This work describes a novel approach for the reduction of energy consumption in data centres (DCs) that will yield benefits both in terms of running costs and its environmental impact. The method is based on the introduction of collaborative interactions and flexibility clauses in contracts between all the DC ecosystem entities. The included entities are all the actors along the energy production–consumption chain, from the energy provider to the Information Technology customer. The collaborative approach also integrates the interaction between federated DCs. In this paper, we find a detailed description of the architecture that enables interaction between the DC ecosystem parties, which is designed to be progressively deployed, allowing traditional and ‘greened’ services to coexist, and without modification of the existing DC automation and framework systems.

Several fractal or scaling phenomena, such as self-similarity and long-range dependence, have been detected in network traffic, with important implications for network performance. In this paper we describe a detailed study that assesses how the characteristics of traffic change when it traverses IEEE 802.11 networks. Various scenarios, including the hidden node situation and the effect of relaying, have been simulated. The simpler scenario has also been replicated in a real testbed, in order to corroborate the results obtained in the simulations. The most significant results are the smoothing effect of the MAC mechanisms on the traffic at the highest frequencies, while at the lowest frequencies we find a mitigation of fractality that seems to be caused by packet loss induced by propagation impairments. The overall effect is a mitigation of fractal characteristics on the output traffic

We propose a new protocol, named DS-SWAN (differentiated services-stateless wireless ad hoc networks), to support end-to-end QoS (quality of service) in ad hoc networks connected to fixed DiffServ domains. DS-SWAN warns nodes in the ad hoc network when congestion is excessive for the correct functioning of real-time applications. These nodes react by slowing down best-effort traffic. Simulation results indicate that DS-SWAN significantly improves end-to-end delays for real-time flows without starvation of background traffic.

We propose a new protocol, named DS-SWAN (Differentiated Services-Stateless Wireless Ad Hoc Networks), to support end-to-end QoS (Quality of Service) in ad hoc networks connected to fixed DiffServ domains. DS-SWAN warns nodes in the ad hoc network when congestion is excessive for the correct functioning of real-time applications. These nodes react by slowing down best-effort traffic. Simulation results indicate that DS-SWAN significantly improves end-to-end delays for real-time flows without starvation of background traffic. In this work we introduce different conditions to force that a wireless node throttles its best-effort traffic and study their behaviour and differences.

This article presents a new version of the dynamic source routing (DSR) protocol that favours the selection of a route containing nodes with high battery levels, in order to maximize the lifetime of the ad hoc mobile network as a whole. This proposal implies little modifications to the original algorithm. After a quantitative analysis, we see simulation results that indicate that the proposed scheme, SEADSR (simple energy aware DSR), outperforms the standard DSR in terms of network survivability and network capacity.

We present new adaptive importance sampling techniques based on stochastic Newton recursions. Their applicability to the performance evaluation of communication systems is studied. Besides bit-error rate (BER) estimation, the techniques are used for system parameter optimization. Two system models that are analytically tractable are employed to demonstrate the validity of the techniques. As an application to situations that are analytically intractable and numerically intensive, the influence of crosstalk in a wavelength-division multiplexing (WDM) crossconnect is assessed. In order to consider a realistic system model, optimal setting of thresholds in the detector is carried out while estimating error rate performances. Resulting BER estimates indicate that the tolerable crosstalk levels are significantly higher than predicted in the literature. This finding has a strong impact on the design of WDM networks. Power penalties induced by the addition of channels can also be accurately predicted in short run-times.