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Linux Gets Improved IPv6 Multihoming Support

Jul 22, 2008, 08:00 (0 Talkback[s])
(Other stories by Olivier Bonaventure)

[ Thanks to Olivier Bonaventure for this link. ]

The Internet architecture was designed in the 1970s as a small internetwork to serve the needs of researchers. For the last 30 years, the Internet continued to grow and we are now getting close to hitting the limits of the 32 bits IPv4 addressing space. During the last decade, the Internet Engineering Task Force has been designing IPv6 as a replacement for IPv4. Most of the initial benefits of IPv6 (security, QoS, autoconfiguration, ...) have been ported to IPv4 and IPv6 deployment has been limited.

However, thanks to the huge IPv6 addressing space, it is possible to design protocols and mechanisms that are more scalable and more powerful than with IPv4. A typical example is the multihoming problem. This problem occurs when a site is attached to several Internet Service providers. With IPv4, the classical solution is for the site to obtain one IPv4 prefix and advertise it by using BGP. This solution works and traffic engineering is possible, but unfortunately, it contributes to a significant growth of the BGP routing tables in the global Internet. With IPv6, many different solutions have been discussed within the IETF. Eventually, the IETF decided to focus on a host-based technique. Basically, when a site is attached to n providers, each of its hosts will receive n different IPv6 addresses. This reduces the size of the BGP routing tables by avoiding to advertise the IPv6 prefixes used by the stub domains and provide many additional benefits in terms of path diversity or performance. However, this requires the implementation of new protocols and mechanisms to coordinate the utilization of the different IPv6 addresses by each host, avoid security problems and efficiently detect failures.

Now that the shim6 standardization is being finalized by the IETF, it is time to validate this approach experimentally in the IPv6 Internet. Sebastien Barré has developed the first publicly available implementation of the shim6 IPv6 host-based multihoming on the Linux kernel:

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