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Re: IPv6 deployment [was Re: Recent Internet governance events]

2013-11-21 18:19:33
On 22/11/2013 12:29, John C Klensin wrote:

--On Friday, November 22, 2013 11:37 +1300 Brian E Carpenter
<brian(_dot_)e(_dot_)carpenter(_at_)gmail(_dot_)com> wrote:

...
Actually there has been a clear market choice among many ISPs
for years: straightforward dual stack. It works very well. We
also have a plethora of tunnelled solutions, some better than
others, which apply to various different scenarios where the
provider's view is that OPEX for dual stack is higher than
OPEX for tunnels. The service to the application software is
still dual stack (in most cases).

Brian,

Keeping in mind that, with respect to this question, I'm just an
apps guy, but my impression is quite different, mainly:

(1) Unless the service levels between the endpoint machines are
always equivalent when IPv4 and IPv6 are both present and there
are no circumstances in which a choice between IPv4 and IPv6
would make a service difference, there is no such thing as
"straightforward dual stack".

From the apps point of view, that's true; hence we end up with
heuristics such as Happy Eyeballs. I was referring to ISP
(or campus) infrastructure, where people have been running
dual stacks for many years.

(2) The non-straightforward version requires that applications,
at least TCP-based applications, be able to make rather complex
route optimization decisions about which protocol and addresses
to use and make those decisions in a way that completely
violates clean layering models.  We have, in general, never
figured out how applications are supposed to do that, nor how to
make the needed information available to them.

Probably because there is no general solution to that problem,
but IMHO you can't fix that without a time machine that takes
you back to about 1977.

(3) If one is going to have dual stack on the applications
(generally "client") machines, they need either wired-in
simplistic preference models (e.g., "always prefer IPv6") or
protocols for getting information from and controlling border
routers to which they have default routes.  The former has not
served us well and we haven't done the protocol work for the
latter.  Another alternative would be to actually do routing
from the applications machines with either packets source-routed
through the border routers or the latter being completely
transparent.  As far as I know, the Internet has not worked that
way in a very long time and no one has seriously proposed
changing the way it does work.

Actually, in the MIF/Homenet world you will find a lot of discussion
of the need for source/destination based routing.

Now I'm obviously missing, or misunderstanding, something that
allows you to assert that straightforward dual stack is the
clear market choice and works well despite the above.   Could
you explain what it is?

As I said, I'm talking about ISP infrastructure, where the issue
is how to deliver both v4 and v6 service to the customer side
of the CPE box. For years, ISPs that do this by simply running
both protocols have been saying that it's straightforward.

The problems you describe are ones that occur when a host sees
more than one IP service. They don't depend (or very little)
on how those services are carried inside the ISP infrastructure.

On the other hand, I haven't noticed any particular user
issues from this, whether my dual service has come from my ISP,
a campus, or the IETF network.  I'm not sure my wife knows
that she's using IPv6 for a lot of what she does. The problems,
though real, are not blocking for most current users. Also,
IMHO, they have nothing specific to do with IPv6; they are
intrinsic to running two network layer protocols.

   Brian

And the market is not going to make a choice because the
market stakeholders find NAT works well enough for its needs.
And when it doesn't, they will switch to IPv6.

Or they will build bigger NATs or invent a latter-day version of
X.75 gateways at peering points or national boundaries.  It
isn't clear to me that IPv6 is the only remaining choice when
the easiest-to-deploy NAT technologies turn out to be
insufficient or too hard to operate.  If it is not, then we have
no guarantees that IPv6 will be chosen over options and most of
us would consider worse.

What I would do as a government entity is to get a group of
techies to describe a minimum set of technical capabilities
for Internet access points. 
Please don't. The history of government mandates for IPv6 is,
to say the least, chequered. 

Indeed.  Just like the history of government mandates for other
networking technologies.

    john





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