From Fedora Project Wiki
New
A SIP, XMPP and WebRTC service is under construction at https://fedrtc.org
The service is very similar to the Debian Developer RTC service and much of the Debian Developer's RTC User Guide is relevant to Fedora users.
General notes about community collaboration at the communicating and getting help page.
Old
In the past, an Asterisk SIP service was provided for the Fedora community, it is documented here but it does not exist any more.