For an interesting explanation of how the Skype integration with Facebook for video calling actually works on the back end, check out this post on Skype's internal blog by chief technology strategist Jonathan Rosenberg.
To me, the most interesting fact revealed in Rosenberg's post is that Skype's famous P2P architecture is becoming more of a hybrid, with a more significant datacenter component; evidently a necessity for scaling Skype to the kind of ubiquity it expects to have with Facebook as a channel, and to manage the interactions with the Facebook platform. Here's what he writes:
Even though Skype leverages its P2P technology to help achieve scale, we still rely on server infrastructure for several parts of the solution. To handle all of this [i.e., the Facebook integration], Skype has substantially increased server counts and added bandwidth in all of our data centers.
Skype had already started going down the road of a more hybrid datacenter/P2P architecture as it seeks to harden its service against the kinds of major outages it has suffered in the past. In his keynote address at Enterprise Connect Orlando 2011, then-head of Skype's enterprise division David Gurle said the company was bringing the "supernode" element of its P2P architecture in-house, instead of allowing it to be distributed within the Skype user base--i.e., the hosts that make up the fabric of the P2P architecture.
It's another indication of why the Facebook move is such a milestone for Skype and--it's not an exaggeration to say--public network communications in general. Skype may be free, and Facebook may be free, but if Facebook is trying to become the platform that Internet users "live" on--and if Skype is trying to be the real-time communications enabler for that platform--the stakes just got a lot higher for Skype. Inevitably, that means Skype has to take more of the processing of the service in house.
The Facebook integration is a big deal because it really does make Skype the odds-on favorite to become the next public communications network. Now you can "call" someone via Skype without pre-arranging connectivity with them in a one-off arrangement that doesn't scale globally. But if the integration doesn't work for users, both Facebook and Skype take a major credibility hit, opening the door to a competitor, most likely Google.
If we get down to a manageable number of new public network service providers--say, Skype, Google, and maybe there's room for a couple more--then that handful of providers can federate and peer to effect true any-to-any IP communications network connectivity, much as the long-distance carriers exchange voice traffic in the legacy PSTN.
