Quality of service aware ant colony optimization routing algorithm

The demand for Internet connectivity has grown exponentially in the past few years. Moreover, the advent of new services such as Voice over IP (VoIP), Video on Demand (VOD) and Videoconferencing applications have caused a sever increase in traffic, which makes it extremely hard to ensure an acceptable level of quality. This is mainly attributed to current routing strategies, such as Link State (LS) and Distance Vector (DV), which are not optimal in terms of Quality of Service (QoS). This paper presents a QoS-Aware routing strategy based on the Ant Colony Optimization (ACO) concept, where a set of artificial ants are used to determine the optimal path. The proposed method was compared to other state of the art ACO procedures and traditional routing schemes like LS and DV. Simulation results clearly demonstrate that the proposed scheme outperforms all the methods considered in this paper where throughput gains of 8% and a reduction in delay of 38% for time critical applications were achieved.peer-reviewe

An ant-inspired, deniable routing approach in ad hoc question & answer networks

The ubiquity of the Internet facilitates electronic question and answering (Q&A) between real people with ease via community portals and social networking websites. It is a useful service which allows users to appeal to a broad range of answerers. In most cases however, Q&A services produce answers by presenting questions to the general public or associated digital community with little regard for the amount of time users spend examining and answering them. Ultimately, a question may receive large amounts of attention but still not be answered adequately. Several existing pieces of research investigate the reasons why questions do not receive answers on Q&A services and suggest that it may be associated with users being afraid of expressing themselves. Q&A works well for solving information needs, however, it rarely takes into account the privacy requirements of the users who form the service. This thesis was motivated by the need for a more targeted approach towards Q&A by distributing the service across ad hoc networks. The main contribution of this thesis is a novel routing technique and networking environment (distributed Q&A) which balances answer quality and user attention while protecting privacy through plausible deniability. Routing approaches are evaluated experimentally by statistics gained from peer-to-peer network simulations, composed of Q&A users modelled via features extracted from the analysis of a large Yahoo! Answers dataset. Suggestions for future directions to this work are presented from the knowledge gained from our results and conclusion

Algoritmos inspirados en Swarm intelligence para el enrutamieto en redes de telecomunicaciones.

En las últimas décadas hemos visto un rápido desarrollo de las redes de telecomunicación llegando a todos los rincones de la sociedad, bien a través de cable o bien de forma inalámbrica. Dichas redes, que cada vez son más grandes, dinámicas y complejas, integrando un mayor número de servicios y protocolos, requieren de un componente central que es el enrutamiento. El enrutamiento determina las estrategias a utilizar por los nodos de una red para encontrar las rutas óptimas entre un origen y un destino en el envío de información. Resulta difícil conseguir una estrategia que se adapte a este tipo de entornos altamente dinámicos, complejos y con un alto grado de heterogeneidad. Los algoritmos clásicos propuestos hasta la fecha suelen ser algoritmos centralizados que tratan de gestionar una arquitectura claramente distribuida, que en escenarios estacionarios pueden mantener un buen rendimiento, pero que no funcionan bien en escenarios donde se dan continuos cambios en la topología de red o en los patrones de tráfico. Es necesario proponer nuevos algoritmos que permitan el enrutamiento de forma distribuida, más adaptables a los cambios, robustos y escalables. Aquí vamos a tratar de hacer una revisión de los algoritmos propuestos inspirados en la naturaleza, particularmente en los comportamientos colectivos de sociedades de insectos. Veremos cómo de una forma descentralizada y auto-organizada, mediante agentes simples e interacciones locales, podemos alcanzar un comportamiento global "inteligente" que cumpla dichas cualidades. Por último proponemos Abira, un algoritmo ACO basado en AntNet-FA que trata de mejorar el rendimiento y la convergencia introduciendo mecanismos de exploración, de feedback negativo como la penalización y de comunicación de de las mejores rutas. Tras realizar una simulación y comparar los resultados con el algoritmo original, vemos que Abira muestra un mejor rendimiento

Self-organisation in ant-based peer-to-peer systems

Peer-to-peer systems are a highly decentralised form of distributed computing, which has ad¬ vantages of robustness and redundancy over more centralised systems. When the peer-to-peer system has a stable and static population of nodes, variations and bursts in traffic levels cause momentary levels of congestion in the system, which have to be dealt with by routing policies implemented within the peer-to-peer system in order to maintain efficient and effective routes.Peer-to-peer systems, however, are dynamic in nature, as they exhibit churn, i.e. nodes enter and leave the system during their use. This dynamic nature makes it difficult to identify consistent routing policies that ensure a reasonable proportion of traffic in the system is routed successfully to its destination. Studies have shown that chum in peer-to-peer systems is difficult to model and characterise, and further, is difficult to manage.The task of creating and maintaining efficient routes and network topologies in dynamic environments, such as those described above, is one of dynamic optimisation. Complex adap¬ tive systems such as ant colony optimisation and genetic algorithms have been shown to display adaptive properties in dynamic environments. Although complex adaptive systems have been applied to a small number of dynamic optimisation problems, their application to dynamic opti¬ misation problems is new in general and also application to routing in dynamic environments is new. Further, the problem characteristics and conditions under which these algorithms perform well, and the reasons for doing so, are not yet fully understood. The assessment of how good the complex adaptive systems are at creating solutions to the dynamic routing optimisation problem detailed above is dependent on the metrics used to make the measurements.A contribution of this thesis is the development of a theoretical framework within which we can analyse the behaviours and responses of any peer-to-peer system. We do this by considering a peer-to-peer system to be a graph generating algorithm, which has input parameters and has outputs which can be measured using topological metrics and statistics that characterise the traffic through the network. Specifically, we consider the behaviour of an ant-based peer-to-peer system and we have designed and implemented an ant-based peer-to-peer simulator to enable this.Recently methods for characterising graphs by their scaling properties have been developed and a small number of distinct categories of graphs have been identified (such as random graphs, lattices, small world graphs, and scale-free graphs). These graph characterisation methods have also enabled the creation of new metrics to enable measurements of properties of the graphs belonging to different categories.We use these new graph characterisation techniques mentioned above and the associated metrics to implement a systematic approach to the analysis of the behaviour of our ant peer-to-peer system. We present the results of a number of simulation runs of our system initiated with a range of values of key parameters. The resulting networks are then analysed from both the point of view of traffic statistics, and also topological metrics.Three sets of experiments have been designed and conducted using the simulator created during this project. The first set, equilibrium experiments, consider the behaviour of the system when the number of operational nodes in the system is constant and also the demand placed on the system is constant. The second set of experiments considers the changes that occur when there are bursts in traffic levels or the demand placed on the system. The final set considers the effect of churn in the system, where nodes enter and leave the system during its operation. In crafting the experiments we have been able to identify many of the major control parameters of the ant-based peer-to-peer system.A further contribution of this thesis is the results of the experiments which show that under conditions of network congestion the ant peer-to-peer system becomes very brittle. This is characterised by small average path lengths, a low proportion of ants successfully getting through to their destination node, and also a low average degree of the nodes in the network. This brittleness is made worse when nodes fail and also when the demand applied to the system changes abruptly.A further contribution of this thesis is the creation of a method of ranking the topology of a network with respect to a target topology. This method can be used as the basis for topological control (i.e. the distributed self-assembly of network topologies within a peer-to-peer system that have desired topological properties) and assessing how best to modify a topology in order to move it closer to the desired (or reference) topology. We use this method when measuring the outcome of our experiments to determine how far the resulting graph is from a random graph. In principle this method could be used to measure the distance of the graph of the peer-to-peer network from any reference topology (e.g. a lattice or a tree).A final contribution of this thesis is the definition of a distributed routing policy which uses a measure of confidence that nodes in the system are in an operational state when making calculations regarding onward routing. The method of implementing the routing algorithm within the ant peer-to-peer system has been specified, although this has not been implemented within this thesis. It is conjectured that this algorithm would improve the performance of the ant peer-to-peer system under conditions of churn.The main question this thesis is concerned with is how the behaviour of the ant-based peer-to-peer system can best be measured using a simulation-based approach, and how these measurables can be used to control and optimise the performance of the ant-based peer-to-peer system in conditions of equilibrium, and also non-equilibrium (specifically varying levels of bursts in traffic demand, and also varying rates of nodes entering and leaving the peer-to-peer system)

Improved antnet routing algorithm for packet switching

Antnet is a software agent based routing algorithm that is influenced by the unsophisticated and individual ant’s emergent behaviour. In this paper a modified antnet algorithm for packet switched network has been proposed that offer improvement in the throughput and the average delay by means of detecting and dropping packets routed through the non-optimal routes. By applying boundaries to the reinforcement parameter it also limits the effect of traffic fluctuations. The round trip feedback information, supplied by the software agents, is reinforced by the updated probability entries in the distance vector table. In addition link usage information is also used to prevent stagnation problems. Also discussed is antnet with multiple ant colonies applied to packet switched networks. Simulation results show that the average delay experienced by data packets is reduced for evaporation for all cases when non-uniform traffic model traffic is used. However, there was no performance gain on the uniform traffic models. In addition, multiple ant colonies was applied to the packet switched networks and results were compared with the other approaches. Results showed that the throughput could be increased when compared with other schemes, but with no gain in average packet delay