Chapter 7. Virtual Private Networks

A company with 1 main site and 10 remote sites could lease several different types of WAN services to connect the sites: leased lines, Frame Relay, or more likely today, Multiprotocol Label Switching (MPLS). However, another option for connecting remote sites is to simply connect each site to the Internet using some high-speed Internet access technology like cable or digital subscriber line (DSL). Then the sites can send IP packets to each other over the Internet, using the Internet as a WAN.

Unfortunately, the Internet is not nearly as secure as leased lines and other WAN options. For example, for an attacker to steal a copy of data frames passing over a leased line, the attacker would have to physically tap ...

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