A virtual private network is disclosed. The network may include a first private network including a first firewall interposed between a first private network and a public network and a second firewall interposed between a first client machine and the first firewall machine. The network may include a...http://www.google.com.hk/patents/US20070101421?utm_source=gb-gplus-share專利 US20070101421 - VIRTUAL PRIVATE NETWORK
