L2TP features

Flexible identity authentication mechanism and high security—L2TP by itself does not provide security for connections. However, it has all the security features of PPP and allows for PPP authentication (CHAP or PAP). L2TP can also cooperate with IPsec to guarantee data security, strengthening the resistance of tunneled data to attacks. Tunnel encryption, end-to-end data encryption, and end-to-end application-layer data encryption technologies can be used together with L2TP for higher data security as required.

Multiprotocol transmission—L2TP tunnels PPP frames, which can be used to encapsulate packets of multiple network layer protocols.

RADIUS authentication—An LAC and LNS can send the username and password of a remote user to a RADIUS server for authentication.

Private address allocation—An LNS can reside behind the firewall of a corporate network and dynamically allocates private addresses to remote users, facilitating corporate private address management (RFC 1918) and improving the security.

Accounting flexibility—Accounting can be simultaneously carried out on the LAC and LNS, allowing bills to be generated on the ISP side and charging and auditing to be processed on the enterprise gateway. The L2TP can provide accounting data, such as inbound and outbound traffic statistics (in packets and bytes) and the connection's start time and end time. These features enable flexible accounting.

Reliability—L2TP supports LNS backup. When the connection to the primary LNS is torn down, an LAC can establish a new one to a secondary LNS. This redundancy enhances the reliability and fault tolerance of VPN services.