[RRG] arguments for map and encap

[Michael Meisel <meisel@cs.ucla.edu>]

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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