[net2-wg] CTP and interoperability

[Philip Levis]

I'm thinking through how to get CTP interoperability, and I think  
there's a snag. Specifically, I think that the CTP TEP needs to talk  
about the link estimator.

The reason is this: currently LinkEstimatorP works directly on top of  
AM. This means that it occupies an AM ID, which is, in theory, the  
CTP routing beacon ID. There's nothing in the packet that says whether
it has LinkEstimation information in it. Therefore, I think that CTP  
is bound to the LinkEstimator. If, in contrast, the LinkEstimator had  
a specific AM id, and then we could dispatch onto the routing ID.

But I know that one consideration for CTP is that it should be able  
to work on any routing topology;
the specification says nothing about how routes are selected. Why  
should there be link estimation packets
  if there is a hardcoded topology?

All together, I think this means we need to tweak the link estimator  
slightly. It needs to be assigned an AM ID and have a higher-level  
dispatch. I'd like to propose we name the link estimator SLEEP, for  
"Simple Link Estimation Extension Protocol," where Extension comes  
from the fact that it adds footers.

This came up because Sun has expressed some initial interest in  
porting CTP to the SPOTS, and I wanted to figure out how best to  
explain the parts.

Thoughts?

Phil