Patent Publication Number: US-2010115306-A1

Title: Method and system for control of energy efficiency and associated policies in a physical layer device

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS/INCORPORATION BY REFERENCE 
     This patent application makes reference to, claims priority to and claims benefit from U.S. Provisional Patent Application Ser. No. 61/111,653, filed on Nov. 5, 2008. 
     This application also make reference to:
     U.S. patent application Ser. No. ______ (Attorney Docket No. 20368US02) filed on even date herewith; and   U.S. patent application Ser. No. ______ (Attorney Docket No. 20755US02) filed on even date herewith.   

     Each of the above stated applications is hereby incorporated herein by reference in its entirety. 
    
    
     FIELD OF THE INVENTION 
     Certain embodiments of the invention relate to networking. More specifically, certain embodiments of the invention relate to a method and system for control of energy efficiency and associated policies in a physical layer device. 
     BACKGROUND OF THE INVENTION 
     Communications networks and in particular Ethernet networks, are becoming an increasingly popular means of exchanging data of various types and sizes for a variety of applications. In this regard, Ethernet networks are increasingly being utilized to carry voice, data, and multimedia traffic. Accordingly more and more devices are being equipped to interface to Ethernet networks. Broadband connectivity including internet, cable, phone and VOIP offered by service providers has led to increased traffic and more recently, migration to Ethernet networking. Much of the demand for Ethernet connectivity is driven by a shift to electronic lifestyles involving desktop computers, laptop computers, and various handheld devices such as smart phones and PDA&#39;s. As an increasing number of portable and/or handheld devices are enabled for Ethernet communications, battery life may be a concern when communicating over Ethernet networks. Accordingly, ways of reducing power consumption when communicating over electronic networks may be needed. Furthermore, ways of improving energy efficiency while maintaining compatibility with existing infrastructure and minimizing the redesign of network components are desirable. 
     Further limitations and disadvantages of conventional and traditional approaches will become apparent to one of skill in the art, through comparison of such systems with some aspects of the present invention as set forth in the remainder of the present application with reference to the drawings. 
     BRIEF SUMMARY OF THE INVENTION 
     A system and/or method is provided for control of energy efficiency and associated policies in a physical layer device, substantially as shown in and/or described in connection with at least one of the figures, as set forth more completely in the claims. 
     These and other advantages, aspects and novel features of the present invention, as well as details of an illustrated embodiment thereof, will be more fully understood from the following description and drawings. 
    
    
     
       BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWINGS 
         FIG. 1  is a block diagram illustrating an exemplary Ethernet connection between two network devices, in accordance with an embodiment of the invention. 
         FIG. 2  is a block diagram illustrating an exemplary Ethernet over twisted pair PHY device architecture comprising a multi-rate capable physical block, in accordance with an embodiment of the invention. 
         FIG. 3A  is a block diagram illustrating an exemplary PHY device operable to implement a control policy for energy efficient networking, in accordance with an embodiment of the invention. 
         FIG. 3B  is a diagram illustrating multiple PHY devices integrated on chip, wherein each PHY device is operable to implement an EEN control policy, in accordance with an embodiment of the invention. 
         FIG. 3C  is a diagram illustrating multiple PHY devices integrated on chip managed and managed by a plurality of EEN control policies, in accordance with an embodiment of the invention. 
         FIG. 4  is a flow chart illustrating implementation of an EEN control policy in a PHY, in accordance with an embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Certain embodiments of the invention may be found in a method and system for control of energy efficiency and associated policies in a physical layer device. In various embodiments of the invention, operation of a PHY device may be controlled based on one or more energy efficient networking (EEN) control policies executed from within the PHY device. The one or more control policies may enable managing power consumption associated with communication of data via the PHY device. A mode of operation of the PHY device may be selected based on the control policy. One or more components of the PHY device may be reconfigured based on the selected mode of operation. A first portion of the reconfiguration may be performed prior to sending an EEN control signal and a remaining portion of the reconfiguration may be performed after sending the EEN control signal. Memory within the PHY may be allocated to buffering received and/or to-be-transmitted data based on the selected mode of operation, based on an amount of time required for the reconfiguration, and/or based on an amount of time required for reconfiguration of a link partner communicatively coupled to the PHY device. Conversely, memory within the PHY may be de-allocated from buffering received and/or to-be-transmitted data based on the selected mode of operation, based on an amount of time required for the reconfiguration, and/or based on an amount of time required for reconfiguration of a link partner communicatively coupled to the PHY device. De-allocating memory from buffering may free the memory up to support other functions such as encryption and/or decryption. The reconfiguration may be triggered at a time determined by the control policy. The selected mode of operation may comprise an LPI mode of operation or a subset PHY mode of operation. The control policy may be executed within the PHY device utilizing hardware, software, and/or firmware within the PHY device. Multiple PHY devices may be integrated on a common substrate, and one of the PHY devices may control operation and/or configuration of one or more of the other PHY devices. 
       FIG. 1  is a block diagram illustrating an exemplary Ethernet connection between a two network devices, in accordance with an embodiment of the invention. Referring to  FIG. 1 , there is shown a system  100  that comprises a network device  102  and a network device  104 . The network devices  102  and  104  may be link partners that communicate via the link  112  and may comprise, respectively, hosts  106   a  and  106   b , networking subsystems  108   a  and  108   b , PHY devices  110   a  and  110   b , interfaces  114   a  and  114   b , interfaces  116   a  and  116   b , and interfaces  118   a  and  118   b . The interfaces  114   a  and  114   b  are referenced collectively or separately herein as interface(s)  114 , and the interfaces  116   a  and  116   b  are referenced collectively or separately herein as interface(s)  116 . The hosts  106   a  and  106   b  are referenced collectively or separately herein as host(s)  106 . The networking subsystems  108   a  and  108   b  are referenced collectively or separately herein as networking subsystem(s)  108 . The PHY devices  110   a  and  110   b  are referenced collectively or separately herein as PHY device(s)  106 . 
     The link  112  is not limited to any specific medium. Exemplary link  112  media may comprise copper, wireless, optical and/or backplane technologies. For example, a copper medium such as STP, Cat3, Cat 5, Cat 5e, Cat 6, Cat 7 and/or Cat 7a as well as ISO nomenclature variants may be utilized. Additionally, copper media technologies such as InfiniBand, Ribbon, and backplane may be utilized. With regard to optical media for the link  112 , single mode fiber as well as multi-mode fiber may be utilized. With regard to wireless, the network devices  102  and  104  may support one or more of the 802.11 family of protocols. In an exemplary embodiment of the invention, the link  112  may comprise up to four or more physical channels, each of which may, for example, comprise an unshielded twisted pair (UTP). The network device  102  and the network device  104  may communicate via two or more physical channels comprising the link  112 . For example, Ethernet over twisted pair standards 10 BASE-T and 100 BASE-TX may utilize two pairs of UTP while Ethernet over twisted pair standards 1000 BASE-T and 10 GBASE-T may utilize four pairs of UTP. 
     The network devices  102  and/or  104  may comprise, for example, switches, routers, end points, routers, computer systems, audio/video (A/V) enabled equipment, or a combination thereof. In this regard, A/V equipment may, for example, comprise a microphone, an instrument, a sound board, a sound card, a video camera, a media player, a graphics card, or other audio and/or video device. Additionally, the network devices  102  and  104  may be enabled to utilize Audio/Video Bridging and/or Audio/video bridging extensions (collectively referred to herein as audio video bridging or AVB) for the exchange of multimedia content and associated control and/or auxiliary data. Also, the network devices may be operable to implement security protocols such IPsec and/or MACSec. 
     The hosts  106   a  and  106   b  may be operable to handle functionality of OSI layer 3 and above in the network devices  102  and  104 , respectively. The hosts  106   a  and  106   b  may be operable to perform system control and management, and may comprise hardware, software, or a combination thereof. The hosts  106   a  and  106   b  may communicate with the networking subsystems  108   a  and  108   b  via interfaces  116   a  and  116   b , respectively. The hosts  106   a  and  106   b  may additionally exchange signals with the PHY devices  110   a  and  110   b  via interfaces  118   a  and  118   b , respectively. The interfaces  116   a  and  116   b  may correspond to PCI or PCI-X interfaces. The interfaces  118   a  and  118   b  may comprise one or more discrete signals and/or communication busses. Notwithstanding, the invention is not limited in this regard. 
     The networking subsystems  108   a  and  108   b  may comprise suitable logic, circuitry, and/or code that may be operable to handle functionality of OSI layer 2 and above layers in the network device  102  and  104 , respectively. In this regard, networking subsystems  108  may each comprise a media access controller (MAC) and/or other networking subsystems. Each networking subsystem  108  may be operable to implement, switching, routing, and/or network interface card (NIC) functions. Each networking subsystems  108   a  and  108   b  may be operable to implement Ethernet protocols, such as those based on the IEEE 802.3 standard, for example. Notwithstanding, the invention is not limited in this regard. The networking subsystems  108   a  and  108   b  may communicate with the PHY devices  110   a  and  110   b  via interfaces  114   a  and  114   b , respectively. The interfaces  114   a  and  114   b  may correspond to Ethernet interfaces that comprise protocol and/or link management control signals. The interfaces  114   a  and  114   b  may be, for example, multi-rate capable interfaces and/or media independent interfaces (MII). 
     The PHY devices  110  may each comprise suitable logic, circuitry, interfaces, and/or code that may enable communication between the network device  102  and the network device  104 . Each of the PHY devices  110  may be referred to as a physical layer transmitter and/or receiver, a physical layer transceiver, a PHY transceiver, a PHYceiver, or simply a PHY. The PHY devices  110   a  and  110   b  may be operable to handle physical layer requirements, which include, but are not limited to, packetization, data transfer and serialization/deserialization (SERDES), in instances where such an operation is required. Data packets received by the PHY devices  110   a  and  110   b  from networking subsystems  108   a  and  108   b , respectively, may include data and header information for each of the above six functional OSI layers. The PHY devices  110   a  and  110   b  may be configured to convert packets from the networking subsystems  108   a  and  108   b  into physical layer signals for transmission over the physical link  112 . In some embodiments of the invention, the PHY devices  110  may comprise suitable logic, circuitry, and/or code operable to implement MACSec. 
     The PHY devices  110  may each support, for example, Ethernet over copper, Ethernet over fiber, and/or backplane Ethernet operations. The PHY devices  110  may each enable multi-rate communications, such as 10 Mbps, 100 Mbps, 1000 Mbps (or 1 Gbps), 2.5 Gbps, 4 Gbps, 10 Gbps, or 40 Gbps, for example. In this regard, each of the PHY devices  110  may support standard-based data rate limits and/or non-standard data rate limits. Moreover, the PHY devices  110  may each support standard Ethernet link lengths or ranges of operation and/or extended ranges of operation. Each of the PHY devices  110  may enable communication between the network device  102  and the network device  104  by utilizing a link discovery signaling (LDS) operation that enables detection of active operations in the other network device. In this regard the LDS operation may be configured for supporting a standard Ethernet operation and/or an extended range Ethernet operation. Each of the PHY devices  110  may also support autonegotiation for identifying and selecting communication parameters such as speed and duplex mode. 
     One or both of the PHY devices  110   a  and  110   b  may comprise a twisted pair PHY capable of operating at one or more standard rates such as 10 Mbps, 100 Mbps, 1 Gbps, and 10 Gbps (10 BASE-T, 100 GBASE-TX, 1 GBASE-T, and/or 10 GBASE-T); potentially standardized rates such as 40 Gbps and 100 Gbps; and/or non-standard rates such as 2.5 Gbps and 5 Gbps. 
     One or both of the PHY devices  110   a  and  110   b  may comprise a backplane PHY capable of operating at one or more standard rates such as 10 Gbps (10 GBASE-KX4 and/or 10 GBASE-KR); and/or non-standard rates such as 2.5 Gbps and 5 Gbps. 
     One or both of the PHY devices  110   a  and  110   b  may comprise an optical PHY capable of operating at one or more standard rates such as 10 Mbps, 100 Mbps, 1 Gbps, and 10 Gbps; potentially standardized rates such as 40 Gbps and 100 Gbps; and/or non-standardized rates such as 2.5 Gbps and 5 Gbps. In this regard, the optical PHY may be a passive optical network (PON) PHY. 
     One or both of the PHY devices  110   a  and  110   b  may support multi-lane topologies such as 40 Gbps CR4, ER4, KR4; 100 Gbps CR10, SR10 and/or 10 Gbps LX4 and CX4. Also, serial electrical and copper single channel technologies such as KX, KR, SR, LR, LRM, SX, LX, CX, BX10, LX10 may be supported. Non standard speeds and non-standard technologies, for example, single channel, two channel or four channels may also be supported. More over, TDM technologies such as PON at various speeds may be supported by the network devices  102  and/or  104 . 
     One or both of the PHY devices  110   a  and  110   b  may support transmission and/or reception at a high(er) data in one direction and transmission and/or reception at a low(er) data rate in the other direction. For example, the network device  102  may comprise a multimedia server and the network device  104  may comprise a multimedia client. In this regard, the network device  102  may transmit multimedia data, for example, to the network device  104  at high(er) data rates while the network device  104  may transmit control or auxiliary data associated with the multimedia content at low(er) data rates. 
     In various embodiments of the invention, each of the PHY devices  110   a  and  110   b  may be operable to implement one or more energy efficient techniques, which may be referred to as energy efficient networking (EEN) on in the specific case of Ethernet, energy efficient Ethernet (EEE). For example, the PHY devices  110   a  and  110   b  may be operable to support low power idle (LPI) and/or sub-rating, also referred to as subset PHY, techniques. LPI may generally refer a family of techniques where, instead of transmitting conventional IDLE symbols during periods of inactivity, the PHY devices  110   a  and  110   b  may remain silent and/or communicate signals other than conventional IDLE symbols. Sub-rating, or sub-set PHY, may generally refer to a family of techniques where the PHYs are reconfigurable, in real-time or near real-time, to communicate at different data rates. 
     In operation, the PHY devices  110   a  and  110   b  may be operable to support one or more EEN techniques, comprising for example, LPI, and sub-rate or subset PHY. Accordingly, an EEN control policy may be implemented in firmware, hardware, and/or software within the PHY devices  110   a  and  110   b.  An EEN control policy may implement functions defined by, related to, or in place of protocols defined by IEEE 802.3az. The EEN control policy may determine how and/or when to configure and/or reconfigure the PHY devices  110   a  and  110   b  to optimize the tradeoff between energy efficiency and performance. For LPI, the control policy may be utilized to determine, for example, what variant of LPI to utilize, when to go into a LPI mode and when to come out of a LPI mode. For subset PHY, the PHY devices  110   a  and  110   b  may be operable to determine, for example, how to achieve a desired data rate and when to transition between data rates. Although aspects of the invention are described with regard to LPI and subset PHY, the invention is not so limited and other EEN techniques may be implemented via a PHY based control policy. 
     The EEN control policy may be implemented at the physical layer and may be transparent to OSI Layer 2 and the OSI layers above. In this regard, in some embodiments of the invention, a control policy for implementing EEN protocols, such as protocols defined by IEEE 802.3az, may be implemented entirely in the physical layer. In other embodiments of the invention, the control may be partially implemented in the physical layer and partially implemented in OSI layer 2 and higher OSI layers. A PHY device that implements such an EEN control policy may thus be a drop-in replacement for a conventional PHY device. The EEN control policy implemented by the PHY device, may be compatible with a legacy MAC and/or legacy host. In this manner, implementing an EEN control policy in a PHY device  110  may enable reaping the benefits of a more energy efficient network while avoiding the need to redesign or “re-spin” all, or a portion of, a networking subsystem  108  and/or a host  106 . Additionally, by implementing the EEN control policy at the physical layer hardware and/or software resources on a host  106  and/or networking system  108 , that would otherwise be required for implementing the EEN policy, may be allocated for other functions. 
       FIG. 2  is a block diagram illustrating an exemplary Ethernet over twisted pair PHY device architecture comprising a multi-rate capable physical block, in accordance with an embodiment of the invention. Referring to  FIG. 2 , there is shown a network device  200  which may comprises an Ethernet over twisted pair PHY device  202  and the interface  114 . The PHY device  202  may be an integrated device which may comprise a multi-rate capable physical layer module  212 , one or more transmitters  214 , one or more receivers  220 , a memory  216 , and one or more input/output interfaces  222 . 
     The PHY device  202  may be an integrated device that comprises a multi-rate capable physical layer module  212 , one or more transmitters  214 , one or more receivers  220 , a memory  216 , a memory interface  218 , and one or more input/output interfaces  222 . The PHY device  202  may be the same as or substantially similar to the PHY devices  110   a  and  110   b  described with respect to  FIG. 1 . In this regard, the PHY device  202  may provide layer  1  (physical layer) operability and/or functionality that enables communication with a remote PHY device. 
     The interface  114  may be the same as or substantially similar to the interfaces  114   a  and  114   b  described with respect to  FIG. 1 . The interface  114  may comprise, for example, a media independent interface such as XGMII, GMII, or RGMII for communicating data to and from the PHY  202 . In this regard, the interface  114  may comprise a signal to indicate that data from the network subsystem  108  to the PHY  110  is imminent on the interface  114 . Such a signal is referred to herein as a transmit enable (TX_EN) signal. Similarly, the interface  114  may comprise a signal to indicate that data from the PHY  110  to the network subsystem  108  is imminent on the interface  114 . Such a signal is referred to herein as a receive data valid (RX_DV) signal. The interface  114  may also comprise a control interface such as a management data input/output (MDIO) interface. 
     The multi-rate capable physical layer module  212  in the PHY device  202  may comprise suitable logic, circuitry, and/or code that may enable operability and/or functionality of physical layer requirements. In this regard, the multi-rate capable physical layer module  212  may enable generating the appropriate link discovery signaling utilized for establishing communication with a remote PHY device in a remote network device. The multi-rate capable physical layer module  212  may communicate with a MAC controller, and/or other OSI layer 2 and higher subsystems, via the interface  114 . In one aspect of the invention, the interface  114  may be a media independent interface (MII) and may be configured to utilize a plurality of serial data lanes for receiving data from the multi-rate capable physical layer module  212  and/or for transmitting data to the multi-rate capable physical layer module  212 . The multi-rate capable physical layer module  212  may be configured to operate in one or more of a plurality of communication modes, where each communication mode may implement a different communication protocol. These communication modes may include, but are not limited to, Ethernet over twisted pair standards 10 BASE-T, 100 BASE-TX, 1000 BASE-T, 10 GBASE-T, and other similar protocols that utilize multiple physical channels between network devices. The multi-rate capable physical layer module  212  may be configured to operate in a particular mode of operation upon initialization or during operation. In this regard, the PHY device  202  may operate in a normal mode or in one of a plurality of an energy saving modes. Exemplary energy saving modes may comprise a low power idle (LPI) mode and one or more sub-rate modes where the PHY device  202  may communicate at less than a maximum supported or initially negotiated data rate. 
     In various embodiments of the invention, the multi-rate capable physical layer module  212  may comprise suitable logic, circuitry, interfaces, and/or code for implementing an energy efficient networking (EEN) control policy. Accordingly, the multi-rate capable physical layer module  212  may be operable to monitor one or more conditions and/or signals in the PHY device  202  and control mode of operation based on the monitoring. In this regard, the multi-rate capable physical layer module  212  may generate one or more control signals to configure and reconfigure the various components of the PHY device  202 . 
     The multi-rate capable physical layer module  212  may comprise memory  216   a  and/or may be coupled to memory  216   b  through a memory interface  218 . The memories  216   a  and  216   b , referred collectively herein as memory  216 , may comprise suitable logic, circuitry, and/or code that may enable storage or programming of information that includes parameters and/or code that may effectuate the operation of the multi-rate capable physical layer module  212 . In this regard, the memory  216  may, for example, comprise one or more registers which may be accessed and/or controlled via a MDIO portion of the interface  114 . Additionally, the memory  216  may buffer data received via the interface  114  prior to converting the data to physical symbols and transmitting it via one or more of the interfaces  222 . For example, data from the interface  114  may be buffered while the PHY transitions from an energy saving mode to a higher performance mode—transitioning out of LPI mode or from a sub-rate to a higher data rate, for example. Also, the memory  216  may buffer data received via one or more of the interfaces  222  prior to packetizing or otherwise processing it and conveying it via the interface  114 . For example, data received via the link  112  may be buffered in the memory  216  while higher layer functions and/or circuitry, such as a MAC or PCI bus, come out of an energy saving mode. 
     Each of the transmitters  214   a ,  214   b ,  214   c ,  214   d , collectively referred to herein as transmitters  214 , may comprise suitable logic, circuitry, interfaces, and/or code that may enable transmission of data from the network device  200  to a remote network device via, for example, the link  112  in  FIG. 1 . The receivers  220   a,    220   b ,  220   c,    220   d  may comprise suitable logic, circuitry, and/or code that may enable receiving data from a remote network device. Each of the transmitters  214   a ,  214   b ,  214   c ,  214   d  and receivers  220   a,    220   b ,  220   c,    220   d  in the PHY device  202  may correspond to a physical channel that may comprise the link  112 . In this manner, a transmitter/receiver pair may interface with each of the physical channels  224   a ,  224   b ,  224   c ,  224   d.  In this regard, the transmitter/receiver pairs may be enabled to support various communication rates, modulation schemes, and signal levels for each physical channel. In this manner, the transmitters  214  and/or receivers  229  may support various modes of operation that enable managing energy consumption of the PHY device  202  and energy consumption on the link  112 . Accordingly, one or more of the transmitters  214  and/or receivers  220  may be powered down and/or otherwise configured based on a mode of operation of the PHY device  202 . 
     The input/output interfaces  222  may comprise suitable logic, circuitry, and/or code that may enable the PHY device  202  to impress signal information onto a physical channel, for example a twisted pair of the link  112  disclosed in  FIG. 1 . Consequently, the input/output interfaces  222  may, for example, provide conversion between differential and single-ended, balanced and unbalanced, signaling methods. In this regard, the conversion may depend on the signaling method utilized by the transmitter  214 , the receiver  220 , and the type of medium of the physical channel. Accordingly, the input/output interfaces  222  may comprise one or more baluns and/or transformers and may, for example, enable transmission over a twisted pair. Additionally, the input/output interfaces  222  may be internal or external to the PHY device  202 . In this regard, if the PHY device  202  comprises an integrated circuit, then “internal” may, for example, refer to being “on-chip” and/or sharing the same substrate. Similarly, if the PHY device  202  comprises one or more discrete components, then “internal” may, for example, refer to being on the same printed circuit board or being within a common physical package. 
     Each hybrid  226  may comprise suitable logic, circuitry, interfaces, and/or code that may enable separating transmitted and received signals from a physical link. For example, the hybrids may comprise echo cancellers, far-end crosstalk (FEXT) cancellers, and/or near-end crosstalk (NEXT) cancellers. Each hybrid  226  in the network device  300  may be communicatively coupled to an input/output interface  222 . One of more of the hybrids  226  may be enabled to support various modes of operation that enable managing energy consumption of the PHY device  202  and energy consumption on the link  112 . Accordingly, portions of the hybrids  226  may be powered down and/or otherwise configured based on a mode of operation of the PHY device  202 . 
     In operation, the network device  200  may communicate with a remote partner via the link  112 . To optimize the tradeoff between performance and energy consumption, the PHY device  202  may implement a control policy, which may be utilized to determine when to transition between various modes of operation. In this regard, performance may be measured by a variety of metrics such as jitter, latency, bandwidth, and error rates. 
     In one exemplary embodiment of the invention, the control policy may determine when and how to utilize sub-rating to improve energy efficiency. Accordingly, the control policy may be utilized to determine what data rate to utilize, how to configure the various components of the PHY device  202  to realize a selected data rate, and when to transition between data rates. In this regard, the PHY device  202  may be operable to generate one or more control signals, based on the control policy, to configure or reconfigure the transmitters  214 , receivers  220 , hybrids  226 , the memory  216 , and/or one or more portions of the multi-rate capable PHY module  212 . The PHY device  202  may also be operable to, based on the control policy, generate signals for communicating EEN states and/or decisions to a link partner. 
     In another exemplary embodiment of the invention, the control policy may make determinations as to when and how to utilize low power idle (LPI) to improve energy efficiency. Accordingly, the control policy may be utilized to determine when to go into an LPI mode, how to configure the various components of the PHY device  202  when in LPI mode, and when to come out of a LPI mode. The PHY device  202  may also be operable to, based on the control policy, generate signals for communicating EEN states and/or decisions to a link partner. 
       FIG. 3A  is a block diagram illustrating an exemplary PHY operable to implement a control policy for energy efficient networking, in accordance with an embodiment of the invention. Referring to  FIG. 3A , there is shown OSI layers above the MAC represented generically as block  306 , a MAC client  304   a , a MAC  304   b  and a PHY device  302 . The PHY device  302  may comprise a module  308  for implementing the physical coding sublayer (PCS), the physical media attachment (PMA) sublayer and/or the physical media dependent (PMD) sublayer; and an EEN module  314 . The module  308  may comprise one or more transmit buffers  310   a,  one or more receive buffers  310   b.    
     The block  308  may be substantially similar to the hosts  106  described with respect to  FIG. 1 . The combination of the MAC client  304   a  and the MAC  304   b  may perform functions substantially similar to a network subsystem  108  described with respect to  FIG. 1 . The MAC client  304   a  may, for example, implement multiplexing and flow control to enable multiple network layer protocols to coexist and utilize the MAC  304   b  and the PHY  302 . The MAC client  304   a  may be, for example, the logical link control (LLC) sub-layer defined in IEEE 802.2. The MAC  304   b  may perform data encapsulation and/or media access management, where media access management may comprise operations that handle conflicts arising from multiple network devices sharing a common physical medium. An exemplary operation may comprise arbitration and negotiation. 
     The PHY device  302  may comprise suitable logic, circuitry, interfaces and/or code that may be operable to implement physical layer functionality. In this regard, the physical coding sublayer (PCS), physical medium attachment (PMA) sublayer, and physical medium dependent (PMD) sublayer may be implemented via hardware, firmware, and/or software represented as module  308 . The module  308  may be operable to perform one or more of physical encoding and/or decoding, PMA framing, and transmitter and/or receiver operations. The module  308  may comprise one or more transmit buffers  310   a  that may be operable to store data received via the interface  114  and destined for transmission on the link  112 . The module  308  may comprise one or more receive buffers  310   b  that may be operable to store data received via the link  112  and destined for the MAC  304   b.    
     The PHY device  302  may also comprise an EEN module  314  which may, in turn, comprise suitable logic, circuitry, and/or code that may be operable to implement an EEN control policy. The (EEN) control policy may be operable to balance the tradeoff between performance and power consumption in the PHY  302  and/or on the link  112 . In various exemplary embodiments of the invention, the PHY device  302  may comprise memory  316  and/or one or more counters  318 . In addition, the module  314  may be operable to generate EEN control information to be communicated to a link partner and/or process EEN control information received from a link partner. 
     The memory  316  may comprise one or more state registers and/or configuration registers for implementing the EEN control policy. The state registers may be read and/or written via, for example, a MDIO bus to the MAC  304   a  and/or one or more signals from the higher OSI layers  306 . Additionally, the memory  316  may be allocated, de-allocated, and reallocated to supplement the Tx buffer  310   a  and/or the Rx buffer  310   b.    
     In operation, the EEN control policy may make decisions such as when to enter and/or exit a low(er) power mode. EEN control policy decisions and the resulting actions, such as reconfiguring the PHY  302 , may be determined based on one or more signals and/or conditions monitored in the PHY  302 . Several examples of factors which may be considered by the control policy follow. Many of the examples are simplified and various embodiments of the invention may utilize a combination of two or more of them. Nevertheless, the invention is not limited to the examples provided. 
     Implementation of the EEN protocols and/or techniques may be based, for example, on an amount of data buffered in the buffers  310  and/or the memory  316 . For example, in instances that the Tx buffer  310   a  is empty, or is empty for a certain amount of time, portions of the PHY  302  associated with data transmission may be reconfigured into a low(er) power state. Similarly, in instances that the Rx buffer  310   b  is empty, or is empty for a certain amount of time, portions of the PHY  302  associated with data reception may be reconfigured into a low(er) power state. In some embodiments of the invention, configuration of transmit portions of the PHY  302  may be determined based on a configuration of receive portions of the PHY  302 , and visa versa—configuration of receive portions of the PHY  302  may be determined based on a configuration of receive portions of the PHY  302 . Strapping configuration of the transmit portion to configuration of the receive portion in this manner may be based on the assumption that no traffic received from a link partner may correlate to no traffic being sent to the link partner. Such an assumption may be useful, for example, in core devices such as switches or routers that have limited ability to predict traffic on the link. 
     Implementation of the EEN protocols and/or techniques, such as determining when to transition between modes of operation, may be based, for example, on one or more counters and/or registers in the block  314 . For example, in instances that the TX_EN of the interface  114  has not been asserted for a statically or dynamically determined period of time, portions of the PHY  302  associated with data transmission may be reconfigured into a low(er) power state. Similarly, in instances that data has not been received via the link  112 , and/or that the link has been in IDLE, for a statically or dynamically determined period of time, portions of the PHY  302  associated with data reception may be reconfigured into a low(er) power state. Additionally, values of the counter may be stored and historical values of the counter may be utilized to predict when the PHY  302  may transition to a low(er) power mode without having a significant negative impact on performance. 
     Implementation of the EEN protocols and/or techniques, such as determining when to transition between modes of operation, may be based, for example, on management signals of an MDIO bus to the MAC  304   b.  For example, the MDIO may configure thresholds such as how long the PHY  302  should stay in a low(er) power mode after entering the low(er) power mode, how long a buffer should be empty before going into a low(er) power mode, and how full a buffer should be before waking up from a low(er) power mode. The MDIO may also be utilized to configure parameters pertaining to a link partner. Exemplary parameters comprise how long the link partner takes to wake up and how much buffering is available in the link partner&#39;s buffers. The MDIO may enable configuration of the control policy by a system designer or administrator. 
     Implementation of the EEN protocols and/or techniques, such as determining when to transition between modes of operation, may be based, for example, on signals from the block  306 , such as signals generated by a PCI bus controller and/or a CPU. For example, a signal indicating whether the PCI bus is active may be utilized to predict whether data will be arriving at the PHY  302  and/or to determine whether the higher OSI layers  306  are ready to receive data from the PHY  302 . For another example, signals from a CPU, or other data processing components in the block  306 , may indicate a type of traffic communicated to the PHY  302  and the control policy may determine an appropriate mode of operation of the PHY  302  and/or an appropriate allocation of buffering, or other resources, in the PHY  302  based on the data type. In this regard, Implementation of the EEN protocols and/or techniques, such as determining when to transition between modes of operation, may be based, for example, on latency constraints of the traffic to be transmitted via the link  112  or communicated up to the MAC  304   a . In instances when latency is not a problem, a series of traffic bursts may be buffered for an acceptable amount of time before waking the PHY device  302 , the MAC  304 , and/or higher layer functions for delivery of the accumulated traffic bursts. 
     Implementation of the EEN protocols and/or techniques, such as determining when to transition between modes of operation, may be based, for example, on signals received from a link partner to which the PHY  302  is communicatively coupled. In this regard, going into and coming out of low(er) power modes may require agreement by the link partner, or at least awareness of what the link partner is doing. For example, in instances that the link partner takes longer to wake up then the PHY  302 , the PHY  302  may need to plan accordingly and allocate sufficient memory to the Tx buffer  310   a.  Conversely, in instances that the link partner wakes up faster than the PHY  302 , the PHY  302  may need to plan accordingly and allocate sufficient memory to the Rx buffer  310   b  and/or instruct the link partner to increase its Tx buffer to hold off transmissions. A similar situation may occur when a link partner has less buffering available than the PHY  302 . Accordingly, in some embodiments of the invention, the control policy may be utilized to dynamically allocate and reallocate as the memory  316 , for example, to supplement the Tx buffer  310  or the Rx buffer  310   b.    
     Implementation of the EEN protocols and/or techniques, such as determining when to transition between modes of operation, may be based, for example, on a type, format, and/or content of packet(s) and/or traffic received from a link partner to which the PHY  302  is communicatively coupled. In this regard, certain distinct packets and/or packet types may trigger the PHY  302  to transition to an energy saving mode and certain distinct packets and/or packet types may trigger the PHY  302  to transition out of an energy saving mode. Also, the PHY  302  may determine how long it may buffer ingress and/or egress traffic based on a type, format, and/or content of packet(s) and/or traffic received. 
       FIG. 3B  is a diagram illustrating multiple PHY devices integrated on chip, wherein each PHY device is operable to implement an EEN control policy, in accordance with an embodiment of the invention. Referring to  FIG. 3B , there is shown a substrate  322  on which a plurality of PHY devices  302   1 , . . . ,  302   N  are fabricated, where N is an integer. Each of the PHYs  302   1 , . . . ,  302   N  may comprise a module  308  which may be as described with respect to  FIG. 3A . Each of the PHYs  302   1 , . . . ,  302   N  may comprise an EEN module  314  which may be as described with respect to, for example,  FIG. 3A . 
     In operation, each module  314   X , where X is an integer between 1 and N, may manage power consumption and performance of PHY  302   X  independently of the other N-1 PHYs. For example, some of the PHYs  302   1 , . . . ,  302   N  may utilize LPI techniques while other may utilize sub-rating. Furthermore, a PHY  302   X  may go into and come out of LPI mode at different times and/or based on different factors than one or more of the other N-1 PHYs. Similarly, a PHY  302   X  utilizing sub-rating may operate at a data rate determined independently of the data rate utilized by one or more of the other N-1 PHYs. 
       FIG. 3C  is a diagram illustrating multiple PHY devices integrated on chip and managed by a plurality of EEN control policies, in accordance with an embodiment of the invention. Referring to  FIG. 3C , there is shown a substrate  332  on which a PHY device  302  and one or more PHY devices  336   1 , . . . ,  336   N  are fabricated, where N is an integer. The PHYs  302  and  336   1 , . . . ,  336   N  may be communicatively coupled via a cross connect  334 . Each of the  302  and  336   1 , . . . ,  336   N  may comprise a module  308  which may be as described with respect to  FIG. 3A . The PHY  302  may also comprise a module  314  which may be as described with respect to  FIG. 3A . Although the substrate  332  comprises only a single PHY  302 , the invention is not so limited. In this regard, the substrate  332  may comprise a plurality of PHYs  302 , each of which may be operable to manage power consumption of a subset of the PHYs  336   1 , . . . ,  336   N . 
     In operation, the module  314   1  may mange power consumption and performance of the PHYs  302  and  336   1 , . . . ,  336   N . In this regard, signals for implementing an EEN control policy may be communicated between the PHY  302  and the PHYs  336   1 , . . . ,  336   N  via the cross connect  334 . Utilizing a common control policy for multiple PHYs may enable, for example, load balancing to achieve greater energy efficiency. In various embodiments of the invention, the PHYs may each utilize a common EEN technique, such as LPI. In other embodiments of the invention, the module  314   1  may generate one set of control signals that are communicatively coupled to each of the PHYs  336   1 , . . . ,  336   N . In this regard, a manner in which each of the PHYs may be reconfigured based on the set of common signals may differ from one PHY to the next. 
       FIG. 4  is a flow chart illustrating implementation of an EEN control policy in a PHY, in accordance with an embodiment of the invention. Referring to  FIG. 4 , the exemplary steps may begin with step  402  when physical layer communications may be established between a PHY in a first link partner and a PHY in a second link partner. Subsequent to step  402 , the exemplary steps may advance to step  404 . 
     In step  404 , logic, circuitry, interfaces, and/or code within the first PHY, such as the EEN module  314  described with respect to  FIGS. 3A-3C , of a first link partner may detect an event and/or condition that, based on an EEN control policy, may trigger a transition into or out of a energy saving mode of operation. Subsequent to step  404 , the exemplary steps may advance to step  406 . 
     In step  406 , the first PHY device may exchange signals and/or packets with the second PHY to coordinate the transition. In this regard, the PHYs may exchange packets and/or physical layer signals. The coordination may comprise, for example, an indication and/or negotiation of when the transition is to happen. Subsequent to step  406 , the exemplary steps may advance to step  408 . 
     In step  408 , the PHY devices may implement the transition into or out of the energy saving mode of operation. In this regard, one or more portions of the PHY devices may be reconfigured via one or more control signals generated by an EEN module  314  based on an EEN control policy. Subsequent to step  408 , the exemplary steps may return to step  404 . 
     Various aspects of a method and system for physical layer control of energy efficient network devices and protocols are provided. In an exemplary embodiment of the invention, operation of a PHY device  202  may be controlled based on one or more energy efficient networking (EEN) control policies executed from within the PHY device  202  ( FIG. 2 ). The one or more control policies may enable management of power consumption associated with communication of data via the PHY device  202 . A mode of operation of the PHY device may be selected based on the control policy. One or more components, such as hybrids  226 , transmitters  214 , receivers  220 , and memory  216   a  and  216   b , of the PHY device  202  may be reconfigured based on the selected mode of operation. The memory  216  within the PHY  202  may be allocated to buffering received and/or to-be-transmitted data based on the selected mode of operation, based on an amount of time required for the reconfiguration, and/or based on an amount of time required for reconfiguration of a link partner communicatively coupled to the PHY device. Conversely, the memory  216  within the PHY  202  may be de-allocated from buffering received and/or to-be-transmitted data, based on the selected mode of operation, on an amount of time required for the reconfiguration, and/or on an amount of time required for reconfiguration of a link partner communicatively coupled to the PHY device. De-allocating memory from buffering may free the memory up to support other functions such as encryption and/or decryption. The reconfiguration may be triggered at a time determined by the control policy. The selected mode of operation may comprise an LPI mode of operation or a subset PHY mode of operation. The control policy may be executed within the PHY device utilizing hardware, software, and/or firmware within the PHY device. Multiple PHY devices  302  and  336  may be integrated on a common substrate  332 , and one of the PHY devices  302  may control operation and/or configuration of one or more of the other PHY devices  336 . 
     Another embodiment of the invention may provide a machine and/or computer readable storage and/or medium, having stored thereon, a machine code and/or a computer program having at least one code section executable by a machine and/or a computer, thereby causing the machine and/or computer to perform the steps as described herein for control of energy efficiency and associated policies in a physical layer device. 
     Accordingly, the present invention may be realized in hardware, software, or a combination of hardware and software. The present invention may be realized in a centralized fashion in at least one computer system, or in a distributed fashion where different elements are spread across several interconnected computer systems. Any kind of computer system or other apparatus adapted for carrying out the methods described herein is suited. A typical combination of hardware and software may be a general-purpose computer system with a computer program that, when being loaded and executed, controls the computer system such that it carries out the methods described herein. 
     The present invention may also be embedded in a computer program product, which comprises all the features enabling the implementation of the methods described herein, and which when loaded in a computer system is able to carry out these methods. Computer program in the present context means any expression, in any language, code or notation, of a set of instructions intended to cause a system having an information processing capability to perform a particular function either directly or after either or both of the following: a) conversion to another language, code or notation; b) reproduction in a different material form. 
     While the present invention has been described with reference to certain embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted without departing from the scope of the present invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the present invention without departing from its scope. Therefore, it is intended that the present invention not be limited to the particular embodiment disclosed, but that the present invention will include all embodiments falling within the scope of the appended claims.