layer 2 forwarding (VPN) (L2F)
The L2F protocol is a Layer 2 protocol for secure communication in Virtual Private Networks( VPN) via a Layer 2 tunnel connection, specifically for the integration of individual computers into a network.
Layer 2 Forwarding (L2F) is an initiative of Cisco, Nothern Telecom and Shiva and supports the IP protocol, Frame Relay and ATM. It is described in RFC 2341. L2F solves the addressing problem from the point of view of the Internet Service Provider. Here, L2F tunnels the link level of high-level protocols such as PPP and SLIP over the Internet. The initialization of the tunnels has to be done by the ISP. Unfortunately, L2F does not include encryption techniques, so this has to be solved otherwise.
The lack of flow control and the ability to establish outgoing connections to the remote terminal are also disadvantages. Operability is limited to a few manufacturers.