Sep 19, 2010
Btw what does WPF hosting on first physical tier mean? If you are trying to host WPF as browser application, then it can be hosted on the same IIS box as the service layer. I assume you meant WPF application installed on the client machine.
You are correct about hosting services on 2nd machine - the service layer should be the only entry point for any external request (either from a WPF, ASP.NET web or a mobile device). Also in future one can easily scale the application or provide multi-tenant feature through re-directing services (through routing feature in 4.0) to services running on different machines.