Overview

In this chapter we look at how MPLS can be used for supporting Virtual Private Networks (VPNs). There are several approaches for supporting VPNs that use MPLS. Even though these approaches all use MPLS, it is important to understand that MPLS is just one of the components within each approach; that is probably the only thing these approaches have in common. While in principle it may be desirable to cover all of these approaches, to do so at a useful level of detail would probably require an entire book. Therefore, we have chosen to describe one specific approach in detail rather than giving a superficial overview of all these approaches. Nevertheless, many of the general principles of MPLS VPNs will become clear in this chapter.

We begin by clarifying the meaning of VPN. The term has been widely used and abused, and there is a great deal of confusion as to what it really means. Following this, we examine traditional VPN solutions based on Frame Relay, ATM, or IP tunnels, and we discuss the problems that these solutions are unable to address. The rest of the chapter describes one particular MPLS-based VPN solution BGP/MPLS VPN. As the name suggests, this solution is based on a combination of two technologies, BGP and MPLS. We look at the components of the solution, including such areas as security and Quality of Service.

Note that although we have tried to describe the solution in considerable depth, not all the details are covered in...