[84484] in North American Network Operators' Group
Re: mail service with no mx (was - Re: Computer systems blamed for
daemon@ATHENA.MIT.EDU (Adam McKenna)
Tue Sep 13 20:00:27 2005
Date: Tue, 13 Sep 2005 16:59:50 -0700
To: nanog@nanog.org
In-Reply-To: <Pine.LNX.4.62.0509131622030.16184@sokol.elan.net>
From: Adam McKenna <adam@flounder.net>
Mail-Followup-To: nanog@nanog.org
Errors-To: owner-nanog@merit.edu
On Tue, Sep 13, 2005 at 04:31:05PM -0700, william(at)elan.net wrote:
> Telnet option negotiation is at Layer 7 after TCP connection has been
> established. Firewalls typically don't operate at this level (TCP session
> is Layer 4 if I remember right) and would refuse or reject (difference
> type of ICMP response) based solely on attempt to connect to certain
> ip or certain TCP/UDP port.
Application layer firewalls have existed for at least 6 years.
--Adam
