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North American Network Operators Group Date Prev | Date Next | Date Index | Thread Index | Author Index | Historical Re: Computer systems blamed for feeble hurricane response?
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 ----------------------------------------------------------------------- This message is not an official statement of OSIS Center policies.
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