At Ars Technica, Peter Bright details Skype’s shift, behind the scenes, from peer-to-peer connectivity to a cloud-based client/server system:
As well as addressing certain constraints of the peer-to-peer network, the new cloud-based system is used to underpin various other Skype features. For example, on the peer-to-peer network file transfers required the recipient to be present and to accept the transfer (with the file subsequently transported directly between the clients). File transfers on the new network go via the cloud, allowing fire-and-forget transfers, even to recipients that are temporarily away. This also allows a file to be downloaded by multiple recipients, or by the same recipient on multiple systems, without needing it to be retransmitted from the sender each time. The new voice and video messaging capabilities operate similarly, using cloud storage to hold voice and video messages even when the receiving client isn’t available.
As podcasters, Skype is obviously a big part of our workflow, and this transition has definitely meant some bumps along the road in terms of reliability and quality. But Bright also raises good questions about the obfuscation around Skype’s internal technology, encryption, privacy, and so on. There are other solutions than Skype for VoIP technology, of course, but none that have reached quite the level of saturation that Skype has. But technology has moved on and Skype, in many ways, has not. Microsoft’s re-architecting has a chance to bring the service into the present—and that’s something it needs.