We posed a few questions to Russ Housley, chair of the Internet Engineering Task Force, about why the standards body is developing network address translations for IPv6 when IPv6 was supposed to eliminate the need for NATs on the Internet. Here's what Housley had to say.

The IETF has four working groups looking at NAT mechanisms for IPv6. How important is this work compared to other development efforts facing the IETF?

For the Internet to continue growing, the bigger address space offered by IPv6 is needed. The original designers of IPv6 expected every host and router to begin running both IPv4 and IPv6 several years ago. This strategy would have resulted in a gradual transition, with all hosts and routers being able to use IPv6 long before IPv4 address allocations became a problem. However, the economic incentives were not in place to encourage IPv6 implementation and deployment. As a result, we need the capability to translate between IPv4 and IPv6 until every host and router supports IPv6.

Isn't it ironic that the IETF is developing NAT mechanisms for IPv6 when IPv6 has been touted for years as a way of ridding the Internet of NATs?

Yes. I expect the address translation between IPv4 and IPv6 to be deployed at different places in the Internet than we have seen strictly IPv4 NAT. Further, the desire is for these NAT devices to be needed only during the transition period. That transition will certainly not be quick, but when it is over, the need for NAT should go away.

Are NATs for IPv6 a necessary evil?

They are necessary for a smooth transition from IPv4 to IPv6 so that the important properties of the Internet are preserved.

How would you characterize the debate within the IETF about NATs for IPv6?

The engineers and computer scientists that make up the IETF wish that the original plan had come to pass. But, of course, it didn't. Given the current situation, the IETF participants are seeking a pragmatic solution, and there is rough consensus that this is the best way forward.

What's the timeframe for the various IETF working groups to develop one or more new NAT mechanisms for IPv6? How fast does the Internet need this work done?

Everyone has a different crystal ball. However, my view is that the IETF needs to have a specification ready for development and deployment in the next year or two.

Is this NAT-for-IPv6 issue going to be one of the hotter topics at the IETF meeting in Dublin? What other topics will be hot?

Certainly. Three other things jump to mind. First, VoIP continues to generate a lot of interest. Second, MPLS is getting a lot of attention. Third, the IETF is considering new work on peer-to-peer infrastructure.