RFC 2181 (rfc2181) - Page 2 of 15

Clarifications to the DNS Specification

RFC 2181        Clarifications to the DNS Specification        July 1997




Contents

    1  Abstract  ...................................................   1
    2  Introduction  ...............................................   2
    3  Terminology  ................................................   3
    4  Server Reply Source Address Selection  ......................   3
    5  Resource Record Sets  .......................................   4
    6  Zone Cuts  ..................................................   8
    7  SOA RRs  ....................................................  10
    8  Time to Live (TTL)  .........................................  10
    9  The TC (truncated) header bit  ..............................  11
   10  Naming issues  ..............................................  11
   11  Name syntax  ................................................  13
   12  Security Considerations  ....................................  14
   13  References  .................................................  14
   14  Acknowledgements  ...........................................  15
   15  Authors' Addresses  .........................................  15




2. Introduction

   Several problem areas in the Domain Name System specification
   [RFC 1034, RFC 1035] have been noted through the years [RFC 1123].  This
   document addresses several additional problem areas.  The issues here
   are independent.  Those issues are the question of which source
   address a multi-homed DNS server should use when replying to a query,
   the issue of differing TTLs for DNS records with the same label,
   class and type, and the issue of canonical names, what they are, how
   CNAME records relate, what names are legal in what parts of the DNS,
   and what is the valid syntax of a DNS name.

   Clarifications to the DNS specification to avoid these problems are
   made in this memo.  A minor ambiguity in RFC 1034 concerned with SOA
   records is also corrected, as is one in the definition of the TTL
   (Time To Live) and some possible confusion in use of the TC bit.












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