Great Suggestion for the DNS problem...?

Mohacsi Janos mohacsi at
Tue Jul 29 14:32:18 UTC 2008

On Tue, 29 Jul 2008, Steven M. Bellovin wrote:

> On Tue, 29 Jul 2008 15:56:19 +0200
> Colin Alston <karnaugh at> 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?)

It was advocated as T/TCP in 90s.
Not accepted widely:
  		Janos Mohacsi

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