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The Point-to-Point Protocol (PPP)
RFC 1548

Document type: RFC - Draft Standard (December 1993)
Obsoleted by RFC 1661
Updated by RFC 1570
Obsoletes RFC 1331
Document stream: IETF
Last updated: 2013-03-02
Other versions: plain text, pdf, html

IETF State: (None)
Document shepherd: No shepherd assigned

IESG State: RFC 1548 (Draft Standard)
Responsible AD: (None)
Send notices to: No addresses provided

Network Working Group                                         W. Simpson
Request for Comments: 1548                                    Daydreamer
Obsoletes: RFC 1331                                        December 1993
Category: Standards Track

                   The Point-to-Point Protocol (PPP)

Status of this Memo

   This document specifies an Internet standards track protocol for the
   Internet community, and requests discussion and suggestions for
   improvements.  Please refer to the current edition of the "Internet
   Official Protocol Standards" (STD 1) for the standardization state
   and status of this protocol.  Distribution of this memo is unlimited.

Abstract

   The Point-to-Point Protocol (PPP) provides a standard method for
   transporting multi-protocol datagrams over point-to-point links.  PPP
   is comprised of three main components:

      1. A method for encapsulating multi-protocol datagrams.

      2. A Link Control Protocol (LCP) for establishing, configuring,
         and testing the data-link connection.

      3. A family of Network Control Protocols (NCPs) for establishing
         and configuring different network-layer protocols.

   This document defines the PPP organization and methodology, and the
   PPP encapsulation, together with an extensible option negotiation
   mechanism which is able to negotiate a rich assortment of
   configuration parameters and provides additional management
   functions.  The PPP Link Control Protocol (LCP) is described in terms
   of this mechanism.

   This document is the product of the Point-to-Point Protocol Working
   Group of the Internet Engineering Task Force (IETF).  Comments should
   be submitted to the ietf-ppp@ucdavis.edu mailing list.

Simpson                                                         [Page 1]
RFC 1548              The Point-to-Point Protocol          December 1993

Table of Contents

   1.   Introduction ................................................3
   1.1  Specification of Requirements ...............................4
   1.2  Terminology .................................................5
   2.   PPP Encapsulation ...........................................5
   3.   PPP Link Operation ..........................................8
   3.1  Overview ....................................................8
   3.2  Phase Diagram ...............................................8
   3.3  Link Dead (physical-layer not ready) ........................9
   3.4  Link Establishment Phase ....................................9
   3.5  Authentication Phase ........................................9
   3.6  Network-Layer Protocol Phase ................................10
   3.7  Link Termination Phase ......................................10
   4.   The Option Negotiation Automaton ............................11
   4.1  State Diagram ...............................................12
   4.2  State Transition Table ......................................14
   4.3  A Day in the Life ...........................................15
   4.4  States ......................................................16
   4.5  Events ......................................................19
   4.6  Actions .....................................................23
   4.7  Loop Avoidance ..............................................26
   4.8  Counters and Timers .........................................26
   5.   LCP Packet Formats ..........................................27
   5.1  Configure-Request ...........................................29
   5.2  Configure-Ack ...............................................30
   5.3  Configure-Nak ...............................................31
   5.4  Configure-Reject ............................................33
   5.5  Terminate-Request and Terminate-Ack .........................34
   5.6  Code-Reject .................................................35
   5.7  Protocol-Reject .............................................36
   5.8  Echo-Request and Echo-Reply .................................37
   5.9  Discard-Request .............................................39
   6.   LCP Configuration Options ...................................40
   6.1  Maximum-Receive-Unit ........................................41
   6.2  Async-Control-Character-Map .................................42
   6.3  Authentication-Protocol .....................................43
   6.4  Quality-Protocol ............................................45
   6.5  Magic-Number ................................................46
   6.6  Protocol-Field-Compression ..................................49
   6.7  Address-and-Control-Field-Compression .......................50
   APPENDIX A. LCP Recommended Options ..............................51
   SECURITY CONSIDERATIONS ..........................................51
   REFERENCES .......................................................52

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