Tailscale's NAT Traversal: A Deep Dive

This Tailscale blog post details how their VPN overcomes the challenges of NAT (Network Address Translation) to enable direct device-to-device connections. It explains NAT's workings and various techniques to handle NAT and firewalls, including STUN for discovering public IPs, the birthday paradox for faster port probing, and DERP as a fallback relay. Finally, it introduces the ICE protocol, which automatically tries various methods, selecting the best connection to ensure reliable connectivity.