On Nov 2, 2010, at 4:55 AM, Karl Auer wrote: > On Tue, 2010-11-02 at 10:51 +0000, Tim Franklin wrote: >>> That breaks the IPv6 spec. Preferred and valid lifetimes are there >>> for a reason. >> >> And end-users want things to Just Work. The CPE vendor that finds a >> hack that lets the LAN carry on working while the WAN goes away and >> manages to slap the "With Home Network Resilience!" label on the box >> correctly will presumably do quite nicely out of it. > > But - preferred and valid lifetimes do *exactly that*. The address is > fully usable up to the end of the preferred lifetime. It is then > deprecated (but not unusable) until the end of the valid lifetime. Only > after the valid lifetime does it become unusable. DHCPv6 lifetimes are > exactly the same as RA lifetimes - and of course there is nothing that > says the RA lifetimes have to be the same as the DHCPv6 lifetimes > (though some sensible relationship would be advisable). > > So loss of connectivity to the upstream is not going to blow away a home > network. It will keep working fine, even if the upstream goes away for a > while. It's up to the upstream to use lifetimes that are a good > compromise between flexibility and stability. > > About the only hack I can see that *might* make sense would be that home > CPE does NOT honour the upstream lifetimes if upstream connectivity is > lost, but instead keeps the prefix alive on very short lifetimes until > upstream connectivity returns. > Which is exactly what was being proposed when Tim responded that it would break the IPv6 spec.
Owen
