Microsoft Lync 2010 was released in 2011 (by Microsoft) to replace Microsoft Office Communicator 2007 R2 - an instant messenging and communications tool for large companies.
Lync 2010 can be thought of as a super version of Microsoft Live Messenger. In addition to instant messenging capabilities, the product can also be hooked into Exchange server and Outlook to allow users to see a traffic lighted 'presence' indicator for their contacts. This allows people at bigger companies to see if someone is at their desk (or at least logged into Outlook) before an attempt is made to contact them.
Lync 2010 also uses SIP to enable computer based phone conversations and conference calls.
The Lync 'presence' is derived by asynchronous calls to Outlook and Exchange Server, some of these calls are to wrappers of COM objects which can be viewed using a reflection tool.
