[106465] in North American Network Operators' Group
Re: Great Suggestion for the DNS problem...?
daemon@ATHENA.MIT.EDU (Steven M. Bellovin)
Tue Jul 29 10:23:30 2008
Date: Tue, 29 Jul 2008 10:23:02 -0400
From: "Steven M. Bellovin" <smb@cs.columbia.edu>
To: Colin Alston <karnaugh@karnaugh.za.net>
In-Reply-To: <488F2183.2020008@karnaugh.za.net>
Cc: nanog@nanog.org
Errors-To: nanog-bounces@nanog.org
On Tue, 29 Jul 2008 15:56:19 +0200
Colin Alston <karnaugh@karnaugh.za.net> wrote:
> > DNS uses UDP.
>
> Ahh yes of course..
>
> Why does it use UDP? :P
>
In this situation, UDP uses one query packet and one reply. TCP uses 3
to set up the connection, a query, a reply, and three to tear down the
connection. *Plus* the name server will have to keep state for
every client, plus TIMEWAIT state, etc. (Exercise left to TCP geek
readers: how few packets can you do this in? For example -- send the
query with the SYN+ACK, send client FIN with the query, send server FIN
with the answer? Bonus points for not leaving the server's side in
TIMEWAIT. Exercise for implementers: how sane can your stack be if
you're going to support that?)
--Steve Bellovin, http://www.cs.columbia.edu/~smb
