What protocol does PPP use to identify the Network layer protocol?

The correct answer is the Network Control Protocol (NCP), which is used by Point-to-Point Protocol (PPP) to identify the Network layer protocol. In the context of PPP, NCP is responsible for establishing and configuring the link layer protocol to provide the necessary support for higher-layer protocols. The NCP allows multiple network layer protocols to be used over the same physical link by providing mechanisms to encapsulate and specify the network layer protocol being used, such as IP (Internet Protocol) or IPX (Internetwork Packet Exchange).

This is significant because PPP can support various network protocols, and NCP acts as a mediator that ensures they operate correctly over the established PPP link. By using NCP, the PPP protocol can dynamically negotiate which network-layer protocol to use during the connection setup phase, providing flexibility and compatibility with different network technologies. This capability is essential for environments where different protocols may need to coexist or switch dynamically.