Network Control Program (NCP)

Network Control Protocol (NCP) was an early protocol implemented by ARPANET, the world's first operational packet-switching network that later evolved into what became the Internet. NCP allowed users to access and use computers and devices at remote locations and to transmit files between computers. NCP provided the middle layer of the protocol stack, and enabled application services such as email and file transfer. Whether the term is Network Control Protocol or Network Control Program is a matter of some debate, as both terms are used to refer to this ARPANET protocol.

Network Control Protocol (NCP) is a set of protocols forming a part of Point − to − Point Protocol (PPP). PPP is a data link layer protocol that is used to transmit multiprotocol data between two directly connected (point-to-point) computers. PPP is composed of link control protocol (LCP), authentication protocol (AP) and network control protocol (NCP). NCPs are used for negotiating the parameters and facilities for the network layer. For every higher-layer protocol supported by PPP, one NCP is there. The following diagram illustrates the layer in which NCPs operate:

source: Tutorials Point