hostname limitation

[Mark.Andrews at nominum.com]

> Mark.Andrews at nominum.com wrote:
> > 
> > >
> > >
> > > Does anyone know what the limitation on hostnames are in DNS?
> > 
> >         Yes.
> > 
> > >  I need to know how many characters I can use for a hostname...
> > 
> >         This is an ambigious question.
> > 
> >         The DNS supports hostnames lengths up to 253 characters.
> >         This is less than the maximum of 255 specified by RFC 1123.
> 
> 	Not that I'm arguing with you, but this is a new one on me. Do you have
>  a
> reference for this? Or is it a limitation built into the software at some
> point that we have to propogate forward?
> 
> Inquiring minds, and all that...

	DNS wire format max is 255 octets.  Do the math.

	e.g.
	The hostname "example.com" is 11 characters long.  It's
	wire format is 1 + 7 + 1 + 3 + 1 = 13.  i.e. two octets of
	overhead.

	255 - 2 = 253

	NOTE: a hostname does not have a period at the end.

	Mark

> 
> Doug
> -- 
>     I need someone really bad. Are you really bad?
--
Mark Andrews, Nominum Inc.
1 Seymour St., Dundas Valley, NSW 2117, Australia
PHONE: +61 2 9871 4742                 INTERNET: Mark.Andrews at nominum.com