Energy Efficient Routing by Switching-Off Network Interfaces

TL;DR

This paper addresses energy-efficient routing by switching off network interfaces to minimize active network elements, proposing models, heuristics, and analyzing impacts on topology and fault tolerance.

Contribution

It introduces a formal model and heuristic algorithms for energy-efficient routing that reduces active network interfaces, with analysis on various topologies and practical energy savings.

Findings

Approximate 33 MWh energy savings in medium-sized backbone networks.

More than one-third of network interfaces can be spared in most topologies.

The problem is proven to be hard to approximate within any constant factor.

Abstract

Several studies exhibit that the traffic load of the routers only has a small influence on their energy consumption. Hence, the power consumption in networks is strongly related to the number of active network elements, such as interfaces, line cards, base chassis,... The goal thus is to find a routing that minimizes the (weighted) number of active network elements used when routing. In this paper, we consider a simplified architecture where a connection between two routers is represented as a link joining two network interfaces. When a connection is not used, both network interfaces can be turned off. Therefore, in order to reduce power consumption, the goal is to find the routing that minimizes the number of used links while satisfying all the demands. We first define formally the problem and we model it as an integer linear program. Then, we prove that this problem is not in APX, that is there is no polynomial-time constant-factor approximation algorithm. We propose a heuristic algorithm for this problem and we also prove some negative results about basic greedy and probabilistic algorithms. Thus we present a study on specific topologies, such as trees, grids and complete graphs, that provide bounds and results useful for real topologies. We then exhibit the gain in terms of number of network interfaces (leading to a global reduction of approximately 33 MWh for a medium-sized backbone network) for a set of existing network topologies: we see that for almost all topologies more than one third of the network interfaces can be spared for usual ranges of operation. Finally, we discuss the impact of energy efficient routing on the stretch factor and on fault tolerance.