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Network robustness and throughput can be improved by routing each source-to-terminal (sd, td)
demand d via two disjoint paths (2DP). However, 2DP routing increases energy usage despite
yielding lower link utilization and higher redundancy. In this paper, we address the problem
of minimizing the energy usage of networks that use 2DP. Specifically, our problem -
Energy-Aware Two Disjoint Paths Routing (EAR-2DP) is to maximally switch off redundant links
while guaranteeing at least 0<=T<=1.0 fraction of all possible (sd, td) 2DPs remain on and
their maximum link utilization (MLU) is no greater than a configured threshold. We first
prove that EAR-2DP is NP-complete. Then, we design a fast heuristic, called Two Disjoint Paths
by Shortest Path (2DP-SP), to solve the problem. We have extensively evaluated the performance
of 2DP-SP on real and/or synthetic topologies and traffic demands with two link-disjoint paths
(2DP-L) and two node-disjoint paths (2DP-N). Our simulation results show that 2DP-SP can reduce
network energy usage, on average, by more than 20%, even for MLU below 50%. As compared to
using Shortest Path (SP) routing, while reducing energy by about 20%, 2DP-SP does not
significantly affect (sd, td) path length, even for MLU<50%. Furthermore, almost 94.2% of routes
produced by 2DP-SP have route reliability up to 35% higher as compared to SP and less than
50% routes have reliability only 5% lower as compared to using 2DP routing without energy savings.
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