Energy-aware virtual topology reconfiguration under dynamic traffic

In an IP over WDM network architecture, IP traffic is carried over a virtual topology (VT), composed of optical transparent channels called lightpaths. We propose an energy-efficient dynamic VT adaptation method with sleep mode, which allows changing only one lightpath connectivity at a time by dynamically monitoring the IP packet traffic load on each lightpath. In order to assure the connectivity of future traffic increase a high-load threshold is used. When the packet traffic load on a specific lightpath becomes higher than a threshold, a new lightpath is added to the virtual topology. However this congestion avoidance policy increases the power consumption by activating transponders in the network. Therefore at the same time lightly loaded lightpaths are eliminated in the virtual topology by using a low-load threshold. Energy-efficient virtual topology adaptation is achieved by traffic offloading considering both lightly loaded and heavily loaded links in the network. In this regard, high- and low-load threshold values need to be carefully determined in order to both gain power and ensure load balancing with keeping the stability of virtual connectivity at a reasonable level. We have analysed the power consumption of the network during 48-hours for different values of low- and high-load thresholds together with the impact of different threshold values on the stability of the virtual topology. We have shown that there is a trade-off between number of changes in the virtual topology and the energy-efficiency. Experimental results demonstrate that a good compromise can be achieved by adjusting the high- and low-load thresholds carefully.