Optimum Traffic Allocation in Bundled Energy-Efficient Ethernet Links

Abstract

The energy demands of Ethernet links have been an active focus of research in the recent years. This work has enabled a new generation of energy-efficient Ethernet (EEE) interfaces able to adapt their power consumption to the actual traffic demands, thus yielding significant energy savings. With the energy consumption of single network connections being a solved problem, in this paper, we focus on the energy demands of link aggregates that are commonly used to increase the capacity of a network connection. We build on known energy models of single EEE links to derive the energy demands of the whole aggregate as a function on how the traffic load is spread among its powered links. We then provide a practical method to share the load that minimizes overall energy consumption with controlled packet delay and prove that it is valid for a wide range of EEE links. Finally, we validate our method with both synthetic and real traffic traces captured in Internet backbones. Index Terms-Energy efficiency, link aggregation, network interfaces, optimization methods.1932-8184 © 2015 IEEE. Personal use is permitted, but republication/redistribution requires IEEE permission.See http://www.ieee.org/publications_standards/publications/rights/index.html for more information. Miguel Rodríguez-Pérez (M'09) received the M.Sc. and Ph.D. degrees in telecommunication engineering from the University of Vigo, Pontevedra, Spain, in 2001 and 2006, respectively. He is currently an Associate Professor with the Department of Telematics Engineering, University of Vigo, where he is also an affiliated member of the colocated Networking Laboratory. His research interests include congestion control and traffic engineering, with a strong focus on energy efficiency. Manuel Fernández-Veiga (SM'12) received the M.Sc. and Ph.D. degrees in telecommunication engineering from the University of Vigo, Pontevedra, Spain, in 1992 and 2001, respectively.He is currently an Associate Professor with the University of Vigo, where he is also an affiliated member of the colocated Networking Laboratory. His research interests include communication theory, performance analysis of computer networks, and wireless networking. He has authored over 50 papers in international conferences and journals.Sergio Herrería-Alonso received the M.Sc. and Ph.D. degrees in telecommunication engineering from the University of Vigo, Pontevedra, Spain, in 2001 and 2006, respectively. He is currently an Associate Professor with the Department of Telematics Engineering, University of Vigo, where he is also an affiliated member of the colocated Networking Laboratory. He has authored or coauthored over 30 papers in peer-reviewed international conferences and journals. His research interests include quality of service in the Internet and energy-efficient networking.

Matching SDN and Legacy Networking Hardware for Energy Efficiency and Bounded Delay

“…In contrast, we focus on flow allocation in a single-link aggregate between two switches (see [ 6 ], which is the theoretical basis of this paper), and our techniques work in much shorter timescales, in the order of a single frame transmission. It was found therein that the optimum minimum-energy allocation of flows into a bundle of EEE links turns out to follow a water filling policy for typical consumption profiles, as explained in [ 6 ]. That is, a new port will only be used to transmit a packet if the packet cannot be transmitted by any of the ports already being used, since they are operating at its full capacity.…”

“…This result holds for the main classes of mechanisms used to manage the power state of the IEEE 802.3az ports, i.e., frame transmission and burst transmission modes [ 24 ]. In addition, reference [ 6 ] presented an algorithm to achieve these results, which operates on a per-packet basis, deciding the port that will be used for each packet based on the occupation of the ports. Following a naive water filling algorithm and only diverting traffic to a new idle port when the previous ones are completely used at their full capacity will lead to an unbounded delay.…”

“…Then, is the normalized energy consumption of the whole bundle for a given load allocation. In [ 6 ], it was proven that, for any arbitrary algorithm governing the idle mode, is minimized iff: where X denotes the total traffic allocation and is the traffic allocation to the i -th port, i.e., . That is, the minimum energy consumption is obtained when a water filling algorithm is used to assign the traffic among the links in the bundle.…”

“…This is because the typical energy consumption profile of a single Ethernet link is a concave function of the traffic load (see Figure 1 ). In addition to the theoretical solution, a practical algorithm is also provided by [ 6 ], but assuming that the switches operate on a packet-by-packet basis. For two reasons, this algorithm cannot be directly implemented as an SDN application: The ideal algorithm considers that the switch individually decides for each packet which port will be used to forward it, based on the instantaneous occupation of the ports, a packet-level operation.…”

“…However, many of these new techniques remain unimplemented due to the lack of flexibility in current networks. For instance, some of the recent proposals in the literature require changes to basic protocols, whereas others require changes to the networking equipment [ 3 , 4 , 5 , 6 ].…”