[ppml] Re: 2005-1:Multi-national Business Enablement

Stephen Sprunk stephen at sprunk.org
Tue May 3 14:38:45 EDT 2005

Thus spake "Daniel Roesen" <dr at cluenet.de>
> On Thu, Apr 28, 2005 at 06:56:04AM -0500, Stephen Sprunk wrote:
> > IPv6 mandates a particular topology and disallows others
> > which happen to be in widespread use by IPv4 ISPs.
> I have problems imagining both. Can you give me an example?

IPv6 mandates that users must be given a subnet of their own; it is common
practice with IPv4 to issue individual addresses on a shared subnet to
reduce waste.  These methods are incompatible.

> > It's common for cable, DSL, wireless, and other technologies.
> > For instance, my landlord provides a straight ethernet connection
> > into my residence (which is connected to a T1); with DHCP, I
> > consume only one IP per PC.  For them to offer me an IPv6 /48
> > or even /64, they'd need to change their IPv4 addressing to a
> > /30 or shorter for each customer, wasting four addresses for a
> > customer with one PC.
> But that's considered perfectly fine use of those addresses, not
> "waste". Sure, the result are unused addresses, but the way of usage
> if sound.

I sincerely hope that ARIN would not approve any request for IPv4 space that
was based on 80% addressing overhead.  I'm pretty sure that's a policy
violation; if not, it should be.  We're short enough on IPv4 addresses as it
is; pissing 80% of them away for aesthetics is irresponsible.

> I do generally consider a shared L3 subnet a mistake by itself,
> especially for security reasons (I know there are methods to battle
> those).

You may consider it a mistake, but the practice is widespread and works
perfectly fine, not to mention it is the most efficient use of address

> > If that's the topology, then that makes sense.  However, it's not the
> > dominant topology in the US today.
> And global IPv6 policies should adapt to US legacy? Or what are you
> asking for?

I'm asking that IPv6 policies allow ISPs to roll out IPv6 without having to
completely reengineer existing IPv4 networks as well as quintuple IPv4
address requirements.

> [my presumption is that we want to reach global policies, not regional
> ones for that]

I thought one of the reasons we have RIRs is that different regions may need
different policies.  If the RIRs are going to consider themselves hostage to
decisions made a decade ago by the IETF, there's not much point in having
RIRs at all; let's give worldwide address allocation back to the goons at

> > > The mantra is "/48, no questions asked, and by default".
> >
> > When you consider how that affects the IPv4 topology, that
> > doesn't make sense in many cases.  If we're going to share
> > subnets across customers in IPv4, we need to do the same
> > for IPv6.
> Not necessarily. You might take it as a starting point to migrate
> your legacy setup to a possibly better one. :-)

This is not legacy -- it's current practice for IPv4 and arguably better
than the alternative for several reasons.  For that matter, I'm willing to
bet you'd find the same topology in other countries if you looked.

> But well, I don't care if US ISPs are giving only /64s to their
> customers. I do enjoy living in EU where I hope that /48s will be the
> default (a man needs to dream once in a while). *g*

I also hope that /64s and /48s will be available in the US to those who want
them, but I'd be much happier getting a few /128s (one per host, via
autoconfig).  And I say that as a "power user".

Without sensible policies, I won't be getting IPv6 at home (or at work, if
2005-1 doesn't pass) at all.  It's not routing or transit in the core that
we're waiting on now -- it's address policies at the edge.


Stephen Sprunk      "Those people who think they know everything
CCIE #3723         are a great annoyance to those of us who do."
K5SSS                                             --Isaac Asimov

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