I stumbled across the following lecture notes and thought they made an interesting read. I'm not vouching for the accuracy of its contents (in fact with the amount of information presented, there's bound to be some mis-information) therefore "consume at your own risk". I have no affiliation with the authors or publisher (University of Westminster), however I certainly thought I learnt a few things. http://www.wmin.ac.uk/ITRG/IS/DPI/HIW/PM1.pdf http://www.wmin.ac.uk/ITRG/IS/DPI/HIW/PM2.pdf regards Peter Badcock ============================================================================================================= To unsubscribe from this list, go to www.freelists.org and logon to your account (the same e-mail address and password you set-up when you subscribed,) and unsubscribe from there.