On the Energy Efficiency of IP-over-WDM Networks

In the next years, the Internet will undergo a substantial increase of the capacity required by end-users. Since Internet currently consumes a significant fraction of the world electrical power, reducing the energy consumption of telecom networks is expected to become more and more important. In this paper, we focus on backbone transport networks. We compare three different architectures for IP packet transport based on Wavelength Division Multiplexing (WDM) over optical fiber links (IP-over-WDM networks), namely IP with no Bypass (IP-NB), IP with Bypass (IP-B) and IP with Bypass and Grooming (IP-BG), which differ in their capability of traffic aggregation (grooming) and optical switching. IP-NB performs grooming in every network node, where the traffic is electronically processed and forwarded by the IP routers. IP-B enables switching of wavelength channels directly in the optical domain, thus bypassing the IP packet processing in intermediate IP routers. The IP-BG architecture represents an intermediate solution between the previous two: it provides both grooming capabilities (as IP-NB), in order to exploit network capacity efficiently, and optical switching (as IP-B) to reduce expensive electronic processing. We compare these three solutions, showing the trade-off between the reduction of the power consumption or of the network cost, and we analyze how minimizing one of these two factors can influence the other.