what's a valid domain name?

Barry Margolin barmar at alum.mit.edu
Sat Jan 29 04:20:15 UTC 2011

In article <mailman.1559.1296265826.555.bind-users at lists.isc.org>,
 pyh at mail.nsbeta.info wrote:

> I  googled and found this: 

It's on the Internet, so it must be true. :)

>     * A domain name can be up to 63 characters long plus a dot plus the 
> characters used to identify the top-level domain (i.e "com", "info", "biz", 
> etc.
>     * Valid characters in a domain name include letters, numbers and 
> hyphens "-". The domain name must start and end with a letter or number. 
> So, for this domain name of   
> "www.xyxyxyxyxyxyxyxyxyxyxyxyxyxyxyxyxyxyxyxyxyxyxyxyxyxyxyxyxyxyxyxy.com" 
> whose size is larger than 64, is not a valid domain name? 
> And is there a RFC item for a valid domain name? 

RFC 1035 section 3.1 says: "To simplify implementations, the total 
length of a domain name (i.e., label octets and label length octets) is 
restricted to 255 octets or less."

The length of each label within a domain name is limited to 63 

Barry Margolin, barmar at alum.mit.edu
Arlington, MA
*** PLEASE don't copy me on replies, I'll read them in the group ***

More information about the bind-users mailing list