Neighbor Discovery for IP Version 6 (IPv6)
RFC 1970

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Network Working Group                                          T. Narten
Request for Comments: 1970                                           IBM
Category: Standards Track                                    E. Nordmark
                                                        Sun Microsystems
                                                              W. Simpson
                                                              Daydreamer
                                                             August 1996

               Neighbor Discovery for IP Version 6 (IPv6)

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

   This document specifies the Neighbor Discovery protocol for IP
   Version 6.  IPv6 nodes on the same link use Neighbor Discovery to
   discover each other's presence, to determine each other's link-layer
   addresses, to find routers and to maintain reachability information
   about the paths to active neighbors.

Table of Contents

   1.  INTRODUCTION.............................................    3
   2.  TERMINOLOGY..............................................    4
      2.1.  General.............................................    4
      2.2.  Link Types..........................................    7
      2.3.  Addresses...........................................    8
      2.4.  Requirements........................................    9
   3.  PROTOCOL OVERVIEW........................................   10
      3.1.  Comparison with IPv4................................   14
      3.2.  Supported Link Types................................   16
   4.  MESSAGE FORMATS..........................................   17
      4.1.  Router Solicitation Message Format..................   17
      4.2.  Router Advertisement Message Format.................   18
      4.3.  Neighbor Solicitation Message Format................   21
      4.4.  Neighbor Advertisement Message Format...............   23
      4.5.  Redirect Message Format.............................   25
      4.6.  Option Formats......................................   27
         4.6.1.  Source/Target Link-layer Address...............   28
         4.6.2.  Prefix Information.............................   29
         4.6.3.  Redirected Header..............................   31

Narten, Nordmark & Simpson  Standards Track                     [Page 1]
RFC 1970       Neighbor Discovery for IP Version 6 (IPv6)    August 1996

         4.6.4.  MTU............................................   31
   5.  CONCEPTUAL MODEL OF A HOST...............................   32
      5.1.  Conceptual Data Structures..........................   33
      5.2.  Conceptual Sending Algorithm........................   35
      5.3.  Garbage Collection and Timeout Requirements.........   36
   6.  ROUTER AND PREFIX DISCOVERY..............................   37
      6.1.  Message Validation..................................   38
         6.1.1.  Validation of Router Solicitation Messages.....   38
         6.1.2.  Validation of Router Advertisement Messages....   38
      6.2.  Router Specification................................   39
         6.2.1.  Router Configuration Variables.................   39
         6.2.2.  Becoming An Advertising Interface..............   43
         6.2.3.  Router Advertisement Message Content...........   43
         6.2.4.  Sending Unsolicited Router Advertisements......   45
         6.2.5.  Ceasing To Be An Advertising Interface.........   45
         6.2.6.  Processing Router Solicitations................   46
         6.2.7.  Router Advertisement Consistency...............   47
         6.2.8.  Link-local Address Change......................   48
      6.3.  Host Specification..................................   48
         6.3.1.  Host Configuration Variables...................   48
         6.3.2.  Host Variables.................................   48
         6.3.3.  Interface Initialization.......................   50
         6.3.4.  Processing Received Router Advertisements......   50
         6.3.5.  Timing out Prefixes and Default Routers........   52
         6.3.6.  Default Router Selection.......................   53
         6.3.7.  Sending Router Solicitations...................   54
   7.  ADDRESS RESOLUTION AND NEIGHBOR UNREACHABILITY DETECTION.   55
      7.1.  Message Validation..................................   55
         7.1.1.  Validation of Neighbor Solicitations...........   55
         7.1.2.  Validation of Neighbor Advertisements..........   56
      7.2.  Address Resolution..................................   57
         7.2.1.  Interface Initialization.......................   57