>>>> How do you renumber the IP address stored in the struct sockaddr_in >>>> in a >>>> long running critical application? > > Disconnect current session, reconnect. Uh, not unless your application has some sort of retry or checkpoint-restart capability. SMTP is pretty resilient in the face of connection breakage, and for some interactive applications you just hit "retry" or the equivalent, which has caused some people to think that somehow it's okay if the network changes a host's IP addresses out from under it. But it doesn't work in general. >> And for that matter, a DNS name is not a host name, and hasn't reliably >> been a host name since at least the mid 1980s. Just because you get >> address A1 from doing a lookup on a name at time T1 and an address A1 >> from doing the same lookup at time T2, doesn't mean that those addresses >> will connect to the same (layer 3 or higher) stack. > >> So even if we somehow magically changed our existing transport protocols >> to be able to support changes to endpoint addresses on the fly, DNS >> names as they are currently used are not suitable as endpoint >> identifiers for such a purpose. At best, existing DNS names serve as >> identifiers for the initial contact only. > > This falls under the heading of "nobody is stopping us from doing this > and it works today so now it's a feature and it can never be taken away". No, it just means that people shouldn't assume that existing DNS names (i.e. the ones we're already using to identify hosts and services) will work as endpoint identifiers for the purpose of connection restart. People are using DNS names to name things that aren't hosts (e.g. services or groups of hosts) for valid reasons and any solution that destroyed this functionality would be a non-starter. > As for renumbering, on a Cisco router, I can make the following > configuration: > > [deleted for brevity] > This way, the router obtains an IPv6 prefix dynamically from a DHCPv6 > prefix delegation server and then sends out router advertisements > using that prefix. So you can renumber the router and all the hosts > connected through it by changing one entry in a DHCPv6 server config. That's the least of the problems with renumbering. A few years ago I was involved in renumbering of a class B IPv4 network. DHCP and DNS doesn't even begin to cover it. > Even with the current state of the art I'd say that renumbering > clients is not a big deal. Renumbering servers is more difficult, though. The distinction between client and server is fairly meaningless. It's certainly not something you want to assume in a renumbering architecture. Every host is a server in some sense. Keith _______________________________________________ Ietf@xxxxxxxx https://www1.ietf.org/mailman/listinfo/ietf