Taking a detour from IPv4

After working on the new Internet Protocol version 6 (IPv6) for a decade and a half, the Internet Engineering Task Force decided it was time to turn off the old protocol (IPv4 or just IP). So this is what they did for an hour on the network used at the IETF meeting in Philadelphia this week. Network traffic plummeted from some 30Mbps to around 3Mbps as the meeting attendees who had IPv6 enabled could now only get at IPv6-reachable destinations on the Internet. Leslie Daigle, chief Internet technology officer for the Internet Society, who coordinated the IPv4 outage, considers the outage a success.

"The plenary outage provided a focal point for a number of people to dive into and work with IPv6—whether on their own notebooks, or their home web sites (e.g., Paul Hoffman's www.vpnc.org), or their products (ISC's BIND), or public services, such as Google," said Daigle. "From that perspective, the experiment was a success before we even turned off IPv4 access in the plenary session. I hope, though I don't know, that the plenary event also provided a first hand experience to more IETF engineers that they can take into Working Group discussions."

Shortly after the fall meeting, the IETF leadership decided to create an "IPv4 outage" during this week's spring meeting. The triannual IETF meetings attracted some 1,200 Internet engineers from around the globe who attended meetings in parallel tracks all week except for the plenary sessions on Wednesday and Thursday evenings. Power cables ran throughout the meeting rooms to power the laptops that everyone used to alternatively enhance participation and zone out.



IETF attendees bracing themselves for the loss of IPv4

A huge wireless network provided connectivity to the attendees. The Philadelphia meeting was hosted by Comcast, which provided a 100Gbps connection with a 10Gbps backup and a 100Mbps backup for the backup. For years now, the IETF meeting network has supported both IPv4 and IPv6. During this meeting, there was also a separate IPv6-only wireless LAN. Yesterday evening, shortly before 7 PM, the mixed IPv4/IPv6 network was turned off, forcing the IETF to proverbially eat its own dog food and talk to the world outside the meeting hotel through the remaining IPv6-only network.

IPv6 and your favorite OS

In the past year or so, most, if not all, of the IETF's web sites have been IPv6-enabled. So having a look at the meeting agenda or looking up RFCs was not a problem for those with IPv6 connectivity. Beforehand, the IPv4 outage wiki had collected instructions on how to configure IPv6 on various operating systems. Windows Vista and some Linux distributions were able to take advantage of the IPv6 connectivity without further configuration because they support the IPv6 version of the DHCP protocol. Mac OS X will automatically use IPv6 connectivity if it's available, but it doesn't support DHCPv6, which makes it necessary to manually configure an IPv6 DNS server address. The same is true for many UNIX/Linux systems. On Windows XP, things are not quite as simple as that—XP not only lacks DHCPv6 support and doesn't have IPv6 turned on by default, it also can't perform DNS lookups over IPv6. The solution is to run a nameserver locally that can be queried over the IPv4 loopback address, but that turned out to be easier said than done. In the end, a number of XP users "cheated" by having a local-use-only IPv4 address to talk to a DNS server that in turn translated DNS names into IPv6 addresses.

After everyone got his or her system up and running, many people started looking for IPv6-reachable web sites, reporting those over Jabber instant messaging—which posed its own challenges in the IPv6 department. I was surprised at the number of sites and wide range of content available over IPv6. Apart from—obviously—IPv6-related sites; they ranged from "the largest Gregorian music collection in Internet" to "hardcore torrents."