hiromori's library 22 articles

Abstract

Discrete event network simulators have emerged as popular tools for verification and performance evaluation for various wireless networks. Nevertheless, the desire to model such networks at high fidelity implies high computational costs, prohibiting most researchers from simulating wireless networks with thousands of nodes. There have been attempts on performance optimizations for large-scale wireless network simulation, but they have not appropriately modeled accumulation of weak interference, thereby suffering inaccuracies which may be magnified by upper layer protocols. This paper presents analysis of ...

Abstract

In this paper, we address the issue of integrating packet-level simulation with fluid-model-based simulation for IEEE 802.11-operated wireless LANs (WLANs), so as to combine the performance gain of the latter with the accuracy and packet-level detail afforded by the former. In mixed-mode simulation, foreground flows operate in the packet mode, while the other background flows are approximated into a collection of fluid chunks and simulated in the fluid mode. As these two types of flows influence each other at the point ...

Abstract

In this paper, we develop a fast simulation framework for IEEE 802.11-operated wireless LANs (WLANs), in which a large number of packets are abstracted as a single fluid chunk, and their behaviors are approximated with analytic fluid models and figured into the simulation. We first derive the analytical model that characterizes data transmission activities in IEEE 802.11-operated WLANs with/without the RTS/CTS mechanism. All the control overhead incurred in the physical and MAC layers, as well as system parameters specified in IEEE ...

Abstract

A layered model of structured overlays has been proposed and it enabled development of a routing layer independently of higher-level services such as DHT and multicast. The routing layer has to include other part than a routing algorithm, which is essential for routing. It is routing process, which is common to various routing algorithms and can be decoupled from a routing algorithm. We demonstrated the decomposition by implementing an overlay construction toolkit Overlay Weaver. It facilitates implementation of routing algorithms and ...

Abstract

Overlay networks are used today in a variety of distributed systems ranging from file-sharing and storage systems to communication infrastructures. However, designing, building and adapting these overlays to the intended application and the target environment is a difficult and time consuming process.To ease the development and the deployment of such overlay networks we have implemented P2, a system that uses a declarative logic language to express overlay networks in a highly compact and reusable form. P2 can express a Narada-style mesh ...

Abstract

Starting in the late 1950s, researchers have been performing progressively more sensitive searches for radio signals from extraterrestrial civilizations, but each search has been limited by the technologies available at the time. As radio frequency technologies have became more efficient and computers have become faster, the searches have grown larger and more sensitive, The SETI@home project, managed by a group of researchers at the Space Sciences Laboratory of the University of California, Berkeley, is the first attempt to use large-scale distributed ...

Abstract

In December 1999, IBM announced the start of a five-year effort to build a massively parallel computer, to be applied to the study of biomolecular phenomena such as protein folding. The project has two main goals: to advance our understanding of the mechanisms behind protein folding via large-scale simulation, and to explore novel ideas in massively parallel machine architecture and software. This project should enable biomolecular simulations that are orders of magnitude larger than current technology permits. Major areas of investigation ...

Abstract

The Grid Datafarm (Gfarm) architecture is designed forglobal petascale data-intensive computing.It provides aglobal parallel filesystem with online petascale storage,scalable I/O bandwidth, and scalable parallel processing,and it can exploit local I/O in a grid of clusters with tensof thousands of nodes.Gfarm parallel I/O APIs and commands provide a single filesystem image and manipulatefilesystem metadata consistently.Fault tolerance and loadbalancing are automatically managed by file duplication orrecomputation using a command history log.Preliminaryperformance evaluation has shown scalable disk I/O andnetwork bandwidth on 64 nodes of ...

Abstract

Currently, researchers designing and implementing largescale overlay services employ disparate techniques at each stage in the production cycle: design, implementation, experimentation, and evaluation. As a result, complex and tedious tasks are often duplicated leading to ine#ective resource use and di#culty in fairly comparing competing algorithms. In this paper, we present MACEDON, an infrastructure that provides facilities to: i) specify distributed algorithms in a concise domainspecific language; ii) generate code that executes in popular evaluation infrastructures and in live networks; iii) leverage ...

Abstract

We design a lightweight Overlay Network, called Arigatoni, that is suitable to deploy the Global Computing Paradigm over the Internet. Communications over the behavioral units of the model are performed by a simple communication protocol. Basic Global Computers can communicate by first registering to a brokering service and then by mutually asking and offering services, in a way that is reminiscent to Rapoport's "titfor- tat" strategy of cooperation based on reciprocity. In the model, resources are encapsulated in the administrative domain ...

Abstract

Recently, Peer-to-Peer (P2P) technology has become important in designing (desktop) grids for large-scale distributed computing over the Internet. We present a middleware for distributed computing based on Peer-to-Peer systems. When combining public-resource computation ideas with concepts of P2P networks, new challenges occur due to the lack of global knowledge as there is no central administration possible. Our Peer-to-Peer desktop grid (P2P Grid) framework includes an efficient and fault-tolerant communication scheme for job distribution combining epidemic algorithms with chord-style multicasts. We show ...

Abstract

Congestion is expected to become a prominent problem to deal with as the popularity of wireless data networks continues to increase. However, this problem can in principle be mitigated if a fraction of the network users could decide to move to another location in case their perceived QoS degrades. To account for this, we propose an extension of the well-known RWP model called QoS-RWP, in which users are divided into mobile users displaying constrained movement patterns, and QoS-driven users who are ...

Abstract

In this work we study the stability of routing paths in a Mobile Ad-hoc Network (MANET), where links are subject to failure due to nodes' mobility. We focus on the Random Direction mobility model, and consider as metrics of interest the duration and availability of links and paths. ...

Abstract

To properly use a mobility model to evaluate a wireless network policy via computer simulations it is necessary to know the statistics of mobile terminal locations for the model. Unfortunately, these statistics are only known for a limited number of mobility models which limits the analysis of wireless networks that can be done using computer simulations. This paper presents a method for calculating an approximation of the steady-state distribution of mobile terminal locations for a general class of mobility models. The ...

Abstract

Ubiquitous access of the resource is the greatest challenge in the world of distributed mobile computing. This paper discuss the framework of agent based middleware to provide efficient, flexible and Scalable system support for configuration and communication in heterogeneous wireless networks. The proposed middleware satisfies the requirement of ubiquitous access of the resource in multilayer modular manner by hiding the platform heterogeneity. ...

Abstract

The very nature of implementing and evaluating fully distributed algorithms or protocols in application-layer overlay networks involves certain programming tasks that are at best mundane and tedious – and at worst challenging – even at the application level. In this paper, we present iOverlay, a lightweight and high-performance middleware infrastructure that addresses these problems in a novel way by providing clean, well-documented layers of middleware components. The internals of iOverlay are carefully designed and implemented to maximize its performance, without sacrificing ...

Abstract

This paper describes the static and dynamic task allocation tools in PVM environment for distributed memory parallel systems. For the static mapping the objective function is used to evaluate the optimality of the allocation of a task graph onto a processor graph. Together with our optimization method also augmented simulated annealing and heuristic move exchange methods in distributed form are implemented. For dynamic task allocation the semidistributed approach was designed based on the division of processor network topology into independent and ...

Abstract

In a distributed computing system, a number of program modules may need to be allocated to different processors such that the reliability of executing successfully these modules is maximized and the constraints with limited resources are satisfied. The problem of finding an optimal task allocation with maximum system reliability has been shown to be NP-hard; thus, existing approaches to finding exact solutions are limited to the use in problems of small size. This paper presents a hybrid particle swarm optimization (HPSO) ...

Abstract

We present our preliminary work that develops a new approach to hybrid packet/analytic network simulations for improved network simulation fidelity, scale, and simulation efficiency. Much work in the literature addresses this topic, including [10] [11] [8] [12] [13] and others. Current approaches rely upon models, which we refer to in this paper as Deterministic Fluid Models [9] [12], to address the analytic modeling aspects of these hybrid simulations. Instead we draw upon an extensive literature on stochastic models of queues and ...