RFC 2136 (rfc2136) - Page 2 of 26

Dynamic Updates in the Domain Name System (DNS UPDATE)

Alternative Format: Original Text Document
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RFC 2136                       DNS Update                     April 1997


      Master          an authoritative server configured to be the
                      source of AXFR or IXFR data for one or more slave
                      servers.

      Primary Master  master server at the root of the AXFR/IXFR
                      dependency graph.  The primary master is named in
                      the zone's SOA MNAME field and optionally by an NS
                      RR.  There is by definition only one primary master
                      server per zone.

   A domain name identifies a node within the domain name space tree
   structure.  Each node has a set (possibly empty) of Resource Records
   (RRs).  All RRs having the same NAME, CLASS and TYPE are called a
   Resource Record Set (RRset).

   The pseudocode used in this document is for example purposes only.
   If it is found to disagree with the text, the text shall be
   considered authoritative.  If the text is found to be ambiguous, the
   pseudocode can be used to help resolve the ambiguity.

   1.1 - Comparison Rules

   1.1.1. Two RRs are considered equal if their NAME, CLASS, TYPE,
   RDLENGTH and RDATA fields are equal.  Note that the time-to-live
   (TTL) field is explicitly excluded from the comparison.

   1.1.2. The rules for comparison of character strings in names are
   specified in [RFC 1035 2.3.3].

   1.1.3. Wildcarding is disabled.  That is, a wildcard ("*") in an
   update only matches a wildcard ("*") in the zone, and vice versa.

   1.1.4. Aliasing is disabled: A CNAME in the zone matches a CNAME in
   the update, and will not otherwise be followed.  All UPDATE
   operations are done on the basis of canonical names.

   1.1.5. The following RR types cannot be appended to an RRset.  If the
   following comparison rules are met, then an attempt to add the new RR
   will result in the replacement of the previous RR:

      SOA    compare only NAME, CLASS and TYPE -- it is not possible to
             have more than one SOA per zone, even if any of the data
             fields differ.

      WKS    compare only NAME, CLASS, TYPE, ADDRESS, and PROTOCOL
             -- only one WKS RR is possible for this tuple, even if the
             services masks differ.




Vixie, et. al.              Standards Track
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