In simple words tunneling is a method of bypassing firewall or proxy restrictions using some tunnelling protocols. It works by creating a "tunnel", or a communications channel that makes the firewall think that it is getting traffic from a web browser. Communications content is delivered through this tunnel to our gateway or your own personal gateway. The gateway extracts your content from the tunnel and sends it to the destination. When your counter party responds everything goes back the same way. Tunnelling can be used when your company, college, university, ISP blocked certain programs, FTP, telnet.