If we use the standard layering model, the network layer is the lowest we can go and still provide end-to-end security. Network-layer security protocols can provide blanket protection for all upper-layer application data carried in the payload of an Internet Protocol (IP) datagram without requiring a user to modify the applications. This transparency of use is quite important for seamlessness across platforms.

Internet-based networking: IPSec
One VPN framework is IP Security Architecture (IPSec), an open source framework defined by the IPSec Working Group of the IETF.

IPSec's Working Group has defined protocols in major areas of concern. These are: data origin authentication, data integrity, replay protection, crypto key management, and data confidentiality. The IETF has come up with specific protocols for each of these areas, and the frameworks with which to apply them.