Distributed construction of resource-efficient overlay tree by approximating MST

Master'sMASTER OF SCIENC

Distributed Monitoring of Network Properties: The Power of Hybrid Networks

We initiate the study of network monitoring algorithms in a class of hybrid networks in which the nodes are connected by an external network and an internal network (as a short form for externally and internally controlled network). While the external network lies outside of the control of the nodes (or in our case, the monitoring protocol running in them) and might be exposed to continuous changes, the internal network is fully under the control of the nodes. As an example, consider a group of users with mobile devices having access to the cell phone infrastructure. While the network formed by the WiFi connections of the devices is an external network (as its structure is not necessarily under the control of the monitoring protocol), the connections between the devices via the cell phone infrastructure represent an internal network (as it can be controlled by the monitoring protocol). Our goal is to continuously monitor properties of the external network with the help of the internal network. We present scalable distributed algorithms that efficiently monitor the number of edges, the average node degree, the clustering coefficient, the bipartiteness, and the weight of a minimum spanning tree. Their performance bounds demonstrate that monitoring the external network state with the help of an internal network can be done much more efficiently than just using the external network, as is usually done in the literature

Localized Minimum Spanning Tree Based Multicast Routing with Energy-Efficient Guaranteed Delivery in Ad Hoc and Sensor Networks

We present a minimum spanning tree based energy aware multicast protocol (MSTEAM), which is a localized geographic multicast routing scheme designed for ad hoc and sensor networks. It uses locally-built minimum spanning trees (MST) as an efficient approximation of the optimal multicasting backbone. Using a MST is highly relevant in the context of dynamic wireless networks since its computation has a low time complexity (O(n log n)). Moreover, our protocol is fully localized and requires nodes to gather information only on 1-hop neighbors, which is common assumption in existing work. In MSTEAM, a message split occurs when the MST over the current node and the set of destinations has multiple edges originated at the current node. Destinations spanned by each of these edges are grouped together, and for each of these subsets the best neighbor is selected as the next hop. This selection is based on a cost over progress metric, where the progress is approximated by subtracting the weight of the MST over a given neighbor and the subset of destinations to the weight of the MST over the current node and the subset of destinations. Since such greedy localized scheme may lead the message to a void area (i.e., there is no neighbor providing positive progress toward the destinations), we also propose a completely new multicast generalization of the well-know face recovery mechanism. We provide a theoretical analysis proving that MSTEAM is loop-free and always achieves delivery of the multicast message, as long as a path exists between the source node and the destinations. Our experimental results demonstrate that MSTEAM is highly energy-efficient, outperforms the best existing localized multicast scheme and is almost as efficient as a centralized scheme in high densities

Underlay aware approach to support quality of service in publish-subscribe systems

Providing delay-reduced routing is important in publish-subscribe systems where timely delivery of event notifications is a critical factor affecting system operation or user experience. However, common research focused primarily on alleviating false-positives. More recent efforts aim towards quality related issues through adapting the overlay according to subscriber requirements but leaving underlying network characteristics aside. It is commonly accepted that efficient routing can only be achieved when underlying network characteristics are respected. Even so, incorporating underlay-aware strategies to build low-stretch overlays is not considered in many distributed environments. This work focuses on solving the problem of establishing an efficient underlay-aware routing mechanism in a content-based publish-subscribe system. In particular, we strive to reduce end-to-end delay among communication partners. Thereby, our contributions are twofold: We will develop a topology inference scheme for unstructured peer-to-peer networks and introduce a routing mechanism reducing overall end-to-end delay among peers. Experimental evaluations will be given for different Internet-like router topologies showing that the approach is capable of modeling an underlay network in an efficient and accurate manner. Furthermore, we will show the positive impact on the stretch of the overlay to outline the concept as a source for efficient event notification delivery in a publish-subscribe environment

Design of Overlay Networks for Internet Multicast - Doctoral Dissertation, August 2002

Multicast is an efficient transmission scheme for supporting group communication in networks. Contrasted with unicast, where multiple point-to-point connections must be used to support communications among a group of users, multicast is more efficient because each data packet is replicated in the network – at the branching points leading to distinguished destinations, thus reducing the transmission load on the data sources and traffic load on the network links. To implement multicast, networks need to incorporate new routing and forwarding mechanisms in addition to the existing are not adequately supported in the current networks. The IP multicast are not adequately supported in the current networks. The IP multicast solution has serious scaling and deployment limitations, and cannot be easily extended to provide more enhanced data services. Furthermore, and perhaps most importantly, IP multicast has ignored the economic nature of the problem, lacking incentives for service providers to deploy the service in wide area networks. Overlay multicast holds promise for the realization of large scale Internet multicast services. An overlay network is a virtual topology constructed on top of the Internet infrastructure. The concept of overlay networks enables multicast to be deployed as a service network rather than a network primitive mechanism, allowing deployment over heterogeneous networks without the need of universal network support. This dissertation addresses the network design aspects of overlay networks to provide scalable multicast services in the Internet. The resources and the network cost in the context of overlay networks are different from that in conventional networks, presenting new challenges and new problems to solve. Our design goal are the maximization of network utility and improved service quality. As the overall network design problem is extremely complex, we divide the problem into three components: the efficient management of session traffic (multicast routing), the provisioning of overlay network resources (bandwidth dimensioning) and overlay topology optimization (service placement). The combined solution provides a comprehensive procedure for planning and managing an overlay multicast network. We also consider a complementary form of overlay multicast called application-level multicast (ALMI). ALMI allows end systems to directly create an overlay multicast session among themselves. This gives applications the flexibility to communicate without relying on service provides. The tradeoff is that users do not have direct control on the topology and data paths taken by the session flows and will typically get lower quality of service due to the best effort nature of the Internet environment. ALMI is therefore suitable for sessions of small size or sessions where all members are well connected to the network. Furthermore, the ALMI framework allows us to experiment with application specific components such as data reliability, in order to identify a useful set of communication semantic for enhanced data services

The Internet of the Future: Quality of Service and Energy Efficiency

Una delle sfide più importanti del ventunesimo secolo nel campo delle reti di telecomunicazioni è la minimizzazione del consumo di energia fornendo congiuntamente una Qualità del Servizio (QoS). Pertanto, di recente la comunità di ricerca ha iniziato a studiare una serie di iniziative miranti a migliorare la QoS e l’efficienza energetica nell’Internet del futuro. In questo scenario, le Service Overlay Network (SON) sono emerse come un modo proficuo per affrontare questi problemi senza modificare l’infrastruttura sottostante. Invece, il Network Power Management (NPM) cerca i metodi che sono in grado di ottenere risparmi energetici sfruttando opportunamentele caratteristiche energetiche dei dispositivi di rete. In questa tesi, viene analizzato il problema della progettazione topologica di una SON dal punto di vista delle prestazioni. Poichè la soluzione analitica del problema è computazionalmente troppo complessa, si confrontano le prestazioni di un insieme limitato di topologie note. Sulla base di euristiche, tre nuove topologie overlay vengono proposte. Attraverso numerose simulazioni, le prestazioni delle topologie overlay candidate vengono valutate in diversi scenari di rete, tenendo conto del carico e del traffico accettato tra i nodi overlay. Inoltre, questa tesi si concentra sul NPM descrivendo quattro problemi di progettazione di rete per ridurre il consumo energetico delle reti attuali e future. I problemi sono risolti per mezzo di risolutori MILP e MINLP, che ottengono delle soluzioni ottimali o approssimate. Dal momento che in scenari di reti di grandi dimensioni questi approcci sono computazionalmente troppo complessi, sono proposte varie euristiche per i diversi metodi di NPM. L’efficacia degli approcci proposti e dell’euristiche viene esplorata in diversi scenari di rete reali, valutando l’impatto di diversi parametri di rete. I risultati mostrano che le topologie SON sono un’ottima scelta perchè mantengono le stesse prestazioni riducendo l’overhead associato. Inoltre, questa tesi mette in luce l’importanza di una buona caratterizzazione del comportamento energetico dei dispositivi di rete. Notevoli risparmi energetici possono essere raggiunti sfruttando le caratteristiche di potenza dei dispositivi. Le euristiche proposte sono in grado di ridurre il tempo di calcolo e di ottenere risparmi energetici comparabili