[SNIP]

> >NetBSD implements PMTUD, and a version of Dave Borman's syn-cache
> >code.  Not sure what other TCP sequence-number checks you're refer to;
> >the Cisco-patented window-checks designed for attacks against BGP, or
> >something else?
> 
> Not sure what you mean by "Cisco-patented window-checks". If you mean that 
> of checking the TCP sequence number in the ICMP payload, then that's not 
> patented by Cisco. I had received a notification from Cisco's lawyer when I 
> published the first version of my draft, saying that they had a pending 
> patent on it.

I guess he means this: 
http://www.ietf.org/ietf/IPR/cisco-ipr-draft-ietf-tcpm-tcpsecure.txt
(statement by Robert Barr from Cisco about the license)

The draft itself is here:
http://www.ietf.org/internet-drafts/draft-ietf-tcpm-tcpsecure-00.txt
Though, the page cannot be found now anymore ...???
I guess the ietf moved the page somewhere else, i can't find it now.
Bye,

Mipam.