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