Vint, vgc> If you look at the instant messaging systems, they map a private vgc> identifier space (IM name or "handle") into IP addresses and vgc> apparently run background heartbeat to re-assign the mapping if the vgc> identifier in the heartbeat arrives in a packet with a different IP vgc> address than before - I was under the impression that they did not handle mobility nearly so dynamically or automatically. Rather, I seem to need to log in whenever I move. So they seem to do a login-time mapping. (On the other hand, the login for IM is usually automatic.) In any event, I suspect that your domain name-based suggestion is the right one to pursue. That is, use DNS for the public, persistent name, and have a record that points to a dynamic address-mapping registry. (One might even think of mapping to a "presence" service...) Somehow, dynamic DNS does not seem like such a good idea, for anything that might change this much or this rapidly and serious host mobility. 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>