Policy Routing Usage

All of your testing with IPv6 to this point has concentrated on the basics of standard IPv6 networking. As you went through the various tests you wondered whether additional structures were available under Policy Routing. The true answer to that question at this point in time is a definite maybe.

The current IPv6 implementation within the Linux kernel, and those of other IPv6 implementations , concentrate on providing a usable networking base for core IPv6 networking functions. While the theory and practice of Policy Routing provides many instances within IPv4 networking that are easily extensible to IPv6, IPv6 still exists mostly in a beta test period.

As you read through the RFCs defining IPv6, IPSec, and the related structures of the future Internet, you will see that the fundamentals of these protocols contain many practices grown within Policy Routing. The notion of addressing as providing a multiple source for service location provides one of the concrete examples of the integration of Policy Routing structures into IPv6.

IPv6 provides a shining example of integration and growth through cross-pollination. As time passes and the entire spectra of protocols comprising the new Internet solidify through practical use you will see more of the core routing structures and extensions as evidenced by Policy Routing under IPv4 appear in IPv6. After all, you must remember that IPv4 was initiated in the early 1980s and only in the mid 1990s did Policy Routing structures begin to change the face of the Internet. The IPv6 Internet is not even a full reality yet.

Indeed, at the time of this writing in late 2000, a commercial IPv6 offering is available in Japan. Parts of Europe and North America are rumored to perhaps have IPv6 commercial availability as soon as January 2001. And this does not even take into consideration the 6bone (http://www.6bone.org) or 6ren networks, which are available today to interested parties. There is even an IPv6 implementation of the NetFilter packet filtering available in the Linux 2.4 kernel. It even includes a fwmark facility, although the RPDB cannot currently support IPv6.

This brings up the core reason why there is not an IPv6 Policy Routing structure within Linux today. Essentially, the RPDB replaced the IPv4 routing and addressing structure within the Linux kernel (see Chapter 3, "Linux Policy Routing Structures" ). The IPv6 structure within Linux was implemented outside of that core structure. Although they do share some facilities, the essential RPDB structure does not participate in or with the IPv6 addressing and routing structures. This will change, although it probably will not be until the 2.5 development kernel series slated to fork in early 2001.

Until then you have much to play with in your Policy Routing structures. The current IPv4 Internet will exist for at least another five years . And because the two network structures are coexistent, there will be use for many of the structures for some time to come.

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