"A Technique for Counting NATted Hosts", Steven M. Bellovin original link http://www.research.att.com/~smb/papers/fnat.pdf
but it's slashdotted now, so try this instead http://216.239.57.100/search?q=cache:QZA0opGpxtwC:www.research.att.com/~smb/papers/fnat.pdf+&hl=en&ie=UTF-8 jim
