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The Polycom RealPresence DMA System’s Three Configurations

Depending on your organization’s needs, you can deploy the Polycom RealPresence DMA system in one of the following three configurations.

Two-server Configuration

Single-server Configuration

Supercluster Configuration

Two-server Configuration

The Polycom RealPresence DMA system is designed to be deployed as a pair of co-located redundant servers that share the same virtual IP address(es). The two-server cluster configuration of the Polycom RealPresence DMA system has no single point of failure within the system that could cause the service to become unavailable.

The two servers communicate with the public and/or private network that connects them. To determine which one should host the public virtual IP address, each server uses three criteria:

Ability to ping its own public physical address

Ability to ping the other server’s public physical address

Ability to ping the default gateway

In the event of a tie, the server already hosting the public virtual address wins.

Failover to the backup server takes about five seconds in the event of a graceful shutdown and about 40 seconds in the event of a power loss or other failure. In the event of a single server failure, these things happen:

All calls that are being routed through the failed server are terminated (including SIP calls, VMR calls, and routed mode H.323 calls). These users simply need to redial the same number, and they are placed back into conference or reconnected to the point-to-point call they were in. The standby server takes over the virtual signaling address, so existing registrations and new calls are unaffected.

Direct mode H.323 point-to-point calls are not dropped, but the bandwidth management system loses track of them. This could result in overuse of the available network bandwidth.

If the failed server is the active web host for the system’s management interface, the active user interface sessions end, the web host address automatically migrates to the remaining server, and it becomes the active web host. Administrative users can then log back into the system at the same URL. The system can always be administered via the same address, regardless of which server is the web host.

The internal databases within each Polycom RealPresence DMA system server are fully replicated to the other server in the cluster. If a catastrophic failure of one of the database engines occurs, the system automatically switches itself over to use the database on the other server.

Single-server Configuration

The Polycom RealPresence DMA system can also be deployed in a single-server configuration. This configuration offers all the advantages of the Polycom RealPresence DMA system except the redundancy and fault tolerance. It can be upgraded to a two-server cluster at any time.

The Polycom RealPresence DMA System Operations Guide and online help generally assume a redundant two-server cluster. Where there are significant differences between the two configurations, those are spelled out.

Supercluster Configuration

To provide geographic redundancy and better network traffic management, up to 10 geographically distributed Polycom RealPresence DMA system clusters (two-server or single-server) can be integrated into a supercluster. All five clusters can be Call Servers (function as gatekeeper, SIP proxy, SIP registrar, and gateway). Up to three can be designated as Conference Managers (manage an MCU resource pool to host conference rooms).

The superclustered Polycom RealPresence DMA systems can be centrally administered and share a common data store. Each cluster maintains a local copy of the data store, and changes are replicated to all the clusters. Most system configuration is supercluster-wide. The exceptions are cluster-specific or server-specific items like network settings and time settings.

Clusters versus Superclusters

Technically, a standalone Polycom RealPresence DMA system (two-server or single-server) is a supercluster that contains one cluster. All the system configuration and other data that is shared across a supercluster is kept in the same data store. At any time, another Polycom RealPresence DMA system can be integrated with it to create a two-cluster supercluster that shares its data store.

It is important to understand the difference between two co-located servers forming a single RealPresence DMA system (cluster) and two geographically distributed RealPresence DMA system clusters (single-server or two-server) joined into a supercluster.

A single two-server cluster has the following characteristics:

A single shared virtual IP address and FQDN, which switches from one server to the other when necessary to provide local redundancy and fault tolerance.

A single management interface and set of local settings.

Ability to manage a single territory, with no territory management backup.

A single set of Call Server and Conference Manager responsibilities.

A supercluster consisting of two clusters (single-server or two-server) has the following characteristics:

Separate IP addresses and FQDNs for each cluster.

Separate management interfaces and sets of local settings for each cluster.

Ability for each cluster to manage its own territory, with another cluster able to serve as backup for that territory.

Different Call Server and Conference Manager responsibilities for each territory and thus each cluster.

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