The reason this component is considered optional is because without it deployed an external Lync client can still connect to Lync and most features will function (IM, Presence, Calls, Desktop Sharing, etc) as will federated communications. The Reverse Proxy server is an optional, external component that is not a Lync Server role and is not defined in the Lync Topology. Everything else (SIP, PSOM, ICE, etc) are all provided by the Edge server. More accurately it could be said that client communications to servers over HTTP and HTTPS are the types of traffic that are not handled by the Edge server. Note that this does not generically mean “stuff over ports 80 and 443” as TCP 443 is used throughout Lync for a variety of different communications. The Edge server is responsible for handling all communications and payloads in Lync Server which are made available to external and federated users with one exception: anything related to Web Services. Throughout the documentation a Reverse Proxy Server will be referred to often and it still seems like this concept is often glanced over or not clearly understood. Overviewįirstly the most important concept to understand when dealing with externally publishing Lync services is exactly what the Edge Server is responsible for handling as well as what it is NOT designed to do. Although most of this material is not new and can be found in various places this article is intended as summary reference for readers new to the elusive concepts of Edge and Reverse Proxy services. Amazingly enough these topics still comes up daily in technical forums, planning discussions with customers, and when troubleshooting improper deployments.