Skype's Network Ditches P2P Tech for Linux Boxes

Microsoft has reportedly done away with the peer-to-peer client machines that have powered Skype's VoIP network over the last nine years. Instead, Skype now uses thousands of Linux-based servers that have been "hardened" for the most common types of hack attacks.

Skype's network overhaul was discovered just weeks ago, but the switch out is believed to have taken place several months back. Ultimately this new network is expected to prevent outages from happening again, giving Microsoft better control over Skype's system as a whole.

"The number of supernodes has dropped from 48k+ to 10k+, and all the supernodes are now hosted by Microsoft/Skype," reports Immunity Security's Kostya Kortchinsky on his personal blog. "Promotion of random eligible nodes to supernodes has stopped (through the setting of the global Boolean 33h). Ironically, those remaining supernodes run on grsec'ed Linux boxes (I hope Spender gets a sizeable donation from Microsoft). They can host a considerable amount of clients, ~100,000."

This explanation essentially means the Skype network has been reduced from over 48,000 supernodes down to over 10,000, and now there's no way that an individual user can become a supernode. The remaining supernodes are also running a version of Linux using grsecurity, the latter of which is a collection of patches and configurations designed to make servers more resistant to attacks.

Even more, these Microsoft-hosted machines are capable of accommodating significantly more users than before. Previously supernodes on the old system could handle around 800 users simultaneously, but now they can each play host to around 4,100 users with a theoretical limit of 100,000 simultaneous users. That said, the number of supernodes in the Skype network has decreased while the user capacity has increased.

"It's pretty good for security reasons because then you don't rely on random people running random stuff on their machine," Kortchinsky told Ars Technica. "You just have something that's centralized and secure."

Skype has seen nothing but growth since its debut back in 2003. However its steepest spikes have occurred within the last two years. From October 2010 to March 2011, Skype saw an additional 6 million concurrent members, but then saw seven months of flatlined growth. Then in January 2012, Skype saw an insane 104-day 9 million spike, averaging 95.5K additional signed-in users daily. Skype now plays host to over 41 million users during peak hours.

The news surrounding Skype's new network arrives after Microsoft said it was investigating reports that a modified client will allow users to see the IP address of anyone on Skype whether they're friends or strangers. "This is an ongoing, industry-wide issue faced by all peer-to-peer software companies," a Skype representative said. "We are committed to the safety and security of our customers and we are takings measures to help protect them."

Microsoft scooped up Skype back in October 2011 for a meaty $8.5 billion. Since then, Skype has arrived on Windows Phone and Sony's PlayStation Vita. There are also signs that Microsoft plans to introduce Skype as a Web app for browsers later this year, and that the popular VoIP service is finally headed to the Xbox 360 console.

UPDATE: Mark Gillett, CVP of Skype Product Engineering & Operations, sent over a little clarification about the network update, saying that it has not changed the underlying nature of Skype’s peer-to-peer architecture.

"As part of our ongoing commitment to continually improve the Skype user experience, we developed supernodes which can be located on dedicated servers within secure datacenters," he told Tom's in an email on Wednesday. "This has not changed the underlying nature of Skype’s peer-to-peer (P2P) architecture, in which supernodes simply allow users to find one another (calls do not pass through supernodes).  We believe this approach has immediate performance, scalability and availability benefits for the hundreds of millions of users that make up the Skype community."