  Improving the energy efficiency of Internet Service Provider (ISP) backbone
networks is an important objective for ISP operators. In these networks, the
overall traffic load throughout the day can vary drastically, resulting in many
backbone networks being highly overprovisioned during periods of lower traffic
volume. In this paper, we propose a new Segment Routing (SR)-based optimization
algorithm that aims at reducing the energy consumption of networks during such
low-traffic periods. It uses the traffic steering capabilities of SR to remove
traffic from as many links as possible to allow the respective hardware
components to be switched off. Furthermore, it simultaneously ensures that
solutions comply to additional operator requirements regarding the overall
Maximum Link Utilization in the network. Based on data from a Tier-1 ISP and a
public available dataset, we show that our approach allows for up to 70 % of
the overall linecards to be switched off, corresponding to an around 56%
reduction of the overall energy consumption of the network in times of low
traffic demands.
