[council] RE: request for ICANN action on single letter domain names (now reserved names)

Bruce Tonkin Bruce.Tonkin at melbourneit.com.au
Wed Aug 17 23:31:38 UTC 2005

Hello All,

Just to refresh my memory, I checked a couple of the IETF standards on
this topic.

>From the  main DNS standard:
RFC 1035 Domain Implementation and Specification    November 1987
(http://www.ietf.org/rfc/rfc1035.txt )

"The DNS specifications attempt to be as general as possible in the
for constructing domain names.  The idea is that the name of any
existing object can be expressed as a domain name with minimal changes.

However, when assigning a domain name for an object, the prudent user
will select a name which satisfies both the rules of the domain system
and any existing rules for the object, whether these rules are published
or implied by existing programs.

For example, when naming a mail domain, the user should satisfy both the
rules of this memo and those in RFC-822.  When creating a new host name,
the old rules for HOSTS.TXT should be followed.  This avoids problems
when old software is converted to use domain names.


Note that while upper and lower case letters are allowed in domain
names, no significance is attached to the case.  That is, two names with
the same spelling but different case are to be treated as if identical."

So basically the DNS protocol itself can handle a range of labels, but
the applications of the DNS may have restrictions.   So the DNS protocol
can handle single letter domain names.

Prior to the DNS, most computers maintained host tables (ie tables of
computer names and their IP addresses) - effectively like a local phone
book as many of you might have in your mobile phone.

Thr rules for computer names (Host names) are defined in

"A "name" (Net, Host, Gateway, or Domain name) is a text string up
   to 24 characters drawn from the alphabet (A-Z), digits (0-9), minus
   sign (-), and period (.).  Note that periods are only allowed when
   they serve to delimit components of "domain style names". (See
   RFC-921, "Domain Name System Implementation Schedule", for
   background).  No blank or space characters are permitted as part of a
   name. No distinction is made between upper and lower case.  The first
   character must be an alpha character.  The last character must not be
   a minus sign or period.  A host which serves as a GATEWAY should have
   "-GATEWAY" or "-GW" as part of its name.  Hosts which do not serve as
   Internet gateways should not use "-GATEWAY" and "-GW" as part of
   their names. A host which is a TAC should have "-TAC" as the last
   part of its host name, if it is a DoD host.  Single character names
   or nicknames are not allowed."

Note the last sentence above.

So the question really comes down to deciding what the impact on
existing software would be to allow single letter domain names more

On a related topic I have also heard requests for additional punctuation
types such as the "&" sign, or "!" sign in domain names using the ASCII
character set.   Punctuation characters are used in company names (e.g
AT&T, Yahoo!,  , and it is now more common for domain names to relate to
company names  and brand names, than the type of names that were used to
label computers in the past.  Note these additional characters are
excluded from the hostname definition above.    As an aside, IDNs do
meet the hostname standard, as they are converted from the hostname
character set into different characters by end user software.   One of
the core debates when introducing internationalised domain names, was
whether to simple allow UNICODE characters to be represented in the DNS
labels directly.

Bruce Tonkin

Bruce Tonkin


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