Sergio Ricciardi

All-optical packet/circuit switching-based data center network for enhanced scalability, latency, and throughput

Applications running inside data centers are enabled through the cooperation of thousands of servers arranged in racks and interconnected together through the data center network. Current DCN architectures based on electronic devices are neither scalable to face the massive growth of DCs, nor flexible enough to efficiently and cost-effectively support highly dynamic application traffic profiles. The FP7 European Project LIGHTNESS foresees extending the capabilities of todays electrical DCNs throPugh the introduction of optical packet switching and optical circuit switching paradigms, realizing together an advanced and highly scalable DCN architecture for ultra-high-bandwidth and low-latency server-to-server interconnection. This article reviews the current DC and high-performance computing (HPC) outlooks, followed by an analysis of the main requirements for future DCs and HPC platforms. As the key contribution of the article, the LIGHTNESS DCN solution is presented, deeply elaborating on the envisioned DCN data plane technologies, as well as on the unified SDN-enabled control plane architectural solution that will empower OPS and OCS transmission technologies with superior flexibility, manageability, and customizability.

Energy-Aware RWA for WDM Networks with Dual Power Sources

Energy consumption and the concomitant Green House Gases (GHG) emissions of network infrastructures are becoming major issues in the Information and Communication Society (ICS). Current optical network infrastructures (routers, switches, line cards, signal regenerators, optical amplifiers, etc.) have reached huge bandwidth capacity but the development has not been compensated adequately as for their energy consumption. Renewable energy sources (e.g. solar, wind, tide, etc.) are emerging as a promising solution both to achieve drastically reduction in GHG emissions and to cope with the growing power requirements of network infrastructures. The main contribution of this paper is the formulation and the comparison of several energy-aware static routing and wavelength assignment (RWA) strategies for wavelength division multiplexed (WDM) networks where optical devices can be powered either by renewable or legacy energy sources. The objectives of such formulations are the minimization of either the GHG emissions or the overall network power consumption. The solutions of all these formulations, based on integer linear programming (ILP), have been observed to obtain a complete perspective and estimate a lower bound for the energy consumption and the GHG emissions attainable through any feasible dynamic energy-aware RWA strategy and hence can be considered as a reference for evaluating optimal energy consumption and GHG emissions within the RWA context. Optimal results of the ILP formulations show remarkable savings both on the overall power consumption and on the GHG emissions with just 25% of green energy sources.

Towards an energy-aware Internet: modeling a cross-layer optimization approach

The containment of power consumption and the use of alternative green sources of energy are the new main goals of telecommunication operators, to cope with the rising energy costs, the increasingly rigid environmental standards, and the growing power requirements of modern high-performance networking devices. To address these challenges, we envision the necessity of introducing energy-efficiency and energy-awareness in the design, configuration and management of networks, and specifically in the design and implementation of enhanced control-plane protocols to be used in next generation networks. Accordingly, we focus on research and industrial challenges that foster new developments to decrease the carbon footprint while leveraging the capacities of highly dynamic, ultra-high-speed, networking. We critically discuss current approaches, research trends and technological innovations for the coming green era and we outline future perspectives towards new energy-oriented network planning, protocols and algorithms. We also combine all the above elements into a comprehensive energy-oriented network model within the context of a general constrained routing and wavelength assignment problem framework, and analyze and quantify through ILP formulations the savings that can be attained on the next generation networks.

Analyzing local strategies for energy-efficient networking

Power management strategies that allow network infrastructures to achieve advanced functionalities with limited energy budget are expected to induce significant cost savings and positive effects on the environment, reducing Green House Gases (GHG) emissions. Power consumption can be drastically reduced on individual network elements by temporarily switching off or downclocking unloaded interfaces and line cards. At the state-of-the-art, Adaptive Link Rate (ALR) and Low Power Idle (LPI) are the most effective local-level techniques for lowering power demands during low utilization periods. In this paper, by modeling and analyzing in detail the aforementioned local strategies, we point out that the energy consumption does not depend on the data being transmitted but only depends on the interface link rate, and hence is throughput-independent. In particular, faster interfaces require lower energy per bit than slower interfaces, although, with ALR, slower interfaces require less energy per throughput than faster interfaces. We also note that for current technologies the energy/bit is the same both at 1 Gbps and 10 Gbps, meaning that the increase in the link rate has not been compensated at the same pace by a decrease in the energy consumption.

An energy-aware dynamic RWA framework for next-generation wavelength-routed networks

Power demand in networking equipment is expected to become a main limiting factor and hence a fundamental challenge to ensure bandwidth scaling in the next generation Internet. Environmental effects of human activities, such as CO2 emissions and the consequent global warming have risen as one of the major issue for the ICT sector and for the society. Therefore, it is not surprising that telecom operators are devoting much of their efforts to the reduction of energy consumption and of the related CO2 emissions of their network infrastructures. In this work, we present a novel integrated routing and wavelength assignment framework that, while addressing the traditional network management objectives, introduces energy-awareness in its decision process to contain the power consumption of the underlying network infrastructure and make use of green energy sources wherever possible. This approach results in direct power, cost and CO2 emissions savings in the short term, as demonstrated by our extensive simulation studies.

Evaluating Network-Based DoS Attacks under the Energy Consumption Perspective: New Security Issues in the Coming Green ICT Area

In the green Information and Communication Society (ICS), new form of Denial of Service (DoS) attacks may be put in place: exploiting the computational and storage resources of datacenters with the aim of consuming as much energy as possible, causing detrimental effects, from high costs in the energy bill, to penalization for exceeding the agreed quantity of CO2 emissions, up to complete denial of service due to power outages. To the best of our knowledge, this is the first paper which investigates the impacts of network-based DoS attacks under the energy consumption perspective. We analyzed different types of such attacks with their impacts on the energy consumption, and showed that current energy-aware technologies may provide attackers with great opportunities for raising the target facility energy consumption and consequently its green house gases (GHG) emissions and costs.

Energy-oriented denial of service attacks: an emerging menace for large cloud infrastructures

This work analyzes a new and very subtle kind of security threat that can affect large-scale cloud-based IT service infrastructures, by exploiting the computational resources of their component data center to waste as much energy as possible. The consequence of these threats ranges from increased costs in the energy bill, to penalization for exceeding the agreed quantity of greenhouse gases (GHG) emissions, up to complete denial of service caused by electrical outages due to power budget exhaustion. We analyzed different types of such attacks with their potential impacts on the energy consumption, modeled their behavior and quantified how current energy-proportional technologies may provide attackers with great opportunities for raising the target facility emissions and costs. These efforts resulted in a simple model with some parametric reference values that can be used to estimate the impact of such attacks also in presence of very large infrastructures containing thousands or millions of servers.

Green-aware routing in GMPLS networks

The increasing amount of traffic in the Internet has been accommodated by the exponential growth of bandwidth provided by the optical networks technologies. However, such a growth has been also accompanied by an increase in the energy consumption and the concomitant green house gases (GHG) emissions. Despite the efforts for improving energy efficiency in silicon technologies and network designs, the large energy consumption still poses challenges for the future development of Internet. In this paper, we propose an extension of the Open Shortest Path First - Traffic Engineering (OSPF-TE) protocol and a green-aware routing and wavelength assignment (RWA) algorithm for minimizing the GHG emissions by routing connection requests through green network elements (NE). The network behavior and the performance of the algorithm are analyzed through simulations under different scenarios, and results show that it is possible to reduce GHGs emissions at the expense of an increase in the path length, and, in some cases, in the blocking probability. The trade-off between emissions and performance is studied. To the authors knowledge, this is the first work that provides a detailed study of a green-aware OSPF protocol.

Saving Energy in Data Center Infrastructures

At present, data centers consume a considerable percentage of the worldwide produced electrical energy, equivalent to the electrical production of 26 nuclear power plants, and such energy demand is growing at fast pace due to the ever increasing data volumes to be processed, stored and accessed every day in the modern grid and cloud infrastructures. Such energy consumption growth scenario is clearly not sustainable and it is necessary to limit the data center power budget by controlling the absorbed energy while keeping the desired level of service. In this paper, we describe Energy Farm, a data center energy manager that exploits load fluctuations to save as much energy as possible while satisfying quality of service requirements. Energy Farm achieves energy savings by aggregating traffic during low load periods and temporary turning off a subset of computing resources. Energy Farm respects the logical and physical dependencies of the interconnected devices in the data center and performs automatic shut down even in emergency cases such as temperature peaks and power leakages. Results show that high resource utilization efficiency is possible in data center infrastructures and that huge savings in terms of energy (MWh), emissions (tons of CO2) and costs (k€) are achievable.

OSPF-TE extensions for green routing in optical networks

This paper proposes extensions to the OSPF-TE protocol to enable green routing in GMPLS-controlled optical networks. Simulation results show a remarkable reduction in CO2 emissions by preferring network elements powered by green energy sources in the connection routing.