General

The 6bone Connected Makes A Backbone

Short for IPv6 backbone, 6bone is an experimental worldwide network built to test interconnectivity among adopters. As a IPv6 testbed of the IETF IPng project that created the IPv6 protocols, 6bone is a reality check to see if IPv6 is really connected to the backbone.

by Jim Thompson [September 11, 2001]

While many debate whether or not to deploy IPv6, more than 900 network sites in 52 countries have been actively working with the protocol in a real world environment through the 6bone. For more than five years the 6bone has been the standard bearer of the next generation protocol and provided a test-bed for its evolution and deployment.

The 6bone debuted in March 1996 as a virtual network backbone using IPv6 over IPv4 tunneling encapsulation but evolved to incorporate native links for IPv6 transport.

"The overall goal of the 6bone is to act as a testing ground for new code and to test various standards features to detect any flaws," said Bob Fink, researcher at the Energy Sciences Network at Lawrence Berkeley National Laboratory and one of the creators of the 6bone.

Although testing is still an essential part of the backbone, it quickly became apparent to its creators that this was only a part of what had to be done. They needed to provide a real world environment that was reliable, stable and safe if the protocol was to have a chance of becoming the standard for the Internet.

Prolonging revelations
"We went from being a random distributed mesh of tunnels between various research and development test networks to a backbone hierarchy, which is more consistent with the way the public Internet runs," noted Fink. "We identified people who were operationally oriented and could guarantee they have a backbone that will survive and be reliable. We called them PTLAs or Pseudo Top Level Aggregators. The pseudo is because we are a test network and pretending to be production ISPs."

One of the main objectives of the 6bone is to assist ISPs migrating toward IPv6 implementation, so ISPs can build market share rooted in the protocol as an enabling technology. As the need for IP addresses increases and the supply decreases, ISPs are coming to grips with the need to understand IPv6 and are beginning to build the new standards into their networks.

According to current estimates, while there are some six billion people in the world, IPv4 provides only 4.3 billion unique Internet addresses. Many see the day when everyone on the planet will need not one but several IP addresses for such things as cell phones, PDAs, automobiles and even home appliances.

According to one estimate, IPv6 will resolve the address shortage issue by providing 340 billion billion billion billion Internet addresses. That's the equivalent of 67 billion billion addresses per square centimeter of the planet.

Quintessential IPv6 fount
Today, the 6bone is the prime source for anything involving IPv6. "At first, you had to search for someone to tunnel to on the 6bone," Fink said. "Today you just identify a backbone provider and let them worry about all the background routing. The 6bone is very similar to the IPv4 Internet with a backbone architecture."

The 6bone is growing rapidly. There are currently 80 to 90 networks worldwide that act as a backbone, Tier-1 ISPs for the 6bone. It's a three-level hierarchical network with backbone, transit, and leaf nodes made up of an interconnected mesh of IPv6 over IPv4 tunnels and direct links.

IPv6 routing inside the backbone is based on the BGP4+ protocol. Transit nodes connect to one or more backbone nodes and provide transit service for leaf sites.

IPv6 addressing inside the 6bone is based on IPv6 aggregatable Global Unicast Address Format. Since 1999, the international address registries began issuing production IPv6 addresses which 6bone calls sub-Top Level Addresses (sub-TLA).

Arduous assignment
Running the backbone and coordinating the activities between the participating members and end-sites is not an easy task. As Fink noted, "It's difficult because the Internet is running along like a Formula One Grand Prix race car and here we are trying to change its engine while it's on the track. It's sometimes a bit scary."

He added that they enforce a rigid application process for IPv6 address space in order to insure the integrity of the backbone. "You need three months of experience running as an N node," commented Fink. "Next you fill out an application and go through a peering evaluation process before you get your PTLA. The people who get the PTLA are serious players."

Membership in the 6bone is open to virtually everyone and there are no fees for joining. About all you need is a BSD, Linux or Windows NT system set-up as an end-site and permission for a tunnel to another member. Full information on 6bone and how to become a member can be found at 6bone.net. "The 6bone is a wonderful way for anyone to work with IPv6 safely, cheaply and easily. It's the place where the trainers are trained," Fink concluded.

—End