> And to Keith - yes, apps need to get a lot smarter (or perhaps a lot dumber) > about their use of addresses. That's true now with IPv4 - we've been using > temporary use addresses ever since we started using dhcp for address > assignment. Addresses come with a lease length, after which they might > be renewed, or might not be. Applications, and application protocols > simply need to deal with that. Currently we're surviving largely by > blind luck - that is, the applications that most people use need an address > to be valid for (at least) an order of magnitude less time than typical > address validity (perhaps commonly 2 orders). So, applications are just > ignoring the issue completely. To be correct, they shouldn't.
I've come to the opposite conclusion - that it's completely unreasonable to expect apps (or hosts) to assume the burdens of: - selecting the "right" address from several alternatives without knowledge of their own location in the network topology and that of all of their current and future peers, - dealing with multiple addressing realms (limited-scope addresses are another form of this), where the components of an app are not all in the same realm, or - expecting apps to know enough about network topology to explicitly tunnel through (or configure) NATs, and - continuing operation across address changes without either support in lower layer protocols to do this or a reliable means of propagating address change information to everyone who has an old address (they don't necessarily have an open connection) and that to the degree that apps were ever expected to do this, the folks who expected them to do those things were on drugs. it's not just that the apps are being expected to make decisions in the absence of adequate information to make those decisions (as in, which of the following N addresses is the best one to use?), it's also unreasonable to impose burdens on every app that are better handled by the network. (e.g. the routing system is having scaling problems, so we'll let hosts or apps do address selection to avoid having multihomed sites defeat provider-based addressing - never mind that they are even less prepared to do routing than the routing system.) We're not "surviving" by blind luck at all - we're "surviving" by pretending that the only apps that matter are those which only need addresses for a short time (e.g. "web and email are typical") and ignoring the apps that fail when this assumption doesn't hold. Keith -------------------------------------------------------------------- IETF IPng Working Group Mailing List IPng Home Page: http://playground.sun.com/ipng FTP archive: ftp://playground.sun.com/pub/ipng Direct all administrative requests to [EMAIL PROTECTED] --------------------------------------------------------------------
