Evaluating the energy benefit of dynamic optical bypass for content delivery

We evaluate the energy efficiency of dynamic optical bypass for decentralized content delivery networks (CDNs). We build energy models based on the energy consumption of current network equipment and devices and analyze the energy tradeoff among key networking resources. Our results show that, due to the under-utilization associated with signaling and reconfiguration overhead, a CDN with dynamic optical bypass achieves the largest savings in delivering very large files (100 Gb (gigabit) and above) with high download rate (a few hundred downloads per hour). We also derive a threshold for a file size, which is approximately the bandwidth-overhead product scaled by the ratio between the power density of WDM equipment and routers: C_λT°p^wdm_d/p^r1_d. We show that, only for the delivery of content of sizes larger than this size threshold, a CDN with dynamic optical bypass is more energy efficient than CDN without bypass.