[84457] in North American Network Operators' Group
Re: Computer systems blamed for feeble hurricane response?
daemon@ATHENA.MIT.EDU (Joseph S D Yao)
Tue Sep 13 16:22:46 2005
Date: Tue, 13 Sep 2005 16:20:40 -0400
From: Joseph S D Yao <jsdy@center.osis.gov>
To: Mike Tancsa <mike@sentex.net>
Cc: nanog@nanog.org
Mail-Followup-To: Mike Tancsa <mike@sentex.net>, nanog@nanog.org
In-Reply-To: <6.2.3.4.0.20050913160427.083fec20@64.7.153.2>
Errors-To: owner-nanog@merit.edu
On Tue, Sep 13, 2005 at 04:15:29PM -0400, Mike Tancsa wrote:
> At 03:50 PM 13/09/2005, Joseph S D Yao wrote:
>
> >Oh, and also ... please consider that some firewalls try to discern
> >whether the connection on port 25 is from a mail server or from Telnet.
> >While I mourn the simplicity of manual debugging of such sites, it
> >remains that: the fact that you can't TELNET HOST.DOMAIN 25 doesn't mean
> >that there's no mail service there.
>
> Making a network connection using the application "telnet" vs the
> application "sendmail" (or whatever MTA one uses) seems to be the
> same when doing a tcpdump on the data. I am not sure how a firewall
> would know -- purely at the network layer -- what the other side's
> application was/is that initiated the connection. Yes, the other end
> could try and connect back to the host, but there is no 2 way traffic
> as the 3way handshake is not completing and I dont see any other
> traffic coming back from that host attempting to discern any info.
I don't know, myself. I said they try. Perhaps they succeed. Perhaps
they check the speed of incoming queries. Perhaps they try to use a
Telnet OPTION. I don't know. Perhaps it's a sales gag. [I think it
was a telnet OPTION, actually.]
--
Joe Yao
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