The following figure shows a sample Office Communications Server 2007 R2 topology and the protocol flow in that topology.
Office Communications Server can be installed in several configurations, starting with a single Standard Edition server for simple/common installations to multiple Enterprise Edition servers where high availability at scale is a requirement.
Standard Edition (Single Server Installation)
Office Communications Server 2007 R2, Standard Edition contains the same server components as Enterprise Edition. However, in this configuration all the server components required to provide presence, instant messaging (IM), multiparty Web conferencing and desktop sharing, and audio/video (A/V) conferencing are installed on a single computer. All voice components and applications are also installed on the same computer. In a Standard Edition configuration, the Back-End Database Server also runs on the single physical server. Thus, all elements share the same server resources.
This configuration is designed to support a small number of users and concurrent meetings and is not designed to scale to larger deployments. Ease of installation and server management are the primary goals for this type of server installation.
An Enterprise Edition server can provide an organization with scaling and high availability. Enterprise Edition servers are deployed in a pool regardless of whether there is one server or multiple servers. An organization can deploy Enterprise Edition configuration by using a single Enterprise Edition server, with or without a hardware load balancer, or multiple Enterprise Edition servers behind a hardware load balancer. Multiple servers provide high availability such that, if one Front End Server fails, clients can detect the failure and automatically reconnect to one of the other Front End Servers.
Consolidated configuration is the recommended topology for most organizations, both in terms of scaling and simplified administration.
In Office Communications Server, each Front End Server in an Enterprise Edition consolidated configuration includes registration, presence, routing, conferencing, and enterprise telephony functionality. Each Front End Server runs an instance of the Focus, Focus Factory, Conferencing Server Factory, and all conferencing servers. Each Front End Server also runs an instance of all voice applications (for example, Voice Inbound and Outbound Routing, Outside Voice Control, Response Group Service, Communicator 2007 R2 Attendant, and Conferencing Announcement Service). The most important aspect of this architecture is that all Front End Servers are equivalent in functionality. The same software components (that is, Focus, Focus Factory, Conferencing Server Factory, conferencing servers, and voice applications) are installed on all the Front End Servers. A consolidated configuration helps simplify setup and management, while still providing high scalability, availability, and failure recovery.
Expanded configuration was introduced in Office Communications Server 2007. The primary advantage of the expanded configuration in Office Communications Server 2007 was its ability to scale in very large deployments. However, the scalability limitations of consolidated configuration, which is simpler to deploy, have been removed in Office Communications Server 2007 R2, and consolidated configuration is now the preferred topology for most organizations.
In an Enterprise Edition expanded configuration, the A/V Conferencing Server and Web Conferencing Server server roles are distributed and run on separate servers. Expanded configuration is no longer a recommended scenario and requires command-line installation and configuration in Office Communications Server 2007 R2.