Dissertation Defense

Virtual Circuit Provisioning in Challenged Sensor Internetworks:
with Application to the Solar System Internet

Ed Birrane

10:00am-12:00pm Monday, 11 August 2014, ITE325b

In this thesis, we present a challenged sensor internetwork (CSI) networking architecture which federates heterogeneous constituent networks behind an overlay routing mechanism abstracted from individual data link layers. The CSI is unique and required to implement expanding sensor networks.

Demand for sensing networks with increasing spatial footprints is evidenced by ongoing efforts to build geo-political border monitoring networks, intelligent highway initiatives, automated undersea surveillance, and NASA effort to construct a Solar System Internet. Existing network technologies fail to address multiple physical links, frequent disruptions, and significant signal propagation delays. The construction and maintenance of virtual circuits in an internetwork abstracted from differences in the physical, data-link, and transport layers of an internetwork represents a unique research contribution with immediate utility for a wide variety of sensing network concepts.

We describe the CSI architecture as the intersection of wireless, delay-tolerant, and heterogeneous networks and describe special characteristics of this architecture than enable useful assumptions to optimize messaging. We define an internetwork routing (INR) framework that decomposes the routing function into discrete logical steps and we provide algorithms for each of these steps. An inferred Contact Graph Routing (iCGR) algorithm populates logical graphs from local nodes. A Contact Graph Routing with Extension Blocks (CGR-EB) algorithm provides a hybrid source-path algorithm for synchronizing link state along network paths. A Predictive Capacity Consumption (PCC) algorithm exploits CGR-EB data to build a congestion model. Payload Aggregation and Fragmentation (PAF) and Traffic-Shaping Contacts (TSC) algorithms condition data and place limits on the amount of internetwork traffic carried over local networks.

From simulation, iCGR performs within ~15% of a perfect-knowledge system. CGR-EB has a speedup over standard approaches by 300% in stable topologies, by 3000% in unstable topologies, and by 11000% in unstable topologies with non-monotonic cost functions. PCC delivers 97% more data in congested networks over table-based approaches and 37% more data than the INR framework without the congestion model. PAF/TSC reduces message count by 43% while increasing goodput by 63%.

Together, these algorithms build and monitor virtual circuits in the CSI architecture. Portions of this work are in consideration for deployment in NASA networks.

Committee: Drs. Alan Sherman (Co-Chair, UMBC), Mohammed Younis (Co-Chair, UMBC), Dhananjay Phatak (UMBC), Vinton Cerf (Google), Keith Scott (MITRE), Hans Kruse (OU)

Erle Ellis, Geography and Environmental Systems, was recently quoted in the Nature article written by Virginia Gewin, Science and politics: Hello, Governor.

“Although there is little disagreement that abrupt shifts occur in Earth systems, including climate and the composition of ecosystems, some scientists baulk at the suggestion that there is enough evidence to predict a single tipping point for the whole planet. “I thought it was a great review of the evidence for rapid shifts in ecology, but then it switched to a series of unsupported statements — at best a hypothesis — about how a global tipping point in the biosphere could happen,” says Erle Ellis, a landscape ecologist at the University of Maryland, Baltimore County, who was involved in a response to the paper.

Yet Ellis understands why the term appeals to politicians. “It’s an extraordinarily simple way to look at human-induced global change. It effectively creates a binary Earth; a line drawn in the sand,” he says. “Doing so gives a false sense of security on the ‘safe side’ and a false sense it is too late to act on the other.” But the concept has power. In fact, game-theory simulations have shown that the kind of coordination needed to solve global environmental problems is much easier to achieve if a tipping point can be predicted with high certainty.”

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Virginia Gewin writes in Nature, about diversity in science and the problems facing minorities in science. Gewin writes that, Neil deGrasse Tyson has suggested that the low numbers of minorities and women in the US science workforce are due in large part to a lack of equal access to opportunities for entering that workforce.

“To solve that problem, universities are now looking to the example of the Meyerhoff Scholars Program at the University of Maryland, Baltimore County (UMBC). It has crafted a formula for mentoring students from minority groups underrepresented in the sciences and helping to guide them into science, technology, engineering and maths (STEM) careers. And that formula seems to work — African American Meyerhoff scholars are five times more likely than their counterparts at other US universities to pursue STEM PhDs (K. I. Maton et al. Mt Sinai J. Med. 79, 610–623; 2012).”

“Now, with US$7.75 million in funding from the Howard Hughes Medical Institute (HHMI), Pennsylvania State University (Penn State) in University Park and the University of North Carolina at Chapel Hill (UNC) are trying to replicate the programme, which for two and a half decades has led the nation in the number of its minority graduates who go on to earn STEM PhDs.”

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