Final answer:
The protocol within PPP that sets up the PPP connection and defines communication parameters and authentication is the Link Control Protocol (LCP). It establishes, configures, and tests the data link connection between two PPP devices.
Step-by-step explanation:
The protocol within PPP that sets up the PPP connection and defines communication parameters and authentication is the Link Control Protocol (LCP).
LCP is responsible for establishing, configuring, and testing the data link connection between two PPP devices. It negotiates and agrees upon the authentication method to be used and other communication parameters such as maximum transmission unit (MTU), compression options, and error detection methods.
For example, LCP can negotiate the use of Password Authentication Protocol (PAP) or Challenge Handshake Authentication Protocol (CHAP) for authentication purposes. It also ensures that both ends of the connection agree on the specific parameters to be used during the PPP session.