Raphael Chand

A scalable protocol for content-based routing in overlay networks

In content networks, messages are routed on the basis of their content and the interests (subscriptions) of the message consumers. This form of routing offers an interesting alternative to unicast or multicast communication in loosely-coupled distributed systems with large number of consumers, with diverse interests, wide geographical dispersion, and heterogeneous resources (e.g., CPU, bandwidth). In this paper, we propose a novel protocol for content-based routing in overlay networks. This protocol guarantees perfect routing (i.e., a message is received by all, and only those, consumers that have registered a matching subscription) and optimizes the usage of the network bandwidth. Furthermore, our protocol takes advantage of subscription aggregation to dramatically reduce the size of the routing tables, and it fully supports dynamic subscription registrations and cancellations without impacting the routing accuracy. We have implemented this protocol in the application-level routers of an overlay network to build a scalable XML-based data dissemination system. Experimental evaluation shows that the size of the routing tables remains small, even with very large populations of consumers.

Semantic peer-to-peer overlays for publish/subscribe networks

Existing publish/subscribe systems suffer from several drawbacks, such as the reliance on a fixed infrastructure of reliable brokers, or the lack of expressiveness of their subscription language. Most importantly, the challenging task of routing messages based on their content remains a complex and time-consuming operation, and often provides results that are just barely better than a simple broadcast. In this paper, we present a novel approach to publish/subscribe that was designed to specifically address these issues. The producers and consumers are organized in a peer-to-peer network that self-adapts upon peer arrival, departure, or failure. Our publish/subscribe system features an extremely simple and efficient routing process and excellent scalability to large consumer populations, both in terms of routing and peer management overhead.

XNET: a reliable content-based publish/subscribe system

Content-based publish/subscribe systems are usually implemented as a network of brokers that collaboratively route messages from information providers to consumers. A major challenge of such middleware infrastructures is their reliability and their ability to cope with failures in the system. In this paper, we present the architecture of the XNET XML content network and we detail the mechanisms that we implemented to gracefully handle failures and maintain the system state consistent with the consumer population at all times. In particular, we propose several approaches to fault tolerance so that our system can recover from various types of router and link failures. We analyze the efficiency of our techniques in a large scale experimental deployment on the PlanetLab testbed. We show that XNET does not only offer good performance and scalability with large consumer populations under normal operation, but can also quickly recover from system failures.

Scalable Distribution of XML Content with XNet

The XNET XML content network was designed to implement efficient and reliable distribution of structured XML content to very large populations of consumers. For that purpose, our system integrates several technologies: the routing protocol XROUTE makes extensive use of subscription aggregation to limit the size of routing tables while ensuring perfect routing (that is, an event is forwarded to a link only if it leads to an interested consumer). The filtering engine XTRIE uses a sophisticated algorithm to match incoming XML documents against large populations of tree-structured subscriptions, whereas the XSEARCH subscription management algorithm enables the system to efficiently manage large and highly dynamic consumer populations. Finally, our XNET system integrates reliability mechanisms to guarantee that its state is consistent with the consumer population and implements several approaches to fault tolerance to recover from various types of router and link failures. We have analyzed the efficiency of our techniques with various simulations, and to assess the performance of our system in realistic settings and show that it is perfectly suitable for large-scale distributed environments, we have performed a large-scale experimental deployment on the PlanetLab testbed.

Powerful Resource Discovery for Arigatoni Overlay Network

Arigatoni is a structured multi-layer overlay network providing various services with variable guarantees, and promoting an intermittent participation in the overlay since peers can appear, disappear and organize themselves dynamically. Arigatoni provides fully decentralized, asynchronous and scalable resource discovery; it also provides mechanisms for dealing with an overlay with a dynamic topology. This paper introduces a nontrivial improvement of the resource discovery protocol by allowing the registration and request of multiple instances of the same service, service conjunctions, and multiple services. Adding multiple instances is a nontrivial task since the discovery protocol must keep track (when routing requests) of peers that accept to serve and peers that deny the service. Adding service conjunctions allows a single peer to offer different services at the same time. Simulations show that it is efficient and scalable.

Improving resource discovery in the Arigatoni overlay network

Arigatoni is a structured multi-layer overlay network providing various services with variable guarantees, and promoting an intermittent participation to the virtual organization where peers can appear, disappear and organize themselves dynamically. Arigatoni mainly concerns with how resources are declared and discovered in the overlay, allowing global computers to make a secure, PKI-based, use of global aggregated computational power, storage, information resources, etc. Arigatoni provides fully decentralized, asynchronous and scalable resource discovery, and provides mechanisms for dealing with dynamic virtual organizations. This paper introduces a non trivial improvement of the original resource discovery protocol by allowing to register and to ask for multiple instances. Simulations show that it is efficient and scalable.