This will route IP packets from one place to another over a single IP connection made using UDP or TCP
http://www.hoagieshouse.com/apps/IP_Tunnel.html
Why deploy a Virtual Private Network? It is important to first understand the needs of your environment and then decide whether tunneling will fulfill those needs.
http://www.quepublishing.com/articles/article.asp?p=130890&rl=1
A cheap preventive measure that can help you avoid intrusion and attack on your wireless network.
http://www.quepublishing.com/articles/article.asp?p=387173&rl=1
how to create a virtual private network without having a virtual nervous breakdown.
http://www.quepublishing.com/articles/article.asp?p=101757&rl=1