Ronald, RvdP> There is a big difference between planning/engineering for a transition RvdP> and planning/engineering for a coexistance. There seem to be forces RvdP> trying to steer to the latter. Seems like an important question. Why RvdP> would we want an internet with two protocols with the same functionality RvdP> running in parallel? Should that be the goal? It is not possible to have a flag-day event for switching to a replacement service. Hence, there must be a transition that takes some time. Remember that this involves thousands of independent administrations and many tens of millions of systems Any detailed consideration of the mechanics and time-frame required of such a transition -- and, yes, I said required; not desirable, not likely, but required -- you will discover that those details look exactly like "coexistence". d/ -- Dave Crocker <mailto:dcrocker@brandenburg.com> Brandenburg InternetWorking <http://www.brandenburg.com> Sunnyvale, CA USA <tel:+1.408.246.8253>, <fax:+1.866.358.5301>