Unified Communications Manager - Session Manager Edition: Session Manager Designs

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A deployment using Cisco Unified CM Session Manager Edition is essentially a Unified CM cluster with trunk interfaces only ( although IP endpoints are also allowed if required). It allows aggregation of multiple Unified Communications systems, referred to as leaf systems.


With Cisco Unified CM 7.1(3) and later releases, Unified CM Session Manager Edition supports the following features:

• H.323 Annex M1 intercluster trunks

• SIP intercluster trunks

• SIP trunks

• H.323 trunks

• MGCP trunks

• Voice calls

• Video calls

• Fax calls

• Encrypted calls



Unified CM Session Manager Edition may also be used to connect to third-party unified communications systems such as IP PSTN connections, PBXs, and centralized unified communications applications. However, as with any standard Unified CM cluster, third-party connections to Unified CM Session Manager Edition should be system tested for interoperability prior to use in a production environment.


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When to Deploy Unified CM Session Management Edition

Cisco recommends deploying Unified CM Session Management Edition if you want to do any of the following:

• Create and manage a centralized dial plan

Rather than configuring each unified communications system with a separate dial plan and trunks to connect to all the other unified communications systems, Unified CM Session Management Edition allows you to configure the leaf unified communications systems with a simplified dial plan and trunk(s) pointing to the Session Management cluster. Unified CM Session Management Edition holds the centralized dial plan and corresponding reachability information about all the other unified communications systems.

• Provide centralized PSTN access

Unified CM Session Management Edition can be used to aggregate PSTN access to one (or more) centralized IP PSTN trunks. Centralized PSTN access is commonly combined with the reduction, or elimination, of branch-based PSTN circuits.

• Centralize applications

The deployment of a Unified CM Session Management Edition enables commonly used applications such as conferencing or videoconferencing to connect directly to the Session Management cluster, thus reducing the overhead of managing multiple trunks to leaf systems.

• Aggregate PBXs for migration to a Unified Communications system

Unified CM Session Management Edition can provide an aggregation point for multiple PBXs as part of the migration from legacy PBXs to a Cisco Unified Communications System.

Differences Between Unified CM Session Management Edition and Standard Unified CM Clusters The Unified CM Session Management Edition software is exactly the same as Unified CM. However, the software has been enhanced significantly to satisfy the requirements and the constraints of this new deployment model. Unified CM Session Management Edition is designed to support a large number of trunk-to-trunk connections, and as such it is subject to the following design considerations:

• Capacity

It is important to correctly size the Unified CM Session Management cluster based on the expected BHCA traffic load between leaf Unified Communications systems (for example, Unified CM clusters and PBXs), to and from any centralized IP PSTN connections, and to any centralized applications. Determine the average BHCA and Call Holding Time for users of your Unified Communications system and share this information with your Cisco account Systems Engineer (SE) or Cisco Partner to size your Unified CM Session Management Edition cluster correctly.

• Trunks

Where possible, avoid the use of static MTPs on Unified CM trunks (that is, "MTP required" must not be checked on the leaf or Session Management Unified CM SIP or H.323 trunks). Trunks that do not use "MTP required" offer more codec choices; support voice, video, and encryption; and do not anchor trunk calls to MTP resources. Dynamically inserted MTPs can be used on trunks (for example, for DTMF translation from in-band to out-of-band). If SIP Early Offer is required by a third-party unified communications system, use either the "Early Offer support for voice and video calls (insert MTP if needed)" on Unified CM SIP trunks or the Delayed Offer to Early Offer feature with Cisco Unified Border Element. Dynamically inserted MTPs can be used on trunks (for example, for DTMF translation from in-band to out-of-band).

• Unified CM versions

Both the Unified CM Session Management Edition and Unified CM leaf clusters should be deployed with Cisco Unified CM 7.1(2) or later release. Earlier versions of Unified CM can be deployed but might experience problems that can be resolved only by upgrading your cluster to Unified CM 7.1(2) or later release.

• Interoperability

Even though most vendors do conform to standards, differences can and do exist between protocol implementations from various vendors. As with any standard Unified CM cluster, Cisco strongly recommends that you conduct end-to-end system interoperability testing with any unverified third-party unified communications system before deploying the system in a production environment. The interoperability testing should verify call flows and features from Cisco and third-party leaf systems through the Unified CM Session Management cluster. To learn which third-party unified communications systems have been tested by the Cisco Interoperability team, go to www.cisco.com/go/interoperability and select the link for Cisco Unified Communications Manager - Session Management Edition.

• Load balancing for inbound and outbound calls

Configure trunks on the Unified CM Session Management Edition and leaf unified communications systems so that inbound and outbound calls are evenly distributed across the Unified CM servers within the Session Management cluster. For more information on load balancing for trunk calls, refer to the UC SRND chapter on Cisco Unified CM Trunks, http://www.cisco.com/en/US/docs/voice_ip_comm/cucm/srnd/8x/trunks.html

• Design guidance and assistance

For more information on Unified CM Session Management Edition designs and deployments, refer to the Cisco Unified Communications Manager Session Management Edition Deployment Guide, available at

http://www.cisco.com/en/US/docs/voice_ip_comm/cucm/session_mgmt/deploy/8_5_1/cucmse-851-deploy.html

Unified CM Session Management Edition designs should be reviewed by your Cisco SE in conjunction with the Cisco Unified CM Session Management Team.


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