RE: Running code (Was: I-D Action: draft-ietf-6man-ipv6only-flag-03.txt)

["Manfredi (US), Albert E" <[e-mail]>]

-----Original Message-----
From: ipv6 <[e-mail]> On Behalf Of Simon Hobson

> You've missed the fact that most nodes these days will autoconfigure a link-local IPv4 address. So "no address = no protocol" doesn't work. "no address (other than link-local) = no protocol" doesn't work either as it would break any network using link-local addressing - they do exist.

No problem, right? With the IPv6-ony flag set, what would a host do? If it does autoconfigure an IPv4 address, maybe to talk to some old printer, it can do so also with the new heuristic. What the host will know is that it can’t route anything outside. There is nothing here that the flag changes. And besides, who knows what hosts will do when they receive that IPv6-onky flag. We are simply speculating. Whether the better heuristics, or this new flag, makes little difference.

> It's accepted that if devices ignore the flag then they can still play around in IPv4 link-local space - but that's not the intent of the flag. The flag is to inform nodes that IPv4 isn't supported on the network and so they can disable the protocol, saving battery (and probably memory) as well).

And our new heuristics can do exactly the same thing, without a flag. To conserve power, try first IPv6, and use only IPv6 if it works. If not, give IPv4 a short try. See if a default router exists and if DNS works in IPv4 format. If not, stop wasting power on IPv4. All of this caveated the same way. A host might still want to go to that old printer which only uses IPv4, but the host will know that nothing routed outside will work with IPv4.

> A [user-entered] setting for it is not practical for a number of reasons. Firstly, it will need to be changed when the user moves between different networks, secondly in most of the scenarios talked about, the user device is unknown to and the network operator and not managed by them. The aim is to be able to give the devices a flag which will **relliably** and **automatically** tell them that they can save the resources they'd otherwise expend on IPv4 operations.

Reliably and automatically is to allow the device to use IPv6 and IPv4, i.e. the default. It will do just what the flag intends.

I just don’t see why the insistence on this flag, if I can do just as well without, and furthermore, without having to trust a net admin to set this flag. The simple fact is, no one is begging for this flag, it seems. I've been following the entire debate. An equipment vendor serious about saving power has other options he can pursue on his own. A network operator serious about preventing IPv4 chatter is perfectly capable of L2 filtering, wherever that's available, and otherwise providing no IPv4 services.

Either way, the only hosts which will NOT holler, when you shit off IPv4, are the updated ones. Updated to read this flag, or updated with the better heuristics, makes no big difference.

Bert