PPP Link Quality Monitoring
RFC 1333

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Network Working Group                                         W. Simpson
Request for Comments: 1333                                    Daydreamer
                                                                May 1992

                      PPP Link Quality Monitoring

Status of this Memo

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

Abstract

   The Point-to-Point Protocol (PPP) [1] provides a standard method of
   encapsulating Network Layer protocol information over point-to-point
   links.  PPP also defines an extensible Link Control Protocol, which
   allows negotiation of a Quality Protocol for continuous monitoring of
   the viability of the link.

   This document defines a protocol for generating Link-Quality-Reports.

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

Simpson                                                         [Page i]


RFC 1333              PPP Link Quality Monitoring               May 1992

Table of Contents

     1.     Introduction ..........................................    1

     2.     Link Quality Monitoring ...............................    2
        2.1       Design Motivation ...............................    2
        2.2       Counters ........................................    2
        2.3       Counting Packets and Octets .....................    4
        2.4       Processes .......................................    4
        2.5       Configuration Option Format .....................    6
        2.6       Packet Format ...................................    8
        2.7       Transmission of Reports .........................   12
        2.8       Calculations ....................................   12
        2.9       Failure Detection ...............................   13
        2.10      Policy Suggestions ..............................   14

     SECURITY CONSIDERATIONS ......................................   14

     REFERENCES ...................................................   14

     ACKNOWLEDGEMENTS .............................................   14

     CHAIR'S ADDRESS ..............................................   15

     AUTHOR'S ADDRESS .............................................   15

Simpson                                                        [Page ii]


RFC 1333              PPP Link Quality Monitoring               May 1992

1.  Introduction

   PPP has three main components:

      1. A method for encapsulating datagrams over serial links.

      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.

   In order to establish communications over a point-to-point link, each
   end of the PPP link must first send LCP packets to configure the data
   link during the Establishment phase.  During the Authentication and
   Network-Layer Protocol phases, the link may be tested to determine if
   quality is sufficient for operation.  This testing is completely
   optional.

   If an implementation desires that the peer use some specific link
   quality monitoring protocol, then it MUST negotiate the use of that
   protocol using the Quality-Protocol Configuration Option during Link
   Establishment phase.

   The negotiation mechanism is independent in each direction.  However,
   if the peer agrees to send Quality-Protocol packets, it MUST
   correctly process such packets on reception, even if it does not
   request such packets or implement a monitoring policy.

Simpson                                                         [Page 1]
RFC 1333              PPP Link Quality Monitoring               May 1992

2.  Link Quality Monitoring

   Data communications links are rarely perfect.  Packets can be dropped
   or corrupted for various reasons (line noise, equipment failure,
   buffer overruns, etc.).  Sometimes, it is desirable to determine
   when, and how often, the link is dropping data.  Routers, for
   example, may want to temporarily allow another route to take
   precedence.  An implementation may also have the option of
   disconnecting and switching to an alternate link.  The process of
   determining data loss is called "Link Quality Monitoring".

2.1.  Design Motivation

   There are many different ways to measure link quality, and even more
   ways to react to it.  Rather than specifying a single scheme, Link
   Quality Monitoring is divided into a "mechanism" and a "policy".  PPP