US Patent 7711800 Network connectivity determination

The present invention provides a method by which the connectivity status of network connections on a PC is determined in real-time by passively reviewing packet information from the TCP/IP stack. To achieve high accuracy of the connectivity status determination, the method involves the determination of the edge of a local network. In cases where little or no network traffic is observed on the network, scalable active probing methods are designed to make accurate connectivity determination. Special considerations for network setups like networks with web proxy servers, NAT or edge firewalls are also included to improve the accuracy of the determination in those environments.