Spherical cows are the punchline of a classic joke. Today, we’ll assume the internet’s spherical cow: IPv6. Assume IPv6 was prevalent enough that we each had, free with our usual internet connection, and IPv4 connection. It would obviously solve some problems: no need for NAT means that any two computers are peers — truly. Any computer can connect to any computer, given correct local firewall configuration. What problems wouldn’t it solve?
Long-lived connection. I could obviously get on dyndns, and make sure my laptop continually registers its current IP in moshez.example.com. That means that if I were to run a web-server on my laptop, it would be continually “up”, assuming my laptop was. This is not far-fetched, really — if I bought a “cell internet provider” card, and I set up the laptop to look for preferred wireless networks, and barring that use the provider card, I would have a more-or-less constant connection. Add to that some extension of battery life, and it’s not really science fiction (well, no more than already assuming IPv6).
Privacy. Sure, with IPv6 comes “opportunistic encryption” and trying to constantly encrypt, but it seems that the key exchange stuff is really hard to configure.
I suggest something more extreme. “Opportunistic VPN”. When I want to connect to an IRC server, I don’t do it over TCP/IP. I build up a VPN, with a non-global IP address, and use that to connect to the IRC server. If either the IRC server or I move, we re-negotiate the VPN, and continue the *same connection*. All we really need is to formalize the “dyndns” is something which is more akin to IM services’ presence-notification. In fact, we could piggy-back on same. Eventually, of course, the IM services would be nothing but presence notification, as the chat link itself would be over an ad-hoc VPN between the users. “Chat rooms” would be dedicated repeater-user, but require nothing else…they would be orthogonal to the presence service.
Currently, a lot of the “emulating long-lived connections” is done over the web, using cookies as the “ad-hoc VPN” IP. If ad-hoc VPNs were more universal, the “identity cookie” (as opposed to other uses for cookies) would be replaced by the locally relevant IP.