A Network Control Protocol is a protocol that runs atop the Point-to-Point Protocol

Point-to-Point Protocol

In networking, the Point-to-Point Protocol is a data link protocol commonly used in establishing a direct connection between two networking nodes...

 (PPP) and that is used to negotiate options for a network layer

Network layer

The network layer is layer 3 of the seven-layer OSI model of computer networking.The network layer is responsible for packet forwarding including routing through intermediate routers, whereas the data link layer is responsible for media access control, flow control and error checking.The network...

 protocol running atop PPP. Network Control Protocols include the Internet Protocol Control Protocol

Internet Protocol Control Protocol

In computer networking, Internet Protocol Control Protocol is a network control protocol for establishing and configuring Internet Protocol over a Point-to-Point Protocol link. IPCP uses the same packet exchange mechanism as the Link Control Protocol...

 for the Internet Protocol

Internet Protocol

The Internet Protocol is the principal communications protocol used for relaying datagrams across an internetwork using the Internet Protocol Suite...

, the Internetwork Packet Exchange Control Protocol for the Internet Packet Exchange

IPX

Internetwork Packet Exchange is the OSI-model Network layer protocol in the IPX/SPX protocol stack.The IPX/SPXM protocol stack is supported by Novell's NetWare network operating system. Because of Netware's popularity through the late 1980s into the mid 1990s, IPX became a popular internetworking...

 protocol, and the AppleTalk Control Protocol for AppleTalk

AppleTalk

AppleTalk is a proprietary suite of protocols developed by Apple Inc. for networking computers. It was included in the original Macintosh released in 1984, but is now unsupported as of the release of Mac OS X v10.6 in 2009 in favor of TCP/IP networking...

.

This protocol operates on the Data Link layer