Network Control Protocol

This article is about (1) protocols running atop the Point-to-Point Protocol for negotiating network layer protocol options and about (2) clarifying the early NCP Transport Layer protocol. For the ARPANET NCP, see Network Control Program.

(1) A Network Control Protocol is a protocol that runs atop the Point-to-Point Protocol (PPP) and that is used to negotiate options for a network layer protocol running atop PPP. Network Control Protocols include the Internet Protocol Control Protocol for the Internet Protocol, the Internetwork Packet Exchange Control Protocol for the Internet Packet Exchange protocol, and the AppleTalk Control Protocol for AppleTalk.

This protocol operates on the Network link layer.

http://tools.ietf.org/html/rfc1332

(2) Please note, that in the world of Information Technology and Networking, a single term, or acronym, may very well have more then one totally different meaning, use, developer, designer, or function. Or may have mistaken interpretations. The Network Control Program is sometimes mistakenly referred to as the Network Control Protocol, as in this reference below. This information is on this wikipedia page to help educate those who are still not sure about NCP in reference to the ARPANET or port numbers. The earliest RFC reference to the NCP acronym, explicitly defines NCP as Network Control Program. http://tools.ietf.org/html/rfc33 Page 4.

Some references, such as the one below, mistakenly refer to NCP as Network Control Protocol.

The Network Control Protocol (NCP) preceded the Transmission Control Protocol (TCP) as a Transport Layer protocol used during the early ARPANET. NCP was a simplex protocol that utilized two port addresses, establishing two connections, for two way communications. An odd and an even port was reserved for each Application Layer application or protocol. The standardization of TCP and UDP, reduced the need for the use of two simplex ports for each application down to one duplex port.

Reference: Steven, W Richard. TCP/IP Illustrated Volume I. Reading, Massachusetts, USA: Addison-Wesley Publishing Company, 1994. ISBN 0-201-63346-9(v.1). Page 15.