Patent Publication Number: US-9843492-B2

Title: Ethernet data rate selection based on cable parameters

Description:
TECHNICAL FIELD 
     The present disclosure relates generally to network cable configuration and management, specifically, the characterization of cables at link-up times and during in-service monitoring to provide improved data throughput. 
     BACKGROUND 
     In traditional Institute of Electrical and Electronics Engineers (IEEE) 802.3 Ethernet standards, such as Gigabit Ethernet (1 GE) and 10 Gigabit Ethernet (10 GE), data rates may be defined. The data rates may be based on specified cable types, electromagnetic noise that can occur in a cable that runs alongside one or more other signal-carrying cables (alien crosstalk), and cable length. For example, 1000 Base-T (which is a standard for 1 GE, also known as 802.3ab) specifies a maximum cable length of 100 meters using Category 5 cable or better. Alternatively, 10 G Base-T (which is a standard for 10 GE, also known as 802.3an) specifies a maximum cable length of 100 meters using Category 6a cable or better. Under the 10 G Base-T standard, alien crosstalk may be handled by a required cable bundle of six cables grouped around a single cable. 
     In most Enterprise Access networks, conditions may or may not meet the specified standards. When conditions are worse than desired, it may result in unreliable performance for end users. On the other hand, conditions better than specified may result in limiting the deployment options of the network. In prior systems, Telecommunications Industry Association (TIA) Engineering Committee TR-42 has proposed performing cable characterization tests on cable at the time of cable installation. Gathered characterization data may then be used to determine possible data rates that can be used while still providing reliable performance. 
     However, upon the application of multi-Gig (mGig) standards, such as IEEE Next Generation Enterprise Access BASE-T (NGEABT—802.3bz) over currently installed cables, the cable data will be unknown for new data rates (such as 2.5 G and 5 G). For example, the NGEABT standard may provide multi-rate 2.5 G/5 G standard for 802.11ac Wave 2. Such standard application may lead to at least two problems upon installation. First, data rate performance on the network links upon startup may be negatively affected. Furthermore, dynamic noise conditions caused by alien cross talk as well as variations due to temperature, voltage, and link speed changes amongst the aggressors in a particular cabling arrangement (for example, in a cable bundle of six cables grouped around a single cable, the six cables are aggressor cables, while the single cable may be referred to as the victim cable. 
     Prior approaches have attempted to re-characterize previously installed cables to determine 2.5 G or 5 G data rate selection. However, such an approach may be very costly due to the large currently installed base number of Cat 5e and Cat 6 cables. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
       The accompanying drawings, which are incorporated in and constitute a part of this disclosure, illustrate various embodiments of the present disclosure. In the drawings: 
         FIG. 1  illustrates a sample network topology where embodiments of the present disclosure may be performed; 
         FIG. 2  illustrates a sequence where embodiments of the present disclosure may be performed; 
         FIG. 3  shows a network device in greater detail; 
         FIG. 4  is a flow chart illustrating embodiments of the present disclosure; and 
         FIG. 5  is a flow chart illustrating embodiments of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     Overview 
     Methods and systems are disclosed which can perform cable characterization at link-up and during in-service monitoring to provide the best data throughput. In some embodiments a plurality of frequency tones may be sent across a cable to a remote system. A plurality of return loss values associated with sending the plurality of frequency tones may then be measured and stored. Next, a crosstalk value across the cable may be computed. A quality value for the cable may then be determined based on at least the plurality of return loss values and the crosstalk value. 
     Both the foregoing overview and the following example embodiment are examples and explanatory only, and should not be considered to restrict the disclosure&#39;s scope, as described and claimed. Further, features and/or variations may be provided in addition to those set forth herein. For example, embodiments of the disclosure may be directed to various feature combinations and sub-combinations described in the example embodiment. 
     Example Embodiments 
     The following detailed description refers to the accompanying drawings. Wherever possible, the same reference numbers are used in the drawings and the following description to refer to the same or similar elements. While embodiments of the disclosure may be described, modifications, adaptations, and other implementations are possible. For example, substitutions, additions, or modifications may be made to the elements illustrated in the drawings, and the methods described herein may be modified by substituting, reordering, or adding stages to the disclosed methods. Accordingly, the following detailed description does not limit the disclosure. Instead, the proper scope of the disclosure is defined by the appended claims. 
       FIG. 1  illustrates a sample network topology that will be used in the following description to illustrate embodiments of the present disclosure. The described network topology may exist in a networking environment  100 . For example, networking environment  100  may be any type of system that transmits data packets over a network. As an example, networking environment  100  may be an environment enabled to provide voice communications, and video and data services. 
     Networking environment  100  may be based on a bi-directional transfer of packet based service, such as Internet Protocol (IP) traffic, between any number of network devices. Networking environment  100  may further include a plurality of gateways (not shown), for example, but not limited to cable modems, routers, switches, set top boxes, and computers. Networking environment  100  may include any combination of wide area networks (WANs), local area networks (LANs), or other networks suitable for packet-type communications, such as Internet communications. 
     Networking environment  100  may be designed to transmit a stream of data packets from one network device to other network devices. Networking environment  100  may comprise any number of network devices both inside and outside the confines of fabric  110 . Network devices may be routers, bridges, fabric edge nodes, or other network devices capable of receiving and transmitting a data stream from a source network device to a destination network device. Specifically, in embodiments of the present disclosure any of the described network devices may operate the disclosed embodiments of the present disclosure. Similarly, local system  110  and remote system  120  may be found on network devices within networking environment  100 . Network devices generally are discussed in further detail in regards to  FIG. 3 . 
     A local system  110  may be a network device connected to a remote system  120  over an Ethernet cable  130 . In some embodiments of the present disclosure, Ethernet cable  130  may be a Cat 5e, Cat6, or Cat6a cable. Local system  110  may comprise a CPU  112  capable of running software to execute embodiments of data rate selection. CPU  112  may be in communication with a local port application-specific integrated circuit (Port-ASIC)  114 . CPU  112  and local Port-ASIC  114  may further be in communication with a local physical (PHY) network device layer  116 . Local PHY network device layer  116  may be further in communication with a registered jack (RJ) port, such as a RJ45 port  118 . 
     Similarly, remote system  120  may comprise a CPU  122  capable of running software to execute embodiments of data rate selection. CPU  122  may be in communication with a remote port application-specific integrated circuit (Port-ASIC)  124 . CPU  122  and remote Port-ASIC  124  may further be in communication with a remote physical (PHY) network device layer  126 . Remote PHY network device layer  126  may be further in communication with a registered jack (RJ) port, such as a RJ45 port  128 . 
     At power-up of a network device such as local system  110  or during a physical link-up between local system  110  and remote system  120 , cable characterization may be performed to measure cable parameters of a cable such as Ethernet cable  130  prior to starting a standard auto-negotiation process. Once the quality level and the type of Ethernet cable  130  are determined, local PHY network device layer  116  may operate to restrict auto-negotiation ability parameters to levels that can be reliably supported based on the determined conditions. 
     A non-exhaustive list of parameters that may be determined during the cable characterization includes: a half power point (3 dB bandwidth) determination, cable attenuation (insertion loss), cable return loss, and detected crosstalk. Once remote system  120  is powered-up, local PHY network device layer  116  may perform testing by sending frequency tones on each set of 4-wire pairs. In some embodiments, the frequency tones may range from 10 MHz to 500 MHz with 10 MHz steps. Remote PHY network device layer  126  may store the amplitude of the different frequencies in a local static random access memory (SRAM) associated with the remote system  120 . 
     Concurrently, local PHY network device layer  116  may measure the return loss and store the return loss information into the local SRAM. Furthermore, the crosstalk occurring between local system  110  and remote system  120  may be computed. Notably, discernable differences in crosstalk may distinguish between Cat 6A cabling versus Cat6 and Cat5e cabling. 
     Once the above cable characteristics have been gathered, embodiments of the present disclosure may perform auto-negotiation at 1 GE. The auto-negotiation may employ extended Organizationally Unique Identifiers (OUIs) to handle identifying exchange insertion loss and return loss values between local PHY network device layer  116  and remote PHY network device layer  126 . Software operating an operating system (such as Internetwork Operating System [IOS]) on CPU  112  may read the recommended maximum data rates and start final auto-negotiation. 
     During network operation, signal-to-noise ratios (SNR), low density parity checks (LDCP), and bit error rates (BER) may each be monitored across Ethernet cable  130 . These monitored values may be used to help avoid issues if there are dynamic changes in alien crosstalk or other impactful changes in network environment  100 . For example, in some embodiments, BER is maintained at a level between 1×10e^-10 to 1×10e^-12. As part of this feature, a fast re-train may be employed to re-optimize a Fast Ethernet adapter associated with a network device. In some embodiments, the fast re-train may result in a new set of Digital Feedback Equalization (DFE) feedback coefficients sent to the network device. 
     In some situations, the rate of fast re-trains is too quick (for example, occurring every second). In this scenario, a speed shift down procedure may be started that includes sending messages to remote PHY network device layer  126  and to local Port-ASIC  114 . Assuming acceptable BER levels, some embodiments may send messages to remote PHY network device layer  126  via auxiliary channel bits (AUX bit) found in a frame with 16 discrete levels of pulse amplitude modulation (16-PAM). In some embodiments, two AUX bits in the 16-PAM frame may be used to express values corresponding to 100M, 1 G, 2.5 G, 5 G, and 10 G speeds. For example, 000 may indicate 100M, 001 may indicate 1 G, 010 may indicate 2.5 G, 011 may indicate 5 G, and 100 may indicate 10 G. 
     Subsequently, local Port-ASIC  114  may update a Transmit-configuration status register at local PHY network device layer  116 . Local Port-ASIC  114  may further send a current transmit congestion status word. In some embodiments, the current transmit congestion status word may be configured to indicate one of a plurality of congestion levels. Finally, local Port-ASIC  114  may generate an interrupt containing at least an interrupt reason and an interrupt mask register value. 
     In embodiments where the BER is at an acceptable value for a predetermined time span, and where there are no fast re-trains occurring, local PHY network device layer  116  may advertise a speed up command to increase the speed of the associated Ethernet card at local Port-ASIC  114  and remote PHY network device layer  126 . All auto-negotiation modes may be user-configurable via Management Data Input-Output (MDIO) registers. 
     Turning to  FIG. 2 , embodiments of a bring-up process  200  for remote system  120 . First, it may be determined whether remote system  120  is powered or if remote system  120  requires power to be provided by local system  110 . In some embodiments, local system  110  may supply such power through Power over Ethernet (PoE). At stage  210 , local system  110  may set Data Terminal Equipment (DTE) powered device (PD), Non-PD, and Link Status/Interrupt values to 0. This may set the Interrupt status to inactive. Furthermore, at stage  210  local system  110  may start a forced auto-negotiation for a 1 GE data rate. 
     If the auto-negotiation is successful, then it may be determined that remote system  120  does not require PoE. Subsequently, process  200  may proceed to stage  260 . If the auto-negotiation hangs for a period of time  220  (for example, ˜four seconds), the auto-negotiation may be deemed unsuccessful, then it may be determined at stage  230  that remote system  120  does not have power. 
     If remote system  120  does not have power, process  200  may proceed to stage  240 . At stage  240 , IEEE standard DTE algorithms may be employed by local PHY network device layer  116  to determine the DTE type of remote system  120 . In some embodiments the DTE algorithm may indicate a powered or non-powered status for remote system  120  based on bandwidth and return loss measurements. 
     At stage  250 , the PD and non-PD status values may be set. For example, if remote system  120  is non-PD, local PHY network device layer  116  may set non-PD status to 1 and PD status to 0. Alternatively, if remote system  120  is PD, local PHY network device layer  116  may set non-PD status to 0 and PD status to 1. After stage  250 , CPU  112  may determine an amount of power to be supplied to remote system  120 . In some embodiments, the power determination may be based on a higher level protocol, such as Link Layer Discovery Protocol (LLDP). 
     Next, process  200  may proceed to stage  260  where cable characterization may commence as both local system  110  and remote system  120  are powered. In embodiments of the present disclosure, cable characterization may occur prior to the selection of the operating data speed via auto-negotiation. 
     Cable characterization may measure 3 dB bandwidth, insertion loss and return loss parameters. First, local PHY network device layer  116  may send frequency tones from 10 MHz to 500 MHz in 10 MHz steps. Remote PHY network device layer  126  may store the recorded amplitude associated with each of the frequencies. In some embodiments, the amplitudes may be stored in a local SRAM in remote system  120 . Next, local PHY network device layer  116  may measure and store the subsequent return loss values. In some embodiments, the return loss values may be stored in a local SRAM in local system  110 . 
     Process  200  may then proceed to stage  260 . At stage  260 , local PHY network device layer  116  may perform auto-negotiation at 1 GE. This auto-negotiation may employ extended OUIs to handle identifying exchange insertion loss and return loss values between local PHY network device layer  116  and remote PHY network device layer  126 . The IOS software on CPU  112  and CPU  122  may both read the recommended maximum data rates and start final auto-negotiation at the determined optimum data rate. 
       FIG. 3  shows a network device (such as local system  110 ) in greater detail. A network device may include a processing device  302 , a memory  304 , input/output (I/O) devices  306 , and a network interface  308 , each of which may be communicatively coupled via a local interface (not shown). Processing device  302  may be a hardware device for executing software, particularly that which is stored in memory  304 . Processing device  302  may be any custom made or commercially available processor, a central processing unit (CPU), an auxiliary processor among several processors, a semiconductor-based microprocessor (in the form of a microchip or chip set), a microprocessor, or generally any device for executing software instructions. Software executed by processing device  302  may include software at least capable of operating described embodiments of the present disclosure. 
     Network interface  308  may include one or more devices that communicate both inputs and outputs, for instance but not limited to, a modulator/demodulator (modem for accessing another device, system, or network), a radio frequency (RF) transceiver or other type of transceiver, a telephonic interface, a bridge, a router, etc. 
     I/O devices  306  may include input devices, for example but not limited to, a keyboard, mouse, scanner, microphone, etc. Furthermore, the I/O devices  206  may also include output devices, for example but not limited to, a printer, display, etc. 
     The local interface may be, for example but not limited to, one or more buses or other wired or wireless connections. The local interface may have additional elements, which are omitted for simplicity, such as controllers, buffers (caches), drivers, repeaters, and receivers, to enable communications. Further, local interface  310  may include address, control, and/or data connections to enable appropriate communications among the aforementioned components and provides the interface to communicate with a network controller, a host tracking database, a fabric edge router, or any number of other network devices in networking environment  100 . 
     In some embodiments, a network device may further be configured with an integrated storage device  312  coupled to local interface  310 . Storage device  312  may be configured to buffer a plurality of data packets. One or more such buffers may be dedicated buffers for storing captured packets. In some embodiments, storage device  312  may be externally coupled to a content server (not shown). 
     Memory  304  may include a suitable operating system (O/S)  314 . Operating system  314  essentially may control the execution of other computer programs, such as scheduling, input-output control, file and data management, memory management, and communication control and related services. Logic  316  may include executable code to send service requests to the local system, the remote system, a fabric edge router, or any number of other network devices in networking environment  100 . 
     Memory  304  may include any one or combination of volatile memory elements (e.g., random access memory (RAM, such as DRAM, SRAM, SDRAM, etc.)) and nonvolatile memory elements (e.g., ROM, hard drive, tape, CDROM, etc.). Moreover, the memory  304  may incorporate electronic, magnetic, optical, semi-conductive, and/or other types of storage media. Note that memory  304  may have a distributed architecture, where various components are situated remotely from one another, which can be accessed by the processing device  302 . 
     The software in memory  304  may include one or more separate programs, each of which comprises an ordered listing of executable instructions for implementing logical functions. In the embodiment shown in  FIG. 3 , the software in memory  304  may include operating system  314  and logic  316 , as explained above. Functionality of logic  316  may be implemented using a single module, or distributed among a plurality of modules. 
     When logic  316  is in operation, processing device  302  may be configured to execute logic  316  stored within memory  304 , to communicate data to and from memory  304 , and to generally control operations of logic  316 . Logic  316  and O/S  314 , in whole or in part, but typically the latter, are read by processing device  302 , perhaps buffered within processing device  302 , and then executed. 
     The network controller may include a communication interface suitable for enabling communication (e.g., TCP/IP) of data packets with other network devices  218  of network environment  100 . For instance, the communication interface may be of a type suitable for communication over an IP network, a coaxial cable network, an HFC network, and/or wireless network, among others. 
     Having described various components of certain embodiments of network environment  100 , a method  400  implemented by one or more network devices employed on network environment  100  will now be described with reference to  FIG. 4 . Method  400  may begin at step  410  where a plurality of frequency tones may be sent from a local system across a cable to a remote system. In some embodiments, the plurality of frequency tones may range from 10 MHz to 500 MHz. For example, the plurality of frequency tones may be sent to the remote system in 10 MHz steps. 
     Method  400  may next proceed to step  420 . At step  420 , a plurality of return loss values associated with sending the plurality of frequency tones may be measured by the local system. 
     Method  400  may next proceed to step  430 . At step  430 , the plurality of return loss values may be stored. In some embodiments, the plurality of return loss values may be stored by the remote PHY in a local SRAM. Method  400  may next proceed to step  440 . At step  440 , a crosstalk value may be calculated across the cable. 
     Finally method  400  may reach step  450 . At step  450 , a quality value for the cable may be determined based on at least the plurality of return loss values and the crosstalk value. In some embodiments, after the quality value is determined, auto-negotiation may then be performed at 1 GE across the cable. The auto-negotiation process may include sending extended Organizationally Unique Identifiers to the remote system. Through this process, the local system and the remote system may exchange insertion-loss and return loss values with one another. These values may be used to determine a maximum data rate to be used in final auto-negotiation. 
     Once quality values have been determined, embodiments of the present disclosure may describe a method  500  implemented by one or more network devices employed on network environment  100  to provide in-service dynamic noise optimization as will now be described with reference to  FIG. 5 . Method  500  may begin at step  510  where signal to noise ratios may be monitored across the cable. Similarly, at step  510  Low Density Parity Check statuses may be monitored across the cable. Furthermore, Bit_error rates may also be monitored. 
     Method  500  may proceed to step  520 . At step  520  it may be detected whether the Bit-Error rates have exceeded a predetermined value. In some embodiments, the predetermined value may be between 1×10e^-10 to 1×10e^-12 inclusive. 
     Method  500  may proceed to step  530 . At step  530  a fast re-train may be performed to re-optimize a plurality of Digital Feedback Equalization (DFE) feedback coefficients associated with the Bit-Error rates. Subsequently, at step  540  it may be determined if a rate of fast re-trains is above a predetermined threshold. In some embodiments, the threshold may be one second. 
     If the rate of fast re-trains is above a predetermined threshold method  500  may proceed to step  545  where a speed shift-down procedure may be started. The speed shift-down procedure may comprise sending one or more messages to the remote system and to a local Port-ASIC to lower transmission speed across the cable. In some embodiments, the one or more messages to the remote system may indicate a desired speed in one or more AUX bits. 
     The messages themselves may comprise 16-PAM/DSQ128 or any other line coded frames. For example, in some embodiments, 000 may indicate 100M, 001 may indicate 1 G, 010 may indicate 2.5 G, 011 may indicate 5 G, and 100 may indicate 10 G. In some embodiments, the one or more messages to the local Port-ASIC may comprise at least a transmission status register and a transmission status word. Furthermore, an interrupt may be generated comprising an interrupt reason and mask register value. 
     Method  500  may proceed to step  550 . At step  550 , it may be detected whether the Bit-Error rates have stayed at or below the predetermined value for a predetermined period of time after the speed shift-down. If so, method  500  may proceed to step  560  where a speed up command may be sent to the remote system and to a local Port-ASIC to raise transmission speed across the cable. In some embodiments, the speed up command may indicate a last advertised speed. 
     Embodiments of the disclosure, for example, may be implemented as a computer process (method), a computing system, or as an article of manufacture, such as a non-transitory computer program product or computer readable media. The computer program product may be a computer storage media readable by a computer system and encoding a computer program of instructions for executing a computer process. The computer program product may also be a propagated signal on a carrier readable by a computing system and encoding a computer program of instructions for executing a computer process. Accordingly, the present disclosure may be embodied in hardware and/or in software (including firmware, resident software, micro-code, etc.). In other words, embodiments of the present disclosure may take the form of a computer program product on a computer-usable or computer-readable storage medium having computer-usable or computer-readable program code embodied in the medium for use by or in connection with an instruction execution system. A computer-usable or computer-readable medium may be any medium that can contain, store, communicate, propagate, or transport the program for use by or in connection with the instruction execution system, apparatus, or device. 
     The computer-usable or computer-readable medium may be, for example but not limited to, an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, device, or propagation medium. More specific computer-readable medium examples (a non-exhaustive list), the computer-readable medium may include the following: an electrical connection having one or more wires, a portable computer diskette, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or Flash memory), an optical fiber, and a portable compact disc read-only memory (CD-ROM). Note that the computer-usable or computer-readable medium could even be paper or another suitable medium upon which the program is printed, as the program can be electronically captured, via, for instance, optical scanning of the paper or other medium, then compiled, interpreted, or otherwise processed in a suitable manner, if necessary, and then stored in a computer memory. 
     Embodiments of the present disclosure, for example, are described above with reference to block diagrams and/or operational illustrations of methods, systems, and computer program products according to embodiments of the disclosure. The functions/acts noted in the blocks may occur out of the order as shown in any flowchart. For example, two blocks shown in succession may in fact be executed substantially concurrently or the blocks may sometimes be executed in the reverse order, depending upon the functionality/acts involved. 
     While certain embodiments of the disclosure have been described, other embodiments may exist. Furthermore, although embodiments of the present disclosure have been described as being associated with data stored in memory and other storage mediums, data can also be stored on or read from other types of computer-readable media, such as secondary storage devices, like hard disks, floppy disks, or a CD-ROM, a carrier wave from the Internet, or other forms of RAM or ROM. Further, the disclosed methods&#39; stages may be modified in any manner, including by reordering stages and/or inserting or deleting stages, without departing from the disclosure. 
     While the specification includes examples, the disclosure&#39;s scope is indicated by the following claims. Furthermore, while the specification has been described in language specific to structural features and/or methodological acts, the claims are not limited to the features or acts described above. Rather, the specific features and acts described above are disclosed as example for embodiments of the disclosure.