To establish secure communication with cloud, client often use an internet. To such communication Virtual Private Network (VPN) can be used. An advantage of such solution is that customers of internet outside of VPN do not have access to data transmitted via VPN. Generally VPN has much more widely application, for example to remote working in corporate network. To build Virtual Private Network we can use one of the following protocols: IPsec (Internet Protocol Security, IP Security) PPTP(Point to Point Tunneling Protocol), L2TP(Layer Two Tunneling Protocol), OpenVPN.

  http://en.wikipedia.org/wiki/Tunneling_protocol