CISSP Study Guide: Point-to-Point Protocol (PPP)

Point-to-Point protocol (PPP) is used to implement TCP/IP over point-to-point connections. It has the basic function of encapsulating Network Layer (Layer 3) protocol information over point-to-point links. PPP uses its own framing method which allows encapsulation of any Layer 3 protocol. Because PPP uses a point-to-point structure, no mapping of protocol addresses is required. PPP utilizes the Link Control Protocol (LCP) to communicate between a PPP client and host.

LCP tests the link between client and PPP host and specifies PPP client configuration. PPP has several capabilities that makes it adaptable to various set-ups, including:

• Multiplexing of network layer protocols
• Link configuration
• Link quality testing
• Authentication
• Header compression
• Error detection
• Link parameter negotiation

For authentication, PPP has a number of options, including:

• Password Authentication Protocol (PAP)
• Shiva Password Authentication Protocol (SPAP)
• Challenge Handshake Authentication Protocol (CHAP)
• Extensible Authentication Protocol (EAP)

These two protocols offer varying levels of protection. Both require an established username and password. This can be done on the router or on a TACACS or RADIUS authentication server.