ICMP Domain Name Messages
RFC 1788

Document Type RFC - Historic (April 1995; No errata)
Obsoleted by RFC 6918
Last updated 2013-05-24
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Network Working Group                                         W. Simpson
Request for Comments: 1788                                    Daydreamer
Category: Experimental                                        April 1995

                       ICMP Domain Name Messages

Status of this Memo

   This document defines an Experimental Protocol for the Internet
   community.  This does not specify an Internet standard of any kind.
   Discussion and suggestions for improvement are requested.
   Distribution of this memo is unlimited.

IESG Note:

   An Internet Engineering Steering Group comment from the co-Area
   Director for IPng:  Please note well that this memo is an individual
   product of the author.  It presents one view of the IN-ADDR
   mechanism, motivated by discussion in the IPNG WG of the difficulty
   of secure, dynamic update of the reverse tree.  Other IETF discussion
   and ongoing standards work on this area will be found in the IP Next
   Generation (ipngwg), DNS IXFR, Notification, and Dynamic Update
   (dnsind), DNS Security (dnssec) working groups.

Abstract

   This document specifies ICMP messages for learning the Fully
   Qualified Domain Name associated with an IP address.

Simpson                                                         [Page 1]
RFC 1788                    ICMP Domain Name                  April 1995

Table of Contents

     1.     Introduction ..........................................    2
        1.1       Direct Query ....................................    3
        1.2       Multicast .......................................    3
        1.3       Domain Names ....................................    3
        1.4       Messages ........................................    4

     2.     Domain Name Request ...................................    4

     3.     Domain Name Reply .....................................    5

     SECURITY CONSIDERATIONS ......................................    6
     REFERENCES ...................................................    6
     ACKNOWLEDGEMENTS .............................................    7
     AUTHOR'S ADDRESS .............................................    7

1.  Introduction

   The Domain Name System (DNS) is described in [RFC-1034].  The IN-ADDR
   domain of the DNS is specified [RFC-1035] to perform address to
   domain name resolution, and to facilitate queries to locate all
   gateways (routers) on a particular network in the Internet.

   Neither function has been remarkably successful.  The IN-ADDR domain
   is not reliably populated.

   As multiple routers were used at boundaries and within networks, the
   IN-ADDR mechanism was found to be inadequate.  The location of
   routers by hosts is now performed using "ICMP Router Discovery
   Messages" [RFC-1256].

   As network numbers migrated to "classless" routing and aggregation,
   the IN-ADDR delegation granularity has fragmented, and requires
   overlapping administration.  The "reverse" IN-ADDR administration
   frequently does not follow the same delegation as the "forward"
   domain name tree.  This structure is not amenable to cooperative
   secure updating of the DNS.

   As application servers have appeared which require the Domain Name
   for user interaction and security logging, the IN-ADDR servers have
   been inundated with queries.  This produces long user visible pauses
   at the initiation of sessions.

Simpson                                                         [Page 2]
RFC 1788                    ICMP Domain Name                  April 1995

1.1.  Direct Query

   This document proposes that each unicast address be queried directly
   for its corresponding Domain Name.  This has the advantages that the
   naming is under the same administration as the address assignment,
   and the queries are distributed in the same fashion as IP routing.
   In effect, the routing is used to index the database.

1.2.  Multicast

   Only a few well-known multicast addresses are populated in the IN-
   ADDR domain.  The ephemeral nature of most multicast addresses is not
   conducive to cooperative secure updating of the DNS.

   However, the technique described here is not useful for multicast
   addresses.  A query to a multicast address could result in a storm of
   replies.  Most multicast groups are not named, or the member nodes
   are not configured with the name.

   The IN-ADDR method SHOULD continue to be used for reverse lookup of
   well-known multicast addresses in the range 224.0.0.0 to
   224.0.255.255.  Other multicast addresses are an issue for futher
   study.

1.3.  Domain Names

   Each Domain Name is expressed as a sequence of labels.  Each label is
   represented as a one octet length field, followed by that number of
   octets.  Since every Domain Name ends with the null label of the
   root, a Domain Name is terminated by a length byte of zero.  The most
   significant two bits of every length octet must be '00', and the
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