RFC 1171 (rfc1171) - Page 2 of 48

Point-to-Point Protocol for the transmission of multi-protocol datagrams over Point-to-Point links

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RFC 1171                Point-to-Point Protocol                July 1990


         asynchronous or synchronous duplex circuits, either dedicated
         or circuit switched.

      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
   PPP would send NCP packets to choose and configure one or more
   network-layer protocols.  Once each of the chosen network-layer
   protocols has been configured, datagrams from each network-layer
   protocol can be sent over the link.

   The link will remain configured for communications until explicit LCP
   or NCP packets close the link down, or until some external event
   occurs (e.g., inactivity timer expires or user intervention).


1.3.  Organization of the document

   This memo is divided into several sections.  Section 2 discusses the
   physical-layer requirements of PPP.  Section 3 describes the Data
   Link Layer including the PPP frame format and data link encapsulation
   scheme.  Section 4 specifies the LCP including the connection
   establishment and option negotiation procedures.  Section 5 specifies
   the IP Control Protocol (IPCP), which is the NCP for the Internet
   Protocol, and describes the encapsulation of IP datagrams within PPP
   packets.  Appendix A summarizes important features of asynchronous
   HDLC, and Appendix B describes an efficient table-lookup algorithm
   for fast Frame Check Sequence (FCS) computation.














Perkins
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