Papers by Glauco Gonçalves
Cloud providers should be able to attend to different types of requests from their users. General... more Cloud providers should be able to attend to different types of requests from their users. Generally, requests are composed of virtual machine and virtual link restrictions. When users request only virtual machines, the Cloud provider should interconnect them - by creating a virtual network - in order to allow the communication. In this paper, we propose a strategy to create virtual links between virtual machines, aiming for load balancing, and at same time, link consolidation in order to optimize resource utilization in Distributed Clouds. The results show that our algorithm usually hits the optimum solution for small requests for virtual machines.
This paper investigates the degradation of to mice flows caused by standard TCP congestion contro... more This paper investigates the degradation of to mice flows caused by standard TCP congestion control mechanisms, especially during the Slow Start phase what can cause multiple packet losses. Thus, a modified TCP startup mechanism was proposed. The Burst TCP (B-TCP) is an intuitive TCP startup mechanism that employs a responsive window growth scheme to improve performance of small flows. Moreover, B-TCP is easy to implement and requires TCP adjustment at the sender side only. Simulation experiments show that B-TCP can significantly reduce transfer times and packet losses of small flows without causing damage to large flows.
Cloud computing is an attractive computing model since it allows for the provision of resources o... more Cloud computing is an attractive computing model since it allows for the provision of resources on-demand. Such a process of allocation and reallocation of resources is the key to accommodating unpredictable demands and improving the return on investment from the infrastructure supporting the Cloud. However, despite the recent growth of the Cloud Computing market, several problems with the process of resource allocation remain unaddressed. This short course introduces essential concepts and technologies regarding Cloud Computing and presents some research questions on the topic, focusing on the challenges and the state-of-the-art solutions in resource allocation.
Standard TCP congestion control mechanisms degrade performance of small flows, especially during ... more Standard TCP congestion control mechanisms degrade performance of small flows, especially during the Slow Start phase, which often causes multiple packet losses. We propose a modified TCP startup mechanism, called Burst TCP (B-TCP), which employs a responsive growth scheme based on current window size, to improve performance for small flows. Our simulation experiments, considering heavy-tailed traffic, show that B-TCP can significantly reduce both transfer times and packet losses for small flows without causing damage to large flows. Additionally, B-TCP is easy to implement and requires TCP adjustment at the sender side only.
Distributed Clouds, or just D-Clouds, can be seen as a paradigm that is able to exploit the poten... more Distributed Clouds, or just D-Clouds, can be seen as a paradigm that is able to exploit the potential of sharing resources across geographic boundaries and provide latency-bound allocation of resources to third-party developers. The representation of D-Cloud resources is a challenge that involves the careful choice of characteristics that drive the mapping of requests on the substrate resources. Regarding these problems, this paper introduces the Cloud Modeling Language (CloudML), a vendor-neutral XML-based language intended to integrate the description of different cloud related aspects such as computational and network resources, services profiles, and developers' requests in an integrated way. Furthermore, the CloudML provides a way to describe geographical location aware services, seen particularly indispensable in D-Cloud scenarios.
In this paper we share our experience in building an ADSL video delivery test-bed. As a result, w... more In this paper we share our experience in building an ADSL video delivery test-bed. As a result, we are able to measure the impact of important parameters such as the loop length, the presence of background traffic and line protection against transmission errors on video quality. We show that although these access technologies promise a broadband pipe and low delay communication, a careful configuration of line parameters is paramount to achieve optimal access and is needed for the success of multimedia triple play (3P) services. We particularly analyze the delay, jitter, packet loss and bitrate consumption obtained from real ADSL measurements. These results are an important step towards understanding the adequate deployment of such services. As a special case, we study the effect of repetitive noise on SDTV.
In this paper we present implementation guidelines of the Distributed Cloud Resource Allocation S... more In this paper we present implementation guidelines of the Distributed Cloud Resource Allocation System (D-CRAS). D-CRAS ensures an automatic monitoring and control of resources to guarantee the optimal functioning of the Cloud while meeting developers' requirements. Additionally, this work establishes the necessary technologies that meet the construction of the proposed system.
... It is based on the Open vSwitch project 9 . The approach distinguishes virtual from physical ... more ... It is based on the Open vSwitch project 9 . The approach distinguishes virtual from physical interfaces while offering software based VLAN support. ... It is also an important decision parameter when choosing an environment to implement a cloud computing system. ...
IEEE Network, 2011
In a cloud computing environment, dynamic resource allocation and reallocation are keys for accom... more In a cloud computing environment, dynamic resource allocation and reallocation are keys for accommodating unpredictable demands and, ultimately, contribute to investment return. This article discusses this process in the context of distributed clouds, which are seen as systems where application developers can selectively lease geographically distributed resources. This article highlights and categorizes the main challenges inherent to the resource allocation process particular to distributed clouds, offering a stepwise view of this process that covers the initial modeling phase through to the optimization phase.
Resumo Este trabalho apresenta uma solução de computador popular aplicada à implantação de labo... more Resumo Este trabalho apresenta uma solução de computador popular aplicada à implantação de laboratórios de informática de instituições de ensino públicas. Neste sistema utilizou-se o princípio do computador popular de rede (CPR), em que um servidor Linux gerencia um conjunto de estações de trabalho. Nesta configuração uma estação de trabalho ou CPR é equivalente a um computador pessoal, porém, sem disco rígido, sem periféricos e com pouca memória. As vantagens desta solução, além do baixo custo de hardware e do uso de software livre, são a minimização do problema de vírus e do trabalho de administração que é centralizado no servidor. Além disso, esta solução permite reusar computadores já defasados tecnologicamente como estações de trabalho. Esta solução vem sendo usada com sucesso para atender a demanda reprimida
QoS Provisioning for 3P over xDSL remains a challenging task due to the effects of line impairmen... more QoS Provisioning for 3P over xDSL remains a challenging task due to the effects of line impairments on such services. Differently from simple data, video and voice services have strict requirements for loss and delay tolerance. The accurate assessment of final service quality is part of this provisioning process, but its direct measurement is yet not practical. In this paper we explore the possibility of estimating service quality, with focus on video delivery, by investigating its relationship with performance data available to xDSL operators and deriving models for estimating quality from this data. Experiments using a real xDSL platform and different noise types were conducted. The derived models showed to be accurate enough to estimate video quality for the scenarios evaluated.
Cloud computing is an attractive computing model since it allows for resources to be provisioned ... more Cloud computing is an attractive computing model since it allows for resources to be provisioned according on a demand basis, i.e., cloud users can rent resources as they become necessary. This model motivated several academic and non-academic institutions to develop open-source cloud solutions. This paper presents and discusses the state-of-the of open-source solutions for cloud computing. The authors hope that the observation and classification of such solutions can leverage the cloud computing research area providing a good starting point to cope with some of the problems present in cloud computing environments.
articles by Glauco Gonçalves
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Papers by Glauco Gonçalves
articles by Glauco Gonçalves