At Mon, 14 Jul 2008 03:30:50 -0700, Erik Nordmark <[EMAIL PROTECTED]> wrote:
> there are currently two places where we treat autoconfigured addresses > differently than on-link prefixes. > One is the text about storing the address and associated lifetime in RFC > 4862 that we are debating here. > The other one is the 2 hour rule that was very explicitly added only for > the addrconf property of the prefix and not the on-link property. > > I don't recall the different treatment for the first case. > But for the second case I clearly recall the argument that loosing the > IP address (by an accidental or malicious RA with a zero valid lifetime > for the prefix) was considered a lot worse than loosing the on-link > property. Basically that loosing the IP address for a short time (it > might be re-added by the next RA) is something we must avoid, but that > "routing" (the on-link property) is something which must be able to > recover from temporary failures in any case. Yes, I recall that discussion, too. > [I don't know if the same argument was present when the storing of > addresses was discussed.] > > > I'd accept, if > > > > 1. we prohibit both address caching and on-link caching (with > > reasonable argument, of course) > > or, > > 2. we don't talk about on-link caching (either allow or prohibit) if > > we don't talk about address caching > > > > but it would be unfair if > > 3. we prohibit on-link caching while ignoring its effect on address > > caching. > > If we are going to require that all aspects of a prefix should be > treated identically then to be consistent we must also make the 2 hour > rule be consistent (by either removing it for the addrconf property or > adding it to the on-link property). > > FWIW I think forcing such consistency is not necessary; it would just > result in unneeded changes to already deployed standards. There's a subtle difference. In the two-hour-rule case, we assume we have a working router. So even if the host looses its on-link prefix information, it can still send packets to the router, having it forward the packets and/or send a redirect back, etc. In the address storing case, (at least in my understanding) we consider the case when a router is temporarily out of service. And since we dropped the on-link-by-default rule, the cached address will effectively be of no use. > Is your concern that there are deployed implementations which store > on-link prefixes across reboots? No, it's rather a meta level concern. What I wanted to say (in case I was not clear) is that we should not pretend that killing on-link prefix caching is independent from address caching. If we kill the former, we will effectively also kill the latter (which has implementors - note: we don't implement it). So, IMO, if this document wants to kill on-link caching, it should at least note that it also kills address caching in effect. If implementors of address caching still think it's acceptable, then I have no objection to that (I have no stake in that area, anyway). I hope I'm clear this time. --- JINMEI, Tatuya Internet Systems Consortium, Inc. -------------------------------------------------------------------- IETF IPv6 working group mailing list [email protected] Administrative Requests: https://www.ietf.org/mailman/listinfo/ipv6 --------------------------------------------------------------------
