CallManager Cluster

[rob.leetun]

There is some intense dicussion on what is a CallManager (CCM) Cluster. Some say it is when all the CCMs are at one site with one switch, others say it is MAN that consists of PUB and SUB at the main site with two other sites that have just a SUB and have GB and fiber connection. What are your thoughts?

[sgelli]

A Cisco CallManager cluster is a set of two or more Cisco CallManager servers that share the same database and resources. For example, a cluster might consist of three Cisco CallManager servers that you set up as a cluster. You specify the servers, each of which can perform more than one function, as follows:

Database publisher server

TFTP (Trivial File Transfer Protocol) server

Application software server

Primary call-processing server

Secondary call-processing server

With clusters, you can extend call processing across an IP network to provide call processing at a remote location.

Clusters provide:

Redundancy. When a primary Cisco CallManager server in a cluster fails, a failover server can take over the call-processing functions. After the problem with the primary server has been resolved, it resumes its call-processing functions.

Sharing of resources and features. A cluster has only one database publisher and one TFTP server, while all other servers subscribe to the publisher database and maintain their own copies of it. The Cisco CallManager servers in the cluster read data from and write data to the publisher database and periodically update the subscriber copies of the database from the publisher database.

System scalability. As a company expands, clusters can be added to provide call processing at multiple sites, yet remain linked through the IP WAN and the PSTN to form a seamless phone system. Or clusters may be added to a single site to provide more uOne ports (or sessions) and more call processing for additional extensions.

The below URL was written for Unity integration with CallManager cluster, but explains what a CallManager cluster is:

http://www.cisco.com/en/US/products/sw/voicesw/ps2237/products_white_paper09186a00800872bc.shtml#1008172

Hope that helps.

Regards,

Srikanth

[rob.leetun]

Thanks for the response on clustering. However, I did not receive the answer that I was looking for. Let me describe our environment and then you can respond again, thanks. We have a PUB and SUB at our main facility, we have a SUB at another facility, and we have another SUB at another facility. The distance between these facilities is about 1 mile each. We have Fiber and GB backbone per say between each of the facilities, GB link between the PUB and SUB at the main facility. Would this count as a cluster environment in Cisco eyes, or do we need to move all the SUBs and PUB to one location to have a clustered environment? Again thanks for your quick help!!

[sgelli]

Hello Rob,

The (Publisher and Subscriber) servers don't have to be in the same location to form a cluster. In your case, a Pub and a Sub at one location and the rest of the Subs at different locations is still a CallManager cluster.

Here are the requirements of a CallManager Cluster:

The maximum round trip time (RTT), a packet takes to get from one server to the other, of 40 ms is allowed between any two servers in the Cisco CallManager cluster.

This time equates to a 20 ms maximum one-way delay, or a transmission distance of approximately 1860 miles (3000 km) under ideal conditions.

I am pretty sure this can be very easily accomplished in your network. For more information on this topic, you can read the "CallManager Release 3.3 Solution Reference Network Design (SRND)" at

http://www.cisco.com/en/US/netsol/ns340/ns394/ns165/ns268/networking_solutions_design_guidances_list.html

Hope that helps.

Regards,

Srikanth