# Greening the NetFPGA Reference Router
## 2 Related Work  
Traffic demands have been witnessing a sky-rocketing growth over the past decade. To keep pace with such growth, it is even more compelling to reduce power consumption while managing massive increases in Internet traffic and networking hardware. Economic reasons and environmental concerns on sustainable growth have created a demand for green communication networks. Many approaches have been proposed to manage energy and power issues, and the European Commission (EC) has launched a series of research projects to improve the energy efficiency of ICT in a variety of areas (e.g., wired networks, wireless networks, data centre, smart grids, etc.).  
The Energy-Aware Radio and neTwork tecHnologies (EARTH) project aims to address the energy efficiency of mobile communication systems to reduce energy waste and improve the energy efficiency of mobile communications. [PERSON] et al. proposed a holistic approach for energy-efficient mobile radio networks and a framework for energy efficiency evaluation (E\({}^{3}\)F) [15]. [PERSON] et al. investigated the power consumption of mobile communication systems, and the power consumption of base stations is quantified in detail [16].  
The Towards Real Energy-efficient Network Design (TREND) project investigated the energy efficiency of the electrical and optical layers of Internet Protocol over wavelength-division multiplexing (IP-over-WDM) networks [17]. The project also proposed energy-aware adaptive routing solutions (EA-ARSs) for the network operators. [PERSON] et al. proposed a approach to reduce the power consumption of backbone networks by turning off network nodes and links while guaranteeing full connectivity and link utilization constraints [18].  
The Multi-Agent Systems and Secured coupling of Telecom and Energy gRIds for Next Generation smart grid services (MAS2 TERING) project investigated the challenges of integrating ICT and energy infrastructures for future smart grids. [PERSON] et al. proposed four strategic challenges at the intersection between ICT and energy infrastructures [19].  
Among those green approaches, the following three works are the most similar to this work. The auto-negotiation scheme in the 802.3 standard takes about 100 ms to change data rates at a 1-Gb/s link data rate. [PERSON] et al. [1] proposed the adaptive link rate (ALR) that allows the speed of network links to be changed by adaptively switching to different processing states in response to the amount of data that is being transmitted.  
[PERSON] et al. [20] proposed a multi-frequency scaling (MFS) scheme that examines buffer usage inside a network device so that the components of the device could dynamically scale its capacity according to its buffer occupancy. In the MFS scheme, a clock (CLK) adapter is the hardware module for frequency scaling, and a multi-dual-threshold policy is adopted as the MFS control policy.  
[PERSON] et al. [21] proposed a power scaling mechanism on the NetFPGA OpenFlow switch that can adapt the operating clock frequencies of the FPGA processor and the link rates of the four Ethernet ports based on the actual traffic load. The power can be saved by changing the clock frequency from 125 MHz to 3.9 MHz in combination with four possible operation modes on each Ethernet port (idle, 10 Mb/s, 100 Mb/s and 1 Gb/s).