Mehrgan Mostowfi

IEEE 802.3az: the road to energy efficient ethernet

Ethernet is the dominant wireline communications technology for LANs with over 1 billion interfaces installed in the U.S. and over 3 billion worldwide. In 2006 the IEEE 802.3 Working Group started an effort to improve the energy efficiency of Ethernet. This effort became IEEE P802.3az Energy Efficient Ethernet (EEE) resulting in IEEE Std 802.3az-2010, which was approved September 30, 2010. EEE uses a Low Power Idle mode to reduce the energy consumption of a link when no packets are being sent. In this article, we describe the development of the EEE standard and how energy savings resulting from the adoption of EEE may exceed

Saving energy in LAN switches: New methods of packet coalescing for Energy Efficient Ethernet

400 million per year in the U.S. alone (and over

A Simulation Study of Energy-Efficient Ethernet With Two Modes of Low-Power Operation

1 billion worldwide). We also present results from a simulation-based performance evaluation showing how packet coalescing can be used to improve the energy efficiency of EEE. Our results show that packet coalescing can significantly improve energy efficiency while keeping absolute packet delays to tolerable bounds. We are aware that coalescing may cause packet loss in downstream buffers, especially when using TCP/IP. We explore the effects of coalescing on TCP/IP flows with an ns-2 simulation, note that coalescing is already used to reduce packet processing load on the system CPU, and suggest open questions for future work. This article will help clarify what can be expected when EEE is deployed.

Packet coalescing for dual-mode energy efficient ethernet: a simulation study

Small or home office (SOHO) Ethernet LAN switches consume about 8 TWh per year in the U.S. alone. Despite normally low traffic load and numerous periods of idleness, these switches typically stay fully powered-on at all times. With the standardization of Energy Efficient Ethernet (EEE), Ethernet interfaces can be put into a Low Power Idle (LPI) mode during idle periods when there are no packets to transmit. This paper proposes and evaluates a new EEE policy of synchronous coalescing of packets in network hosts and edge routers. This policy provides extended idle periods for all ports of a LAN switch and thus enables energy savings deeper than in the Ethernet PHY only. We evaluate our method using an ns-2 simulation model of a LAN switch. We show that our method can reduce the overall energy use of a LAN switch by about 40%, while introducing limited and controlled effects on typical Internet traffic and TCP.

Timed redirection: HTTP request coalescing to reduce energy use of hybrid web servers

Section 78.1.3 of the IEEE 802.3bj-2014 standard defines two modes of low-power idle (LPI) operation for the physical layers of energy-efficient ethernet (EEE) links that work at a speed of 40 Gb/s and higher: Fast Wake and Deep Sleep. In this letter, it is shown by simulation that combining two modes of low(er)-power operation in EEE links can result in significant savings with a reasonable performance tradeoff that may not be achievable with a single mode of LPI, as is the case for 10 Gb/s links and lower.

Major Dynamic Power Management methods in wired networks: A new taxonomy

Energy Efficient Ethernet (EEE) is a standard that introduces a Low Power Idle (LPI) mode to Ethernet links to reduce their power consumption between packet transmissions. An EEE link can transition to LPI when there are no packets in its buffer to transmit -- idle periods. Transition times to and from LPI are significantly high, which prevents EEE from taking full advantage of the links idle periods. Packet coalescing is to collect multiple packets before sending them on a link as a burst of back-to-back packets. By coalescing packets into bursts, the overhead of transition times can be reduced and nearly energy-proportional operation can be achieved. Only one LPI mode as described above is defined for Ethernet links with the capacity of 10 Gb/s and lower. However, two modes of low-power operation are defined for EEE links at 40 Gb/s and higher; Fast Wake and Deep Sleep. The Dual-Mode EEE can achieve significant savings that may not be achievable with a single LPI mode. In this paper, applying packet coalescing to Dual-Mode EEE is studied. Performance evaluation using simulation shows that packet coalescing can result is nearly energy-proportional operation in Dual-Mode EEE for 40 Gb/s and above, albeit with some modifications and trade-offs.

An energy-delay model for a packet coalescer

Network protocols can be designed to enable a reduction in energy use of data servers. We architect a new HTTP timed redirection response for a GET request to be redirected to another server with a given delay. This redirection response can be used in a hybrid web server to coalesce GET requests and allow a server to periodically sleep. In such a hybrid web server, a small low-power ARM-based Assistant receives all incoming HTTP requests and redirects them to a Pentium-class Master server with a delay calculated to allow the Master to sleep in alternating intervals. There is a growing class of applications that are delay tolerant at short time scales for file downloads. Experimental evaluation of timed redirection shows significant savings for the Master server with added delay for some requests which may be acceptable for certain applications.

Systems And Methods For Automatically Selecting A Communication Channel

Electricity consumption of Information and Communications Technology (ICT) reached a total of about 900 TWh per year in 2012 and electricity generation for ICT continues to contribute over 2% of the human-generated CO2 to the atmosphere. Energy costs are rapidly becoming the major operational expense for ICT and may soon dwarf capital expenses as software and hardware continue to drop in price. Energy consumption of wired networks as the dominant communications technology in enterprises and datacenters has been subject to significant research in the past years to reduce this cost and making networks more energy-efficient. This paper focuses on the major methods at the system-level to achieve this goal, and systematically reviews them in the context of a new taxonomy.