This section
provides an overview of the system topology and describes the relationship
between the types of nodes in the topology.
Clusters
Clusters provide a
mechanism for distributing call processing and database replication among
multiple servers. They provide transparent sharing of resources and features
and enable system scalability.
A cluster
comprises a set of
Cisco
Unified Communications Manager (Unified Communications Manager) nodes
and
IM and
Presence nodes that run compatible software versions.
Publisher
Nodes and Subscriber Nodes
Within a cluster,
there is a database publisher for each type of node that you install.
When you install
Unified
Communications Manager, the installation wizard prompts you to
specify whether the node you are installing is the first node in the cluster.
The first
Unified
Communications Manager node that you install becomes the publisher
node, because it publishes the voice and video database to the other
Unified
Communications Manager nodes in the cluster. All subsequent nodes in
the cluster are called subscriber nodes. Each subscriber node must be
associated with the publisher node. You must set up all subscriber nodes in the
system topology on the publisher node before you install the software on the
subscriber nodes.
When you install
IM and
Presence nodes, the first node that you install functions as the
server for the
IM and
Presence database. Because this node publishes the database for all
of the
IM and
Presence nodes in the cluster, it is referred to as the
IM and
Presence database publisher; however, you must install this and all
other
IM and
Presence nodes as subscribers of the
Unified
Communications Manager publisher node. As with other subscriber
nodes, you must add these in the system topology before you install the
software.