Which protocol provides a standard method for transporting multiprotocol datagrams over point-to-point links?

Point-to-Point Protocol (PPP) is the correct answer because it is specifically designed to encapsulate various network protocols in a point-to-point link configuration. This means it can transport datagrams or packets from multiple higher-layer protocols (such as IP, IPX, or AppleTalk) over a direct connection between two network nodes.

PPP provides essential features such as encapsulation of network layer packets, error detection, link quality monitoring, and authentication mechanisms, which are vital for ensuring reliable communication in point-to-point links. It can also support both synchronous and asynchronous connections, making it versatile for various networking scenarios.

Other options do not perform the same function. Layer Two Tunneling Protocol (L2TP) is primarily used for creating virtual private networks (VPNs) and does not function as a general-purpose transport protocol for multiprotocol datagrams like PPP does. Internet Protocol (IP) focuses on routing packets across networks rather than providing standardized means for transport over point-to-point links. Transmission Control Protocol (TCP) is a transport layer protocol that ensures reliable transmission of streams of data but operates over IP for end-to-end communication rather than specifically addressing point-to-point encapsulation.