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

>> Which says, I have no peripherals configured which require IPv4
>
> how do you know in advance that there are no peripherals that the user might want to connect to which are IPv4 only ?

Does not matter. The updated host prefers IPv6. If there has been nothing configured that requires IPv4, IPv4 is not used. If the user has to set up a new peripheral that is IPv4-only, the OS will have to be informed of that, when the user sets it up. (Might also involve installing new drivers.) All part of the process. The user, of course, can be oblivious of these details.

>> I have no old IPv4 PCs with which I'm sharing drives
>
> how do you know that the user won't want to connect to an IPv4 only share ?

Same answer. Absolutely nothing here, flag or no flag, must ever preclude starting up IPv4, if the need arises. The flag does not change anything. Even with flag set, you cannot create a case where things suddenly start breaking, only because the user's device got a software update.

>> I have access to one or more IPv6 default routers
>
> describes pretty well every dual-protocol network)

Not necessarily. You boot up your device on this new network, and you are presented with IPv6 default router options via RAs. You have no IPv4 default router configured, no router advertisements to use to set up any IPv4 default router, no peripherals set up which require IPv4, but you do have IPv6 default routers and IPv6 DNS. So, why bother even trying IPv4? You don't need to ... not yet anyway. If your device is not already configured to use IPv4 assets of any sort, then it won't need to transmit IPv4. That could change, in the future, and nothing must prevent this.

>> so I don't need to use IPv4 for anything.
>
> So your user of a device on a dual-protocol network goes into whatever UI they have to find local devices (printers, file shares, etc). They didn't previously have any persistent IPv4 connections defined*, the network is dual-protocol so you have at least one default router for IPv6 - by your heuristics the user will not find any IPv4 only devices. So you have broken the network for them.

A device which really wants to save power will prefer the IPv6 printer(s). It's easy enough, if you want to "find all other printers available," to start IPv4, without involving any net admin. This breaks nothing. The device maker and the user are perfectly capable on deciding just how much they are into saving power, even on dual stack networks.
 
>> True story.

>> So I had to do some research. Come to find out, even though the US Supreme Court had decided that time-shift recording is perfectly legal, a "do not copy" flag was still configured, in these recording devices. So, I called the engineer from the one station giving me this problem, and the nice guy on the other end had no idea they were transmitting this blasted flag. But, the problem did go away after that.
>> 
>> Lesson learned (for me, anyway): best to avoid flags that aren't really essential.
>
> The lesson learned from this is that the flag is the right way to do it. The flag was incorrectly set causing a **hard** fault, it was diagnosed and unset, problem solved.

Problem didn't need to exist! The Supreme Court had already decided. Users should not have to do research, to use their equipment legally. The obvious course of action would have been for the manufacturer to send an update, which disabled reading of the "do not record" flag entirely, on this particular device. There should no longer be any situation in which a broadcaster can prevent the user from doing what is perfectly legal, in his home equipment.

Same with this IPv6-only flag. You eliminate unnecessary risk, you don't try to dream up obscure corner cases, where just maybe, some of the time, it might help. The heuristic model is trivially easy, in this case. It's called, "recording the broadcast program, for the purposes of any in-home time shifting device like this one, is always permissible." In our case, starting to use IPv4, for internal network usage, e.g. for a new peripheral in my local network, id always permissible.

Bert