Engineering Lessons, IPv6 Edition

Yes, we really are going to reach a point where the RIRs will run out of IPv4 addresses. As this chart from Geoff’s blog shows —


Why am I thinking about this? Because I ran across a really good article by Geoff Huston over at potaroo about the state of the IPv4 address pool at APNIC. The article is a must read, so stop right here, right click on this link, open it in a new tab, read it, and then come back. I promise this blog isn’t going anyplace while you’re over on Geoff’s site. But my point isn’t to ring the alarm bells on the IPv4 situation. Rather, I’m more interested in how we got here in the first place. Specifically, why has it taken so long for the networking industry to adopt IPv6?

Inertia is a tempting answer, but I’m not certain I buy this as the sole reason for lack of deployment. IPv6 was developed some fifteen years ago; since then we’ve deployed tons of new protocols, tons of new networking gear, and lots of other things. Remember what a cell phone looked like fifteen years ago? In fact, if we’d have started fifteen years ago with simple dual mode devices, we could easily be fully deployed in IPv6 today. As it is, we’re really just starting now.

We didn’t see a need? Perhaps, but that’s difficult to maintain, as well. When IPv6 was originally developed (remember — fifteen years ago), we all knew there was an addressing problem. I suspect there’s another reason.

I suspect that IPv6, in it’s original form tried to boil the ocean, and the result might have been too much change too fast for the networking community to handle in such a fundamental area of the stack. What engineering lessons might we draw from the long times scales around IPv6 deployment?

For those who weren’t in the industry those many years ago, there were several drivers behind IPv6 beyond just the need for more address space. For instance, the entire world exploded with “no more NATs.” In fact, many engineers, to this day, still dislike NATs, and see IPv6 as a “solution” to the NAT “problem.” Mailing lists roiled with long discussions about NAT, security by obscurity (still waiting for someone who strongly believes that obscurity is useless to step onto a modern battlefield with a state of the art armor system painted bright orange), and a thousand other topics. You see, ARP really isn’t all that efficient, so let’s do something a little different and create an entirely new neighbor discovery system. And then there’s that whole fragmentation issue we’ve been dealing with for IPv4 for all these years. And…

Part of the reason it’s taken so long to deploy IPv6, I think, is because it’s not just about expanding the address space. IPv6, for various reasons, has tried to address every potential failing ever found in IPv4.

Don’t miss my point here. The design and engineering decisions made for IPv6 are generally solid. But all of us — and I include myself here — tend to focus too much on building that practically perfect protocol, rather than building something that was “good enough,” along with stretchy spots where obvious change can be made in the future.

In this specific case, we might have passed over one specific question too easily — how easy will this be to deploy in the real world? I’m not saying there weren’t discussions around this very topic, but the general answer was, “we have fifteen years to deploy this stuff.” And, yet… Here we are fifteen years later, and we’re still trying to convince people to deploy it. Maybe a bit of honest reflection might be useful just about now.

I’m not saying we shouldn’t deploy IPv6. Rather, I’m saying we should try and take a lesson from this — a lesson in engineering process. We needed, and need, IPv6. We probably didn’t need the NAT wars. We needed, and need, IPv6. But we probably didn’t need the wars over fragmentation.

What we, as engineers, tend to do is to build solutions that are complete, total, self contained, and practically perfect. What we, as engineers, should do is build platforms that are flexible, usable, and can support a lot of different needs. Being a perfectionists isn’t just something you say during the interview to that one dumb question about your greatest weakness. Sometimes you — we, really — do need to learn to stop what we’re doing, take a look around, and ask — why are we doing this?