Energy efficient optical backbone networks: A dynamic threshold approach

A new approach about virtual topology reconfiguration in IP over WDM optical networks is introduced. Traditional reconfiguration algorithms adjust the virtual topology using two thresholds as a control mechanism. When the load of a lightpath exceeds the upper threshold, a new lightpath is activated to avoid congestion and possible data loss upon the arrival of traffic bursts. Similarly, when the load of a lightpath decreases below the low threshold, a lightpath is deactivated to release the underutilized network equipment. Reconfiguration algorithms use these thresholds to adjust the virtual topology to the constantly fluctuating IP traffic flows. While they save large amounts of energy in comparison to a static virtual topology scenario, they define the upper threshold arbitrary. This is not considered efficient, since setting a very low upper threshold as a precaution is a waste of lightpath capacity. Similarly, setting a high upper threshold arbitrary, may indeed lead to data loss if a sudden data burst arrives to the network. This work proposes a new method, Virtual Topology Reconfiguration with Dynamic Thresholds (DT-VTR), which adaptively calculates the upper threshold by taking into consideration the load variance of the IP traffic flows. The upper threshold is set up based on the worst case scenario excluding any chance of data loss due to burst arrivals, while keeping the upper threshold close to 100%. Furthermore, the adaptive approach of DT-VTR differentiates from previous studies by using an individual dynamic upper threshold for each lightpath, which alternates during the network operation along with the fluctuating traffic flows. As shown by the simulation results, DT-VTR manages to save from 6% up to 18% in comparison to traditional reconfiguration algorithms for various static upper thresholds.