Special Issue: Green Networking and Computing, Part 1 of 2

The Internet was born as a simple, small-scale, communication system for transmitting low bit-rate traffic between machines. Today it is a large, dynamic, heterogeneous collection of interconnected systems that can be used for many different types of communications among any interested party connected to it. The term Internet includes both the " core Internet " (i.e., Internet Service Provider networks) and the " edge Internet " (i.e., corporate, data centres, private and community networks). Clearly, such a ubiquitous network paradigm comes at a no negligible cost. It has been estimated that the global Information and Communications Technology (ICT) energy consumption amounts to 7% of the entire electricity production, while the energy requirements of data centers and network equipment are foreseen to grow with a yearly rate of 12%. Furthermore, with an ever-increasing demand for bandwidth, connection quality and end-to-end interactivity, computer networks and mobile devices are in need of more and more sophisticated and power-hungry technologies. The reduction of the energy consumption and the environmental impact of Green House Gas (GHG) emissions is nowadays a matter of great interest in the worldwide conscience, and among the most important challenges facing our civilization. Local area networks, broadband wireless technologies, long-haul systems and other networks cannot be designed, produced and commercialised without highlighting their advancement in the energy usage. This Special Issue on " Green networking and computing " brings together state-of-the-art research contributions that address many aspects of the enabling technologies for greening the Internet. The nine selected papers cover various sub-fields: (i) energy-oriented protocols and technologies for broadband access networks, (ii) traditional IP over WDM core networks with energy considerations, and (iii) novel technologies with energy as a new constraint for core networks. The first three papers deal with energy efficiency in the access segment of the network. In the first paper about Energy efficient multicasting in TDMA PONs, L. Valcarenghi, I. Cerutti and P. Castoldi propose an approach where energy is saved by setting to sleep mode the ONUs that are not subscribed to a multicast group, i.e., not receiving data. Based on this intuition the authors propose a multicast group scheduling approach that minimizes the number of transitions from sleep to active mode. Their results show that with multicast transmissions it is possible to achieve better energy consumption figures than with current, broadcast-based, PON access solutions. Next, in the paper on Energy consumption of subscriber devices in broadband …