[Off-Topic] Scary Patenting?

["Ravikant K. Rao" <ravi@xxxxxxxxxxx>]

All:

	To Quote LWN - 

Has Cisco patented NAT?. It turns out that Cisco has a patent on a
"security system for network address translation systems". Depending on
your reading of the patent and what it really covers, this could be one of
the more threatening software patents to come along yet. 

NAT has been a feature of Linux networking for years - though the Linux
world has generally referred to it as "masquerading." Essentially the
feature allows the hiding of a network of systems behind a single
gateway. All outgoing connections appear to come from the gateway itself -
the systems behind it are invisible. They are also, normally, unreachable
from the outside; this feature means that a box running NAT/masquerading
can often serve as a simple and highly effective firewall. 

It is the firewalling ("security") feature of NAT that Cisco claims a
patent for. The claims in the patent text describe the basic NAT
algorithm, then add features like dropping inbound TCP packets that do not
correspond to an existing TCP connection. Passing through FTP data
connections and certain types of ICMP packets are also claimed as patented
features. These are all things that the Linux implementation does. 

If Cisco decides to get obnoxious - and there is no evidence of that at
this time - this could be the first serious patent issue to reach deeply
into the Linux kernel. The basic NAT implementation in Linux predates the
patent application, and thus qualifies easily as prior art. But some of
the fancier filtering features may not. The possibility of a patent
challenge reaching deeply into the Linux kernel exists. This one is worth
keeping an eye on. 

	</QUOTE>


	Check out the details:

		http://www.patents.ibm.com/details?&pn=US05793763__

	-ravi

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