Cisco Unified Contact Center Enterprise Design Guide, Release 10.0(1)
Sizing Cisco Unified Communications Manager Servers
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Sizing Cisco Unified Communications Manager Servers

Sizing Cisco Unified Communications Manager Servers

Sizing Unified Communications Manager Clusters for Unified CCE

This chapter discusses the concepts, provisioning, and configuration of Cisco Unified Communications Manager clusters when used in a Unified CCE deployment. Clusters provide a mechanism for distributing call processing across a converged IP network infrastructure to support Cisco Unified Communications. This mechanism also facilitates redundancy and provides feature transparency and scalability.

This chapter covers only the Unified CCE operation with clusters and proposes reference designs for implementation.

The information in this chapter builds on the concepts presented in the Cisco Unified Communications SRND. Some duplication of information is necessary to clarify concepts relating to Unified CCE as an application supported by the Unified Communications Manager call processing architecture. However, the foundational concepts are not duplicated here; become familiar with them before continuing with this chapter.

This chapter documents general requirements and scalability considerations for sizing the subscribers used with your Unified CCE deployments. Within the context of this document, scalability refers to the subscriber and cluster capacity when used in a Unified CCE deployment. For information about sizing and choosing a gateway, see the gateway information in the latest version of the Cisco Unified Communications SRND.

Cluster Sizing Concepts

Before attempting to size a Unified Communications Manager cluster for a Unified CCE deployment, perform the following design tasks:
  • Determine the different types of call flows.
  • Determine the required deployment model (single site, centralized, distributed, clustering over the WAN, or remote branches within centralized or distributed deployments).
  • Determine whether Unified CVP or IP IVR is used for call treatment, self service, and queuing.
  • Determine the protocols to be used.
  • Determine redundancy requirements.
  • Determine all other customer requirements for Cisco Unified Communications that will share a 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).
After you complete these tasks, you can begin to accurately size the necessary clusters. Many factors impact the sizing of a 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 Unified CVP is used for call treatment, self service, and queuing)
  • Number of Voice Gateway ports and the BHCA rate on those VoIP endpoints
  • Type of outbound dialer (SCCP or SIP Dialer)
  • Number of outbound agent phones, outbound dialing mode, and BHCA rate per phone
  • Number of outbound dialer ports, number of VRU ports for outbound campaigns, and the BHCA rate per port for both
  • Number of mobile agents and the BHCA rate per mobile agent
  • Number of voicemail ports and the BHCA rate to those VoIP endpoints
  • Signaling protocols 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 as CTI Manager, E-911, and Music on Hold
  • Unified Communications Manager release (sizing will vary per release)
  • Type of Unified Communications Manager OVA

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 cluster is to estimate the resource consumption (CPU, memory, and I/O) for each of these factors and then to choose VMs that will satisfy the resource requirements. It is important to gather information with regard to the factors listed above before attempting to size a cluster with any accuracy.

The next section describes the tools for sizing Unified Communications Manager deployments.

Cisco Unified Collaboration Sizing Tool

To size Cisco Unified Contact Center Enterprise servers, use the Cisco Unified Collaboration Sizing Tool (Unified CST) available at http:/​/​tools.cisco.com/​cucst/​faces.

You can use the Unified CST to size large and complex Unified Communications Systems. This tool supports the sizing of many Unified Communications components, such as Unified Communications Manager, Unified CCE, Unified IP IVR, Unified CVP, and gateways.

The Unified CST is available to Cisco internal employees and Cisco partners, and proper login authentication is required. For detailed instructions, see the documentation for this tool.

Cluster Guidelines and Considerations

The following guidelines apply to all Unified Communications Manager clusters with Unified CCE.

  • All primary and fail-over (backup) subscribers must use the same OVF template. All subscribers in the cluster must run the same Unified Communications Manager software release and service pack.
  • Within a cluster, you can enable a maximum of eight subscribers with the Cisco Call Manager Service, including backup subscribers. You can use more VMs for dedicated functions such as TFTP, publisher, and music on hold.
  • In a deployment with IP IVR, each cluster (four primary and four backup subscribers) can support about 2000 Unified CCE agents. This limit assumes that the BHCA call load and all configured devices are spread equally among the eight call processing servers with 1:1 redundancy. Each of the eight subscribers would support a maximum of 250 agents. In a fail-over scenario, the primary subscriber would support a maximum of 500 agents. These capacities can vary, depending on your specific deployment. All deployments must be sized by using the Cisco Unified Communications Manager Capacity Tool or the Unified Collaboration Sizing Tool.
  • In a deployment with Unified CVP (no IP IVR), each cluster (four primary and four backup subscribers) can support about 4000 Unified CCE agents. This limit assumes that the BHCA call load and all configured devices are spread equally among the eight call processing subscribers with 1:1 redundancy. Each of the eight subscribers would support a maximum of 500 agents. In a fail-over scenario, the primary subscriber would support a maximum of 1,000 agents. These capacities can vary, depending on your specific deployment. All deployments must be sized by using the Cisco Unified Communications Manager Capacity Tool or the Unified Collaboration Sizing Tool.

When sizing the cluster to support contact center solutions for the appropriate number of CTI resources, remember to account for the following:

  • Configured phones from agents who are not signed in
  • Applications which remotely control the device like Call Recording, Attendant Console, and PC-clients
  • Other 3rd-party applications which consume CTI resources

Unified Communications Manager can support multiple concurrent CTI resources, for example, when multiple lines, the contact center, and recording are used concurrently. Those CTI resources follow the same CTI rules as described in the Unified Communications SRND. Size all deployments with the Cisco Unified Collaboration Sizing Tool.

  • Devices (including phones, music on hold, route points, gateway ports, CTI ports, JTAPI Users, and CTI Manager) must never reside or be registered on the publisher. If there are any devices registered with the publisher, any administrative work on Unified Communications Manager impacts call processing and CTI Manager activities.
  • Do not use a publisher as a fail-over or backup call processing subscriber in production deployments. Any deviations require review by Cisco Bid Assurance on a case-by-case basis.
  • Any deployment with more than 150 agent phones requires a minimum of two subscribers and a combined TFTP and publisher. The load-balancing option is not available when the publisher is a backup call processing subscriber.
  • If you require more than one primary subscriber to support your configuration, then distribute all agents equally among the subscriber nodes. This configuration assumes that the BHCA rate is uniform across all agents.
  • Similarly, distribute all gateway ports and Unified IP IVR CTI ports equally among the cluster nodes.
  • If you require more than one Unified CCE JTAPI user (CTI Manager) and more than one primary subscriber, then group and configure all devices monitored by the same Unified CCE JTAPI User (third-party application provider), such as Unified CCE route points and agent devices, on the same VM if possible.
  • Enable CTI Manager only on call processing subscribers, thus allowing for a maximum of eight CTI Managers in a cluster. To provide maximum resilience, performance, and redundancy, load-balance CTI applications across the various CTI Managers in the cluster. For more CTI Manager considerations, see the Cisco Unified Communications Solution Reference Network Design (SRND) Guide at http:/​/​www.cisco.com/​go/​ucsrnd.
  • If you have a mixed cluster with Unified CCE and general office IP phones, group and configure each type on a separate VM if possible (unless you need only one subscriber). For example, all Unified CCE agents and their associated devices and resources are on one or more Unified Communications Manager servers. Then, all general office IP phones and their associated devices (such as gateway ports) are on other Unified Communications Manager servers, as long as cluster capacity allows. If you use the Cisco Unified Communications Manager Capacity Tool, run the tool separately with the specific device configuration for each primary Unified Communications Manager server. You need to run it multiple times because the tool assumes that all devices are equally balanced in a cluster. Remember that with Unified CCE, you must use the 1:1 redundancy scheme. If you use the Unified Collaboration Sizing Tool instead, you can run the tool once because this tool supports deployments with dedicated Unified Communications Manager servers for agent phones or with a mixed cluster.
  • Use hardware-based conference resources whenever possible. Hardware conference resources provide a more cost-effective solution and allow better scalability within a cluster.
  • Have all CTI route points that are associated with the Unified CCE Peripheral Gateway (PG) JTAPI user register with the subscriber node running the CTI Manager instance that communicates with that Unified CCE PG.
  • The Cisco Unified Communications Manager Capacity Tool and the Unified Collaboration Sizing Tool do not currently measure CTI Manager impact on each VM separately. However, CTI Manager does place an extra burden on the subscriber running that process. The tools report the resource consumption based on these subscribers. The actual resource consumption on the other Unified Communications Manager subscribers can be slightly lower.
  • Count as an agent device all devices that are associated with a Unified CCE PG JTAPI user, but that a call center agent does not use. The PG is still notified of all device state changes for that phone, even though an agent does not use the phone. To increase cluster scalability, if a device is not used regularly by an agent, do not associate the device with the Unified CCE PG JTAPI user.
  • For deployments requiring large numbers of VRU ports, use Unified CVP instead of IP IVR. IP IVR ports place a significant call processing burden on Unified Communications Manager, while Unified CVP does not. Thus, Unified CCE deployments with Unified CVP allow more agents and higher BHCA rates per cluster. Size all deployments by using the Unified Collaboration Sizing Tool.
  • In deployments with multiple IP IVRs, associate those servers with different CTI Managers on different subscribers to better balance call processing across the cluster.
  • CPU resource consumption by Unified Communications Manager varies, depending on the trace level enabled. Changing the trace level from Default to Full on Unified Communications Manager can increase CPU consumption significantly under high loads. The Cisco Technical Assistance Center does not support changing the tracing level from Default to No tracing.
  • Under normal circumstances, place all subscribers from the cluster within the same LAN or MAN. Do not place all members of a cluster on the same VLAN or switch.
  • If the cluster spans an IP WAN, follow the specific guidelines for clustering over the IP WAN as described in Geographically distributed data centers in this guide and Clustering over the IP WAN in the Cisco Unified Communications Solution Reference Network Design (SRND) Guide at http:/​/​www.cisco.com/​go/​ucsrnd.

For the most current information about Unified Communications Manager and Unified CCE supported releases, see the latest version of the Compatibility Matrix for Unified CCE.

For more Unified Communications Manager clustering guidelines, see the Cisco Unified Communications Solution Reference Network Design (SRND) Guide at http:/​/​www.cisco.com/​go/​ucsrnd.

Unified Communications Manager Redundancy

With Unified Communications Manager, you can choose from the following redundancy schemes:
  • 2:1—For every two primary subscribers, there is one shared backup subscriber.
  • 1:1—For every primary subscriber, there is a backup subscriber.

Due to the higher phone usage in contact centers and the increased downtime required during upgrades, do not use the 2:1 redundancy scheme for Unified Communications Manager deployments with Unified CCE.

The following figure illustrates these options. This illustration shows only call processing subscribers and does not show publisher, TFTP, music on hold (MoH), or other servers. For details on additional cluster deployment and redundancy options, see the latest version of the Cisco Unified Communications Solution Reference Network Design (SRND) Guide at http:/​/​www.cisco.com/​go/​ucsrnd.

Figure 1. Basic Redundancy Schemes

In the following figure, the options shown all provide 1:1 subscriber redundancy. Option 1 is used for clusters supporting fewer than 150 Unified CCE agents on any supported version of Unified CM. Options 2 through 5 illustrate increasingly larger clusters. In this figure, for deployments with Unified Communications Manager 8.x and Unified CVP (not IP IVR), N is equal to 1000. For deployments with IP IVR, N is equal to 500. For other types of deployments, use the Cisco Unified Communications Manager Capacity Tool or the Cisco Unified Collaboration Sizing Tool.

Figure 2. Redundancy Configuration Options

Load Balancing for Unified Communications Manager

An additional benefit of using the 1:1 redundancy scheme is that it enables you to balance the devices over the primary and backup subscriber pairs.

With load balancing, you can move up to half of the device load from the primary to the secondary subscriber by using the Unified Communications Manager redundancy groups and device pool settings. In this way, you can reduce by half the impact of any subscriber becoming unavailable.

To plan for 50/50 load balancing, calculate the capacity of a cluster without load balancing and then distribute the load across the primary and backup subscribers based on devices and call volume. To allow for failure of the primary or the backup, the total load on the primary and secondary subscribers must not exceed that of a single subscriber. In a 1:1 redundancy pair, you can split the load between the two subscribers, configuring each subscriber with half of the agents. To provide for system fault tolerance, make sure that all capacity limits are observed so that Unified CCE agent phones, Unified IP phones, CTI limits, and so on, for the subscriber pair do not exceed the limits allowed for a subscriber's VM.

Distribute all devices and call volumes as equally as possible across all active subscribers. For instance, distributing the Unified CCE agents, CTI ports, gateways, trunks, voicemail ports, and other users and devices among all subscribers equally, minimizes the impact of any outage.

For additional information about general call processing topics such as secondary TFTP servers and gatekeeper considerations, see the Cisco Unified Communications Solution Reference Network Design (SRND) Guide at http:/​/​www.cisco.com/​go/​ucsrnd.

Deployment of Agent PG in Unified Communications Manager Cluster

Agent PGs can be deployed in a Unified Communications Manager cluster in either of the following ways:
  • The first method is to deploy an Agent PG for each pair of subscribers. In this case, each subscriber runs the CTI Manager service, and each Agent PG connects to a CTI Manager running on its corresponding subscriber pair. The following diagram shows an example where four primary subscribers are required and four backup subscribers are deployed to provide 1:1 redundancy.
    Figure 3. Deploy Agent PG for Each Pair of Subscribers

  • Another possible method is to deploy a single Agent PG for the entire cluster. This type of deployment requires a single pair of subscribers running CTI Manager. Spread agent phone registration among all the subscribers, including the subscribers running the CTI Manager service. The following diagram shows an example where four primary subscribers are required and four backup subscribers are deployed to provide 1:1 redundancy.
    Figure 4. Deploy Single Agent PG for Entire Cluster

    One benefit of this model is the reduction of the server count for the PG. Another benefit is that there is a single PIM for the entire cluster. This makes it possible to create teams that span across many subscribers, thus allowing supervisors, for example, to monitor agent phones registered to any subscriber in the cluster. However, the resource utilization on the cluster might be slightly higher in this type of deployment. Use the Cisco Unified Communications Manager Capacity Tool or the Cisco Unified Collaboration Sizing Tool to size the Unified Communications Manager servers for a particular deployment.

Sizing Considerations for Unified Mobile Agent

Unified Mobile Agent requires the use of two CTI ports per contact center call. One CTI port controls the caller endpoint, and the other CTI port controls the selected agent endpoint. The actual RTP stream is between the two endpoints and is not bridged through these two CTI ports. However, there is additional call processing activity on Unified CM when setting up calls to mobile agents through these two CTI ports (when compared with setting up calls to local Unified CCE agents).

While mobile agents may essentially log in from any location (by using the agent desktop) where they have a high-quality broadband connection and a PSTN phone, they will still be associated logically with a particular Unified CCE Peripheral and Unified Communications Manager cluster, even if the Voice Gateway used to call the mobile agent is registered with a different cluster. The agent desktop is configured with the IP address of the PG and/or CTI server to which it is associated.

For specific subscriber and cluster sizing for Unified CCE deployments, the Cisco Unified Communications Manager Capacity Tool or the Unified Collaboration Sizing Tool must be used. When sizing the cluster, input the maximum number of simultaneously logged-in mobile agents. In cases where the number of configured mobile agents is higher than the maximum number of simultaneous logged-in mobile agents, consider the pairs of CTI ports configured for mobile agents who are not logged in the Cisco Unified Communications Manager Capacity Tool by entering CTI ports type 1 with a BHCA and BHT of 0. This is similar to the method for taking into account local agent phones that are not logged in by using the CTI third-party controlled lines in the Cisco Unified Communications Manager Capacity Tool. As an alternative, or when using the Cisco Unified Collaboration Sizing Tool, you can input all mobile agents (logged-in and not logged-in) into the tool and adjust the BHCA and BHT per mobile agent accordingly. The total BHCA and BHT must remain the same as when considering simultaneous logged-in mobile agents with their actual BHCA and BHT.

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