The office communicator uses rtcdll.dll for its RTP communication, how come M$ did not make this available for the Mobile 5 platform via an interop or in the compact framework.  There are numerous posts out there for people looking to develop custom VOIP applications for the mobile platform and are having to move to other platforms or 3rd party providers.  I work for a company that develops sip based software and we are a M$ centric shop and a valued M$ partner.  It would be great for us to use mobile 5.0 with the RTC component instead of going through a 3rd party.  It is obvious that it can be done without the need to use platform builder, since when you install the communicator you can do voip....what gives.....Embarassed