Virtual Private Networks

A VPN is a virtual private network. This is essentially a way to use the Internet to create a virtual connection between a remote user or site and a central location. The packets sent back and forth over this connection are encrypted, thus making it private. The VPN must emulate a direct network connection.

There are three different protocols that are used to create VPNs:

• Point-to-Point Tunneling Protocol (PPTP)

• Layer 2 Tunneling Protocol (L2TP)

• Internet Protocol Security (IPsec)

These are each discussed in more depth in the following sections.

PPTP

Point-to-Point Tunneling Protocol (PPTP) is the oldest of the three protocols used in VPNs. It was originally designed as a secure extension to Point-to-Point Protocol (PPP). PPTP was originally proposed as a standard in 1996 by the PPTP Forum—a group of companies that included Ascend Communications, ECI Telematics, Microsoft, 3Com, and U.S. Robotics. It adds the features of encrypting packets and authenticating users to the older PPP protocol. PPTP works at the data link layer of the OSI model (discussed in Chapter 2).