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Networks & Infrastructure
Case Study
Searching for energy efficiency
Service providers need greater insight into where they can find efficiency in the network without impacting service delivery
by Bob Mandeville, Iometrix
With energy usage accounting for up to 50 percent of an operator’s operating expenses, energy costs on the rise, and IP technology delivering new bandwidth-intensive services to an ever-growing number of fixed and mobile subscribers, service providers need greater insight into where they can find efficiency in the network without impacting service delivery.
Everyone in networking agrees: Achieving energy efficiency is important. Such consensus may be a good starting point but where exactly does it take us? From an informal poll asking industry experts some very basic questions, the answer is unclear. Shouldn’t we all know how much energy consumption goes up when networks handle increasing traffic loads? Or when massive numbers of subscriber services are configured for delivery on a network service platform? Or, for that matter, when those elements perform the hard chore of bringing hundreds of circuits back to life after a network failure? Do state-of-the-art, very high speed corporate multipoint-to-multipoint services consume a lot more power than common residential broadband services?
So, if the expert poll couldn’t provide the answers, how about publicly available tests? The surprise here is that most test reports clearly state it is early days for power consumption measurement of networking elements and most then take the same tack of pushing frames at a device to see what happens.
In search of some guidelines to build up our knowledge base on power consumption, the best next step was to test networking devices with fully configured services and traffic loads to replicate conditions of use typical of an operational network. In parallel, we also analyzed the results with a view to contributing to the standards discussions revolving around energy efficiency.
The development of industry-wide agreements on a methodology for measuring and reporting energy consumption is being addressed with increased urgency as the need to define requirements for power consumption is starting to take precedence in several governing and advisory organizations. Governments are also taking steps to define limits to the amount of power that should be used to deliver broadband services to a residential subscriber. Such initiatives quickly give rise to some key questions: what are the metrics, and how do we measure?
To date, the only metrics we’ve had have been conventional measurements of watts per platform or port (i.e.watts per GigE). However, metrics that build linkages between service creation and energy consumption are inherently more useful to providers who monetize their businesses and plan their infrastructure investments by the number of subscribers serviced. If we can provide metrics more in line with the economics of their business in terms of the costs associated with delivering services, providers can better plan the return on investment around the traffic dimensioning and capacity planning to deliver those subscriber services. Since the IP edge and metro Ethernet platforms are responsible for aligning, shaping and monitoring subscriber traffic as well as the circuits that deliver that traffic, they are logical hot spots for service providers to target in their quest to reduce energy consumption.
The measurement and analysis of energy efficient designs recently performed by Iometrix on Ericsson service platforms aim to contribute to the current discussions the broader communications industry is having on ways of achieving greater environmental friendliness. The series of tests were conducted on Ericsson’s SM 480 Metro Ethernet and SmartEdge 1200 Multi-Service Edge routing platforms which deliver a variety of different services. The platforms were tested to measure power consumption on configurations capable of delivering high bandwidth services on an increasing scale to a very large number of customers.
Tests were performed for three different types of services: Ericsson’s SM 480 was configured to support carrier Ethernet E-Line point-to-point services transported over MPLS, and E-LAN multipoint-to-multipoint services transported over VPLS. The SmartEdge 1200 was configured to support PPPoE services. In the hands-on evaluation by Iometrix, the SmartEdge 1200 and SM 480 were placed under maximum loads measuring bi-directional traffic and stressing real-world data plane and control plane conditions.
Using Spirent’s Avalanche tester, as many as 256,000 subscriber sessions were activated on 64 Gigabit Ethernet access interfaces. Measured power consumption expressing the ratio of work performed to energy consumed is reported in milliwatts per active subscriber session to reflect the power consumption that a service provider will experience as large numbers of subscribers are added to the network.
Based on the functions performed by each platform, we believe the proposed metrics provide practical views into energy consumption on a granular level, by subscriber in the case of the IP edge, and by circuit in the case of the metro.
Figure 1.
The key findings of this series of tests performed on Ericsson’s SM 480 and SmartEdge 1200 are:
• Per subscriber power draw decreases sharply as the number of active subscribers is scaled upwards. When each system is configured to service as many as a quarter million subscribers, the measured per subscriber or per circuit power consumption was just over 5 milliwatts or 192 subscribers per watt.
• Power consumption increases only by a small amount when subscriber traffic is ramped up to high levels. These findings are similar for Carrier Ethernet over MPLS supported on the SM 480 and PPPoE services supported on the SmartEdge 1200.
Figure 2.
This series of lab tests provides strong evidence that energy efficient design can significantly impact the amount of energy required to support large numbers of subscribers in highly scaled networking environments delivering high bandwidth applications such as Triple Play.
The goal of energy efficient designs is to offer more services with less energy. The broad range of results posted in this series of tests show that networking platforms can significantly reduce per subscriber energy cost when they are scaled to service very large numbers of active subscribers under heavy loads. The industry-wide adoption of metrics to reliably measure energy efficiency in terms that take full account of the working conditions of this class of device will help pave the way for service providers to achieve greater energy cost savings and environmental friendliness.
Bob Mandeville is the founder of Iometrix.
About Iometrix
Iometrix is the networking industry's preeminent testing authority. Established in Silicon Valley in 2003, Iometrix is the successor to ENL (European Network Laboratories), the pioneering test lab Bob Mandeville founded in 1991 in Paris, France. Iometrix provides globally recognized and trusted certification tests as the officially endorsed test lab of the Metro Ethernet Forum, the MultiService Forum and the IP/MPLS Forum. Iometrix is strongly committed to advancing industry testing standards and has developed test specifications for protocols and services in several standards bodies including the IETF, IEEE, MEF, MultiService Forum and IP/MPLS Forum since 1993, developed and implemented procedures to execute testing for a broad range of networking equipment and also developed and implemented efficient test reporting processes. Iometrix has extensive experience with the management of testing projects and programs and has a team of highly specialized test engineers with strong experience in network performance and conformance testing.
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