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Two schemes have been adopted by the Internet community to encapsulate and transmit IP (Internet Protocol) datagrams over serial point-to-point links: SLIP (Serial Line Interface Protocol) and PPP (Point-to-Point Protocol). SLIP is an earlier protocol that has fallen into disuse. PPP predominates because it works with other protocols such as IPX and was designed to overcome problems with the earlier protocol.

PPP is defined in RFC 1661 (The Point-to-Point Protocol, July 1994). RFC 1547 (Requirements for an Internet Standard Point-to-Point Protocol, December 1993) provides historical information about the need for PPP and its development. A series of related RFCs have been written to define how a variety of network control protocols-including TCP/IP, DECnet, AppleTalk, IPX, and others-work with PPP.