I read the OCS 2007 Edge Server Deployment Guide before I posted my question. At your suggestion, I read the section on "Configure Federation" again. Perhaps I'm being dense, but I still don't see where they discuss the protocols used. My client is a provider of IM and audio conferencing servers. I need to build a gateway that enables OCS federation with my client's servers. Can anyone point me in the right direction? I'm drowning in details.