PPP Authentication Protocols: PAP and CHAP

PPP was designed to provide layer 2 connectivity over a variety of serial links and other physical layer technologies, some of which introduce more security concerns than others. For example, suppose you connect two machines in your office with a serial cable and want to run PPP between them. When one of these initiates a PPP link with the other, you don't really need to worry about who's calling. On the other hand, consider an Internet service provider (ISP) using PPP for remote dial-in users. They generally want to allow only their customers to connect.

The PPP protocol suite allows for the use of an optional authentication protocol when devices negotiate the basic link setup. The PPP suite initially ...

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