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. Mobility Services and corrections in the IM and Presence workload are included with version 5.11.

It is a great place to start to understand how the various elements of Lync work together

It can be downloaded here: Lync 2010 workload Poster

Zoom it provides a great way to review the poster if you don't have a 60" screen or printer ;-)
Lync Workload Poster 5.10 on Zoomit