RFC 1134 (rfc1134) - Page 3 of 38
Point-to-Point Protocol: A proposal for multi-protocol transmission of datagrams over Point-to-Point links
Alternative Format: Original Text Document
RFC 1134 PPP November 1989 every host supports point-to-point connections. For example, asynchronous RS-232-C [1] interfaces are essentially ubiquitous. One reason for the small number of point-to-point IP links is the lack of a standard encapsulation protocol. There are plenty of non- standard (and at least one defacto standard) encapsulation protocols available, but there is not one which has been agreed upon as an Internet Standard. By contrast, standard encapsulation schemes do exist for the transmission of datagrams over most popular LANs. One purpose of this memo is to remedy this problem. But even more importantly, the Point-to-Point Protocol proposes more than just an encapsulation scheme. Point-to-Point links tend to exacerbate many problems with the current family of network protocols. For instance, assignment and management of IP addresses, which is a problem even in LAN environments, is especially difficult over switched point-to- point circuits (e.g., dialups). Some additional issues addressed by PPP include asynchronous (start/stop) and bit-oriented synchronous encapsulation, network protocol multiplexing, link configuration, link quality testing, error detection, and option negotiation for such capabilities as network-layer address negotiation and data compression negotiation. PPP addresses these issues by providing an extensible Link Control Protocol (LCP) and a family of Network Control Protocols (NCP) to negotiate optional configuration parameters and facilities. 1.2. Overview of PPP PPP has three main components: 1. A method for encapsulating datagrams over serial links. PPP uses HDLC as a basis for encapsulating datagrams over point- to-point links. 2. An extensible Link Control Protocol (LCP) to establish, configure, and test the data-link connection. 3. A family of Network Control Protocols (NCP) for establishing and configuring different network-layer protocols. PPP is designed to allow the simultaneous use of multiple network- layer protocols. In order to establish communications over a point-to-point link, the originating PPP would first send LCP packets to configure and test the data link. After the link has been establish and optional facilities have been negotiated as needed by the LCP, the originating Perkins
