NATfriendly

NATfriendly is a term used to describe networking designs, protocols, and software that are optimized to operate effectively behind network address translation (NAT) devices. NATfriendly approaches aim to minimize reliance on globally routable IP addresses and to enable peers and services to establish and maintain communication even when direct inbound connectivity is restricted by NAT.

NATfriendly techniques include using outbound-initiated connections, maintaining periodic keep-alives, and employing NAT traversal methods such as STUN (Session Traversal Utilities for NAT), ICE (Interactive Connectivity Establishment), and TURN (Traversal Using Relays around NAT). Many NATfriendly systems also use rendezvous or signaling servers, name resolution strategies that tolerate private addressing, and relay-based fallbacks when direct connectivity is not possible. Some designs leverage UPnP or NAT-PMP to request port mappings where allowed.

Applications of NATfriendly design appear in real-time communications and peer-to-peer ecosystems. WebRTC, for example, relies on ICE, STUN, and TURN to establish media paths across NATs. Online gaming, VoIP services, and distributed file-sharing protocols often implement NAT-friendly features to improve connectivity for users behind residential gateways.

Limitations include added latency from relay paths, dependence on intermediary servers, and variability across NAT types and operator configurations. Security considerations involve exposing signaling paths, encryption of media and control data, and potential exposure through UPnP.

See also NAT traversal, NAT, STUN, ICE, TURN, UPnP, NAT-PMP.