Usage of TCP/53

Dan Mahoney, System Admin danm at
Thu Sep 28 19:10:46 UTC 2006

On Thu, 28 Sep 2006, Peter Dambier wrote:

As an aside, I really wish certain other protocols worked like this (SNMP, 
specifically).  I notice the services file for my OS has TCP/UDP entries 
for a LOT of things that will NEVER use UDP -- anyone have any idea why?


> Ralf Durkee wrote:
>> I have a question about usage of the TCP port 53 by DNS servers in
>> general, and BIND in particular.  I've heard it stated that only zone
>> transfers use the tcp port, but it was my understanding that it could
>> also be used in other circumstances to handle larger
>> requests/responses.  Are there other uses of TCP/53?  What would they be?
>> Thanks,
>> -- Ralf Durkee, CISSP, GSEC, GCIH, GSNA
>> Principal Security Consultant
> All queries can be either UDP or TCP. Sometimes servers, routers or
> firewalls are broken and TCP is your only chance.
> Address spoofing attacks dont work with TCP because they are building
> a session. In the long run some people would like to get rid of UDP
> and use TCP only, especially on open resolvers.
> Kind regards
> Peter and Karin


"Hey Guys, does anyone know what 'poon tang' is?"

-C.S. Dave, July 8, 2K, about 12:30AM

--------Dan Mahoney--------
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