Network firewall and NAT traversal for TCP and related protocols

Abstract

A message passing protocol allows two clients to establish a connection even when the clients are behind different NAT devices such as NAT firewalls. Beneficially, the protocol does not require that either client has knowledge of where the other client is located (e.g., behind the same NAT device or behind a different NAT device). When two clients want to establish a connection, the clients exchange identifying information with each other by passing the information through a rendezvous server. Based on the identifying information, each client determines and sends a plurality of synchronization packets to a number of different predicted addresses. When synchronization packets reach the actual addresses of both devices, a connection can be established between the clients.

Description

BACKGROUND1. Field of the InventionThe invention relates generally to the field of computer networking and more particularly to traversing NAT devices and firewalls.2. Description of the Related ArtsIn many computer network applications (e.g., peer-to-peer networking), it is desirable for two or more clients to establish direct connections with each other without requiring all information to pass through a centralized server. To connect to another network node a client generally sends a message to a recipient node requesting a connection. However, if the intended recipient node is behind a firewall or other network address translation (NAT) device, this connection request may be blocked. This is because a NAT device may be configured to only allow messages to reach an intended recipient when the message is in response to communication initiated by the recipient. Unsolicited communications are generally dropped. Alternatively, a NAT device may map a given internal IP address and port...

AI Technical Summary

Problems solved by technology

However, if the intended recipient node is behind a firewall or other network address translation (NAT) device, this connection request may be blocked.

Alternatively, a NAT device may map a given internal IP address and port to a different external IP address and / or port for a multitude of reasons, making it similarly difficult to reach a given node.

As a result, the nodes will be unable to connect to each other.

This creates a challenging problem in applications such as peer-to-peer networking, or other network applications that are not specifically peer-to-peer, but nevertheless utilize direct communication between two devices on a network.

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