How do I get OCS presence to work inside of SharePoint?

This is was from a Midwestern university which asked a question around how does MOSS and OCS work together. Below is a sample of how presence or click to chat/call is surfaced in MOSS:

Based on above you would think there would be some server side configurations on MOSS required to surface OCS presence or click to chat/call functionality. The reality is this is all performed with client side controls and the Office Communicator client.

In order for rich presence and/or click to chat/call to work in SharePoint the following is required on the end user’s side:

• Office Communicator Client 2007 installed and logged into
• Office 2003 or Office 2007 installed which installs the ActiveX control that allows you to surface presence in MOSS
• Optional - Outlook 2003 or Outlook 2007 logged into for the ActiveX control to pull availability information

How does it work?

When a SharePoint page is displayed, the ActiveX control is invoked on the client to display the presence icons on the web page such as above. The ActiveX control talks to Office Communicator locally on the client to request the presence status of the user(s) being shown. The ActiveX control also talks to Outlook (if Outlook is open) to gather additional information such as availability based on calendar. Outlook gets this information from Exchange Server. Because this information is collected from the other client-side applications that the user is already running, you can be sure that the presence controls only ever show information that the user already had permission to see