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The Point-to-Point Protocol (PPP)
RFC 1661

Document type: RFC - Internet Standard (July 1994; Errata)
Updated by RFC 2153
Obsoletes RFC 1548
Document stream: IETF
Last updated: 2013-03-02
Other versions: plain text, pdf, html

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

IESG State: RFC 1661 (Internet Standard)
Responsible AD: (None)
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Network Working Group                                 W. Simpson, Editor
Request for Comments: 1661                                    Daydreamer
STD: 51                                                        July 1994
Obsoletes: 1548
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.

Table of Contents

     1.     Introduction ..........................................    1
        1.1       Specification of Requirements ...................    2
        1.2       Terminology .....................................    3

     2.     PPP Encapsulation .....................................    4

Simpson                                                         [Page i]

RFC 1661                Point-to-Point Protocol                July 1994

     3.     PPP Link Operation ....................................    6
        3.1       Overview ........................................    6
        3.2       Phase Diagram ...................................    6
        3.3       Link Dead (physical-layer not ready) ............    7
        3.4       Link Establishment Phase ........................    7
        3.5       Authentication Phase ............................    8
        3.6       Network-Layer Protocol Phase ....................    8
        3.7       Link Termination Phase ..........................    9

     4.     The Option Negotiation Automaton ......................   11
        4.1       State Transition Table ..........................   12
        4.2       States ..........................................   14
        4.3       Events ..........................................   16
        4.4       Actions .........................................   21
        4.5       Loop Avoidance ..................................   23
        4.6       Counters and Timers .............................   24

     5.     LCP Packet Formats ....................................   26
        5.1       Configure-Request ...............................   28
        5.2       Configure-Ack ...................................   29
        5.3       Configure-Nak ...................................   30
        5.4       Configure-Reject ................................   31
        5.5       Terminate-Request and Terminate-Ack .............   33
        5.6       Code-Reject .....................................   34
        5.7       Protocol-Reject .................................   35
        5.8       Echo-Request and Echo-Reply .....................   36
        5.9       Discard-Request .................................   37

     6.     LCP Configuration Options .............................   39
        6.1       Maximum-Receive-Unit (MRU) ......................   41
        6.2       Authentication-Protocol .........................   42
        6.3       Quality-Protocol ................................   43
        6.4       Magic-Number ....................................   45
        6.5       Protocol-Field-Compression (PFC) ................   48
        6.6       Address-and-Control-Field-Compression (ACFC)

     SECURITY CONSIDERATIONS ......................................   51
     REFERENCES ...................................................   51
     ACKNOWLEDGEMENTS .............................................   51
     CHAIR'S ADDRESS ..............................................   52
     EDITOR'S ADDRESS .............................................   52

Simpson                                                        [Page ii]

RFC 1661                Point-to-Point Protocol                July 1994

1.  Introduction

   The Point-to-Point Protocol is designed for simple links which

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