It is worth checking out Tom’s analysis of Fusion telecommunication’s “intriguing” p2p solution.

"This technology will give Fusion the opportunity to expand its existing suite of paid service offerings and participate in the growing peer-to-peer telephony market through its efonica brand, including the free call segment now dominated by Skype," said Matthew Rosen, President and Chief Operating Officer of Fusion.

Fusion claims that the technology took more than five years to develop incorporating a "unique approach that builds upon globally accepted VoIP standards and seamlessly integrates with Fusion’s carrier-class network and back-office infrastructure". According to Tom, the release was inexplicably vague as to what exactly they have done from a technical perspective, but the P2P SIP certainly caught Tom’s eye.