Information, Computer and Network Security Terms Glossary and Dictionary

L2TP / PPTP Virtual Private Network (VPN)

The Layer 2 Tunneling Protocol (L2TP), an IETF standard based on the Mirosoft Point to Point Tunneling Protocol (PPTP) and the Cisco Layer 2 Forward protocol (L 2F ), provides remote users encrypted, multi-protocol dial up access to a corporate network over the Internet. PPTP and L2TP are the layer 2 VPN technologies from CPE (customer premise equipment) to CPE.

L2TP and PPTP are extension s to the Point-to-Point Protocol (PPP) . Network layer (Layer 3) protocols, such as IP and IPX, are encapsulated by the L2TP/ PPTP for transport over the Internet. However, PPTP can support only one tunnel at a time for each user. Therefore, its proposed successor, L2TP can support multiple, simultaneous tunnels for each user. In addition, L2TP supports multiple protocols and unregistered and privately administered IP addresses over the Internet. This allows the existing access inf r astructure, such as the Internet, modems, access servers, and ISDN terminal adapters (TAs), to be used. It also allows enterprise customers to outsource dialout support, thus reducing overhead for hardware maintenance costs and 800 number fees, and allows them to concentrate corporate gateway resources.

PPTP is vulnerable to man-in-the-middle attacks related to data integrity and data origination, but the biggest problem is that it supports only single-factor, password-based authentication. As a result, if an intruder steals or guesses an employee's password, that intruder can access your company's network. Security mechanisms are improved in the L2TP VPN. Two types of mutual authentication are supported for use with L2TP: Certificate Authority and Preshared Key. Authentication protocols supported in L2TP including PAP, CHAP, MS-CHAP v1 and v2, etc.

For information privacy, L2TP VPN support many encryption algorithms such as: Triple DES (3DES) encryption and RSA RC4 algorithm, etc.

Related Terms

Tunneling, IPsec, SSL, TLS, PPTP, L2TP, L2F , SOCKS 5, Encryption, Encapsulation , MPLS VPN, IPsec VPN, SSL VPN