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

Stephen Sprunk stephen at sprunk.org
Wed Sep 3 00:47:22 EDT 2008

William Herrin wrote:
> On Tue, Sep 2, 2008 at 5:40 PM, Howard, W. Lee
> <Lee.Howard at stanleyassociates.com> wrote:
>> 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. But we do know that each IPv6 route costs 2 to 3 times as much to implement in the router as an IPv4 route.

Yes, one IPv6 route is more expensive than one IPv4 route, due to the 
simple fact that they're longer.  However, it is expected (with a 
reasonable basis) that each org will have fewer IPv6 routes because the 
RIRs are deliberately giving each org far more space than they should 
ever need, plus reserving plenty of room for unexpected growth.  We're 
looking at an order of magnitude reduction, at least, in the number of 
routes in the DFZ if the current folks using PIv4 switched to PIv6.  Of 
course, the natural result is that more orgs will be allowed to get PIv6 
space, but then you're no longer comparing apples to apples.

> And we know that there is no new magic in IPv6 routing: multihoming still requires a unique global route.

For now.  The RRG is working on that part of the problem.

> 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.

I think your statement is true if you look at it from a short-term cost 
perspective each quarter, but not if you look at the long-term costs.


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