RFC 1464 (rfc1464) - Page 2 of 4

Using the Domain Name System To Store Arbitrary String Attributes

RFC 1464          Storing Arbitrary Attributes in DNS           May 1993


   For example, the following TXT records contain attributes specified
   in this fashion:

        host.widgets.com   IN   TXT   "printer=lpr5"
        sam.widgets.com    IN   TXT   "favorite drink=orange juice"

   The general syntax is:

         TXT "="

   Attribute Names

   Any printable ASCII character is permitted for the attribute name.
   If an equals sign is embedded in the attribute name, it must be
   quoted with a preceding grave accent (or backquote: "`").  A
   backquote must also be quoted with an additional "`".

   Attribute Name Matching Rules

   The attribute name is considered case-insensitive.  For example, a
   lookup of the attribute "Favorite Drink" would match a TXT record
   containing "favorite drink=Earl Grey tea".

   During lookups, TXT records that do not contain an unquoted "=" are
   ignored.  TXT records that seem to contain a null attribute name,
   that is, the TXT-DATA starts with the character "=", are also
   ignored.

   Leading and trailing whitespace (spaces and tabs) in the attribute
   name are ignored unless they are quoted (with a "`").  For example,
   "abc" matches " abc" but does not match "` abc".

   Note that most DNS server implementations require a backslash (\) or
   double quote (") in a text string to be quoted with a preceding
   backslash.  Accent grave ("`") was chosen as a quoting character in
   this syntax to avoid confusion with "\" (and remove the need for
   confusing strings that include sequences like "\\\\").

   Attribute Values

   All printable ASCII characters are permitted in the attribute value.
   No characters need to be quoted with a "`".  In other words, the
   first unquoted equals sign in the TXT record is the name/value
   delimiter.  All subsequent characters are part of the value.

   Once again, note that in most implementations the backslash character
   is an active quoting character (and must, itself, be quoted).




Rosenbaum