Ring is the next generation of the SFLphone project produced by the open source software firm Savoir-faire Linux. Through 10 years of development as SFLphone, it has refined the features typically anticipated in a VoIP client — compatibility with SIP and IAX, multiparty calls, call-recording capabilities, and support for various codecs. Ring clients are available for Windows, OS X, and Linux -- with separate native interfaces for GNOME or KDE desktops to match user preference.
Ring uses OpenDHT (a distributed hash table) to connect users instead of a centralized SIP server system such as Asterisk. OpenDHT is an implementation of the same decentralized, peer-to-peer system used in BitTorrent's distributed tracker, allowing Ring to bypass the server-client methodology by passing along user information to each user.
Image: Savoir-faire Linux