What is a Virtual Private Network (VPN) primarily built upon?

A Virtual Private Network (VPN) is primarily built upon tunneling protocols. These protocols are crucial because they create secure, encrypted connections between devices over the internet or other untrusted networks. By encapsulating data packets within another packet, tunneling protocols provide a secure "tunnel" through which information can travel safely. This encapsulation ensures that sensitive data is transmitted without interference or interception from unauthorized users, maintaining confidentiality and integrity.

Tunneling protocols include various implementations like PPTP, L2TP, IPsec, and SSL/TLS, each providing different levels of encryption and security features. This makes them essential for organizations and users wanting to securely connect to remote networks, allowing secure access to internal resources without exposing them to broader internet vulnerabilities. The reliance on tunneling protocols for security and data integrity is what primarily defines the functionality of a VPN.