ÐHigh-speed local area networks (LANs) consist of a set of switches interconnected by point-to-point links, and hosts linked to those switches through a network interface card. High-speed LANs may change their topology due to switches being turned on/off, hot expansion, link remapping, and component failures. In these cases, a distributed reconfiguration protocol analyzes the topology, computes the new routing tables, and downloads them to the corresponding switches. Unfortunately, in most cases, user traffic is stopped during the reconfiguration process to avoid deadlock. These strategies are called static reconfiguration techniques. Although network reconfigurations are not frequent, static reconfiguration such as this may take hundreds of milliseconds to execute, thus degrading system availability significantly. Several distributed real-time applications have strict communication requirements. Distributed multimedia applications have similar, although less strict, quality of service (QoS) requirements [3], [4]. Both stopping packet transmission and discarding packets due to the reconfiguration process prevent the system from satisfying the above requirements. Therefore, in order to support hard real-time and distributed multimedia applications over a high-speed LAN, we need to avoid stopping user traffic and discarding packets when the topology changes. In this paper, we propose a new deadlock-free distributed reconfiguration protocol that is able to asynchronously update routing tables without stopping user traffic. This protocol is valid for any topology, including regular as well as irregular topologies. It is also valid for packet switching as well as for cut-through switching techniques and does not rely on the existence of virtual channels to work. Simulation results show that the behavior of our protocol is significantly better than for other protocols based on stopping user traffic.
High-speed local area networks (LANs) consist of a set of switches connected by point-to-point links, and hostslinked to switches through a network interface card. Highspeed LANs may change their topology due to switches and hosts being turned on/off, link remapping, and component failures. In these cases, a distributed reconfiguration algorithm analyzes the topology, computes the new routing tables, and downloads them to the corresponding switches. Unfortunately, in most cases, user traffic is stopped during the reconfiguration process to avoid deadlock. Although network reconfigurations are not frequent, static reconfiguration such as this may take hundreds of milliseconds to execute, thus degrading system availability significantly.Several distributed real-time applications have strict communication requirements [9,11]. Distributed multimedia applications have similar, although less strict, quality of service (QoS) requirements. Both stopping packet transmission and discarding packets due to the reconfiguration process prevent the system from satisfying the above requirements. Therefore, in order to support hard real-time and distributed multimedia applications over a high-speed LAN, we need to avoid stopping user traffic and discarding packets when the topology changes.In this paper, we propose a new deadlock-free distributed reconfiguration algorithm that is able to asynchronously update routing tables without stopping user traffic. This algorithm is valid for any topology, including regular as well as irregular topologies. Simulation results show that the behavior of our algorithm is significantly better than for other algorithms based on a spanning-tree formation.
This paper presents the simulation environment for the EIDOS (EquIpment Destined for Orientation and Safety) architecture applied to wildfire fighting operations. The development of this environment involves a multidisciplinary study, in which we have to handle several different types of information (geographical data, vegetation models, fire models, etc.) and devices (sensors, aerial vehicles, and mobile devices). Therefore, the simulation tool is actually composed of several independent and interconnected modules. Motivation and scopeForest fires represent one of the main causes of environmental degradation in many countries. Moreover, very often the people working directly on their extinction and residing in the area affected by the fire is in serious danger. With the final goal of reducing the risk to which these people are exposed, and increasing the efficacy of wildfire fighting operations, recently we have proposed the EIDOS system [4]. This architecture is based on the use of a WSN (wireless sensor network), which is deployed over the area affected by the fire, and is able to provide the fire-fighters with critical information in real time, contributing to increment their safety.Several recent works propose using WSNs for firefighting. As an example, FireNet [2] focuses on fire rescue in urban areas. In this proposal, each fire-fighter carries a Crossbow Mica2/MicaZ [1] (attached with a sensor board), that is able to sense data and forward packets to the sink node (located in the incident commander vehicle). Another representative proposal may be FireWxNet [7], which presents a complex tiered architecture for wildfire environments. In almost all these proposals, the purpose of the sensor network consists in just acquiring environmental data. Then, this information is gathered in a central server (for example a PC), where it is displayed, stored in a database, processed, used as input for some fire prediction software, or sent to a remote location.However, in the EIDOS system, the information collected by the network is processed by the sensors themselves in a collaborative way, with the aim of obtaining information about the localization of the active fire fronts and their evolution along the time. Finally, the result of this processing can be transmitted either to the people working in fighting operations (equipped with mobile devices), or to a base station.Although we plan to build a real prototype bringing together the subsystems we are designing, the initial phase of the EIDOS development will be carried out over a simulation environment. This platform will allow us to analyze and refine the behavior of our proposals. In this paper, we provide a description of this simulation environment.Next, the architecture and functionality of the EIDOS system are introduced. Then, an outlook of the simulator tool is presented, and the modules composing it are detailed. Finally, some conclusions are given, and future work is proposed. EIDOS system ArchitectureAt a glance, the EIDOS system consists of three types ...
Abstract-The InfiniBand architecture has been proposed as a technology both for communication between processing nodes and I/O devices, and for interprocessor communication. Its specification defines a basic management infrastructure that is responsible for subnet configuration and fault tolerance. Each time a topology change is detected, new forwarding tables have to be computed and uploaded to devices. The time required to compute these tables is a critical issue, due to application traffic is negatively affected by the temporary lack of connectivity. In this paper, we show the way to integrate several routing algorithms, in order to combine their advantages. In particular, we merge a new proposal, characterized by its high computation speed but low efficiency, with a traditional one, slower but more efficient. Our goal is to provide new routes in a short period of time, minimizing the degradation mentioned before, and maintaining, at the same time, high network performance.
The InfiniBand Architecture is a high-performance network technology for the interconnection of processor nodes and I/O devices using a point-to-point switch-based fabric. The InfiniBand specification defines a basic management infrastructure that is responsible for subnet configuration, activation, and fault tolerance. Subnet management entities and functions are described, but the specifications do not impose any particular implementation. This paper presents and analyzes a complete subnet management mechanism for this architecture. This work allows us to anticipate future directions to obtain efficient management protocols.
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