RMAC : a reliable MAC protocol supporting multicast for wireless ad hoc networks

This paper presents a new reliable MAC protocol called "RMAC" supporting reliable multicast for wireless ad hoc networks. By utilizing the busy tones to realize the multicast reliability, RMAC has three novelties: (1) it uses a variable-length control frame to stipulate an order for the receivers to respond, thus solving the feedback collision problem; (2) it extends the usage of busy tone for preventing data frame collisions into the multicast scenario; and (3) it introduces a new usage of busy tone for acknowledging data frames positively. In addition, RMAC is generalized into a comprehensive MAC protocol that provides both reliable and unreliable services for all the three modes of communications: unicast, multicast, and broadcast, making it capable of supporting various upper-layer protocols. The evaluation shows that RMAC achieves high reliability with very limited overhead. RMAC is also compared with other reliable MAC protocols, showing that RMAC not only provides higher reliability but also involves lower cost

A position-based deployment and routing approach for directional wireless mesh networks

Observing that simplicity implies efficiency and scalability, this paper proposes a position-based deployment and routing strategy, and then gives a concrete approach under this strategy, for the emerging wireless mesh networks with multiple radios and directional antennas. The main idea of this strategy is to deploy the mesh network in certain kind of geometric graph and then design a position-based routing protocol by exploiting the routing properties of this graph. The proposed concrete approach comprises two parts: (1) a topology generation algorithm based on Delaunay triangulations and (2) a routing protocol based on the greedy forwarding algorithm. Both parts have appealing properties for deployment or routing, with formal proofs provided when applicable. Our simulation results strongly support this proposed approach

Evaluation of web vulnerability scanners based on OWASP benchmark

The widespread adoption of web vulnerability scanners and their differences in effectiveness make it necessary to benchmark these scanners. Moreover, the literature lacks the comparison of the results of scanners effectiveness from different benchmarks. In this paper, we first compare the performances of some open source web vulnerability scanners of our careful choice by running them against the OWASP benchmark, which is developed by the Open Web Application Security Project (OWASP), a well-known non-profit web security organization. Furthermore, we compare our results from the OWASP benchmark with the existing results from the Web Application Vulnerability Security Evaluation Project (WAVSEP) benchmark, another popular benchmark used to evaluate scanner effectiveness. We are the first to make a comparison between these two benchmarks in literature. Our evaluation results allow us to make some valuable recommendations for the practice of benchmarking web scanners

New memoryless online routing algorithms for delaunay triangulations

Memoryless online routing (MOR) algorithms are suitable for the applications only using local information to find paths, and Delaunay triangulations (DTs) are the class of geometric graphs widely proposed as network topologies. Motivated by these two facts, this paper reports a variety of new MOR algorithms that work for Delaunay triangulations, thus greatly enriching the family of such algorithms. This paper also evaluates and compares these new algorithms with three existing MOR algorithms. The experimental results shed light on their performance in terms of both Euclidean and link metrics, and also reveal certain properties of Delaunay triangulations. Finally, this paper poses three open problems, with their importance explained

Midpoint routing algorithms for Delaunay triangulations

Memoryless online routing (MOR) algorithms are important for the applications with only local information available to make routing decisions. This paper gives two new MOR algorithms for a class of geometric graphs called Delaunay triangulations (DTs): the Midpoint Routing algorithm and the Compass Midpoint algorithm. More meaningfully, the former is generalized into a set of MOR algorithms that use the Euclidean distance as the reference and work for DTs, and the latter is generalized into a set of MOR algorithms that use the direction as the reference and work for DTs. Many other existing MOR algorithms can also be covered by these two sets. Finally, the two new algorithms are evaluated and compared with other existing MOR algorithms, and the experimental results give new findings on the performances of these algorithms in average and general cases

Estimating contention of IEEE 802.11 broadcasts based on inter-frame idle slots

Recent advances in communication technology has enabled vehicles to communicate with each other autonomously through the use of IEEE 802.11p protocol. Vehicle-to-vehicle communication regularly makes use of the broadcast mode transmissions, which are not often used prior to this application. Broadcast mode transmissions are more prone to frame loss from channel contention than unicasts due to its inability to adapt, and are unable to recover lost frames. This makes them very sensitive to channel congestion. In this paper, we first apply a variant of Bianchi et al.’s Markov model of the Distributed Coordination Function (DCF), to show that the observed inter-frame idle slots can be expressed as a probability distribution conditional on the number of saturated stations. It therefore follows that the probability distribution for the number of saturated stations can be estimated from inter-frame idle slots through Bayes law. Second, we present a novel passive channel congestion estimation technique that observes the inter-frame idle slot counts and uses a naive Bayes classifier to estimate the current channel contention in terms of the number of concurrent saturated stations. This technique is evaluated using computer simulations, and is shown to produce more accurate estimates with faster convergence time than the existing technique of observing collision probability using channel busy status as a proxy

Adaptive path tracing with programmable bloom filters in software-defined networks

One critical challenge of managing modern data center networks lies in that existing network protocols provide limited visibility on the internal routing and forwarding decisions made by the control plane, leading to difficulties on fast diagnosis and identification of root causes for performance bugs and anomalies. In this paper, we develop and evaluate a 'debugging mode' for packet forwarding, where we demonstrate a possible design space by introducing a programmable header field into data packets used for diagnosis purposes. These headers can be manipulated by routers in intermediate hops to perform tracing and diagnosis operations, thereby providing much greater visibility on the control plane and data plane operations. To make this design scalable and feasible, we exploit the software APIs provided by the latest software-defined networking (SDN) technologies, where the network control plane is separated from the underlying data plane, so that we can reprogram the network forwarding functions dynamically. Compared to existing alternative approaches, our approach is adaptive and programmable, allowing dynamic and on-demand receiver-side decoding with extremely low overhead. We emphasize that as this 'debugging mode' can be enabled and disabled by network managers as demanded, it introduces zero overhead to normal traffic if everything is operating as expected. Our evaluation results on a real SDN network testbed demonstrate the effectiveness of the proposed approaches

Application-layer multicasting with Delaunay triangulation overlays

Application-layer multicast supports group applications without the need for a network-layer multicast protocol. Here, applications arrange themselves in a logical overlay network and transfer data within the overlay. In this paper, we present an application-layer multicast solution that uses a Delaunay triangulation as an overlay network topology. An advantage of using a Delaunay triangulation is that it allows each application to locally derive next-hop routing information without requiring a routing protocol in the overlay. A disadvantage of using a Delaunay triangulation is that the mapping of the overlay to the network topology at the network and data link layer may be suboptimal.We present a protocol, called Delaunay triangulation (DT protocol), which constructs Delaunay triangulation overlay networks. We present measurement experiments of the DT protocol for overlay networks with up to 10 000 members, that are running on a local PC cluster with 100 Linux PCs. The results show that the protocol stabilizes quickly, e.g., an overlay network with 10 000 nodes can be built in just over 30 s. The traffic measurements indicate that the average overhead of a node is only a few kilobits per second if the overlay network is in a steady state. Results of throughput experiments of multicast transmissions (using TCP unicast connections between neighbors in the overlay network) show an achievable throughput of approximately 15 Mb/s in an overlay with 100 nodes and 2 Mb/s in an overlay with 1000 nodes

A distributed energy saving approach for Ethernet switches in data centers

With popularity of data centers, energy efficiency of Ethernet switches in them is becoming a critical issue. Most existing energy saving approaches use a centralized methodology that assumes global knowledge of data center networks. Though these approaches can achieve nearly optimal energy saving for static traffic patterns, they are not suitable when the traffic patterns can change rapidly or the data centers have a large size. To overcome these limitations, this paper proposes a novel distributed approach called eAware that dynamically idles a port or a switch to save energy by examining the queue lengths and utilizations at switch ports. Through extensive simulations in ns-2, we compare eAware with an existing energy oblivious approach, showing that eAware can save 30%-50% on the total energy consumption by switches in data centers, and only increases the average end-to-end delay of packets by 3%-20% and the packet loss ratio by 0%-0.9%

Toward more effective centrality-based attacks on network topologies

This paper considers the cyber-attacks that aim to remove nodes or links from network topologies. We particularly focus on one category of such attacks, in which attacks happen by rounds, and in each round, the node with the highest centrality and its adjacent links are removed. Here the centrality can be any centrality measure such as Degree Centrality, Betweenness Centrality, etc. For this attack category, there currently exist two strategies: Initial and Adaptive. In the Initial strategy, node centralities are only calculated initially, while in the Adaptive strategy, node centralities are recalculated after each round of attack. In the literature, it has been shown that the Adaptive strategy is more effective than the Initial strategy for a centrality measure. In this paper, we propose a new strategy called the largest component (LC) strategy which further outperforms the Adaptive strategy in terms of both attack effectiveness and computation complexity. Moreover, we propose the use of current-flow versions of Betweenness Centrality and Closeness Centrality as the centrality measures in the attacks, since they are more granular and supported by the LC strategy. We verify the better performances of the LC strategy by extensive experiments on four kinds of artificial networks and two realworld networks. Our experiments also show that the Currentflow Betweenness Centrality makes attacks the most effective among the five centrality measures studied in this paper