What is the sense of telnet on 53 port?

[Brad Knowles]

At 1:24 AM -0700 7/27/01, Kankossa wrote:

>  - I know that telnet, ftp, smtp, http both must read /etc/resolv.conf.

	Not really.  They just use the resolver library, and the resolver 
library reads this file.

>  So, if I do: telnet www.redhat.com 80 and I reach it, this implicitely
>  constituous a test that my DNS works (both gethostbyname() and
>  gethostbyaddr() have been performed).

	Again, not necessarily.  The resolver library may have been 
configured to look in a local /etc/hosts file first, and only proceed 
to the DNS if the information can't be found there.

>  - Can Bind be forced to use only TCP to communicates?

	BIND itself?  No.  You can force dig to use TCP when doing 
queries, as can anyone using the resolver routines, but you can't 
force the nameserver to use only TCP.

>  -In recent versions of Bind where DNSSEC and  IXFR, DDNS, Notify,
>  EDNSO protocoles are included, is this means that TCP must be used
>  instead of UDP even for a simples request of addresses resolutions?

	EDNS0 expands the UDP-based protocol to allow much longer 
packets, but is not necessarily a requirement for supporting the 
other features.  Because of the additional data that would be in the 
DNS, this means that you will probably frequently be using TCP to 
perform DNS queries, but there is also a chance that some of this 
information may fit into a standard 512-byte UDP packet.

-- 
Brad Knowles, <brad.knowles at skynet.be>

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