Which VPN tunneling method requires that the client uses a VPN tunnel whenever connecting to an untrusted network?

The concept of an "Always-on VPN Tunnel" is that it mandates the client to maintain a VPN connection whenever it accesses any untrusted networks, which enhances security by ensuring that all data transmitted is encrypted and secure. This type of tunneling method is particularly important for users who frequently connect to public Wi-Fi or untrusted environments, as it minimizes the risk of data interception or unauthorized access to sensitive information.

With an Always-on VPN, the user does not have the option to alter their connection state; it is permanently established. This approach provides robust protection by ensuring that all internet traffic is routed through the secure VPN tunnel, effectively shielding the device from potential threats inherent in untrusted networks.

In contrast, the Full Tunnel method also secures all traffic but may not emphasize the necessity of having the VPN active at all times in the same way an Always-on VPN does. A Split Tunnel allows for direct connections to the internet while using a VPN for some traffic, which could expose the device when not using the VPN for all traffic. A Site-to-Site Tunnel connects entire networks rather than individual client devices and isn't typically relevant to individual user connections to untrusted networks.