In networking, the Point-to-Point Protocol, or PPP, is a data link protocol commonly used to establish a direct connection between two nodes over serial cable, phone line, trunk line, cellular telephone, specialized radio links, or fiber optic links. Most Internet service providers use PPP for customers' dial-up access to the Internet. Two common encapsulated forms of PPP, Point-to-Point Protocol over Ethernet (PPPoE) or Point-to-Point Protocol over ATM (PPPoA), are used in a similar role with Digital Subscriber Line (DSL) Internet service.
PPP is commonly used to act as a data link layer protocol for connection over synchronous and asynchronous circuits, where it has largely superseded the older, non-standard Serial Line Internet Protocol (SLIP), and telephone company mandated standards (such as Link Access Protocol, Balanced (LAPB) in the X.25 protocol suite). PPP was designed to work with numerous network layer protocols, including Internet Protocol (IP), Novell's Internetwork Packet Exchange (IPX), NBF and AppleTalk.
PPP Protocol Specification is RFC 1661.
Reference:
http://en.wikipedia.org/wiki/Point-to-Point_Protocol
