L2TP (Layer 2 Tunneling Protocol) is a network protocol used to support the creation of virtual private networks (VPN). Its primary function is to allow data to be transmitted from one device to another over a public network (such as the Internet) securely, acting as if it were connected by a private network.

What distinguishes L2TP is that it operates at layer 2 of the OSI Model (Data Link Layer), which means that it can be used for different types of transport media such as IP, Frame Relay or ATM.

One of the notable features of L2TP is that it does not provide encryption by itself. Therefore, it is often combined with IPsec (Internet Protocol Security), which does offer encryption, to form L2TP/IPsec.

This combination provides data transport security, including features such as encryption, data origin authentication, and replay protection. L2TP/IPsec is widely used by businesses and VPN services to provide secure remote access to corporate networks and to protect data communication on insecure networks such as the Internet.

Common uses of L2TP/IPsec include:

• Site-to-site VPN connections: Securely connect two networks over the Internet, allowing resources on one network to be accessible to users on the other network as if they were a unified local network.
• Remote access: Allow remote employees or users to connect to your company network securely from anywhere, providing a secure tunnel through which they can access applications, files and resources as if they were physically in the office.

Key features:

• Compatibility: L2TP supports a wide range of devices and operating systems, making it easy to deploy in heterogeneous environments.
• Security: Although L2TP alone does not encrypt data, the combination of L2TP with IPsec provides a high level of security for communications over public networks.
• Flexibility: It can carry traffic from multiple protocols, making it useful in a variety of network scenarios.

In summary, L2TP connections, especially when combined with IPsec, offer a robust and secure solution to create virtual private networks on the infrastructure of a public network, guaranteeing the security and privacy of the data transmitted.