-The evaluation and reduction of energy consumption of backbone telecommunication networks has been a popular subject of academic research for the last decade. A critical parameter in these studies is the power consumption of the individual network devices. It appears that across different studies, a wide range of power values for similar equipment is used. This is a result of the scattered and limited availability of power values for optical multilayer network equipment. We propose reference power consumption values for Internet protocol/multiprotocol label switching (IP/MPLS), Ethernet, optical transport networking (OTN) and wavelength division multiplexing (WDM) equipment. In addition we present a simplified analytical power consumption model that can be used for large networks where simulation is computationally expensive or unfeasible. For illustration and evaluation purpose, we apply both calculation approaches to a case study, which includes an optical bypass scenario. Our results show that the analytical model approximates the simulation result to over 90% or higher, and that optical bypass potentially can save up to 50% of power over a non-bypass scenario.

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A detailed survey of approaches reducing energy consumption of core networks is presented in this paper. We consider a multilayer architecture, in which the optical layer can be realized either with a Wavelength Division Multiplexing (WDM) network or an Elastic Optical Network (EON). We focus on the design and operation stages, i.e., deciding which devices to install in the network during the former step, and choosing which devices to put into sleep mode during the latter one. A taxonomy for classifying the surveyed approaches is provided in order to compare the works covering energy efficiency in core networks (in terms of both optimal formulations and heuristic solutions). Moreover, our work provides a global view of the traffic assumptions, the topologies, and the power consumption models in the literature. The need of further investigations in this field clearly emerges. We envision future works targeting: (1) more effective standardization efforts to practically realize sleep modes; (2) the evaluation of the impact of sleep mode on the device lifetime; (3) the extensive adoption of new paradigms like Software Defined Networking (SDN) and EON; and (4) a radical improvement in the testbed implementations