Patent ID: 12192086

The figures are not exhaustive and do not limit the present disclosure to the precise form disclosed.

DETAILED DESCRIPTION

As described above, a liaison VRF acts as a liaison between external networks and an EVPN by publishing learned external routes to internal EVPN devices (e.g. Vteps). This internal publishing forms tunnels between the liaison VRF and the other EVPN devices which can be used by an OAM ping mechanism to reach the liaison VRF. However, when an EVPN is newly provisioned, communication with external networks may not commence immediately. Accordingly, the liaison VRF may not have external routes to publish, and thus may not have formed tunnels with other EVPN devices.

In this scenario, existing OAM ping mechanisms which rely on overlay tunnels to reach a liaison VRF cannot be utilized to validate the liaison VRF. Because IP addresses are generally not configured onto liaison VRFs, other common TLVs/OAM ping mechanisms (which utilize IP addresses to perform reachability checks) cannot be used to reach the liaison VRF either. Accordingly, a network administrator who wants to validate the reachability of a liaison VRF while provisioning a new EVPN cannot use existing TLVs/OAM ping mechanisms.

To address this problem, examples of the presently disclosed technology provide a new type of TLV (i.e. an EVPN Instance Identifier (EVI) TLV) which can be encapsulated in an OAM ping packet. This EVI TLV OAM ping packet can be sent to a network device (e.g., a border router) that a liaison VRF is provisioned on (unlike the liaison VRF, the border router will have an IP address, and thus can be reached using current OAM ping mechanisms). Upon receipt, the encapsulated EVI TLV instructs the network device to determine whether the configuration of the liaison VRF is mapped to an EVI value specified by the EVI TLV. If the configuration of the liaison VRF is mapped to the specified EVI value, the network device returns an echo response indicating that the configuration of the liaison VRF is mapped onto the specified EVI value. Such a response indicates that the liaison VRF is reachable for the EVPN (as described above, the EVPN is identified by the EVI value). In other words, if a liaison VRF is mapped to the EVI value, that means that the liaison VRF is enabled for publishing/receiving/hosting routes within the EVPN.

By leveraging typical mapping of a liaison VRF to an EVI value for an EVPN (e.g., a Virtual Network Identifier (VNI) for Vxlan EVPN fabrics, or an MPLS label for MPLS EVPN fabrics), examples of the presently disclosed technology can perform OAM ping validations on liaison VRFs before the liaison VRF has formed tunnels with other EVPN devices. Existing OAM ping technologies cannot do this. As examples of the presently disclosed technology appreciate, being able to perform OAM ping validations on liaison VRFs before they have formed tunnels with other EVPN devices can be advantageous when provisioning new EVPNs. In other words, it can be advantageous for a network administrator to validate a liaison VRF when provisioning an EVPN to ensure that the liaison VRF is properly configured and reachable before the EVPN is up and running. Examples perform this validation via modified OAM ping mechanisms because OAM pings validate both control plane (i.e., configuration of the liaison VRF) and data plane (i.e., reachability of the liaison VRF). Other validation checks, such as manually logging into the border router on which a liaison VRF is provisioned, may only validate the control plane.

FIG.1is an example conceptual diagram depicting an example EVPN fabric110, in accordance with various examples of the presently disclosed technology.

EVPN fabric110comprises a control plane112and a data plane114.

Control plane112may be a conceptual plane of EVPN fabric110that controls how data packets are forwarded within EVPN fabric110. In other words, control plane110may comprise the functions and processes involved for determining data packet routes within EVPN fabric110. Control plane112may use various protocols to determine data packet routes. Examples of these protocols may include MP-BGP, BGP-EVPN, BGP-L3VPN, etc. As described above, a control plane validation of a liaison VRF may comprise validating the configuration of the liaison VRF.

Data plane114may be a conceptual plane of EVPN fabric110that actually forwards data packets. In other words, data plane114may comprise the functions and processes that actually route data packets within EVPN fabric110(for basic analogy, if control plane112is the brain of EVPN110, data plane114is the hands and feet). Data plane114may utilize various protocols to route packets within EVPN fabric110. For example, if EVPN fabric110is a Vxlan fabric, data plane114may utilize Vxlan-based protocols. By the same token, if EVPN fabric110is an MPLS fabric, data plane may utilize MPLS-based protocols. As described above, a data plane validation of a liaison VRF may comprise validating the reachability of the liaison VRF

OAM ping mechanisms are well-suited for troubleshooting a network device/component like a liaison VRF because they can perform both a control plane and a data plane validation at the same time.

Data Plane Validation: OAM pings can be sent as echo request datagrams (i.e., OAM ping packets) over the same routes as a data packet would be sent. Accordingly, by reaching a liaison VRF and returning an echo response, an OAM ping can validate the data plane for an EVPN visa-vie the liaison VRF. In other words, the OAM ping validates the reachability of the liaison VRF.

Control Plane Validation: An OAM ping may perform a control plane validation for a liaison VRF as well. In other words, the OAM ping may validate the configuration of the liaison VRF and confirm that it is operational within the EVPN (i.e., enabled for publishing/hosting/receiving routes to and from other nodes of the EVPN). As alluded to above, the OAM ping may achieve these validations/confirmations by encapsulating TLVs within an OAM ping packet. These encapsulated TLVs may instruct the network device on which the liaison VRF is provisioned to validate the configuration of the VRF and/or confirm that the liaison VRF is operational/reachable.

FIG.2is an example diagram depicting an example EVPN fabric210, in accordance with various examples of the presently disclosed technology.

EVPN fabric210may be any type of EVPN fabric (e.g., MPLS, Vxlan, Mac-in-Mac, etc.). As depicted, EVPN fabric210contains network devices214and216and border router212. In various examples, EVPN fabric210may include a different number of network devices.

Network devices214and216may be various types of network devices (e.g., switches, routers, gateways, etc.). If EVPN fabric210comprises a Vxlan fabric, network devices214and216may comprise Vxlan Tunnel Endpoints (Vteps). These Vteps may be hardware-based or software-based.

Border router212may be a router deployed at the edge of EVPN fabric210. Provisioned on border router212is liaison VRF212a(in various examples, border router212may provision non-liaison VRFs as well). Liaison VRF212amay be a virtual routing and forwarding instance. As described above, liaison VRF212amay act as a “liaison” between EVPN fabric210and other networks (e.g., external networks220) by publishing learned external routes to internal EVPN devices (e.g., network devices214and216). In various examples, liaison VRF212amay be the sole VRF in EVPN fabric210responsible for storing/publishing learned external routes.

As depicted, EVPN fabric210communicates with external networks220(here external networks220may comprise one or more networks external to EVPN fabric210). In its role as “liaison,” liaison VRF212amay publish routes learned from external networks220to other network devices within EVPN fabric210. To publish these external routes, liaison VRF212amay form virtual overlay (i.e., layer2) tunnels with other network devices. Accordingly, in the example ofFIG.2, liaison VRF212ahas formed overlay tunnels to network devices214and216respectively.

Via these overlay tunnels, data packets may be routed/forwarded within EVPN fabric210. As will be described below, to validate the data plane of EVPN fabric210, OAM management device218may send OAM ping packets over the tunnels/overlay network of EVPN fabric210.

OAM management device218may be a device (hardware or software) which generates OAM ping packets. As depicted, OAM management device218is external to EVPN fabric210. However, in various examples OAM management device218may be a device within EVPN fabric210.

As described above, utilizing existing OAM ping mechanisms, OAM management device218may send an OAM ping packet to validate a network device (e.g., network devices214and216, or border router212) using an IP address of the network device. Liaison VRFs such as liaison VRF212atypically lack IP addresses (in other words, because of their limited “liaison” roles, liaison VRFs are not typically provisioned with layer 3 interfaces). Thus, in order to “reach” liaison VRF212ausing existing OAM ping mechanisms, OAM management device218must utilize the overlay tunnel network of EVPN fabric210. In this way, OAM management device218may validate the data plane of EVPN fabric210visa-a-vie liaison VRF212a.

In the example ofFIG.2, OAM management device218can send OAM ping packets to liaison VRF212abecause liaison VRF212ahas formed tunnels with other network devices within EVPN fabric210. In other words, because liaison VRF212ais a connected node within the overlay tunnel network of EVPN fabric210, OAM pings sent via this overlay tunnel network may reach liaison VRF212a(here OAM ping packets may be sent to e.g., network device214initially as network device214has an IP address/layer 3 interface).

However, it may not always be the case that a liaison VRF is a connected node of a tunnel network overlaying an EVPN fabric. For example, a newly provisioned EVPN may not have commenced communication with external networks. Accordingly, the liaison VRF of the EVPN may not have published learned external routes internally, and by extension, may not have formed overlay tunnels with other network devices within the EVPN. Accordingly, OAM ping packets sent via the overlay tunnel network of the EVPN will not reach the liaison VRF. This scenario will be described further in conjunction withFIG.3.

FIG.3is an example diagram depicting an example EVPN fabric310, in accordance with various examples of the presently disclosed technology. As depicted, EVPN fabric310contains network devices314and316and border router312. Provisioned on border router312is liaison VRF312a. Here, EVPN fabric310and its constituent components may be defined similarly to their corresponding components described in conjunction withFIG.2.

A key distinction betweenFIG.2andFIG.3is that inFIG.3, liaison VRF312ahas not formed overlay tunnels with other network devices within EVPN fabric310. As described above, this may be because EVPN fabric310is being provisioned (or has only recently been provisioned), and thus has not commenced communication with external networks320.

Because liaison VRF312ahas not formed tunnels with other network devices (e.g., network devices314and316), OAM management device318cannot utilize the overlay tunnel network of EVPN fabric310to reach/ping liaison VRF312a. Moreover, because liaison VRF312alacks an IP address/layer 3 interface, OAM management device318cannot utilize other existing OAM ping mechanisms to validate liaison VRF312a.

To address this problem, examples of the presently disclosed technology provide a new type-length-value data stream (TLV) which can be encapsulated by existing OAM ping mechanisms to validate a liaison VRF when the liaison VRF cannot be reached via a EVPN's overlay tunnel network. In particular, examples provide an EVPN Instance Identifier (EVI) TLV such as the example EVI TLV depicted below.

As depicted, the EVI TLV may comprise a type field, a length field, and a value field (i.e. the EVI Identifier field).

The type field of the EVI TLV may comprise one octet and may describe the type/kind of message being conveyed by the EVI TLV, and may depend on the type of EVPN fabric.

The length field of the EVI TLV may define the length of the value field. For example, if the EVI Identifier in the value field comprises four octets, the corresponding length field may carry “4” as the length.

The value field of the EVI TLV may comprise an EVI identifier value. This EVI identifier value may vary depending on EVPN fabric310's type. For example, if EVPN fabric310is a Vxlan fabric, the EVI identifier value may comprise a Virtual Network Identifier (VNI) value for EVPN310. By contrast, if EVPN fabric310is an MPLS-based fabric, the EVI identifier value may comprise an MPLS label for EVPN fabric310.

As examples of the presently disclosed technology appreciate, while a liaison VRF may not have an IP address/layer 3 interface, the liaison VRF will often be mapped to the EVI identifier for an EVPN. This is because the liaison VRF must be mapped to the EVI identifier in order to publish routes within the EVPN. Accordingly, examples of the presently disclosed technology may validate the configuration and reachability of a liaison VRF by confirming that it is mapped to the EVI identifier for an EVPN.

In particular, OAM management device318can send an OAM ping packet to border router312which encapsulates an EVI TLV such as the one illustrated above. This OAM ping command may utilize the IP address of border router312(e.g., 101.1.1.1) to reach border router312. An example OAM ping packet command designed to validate whether liaison VRF312ais mapped to example EVI identifier100is illustrated below.Aruba-cx-vtysh## Path trace 101.1.1.1100[Command Syntax: Pathtrace <border router 312 IP><EVI>]

Upon receiving such an OAM ping packet, border router312may determine whether a configuration of liaison VRF312ais mapped onto EVI identifier100. If border router312determines that the configuration of liaison VRF312ais mapped onto EVI identifier100, border router312may respond with an echo response indicating as such. If border router312determines that the configuration of liaison VRF312ais not mapped onto EVI identifier100, border router312may drop the OAM ping packet, or provide an echo response with an error message.

When OAM management device318receives an echo response indicating that liaison VRF312ais mapped onto EVI identifier100, OAM management device may confirm that liaison VRF312ais properly configured and reachable. In other words, OAM management device may confirm that liaison VRF312ais up and working.

By contrast, if OAM management device318does not receive an echo response or receives an echo response indicating that liaison VRF312ais not mapped onto EVI identifier100, OAM management device318may confirm that liaison VRF312ais not reachable and/or not properly configured. In other words, OAM management device318may confirm that liaison VRF312ais not up and working. As described above, such information can be valuable to a network administrator when provisioning an EVPN such as EVPN fabric310.

FIG.4depicts an example computing system400that may be used to validate the configuration and reachability of a liaison VRF in a VPN, in accordance with various examples. Referring now toFIG.4, computing component410may be, for example, a server computer, a controller, or any other similar computing component capable of processing data. In the example implementation ofFIG.4, the computing component410includes a hardware processor412, and machine-readable storage medium for414. In various examples, example computing system400may be implemented on a device in the VPN.

Hardware processor412may be one or more central processing units (CPUs), semiconductor-based microprocessors, and/or other hardware devices suitable for retrieval and execution of instructions stored in machine-readable storage medium414. Hardware processor412may fetch, decode, and execute instructions, such as instructions416-420, to control processes or operations for burst preloading for available bandwidth estimation. As an alternative or in addition to retrieving and executing instructions, hardware processor412may include one or more electronic circuits that include electronic components for performing the functionality of one or more instructions, such as a field programmable gate array (FPGA), application specific integrated circuit (ASIC), or other electronic circuits.

A machine-readable storage medium, such as machine-readable storage medium414, may be any electronic, magnetic, optical, or other physical storage device that contains or stores executable instructions. Thus, machine-readable storage medium414may be, for example, Random Access Memory (RAM), non-volatile RAM (NVRAM), an Electrically Erasable Programmable Read-Only Memory (EEPROM), a storage device, an optical disc, and the like. In some examples, machine-readable storage medium414may be a non-transitory storage medium, where the term “non-transitory” does not encompass transitory propagating signals. As described in detail below, machine-readable storage medium414may be encoded with executable instructions, for example, instructions416-420.

As described above, computing system400may be used to validate the configuration and reachability of a liaison VRF in a VPN. Accordingly, hardware processor412may execute instruction416to send to an OAM ping packet to a device in the VPN. Here, the liaison VRF may be provisioned on the device. In certain examples, the device may comprise a border device such as a border router, border switch, border gateway, etc. In various examples, the VPN may be an EVPN.

The liaison VRF may function to publish learned external routes to other devices within the VPN (these “other devices within the VPN” may comprise various types of devices, both hardware-based and software-based). In other words, the liaison VRF may act as a liaison between external networks and devices within the VPN. In its role as liaison, the liaison VRF may store learned external routes, and publish them to other devices within the VPN. In doing so, the liaison VRF may form overlay tunnels with other devices within the VPN. However, as described above, in some instances the liaison VRF may not have published any routes to other devices within the VPN. This may be the case where the VPN is newly provisioned, and has not yet commenced communication with external networks. In these scenarios, the liaison VRF may not have formed overlay tunnels with other devices within the VPN. Accordingly, the liaison VRF may be unreachable using existing OAM ping mechanisms.

To address this scenario, hardware processor412may encapsulate a VPN instance identifier (EVI) time-length-value data stream (TLV) (collectively an EVI TLV) in the OAM ping packet sent to the device (as described above, hardware processor412may be able to send the OAM ping packet to the device because unlike the liaison VRF, the device may have an IP address). As described above, this EVI TLV may specify an EVI value identifying the VPN. Where the VPN comprises a Vxlan data plane, the EVI value may by a VNI associated with the Vxlan data plane. When the VPN comprises an MPLS-based data plane, the EVI value may comprise an identifying label associated with the MPLS-based data plane.

As described above, upon receipt of the OAM ping packet encapsulating the EVI TLV, the device may determine whether a configuration of the liaison VRF is mapped to the EVI value specified in the EVI TLV. If the device determines that the configuration of the liaison VRF is mapped to the EVI value specified in the EVI TLV, the device may send an echo response indicating as such.

Accordingly, hardware processor412may execute instruction418to receive, from the device, a response to the OAM packet indicating that the configuration of the liaison VRF is mapped to the EVI value specified in the EVI TLV.

Hardware processor412may execute instruction420to determine that the liaison VRF is reachable within the VPN. As described above, hardware processor412may determine that the liaison VRF is reachable within the VPN simply by receiving the echo response indicating that the configuration of the liaison VRF is mapped to the EVI value specified in the EVI TLV.

FIG.5depicts another example computing system500that may be used to validate the configuration and reachability of a liaison VRF in an EVPN, in accordance with various examples. Referring now toFIG.5, computing component510may be, for example, a server computer, a controller, or any other similar computing component capable of processing data. In the example implementation ofFIG.5, the computing component510includes a hardware processor512, and machine-readable storage medium for514. Here, computing system500is implemented on a first device within the EVPN. The liaison VRF is provisioned on this first device.

Hardware processor512and machine-readable storage medium514may be the same/similar as hardware processor412and machine-readable storage medium414respectively. Accordingly, machine-readable storage medium514may be encoded with executable instructions, for example, instructions516-520.

Hardware processor512may execute instruction516to receive an OAM ping packet. As described in conjunction withFIG.4, the OAM ping packet may encapsulate an EVI TLV. This EVI TLV may specify an EVI value associated with the EVPN. The EVI TLV and EVI value may be the same/similar as described in conjunction withFIG.4.

As described above, hardware processor512is implemented on a first device within the EVPN. The liaison VRF is provisioned on this first device (here the liaison VRF may be the same/similar as described in conjunction withFIG.4). In various examples, the first device may be a border device of the EVPN, such as a border router, a border switch, a border gateway, etc.

In various example, hardware processor512may receive the OAM ping packet from a second device within the EVPN. This second device may be hardware-based or software-based. The second device may send the OAM ping packet to the first device using any of the methods described in conjunction with the previous figures.

Hardware processor512may execute instruction518to determine that a configuration of the liaison VRF is mapped onto the EVI value specified in the EVI TLV. As described above, this may indicate that the liaison VRF is reachable within the EVPN. In other words, this may indicate that the liaison VRF is enabled for publishing/receiving/hosting routes within the EVPN.

Hardware processor512may execute instruction518to send a response to the OAM ping packet indicating that the configuration of the liaison VRF is mapped to the EVI value specified in the EVI TLV. In certain examples, this response may comprise an echo response to the OAM ping packet. The response may be received by the second device (i.e., the device which initially sent the OAM ping packet to the first device). In various examples, the response to the OAM ping packet may also indicate that the liaison VRF is reachable within the EVPN.

FIG.6depicts a block diagram of an example computer system600in which various of the embodiments described herein may be implemented. The computer system600includes a bus602or other communication mechanism for communicating information, one or more hardware processors604coupled with bus602for processing information. Hardware processor(s)604may be, for example, one or more general purpose microprocessors.

The computer system600also includes a main memory606, such as a random-access memory (RAM), cache and/or other dynamic storage devices, coupled to bus602for storing information and instructions to be executed by processor604. Main memory606also may be used for storing temporary variables or other intermediate information during execution of instructions to be executed by processor604. Such instructions, when stored in storage media accessible to processor604, render computer system600into a special-purpose machine that is customized to perform the operations specified in the instructions.

The computer system600further includes a read only memory (ROM)608or other static storage device coupled to bus602for storing static information and instructions for processor604. A storage device610, such as a magnetic disk, optical disk, or USB thumb drive (Flash drive), etc., is provided and coupled to bus602for storing information and instructions.

The computer system600may be coupled via bus602to a display612, such as a liquid crystal display (LCD) (or touch screen), for displaying information to a computer user. An input device614, including alphanumeric and other keys, is coupled to bus602for communicating information and command selections to processor604. Another type of user input device is cursor control616, such as a mouse, a trackball, or cursor direction keys for communicating direction information and command selections to processor604and for controlling cursor movement on display612. In some embodiments, the same direction information and command selections as cursor control may be implemented via receiving touches on a touch screen without a cursor.

The computing system600may include a user interface module to implement a GUI that may be stored in a mass storage device as executable software codes that are executed by the computing device(s). This and other modules may include, by way of example, components, such as software components, object-oriented software components, class components and task components, processes, functions, attributes, procedures, subroutines, segments of program code, drivers, firmware, microcode, circuitry, data, databases, data structures, tables, arrays, and variables.

In general, the word “component,” “engine,” “system,” “database,” data store,” and the like, as used herein, can refer to logic embodied in hardware or firmware, or to a collection of software instructions, possibly having entry and exit points, written in a programming language, such as, for example, Java, C or C++. A software component may be compiled and linked into an executable program, installed in a dynamic link library, or may be written in an interpreted programming language such as, for example, BASIC, Perl, or Python. It will be appreciated that software components may be callable from other components or from themselves, and/or may be invoked in response to detected events or interrupts. Software components configured for execution on computing devices may be provided on a computer readable medium, such as a compact disc, digital video disc, flash drive, magnetic disc, or any other tangible medium, or as a digital download (and may be originally stored in a compressed or installable format that requires installation, decompression, or decryption prior to execution). Such software code may be stored, partially or fully, on a memory device of the executing computing device, for execution by the computing device. Software instructions may be embedded in firmware, such as an EPROM. It will be further appreciated that hardware components may be comprised of connected logic units, such as gates and flip-flops, and/or may be comprised of programmable units, such as programmable gate arrays or processors.

The computer system600may implement the techniques described herein using customized hard-wired logic, one or more ASICs or FPGAs, firmware and/or program logic which in combination with the computer system causes or programs computer system600to be a special-purpose machine. According to one embodiment, the techniques herein are performed by computer system600in response to processor(s)604executing one or more sequences of one or more instructions contained in main memory606. Such instructions may be read into main memory606from another storage medium, such as storage device610. Execution of the sequences of instructions contained in main memory606causes processor(s)604to perform the process steps described herein. In alternative embodiments, hard-wired circuitry may be used in place of or in combination with software instructions.

The term “non-transitory media,” and similar terms, as used herein refers to any media that store data and/or instructions that cause a machine to operate in a specific fashion. Such non-transitory media may comprise non-volatile media and/or volatile media. Non-volatile media includes, for example, optical or magnetic disks, such as storage device610. Volatile media includes dynamic memory, such as main memory606. Common forms of non-transitory media include, for example, a floppy disk, a flexible disk, hard disk, solid state drive, magnetic tape, or any other magnetic data storage medium, a CD-ROM, any other optical data storage medium, any physical medium with patterns of holes, a RAM, a PROM, and EPROM, a FLASH-EPROM, NVRAM, any other memory chip or cartridge, and networked versions of the same.

Non-transitory media is distinct from but may be used in conjunction with transmission media. Transmission media participates in transferring information between non-transitory media. For example, transmission media includes coaxial cables, copper wire and fiber optics, including the wires that comprise bus602. Transmission media can also take the form of acoustic or light waves, such as those generated during radio-wave and infra-red data communications.

The computer system600also includes a communication interface618coupled to bus602. Network interface618provides a two-way data communication coupling to one or more network links that are connected to one or more local networks. For example, communication interface618may be an integrated services digital network (ISDN) card, cable modem, satellite modem, or a modem to provide a data communication connection to a corresponding type of telephone line. As another example, network interface618may be a local area network (LAN) card to provide a data communication connection to a compatible LAN (or WAN component to communicated with a WAN). Wireless links may also be implemented. In any such implementation, network interface618sends and receives electrical, electromagnetic, or optical signals that carry digital data streams representing various types of information.

A network link typically provides data communication through one or more networks to other data devices. For example, a network link may provide a connection through local network to an edge computer or to data equipment operated by an Internet Service Provider (ISP). The ISP in turn provides data communication services through the worldwide packet data communication network now commonly referred to as the “Internet.” Local network and Internet both use electrical, electromagnetic, or optical signals that carry digital data streams. The signals through the various networks and the signals on network link and through communication interface618, which carry the digital data to and from computer system600, are example forms of transmission media.

The computer system600can send messages and receive data, including program code, through the network(s), network link and communication interface618. In the Internet example, a server might transmit a requested code for an application program through the Internet, the ISP, the local network, and the communication interface618.

The received code may be executed by processor604as it is received, and/or stored in storage device610, or other non-volatile storage for later execution.

Each of the processes, methods, and algorithms described in the preceding sections may be embodied in, and fully or partially automated by, code components executed by one or more computer systems or computer processors comprising computer hardware. The one or more computer systems or computer processors may also operate to support performance of the relevant operations in a “cloud computing” environment or as a “software as a service” (SaaS). The processes and algorithms may be implemented partially or wholly in application-specific circuitry. The various features and processes described above may be used independently of one another, or may be combined in various ways. Different combinations and sub-combinations are intended to fall within the scope of this disclosure, and certain method or process blocks may be omitted in some implementations. The methods and processes described herein are also not limited to any particular sequence, and the blocks or states relating thereto can be performed in other sequences that are appropriate, or may be performed in parallel, or in some other manner. Blocks or states may be added to or removed from the disclosed example embodiments. The performance of certain of the operations or processes may be distributed among computer systems or computers processors, not only residing within a single machine, but deployed across a number of machines.

As used herein, a circuit might be implemented utilizing any form of hardware, software, or a combination thereof. For example, one or more processors, controllers, ASICs, PLAs, PALs, CPLDs, FPGAs, logical components, software routines or other mechanisms might be implemented to make up a circuit. In implementation, the various circuits described herein might be implemented as discrete circuits or the functions and features described can be shared in part or in total among one or more circuits. Even though various features or elements of functionality may be individually described or claimed as separate circuits, these features and functionality can be shared among one or more common circuits, and such description shall not require or imply that separate circuits are required to implement such features or functionality. Where a circuit is implemented in whole or in part using software, such software can be implemented to operate with a computing or processing system capable of carrying out the functionality described with respect thereto, such as computer system600.

As used herein, the term “or” may be construed in either an inclusive or exclusive sense. Moreover, the description of resources, operations, or structures in the singular shall not be read to exclude the plural. Conditional language, such as, among others, “can,” “could,” “might,” or “may,” unless specifically stated otherwise, or otherwise understood within the context as used, is generally intended to convey that certain embodiments include, while other embodiments do not include, certain features, elements and/or steps.

Terms and phrases used in this document, and variations thereof, unless otherwise expressly stated, should be construed as open ended as opposed to limiting. Adjectives such as “conventional,” “traditional,” “normal,” “standard,” “known,” and terms of similar meaning should not be construed as limiting the item described to a given time period or to an item available as of a given time, but instead should be read to encompass conventional, traditional, normal, or standard technologies that may be available or known now or at any time in the future. The presence of broadening words and phrases such as “one or more,” “at least,” “but not limited to” or other like phrases in some instances shall not be read to mean that the narrower case is intended or required in instances where such broadening phrases may be absent.

It should be noted that the terms “optimize,” “optimal” and the like as used herein can be used to mean making or achieving performance as effective or perfect as possible. However, as one of ordinary skill in the art reading this document will recognize, perfection cannot always be achieved. Accordingly, these terms can also encompass making or achieving performance as good or effective as possible or practical under the given circumstances, or making or achieving performance better than that which can be achieved with other settings or parameters.