To switch on or off: A simple case study on energy efficiency in IP-over-WDM networks

In this paper, we present a simple case study on energy efficiency in IP-over-WDM networks with dynamic circuit capability and compare two different load adaptive schemes, referred to as switch-on and switch-off. While the switch-off technique was already proposed for energy conservation, the switch-on approach is a new paradigm which is based purely on one-time implementations of dynamic circuit capability. Our results show that both approaches can significantly reduce the power consumption and decrease the necessary totally installed capacity, but unlike the switch-off scheme, the switch-on scheme does not affect the path redundancy in the network. Furthermore, switch-on can reduce the number of routing reconfigurations required in the network. While this seems ideal, our results also show that the switch-on scheme uses a large number of small capacity interfaces which may not be suitable from a network planning perspective as it might require frequent capacity upgrades, which alone is an interesting avenue for future research.

I. Introduction

Internet based services play a substantial role in today's world economy and have been exhibiting significant growth rates with predictions that the global IP traffic will increase 4.3 times from 2009 to 2014, reaching 63.9 exabytes per month in 2014 [1]. This trend is mainly driven by the ongoing increase of all forms of consumer video (IPTV, VoD, P2P, YouTube, etc.) coupled with increasing total number of Internet users worldwide. This unprecedented increase in capacity has not only driven up demand for bandwidth from the Internet infrastructure but has also presented providers with new challenges, especially in the energy consumed by the Internet infrastructure. Although the ongoing technological progress of network equipment reduces the consumed energy per transmitted bit by around 13% per year [2], this will likely not be sufficient in itself since there remains at least a 20% gap compared to the traffic growth. Without new and efficient energy conservation approaches, the energy consumption is likely to become the Internet's main bottleneck. This is especially critical in today's Internet backbone, which is typically over-provisioned and thereby lightly loaded at most times [3].