If you look at the instant messaging systems, they map a private identifier space (IM name or "handle") into IP addresses and apparently run background heartbeat to re-assign the mapping if the identifier in the heartbeat arrives in a packet with a different IP address than before - not sure whether or how hijack is avoided. Could one use the NAPTR concept to create a new identifier space with specific dynamics? It would take two lookups: one to DNS to get the NAPTR and one to resolve the NAPTR identifier into an IP address. The latter resolution need not necessarily be done via DNS. vint Vint Cerf SVP Technology Strategy MCI 22001 Loudoun County Parkway, F2-4115 Ashburn, VA 20147 703 886 1690 (v806 1690) 703 886 0047 fax vinton.g.cerf@mci.com www.mci.com/cerfsup