The concept of energy-efficient networking has begun to spread in the past few years, gaining increasing popularity. Besides the widespread sensitivity to ecological issues, such interest also stems from economic needs, since both energy costs and electrical requirements of telcos' and Internet Service Providers' infrastructures around the world show a continuously growing trend. In this respect, a common opinion among networking researchers is that the sole introduction of low consumption silicon technologies may not be enough to effectively curb energy requirements. Thus, for disruptively boosting the network energy efficiency, these hardware enhancements must be integrated with ad-hoc mechanisms that explicitly manage energy saving, by exploiting network-specific features. This paper aims at providing a twofold contribution to green networking. At first, we explore current perspectives in power consumption for next generation networks. Secondly, we provide a detailed survey on emerging technologies, projects, and work-in-progress standards, which can be adopted in networks and related infrastructures in order to reduce their carbon footprint. The considered approaches range from energy saving techniques for networked hosts, to technologies and mechanisms for designing next-generation and energy-aware networks and networking equipment.

Recently, network operators around the world reported statistics of network energy requirements and the related carbon footprint, showing an alarming and growing trend. Such high energy consumption can be mainly ascribed to networking equipment designed to work at maximum capacity with high and almost constant dissipation, independent of the traffic load. However, recent developments of green network technologies suggest the chance to build future devices capable of adapting their performance and energy absorption to meet actual workload and operational requirements. In such a scenario, this contribution aims at evaluating the potential impact on next-generation wireline networks of green technologies in economic and environmental terms. We based our impact analysis on the real network energy-efficiency targets of an ongoing European project, and applied them to the expected deployment of Telecom Italia infrastructure by 2015-2020.

The envisioned 5G ecosystem will be composed of heterogeneous networks based on different technologies and communication means, including satellite communication networks. The latter can help increase the capabilities of terrestrial networks, especially in terms of higher coverage, reliability, and availability, contributing to the achievement of some of the 5G KPIs. However, technological changes are not immediate. Many current satellite communication networks are based on proprietary hardware, which hinders the integration with future 5G terrestrial networks as well as the adoption of new protocols and algorithms. On the other hand, the two main paradigms that are emerging in the networking scenario -- software defined networking (SDN) and network functions virtualization -- can change this perspective. In this respect, this article presents first an overview of the main research works in the field of SDN satellite networks in order to understand the already proposed solutions. Then some open challenges are described in light of the network slicing concept by 5G virtualization, along with a possible roadmap including different network virtualization levels. The remaining unsolved problems are related to the development and deployment of a complete integration of satellite components in the 5G ecosystem.

Today, backbone networks of telecom operators deploy a large number of devices and links. This is mainly due to both redundancy purposes for network service reliability and resource overdimensioning for maintaining quality of service during rush hours. Unfortunately, current network devices do not have power management primitives, and have constant energy consumption independent of their actual workloads. Starting from these considerations, we propose a viable approach to introduce and support standby modes in backbone network devices. This approach can be effectively used to almost halve the energy requirements of the whole telecom core network. Our main idea consists of periodically reconfiguring nodes and links to meet incoming traffic volumes and operational constraints of real-world networks, such as reliability, stability, quality of service, and reconvergence times. To this purpose, the approach we propose directly exploits the main features of both backbone device architectures and the network protocol stack.