Patent Publication Number: US-9413551-B2

Title: Method and system for network communications via a configurable multi-use Ethernet PHY

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS/INCORPORATION BY REFERENCE 
     This is a continuation-in-part of U.S. patent application Ser. No. 13/308,958 filed Dec. 1, 2011, which is a continuation of U.S. patent application Ser. No. 12/490,209, filed Jun. 23, 2009 (Now U.S. Pat. No. 8,089,984). Each of the above-identified patent applications is 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 network communications via a configurable multi-use Ethernet PHY. 
     BACKGROUND OF THE INVENTION 
     With the increasing popularity of electronics such as desktop computers, laptop computers, and handheld devices such as smart phones and PDA&#39;s, communication networks are becoming an increasingly popular means of exchanging data of various types and sizes for a variety of applications. One set of networking technologies, namely Ethernet, has been particularly successful with regard to deployment in local area networks (LANs) and has made networking useful and affordable to individual and business customers of all levels and sizes. Everyday more and more devices are being equipped with Ethernet interfaces and Ethernet is increasingly being utilized to carry information of all types and sizes including voice, data, and multimedia. Due to the ubiquity of Ethernet in LANs, the advantages of using Ethernet in wide area networks are being recognized and Efforts such as Ethernet in the First Mile IEEE 802.3ah seek to realize these advantages. As the role of Ethernet expands to networks of all topologies and/or technologies, however, equipment manufacturers, service providers, and network administrators are presented with new economic and technological challenges. 
     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 network communications via a configurable multi-use Ethernet PHY, 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 functional block diagram illustrating an exemplary Ethernet connection between two network devices, which may comprise configurable multi-use PHYs, in accordance with an embodiment of the invention. 
         FIG. 2A  is a diagram illustrating managing data transmission via a carrier sense signal of a media independent interface, in accordance with an embodiment of the invention. 
         FIG. 2B  is a flow chart illustrating exemplary steps for managing data transmission via a carrier sense signal of a media independent interface, in accordance with an embodiment of the invention. 
         FIG. 3  is a functional block diagram illustrating a PHY configurable based on characteristics of a link over which it communicates, in accordance with an embodiment of the invention. 
         FIG. 4A  is a diagram illustrating use of a configurable multi-use PHY for Ethernet over DSL communications, in accordance with an embodiment of the invention. 
         FIG. 4B  is a diagram illustrating use of a configurable multi-use PHY for extended reach Ethernet communications, in accordance with an embodiment of the invention. 
         FIG. 4C  is a diagram illustrating use of a configurable multi-use PHY for standard Ethernet communications, in accordance with an embodiment of the invention. 
         FIG. 5A  is a functional block diagram illustrating a network device operable to convey data between network links having different characteristics, in accordance with an embodiment of the invention. 
         FIG. 5B  is a flow chart illustrating exemplary steps for controlling ingress data flow in a network device that conveys data between network links having different characteristics, in accordance with an embodiment of the invention. 
         FIG. 5C  is a flow chart illustrating exemplary steps for controlling egress data flow in a network device that conveys data between network links having different characteristics, 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 network communications via a configurable multi-use Ethernet PHY. In various embodiments of the invention, a first Ethernet PHY may be configured based on characteristics of a network link over which the first Ethernet PHY communicates, energy efficiency considerations, etc. 
     In some embodiments of the invention, a first Ethernet PHY, a first MAC, a second Ethernet PHY, and a second MAC may be integrated within a network device. In such embodiments, data may be received by the second Ethernet PHY, buffered in a queue, and transmitted by the first Ethernet PHY, where the second Ethernet PHY receives the data at a rate that may be different than the rate at which the first Ethernet PHY transmits the data. In some instances, the second Ethernet PHY may be operable to request that a link partner pause or slow down transmission of data based on a status of the queue. 
       FIG. 1  is a functional block diagram illustrating an exemplary Ethernet connection between two network devices, which may comprise configurable multi-use PHYs, 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  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  110   a  and  110   b  are referenced collectively or separately herein as PHY(s)  110 . 
     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, coaxial cable, 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 or 802.16 family of protocols. In various embodiments of the invention, 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 10BASE-T and 100BASE-TX may utilize two pairs of UTP while Ethernet over twisted pair standards 1000BASE-T and 10GBASE-T may utilize four pairs of UTP. 
     The network devices  102  and/or  104  may comprise, for example, switches, routers, end points, computer systems, audio/video (A/V) enabled equipment, or a combination thereof. 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 PHYs  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. In various embodiments of the invention, one or both of the hosts  106  may comprise one or more queues  115   Z  for buffering received and/or to-be-transmitted data. 
     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 PHYs  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 such as a carrier sense signal (CRS). The interfaces  114   a  and  114   b  may be, for example, multi-rate capable interfaces and/or media independent interfaces (xxMII). In this regard, “media independent interface (MII)” is utilized generically herein and may refer to a variety of interfaces such as a media independent interface (MII), a gigabit MII (GMII), a reduced MII (RMII), reduced gigabit MII (RGMII), and 10 gigabit MII (XGMII). In various embodiments of the invention, one or both of the networking subsystems  108  may comprise one or more queues  115   Y  for buffering received and/or to-be-transmitted data. 
     The PHYs  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 PHYs  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 PHYs  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 PHYs  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 PHYs  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 , and convert received physical signals into digital information. In some embodiments of the invention, the PHYs  110  may comprise suitable logic, circuitry, and/or code operable to implement MACSec. In various embodiments of the invention, one or both of the PHY devices  110  may comprise one or more queues  115   X  for buffering receiving and/or to-be-transmitted data. 
     One or both of the PHYs  110  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 (10BASE-T, 100GBASE-TX, 1GBASE-T, and/or 10GBASE-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 PHYs  110  may comprise a backplane PHY capable of operating at one or more standard rates such as 10 Gbps (10GBASE-KX4 and/or 10GBASE-KR); and/or non-standard rates such as 2.5 Gbps and 5 Gbps. One or both of the PHYs  110  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 PHYs  110  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 PHYs  110 . 
     Also, the PHYs  110  may support transmission and/or reception at a high(er) data rate 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 a link partner may comprise a multimedia client. In this regard, the network device  102  may transmit multimedia data, for example, to the link partner at high(er) data rates while the link partner may transmit control or auxiliary data associated with the multimedia content at low(er) data rates. The network device  102  may also support wireless protocols such as the IEEE 802.11 family of standards. 
     Each of the PHYs  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), or in the specific case of Ethernet, energy efficient Ethernet (EEE). For example, the PHYs  110   a  and  110   b  may be operable to support low power idle (LPI) and/or subrating techniques, such as subset PHY for Copper based PHYs. LPI may generally refer to a family of techniques where, instead of transmitting conventional IDLE symbols during periods of inactivity, the PHYs  110   a  and  110   b  may remain silent and/or communicate signals other than conventional IDLE symbols. Subrating 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. The reconfiguration of the PHYs through subrating provides further  FIG. 5A  is a functional block diagram illustrating a network device operable to convey data between network links having different characteristics, in accordance with an embodiment of the invention. Referring to  FIG. 5A , there is shown a network device  500  comprising Ethernet PHYs  310   a  and  310   b , MACs  308   a  and  308   b , and memory  512 . The Ethernet PHYs  310   a  and  310   b  and the MACs  308   a  and  308   b  may be as described with respect to  FIG. 3 . 
     In operation, for example, data may be communicated from the network device  102  to the network device  104  over the link  112 . In such instances, the networking subsystem  108   a  may communicate data via the interface  114   a  to the PHY  110   a  at a higher rate than the line rate, or other specified rate, at which the PHY  110   a  may be operable to output the data onto the link  112 . That is, the networking subsystem  108   a  and the PHY  110   a  may be mismatched with regard to an egress data rate. Consequently, a queue, such as one or more of the queues  115 , that store the egress data may eventually overflow. Accordingly, the rate at which the PHY  110   a  is transmitting data and/or an amount of data waiting to be transmitted may be monitored and the PHY  110   a  may notify the networking subsystem to hold off sending more data to the PHY  110   a  until the PHY  110   a  is ready to receive more data without dropping or corrupting any data. In various embodiments of the invention, the PHY  110   a  may notify the MAC  108   a  via the CRS  120   a  and/or by generating one or more pause frames and conveying the pause frames up to the networking subsystem  108   a  via a receive path of the interface  114   a.    
     In various embodiments of the invention, the CRS  120   a  may be controlled to match the rate at which data comes into the PHY  110   a  from the networking subsystem  108  with the rate at which the data is transmitted onto the link  112 . In this regard, the PHY  110   a  may assert the CRS  120   a  during periods when the PHY  110   a  cannot handle additional data from the networking subsystem  108   a . For example, the PHY  110   a  may be unable to handle additional data from the networking subsystem  108   a  when it is already transmitting data onto the link  112  at the line rate, or other specified maximum rate. The networking subsystem  108   a  may, accordingly, defer transmission until the PHY  110   a  de-asserts the CRS  120   a . The PHY  110   a  may de-assert the CRS  120   a  when the PHY  110   a  can handle additional data from the networking subsystem  108   a . For example, the PHY  110   a  may be able to handle data from the networking subsystem  108  when the rate at which the PHY  110   a  communicates data onto the link  112  drops below the line rate, or other specified rate. 
     In various embodiments of the invention, the PHY  110   a  may generate one or more pause frames and convey the pause frames up to the networking subsystem  108   a  during periods when the PHY  110   a  cannot handle additional data to be transmitted. For example, the PHY  110   a  may be unable to handle additional data from the networking subsystem  108   a  when it is already transmitting data onto the link  112  at the line rate, or other specified maximum rate. Once the PHY  110   a  is ready to receive additional data from the networking subsystem  108  it may generate an unpause frame and convey the unpause frame up to the networking subsystem  108   a . The pause and unpause frames may be sent to the networking subsystem  108  as if they were frames received from a link partner. Accordingly, the networking subsystem  108   a  may be operable to inspect received frames and distinguish pause and unpause frames from other received data. The networking subsystem  108   a  may hold-off conveying data to be transmitted to the PHY  110   a  during periods of time between receiving a pause frame and receiving a corresponding unpause frame. An unpause frame may, for example, comprise a pause frame with a wait time field set to 0. Additionally or alternatively, a MAC may resume sending data to the PHY upon expiration of a timer without having received an unpause frame. 
     In some embodiments of the invention, one or more queues in which the egress data is buffered may be monitored to determine whether the PHY  110   a  is ready to receive data from the networking subsystem  108   a . For example, in instances that a queue  115  in which the egress data is stored reaches a threshold, the PHY  110   a  may assert the CRS  120   a  and/or generate a pause frame to pause or slow down the data being output by the networking subsystem  108   a . Upon the occupied portion of the queue  115  dropping below a particular threshold, the PHY  110   a  may de-assert the CRS  120   a  and/or generate an unpause frame and, upon detecting the de-assertion of the CRS  120   a  and/or the receipt of the unpause frame, the networking subsystem  108   a  may resume sending data to the PHY  110   a  via the interface  114   a.    
     In various embodiments of the invention, the Ethernet PHYs  110  may be configured based on characteristics of the link  112 . The configuration of the PHYs  110  may, in turn, determine the rate at which the PHYs  110  are operable to communicate over the link  112 . Exemplary characteristics of the link  112  factored into the configuration may comprise the length and/or grade or quality of the link  112 . For example, in a local area network (LAN) the link  112  may comprise up to 100 meters of CAT-5 UTP, whereas in an Ethernet over DSL application, the link  112  may comprise up to 2.7 km of CAT-1 UTP. 
     Controlling the flow of traffic between a MAC and PHY utilizing the CRS  120  may thus enable utilizing a single configurable PHY device in various applications. Moreover, utilizing the CRS to control the data flow may enable the configurable multi-use PHY  110  to interface to a legacy MAC, regardless of whether that MAC communicates full-duplex or half-duplex, and regardless whether the MAC was designed for communication over high quality UTP at less than 100 meters, such as the 10/100/1G/10GBASE-T protocols, or for communication over lower grade UTP and/or longer links, such as the 10PASS-TS or 2BASE-TL protocols. That is, a multi-use configurable PHY  110  may be compatible with MACs designed for LAN applications, Ethernet over DSL applications, and other applications. 
       FIG. 2A  is a diagram illustrating managing data transmission via a carrier sense signal of a media independent interface, in accordance with an embodiment of the invention. Referring to  FIG. 2A  there is shown a networking subsystem  108 , a PHY  110 , a queue  115 , and corresponding values of a CRS  120  during a sequence of time instants T 1 -T 5 . 
     The networking subsystem  108  may be as described with respect to  FIG. 1 . The PHY  110  may be the same as the PHYs  110   a  and  110   b  described with respect to  FIG. 1 . The queue  115  may be the same as one or more of the queues  115   X ,  115   Y , and  115   Z  described with respect to  FIG. 1 . The CRS  120  may be the same as the CRS signals  120   a  and  120   b  described with respect to  FIG. 1 . 
     At time instant T 1 , the queue  115  is not, or has not been, filled above the threshold  204 . Accordingly, the CRS  120  is de-asserted and the networking subsystem  108  is communicating data to the PHY  110  at a high(er) data rate (as indicated by the large arrow  156 ) the PHY  110  is transmitting data onto the link  112  a low(er) rate (as indicated by the small arrow  158 ), where the rate at which the PHY  110  transmits onto the link  112  may be determined based on characteristics of the link  112 . 
     At time instant T 2 , the queue  115  may have more data buffered in it than at time instant T 1 ; however, the amount of data has still not surpassed the threshold  204  and thus the CRS  120  remains de-asserted and the data continues to be communicated from the networking subsystem  108  to the PHY  110 . 
     At time instant T 3 , the amount of data in the queue  115  has risen above the threshold  204  and thus the CRS  120  may be asserted and/or a pause frame may be generated and conveyed to the networking subsystem  108 . The PHY  110  may continue to drain the queue  115  by transmitting data onto the link  112 . 
     At time instant T 4 , the PHY  110  may continue to transmit data and drain the queue  115 ; however, hysteresis may be utilized to prevent rapid toggling of the CRS  120  and thus, the CRS  120  may be de-asserted only when the level of data in the queue  115  drops below the threshold  206 . Accordingly, the CRS  120  may remain asserted and communication from the networking subsystem  108  to the PHY  110  may remain paused. 
     At time instant T 5 , the amount of data in the queue  115  may drop below the threshold  206 , accordingly the CRS  120  may be de-asserted and/or a pause frame may be generated and conveyed to the networking subsystem  108  and data may again be communicated from the networking subsystem  108  to the PHY  110 . 
       FIG. 2B  is a flow chart illustrating exemplary steps for managing communication of data from a MAC to a PHY via a carrier sense signal of a media independent interface, in accordance with an embodiment of the invention. Referring to  FIG. 2B , from start step  222 , the exemplary steps may advance to step  224  in which it may be determined whether there is data pending conveyance from a MAC to a PHY via an xxMII. In instances that there is no to-be-transmitted data pending communication from the MAC to the PHY, the steps may remain in step  224  until there is data to be communicated to the PHY. In instances that there is data pending communicated from the MAC to the PHY, the exemplary steps may advance to step  226 . 
     In step  226  it may be determined whether a CRS signal of the xxMII between the MAC and PHY is asserted. In instances, that the CRS is asserted, the exemplary steps may advance to step  234 . 
     In step  234 , the MAC may hold off communication of data to the PHY until the PHY de-asserts the CRS. In this regard, the PHY  110  may de-assert the CRS signal when the amount of data buffered in a transmit queue drops below a threshold. Subsequent to step  234 , the exemplary steps may return to step  224 . 
     Returning to step  226 , in instances that the CRS is not asserted, the exemplary steps may advance to step  228 . In step  228 , the MAC may communicate data to the PHY. Subsequent to step  228 , the exemplary steps may advance to step  230 . 
     In step  230 , data communicated from the MAC to the PHY may be stored in a queue and it may be determined whether the additional data in the queue has filled the queue above a threshold. In instances that the queue is not filled above the threshold the exemplary steps may return to step  224 . In instances that the queue is filled above the threshold the exemplary steps may advance to step  232 . 
     In step  232  the PHY may assert the CRS. Subsequent to step  232 , the exemplary steps may advance to step  234 . 
     In step  234 , the PHY may wait for the amount of data buffered in the queue to be below a threshold as data is read out from the queue and transmitted. Once the queue is below the threshold the PHY may de-assert the CRS and the exemplary steps may return to step  224   
       FIG. 3  is a functional block diagram illustrating a PHY configurable based on characteristics of a link over which it communicates, in accordance with an embodiment of the invention. Referring to  FIG. 3  there is shown a PHY  310  and a MAC  308 . 
     The PHY  310  may be similar to or the same as the PHYs  110   a  and  110   b  described with respect to  FIG. 1 . The MAC  308  may be similar to or the same as the networking subsystem  108 , or a portion thereof, described with respect to  FIG. 1 . The CRS  120  may be as described with respect to  FIG. 1 . 
     The PHY  310  may comprise suitable logic, circuitry, interfaces, and/or code that may enable the PHY  310  to be configured into various modes of operation. The configurability of the PHY  310  is represented by the switching element  316  controlled by a signal  314 . Additionally, as described with respect to  FIGS. 1, 2A, and 2B , the PHY  310  may be operable to control the flow of data from the MAC  308  via the CRS  120  and/or by generating pause frames. 
     The link detection and/or characterization module  318  may comprise suitable logic, circuitry, code, and/or interfaces that may be operable to determine characteristics of the link  304  and generate the control signal  314  accordingly. Exemplary characteristics that may be determined by the module  318  may comprise length, grade, and/or number of available channels or conductors of the link  304 . 
     In operation, the switching element  316  may be configured to select an appropriate mode of operation for communicating over the network link  304 . In some embodiments of the invention, the PHY  310  may comprise the module  318  and configuration of the PHY  310  may be controlled based on an automatic link detection and/or characterization. In other embodiments of the invention, control signal  314 , and thus configuration of the PHY  310 , may be controlled via software and/or manually by a network administrator, application, or end-user. 
       FIG. 4A  is a diagram illustrating use of a configurable multi-use PHY for Ethernet over DSL communications, in accordance with an embodiment of the invention. Referring to  FIG. 4A , there is shown a network device  400  communicatively coupled to a broadband access network  402  and a link partner  408 . The network device  400  comprises a controller  412 , a memory  414 , and Ethernet PHYs  310   a  and  310   b , which are operable to communicate over links  404  and  406 , respectively. 
     The broadband access network  402  may be owned and/or operated by a service provider (e.g., telephone company, cable company, wireless broadband company, etc.). The broadband access network  402  may provide Internet connectivity to homes and business utilizing DSL. 
     The controller  412  may comprise suitable logic, circuitry, interfaces, and/or code that may be operable to process data and/or control operations of the network device  400 . With regard to processing data, the controller  412  may enable packetization, de-packetization, transcoding, reformatting, and/or otherwise processing data received from and/or to be transmitted by the network device  400 . With regard to controlling operations of the network device  400 , the controller  412  may be enabled to provide control signals to the various other portions of the network device  400 . In this regard, the controller  412  may be operable to make decisions and/or generate signals for configuring the Ethernet PHYs  310   a  and  310   b . The controller  412  may also control data transfers between various portions of the network device  400 . The controller  412  may enable execution of applications programs and/or code. In this regard, the applications, programs, and/or code may enable, for example, parsing, transcoding, or otherwise processing of data. Furthermore, the applications, programs, and/or code may enable, for example, configuring or controlling operation of the Ethernet PHYs  310   a  and  310   b  and/or the memory  414 . 
     The memory  414  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 network device  400 . The parameters may comprise configuration data and the code may comprise operational code such as software and/or firmware and the parameters may include adaptive filter and/or block coefficients, but the information need not be limited in this regard. Additionally, the memory  400  may buffer or otherwise store received data and/or data to be transmitted. In various embodiments of the invention, the memory  400  may store instructions, parameters, of other information for configuring the Ethernet PHYs  310   a  and  310   b . Each of the Ethernet PHYs  310   a  and  310   b  may be the same as the PHY  310 , which is described with respect to  FIG. 3 . 
     In operation, the Ethernet PHYs  310   a  and  310   b  may be configured for communication over the respective links  404  and  406 . In an exemplary embodiment of the invention, the link  404  may comprise voice grade UTP designed and/or suited for DSL and the link  406  may comprise less than 100 meters of CAT-5e UTP. Accordingly, the Ethernet PHY  310   a  may be configured into an Ethernet over DSL mode and the Ethernet PHY  310   b  may be configured into a standard Ethernet mode. In this regard, the coding and signaling techniques utilized by the Ethernet PHY  310   a  may adhere to, for example, 10PASS-TS or 2BASE-TL. In this regard, the network device  400  may function as a modem, router, and/or switch to provide Internet access to devices such as the device  408 . The Ethernet PHY  310   b , on the other hand, may utilize coding and signaling techniques that adhere to, for example, one of 10BASE-T, 100BASE-T, 1000BASE-T, or 10GBASE-T. 
     The protocols and link characteristics described with regard to  FIG. 4A  are for illustration purposes and the invention is not so limited. Also, the network device  400  comprises two PHYs for illustration only and a device such as network device  400  may comprise any number of Ethernet PHYs each of which may be configurable and/or may communicate over copper, optical fiber, or backplane. In one application, the Ethernet PHY can be designed to communicate with the broadband access network  402  via a PON protocol. For example, communication with the broadband access network  402  can be enabled by EPON as defined by IEEE 802.3, GPON, BPON, xGPON, or NGPON as defined by ITU-T, or the like. In a further example, the Ethernet PHY can be designed to communicate using a PON protocol over a non-optical PHY, such as that defined by EPON Protocol Over Coax (EPoC). 
       FIG. 4B  is a diagram illustrating use of a configurable multi-use PHY for extended reach Ethernet communications, in accordance with an embodiment of the invention. Referring to  FIG. 4B , there is shown a network device  400  communicatively coupled to a broadband access network  420  and a link partner  408 . The network device  400 , its PHYs  310   a  and  310   b , controller  412 , and memory  414  may be as described with respect to  FIG. 4A . 
     The broadband access network  420  may be owned and/or operated by a service provider (e.g., telephone company, cable company, wireless broadband company, etc.). The broadband access network  420  may provide internet connectivity to homes and businesses utilizing Extended reach Ethernet techniques such as those described in U.S. patent application Ser. No. 61/101,072 filed on Sep. 29, 2009, and U.S. patent application Ser. No. 12/495,496 filed Jun. 30, 2009, which are incorporated by reference in their entirety. In this regard, the rate at which the broadband access network  420  communicates with the network device  400  may be adapted based on characteristics of the link  424 , where exemplary characteristics comprise a grade of the link, a length of the link, a number of channels available on the link, temperature of the link, and interference present on the link. 
     In operation, the Ethernet PHYs  310   a  and  310   b  may be configured for communication over the respective links  424  and  406 . In an exemplary embodiment of the invention, the link  424  may comprise more than 100 meters of Cat-5e UTP and the link  406  may comprise less than 100M of CAT-5e UTP. Accordingly, the Ethernet PHY  310   a  may be configured for extended reach Ethernet and the Ethernet PHY  310   b  may be configured into a standard Ethernet mode. In this regard, the rate at which data is communicated over the link  424  and/or the number of channels of the link  424  over which data is communicated may be configured based on the characteristics of the link  424 . Adjusting the data rate of communications on the link  424  may compensate, for example, for the increased delay, noise, and/or attention of the link  424 . In this regard, the network device  400  may function as a modem, a switch, and/or a router to provide Internet access to devices such as the device  408 . The Ethernet PHY  310   b , on the other hand, may communicate over the link  406  may at a standard rate as defined by, for example, 10BASE-T, 100BASE-T, 1000BASE-T, or 10GBASE-T. 
     The protocols and link characteristics described with regard to  FIG. 4B  are for illustration purposes and the invention is not so limited. For example, both links may be longer than 100M and both Ethernet PHYs  310   a  and  310   b  may be configured into an Extended reach mode. Also, the network device  400  comprises two PHYs for illustration only and a device such as network device  400  may comprise any number of Ethernet PHYs each of which may be configurable and/or may communicate over copper, optical fiber, or backplane. In general, the particular configuration of the Ethernet PHY can be chosen to support the particular characteristics of the broadband access network  420  that is implemented by the service provider (e.g., telephone company, cable company, wireless broadband company, etc.) As such, the Ethernet PHY can be configured to support service provider links that are based on copper, wireless and/or optical technologies. As noted, such configurability can be based on the switching element  316 , which may be configured to select an appropriate mode of operation for communicating over the link to the broadband access network  420 . 
       FIG. 4C  is a diagram illustrating use of a configurable multi-use PHY for standard Ethernet communications, in accordance with an embodiment of the invention. Referring to  FIG. 4C , there is shown a network device  400  communicatively coupled to a link partner  432  and a link partner  408 . The network device  400 , its PHYs  310   a  and  310   b , controller  412 , and memory  414  may be as described with respect to  FIG. 4A . 
     In operation, the Ethernet PHYs  310   a  and  310   b  may be configured for communication over the respective links  434  and  406 . In an exemplary embodiment of the invention, the links  434  and  406  may each comprise less than 100 meters of CAT-5e UTP. Accordingly, the Ethernet PHYs  310   a  and  310   b  may be configured into a standard Ethernet mode. In this regard, the network device  400  may function as a network switch, network controller, and/or a router between the devices  432  and  408  and possibly additional devices not shown in  FIG. 4C . The Ethernet PHYs  310   a  and  310   b  may each communicate over the link  406  at a standard rate as defined by, for example, 10BASE-T, 100BASE-T, 1000BASE-T, or 10GBASE-T, and in some instances may communicate at different rates, which may be non-standard rates. 
     The protocols and link characteristics described with regard to  FIG. 4B  are for illustration purposes and the invention is not so limited. For example, both links may be longer than 100 meters and both Ethernet PHYs  310   a  and  310   b  may be configured into an extended reach mode. Also, the network device  400  comprises two PHYs for illustration only and a device such as network device  400  may comprise any number of Ethernet PHYs each of which may be configurable and/or may communicate over copper, optical fiber, or backplane. 
       FIG. 5A  is a functional block diagram illustrating a network device operable to convey data between network links having different characteristics, in accordance with an embodiment of the invention. Referring to  FIG. 5A , there is shown a network device  500  comprising Ethernet PHYs  310   a  and  310   b , MACs  308   a  and  308   b , and memory  512 . The Ethernet PHYs  310   a  and  310   b  and the MACs  308   a  and  308   b  may be as described with respect to  FIG. 3 . 
     The memory  512  may comprise suitable logic, circuitry, interfaces, and/or code that may be operable to buffer data being conveyed between the MACs  308   a  and  308   b.    
     In operation, data may be received via one of the Ethernet PHYs  310   a  and  310   b  and transmitted via the other of the PHYs  310   a  and  310   b . The PHY  310   a  may be configured based on characteristics of the link  502  and the PHY  310   b  may be configured based on characteristics of the link  504 . Accordingly, the rate at which the data is transmitted by one of the PHYs  310   a  and  310   b  may be different than the rate at which the data may be transmitted via the other of the PHYs  310   a  and  310   b . For example, the links  502  and  504  may comprise different physical media (e.g., copper, optical, wireless, etc.), comprise different grades of physical media, be different lengths, be coupled to different types of network devices, and/or comprise a different number of channels. Consequently, as data is received via the Ethernet PHY  310   a  for transmission via the Ethernet PHY  310   b  the different data rates may be matched by buffering data in the memory  512 . 
     In an exemplary embodiment of the invention, data may arrive via the Ethernet PHY  310   a  faster than the Ethernet PHY  310   b  may transmit the data. Consequently, the Ethernet PHY  310   b  may utilize CRS  120   b  to control the transfer of data from the MAC  308   b  to the Ethernet PHY  310   b , which in turn may determine the rate at which the MAC  308   b  reads data from the memory  512 . Consequently, the memory  512  may eventually reach a level or capacity that is beyond a particular threshold and the memory  512  may be unable to receive more data from the MAC  308   a  until additional data is read from the memory  512  and transmitted by the Ethernet PHY  310   b . An indication that the memory  512  is filled above the particular threshold may be provided to the MAC  308   a  via a signal  506   a . Upon detecting that the memory  512  is at a level above the particular threshold, the MAC  308   a  and/or the PHY  310   a  may notify the link partner sending the data. As a result, the link partner may pause transmission of the data or alter a rate at which it transmits the data to the network device  500 . In this manner, the network device  500  may be operable to utilize a back pressure to control data transmitted to the network device  500  by a link partner. Additional details of controlling traffic in the network device  500  are described with respect to  FIGS. 5B and 5C  below. 
     In one embodiment of the invention, the network device  500  may be a MACSec PHY adapted to convert between two data rates and/or network links. In this regard, a second PHY  310   b  may be instantiated or coupled to a MACSec PHY such that the MACSec PHY is operable to interface to two network links. In this regard, the network device  500  may be configurable to operate as a MACSec PHY or as a converter between two network links. The memory  512  may either be utilized for implementing MACSec protocols or for buffering data to rate match the network link  502  and the network link  504 . 
       FIG. 5B  is a flow chart illustrating exemplary steps for controlling ingress data flow in a network device that conveys data between network links having different characteristics, in accordance with an embodiment of the invention. Referring to  FIG. 5B , start step  532 , the exemplary steps may advance to step  534 . In step  534 , it may be determined whether the memory  512  is at a level that is above a particular threshold, where the threshold may be configurable. In instances that the memory  512  is not at a level that is above the particular threshold, the exemplary steps may advance to step  536 . 
     In step  536 , the PHY  310   a  and MAC  308   a  may be configured and/or prepared to receive data. In this regard, in some instances the MAC  308   a  and/or the PHY  310   a  may be enabled to operate in an energy saving mode and in step  536  the MAC  308   a  and/or the PHY  310   a  may transition out of the energy saving mode and may be trained and/or synchronized with a link partner. Upon receiving data from the link partner, the exemplary steps may advance to step  538 . 
     In step  538  the PHY  310   a  may process the received data and convey the received data to the MAC  308   a . The MAC  308   a  may store the data in the memory  512 . Subsequent to step  538 , the exemplary steps may advance to step  534 . 
     Returning to step  534 , in instances that the memory  512  is at a capacity or level that is above the particular threshold, the exemplary steps may advance to step  540 . In step  540 , the MAC  308   a  and/or PHY  310   a  may generate one or more signals or otherwise notify link partner(s) to pause or slow transmission of data to the network device  500 . Subsequent to step  540 , the exemplary steps may advance to step  542 . 
     In step  542 , the MAC  308   a  and/or the PHY  310   a  may wait for the memory  512  to drain below a particular threshold. In this regard, the duration of the wait may depend on the rate at data from the memory  512  by the MAC  308   b  and being transmitted by the PHY  310   b . In some embodiments of the invention, portions of the network device  500 , such as the MAC  308   a  and/or the PHY  308   a , may transition to an energy saving mode during this time. Once an amount of data buffered in the memory  512  drops below the particular threshold, the exemplary steps may advance to step  544 . 
     In step  544 , the MAC  308   a  and/or the PHY  310   a  may stop applying back pressure to the link partner and/or notify the link partner to resume transmission of data to the network device  500 . Subsequent to step  544 , the exemplary steps may advance to step  536 . 
       FIG. 5C  is a flow chart illustrating exemplary steps for controlling egress data flow in a network device that conveys data between network links having different characteristics, in accordance with an embodiment of the invention. Referring to  FIG. 5C , subsequent to start step  542 , the exemplary steps may advance to step  544 . 
     In step  544 , it may be determined whether there is data to be transmitted that is buffered in the memory  512 . In instances that there is data buffered in the memory  512 , the exemplary steps may advance to step  548 . In step  548 , it may be determined whether the CRS  120   b  is asserted. In instances that CRS  120   b  is not asserted, the exemplary steps may advance to step  552 . In step  552 , the MAC  308   b  may read data out of the memory  512 , process it accordingly, and convey it to the PHY  310   b . The PHY  310   b  may process the data accordingly and transmit it onto the link  504 . Subsequent to step  552 , the exemplary steps may advance to step  544 . Returning to step  548 , in instances that CRS  120   b  is asserted, the exemplary steps may advance to step  550 . In step  550 , the MAC  308   b  may hold-off or defer reading data from the memory  512  and conveying the data to the PHY  310   b  until CRS  120   b  is de-asserted. Upon de-assertion of the CRS  120   b , the exemplary steps may advance to step  552 . 
     Returning to step  544 , in instances that there is no buffered data in the memory  512 , which is pending transmission, the exemplary steps may advance to step  546 . In step  546  the MAC  308   b  and the PHY  310   b  may await arrival of data to be transmitted. In some embodiments of the invention, the MAC  308   b , the PHY  310   b , and/or other portions of the network device  500  may be configured to operate in an energy saving mode during this time. 
     Various aspects of a method and system for network communications via a configurable multi-use Ethernet PHY are provided. In an exemplary embodiment of the invention, a first Ethernet PHY  310  may be configured based on characteristics of a network link  304  over which the first Ethernet PHY  310  communicates, energy efficiency, etc. A rate at which data is conveyed from a first media access controller (MAC)  308  to the first Ethernet PHY  310  via a media independent interface (MII)  114  may be controlled via a carrier sense signal  120  of the MII  114 . The carrier sense signal  120  may be controlled based on a rate at which the first Ethernet PHY  310  transmits data over the network link  304 . The rate at which the first Ethernet PHY  310  transmits data over the network link  304  may be determined by monitoring a queue  115  that buffers data to be transmitted. The carrier sense signal  120  may be asserted when an amount of data stored in the queue  115  is above a threshold. 
     The carrier sense signal  120  may be de-asserted when the amount of data stored in the queue  115  is below a threshold. The first Ethernet PHY  310  may be configured based on characteristics of the network link  304 , which can be based on copper, optical, or wireless transmission media. The MII  114  may comprise one of a media independent interface (MII), a gigabit MII (GMII), a reduced MII (RMII), reduced gigabit MII (RGMII), and 10 gigabit MII (XGMII). 
     In some embodiments of the invention, a first Ethernet PHY  310   b , a first MAC  308   b , a second Ethernet PHY  310   a , and a second MAC  308   a  may be integrated within a network device  500 . In such embodiments of the invention, data may be received by the second Ethernet PHY  310   a , buffered in a queue  512 , and transmitted by the first Ethernet PHY  310   b , where the second Ethernet PHY  310   a  may receive the data at a rate different than the rate at which the first Ethernet PHY  310   b  transmits the data. In some instances, the second Ethernet PHY  310   a  may be operable to request that a link partner pause or slow down transmission of data based on a status of the queue  512 . As described above, different transmission rates can be used by the configured Ethernet PHYs. In one example, a different transmission rate can be used through subrating of the Ethernet PHY. In one scenario, such subrating of the Ethernet PHY can be implemented by a service provider for power savings, for different service levels for customers, etc. 
     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 network communications via a configurable multi-use Ethernet PHY. 
     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.