This means packages providing SIP (and soon XMPP/Jabber) will hopefully be under much more scrutiny from developers in the lead up to the next major Debian release, codename jessie, expected early 2015.
Although the user guide provides setup details for several packages and softphones, including Jitsi and Lumicall, the developers of the core SIP server have not indicated that any specific package should be preferred and it is up to each user to choose the client that best suits their needs.
Discussion has already started about replicating this technology for the Fedora community.
Users of the Lumicall softphone on Android are already able to make federated SIP calls, so just dialing email@example.com from Lumicall is sufficient to make a call to a Debian Developer and see federated SIP working.
People who want to try SIP federation for their workplace or any other organisation are encouraged to see the Real-time Communications (RTC) Quick start guidetags: promote