Ethernet Adaptive Link Rate: System Design and Performance Evaluation

Abstract

The Internet and the devices that connect to it consume a growing and significant amount of electricity.The utilization of desktop-to-switch Ethernet links is generally very low and thus there is a potential for energy savings by using an Adaptive Link Rate (ALR) protocol that matches link rate to utilization. In this paper, we design and evaluate a new ALR policy suitable for both bursty and smooth traffic. The policy uses output buffer thresholds and fine-grain utilization monitoring to determine when to switch link data rate. We develop a new traffic model for generating synthetic 1 and 10 Gb/s bursty traffic traces. Using this traffic model and simulation, we show that the new ALR policy is suitable for smooth traffic and also does not degrade performance for bursty traffic. Performance is measured in packet delay versus time in low (and energy saving) data rate.

Real-time performance analysis of Adaptive Link Rate

“…Furthermore, we acknowledge that our measured switching times are much longer than 1 ms, which is assumed in previous research [8] [9][10], but our switching time between 1 Gbps and 100 Mbps is well within the time projected by [3] [20]. Unfortunately, this lengthy time is due to limitations of the current PHY technology and IEEE standards.…”

“…To solve the problem of link oscillation and avoid the resulting increase in mean packet delay, Gunaratne et al [9] proposed a link utilization based threshold policy. The utilization threshold policy monitors link utilization by counting bytes transmitted during a defined time interval.…”

“…To simulate network traffic, we use a Poisson process to model the arrival of packets of a constant maximum packet length of 1518 bytes, which reflects that used in previous work [9][10]. To represent different network traffics ranging from light to heavy, we vary the average link utilization of input traces from 1% to 15%.…”

“…During these periods, energy is wasted by operating the network interfaces and links at the highest rates available. Devices may adaptively shut down and/or vary link rates in response to link utilization to reduce power consumption [1] [4] [9]. The ability to vary the link rate is a technique known as adaptive link rate (ALR) [9].…”

Review of Facts, Data and Proposals for a Greener Internet

“…Another power management approach that has been intensively investigated is Adaptive Link Rate (ALR), which is the ability to modify the link rate to reduce power consumption [36], [37], [43]- [46]. The technique exploits the characteristics of the network traffic in which packets are transmitted in bursts, with variable length periods of idleness or reduced link utilization between bursts.…”