What is L2TP Protocol?

By Paul Liu
Monday, January 7th, 2013

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What is the L2TP Protocol? How do I use it, and how is it different from other VPN protocols?

Layer 2 Tunneling Protocol (L2TP) is an advanced networking protocol used to implement virtual private networks (VPN). It is one of the most secure and versatile protocols available that works on a majority of computer systems and mobile platforms. The L2TP protocol is also used by internet service providers (ISP) to deliver their services in special cases, for instance when the cable or ADSL is being resold. L2TP is also recommended as a replacement for networks using the less secure PPTP protocol where additional encryption and security is required. Below we check out the most important features offered by the L2TP protocol along with their pros and cons.

History – The L2TP protocol was first proposed in 1999. The protocol is derived from two existing protocols; Layer 2 Forwarding Protocol (L2F) which was created by CICSO and Point-to-Point Tunneling Protocol (PPTP) which was developed by USRobotics. In 2005, a new version of the protocol (L2TPv3) was proposed which provided additional security and encapsulation features and ability to carry data over many more types of networks. Just like PPTP, L2TP doesn’t include privacy and encryption features; instead it relies on encryption features provided by tunneling protocols to provide the security.

System Support – The L2TP protocol enjoys industry wide support. Microsoft offers in-built support for L2TP since the launch of Windows 2000 and XP. Most Linux and UNIX implementations as well as Mac OSX offer support for the protocol. A lot of mobile platforms such as iOS and Android have built-in L2TP clients.

Encryption – L2TP is often used in conjunction with the IPSec protocol which provides encryption, authentication and integrity to the network; the combination is referred to as L2TP/IPSec in the technology landscape. In L2TP/IPSec, the packets are encrypted with IPSec protocol which uses advanced 3DES or AES algorithms for encryption and authentication. Most VPN providers use 256 bit keys for encryption to deliver a safe and secure networking environment to their users.

Configuration – L2TP is easier to set up than its competitors. Since most platforms come with inbuilt support of L2TP, installation and configuration is quick and easy.

Speed – L2TP encapsulates its data twice which slows down the entire data transfer process and makes it slower and less efficient than its competitors. However the speed difference is barely noticeable over fast networks so a majority of VPN providers provide support for L2TP in addition to OpenVPN.

Port – L2TP uses several protocols for its operation. For instance, the L2TP/IPSec combination uses UDP 500 for key exchange, UDP 1701 for configuration and UDP 4500 for traversal. Since it uses fixed ports and protocols, it is easier to block L2TP than OpenVPN.

Stability – L2TP is known to be a stable and reliable VPN protocol. However it is slightly difficult to manage and configure when used with devices that are connected to NAT routers. The configuration and stability issues can be resolved by using both clients and servers that support NAT traversal.

Security Issues – L2TP is known to be extremely secure since it doesn’t have any major exploit or vulnerability. It is best to use L2TP with a tunneling protocol that uses advanced encryption and security algorithms such as AES for maximum security.

Conclusion – L2TP is an excellent VPN protocol that delivers the goods. While it falls just short of OpenVPN, it is quick to setup, provides excellent security and supports a wide variety of devices which makes it an great choice for use in most environments.

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January 7, 2013

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