[SensorNetArch] draft slides for friday

[Philip Levis]

A couple of points on the functional architecture:

Although the proposal claimed broadcast would be the primitive, it 
isn't in the SP that Joe will present. Certain link technologies 
prevent broadcast from being the lowest common denominator. That is in 
and of itself an interesting finding and worth bringing up.

SP is not exactly a narrow waist in the same way that IP is. Among 
other things, it isn't a protocol, but rather a systems abstraction. 
Two systems running SP on top of the same data link layer are not 
necessarily interoperable, unless they also use the same SP 
implementation. Due to the ways in which sensor networks are deployed 
and developed (generally single administrative domain), this is OK. It 
just needs to be made clear that while we're using the same term, it 
has a different meaning.

Slide 23: The formation and management of the connectivity graph (sec 
4.3 in the proposal) is essentially the SP neighbor table. The fact 
that we've moved it into SP is an interesting finding and worth 
bringing up.

Slides 26-7: We spent a whole bunch of weeks discussing cross layer 
services and what they mean. Much of SP came out of taking a hard look 
at power management with regards to communication (Joe and Jonathan's 
first cut on Deluge). Putting some of our progress here would be nice: 
right now it mostly restating the proposal.

A bit of an observation: defining a unifying abstraction is inherently 
at odds with the notion of cross-layer services. For example, SP can 
provide feedback to a routing layer on how it could improve energy 
efficiency (phase, etc.): how does the routing layer then convey this 
information to the application which is sending data? Do the notions of 
SP -- an abstraction *between* two layers, defining the control and 
feedback -- push up to successive layers? It would seem the inevitable 
conclusion...

Phil

-------

"We shall not cease from exploration
And the end of all our exploring
Will be to arrive where we started
And know the place for the first time."

- T. S. Eliot,  'Little Gidding'