Let me start out by saying I'm allergic to CGN, but I got to ask the question:
Some of the CGN providers are coming out with "fixed" nat solutions for their IPv6 transition/IPv4 preservation technologies to reduce logging. This appears to provide for a static mapping of outside ports/IPs to a particular customer such that the service provider doesn't need to log literally every session through the box. At the last nanog, I seem to remember someone stepping up and discussing the problems associated with just taking ports 1025 through 1025+X and giving it to some customer and had brought up the idea of using a hash or salt to map what would appear to be random ports to a customer in such a way that you could reverse the port back to the customer later if need be. For the life of me, I can't find anything on the internets about this concept. I had it in my head it was a lightning talk or something, but reviewing the agenda doesn't ring any bells. Anyone know what I'm talking about and what it's called? -e