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 Brian Haberman

> I think your observation is key for everyone. The flag only indicates
that the router(s) will not route IPv4 off the link. There is nothing
stopping devices from using IPv4 locally on the link to communicate with
other such devices.
>
> The same thing occurs today with devices using IPv6 link-locals on
IPv4-only links.

Agreed.

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

> OK, explain how the device is to know whether or not it should be turning on IPv4 to see if there's an IPv4 printer it needs to talk to ?

That should occur when you set up the printer, when you load the printer driver. In my own experience, I have had to enter the actual IP address, EVEN OF enterprise printers, when the DNS for some reason or other didn't contain its name. So that's one way the host can determine to use IPv4, for that printer.

And too, even in an enterprise net, one can potentially have a printer or other specialty device, like a CD-ROM label maker, in an office, or in a suite, where that specialty device is not under the control of the IT people, and access to it has to be IPv4. A flag, or heuristics, c'est la même chose.

> IFF there is an old IPv4 only printer that the user needs to access, then the admin would not set this flag.

What Brian said. Sorry, that's wrong. If any host uses the flag that way, that host is broken. Which is part of the risk of the IETF creating such a flag, without very explicit instructions on its use by hosts. Instructions which the equipment designer might simply want to ignore, along with the flag itself.
 
Mikael says it would be used as an extra input to the heuristics, which is IMO the actual way it would ever get used.

> Again, you've missed the point - it's not about hosts hollerin, it's about allowing hosts to operate more efficiently.

I missed no such point. There are two interests here: a network admin wanting to shut off IPv4, for whatever reason, and a host wanting to conserve energy. I'm simply saying, if the network wants to shut off IPv4, chances are, flag or no flag, someone's going to holler. Flag makes zero difference. Anyone with an older device will be unhappy.

Bert