Tronje Krop

A survey on dependable routing in sensor networks, ad hoc networks, and cellular networks

The class of wireless and mobile networks features a dissimilar set of characteristics and constraints compared to traditional fixed networks. The various dimensions of these characteristics/constraints strongly influence the routing system, which is often regarded as the glue of a network. We introduce the concept of routing dependability describing the trustworthiness of a routing system such that reliance can justifiably be placed on the consistency of behavior and performance of the routing service delivered. We investigate this concept by analyzing the basic characteristics of various networks. Subsequently, we derive the most important attributes and impairments that contribute to routing dependability in sensor networks, ad hoc networks, and infrastructure-based cellular networks. Departing from state-of-the-art network designs, we extend our survey to cover future network architectures as well. We finish by briefly investigating possible directions and means that allow mitigating the deprivation of dependability.

JiST/MobNet: combined simulation, emulation, and real-world testbed for ad hoc networks

Mobile ad hoc networks are a promising technology enabling the spontaneous formation of communication networks without dedicated infrastructure. However, ad hoc networks are not yet ready for large-scale deployment, because several unsolved research challenges persist. Evaluation methods such as analytical modeling, simulation, emulation, and real-world experiments aid in addressing these challenges. Applying a single method alone often leaves doubt as to the accuracy of the obtained results. Thus, there is a strong need for tools that support the task of modeling, evaluation, and analysis. These tools should allow for protocol validation, performance analysis, and proof-of-concept implementation using multiple evaluation methods. In this paper, we present a new approach for conducting simulation, emulation, and real-world experiments in mobile ad hoc networks using a single tool that allows for vertical validation of experiments. We explain the principles behind the architecture of our tool and systematically assess its limitations.

A survey on real world and emulation testbeds for mobile ad hoc networks

Mobile ad hoc networks allow for the spontaneous formation of communication networks without dedicated infrastructure. Ad hoc networks are not yet ready for large-scale deployment, because several unsolved research challenges persist. Evaluation methods such as analytical modeling, simulation, emulation, and real world experiments aid in addressing these challenges. There is a strong need for tools to support the task of modeling and evaluation to allow for protocol validation, performance analysis, or proof-of-concept implementations. The choosing of appropriate tools is a time-consuming process, which is often unnecessarily repeated, due to limited knowledge-transfer. We contribute an extensive survey covering real world and emulation testbeds to simplify the choice of appropriate research tools and methodologies in the domain of mobile ad hoc networks. In particular, we identify the key attributes of the aforementioned classes of testbeds and thoroughly discuss the state-of-the-art in literature to form a comprehensive classification of available testbeds

Modeling mobility and workload for wireless metropolitan area networks

Research on large-scale wireless metropolitan area networks, which offer broadband capacity while supporting user and terminal mobility suffers from the lack of realistic mobility and workload models. There is a strong need for such models to be able to perform sound simulations supporting important yet difficult tasks like network planning and traffic engineering. In this paper, a novel approach towards realistic modeling of user mobility is proposed and studied. We formulate an analytical model, which is a hybrid of an empirical mobility model and a synthetic traffic model. The model clearly separates the influence of mobility and traffic to allow for greater flexibility. The mobility part is based on the combination of statistical zoning information with field data of movement patterns. This allows us to predict the density of users-classified into different groups-for a given area at a given time. We are able to integrate different traffic characteristics on top of our mobility model elegantly. The combination of user density with the predicted-synthetic-traffic of the modeled user groups gives the traffic and fluctuations of traffic throughout the network, thus describing the workload for the envisioned scenario. We present the instantiation of our model for the example of a real city. Analysis and simulations are provided which show that the proposed scheme is quite prospective. Our findings are, that our model is able to cover the macroscopic effects of real-world behavior more precisely than currently available mobility/workload models.

Comparative analysis of quality of service routing in wireless metropolitan area networks

Currently, we see the evolution of large scale community and metropolitan area networks based on inexpensive wireless local area network technology. We present the results of an experimental analysis, which investigates the potential of quality of service routing mechanisms within this challenging environment. Our investigation is based on a model of a radio access network designed to cover a large city center by means of decentralized and distributed routers, which are tightly meshed. The workload is modeled to reflect the estimated usage patterns based on statistical data collection of user mobility and combined with synthetic traffic matrices. We present results for various routing strategies including shortest path routing, delay constrained routing as well as various multipath quality of service routing variants. Moreover, we investigate different traffic distributions. Our findings are, that multipath routing is able to enhance the utility of the network significantly.

GeoSec: quarantine zones for mobile ad hoc networks

With their wireless and infrastructureless nature, mobile ad hoc networks offer new possibilities for communication, but also new possibilities for attacks. An intrusion detection system combined with intrusion response mechanisms is a promising approach which mitigates the effects of attacks, but cannot be taken directly from wired or infrastructure-based environments. In this paper, we propose an intrusion response mechanism for mobile ad hoc networks that excludes detected adversaries from the network based on their geographical position. To this end, we establish geographical quarantine zones, which block communication around misbehaving nodes. Thus, we depart from the assumption that attacks can be uniquely bound to addresses. Without loss of generality, we show how our approach can be used together with the AODV routing protocol to provide an intrusion response to a combination of Blackhole and Sybil attacks. In a series of simulation studies, we compare our approach with a ‘traditional’, address-based intrusion response strategy. Copyright

Enhancing Availability with Self-Organization Extensions in a SOA Platform

The availability and reliability of Service-oriented architectures (SOA) depends on two factors: On the one hand, the availability and reliability of the services that provide a certain business functionality and on the other hand the services that make up the underlying SOA platform. For platforms that are supposed to form the core of mission-critical service-oriented applications, this implicates the need for mechanisms that can regulate the reliability- and availability-levels of the core services in changing conditions. In this paper, we discuss open questions about what kind of monitoring functionalities and service replication mechanisms should be integrated in SOA infrastructures. Therefore, the integration of concepts from peer-to-peer (P2P) computing is proposed: We present a self-organization extension that can improve the availability of the core services of SOA infrastructures, and we provide an experiment-based evaluation, showing some of the benefits that this extension can have in a critical scenario. The concepts are prototypically implemented as extensions of Apache Tuscany, which is a realization of the Service Component Architecture (SCA) standard.

Seasonal changes in the behaviour and circadian rhythms in activity and behaviour of captive koalas Phascolarctos cinereus

Feeding and locomotor activity of one male and three female koalas have been continuously observed for one year at Taronga Zoo, Sydney, Australia. Activity was not restricted to the night, but showed a clear day–night distinction with activity maxima during twilight and following afternoon feeding. Acrophase of activity changed during the year but remained within the first half of the night. The koalas spent between 18 and 20 hours per day resting, and between 2.5 and 4 hours feeding. On average, 7.2±1.90 bouts per day have been observed in the male and 6.5±2.11 bouts in the females. Though there was a clear relation between food introduction and feeding activity, activity pattern and time budget were similar to free-ranging koalas.

A hybrid workload model for wireless metropolitan area networks

Wireless local and metropolitan area networks are en route to complement 2nd and 3rd generation cellular networks to provide for broadband wireless access for mobile users. The characterization and generation of realistic workload is important to allow for accurate network planning and traffic engineering. In this paper, we present the instantiation of a novel workload model, which is a hybrid of an empirical mobility model and a synthetic traffic model. We focus on the effects which are induced by user mobility. The model clearly separates the influence of mobility and traffic to allow for greater flexibility. Thus, we are able to integrate different traffic characteristics on top of our mobility model elegantly. We present results for the example of a real city and compare our model to existing synthetic models. Our findings are, that our model is able to cover the macroscopic effects of real world behavior more precise than currently available workload models.

Modeling static and dynamic behavior of routes in mobile ad hoc networks

Ad hoc networking research needs meaningful models to describe the behavior of multihop routes. We survey existing static models to describe the distribution of link and path distances as well as dynamic models describing the lifetime of links, paths, and routes. Next, we enhance and combine selected models to form a combined model describing both, the static and dynamic aspects of multihop ad hoc routes. In particular, our model allows for prediction of lifetimes for single and multipath routes for a bounded and an unbounded modeling area. As a proof-of-concept, the model is applied to analyze the efficiency of different usage strategies of multipath routes: based on the lifetime predictions of our model we estimate the transport capacity of the routes.