It’s late 2003, and I’ve just had a crystal-clear voice conversation with a colleague in London from my desk in Seattle. The best part? It cost us zero cents. We weren't using expensive telephony equipment; we were using Skype.
We’ve had VoIP before (like Net2Phone), but it was always clunky, had terrible latency, and required you to mess with your firewall settings. Skype just... works.
The P2P Engine
Skype was created by Niklas Zennström and Janus Friis, the same duo behind the Kazaa file-sharing network. And just like Kazaa, Skype is built on a decentralized P2P architecture.
Most VoIP services use a central server to handle the call routing. Skype uses "Supernodes"-user computers with high bandwidth and no firewalls-to act as the infrastructure. When you make a call, the Skype network finds the most efficient path through these peers.
Firewall Traversal
The real genius of Skype is how it handles firewalls and NAT. It uses "STUN" and "ICE" techniques to find holes in the firewall, and if all else fails, it relays the encrypted call through a Supernode. To the user, it’s invisible.
Security and Compression
Skype uses a proprietary wideband codec that sounds much better than a standard telephone line. And unlike the traditional phone network, every call is encrypted from end-to-end using AES.
Looking Ahead
Skype is a "disruptive technology" in the truest sense. The traditional telcos should be terrified. Why pay for a long-distance call when you can have a better-quality conversation for free over the internet?
From a technical perspective, it’s a brilliant application of P2P. It shows that you can build a massive, high-performance communication network without spending a fortune on central servers. The infrastructure is provided by the users themselves.