RE: The state of IPv6 multihoming development

["Tony Hain" <alh-ietf@tndh.net>]

Iljitsch van Beijnum wrote:
> ...
> Actually holes in PA space is perfectly fine for the network, as you 
> can filter the more specifics and still have connectivity.

This statement is self contradictory. 

> However, it is not so great for the
> organization using the addresses since this doesn't address
> all failure modes.

The point I was making about punching holes in PA is that the more
influential organizations will get the full prefix routed globally.

> 
> We did discuss this proposal at length on a different mailinglist. My 
> view was that it needs to address the problem of address density at 
> the poles

Over-engineering the approach doesn't accomplish the goal. 

> and the fact that the
> aggregation boundaries don't fit either topology or
> geography. 

By geography, I assume you mean geo-political agreements. It clearly
matches the global coordinate system those agreements are based on.

> This could be done by having several instances of
> this address space and have two places that would otherwise
> be aggregated together sit in a different instance. By 
> rotating the axes and limiting everything to (say) from -60 
> to +60 degrees you eliminate the pole problem.

I played with rotating the axis, but the only thing that made Europe
contiguous was to put the origin on a 22.5 degree mark. This would
unnecessarily complicate the rest of the world, for the simple gain of
reducing the London prefix set from 2 to 1. If it were 20 to 1 I would
reconsider, but I don't see how a single prefix makes it worthwhile.
Also, setting the boundaries at +/-60 does nothing useful in terms of
available address resolution. You would have to restrict it to +/-45 to
get a bit back, and that is clearly not a wide enough band.

> 
> Still, there is one unanswered question: what problem is solved by 
> having such a close relationship between geography and address space?

I was not trying to force any particular alignment. The goals were: 
Uses current BGP protocol. 
Aggregate the basement-multi-homer, while recognizing the CNN's of the
world will always get a full prefix announced. 
Decouple the scale of aggregation, so it becomes a regional decision. 
Make it simple to derive by basing it on a globally consistent
reference.

The use of WGS84 was based on the fact that handheld receivers are cheap
and available, so the L1 installer can easily identify the reference
point. Bit-interleaving the result decoupled the aggregation scale
decision when using current BGP prefix exchanges.

Is it the most efficient use of address space? No, and the document
recognizes there is a clear trade-off being made between simplicity and
efficiency. Are there other ways to achieve the listed goals? Probably,
and when I see something that looks more operationally viable I will
back off. 

Tony