[arin-ppml] IPv4 is depleted today - unrealistic statements about IPv6 inevitability

Howard, W. Lee Lee.Howard at stanleyassociates.com
Wed Sep 3 10:17:27 EDT 2008

[good work is being done on routing scalability] > They don't 
> buy growth forever, but they buy a lot more than Tony thinks.

Great!  Can I (if I were a major ISP) buy 10 routers using this
architecture in time to design, test, and deploy before the
inflation of the routing table presumed in this thread?

> > Routing does not scale to 4 billion routes.  Don't know 
> exactly where 
> > hardware can't do it anymore.
> Doesn't have to. As long as the /24 lower boundary on 
> routability holds, IPv4 will stay on a logarithmic growth 
> curve that flattens out somewhere around 7M or 8M routes. 

Is that a fair assumption?  The argument I thought I was 
reading said that aggressive deaggregation was easier and
cheaper than deploying IPv6.

> In other words, IPv6 is not the only choice. The best choice 
> maybe, but don't for an instant imagine that  properly 
> motivated people can't find a way to make the IPv4 Internet 
> continue to grow.

I do indeed imagine that.  It keeps me awake at night.  We're
using different constraints on the term "IPv4 Internet" though.

> > If large network operators have to [make IPv4 continue to 
> work] will 
> > that always be cheaper and provide better connectivity than
> > IPv6 with translation technologies (tunnels, NAT-PT, teredo, 6to4,
> > whatever: 
> http://www.getipv6.info/index.php/Planning_IPv6_Deployment)?
> That approaches the real question: IPv6 migration has a cost 
> function and so does IPv4 growth. Where do the cost lines 
> cross? When does it become less expensive to deploy IPv6 and 
> exert the push that brings
> IPv4 to a close?
> The plain truth is that we don't have enough data to do 
> better than guess at the answer to that question. 

I agree with your question.  What data would we need?  Is it 
possible to get such data, so network operators will be able
to make well-informed design and purchasing decisions?

> But we do 
> know that each IPv6 route costs 2 to 3 times as much to 
> implement in the router as an IPv4 route. And we know that 
> there is no new magic in IPv6 routing:
> multihoming still requires a unique global route.

True, but in IPv6 it's likely to require only one unique global
route, unlike the fragments of CIDR space seen in IPv4.  I saw
in another post you believe it could go from 8:1 to 2:1, which 
gain is largely removed be the address space overhead.  I still
think deaggregation is a stupid way to do TE, and that BGP needs
another knob for that purpose, but I understand the difficulty
in getting that knob adopted (unless somebody important decides
to suppress more-specifics where an aggregate is announced and
otherwise override deaggregation TE).

> If I had to guess, I'd guess that the cost lines never cross. Even as
> IPv4 gets more expensive, it remains more cost effective to 
> squeeze a little more out of it than to attempt an IPv6 
> migration. If I'm right, it means that some successor 
> technology that directly solves the routing problem will 
> leapfrog IPv6 in 10 or 20 years without IPv6 ever having 
> reached useful deployment or ever having paid back its early adopters.

You know, if all that happens with IPv6 is that it generates
enough innovation in IPv4 to keep the Internet largely intact
and stable, I'd be happy.

I understand your points, and you're largely right, but where 
we have insufficient data it still looks to me that
when comparing cost and risk, sticking with
IPv4 is higher on both in the long run. 

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