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Re: Why is IPv6 a must?

2001-11-12 14:00:03


Quite simply, a bunch of us *are* searching for a paradigm shift. Geoff's good work in this area reveals the complexity of the whys and wherefores of the routing system. Given that 8+8 was a serious consideration (and to some deserves some amount of revisiting -- at least as a starting point), I don't believe we can say that the deployment of v6 is completely divorced from the routing system. 8+8 is merely an existence proof of how the routing system and v6 can be intertwined, for better or worse.

As I tried (probably poorly) to indicate in my last posting on this topic there are a number of different directions you can take when searching for a lever to use to handle scaleable routing. Our recent experience with V4 using an address-based hierarchy tends to indicate that the hierarchy leaks - i.e. attempting to align the structure of the network into a hierarchy and aligning addresses to conform to this same hierarchy is not an easy task and it tends to break down in the face of increased interconnectivity at the edge (multi-homing) and in the middle (peering and multi-transits). If you look away from an address -based hierarchy and define other objects as the 'atoms' of a routing system then there may be some benefit. Even today, with some 105,000 objects in the routing table (*) there are only some 12,000 AS's (*) and 15,500 AS paths selected (*). This tends to indicate that grouping addresses not by bit boundaries, but by origin AS's has some potential, in my view (*). If you take this AS-based perspective the issue of V4 / V6 tends to be less important than if you take an address hierarchical perspective. I note the AS-based approach to hierarchies as an example - there are other ways to look at the network that also provide some tractable level of grouping that could make interdomain routing scale. The point is that the degree to with the inter-domain routing issue is intrinsically liked to the address structure within the protocol depends on the approach used by routing. Some approaches, like an AS-based approach, attempt to bypass an effort to structure the address space as the aggregateable element of the routing system, and the corollary is that the approach has pretty much the same leverage in a V4 world, a V6 world, or a heterogeneous world.

   Geoff


* Your mileage may vary.



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