Which protocol does Mac OS X support for establishing a VPN?

Mac OS X supports the Point-to-Point Tunneling Protocol (PPTP) for establishing a Virtual Private Network (VPN). PPTP is a method that allows for the encapsulation of data traffic within a secure tunnel, making it possible for users to connect securely to a remote network over the internet. This protocol is designed to create a direct connection between the user’s device and a VPN server, providing a secure pathway for data transmission, which is critical for maintaining the confidentiality and integrity of information being sent over potentially unsecured networks.

The other protocols listed are designed for different purposes. FTP (File Transfer Protocol) is used for transferring files between a client and a server, while SMTP (Simple Mail Transfer Protocol) is utilized for sending emails. HTTP (Hypertext Transfer Protocol) is the foundation for data communication on the World Wide Web, but it does not provide the secure, private connection characteristic of a VPN. Therefore, PPTP is the choice that aligns with VPN functionality in Mac OS X.