Cloud Computing (CC) services are rapidly catching on as an alternative to conventional office-based computing. As cloud computing adoption increases, the energy consumption of the network and of the computing resources that underpin the cloud is growing and causing the emission of enormous quantities of CO2. Research is now focusing on novel "low-carbon" cloud-computing solutions. Renewable energy sources are emerging as a promising solution both to achieve drastic reduction in CO2emissions and to cope with the growing power requirements of data centers. These infrastructures can be located near renewable energy plants and data can be effectively transferred to these locations via reconfigurable optical networks, based on the principle that data can be moved more efficiently than electricity. This paper focuses on how to dynamically route on-demand optical circuits that are established to transfer energy-intensive data processing towards data centers powered with renewable energy. Our main contribution consists in devising two routing algorithms for connections supporting CC services, aimed at minimizing the CO2emissions of data centers by following the current availability of renewable energies (e.g., coming from sun and wind). The trade-off with energy consumption for the transport equipments is considered. We also compare three different IP-over-WDM network architectures. The results show that relevant reductions, up to about 30% in CO2emissions can be achieved using our approaches compared to baseline shortest-path-based routing strategies, paying off only a marginal increase in terms of network blocking probability.

Energy consumption in telecommunication networks keeps growing rapidly, mainly due to emergence of new Cloud Computing (CC) services that need to be supported by large data centers that consume a huge amount of energy and, in turn, cause the emission of enormous quantity of CO2. Given the decreasing availability of fossil fuels and the raising concern about global warming, research is now focusing on novel “low-carbon” telecom solutions. E.g., based on today telecom technologies, data centers can be located near renewable energy plants and data can then be effectively transferred to these locations via reconfigurable optical networks, based on the principle that data can be moved more efficiently than electricity. This paper focuses on how to dynamically route on-demand optical circuits that are established to transfer energy-intensive data processing towards data centers powered with renewable energy. Our main contribution consists in devising two routing algorithms for connections supporting CC services, aimed at minimizing the CO2emissions of data centers by following the current availability of renewable energy (Sun and Wind). The trade-off with energy consumption for the transport equipments is also considered. The results show that relevant reductions, up to about 30% in CO2emissions can be achieved using our approaches compared to baseline shortest-path-based routing strategies, paying off only a marginal increase in terms of network blocking probability.

Today's “green thrust” has been completely steering the evolution of our society. Therefore, since enhancements on telecommunication networks are expected to cope with the growth of traffic demand, energy consumption is becoming a crucial design metric. In this paper we focus on IP over Wavelength Division Multiplexing (IPoWDM) optical network architectures, where optical circuits (or lightpaths) interconnect IP routers. Various implementations of IPoWDM networks are possible, e.g., transparent, translucent or opaque each accounting different routing and switching constraints, in order to evolve from the classic IPoWDM approach, where only signal transmission is performed optically. Although it is a common belief that “more optical” architectures can generally guarantee a much lower total power consumption, we show that identifying the most energy-efficient IPoWDM architecture is not a trivial task. In fact we demonstrate that the most energy-efficient architecture depends on some network parameters such as number of nodes, link length and average distance between nodes. This work provide an analytical framework by which we draw guidelines to (a) assess under which conditions optical switching actually becomes more desirable than electronic switching and (b) evaluate which architecture, among those employing optical switching, is more energy-efficient under different parameter settings.