A portal won't necessarily take care of the issue. It has to do with handing off the authentication. IIS won't do that, which is really a good thing. However, Maestr0's idea will probably work best. We are experiencing a similar issue with SharePoint portal server. If the servers/servicees were all on one machine, there probably wouldn't be a problem, but you have to do machine-to-machine authentication for what you described. So, you get the two authentication requests.