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According to several studies, the power consumption of the Internet accounts for up to 10% of the worldwide energy consumption, and several initiatives are being put into place to reduce the power consumption of the ICT sector in general. To this goal, we propose a novel approach to switch off network nodes and links while still guaranteeing full connectivity and maximum link utilization. After showing that the problem falls in the class of capacitated multi-commodity flow problems, and therefore it is NP-complete, we propose some heuristic algorithms to solve it. Simulation results in a realistic scenario show that it is possible to reduce the number of links and nodes currently used by up to 30% and 50% respectively during off-peak hours, while offering the same service quality.

Power consumption of ICT is becoming more and more a sensible problem, which is of interest for both the research community, for ISPs and for the general public. In this paper we consider a real IP backbone network and a real traffic profile. We evaluate the energy cost of running it, and, speculating on the possibility of selectively turning off spare devices whose capacity is not required to transport off-peak traffic, we show that it is possible to easily achieve more than 23% of energy saving per year, i.e., to save about 3GWh/year considering today's power footprint of real network devices.

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Service Function Chaining (SFC) allows the forwarding of a traffic flow along a chain of Virtual Network Functions (VNFs, e.g., IDS, firewall, and NAT). Software Defined Networking (SDN) solutions can be used to support SFC reducing the management complexity and the operational costs. One of the most critical issues for the service and network providers is the reduction of energy consumption, which should be achieved without impact to the quality of services. In this paper, we propose a novel resource allocation architecture which enables energy-aware SFC for SDN-based networks. To this end, we model the problems of VNF placement, allocation of VNFs to flows, and flow routing as optimization problems. Additionally, we model the problem of flow rerouting to reduce the impact of resource fragmentation on the network utilization. Thereafter, heuristic algorithms are proposed for the different optimization problems, in order to find near-optimal solutions in acceptable times. The performances of the proposed algorithms are numerically evaluated over a real-world topology and various network traffic patterns. The results confirm that the proposed heuristic algorithms provide near-optimal solutions while their execution time is applicable for real-life networks.

In this article, we consider the adoption of sleep modes for the base stations of a cellular access network, focusing on the design of base station sleep and wake-up transients.. We discuss the main issues arising with this approach, and we focus on the design of base station sleep and wake-up transients, also known as cell wilting and blossoming. The performance of the proposed procedures is evaluated in a realistic test scenario, and the results show that sleep and wake-up transients are short, lasting at most 30 seconds.

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