Salma Ktari

Building an efficient overlay for publish/subscribe in wireless sensor networks

In this paper we examine how to efficiently build a brokers overlay to implement publish/subscribe in a wireless sensor network, trying to reduce sensor nodes energy consumption, memory required for buffering packets and delivery time. We evaluate, on the connectivity graph that represents the network, the performance of various criteria that can be used to select brokers among the set of nodes. We compare a dominating set approach with the selection of the best ranked brokers based on centrality measures. We finally give hints on how to implement a distributed algorithm to approximate the most efficient overlays.

Power-law chord architecture in P2P overlays

In this paper, we propose to extend the topology of Chord to a bidirectional graph to provide a super-peer based lookup algorithm and an efficient resource localization service at a very little additional cost.

A model to evaluate brokers overlays for publish/subscribe in wireless sensor networks

In this article, we propose a model to compare strategies to deploy a multiple brokers overlay to support a publish/subscribe middleware in wireless sensor networks. We provide expressions for the expected memory size required for buffering packets and the energy consumption at each node and evaluate how many brokers are necessary in a scenario and to compare brokers placement strategies. We demonstrate this model by simulation, comparing the use of various centrality measures to rank broker candidates in random graphs.

Symmetric routing in DHT overlays

In this paper, we propose to extend the DHT topology to a bidirectional graph to provide a super-peer based lookup algorithm and a scalable search support. We consider routing algorithms for a bidirectional variant of the DHT network and show how the resulting structure extends the search region and provides an efficient resource lookup service at a very little additional cost.

Empowering Chord DHT overlays

In peer to peer networks, the overlay topology connecting peers is an important component in addition to peer and data organization and search. In fact, topological characteristics have an important impact on the efficiency of search on such networks. In this paper, we address this issue for Chord based P2P systems. Based on the Barabasi Albert (BA) model, we propose to extend the topology of Chord to a scale free graph DHT, named PL-Chord, to provide a non hierarchical super-peer based lookup algorithm with an efficient search support. Through several simulation experiments, we found that PL-DHT could construct an overlay network that extends the search region and provides higher reachability at a very little additional cost.

A Construction Scheme for Scale Free DHT-Based Networks

In this paper, we propose PowerDHT, a novel scheme to extend the classic DHT-based overlay to a network with scale free-like properties. PowerDHT has a distributed rewiring method to improve the structure of the overlay network to a power-law-like graph. Our scheme is characterized through minimal, typically local-only, changes. Through simulations, we show that our proposal constructs an overlay network with an extended peers neighborhood knowledge and a reduced network diameter at no additional cost and that it supports a more effective flooding e.g. for generic search.

A Peer-to-Peer Social Network Overlay for Efficient Information Retrieval and Diffusion

In this paper we explore new ways in P2P based Online Social Network (OSN) design and present a novel methodology for efficient information retrieval and diffusion in OSN. We propose a new P2P topology model that matches real OSN graph. The new topology decreases the graph diameter and thus the route length by rendering the graph power law. Our proposal can be adapted to existing P2P based OSN systems and thus can fit diverse OSN application requirements. We present the architecture of our adaptable overlay network model as well as the proposed search techniques employed to provide efficient data search and information diffusion. Through simulations, we show the effectiveness of our approach in term of search route length and signaling cost.

Exploiting Power-Law Node Degree Distribution in Chord Overlays

In this paper, we propose to extend the topology of Chord to a bidirectional graph to provide a super-peer based lookup algorithm and a scalable broadcast search support. We consider routing algorithms for a bidirectional variant of Chord network and show how the resulting structure extends the search region and provides an efficient resource lookup service at a very little additional cost.

Structured flooding search in Chord overlays

In this paper, we present an algorithm for an effective flooding procedure with reduced cost in a DHT based P2P network. We describe techniques of flooding and replication that exploit structural constraints to achieve low overhead and higher reliability. These techniques can help to support complex queries in mobile distributed environments with better performance.

Publish/subscribe for wireless sensor networks

This extended abstract overviews some of the advantages and problems to overcome when implementing a publish/subscribe system over a wireless sensor network. Publish/subscribe usually relies on a set of intermediate nodes, brokers that gather and dispatch all the packets emissions. The presence of these brokers lightens the duty of most regular nodes, as they are the only ones who really need to know nodes identities and to maintain long-range routes. However, as computing power, memory, energy and channel bandwidth are scarce resources in WSN, defining an efficient brokering architecture is not trivial. After presenting publish/subscribe in a wireless sensor network context, we examine various performance criteria and discuss on the brokering overlay. If a multi-brokers architecture seems necessary to distribute the load across the network, questions such as the correct number of brokers and their location are difficult when taking into account multiple criteria and that brokers need to remain synchronized. The dynamics of the system also requires attention, as brokers may appear or disappear according to the network traffic patterns or to battery levels.