5180938
A Sensor-cyber Network Testbed for Plume Detection, Identification, and Tracking
Detection, identification, and tracking (DIT) problems that arise in applications such as the protection of people and the environment against radiational, biological, and chemical plumes, can be solved by combining the modalities of sensor and cyber networks. The sensor network provides information about physical space activities, such as the locations and movements of plume sources and targets. The cyber network provides storage and computational resources to analyze and infer, based on realistic dispersion models of plumes with respect to physical phenomena (e.g., terrain and weather effects), where the plume originated, the trajectory of its movement (speed and direction), and the prediction of its future movement. The cyber network also makes decisions about where to task and activate plume sensors regarding their future sensing and communciation activities.
16965968
Performance of Full Text Search in Structured and Unstructured Peer-to-Peer Systems
While structured P2P systems (such as DHTs) are often regarded as an improvement over unstructured P2P systems (such as super-peer networks) in terms of routing efficiency, it is not clear which architecture is better for full text search. This paper provides a quantitative comparison of full text keyword search in structured and unstructured P2P systems. We examine three techniques (and optimizations to those techniques) proposed in the literature: using a DHT along with inverted lists and Bloom filters; using a super-peer network; and using a random walk over an unstructured network. We use real Web documents and user queries to measure the cost for both document publishing and query processing, in terms of bandwidth and response time. Our results show that all three techniques use roughly the same bandwidth to process queries (with the super-peer technique having a slight edge). The structured network provides the best response time (30 percent better than a super-peer network), but has a high cost of document publishing, using six times as much bandwidth as the super-peer system. The random walk technique requires no publishing, but has a very long response time unless multiple random walks operate in parallel.
14988023
Modeling the Effect of Transmit Power and Physical Carrier Sense in Multi-Hop Wireless Networks
In this paper, we extend both Bianchi's and Kumar's models and characterize the channel activities governed by IEEE 802.11 DCF in multi-hop wireless networks from the perspective of an individual sender. In particular, we incorporate the effect of PHY/MAC attributes (such as transmit power and physical carrier sense) that need not be considered in WLANs but become extraordinarily important in multi-hop wireless networks, and derive the throughput attained by each sender. With the use of the analytical model derived, we investigate the impact of transmit power and carrier sense threshold on network capacity, and identify a simple operating condition under which the network may attain throughput that is close to its optimal value.
30026565
A Web-based Real-time Cooperative Editor in Java
2911118
A Theory of Network Localization
In this paper, we provide a theoretical foundation for the problem of network localization in which some nodes know their locations and other nodes determine their locations by measuring the distances to their neighbors. We construct grounded graphs to model network localization and apply graph rigidity theory to test the conditions for unique localizability and to construct uniquely localizable networks. We further study the computational complexity of network localization and investigate a subclass of grounded graphs where localization can be computed efficiently. We conclude with a discussion of localization in sensor networks where the sensors are placed randomly
7877505
Three forbidden subgraphs for line graphs
We construct a set of three graphs with the property that a 3-connected graph with minimum degree at least 7 is a line graph if and only if it does not contain any of the three graphs as an induced subgraph. We also show that the number of excluded subgraphs cannot be reduced no matter what connectivity is specified.
34587947
Guaranteed Mutually Consistent Checkpointing in Distributed Computations
In this paper, we emplore the isomorphism between vector time and causality to characterize consistency of a set of checkpoints in a distributed computing. A necessary and sufficient condition, to determine if a set of checkpoints can form a consistent global checkpoint, is presented and proved using the isomorphic power of vector time and causality. To the best of our knowledge, this is the first attempt to use the isomorphism for this purpose. This condition leads to a simple and straightforward algorithm for a guaranteed mutually consistent global checkpointing. In our approach, a process can take a checkpoint whenever and wherever it wants while other related process may be asked to take an additional checkpoint for ensuring the mutual consistency. We also show how this condition and the resulting algorithm can be used to obtain a maximum and minimum global checkpoints, another important paradigm for distributed applications.
12472387
CLID: A general approach to validate security policies in a dynamic network
Many researchers have considered security policy management, including how to configure policies manually and even how to automatically generate security policies based on security requirements. Both can be error prone, especially when properties of the network topology change, because security requirements are usually not bound to any particular route path. Our DETER lab emulation results show that conflicts could be caused by these factors. Therefore, a systematic way to validate the correctness of the security policies is essential. This paper presents an approach, CLID (conflict and looping identification and detection), to verify whether a set of security policies (e.g. IPSec/VPN tunnels) satisfy the given security requirements, without causing any conflicts. This approach utilizes the definition of a security policy lo include network routing data as well as traffic selector information, thus it works for general network topologies. We also analyze and justify the correctness of the approach. The paper concludes with our simulation results and addresses future work.