🚀 go-pugleaf

In article <862863270snx@ogham.org>, Giolla Decair  <Giolla@ogham.org> wrote:
>In article <336d1cf7.52504565@news.demon.co.uk>
>   peter@pmorton.demon.co.uk (Peter Morton) writes:
>> I'm trying to find the maximum length allowed for a domain name -
>> presuming there is one?  I'm suffering from RFC overload on this one
>> and although I expected it to be in the "Internet Encyclopedia",  a
>> few searches haven't revealed the information (and as it's a 7Meg file
>> I don't want to download it!).
>
>As far as I'm aware there isn't a maximum length, except that of 
>practicality, if it's too long who'd want to type it? A quick look
>through DNS and Bind, doesn't reveal any indication of a maximum allowable
>length either.

Actually I'm just reading the relevant chapter of "DNS and Bind" at the
moment (see page 290).  DNS query packets use a packed format for these
fields.  They contain a size byte for each element;  two bits are
allocated to flags, leaving 6 bits (i.e. 0 to 63) for the length of each
element.

The maximum overall length is defined (page 295) as MAXDNAME (including
the terminating zero byte).  MAXDNAME is defined in the arpa/nameser.h
header file:

#define MAXDNAME        256         /* maximum domain name */
#define MAXLABEL        63          /* maximum length of domain label */

-- 
John F Hall     jfhall@avondale.demon.co.uk    jfhall@compuserve.com
                jfhall@bcs.org.uk