N.L.S. da Fonseca

Scheduling in hybrid clouds

Schedulers for cloud computing determine on which processing resource jobs of a workflow should be allocated. In hybrid clouds, jobs can be allocated on either a private cloud or a public cloud on a pay per use basis. The capacity of the communication channels connecting these two types of resources impacts the makespan and the cost of workflow execution. This article introduces the scheduling problem in hybrid clouds presenting the main characteristics to be considered when scheduling workflows, as well as a brief survey of some of the scheduling algorithms used in these systems. To assess the influence of communication channels on job allocation, we compare and evaluate the impact of the available bandwidth on the performance of some of the scheduling algorithms.

Tuning of 802.11e network parameters

This paper introduces a mechanism which dynamically tunes the parameters of the 802.11e contention-based access method. The proposed mechanism aims at providing QoS as well as ameliorating the problem of delay asymmetry

A minimum interference routing algorithm

Minimum interference routing is instrumental to MPLS traffic engineering under realistic assumptions of unknown traffic demand. This work presents a new algorithm for minimum interference routing, called light minimum interference routing (LMIR). This algorithm introduces a new approach for critical link identification that reduces the computational complexity. Results, derived via simulation, show that LMIR is precise and has indeed a low computational complexity.

Uplink Scheduling with Quality of Service in IEEE 802.16 Networks

In order to support real-time and bandwidth demanding applications the IEEE 802.16 standard is expected to provide quality of service (QoS). Although the standard defines a QoS signaling framework and four service levels, scheduling mechanisms for this network are unspecified. In this paper, we propose a scheduling discipline for uplink traffic. Simulation results show that our scheme is capable to provide QoS. Moreover it shares fairly the resources among connections of the same service type.

Scheduler for IEEE 802.16 networks

The IEEE 802.16 standard was designed to support real-time and bandwidth demanding applications with quality of service (QoS). Although the standard defines a QoS signaling framework and five service levels, scheduling disciplines for these service levels are unspecified. In this paper, we propose a scheduling scheme for the uplink traffic which is fully standard-compliant and can be easily implemented in the base station. Simulation results show that this scheme is able to meet the QoS requirements of the service flows.

WiMAX Module for the ns-2 Simulator

This paper presents the design and validation of an WiMAX module based on the IEEE 802.16 standard. The module, which was implemented, includes mechanisms for bandwidth request and allocation, as well as for QoS provision. Moreover, the implementation is standard-compliant.

An envelope process for multifractal traffic modeling

In this paper, a novel envelope process for multifractal traffic modeling is introduced. The envelope process is an upper bound for the amount of work arrived in a multifractal Brownian motion process. The time scale of interest of a queueing system fed by a multifractal stream is computed. Simulation experiments using both real and synthetic data show that the proposed model is accurate.

Self-Adjusting Grid Networks

This paper introduces a procedure called traffic engineering for grids for enabling grid networks to self-adjust to resource availability. The proposal is based on monitoring the state of resources and on task migration. It involves several layers of the Internet architecture. Experiments executed in NS-2 are used to illustrate the efficacy of the procedure proposed.

A survey of channel switching schemes for IPTV

In spite of the increasing deployment of IPTV services, various functionalities still need to be improved. One of the main challenges is a reduction in startup delays, especially in channel switching, a problem that is quite relevant in IPTV systems due to bandwidth limitations, as well as the employment of buffers and distribution structures. The problem is essentially more serious in P2P IPTV systems, since the dynamic nature of P2P networks requires larger buffers and the exchange of more signaling messages to establish the overlay structures. Since users expect to be able to switch channels quickly, IPTV services must reduce startup delays to just a few seconds or even milliseconds. The aim of this article is to provide a survey of existing channel switching schemes for IPTV systems.

A Brief Survey on Resource Allocation in Service Oriented Grids

Grids are systems that involve coordinate resource sharing and problem solving in heterogeneous dynamic environments. Resource allocation is central to service provisioning in grids. In this paper, a brief survey of resource allocation of twelve existing systems is presented. Moreover, directions for future research are suggested.