Introduction
With the tremendous growth of Internet traffic, the network energy consumption is inherently growing fast with a rate of 10% per year, which exceeded 350 TWh and represented 1.8% of the worldwide electricity consumption in 2012. It is even reported that communication networks will consume as much as 51% of the global electricity in the worst case by 2030 if its energy efficiency is not improved enough. Thus, the problem of energy efficiency is becoming critical for nowadays communication networks. To reduce energy consumption, green networking has attracted a lot of attention from device manufacturers and Internet Service Providers (ISP). In the literature, energy-aware traffic engineering problem is proposed to minimize the total energy consumption by switching off unused network devices (routers and links) while guaranteeing full network connectivity [1, 2]. In this work, we are interested in the problem of energy-aware Traffic Engineering (TE) while using multipath routing to minimize link capacity utilization in ISP backbone networks.