RFC 1464 (rfc1464) - Page 2 of 4
Using the Domain Name System To Store Arbitrary String Attributes
Alternative Format: Original Text Document
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