Lync Team published a visio diagram with the protocol workloads. Good stuff.
This poster shows each workload in Lync Server 2010, describing relationships, dependencies, the servers that initiate connections, and certificate requirements. Relationships between Microsoft Lync 2010 communications software, Microsoft Lync 2010 Phone Edition, Microsoft Office Live Meeting 2007, Microsoft Lync Web App, and other communications software are also described. SIP and XMPP connection patterns are shown for Yahoo!, MSN, AOL, Gmail, and Jabber.
Download it from here:http://www.microsoft.com/downloads/en/details.aspx?FamilyID=ad8ff3fb-014e-4fd7-8003-436d896ab0c6