# Projects & Publications

## **Current Projects**

**Evaluation of software defined networking (SDN) for communication and control of cyber physical systems**

In the current work, we use a simulative approach to develop methods for designing robust networks and evaluate software defined networking for communication and control in cyber physical systems, where the smart grid is the system under consideration. The network technology, OpenFlow, along with other simulation software (THYME and NS3) is being used in the simulations for the smart grid to monitor the system frequency and take the necessary action if there is a frequency deviation, such as, monitoring generator speeds, transmitting these speeds to a control center where they are processed, and then issuing actuation commands to increase or decrease the power consumed by loads in order to increase or decrease the frequency. The effectiveness of OpenFlow is compared with that of MPLS on the basis of final voltages in the power network, the average frequency variation for the generators, the amount of load that is adjusted, and throughput and latency in the communication network. These measurements are done with and without background traffic in the communication network, as well as by varying the bandwidth of some links in the network.

**Publications**

**Spreading Processes over Multilayer and Interconnected Networks**

This project advances the boundaries of network theory by analyzing spreading processes over multilayer and interconnected networks, which abound in nature and man-made infrastructures, and about which many interesting questions remain unanswered. Multilayer networks are an abstract representation where multiple types of links exist among nodes. Interconnected networks are an abstract representation where two or more simple networks, possibly with different and separate dynamics, are coupled to each other. The rationale for this project is that viral-spreading dynamics over multilayer and interconnected networks exhibit behaviors that cannot be attributed to single-network characteristics and play a highly relevant role in practice. This project uses rigorous mathematical tools from network science, spectral graph theory, nonlinear dynamics, stochastic processes, controls, game theory, and optimization.

**Publications**

Darabi Sahneh F., Scoglio C., Van Mieghem P., "Generalized Epidemic Mean-Field Model for Spreading Processes over Multi-Layer Complex networks (pdf)," IEEE/ACM Transactions on Networking, 2013, to appear.

Darabi Sahneh F., Chowdhury F., Scoglio C., "On the Existence of a Threshold for Preventive Behavioral Responses to Suppress Epidemic Spreading," Nature Scientific Reports, Vol 2:632, 2012.

Darabi Sahneh F., Scoglio C., and Chowdhury F. N., "Effect of Coupling on the Epidemic Threshold in Interconnected Complex Networks: A Spectral Analysis" Proceedings of American Control Conference, Washington DC, 2013, to appear.

Darabi Sahneh F., Scoglio C., "Optimal Information Dissemination in Epidemic Networks (pdf)," Proceedings of IEEE Conference on Decision and Control, Maui, Hawaii, Dec. 2012.

Darabi Sahneh F., Scoglio C., "Epidemic Spread in Human Networks," Proceedings of IEEE Conference on Decision and Control,Orlando, Dec. 2011.

## **Past Projects**

**Modeling and analysis of vector-borne diseases on complex networks**

**Ling Xue**

I'm working on modeling vector-borne diseases, with primary applications to Rift Valley fever. Metapopulation models are developed to capture different features of disease transmission in different environments. Network approach is used to study the role of movement and spatial heterogeneity in disease propagation. Geographic information system is used to facilitate visualization for disease propagation in space. Numerical tools are used to obtain quantitative results and analytic tools are used to understand model behaviors and threshold phenomenon. The network level reproduction number for diseases vertically and horizontally transmitted among multiple species on heterogeneous networks was derived to predict whether a disease may invade the whole system in a deterministic setting. Extinction threshold is derived in a stochastic setting to understand characteristics on disease persistence. Relationships between the reproduction and extinction threshold are derived analytically and numerically. The findings may help to guide and design effective mitigation strategies for public health administrators, and ultimately increase the surveillance of vector-bone diseases

* Publications*
Google Scholar

**Robustness Analysis of Complex Networks with Applications to Power Grids**

**Sakshi Pahwa**

My current project involves proposing two mitigation strategies for cascading failures in power grid networks. These strategies are based on the topological and electrical properties of the power grid networks.

The first strategy uses the electrical centrality and node significance measures to decide the location of distributed generation in the transmission system. Using distributed generation allows load satisfaction locally, and also increases reliability of the system in case of failures. Electrical centrality considers the electrical structure of the power grid to indicate the electrically central nodes whereas the node significance selects important nodes based on flow of power in to and out of the nodes. The use of these measures to decide the location of DGs significantly improves the robustness of the power grid, in terms of load and node loss, when one or more links go out of operation. The second strategy utilizes the spectral properties of the power grid for the addition of a long link in the existing grid. The addition of a long link reduces the characteristic path length of the network which directly affects the network robustness. The eigenvalues corresponding to the second, third, and fourth smallest eigenvectors are used to determine the location of the long link such that the characteristic path length is the smallest for the network.

These two strategies have been tested on the 14, 30, 57, 118, and 300 bus IEEE test networks available at http://www.ee.washington.edu/research/pstca/

* Publications*
Google Scholar

**Estimation of cattle movements**

**Phillip Schumm**

To study outbreaks across large populations and geographical scales through a simulation-based approach three essential components are necessary: a realistic epidemic model, data characterizing the vulnerable populations, and data characterizing the movements among the geographical regions. When considering cattle, the first two components can arguably be said to exist, but scientists face a significant gap in the availability of large-scale cattle movement data, particularly in the United States. This project aims to estimate cattle movement parameters for the modeling of such movement through publicly available data provided by USDA NASS and industrial insights of various farmers, ranchers, and scientists. We formulate a data-driven movement model and optimization problem to estimate a set of parameters that serve to characterize the movement of cattle from a county sub-population (delineated by farm type and size) to other such sub-populations within the same county and in surrounding counties.

* Publications*
Google Scholar

**Complex Networks**

Complex networks can represent a large variety of phenomena, from the topology of an overlay network built over the Internet by a Peer-to-Peer application, to the contact networks that characterize the spreading of epidemics due to bioterrorism agents or naturally occurring infectious diseases. This project concerns the study of multiple statistical metrics and performance indices which characterize complex networks.

People: Caterina Scoglio, Mina Youssef, Phillip Schumm, Sakshi Pahwa.

- Robust Topologies (Mina Youssef)

- Clustering Algorithms (Phillip Schumm)

- Cascading Effects (Sakshi Pahwa)

Cascading failures can be seen in a variety of complex networks including the Internet, the Electric Power Grid, Transportation networks, Social, and Economic networks. We modeled the Power Grid as a complex network to study cascading effects. Cascading effects usually occur in power grids when a critical failure at one place spreads to a wider area, such as 2003 Northeast blackout.

We developed a simulator to study the cascading effects on IEEE test networks representing the different parts of the US power grid. A network generator was developed to generate power grid networks with characteristics similar to the original test cases but with different topologies. Topological analysis of the power grid was stressed upon because topology plays an important role in determining the robustness of the network. Two novel mitigation strategies were suggested to prevent cascading failures - Targeted load reduction and Islanding using distributed sources.

Some of the future work includes a thorough fault and power flow analysis with islanding and distributed sources, detailed analysis on some of the network metrics which may play a role in determining the robustness of the power grid networks and including geographical and other practical constraints to the generated networks to make them more realistic. In addition, work has begun on the analysis of the distribution grid, focusing on the topology, variation of loads and size and placement of distributed renewable generation to enable islanding realistically in the distribution network.*.*

**Publications**

- Piet Van Mieghem, Xin Ge, Phillip Schumm, Stojan Trajanovski, and Huijuan Wang,
“**Spectral graph analysis of modularity and assortativity**,” Physical Review E, vol. 82, no. 5, p. 056113, Nov. 2010.

- Sakshi Pahwa, Amelia Hodges, Caterina Scoglio, and Sean Wood "**Topological Analysis of the Power Grid and Mitigation Strategies Against Cascading Failures**" Proceedings of the 4th Annual International IEEE Systems Conference, 2010, San Diego, USA. PDF Extended Abstract

- Ali Sydney, Caterina Scoglio, Mina Youssef, and Phillip Schumm "**Characterizing the Robustness of Complex Networks**," International Journal of Internet Technology and Secured Transactions, vol. 2, no. 3, pp. 291 - 320, 2010.

- Supriya Nirkhiwale, Caterina Scoglio, "** Optimal mobility pattern in epidemic networks**" Proceedings of IEEE Globecom 2009 Wireless Networking Symposium (GC'09-WNS)

- Caterina Scoglio, Robert Kooij, Phillip Schumm, Ali Sydney, and Mina Youssef, "**Metrics for robustness in complex networks**" Presentation at Delft TU, NAS Group, January 2009, Delft, The Netherlands. PDF preprint

- Robert Kooij, Phillip Schumm, Caterina Scoglio, and Mina Youssef, “**A new metric for robustness with respect to virus spread**” Proceedings of IFIP-TC Networking 2009 (33% acceptance rate), 2009.

-Caterina Scoglio, Robert Kooij, Phillip Schumm, Ali Sydney, and Mina Youssef "**Metrics for Robustness in Complex Networks**" Poster presented at "Complex Systems Conference" National Academies Keck Futures Initiative, November 12-15, 2008, Arnold and Mabel Beckman Center, Irvine, CA. PDF preprint

-Ali Sydney, Caterina Scoglio, Phillip Schumm, and Robert Kooij "**ELASTICITY: Topological Characterization of Robustness in Complex Networks**" Proceedings of IEEE/ACM Bionetics 2008.

- Caterina Scoglio, Todd Easton, Phillip Schumm, and Don Gruenbacher "**Controlling Epidemic Outbreaks through Modeling, Analysis, and Optimization of Complex Networks**" Presentation at THE NABC FORUM August 2007. PDF preprint

- Phillip Schumm, Caterina Scoglio, Todd Easton, and Don Gruenbacher "**Epidemic Spreading on Weighted Contact Networks**" Proceedings of IEEE/ACM Bionetics 2007, Budapest, Hungary, Dec. 2007. PDF preprint

- Caterina Scoglio, Todd Easton, Ronette Gehring, and Phillip Schumm "**Validated Mathematical Models for Epidemics: Utopia or Reality**" Presentation at DMP Seminar Series Fall 2007, November 2007. PDF preprint

**GpENI: Great Plains Environment for Network Innovation**

The Great Plains Environment for Network Innovation (GpENI) is a regional network between The University of Kansas (KU), Kansas State University (K-State), University of Nebraska – Lincoln (UNL), and University of Missouri – Kansas City within the Great Plains Network, supported with optical switches from Ciena interconnected by Qwest fiber infrastructure, in collaboration with the Kansas Research and Education Network (KanREN) and Missouri Research and Education Network. GpENI is funded in part by the National Science Foundation GENI (Global Environment for Network Innovation) Program as part of Cluster B in Spiral 1.

People: Caterina Scoglio, Don Gruenbacher, Ali Sydney, Yunzhao Li.

For more info GpENI wiki

**Overlay, Optical, and Virtual Networks**

An overlay network is an application-layer logical network created on top of the physical network. It is formed by all or a subset of the underlying physical nodes. The connections between each pair of overlay nodes are provided by overlay links which consist of many underlying physical links. Overlay networks can be used to improve performance and provide quality of service on the IP network, by routing data on the overlay links based on performance measurements.

People: Caterina Scoglio, Don Gruenbacher, Yunzhao Li, Mina Youssef

- M. Youssef, B.Y. Choi, C. Scoglio, E. K. Park "**Dynamic Hybrid Topology Design for Integrated Traffic Support in WDM Mesh Networks**" International Journal of Computer Networks, Accepted for publication, 2010

- Yunzhao Li, Don Gruenbacher "**Analysis of P2P File Sharing Networks Credit System for Fairness Management**" IEEE/IFIP NOMS 2010 Mini-conference. OSAKA, JAPAN, April, 2010

- M. Youssef, C. Scoglio "**On Graph-based Characteristics of Optimal Overlay Topologies.**" Computer Network Journal, Elsevier, vol. 53, Issue 7, pp. 913-925, May 2009.

- M. Youssef, B.Y. Choi, C. Scoglio, E. K. Park "**Dynamic Hybrid Topology Design for Multicastin Constrained WDM Networks.**" Proceedings of ICCCN 2008 (26% acceptance rate), St. Thomas, USA, 2008.

- D. Pompili, C. Scoglio, and L. Lopez. "**Multicast Algorithms in Service Overlay Networks.**" Computer Communications Journal vol. 31, pp. 489-505, August 2008.

- B. McBride and C. Scoglio. "**Constructing Traffic-Aware Overlay Topologies: A Machine Learning Approach**." Proceedings of Workshop on Peer-to-Peer Systems (IPTPS 2008), Tampa Bay, USA, 2008. PDF preprint

- D. Medhi, B.Y. Choi, C. Scoglio, S. Song, S Dispensa "**Agent-Based VPN Architecture: Framework and Optimal User Connectivity (Static Case)**" in Proceedings of IEEE ADCOM 2007, Guwahati, India, 2007.

- B. McBride and C. Scoglio. "**Characterizing Traffic Demand Aware Overlay Routing Network Topologies**." Proceedings of IEEE Workshop on High Performance Switching and Routing 2007, New York, USA, 2007. PDF preprint

- M. Youssef, C. Scoglio, and T. Easton. "**Optimal Topology Design for Overlay Networks.**" Proceedings of IFIP Networking 2007 (22% acceptance rate), Atlanta, USA, 2007. PDF preprint

- B. McBride, C. Scoglio, and S. Das. "**Distributed Biobjective Ant Colony Algorithm for Low Cost Overlay Network Routing.**" Proceedings of the 2006 International Conference on Artificial Intelligence. Las Vegas, NV, USA. 2006. PDF preprint

**Traffic Modeling and Forecasting**

In this project we optimally design dynamic reservation schemes which allocate the bandwidth on-line in real-time to flows or aggregation of flows efficiently on the basis of local measurements. It will be possible to use these schemes in currently deployed networks such as MPLS and overlay networks, which are virtual networks, built using the current Internet infrastructure.

People: Caterina Scoglio, Bala Natarajan, Nikkie Anand, Lutfa Akter.

**Publications**

- Caterina Scoglio, Carlo Bruni, Giorgio Koch, Sweta Sutrave "**Estimation of Traffic Flows from Aggregate Measurements**" Mathematical and Computer Modelling, Accepted for publication, 2010.

- Nikkie Anand, Caterina Scoglio, and Bala Natarajan "**Traffic Modeling and Forecasting using Non-Linear Time Series Model - GARCH**" Workshop on Advances in Wireless Networking, "WOW-NET 2007" in conjunction with IFIP Networking 2007, Atlanta, USA, May 2007

- Nikkie Anand, Caterina Scoglio, and Bala Natarajan "**GARCH - Non-Linear Time Series Model for Traffic Modeling and Prediction**" Proceedings of IEEE/IFIP NOMS 08 (short paper), Salvador da Bahia, Brazil, April 2008

- Lutfa Akter, Bala Natarajan, and Caterina Scoglio "**Modeling and Forecasting Secondary User Activity in Cognitive Radio Networks**" Proceedings of ICCCN 2008 (26% acceptance rate), St. Thomas, USA, 2008.

**Interconnection Networks**

For this project, Sandia National Labs and Kansas State University have teamed up and have developed a scaled version of the Red Storm (Thor's Hammer) Super Computer. This has given us the ability to work within the realm of Interconnection Networks by providing a testbed for evaluating different routing theories. Along with routing, this opens up a plethora of research areas for our networking group as well.

People: Don Gruenbacher, Chris Lydick

**Publications**

- Chris Lydick. **Introducing Enhanced Fully-Adaptive Routing Decisions Within Torus-Mesh and Hypercube Interconnect Networks**. April 2008. MS Thesis. PDF (full), PDF (no appendix)

- Chris Lydick. **Evaluating Network Performance Tools for Comparing Transport Protocols**. July 2007, Sandia National Laboratories. SAND2007-4526. PDF

- Chris Lydick. **An Evaluation of Adaptive Routing Algorithms on Tori-Mesh Networks by Nodal Failures**. April 2007. Draft. PDF. (Previous Drafts: PDF, PDF)