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[RRG] arguments for map and encap



In their earlier post (http://www.ops.ietf.org/lists/rrg/2008/msg01159.html), the RRG co-chairs requested that we first come to a consensus on the "highest-level branches of the decision tree". Towards that goal, Dan Jen and I want to open a discussion on this issue with some arguments for choosing the map & encap branch.

First, some background. We know the fundamental reason that the current routing system doesn't scale: there is a conflict between network customers and their transit-network providers. It is in the interest of network users to have provider-independent (PI) addresses, while it is in the interest of network service providers to maintain IP address aggregatability.

So what the RRG is tasked to decide is: what changes should be made to resolve this conflict?

We believe that the answer is to take a path that (1) best resolves the conflict for the long term and also (2) provides a feasible economic incentive to make the changes.

1. Selecting the best long term solution.
The Internet as it stands is a great success. We want to first make changes that are in the best long term interest. Faced with equally good long term changes, we should also select the one with the highest degree of backwards compatibility.

2. Ensuring that parties required to make changes have incentive to do so.
For any solution that does not align cost with benefit, it may be possible to deploy it in a few places, but the solution will not be widely adopted unless the economics are on the right side.

This means we cannot expect everyone to change operations. It is reasonable to ask each ISP to make a big change, but only if they can see some appreciable benefit. Conversely, it is not reasonable to ask all home users to change in order to better accommodate ISPs. The scaling problem is perhaps felt most profoundly at the ISPs, so fixing the problem by making changes at all ISPs seem more reasonable. Forcing changes upon all network customers would need to be matched by a compelling gain for those customers.


Arguments for Map & Encap

For a long term solution, we believe some decoupling of the network customers and transit networks is necessary. The conflict over PI addresses is a clear example of the need to decouple. In the long term, it also opens up a number of new possibilities at both sides for scaling and routing changes in the core and techniques to exploit mapping service for new features at the edges.

As compared to other types of schemes, map & encap requires changes only to the nodes at the borders (where encap/decap occurs), along perhaps with a small support infrastructure. No changes are required at end hosts who benefit only indirectly from the change -- in fact, map & encap schemes can be made invisible to end users (and edge networks in general, if desirable).

Service providers, both large and small, are the parties that stand to benefit from a resolution to the conflict. Thus, they should be the ones who bear the burden of deployment. Thus, map & encap seems to be the solution that best aligns cost with benefit, as well as the best long-term direction going forward.

-Michael and Dan

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