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Method to Optimize Energy Efficient Operation of High Speed Links

IP.com Disclosure Number: IPCOM000239171D
Publication Date: 2014-Oct-19
Document File: 5 page(s) / 76K

Publishing Venue

The IP.com Prior Art Database

Abstract

Disclosed is an extension of the negotiation process for energy efficient parameters for high-speed links. The disclosed process extends the current energy efficient parameter negotiation process to also support custom Physical Layer timing parameters applicable to energy efficient operation. Thus, interconnected systems have additional flexibility to maximize energy efficiency for a given link.

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Method to Optimize Energy Efficient Operation of High Speed Links

This disclosure is related to energy efficient operation of high-speed links, specifically those associated with Energy Efficient Ethernet (EEE) operation according to IEEE 802.3bj, and Fibre Channel Energy Efficient (FC-EE) operation according to the emerging FC-FS-4 standard. Both standards provide for low power operating periods (termed "Low Power Idle Mode" or "LPI Mode") during which the transmitter and receiver sides of the link may operate its circuitry at reduced power when no data frames are being transferred. To enable such low power operating periods, both standards include Transmitter and Receiver state diagrams, which control entry into and exit from the LPI Mode.

As illustrated in IEEE 802.3bj (and expected to be illustrated in the emerging FC-FS-4 standard), the systems attached to a given high-speed link may support one or more energy efficient operating states to reduce power consumption, or may choose to not support energy efficient operation. Those states include:


• Quiet (aka Deep Sleep): state in which the high speed link enters a quiescent
(i.e. non-signaling) state and supporting logic circuits at the transmitter and receiver sides of the link are powered off


• Fast Wake: state in which the high speed link remains in an active state transmitting Low Power Idle (LI) characters, allowing a subset of supporting logic circuits at the transmitter and receiver sides of the link to be powered off


• Idle: state in which the high speed link remains in an active state transmitting Idle
(I) characters, and supporting logic circuits at the transmitter and receiver sides of the link remain powered on (i.e. energy efficient operation is not permitted)

Considering the set of energy efficient operating states, parameter exchange and negotiation processes are employed by which the transmitter and receiver sides determine which operating state will be supported. Specifically considering the Quiet state, these processes involve exchanging system level Wake Time parameters pertaining to the transmit and receiver sides of the link. The transmit side Wake Time parameter (Transmit Tw) indicates the amount of time (in microseconds) the transmitting link partner will wait before it starts transmitting data after leaving LPI Mode. The receiver side Wake Time parameter (Receive Tw) indicates the amount of time (in microseconds) the receiving link partner is requesting the transmitting link partner to wait before resuming data transmission after leaving LPI Mode. In order to select Quiet state operation, the negotiation process must successfully resolve the Transmit Tw and Receive Tw parameter values pertaining to the systems interconnected by a given link such that Transmit Tw is equal to or greater than Receive Tw. As defined by the Fibre Channel and Ethernet standards, the Transmit Tw and

Receive Tw parameters represent system level Wake Time requirements. Howeve...