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North American Network Operators Group

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Re: Computer systems blamed for feeble hurricane response?

  • From: Joseph S D Yao
  • Date: Tue Sep 13 16:24:08 2005

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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