Office Communications Server 2007 provides the following server roles with specific purposes for building your Enterprise instant messaging and conferencing infrastructure:

The Enterprise Edition scales the capacity of the Standard Edition Server to a larger magnitude by splitting the different logical functionality into separate physical servers. The Director is a logical server role and really is a Standard Edition Server. What differentiates the Director from a Standard Edition Server is the lack of users homed on it. It serves to proxy or redirect user connections to the user's home server or home pool.

The Edge Servers are deployed in the network perimeter to enable connectivity outside the organization's private network. The Access Edge Server allows remote users to sign in to their organization's Office Communications Server infrastructure, and communicate using IM. The Access Edge Server is also required to allow internal users to communicate over IM with federated partners and with subscribers to any of the three public IM providers (AOL, MSN, Yahoo). The Web Conferencing Edge Server allows internal users to collaborate with external users. The A/V Edge Server allows internal users to communicate via audio and video with external users.

The Archiving and CDR Server serves the role of performing server-side recording of call details and archiving of all IM communications of employees within the organization's network, as well as outside the network.

Communicator Web Access provides a Communicator client experience from a Web browser for users without Office Communicator installed on their computers.