What PPP protocol provides dynamic addressing, authentication, and multilink?

The correct answer is the Link Control Protocol (LCP), which is part of the Point-to-Point Protocol (PPP). LCP is responsible for establishing, configuring, and testing the data-link connection, allowing for dynamic addressing and authentication processes.

Dynamic addressing allows devices to obtain their IP addresses automatically, enhancing flexibility in network configurations. Additionally, LCP supports authentication protocols that verify the identity of the connecting devices, ensuring secure communication over the link. Furthermore, the multilink feature permits the aggregation of multiple physical connections into a single logical connection, which can help increase bandwidth and provide redundancy.

Other protocols mentioned, such as NCP, HDLC, and X.25, do not provide the same combination of features as LCP in the context of PPP. For example, NCP (Network Control Protocol) is primarily responsible for establishing and configuring network-layer protocols on a PPP link but does not handle the physical link setup itself. HDLC is a data link layer protocol but lacks dynamic addressing capabilities, and X.25 is an older standard for packet-switched networks, which operates quite differently from PPP's more flexible architecture.