What are some common tunneling protocols?

The most popular tunneling protocols for VPNs are the Point-to-Point Tunneling Protocol (PPTP), Internet Protocol Security (IPSec), and Layer 2 Tunneling Protocol (L2TP), which combines PPTP and Cisco Systems' Layer-2 Forwarding (L2F). SOCKS 5 is yet another approach, which follows a proxy server model, and is considered among the most secure. Companies with very low security requirements may consider other alternatives, such as Secure Shell (SSH).