SIPshare is an implementation of a Gnutella-type peer-to-peer file sharing network using SIP (Session Initiation Protocol). There are no SIP proxies, no central servers; it is a purely peer-to-peer application.
From the web page:
The emerging ubiquity of SIP as a general session-initiation enabler provides a rare opportunity to offer users all manner of P2P applications over a common protocol, instead of inventing a new protocol for each new P2P application that comes along.
EarthLink wants to point the way and aid the cause of these new applications by demonstrating in open source working code that SIP can host powerful applications beyond those that immediately come to mind, that is, voice and video.
We chose file sharing to illustrate how SIP can be used to build an alternate P2P application, but file sharing itself is not the point — file sharing, of course, has been done. EarthLink SIPshare demonstrates that it is conceivable that voice over IP, where voice is just content of a different form, itself can be implemented using SIP in a fully standards-based P2P network. In other words, the effect of Skype, but with one important difference: using standards-based protocols, as EarthLink SIPshare does for content sharing.