Germán Santos-Boada

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.

Energy-Oriented Models for WDM Networks

A realistic energy-oriented model is necessary to formally characterize the energy consumption and the consequent carbon footprint of actual and future high-capacity WDM networks. The energy model describes the energy consumption of the various network elements (NE) and predicts their energy consumption behavior under different traffic loads and for the diverse traffic types, including all optical and electronic traffic, O/E/O conversions, 3R regenerations, add/drop multiplexing, etc. Besides, it has to be scalable and simple to implement, manage and modify according to the new architecture and technologies advancements. In this paper, we discuss the most relevant energy models present in the literature highlighting possible advantages, drawbacks and utilization scenarios in order to provide the research community with an overview over the different energy characterization frameworks that are currently being employed in WDM networks. We also present a comprehensive energy model which accounts for the foreseen energy-aware architectures and the growth rate predictions which tries to collect the main benefits of the previous models while maintaining low complexity and, thus, high scalability.

Evaluating energy savings in WoL-enabled networks of PCs

In this paper we present EnergySave, a smart energy-saving system that, by leveraging the consolidated WoL (Wake on LAN) technology, allows the remote wake-up of PCs from a centralized management server, providing easy and secure power management capabilities for local or remote IP-based networks of personal computers (PCs). We also present a lightweight web-based platform implementing the remote management interface as less intrusively as possible. Finally, we model the mathematical saving functions to be used in order to evaluate through simulation the amount of potential energy savings, and hence the whole framework effectiveness, both in the general case and in a real case scenario. Results show that significant savings are achievable provided that the hardware supports the Wake-on-LAN specifications and that proper configuration of the Web server is set-up, allowing the WoL magic packet to travel to the destination hosts and wake them up only when they are really needed.

A critical review of OpenFlow/SDN-based networks

The separation of the data and control planes simplify the implementation of SDN applications. The centralised architecture of a controller based on the OpenFlow protocol is appealing to the network operators. We have reviewed the concept of SDNs and its extension to optical networks, and constrained and unconstrained wireless access networks. The current status of the proposed and implemented SDN architectures is such that the fulfilment of a SLA is an open issue. This aspect is left to be tackled by the SDN applications and the proposed architectures do not provide means to describe the interplay between different technology domains. In this paper we make an in depth analysis of the current proposed architectures and identify important challenges to be addressed by a novel integrated SDN architecture.

Towards Service Orchestration Between Smart Grids and Telecom Networks

In the last years, the research efforts in smart grids SG and telecommunication networks TN have been considerable but never converged to a common view and, due to the lack of strong interactions between the two worlds, only limited benefits have been achieved. We envision in this paper that future TN as well as any other ICT application will interact with the SG, enabling 1 the TN to know the energy source and cost that is currently powering its equipment, 2 to turn the TN into an active client which can request to the SG the quantity and quality e.g. green of energy that it needs, and 3 a service orchestration between SG supply system and TN operations. As a consequence, the enabled interoperability between TN and SG would allow TN to take energy-aware management decisions in function of energy-related information provided by the SG. For example, TN can route packets with the objective of optimizing green criteria, while SG can route the energy towards the TN clients with the objective of not wasting surpluses of green energy. These new energy and data routing capabilities can be exploited not only by SG operators and telecom carriers but also by any energy consumer/producer within the ICT world. This may include industry and institutional ICT premises, datacenters, home automation, wireless and mobile cellular networks, which will be able to implement their own energy-aware management and operations M&O by considering the quantity, quality and cost of the energy currently provided by the smart grid.

A hybrid load-balancing and energy-aware RWA algorithm for telecommunication networks

In the last years, the power consumption of telecommunication networks has attracted the attention of both researchers and field experts in order to contain the associated energy bills and reduce their ecological impact. Many of the proposed solutions have been focused exclusively on the reduction of the power consumption, without adequately considering more traditional network engineering objectives such as balancing resource utilization, routing policy, or resilience schemes. As a consequence, network control plane strategies passed from one extreme to the other, from being totally energy-unaware to exclusively energy-efficient at the expenses of load-balancing, with obvious impacts on the power consumption in the former case and on the blocking rate in the latter one.In this paper, we present a hybrid routing and wavelength assignment algorithm that, when the network is lightly loaded, operates in an energy-efficient way, by routing the connections on the paths requiring the lowest amount of energy, while, when the network load increases, it dynamically switches to a pure load-balancing scheme in order to best allocate the available communication resources. The switching decision among load-balancing and energy-awareness is taken dynamically, driven by a threshold on the number of new connections requests reaching the network during a prefixed time window.Simulation results show the effectiveness of the hybrid algorithm, which achieves lower energy consumption than a pure load-balancing algorithm while keeping the network load fairly distributed on the available resources.

Technical challenges and deployment perspectives of SDN based elastic optical networks

There is a widespread acceptance that the flex-grid technology is the future of the transport network due to its astounding characteristics: flexible bandwidth allocation and reach tailoring through adaptive line rate, modulation formats, and spectral efficiency. However the number of variables to be optimized and the challenges to be overcome are enormous: routing, code and spectrum assignment; multi-domain and multi-technology orchestration; bandwidth variable transponders; modulation formats; monitoring aspects, just to name a few. In this paper, we exploit the software defined elastic optical networks (SD-EONs) aiming at identifying its state of art and the future challenges in terms of efficient dynamic resources assignment. In addition, we present some up-to-date information concerning the perspectives that operators carry out real deployments of this technology in the core network where currently predominate GMPLS solutions.