Comment 13 for bug 761558

* Mathieu Trudel-Lapierre

> I've just confirmed it is indeed the case: there is something
> wrong in the LiveCD, and we'll definitely fix that.

Great! :-)

> After re-reading this, I also got to the same conclusion (and also
> with Stephane's careful analysis and testing); IPv4 could
> theoretically be set to "optional" as well, *however*...

Could and should. ;-)

> While I agree that IPv6 deployment is being planned in carriers (and
> ipv6-only also is), I believe majority still will remain, at least
> until Oneiric + 1, that dual-stack IPv4 and IPv6 would be what will
> get deployed if anything. Other networks with specific requirements
> can obviously set a different setting, it's not very far in the
> dialogs.

I don't disagree with this. It's rather unlikely that IPv6-only networks
will outnumber IPv4-only and dual-stacked networks in the forseeable
future.

But, as long as it doesn't cost you anything (in terms of losing any
support for IPv4-only and dual-stacked networks), why not support IPv6-only
networks out of the box as well? I don't understand what the perceived
problem is.

> In other words, let's aim to change that in the release after Oneiric.

I've not given up on making you reconsider... :-)

I'm a primarily a network engineer these days and I work closely with
ISPs, wireless carriers, and others in the industry. (I'm also a old-time
DD and Linux guy, which is why I take an interest in Ubuntu/Fedora/NM
specifically.)

The mood in the industry is that there is a desire to be able to deploy
IPv6-only services, and this goes especially for growth segments where the
shortage of IPv4 addresses are particularly hard felt, especially the
wireless/mobile segment and in the Asian developing economies.

On the other hand, every device and operating system that does not support
IPv6-only operation is an argument against deploying IPv6-only service. Of
course, these have different levels of importance - for example,
non-support by MS Windows would be a non-starter due to its huge market
share, while a Linux distro like Ubuntu is easier to disregard. Of course
it helps if the support can be activated by mucking about in the settings,
but it's not as good as out of the box «plug and play» - anything else
means unwanted support calls and unhappy customers. Fortunately, Apple's
and Microsoft's products support IPv6-only operation out of the box, so we
might very well already be at the point where providing IPv6-only service
is considered viable, but it'd certainly be a good thing for Ubuntu to
catch up.

The more devices that are capable of IPv6-only out of the box, the easier
the IPv6 transition gets. And every organisations that are doing stuff
online, including Ubuntu, have a responsibility and interest in
facilitating the IPv6 transition. For a more in-depth walkthrough of what's
at stake, I recommend you take a look at Geoff Huston's excellent keynote
at Linux.Conf.Au
<http://www.montanalinux.org/videos-lca2011-geoff-huston.html> by the way.

So again, if there's no disadvantage to supporting IPv6-only operation out
of the box, why not do so? And if there is a disadvantage, what is it?

> I was unfortunately bitten by a side-effect of setting IPv4 to
> optional in dual-stack networks: users of dual-stack networks, when
> networks fail to provide IPv4 addresses but do provide IPv6 (my
> router's DHCP process had somehow stopped giving IPv4), will be faced
> with a connection coming up because IPv6 is available. This will mean
> they would get NM to say it's online, although only IPv6 is. They
> would be able to connect to some services that do allow IPv6 (e.g.
> Freenode, Google, some others), but wouldn't get access to IPv4-only
> networks. In order to avoid cater to most users and avoid getting bugs
> against NetworkManager for what is ultimately a network fault, I think
> for the time being it is still best to keep the IPv4 setting to
> required.

So here you have an error in your network that happens to affect only your
IPv4 connectivity. If I understand you correctly, you want in this case to
exacerbate the error to also affect your IPv6 connectivity (even though
there's nothing wrong with it)? If so I have a hard time understanding
why...

Isn't it better, then, to continue to have access to *some* services over
IPv6 rather than to have access to *absolutely nothing* at all? Remember
that some of those services that would remain accessible might very well be
helpful when it comes to solving the original problem (e.g. Google
searches, the ISP's support pages, and so on).

If your point of view is that for as long as there are IPv4-only networks
in existence you cannot make IPv4 optional, we'll have to wait until
Oneiric + 20 before the default can be changed, I think... :-P

I feel your scenario is a fringe case that is unlikely to occur so often
that it will cause an unbearable influx of bugs against NetworkManager, to
be honest... You'll need 1) a user with a dual-stacked network (uncommon
enough these days), where 2) there's something wrong with IPv4 (obviously
way more uncommon than #1), and 3) where the IPv4 problem happens to
manifest itself in a way that makes DHCPv4 fail (an even smaller subset of
#1+#2), and finally 4) where the user will file a bug with NM, instead of
contacting his ISP, or figuring out the problem some other way (an even
smaller subset of #1+#2+#3 again).

I cannot imagine we're left with a significant number of users here. And
remember you'd also have to take into account the amount of users that
would file bugs because Oneiric doesn't work with their IPv6-only T-Mobile
mobile broadband service or whatever, too.

Finally, it's not like you'll be heading into uncharted territory by
making IPv4 optional, either. Microsoft and Apple has gone before and
cleared the path, and for what it's worth I've not heard any reports from
any of my contacts in those organisations saying that their users are
complaining. I honestly think that your fear of bugs are entirely
unfounded. Is that the only concern you have about making IPv4 optional?

Best regards,
--
Tore Anderson