Start talking to someone about IPv6 and before you know it, it often feels like the Cone of Silence has descended upon you. The Cone of Silence, for those who haven’t seen the “Get Smart” movie or vintage TV shows, looked like a huge hamster ball cut in half and was meant to isolate conversations between secret agents from eavesdroppers but instead just made it harder to understand each other.

I’m not implying that there’s anything top secret about IPv6. The problem is that it’s hard to have a discussion about it without it turning into a high-tech version of the Abbott & Costello “Who’s on First?” routine.

I was reminded of this when I talked this week with Owen DeLong, who has the intriguing title of IPv6 evangelist for Hurricane Electric, an Internet backbone provider that has been particularly aggressive in deploying IPv6. DeLong and I have talked before and I’ve always enjoyed it because he is very knowledgeable about this topic and can answer questions that others can’t—provided that the question is precisely posed and thoroughly understood.

I wanted to get DeLong’s insight on recent IPv6 initiatives from service providers such as AT&T and Comcast. “I heard they’ve been assigning IPv6 addresses, but don’t customers have trouble reaching everywhere they want to go?” I asked DeLong.

Suddenly the Cone of Silence seemed to descend. I don’t remember what DeLong’s answer was, only that it didn’t make sense to me.

Then he cleared it up. With service providers such as AT&T and Comcast, he said, “People that are getting IPv6 are getting it as an additional parallel service; they’re not getting moved from IPv4 to IPv6.” Accordingly they have no problem reaching either type of endpoint. I had assumed, incorrectly, that customers were getting IPv6 addresses instead of IPv4 addresses.

Aha! Now it all made sense.

But it shows how careful you have to be about the assumptions you and the person you are talking to make about IPv6 or you can easily get off on the wrong foot. And the topic is so complex that it’s not so easy to avoid that. You can’t say something like “supports IPv6” without clarifying what you mean by that. Do you mean IPv6-only or IPv4 and IPv6? And what kind of support are we talking about? The customer premises equipment? The network? And is that the backbone network or the end-to-end network?

As DeLong explained, network operators such as AT&T and Comcast are deploying dual stack technology, which enables IPv4 and IPv6 to operate essentially side by side, beginning in the core and moving toward the edge. As the technology gets to a neighborhood node, the network operator turns up dual stack capability for everyone served from that node. DSL or cable modem customers whose premises equipment supports only  traditional IPv4 connectivity will continue to be able to only reach other IPv4 endpoints but customers whose CPE supports both types of connections and who have the dual addresses will be able to reach both types of endpoints. New customers apparently get—or at least have the option of getting—the requisite CPE and dual addresses.

Some Asian carriers, including China Netcom and China Telecom, are not fortunate enough to have such an ample supply of IPv4 addresses, said DeLong. Accordingly at least some of their new customers get IPv6 addresses only and can only reach endpoints supporting IPv6. DeLong noted that many of these customers are getting Internet connectivity for the first time and therefore may be less aware than some others of what they are missing.

I asked DeLong how soon U.S. carriers would face the same circumstances and he said he had no idea. He said it would depend on a variety of factors, including how many IPv4 addresses each carrier has stockpiled.

He also declined to speculate how soon other U.S. carriers will be following AT&T’s and Comcast’s lead in supporting end-to-end IPv6 (plus IPv4) capability. His opinion is that it’s a stretch to call what AT&T and Comcast are doing “super proactive and wonderful.”

Noting that dual stack technology has been available to network operators for years, he said, “Comcast and AT&T are less late to the party than most others.”

So what will happen when U.S. carriers finally do have to start assigning only IPv6 addresses? That depends on how widely IPv6 is supported on endpoints worldwide by the time that occurs. To fill in any gaps that may continue to exist, some carriers are looking to implement carrier-grade network address translation as a means of enabling IPv6-only endpoints to reach IPv4-only endpoints. But as DeLong explained, developers working on that solution are encountering numerous challenges.

More on that next week.