NAT traversal techniques are required for many network applications, such as peer-to-peer file sharing and voice over IP.
However, applications such as peer-to-peer file sharing, VoIP services, and video game consoles require clients to be servers as well.
Furthermore, many of these types of services carry IP address and port number information in the application data, potentially requiring substitution with deep packet inspection.
Some methods use the server only when establishing the connection, while others are based on relaying all data through it, which increases the bandwidth requirements and latency, detrimental to real-time voice and video communications.
Hole punching techniques, such as STUN and ICE, fail in traversing symmetric NATs without the help of a relay server, as is practiced in TURN.
Hosted NAT traversal (HNT) is a set of mechanisms, including media relaying and latching, that is widely used by communications providers for historical and practical reasons.