Protocols in development by the IETF to support secure data exchange. Once completed, IPSec is expected to be widely deployed to implement Virtual Private Networks (VPNs). IPSec supports two encryption modes: Transport and Tunnel. Transport mode encrypts the data portion (payload) of each packet but leaves the header untouched. Tunnel mode is more secure since it encrypts both the header and the payload. On the receiving side, an IPSec-compliant device decrypts each packet.