NATläbikäimine

NATläbikäimine, often abbreviated as NAT traversal, refers to the techniques used to enable direct peer-to-peer communication between two devices located behind different Network Address Translation (NAT) devices. NAT is a common networking technique that allows multiple devices on a private network to share a single public IP address. However, it makes it difficult for external devices to initiate connections to devices behind NAT because the NAT device does not know which internal device the incoming connection is intended for.

NAT traversal aims to overcome this challenge by establishing a direct path between two peers, even if they are both behind NAT. Several methods exist, each with its own advantages and disadvantages. One common technique is UDP hole punching, where both peers send UDP packets to each other. These packets effectively "punch holes" in the NAT devices, allowing subsequent packets to pass through. Another approach involves using a STUN (Session Traversal Utilities for NAT) server. A STUN server helps a client behind NAT discover its public IP address and the type of NAT it is behind, which can then be used by the peers to establish a connection.

In some cases, when direct peer-to-peer communication is not possible, a TURN (Traversal Using Relays around NAT) server can be used. A TURN server acts as an intermediary, relaying traffic between the two peers. This is less efficient than direct communication but ensures connectivity. NAT traversal is crucial for various applications, including Voice over IP (VoIP) services, online gaming, and peer-to-peer file sharing, where direct connections are essential for optimal performance.