What is Layer 2 Tunneling Protocol (L2TP)?
Layer 2 Tunneling Protocol (L2TP) is a computer network protocol used by Internet Service Providers (ISPs) to enable virtual private network (VPN) operations. L2TP is similar to the Data Link Layer Protocol in the OSI reference model, but is a session layer protocol.
A User Datagram Protocol (UDP) port is used for L2TP communication. Since it does not provide security for data such as encryption and confidentiality, an encryption protocol such as Internet Protocol Security (IPsec) with L2TP is often used.
This term is also known as Virtual Dialup Protocol.
Officially published in 1999, L2TP is an extension of the Point-to-Point Tunneling Protocol (PPTP). It is the amalgamation of two protocols, one from Microsoft (PPTP) and one from Cisco. L2TP stores the dial-in cost and overhead for each user trying to connect remotely to a site office. L2TP is known as Virtual Dialup Protocol over the Internet because of its PPP (Point-to-Point Protocol) extension service.
For example, suppose a user in New York is connected to a traditional dial-up modem and wants to communicate with someone in Sydney. To do this, the user receives a connection and establishes a dedicated connection from New York to Sydney. This dedicated dial-up connection uses a public switched telephone network (PSTN) and provides the lowest data transfer speed due to shared PSTN media. Thousands of other users are using the same medium, giving the user an overall speed of 33 Kbps or worse.
Instead, the user could use L2TP, with PPP used and configured at both ends (the ISP and the user site). After successful authentication of a user request, a tunnel for user data is created. When the tunnel is created, the user is open to start communication.
Advantages of L2TP are:
A high level of data security is provided for critical applications.
High-level encryption is used so that important information is always safe and personal.
It offers excellent and efficient connectivity.
It's inexpensive and once implemented, it doesn't have any Overhead.
It's reliable, scalable, fast, and flexible.
It is an industry standard for the corporate sector.
It has the best authorization policy for users with VPN authentication.