Dual stack IPv6 for IPv4 depletion

Matthew Kaufman matthew at matthew.at
Sun Jul 5 23:23:46 UTC 2015

On 7/4/2015 5:09 AM, Josh Moore wrote:
> Traditional dual stack deployments implement both IPv4 and IPv6 to the CPE.
> Consider the following:
> An ISP is at 90% IPv4 utilization and would like to deploy dual stack with the purpose of allowing their subscriber base to continue to grow regardless of the depletion of the IPv4 space.

Admirable goal.

>   Current dual stack best practices seem to recommend deploying BOTH IPv4 and IPv6 to every CPE.

That's what "dual stack" means, yes.

>   If this is the case, and BOTH are still required, then how does IPv6 help with the v4 address depletion crisis?

Well, you dual-stacked your subscribers about 5-8 years ago, and about 
3-5 years ago we're basically done moving all content they might wish to 
access to IPv6 as well. So about a year ago, you've been able to offer 
an IPv6-only product that actually works just fine... and you charge 
extra for IPv4 (which most people don't want/need at this point)

>   Many sites and services would still need legacy IPv4 compatibility.

Well,... because you and every other ISP dual-stacked over 5 years ago, 
and the transition is just about done, I wouldn't call it "many" at this 

> Sure, CGN technology may be a solution but what about applications that need direct IPv4 connectivity without NAT?

By now, there aren't any such applications in wide use. A few legacy 
things that couldn't be updated, sure, and for those you can still offer 
IPv4 addresses and access to the few people willing to pay extra for that.

> It seems that there should be a mechanism to enable on-demand and efficient IPv4 address consumption ONLY when needed.

That's not needed, because with everyone on IPv6, there's more than 
enough IPv4 space available for you... and if you need to buy some, it 
is almost worthless, so the prices are near zero.

>   My question is this: What, if any, solutions like this exist?

Nobody bothered to build sharing strategies because it was clear that it 
wouldn't be needed as IPv6 deployment ramped up over the last decade.

>   If no solution exists then what is the next best thing? What would the overall IPv6 migration strategy and goal be?

Just continue the dual-stack approach for those who need it, as you've 
been doing for 5+ years. For the rest, IPv4 is historic.

> Sorry for the length of this email but these are legitimate concerns and while I understand the need for IPv6 and the importance of getting there; I don't understand exactly HOW that can be done considering the immediate issue: IPv4 depletion.

Fortunately, the recent ARIN announcement is of no real concern, because 
you and everyone else moved to a nearly 100% IPv6 Internet years ago.

Matthew Kaufman

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