Comcast and Internet Systems Consortium announced on Thursday the availability of open source software that will help carriers and enterprises migrate to IPv6, the long-anticipated upgrade to the Internet's main communications protocol.

Called Address Family Transition Router (AFTR), the software is available immediately and free of charge to network engineers who want to experiment with this IPv6 transition mechanism. AFTR version 1.01 can be downloaded here.  

The Internet industry needs transition mechanisms like AFTR because the Internet is running out of address space with its current protocol, called IPv4. IPv4 uses 32-bit addresses and can support 4.3 billion devices connected directly to the Internet. Experts predict that the remaining IPv4 addresses will be distributed in 2012. In January, the Regional Internet Registries announced that fewer than 10% of IPv4 addresses remain unallocated.

When IPv4 addresses run out, carriers and enterprises will need IPv6, which uses 128-bit addresses and supports a virtually unlimited number of devices. IPv6 deployment is picking up momentum in the United States, with carriers such as Comcast, Hurricane Electric, NTT and Global Crossing leading the charge.

Comcast is trying to generate interest in IPv6 with the release of the AFTR software that it developed in conjunction with ISC.

"We plan to continue working with ISC on this open source implementation," says Richard Woundy, senior vice president of software and applications for Comcast. "Our hope and our expectation is that others in the Internet community will take a serious look at this technology, try it out, and provide their feedback."

AFTR enables a user whose computer, printer, gaming system or other Internet-connected device supports IPv4 to access IPv4 content and services over an IPv6-based network. AFTR is the first open source implementation of an emerging standard called Dual Stack Lite that was developed by Comcast.

Dual Stack Lite allows multiple customers to share a single IPv4 address using carrier-grade network address translation (NAT) along with IPv4-to-IPv6 tunneling from the customer's gateway to the carrier's NAT. Dual Stack Lite is being standardised by the Internet Engineering Task Force, with approval as a proposed standard expected later this year.

Comcast will begin a trial of three different IPv6 transition mechanisms including Dual Stack Lite in April. Comcast and ISC developed an open source version of Dual Stack Lite because they wanted to define the concept, provide a reference implementation to the Internet engineering community, and allow users to test it.

The open source version "can stand alone as its own software implementation and answer lots of questions people had early on about how Dual Stack Lite would work in practice in ISP networks," Woundy says. "There were lots of questions about what is this technology really doing behind the scenes and what's happening with the packets because now the ISP is involved in a [network address translation] operation."

Comcast and ISC have been collaborating on Dual Stack Lite for two years, says Alain Durand, Director of IPv6 Architecture and Internet Governance at Comcast.

"In the last six months, we have had a number of discussions with other carriers around the world about this open technology," Durand says, adding that a beta version of the AFTR software has been available for four months. "There have been telcos… in France, in Germany and in Japan that have started experimentation with the beta code."

Durand says he knows of five commercial implementations of Dual Stack Lite that are under development, but that AFTR is the first open source version being released to the Internet community at large.

ISC is gearing up for carriers, government agencies, equipment vendors and enterprises to download and test the AFTR software.

"The most obvious use case [for AFTR] is carriers because those are the ones that are running out of IPv4 addresses," says Suzanne Woolf, manager of strategic partnerships for ISC. "But a lot of enterprises are not that different from carriers in terms of what they have to do to operate their networks. There may be enterprises that discover that they have these cases where interoperability between legacy IPv4 devices and IPv6 networks is required."

Woolf says the current version of the AFTR software is ready for test labs and small scale deployment.

"The road map for the future calls for more advanced usability features and management infrastructure for the kind of scalability that people will need over the long term," she says. "The initial release is not as much aimed at large-scale production use in that it will require a certain amount of administrative [work.]"

Woolf says she is optimistic that AFTR will be a solid product for ISC, which also supports open source versions of DNS and DHCP software.

"One of the reasons we were excited to be working on Dual Stack Lite is that both the product and the protocol are relatively simple and straightforward," she adds. "It's not hard to figure out what it does and doesn't do, and for the most part it just works."