing and plan for growth.


Sizing considerations are based on capacity and scalability test data. Major Unified CCE software processes were run on individual VMs to measure their specific CPU and memory usage and other internal system resources. Reasonable extrapolations were used to derive capacities for co-resident software processes and multiple vCPU VMs. This information is meant as a guide for determining when Unified CCE software processes can be co-resident within a single VM and when certain processes need their own dedicated VM. Table 1 assumes that the deployment scenario includes two fully redundant VMs.

Related Concepts

Operating Conditions

The sizing information presented in this chapter is based on the following operating conditions:
  • Maximum of 30 busy hour call attempts (BHCA) per agent.
  • Five skill groups or precision queues per agent.
  • The total number of agents indicated in the following tables and figures consists of 90% agents and 10% supervisors. For example, if a table or figure indicates 100 agents, the assumption is that there are 90 agents and 10 supervisors.
  • Supervisors do not handle calls.
  • Total number of teams is equal to 10% of total number of agents.
  • Team members consist of 90% agents and 10% supervisors.
  • Call types consist of 85% straight calls, 10% consultative transfers, and 5% consultative conferences.
  • The default refresh rate for skill group updates is 10 seconds.
  • The default number of skill group statistics columns configured at the CTI OS server is 17 columns.
  • Agent Statistics is turned ON.
  • The default number of agent statistics columns configured at the CTI OS server is 6 columns.
  • Average of five Voice Response Unit (VRU) scripts, running consecutively in the Unified CCE script, per VRU call.
  • Five Expanded Call Context (ECC) scalars.
  • Transport Layer Security (TLS) for CTI OS is turned OFF.
  • No mobile agents.
  • Outbound hit rate is averaged at 30%.

The following notes apply to all figures and tables in this topic:

  • The number of agents indicates the number of logged-in agents
  • Server types:
    • APG = Agent Peripheral Gateway
    • PGR = Lab deployment
    • RGR = Rogger
Figure 1. Minimum Servers Required for Unified CCE Deployments with CTI OS Desktop

The following notes apply to the figure above:
  • Sizing is based on the information listed above.
  • Voice Response Unit (VRU), Administration & Data Server, and Unified Communications Manager components are not shown.


The terms Rogger and Central Controller are used interchangeably throughout this chapter.

Table 1 Sizing Information for Unified CCE Components and Servers
Component Notes
Administration & Data Server For the current specifications for a VM running the Administration & Data Server, see the Virtualization for Unified CCE DocWiki at http:/​/​​wiki/​Virtualization_​for_​Unified_​CCE.
Voice Response Unit (VRU) PG Use the number of ports instead of agent count. Average of 5 Run VRU Script Nodes per call.
Agent PG with Outbound Voice (Includes Dialer and Media Routing PG)

To determine the maximum inbound agent capacity, see the Inbound Agent PG entry in this table. The capacity depends on your Unified CCE software release, hardware server class, and agent desktop type.

Impact of Outbound Option on agent capacity:

  • For SIP Dialers: (Maximum PG agent capacity) – (1.33 x [number of SIP Dialer ports])

  • For SCCP Dialers: (Maximum PG agent capacity) – (4 x [number of SCCP dialer ports])

The formula is an indicator of platform capacity. The formula does not indicate outbound resources in terms of how many agents can be kept busy by the number of dialer ports in the deployment. A quick but inexact estimate is that two ports are required for each outbound agent, but your outbound resources can vary depending on hit rate, abandon limit, and talk time for the campaigns in the deployment. Use the sizing tool to determine outbound resources required for your campaigns.

Example: Agent PG with Cisco Finesse and 30 SIP Dialer ports.

Available inbound Finesse agents = 2000 - (1.33*30) = 1960.


The Cisco Media Blender is not supported when installed on a PG system.

Cisco Unified Web and E-Mail Interaction Manager For the most current server specifications and sizing guidelines for Cisco Unified Web and E-Mail Interaction Manager, see the latest documentation at http:/​/​​c/​en/​us/​support/​customer-collaboration/​unified-email-interaction-manager/​products-implementation-design-guides-list.html.
Cisco Unified Customer Voice Portal (CVP) Application Server And Voice Browser For the most current server specifications for Unified CVP, see the latest version of the Hardware and System Software Specification for Cisco Unified CVP at http:/​/​​c/​en/​us/​support/​customer-collaboration/​unified-customer-voice-portal/​products-technical-reference-list.html.
Unified IP IVR Server For the most current Unified IP IVR server specifications, see the documentation available through valid Cisco Employee or Partner login.
Cisco Unified Intelligence Center (Unified Intelligence Center) For the most current server specifications for Unified Intelligence Center, see the latest version of the Hardware and System Software Specification (Bill of Materials) at http:/​/​​c/​en/​us/​support/​customer-collaboration/​unified-intelligence-center/​products-implementation-design-guides-list.html.

For further details on sizing VMs, see the Unified Communications in a Virtualized Environment DocWiki pages.

Additional Sizing Factors

Many variables in the Unified CCE configuration and deployment options can affect the hardware requirements and capacities. This section describes the major sizing variables and how they affect the capacity of the various Unified CCE components.

Busy Hour Call Attempts (BHCA)

The number of calls attempted during a busy hour is an important metric. As BHCA increases, there is an increase in the load on all Unified CCE components, most notably on Unified CM, Unified IP IVR, and the Unified CM PG. The capacity numbers for agents assume up to 30 calls per hour per agent. If a deployment requires more than 30 calls per hour per agent, it decreases the maximum number of supported agents for the agent PG. Handle such occurrences on a case-by-case basis.


The number of agents is another important metric that impacts the performance of most Unified CCE server components, including Unified CM clusters.

Average Skill Groups or Precision Queues Per Agent

The number of skill groups or precision queues per agent (which is independent of the total number of skills per system) significantly affects the following:

  • CTI OS servers

  • Finesse servers

  • Agent PG

  • Call Router

  • Logger

Limit the number of skill groups and precision queues per agent to 5 or fewer, when possible. Periodically remove unused skill groups or precision queues so that they do not affect the system's performance. You can also manage the effects on the CTI OS Server by increasing the value for the frequency of statistical updates.

The Finesse server does not display statistics for unused skill groups. Therefore, the number of skill groups that are assigned to agents affects the performance of the Finesse server more than the total number of skill groups configured. The Finesse server supports a maximum of 1961 skill groups assigned to agents, not including the default skill group.

Queue (skill group) statistics are updated on the Finesse Desktop at 10-second intervals. The Finesse Desktop also supports a fixed number of queue statistics fields. These fields cannot be changed.

The first table shows examples of the number of skill groups or precision queues (PQ) per agent affecting the capacity of the Unified CCE system. The table shows the capacity for each CTI OS instance. The Finesse server supports the same number of agents and skill groups as CTI OS.

Unified CCE supports a maximum of 50 unique skill groups across all agents on a supervisor’s team, including the supervisor’s own skill groups. If this number is exceeded, all skill groups monitored by the supervisor still appear on the supervisor desktop. However, exceeding this number can cause performance issues and is not supported.


Each precision queue that you configure creates a skill group per Agent PG and counts toward the supported number of skill groups per PG.

The numbers in this table are subject to specific hardware and software requirements.

Table 2 Sizing Effects of Skill Groups or Precision Queues for Each Agent (12,000 Agents)
Avg Configured PQ or SG for each Agent System Generic PG Limits
Max Concurrent Agent for each System Max Concurrent Agent for each PG Max Configured PQ or SG for each PG Max Configured VRU Ports for each PG Max Configured VRU PIMs for each PG
5 12000 2000 3000 1000 4
10 11038 1832 3000 1000 4
15 10078 1663 3000 1000 4
20 9116 1495 3000 1000 4
25 8156 1326 3000 1000 4
30 7194 1158 3000 1000 4
35 6234 989 3000 1000 4
40 5272 820 3000 1000 4
45 4312 652 3000 1000 4
50 3350 484 3000 1000 4


CTI OS monitor mode applications are supported only at 20 or lower skill groups per agent.

Supervisors and Teams

The number of supervisors and team members can also be a factor impacting the CTI OS Server performance. Distribute your agents and supervisors across multiple teams and have each supervisor monitor only a few agents.


Supervisors can monitor only agents within their own team, and all of the agents must be configured on the same peripheral.


You can add a maximum of 50 agents per team. You can add a maximum of ten supervisors per team.

A Unified CCE system can support a maximum of 50 agents per supervisor with the assumptions below. If a particular environment requires more than 50 agents per supervisor, then use the following formula to ensure that there is no impact to the CTI OS Server and Supervisor desktop. The most important factor in this calculation is the number of updates per second.

X = (Y * (N + 1) / R) + ((Z * N * A) / 3600), rounded up to the next integer


X = Number of updates per second received by the CTI OS Supervisor desktop.

Y = Weighted Average of Number of Skill Groups or Precision Queues per Agents. For example, if total of 10 agents have the following skill group distribution: 9 have 1 skill group and 1 agent has 12 Skill Groups. The number of skills per agent ('Y') is, Y = 90% * 1 + 10% * 12 = 2.1.
       (The number of configured statistics in the CTI OS server is 17.)

Z = Calls per hour per agent.

A = Number of agent states. (Varies based on call flow; average = 10.)

N = Number of agents per supervisor.

R = The skill group or precision queue refresh rate configured on the CTI OS Server. (Default = 10 seconds.)

(Y * (N + 1) / R) = Number of updates per second, based on skill groups.

(Z * N * A) / 3600 = Number of updates per second, based on calls.

The CTI OS Supervisor desktop is not impacted as long as there are fewer than 31 updates per second. This threshold value is derived by using the above formula to calculate the update rate for 50 agents per supervisor (N = 50), as follows:

X = (5 * (50 + 1) / 10) + ((30 * 50 * 10) / 3600) = 25.5 + 5 = 31 updates per second

The maximum number of agents per supervisor must not exceed 200 for any given configuration, still holding updates per sec to a max of 31 with above formula.

CTI OS Monitor Mode Applications

A CTI OS Monitor Mode application can affect the performance of the CTI OS Server. CTI OS supports only two such applications per server pair. Depending on the filter specified, the impact on the CPU utilization might degrade the performance of the Agent PG.

Unified CM Silent Monitor

Each silently monitored call adds more processing for the PG and Unified CM. Each silently monitored call is equivalent to two unmonitored calls to an agent. Make sure that the percentage of the monitored calls is within the capabilities of PG scalability.

CTI OS Skill Group Statistics Refresh Rate

The skill group statistics refresh rate can also affect the performance of CTI OS Server. Cisco requires that you do not lower the refresh rate below the default value of 10 seconds.

Call Types

The call type is also an important metric that affects the performance of most Unified CCE server components. An increase in the number of transfers and conferences increase the load on the system and, thus, decrease the total capacity.


The Unified IP IVR and Unified Customer Voice Portal (CVP) place calls in a queue and play announcements until an agent answers the call. For sizing purposes, it is important to know whether:

  • The VRU will handle all calls initially (call treatment), and direct the callers to agents after a short queuing period.

  • The agents will handle calls immediately, and the VRU queues only unanswered calls when all agents are busy.

The answer to this question determines VRU sizing requirements and affects the performance of the Call and Voice Response Unit (VRU) PG.
Sizing the translation route pool depends on the expected call arrival rate. Use the following formula to size the translation route pool:

Translation route pool = 20 * (Calls per second)

This calculation is specific to Unified CCE. For more general Unified ICM deployments, consult your Cisco Account Team or Partner.

Unified CCE Script Complexity

As the complexity and/or number of Unified CCE scripts increase, the processor and memory overhead on the Call Router and VRU PG increases significantly. The delay time between replaying Run VRU scripts also has an impact.


Real-time reporting can have a significant effect on Logger and Rogger processing due to database access. A separate VM is required for an Administration & Data Server to off-load reporting overhead from the Logger and Rogger.

VRU Script Complexity

As VRU script complexity increases with features such as database queries, the load placed on the IP IVR Server and the Router also increases. There is no good rule or benchmark to characterize the Unified IP IVR performance when used for complex scripting, complex database queries, or transaction-based usage. Test complex VRU configurations in a lab or pilot deployment to determine the response time of database queries under various BHCA and how they affect the processor and memory for the VRU server, PG, and Router.

Unified IP IVR Self-Service Applications

In deployments where the Unified IP IVR is also used for self-service applications, the self-service applications are in addition to the Unified CCE load. Factor self-service applications into the sizing requirements as stated in the sizing tables above.

Third-Party Database and Cisco Resource Manager Connectivity

Carefully examine connectivity of any Unified CCE solution component to an external device and/or software to determine the overall effect on the solution. Cisco Unified CCE solutions are flexible and customizable, but they can also be complex. Contact centers are often mission-critical, revenue-generating, and customer-facing operations. Therefore, engage a Cisco Partner (or Cisco Advanced Services) with the appropriate experience and certifications to help you design your Unified CCE solution.

Expanded Call Context (ECC)

The ECC usage impacts PG, Router, Logger, and network bandwidth. There are many ways that ECC can be configured and used. The capacity impact varies based on ECC configuration, handled on a case-by-case basis.

Related Concepts

Peripheral Gateway and Server Options

A Unified CCE Peripheral Gateway (PG) translates messages coming from the Unified Communications Manager servers, the Unified IP IVR, Unified CVP, or voice response units (VRUs) into common internally formatted messages that are then sent to and understood by Unified CCE. In the reverse, it also translates Unified CCE messages so that they can be sent to and understood by the peripheral devices.

The figures below illustrate various configuration options for the Agent PG with CTI OS.

Figure 2. Agent PG Configuration Options with CTI OS

The table below gives sizing guidelines for PGs and PIMs.

Table 3 PG and PIM Sizing Guidelines

Sizing variable

Guidelines based on Unified CCE Release 10

Maximum number of PGs per Unified CCE


Maximum number of PG types per VM

Up to two PG types are permitted per VM, but each VM must meet the maximum agent and VRU port limitations.

Maximum number of Unified Communications Manager PGs per VM

Only one Unified Communications Manager PG, Generic PG, or System PG is allowed per VM.

Maximum number of Unified Communications Manager PIMs per PG


Can PGs be remote from Unified CCE?


Can PGs be remote from Unified Communications Manager?


Maximum number of VRUs controlled by one Unified Communications Manager

See the Cisco Collaboration System Solution Reference Network Designs at http:/​/​​go/​ucsrnd.

Maximum number of CTI servers per PG


Can PG be co-resident with Cisco Unified Communications Manager?


Agent Greeting Sizing Considerations

Agent Greeting invokes conference resources to bring the greeting into the call. With supported hard phones, the Built in Bridge on the phone is used. For Mobile Agent, conference resources are used. This adds a short but additional call leg to every call, which has impacts on all components.

Central Controller

Agent Greeting has an impact of up to 1.5 regular calls on the Router and Logger. This implies that the maximum call rate on Unified CCE is reduced from 60 calls per second to 40 calls per second, as measured by new calls that originate from the service provider. As each Agent Greeting involves an additional route request, the Router PerfMon counter displays 80 calls per second under a full supported load. The number of agents supported per System is dependent upon the overall call rate. For a specific scenario, see the Unified CCE Sizing Tool.

Peripheral Gateway

Agent Greeting does have an impact on the PG resource utilization, but it is not enough impact to require reducing the supported agent capacity per PG. Other factors like additional skill groups per agent or total configured skill groups also play a factor in PG sizing. When sizing the PG, the sizing calculator factors in Agent Greeting.

Communications Manager

When Agent Greeting and/or Mobile Agent and Unified IP IVR are in use, the number of agents supported by a Unified Communications Manager subscriber is impacted.

The Cisco Unified Collaboration Sizing Tool takes call rate and the other factors into account to determine the capacity for a specific scenario.

Mobile Agent

Agent Greeting with Mobile Agent uses additional Conference Bridge and MTP resources. The agent greeting calls are relatively short and they need not be factored into sizing considerations. To properly size Conference Bridge and UCM resources, indicate a conference in place of an Agent Greeting for each Mobile Agent (when Agent Greeting is enabled) for each inbound call.

CVP and VXML Gateway

Agent Greeting also utilizes CVP and VXML gateway resources, so it is important to consider the call rate when sizing. The Design Guide for Cisco Unified Customer Voice Portal includes information about how to size based on call rate; however, most deployments are sized based on the number of ports. The Agent Greeting utilization has a profile of short calls but at a high call rate, so do not overlook this consideration.

Whisper Announcement Sizing Considerations

The impact of Whisper Announcement on solution component sizing is not as significant as the impact caused by Agent Greeting. To factor in Whisper Announcement, run the Cisco Unified Collaboration Sizing Tool.

Peripheral Throttling

To mitigate possible overload conditions on the agent peripheral, Precision Routing limits the number of calls to the peripheral when it detects an overload condition. When this occurs, the system stops routing Precision Routing calls to that peripheral for a short period of time.

System Performance Monitoring

Supporting and maintaining an enterprise solution requires many steps and procedures. Depending on the customer environment, the support procedures vary. System performance monitoring is one procedure that helps maintain the system. This section provides a guide for monitoring Unified CCE to ensure that the system is performing within system tolerances. System monitoring is especially critical for customers as they expand or upgrade their system. Monitor the system during times of heavy activity. For more information about monitoring, see the Serviceability Best Practices Guide for Cisco Unified ICM/Contact Center Enterprise at http:/​/​​c/​en/​us/​support/​customer-collaboration/​unified-contact-center-enterprise/​products-configuration-examples-list.html.

The following system components are critical to monitor:
  • CPU
  • Memory
  • Disk
  • Network
The following list highlights some of the important counters for the critical system components, along with their threshold values:
  • Monitoring the CPU
    • %Processor Time; the threshold of this counter is 60%.
    • ProcessorQueueLength; this value must not go above (2 * [the total number of CPUs on the system]).
  • Monitoring Memory
    • % Committed Bytes; this value must remain less than (0.8 * [the total amount of physical memory]).
    • Memory\Available MByte; this value must not be less than 16 MB.
    • Page File %usage; the threshold for this counter is 80%.
  • Monitoring the Disk Resources
    • AverageDiskQueueLength; this value must remain less than (1.5 * [the total number of disks in the array]).
    • %Disktime; this value must remain less than 60%.
  • Monitoring Network Resources
    • NIC\bytes total/sec; this value must remain less than (0.3 * [the bandwidth of the NIC]).
    • NIC\Output Queue Length; the threshold for this counter is 1.
  • Monitoring Unified CCE application
    • Cisco Call Router(_Total)\Agents Logged On
    • Cisco Call Router(_Total)\Calls in Progress
    • Cisco Call Router(_Total)\calls /sec


The above performance counters for CPU, memory, disk, and network are applicable to all VMs within the deployment. The preferred sample rate is 15 seconds.


Proper sizing of Unified CCE components requires analysis beyond the number of agents and busy hour call attempts. Configurations with multiple skill groups per agent, significant call queuing, and other factors contribute to the total capacity of any individual component. Careful planning and discovery in the pre-sales process uncovers critical sizing variables; apply these considerations to the final design and hardware selection.

Correct sizing and design can ensure stable deployments for large systems up to 8000 agents and 216,000 BHCA. For smaller deployments, cost savings can be achieved with careful planning and co-resident Unified CCE components (for example, Rogger and Agent PG).

Pay careful attention to the sizing variables that impact sizing capacities such as skill groups per agent. While it is often difficult to determine these variables in the pre-sales phase, it is critical to consider them during the initial design, especially when deploying co-resident PGs.