Impact of energy-aware topology design and adaptive routing at different layers in IP over WDM networks

As the Internet expands in terms of users and exchanged traffic, its energy consumption is becoming a very important issue; in particular, the energy consumption of core networks is expected to be the most critical aspect in coming years. Different strategies and many solutions have been proposed in the last years to improve the energy efficiency of core networks. Specifically, three different strategies can be mainly distinguished: i) the Energy Minimized Virtual Topology Design (EM-VTD), which aims at designing the IP layer topology minimizing the peak power consumption of the network; ii) the Energy Aware Traffic Engineering (EA-TE), which acts on the traffic routing at the IP layer and aims at bringing the power consumption of the network nearly proportional to the actual offered load; iii) the Power Aware Routing and Wavelength Assignment (PA-RWA), which instead acts on the traffic routing at the optical layer. The present study considers these three energy saving strategies, adopting a specific solution for each of them, and evaluates the impact that each of them has on the power consumption of the whole network, considering both the IP and the WDM layers. Results show that a good design of the IP topology is a key aspect to improve the energy efficiency of the network with respect to other simpler strategies (e.g. the end-to-end or the link-by-link grooming strategy). Moreover, the combined use of adaptive routing solutions at both the IP and the WDM layers allows to achieve a better comprehensive power saving in any traffic load conditions, with IP-specific solutions being more important when the total traffic offered to the network grows.