Supplementary Protocols and Technologies

In the realm of digital communication, Network Address Translation (NAT) plays a crucial role in managing IP addresses within private networks. However, NAT presents challenges for peer-to-peer (P2P) communications, as it obscures the IP addresses and ports of devices, making direct communication between devices difficult. This necessitates the use of NAT traversal techniques, which include protocols like STUN, TURN, and ICE, to facilitate effective P2P connectivity across different network configurations. 

STUN (Session Traversal Utilities for NAT)

STUN is a protocol designed to allow an end host to discover its public IP address and the type of NAT it is behind. This is achieved by sending a request to a STUN server located outside the NAT. The server replies with the public IP and port that is visible to the outside world, which can then be used to inform other peers about how to establish a direct connection. However, STUN may not work effectively with symmetric NATs, where the port mapping changes with every request to different external destinations. You will find detailed information about STUN in RFC8489.