Abstract:
A security appliance to perform a method that includes receiving a first set of data from a first device using a first secure protocol of a first network, the first secure protocol comprises a first level of security, and determining, by the security appliance, that the received first set of data is intended for a second device on a second network using a second secure protocol, the second secure protocol comprises a second level of security different from the first. The method includes authenticating, by the security appliance, the received first set of data from the first network using the first secure protocol for transmission through the second network using the second secure protocol while collecting and concentrating additional data from the first network and transmitting, by the security appliance, the received first set of data to the second device via the second network comprising the second secure protocol.

Description:
TECHNICAL FIELD 
       [0001]    This disclosure is generally directed to a security appliance. More specifically, this disclosure is directed to a security appliance with IEC 61131-3 for use in an industrial process control and automation system. 
       BACKGROUND 
       [0002]    The ability to integrate subsystem devices that communicate using a variety of legacy protocols into a modern secure Ethernet network requires the use of different devices (such as protocol converters, gateways, firewalls, and dedicated security appliances). Each such device typically serves a single function or supports a single protocol, is typically sourced from different vendors and uses different configuration tools that are at a high risk of exposure to a security attack, and does not have a programming environment that would allow an end user to customize the behavior of the device. 
       SUMMARY 
       [0003]    This disclosure relates to an apparatus and method for using a security appliance in a process control system. 
         [0004]    In a first embodiment, a method is provided. The method includes receiving, by a security appliance, a first set of data from a first device using a first secure protocol of a first network, wherein the first secure protocol comprises a first level of security. The method also includes determining, by the security appliance, that the received first set of data is intended for a second device on a second network using a second secure protocol, wherein the second secure protocol comprises a second level of security that is different from the first level of security. The method further includes authenticating, by the security appliance, the received first set of data from the first network using the first secure protocol for transmission through the second network using the second secure protocol while collecting and concentrating additional data from the first network. In addition, the method includes transmitting, by the security appliance, the received first set of data to the second device via the second network comprising the second secure protocol. 
         [0005]    In a second embodiment, a security appliance including processing circuitry is provided. The processing circuitry is configured to receive a first set of data from a first device using a first secure protocol of a first network, wherein the first secure protocol comprises a first level of security. The processing circuitry is also configured to determine that the received first set of data is intended for a second device on a second network using a second secure protocol, wherein the second secure protocol comprises a second level of security that is different from the first level of security. The processing circuitry is further configured to authenticate the received first set of data from the first network using the first secure protocol for transmission through the second network using the second secure protocol while collecting and concentrating additional data from the first network. In addition, the processing circuitry is configured to transmit the received first set of data to the second device via the second network comprising the second secure protocol. 
         [0006]    In a third embodiment, a non-transitory, computer-readable medium storing one or more executable instructions is provided. The one or more executable instructions, when executed by one or more processors, cause the one or more processors to receive a first set of data from a first device using a first secure protocol of a first network, wherein the first secure protocol comprises a first level of security. The one or more executable instructions, when executed by the one or more processors, also cause the one or more processors to determine that the received first set of data is intended for a second device on a second network using a second secure protocol, wherein the second secure protocol comprises a second level of security that is different from the first level of security. The one or more executable instructions, when executed by the one or more processors, further cause the one or more processors to authenticate the received first set of data from the first network using the first secure protocol for transmission through the second network using the second secure protocol while collecting and concentrating additional data from first network. In addition, the one or more executable instructions, when executed by the one or more processors, cause the one or more processors to transmit the received first set of data to the second device via the second network comprising the second secure protocol. 
         [0007]    Other technical features may be readily apparent to one skilled in the art from the following figures, descriptions, and claims. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]    For a more complete understanding of this disclosure, reference is now made to the following description, taken in conjunction with the accompanying drawings, in which: 
           [0009]      FIG. 1  illustrates an example industrial process control and automation system according to this disclosure; 
           [0010]      FIGS. 2 and 3  illustrate example details of a security appliance according to this disclosure; and 
           [0011]      FIGS. 4 and 5  illustrate example methods according to this disclosure. 
       
    
    
     DETAILED DESCRIPTION 
       [0012]    The figures discussed below and the various embodiments used to describe the principles of the present invention in this patent document are by way of illustration only and should not be construed in any way to limit the scope of the invention. Those skilled in the art will understand that the principles of the invention may be implemented in any type of suitably arranged device or system. 
         [0013]    The ability to integrate subsystem devices that communicate using a variety of legacy protocols into a modern secure Ethernet network requires the use of different devices (such as protocol converters, gateways, firewalls, and dedicated security appliances). Each such device typically serves a single function or supports a single protocol. Thus, a number of such devices have to be connected in series. These devices are typically sourced from different vendors and use different configuration tools, thereby increasing engineering complexity for the end user. In addition, legacy protocols are not designed with cybersecurity in mind, and the security exposure of the integrated system is high. The security appliances that exist in the market today also do not have programming environments that would allow the end user to customize the behavior of the appliance. This makes protocol conversion and other manipulation of data during transmission difficult on the same appliance. 
         [0014]      FIG. 1  illustrates an example industrial process control and automation system  100  according to this disclosure. As shown in  FIG. 1 , the system  100  includes various components that facilitate production or processing of at least one product or other material. For instance, the system  100  is used here to facilitate control over components in one or multiple plants  101   a - 101   n.  Each plant  101   a - 101   n  represents one or more processing facilities (or one or more portions thereof), such as one or more manufacturing facilities for producing at least one product or other material. In general, each plant  101   a - 101   n  may implement one or more processes and can individually or collectively be referred to as a process system. A process system generally represents any system or portion thereof configured to process one or more products or other materials in some manner. 
         [0015]    In  FIG. 1 , the system  100  is implemented using the Purdue model of process control. In the Purdue model, “Level 0” may include one or more sensors  102   a  and one or more actuators  102   b.  The sensors  102   a  and actuators  102   b  represent components in a process system that may perform any of a wide variety of functions. For example, the sensors  102   a  could measure a wide variety of characteristics in the process system, such as temperature, pressure, or flow rate. Also, the actuators  102   b  could alter a wide variety of characteristics in the process system. The sensors  102   a  and actuators  102   b  could represent any other or additional components in any suitable process system. Each of the sensors  102   a  includes any suitable structure for measuring one or more characteristics in a process system. Each of the actuators  102   b  includes any suitable structure for operating on or affecting one or more conditions in a process system. 
         [0016]    At least one network  104  is coupled to the sensors  102   a  and actuators  102   b.  The network  104  facilitates interaction with the sensors  102   a  and actuators  102   b.  For example, the network  104  could transport measurement data from the sensors  102   a  and provide control signals to the actuators  102   b.  The network  104  could represent any suitable network or combination of networks. As particular examples, the network  104  could represent an Ethernet network, an electrical signal network (such as a HART or FOUNDATION FIELDBUS network), a pneumatic control signal network, or any other or additional type(s) of network(s). 
         [0017]    In the Purdue model, “Level 1” may include one or more controllers  106 , which are coupled to the network  104 . Among other things, each controller  106  may use the measurements from one or more sensors  102   a  to control the operation of one or more actuators  102   b.  For example, a controller  106  could receive measurement data from one or more sensors  102   a  and use the measurement data to generate control signals for one or more actuators  102   b.  Each controller  106  includes any suitable structure for interacting with one or more sensors  102   a  and controlling one or more actuators  102   b.  Each controller  106  could, for example, represent a proportional-integral-derivative (PID) controller or a multivariable controller, such as a Robust Multivariable Predictive Control Technology (RMPCT) controller or other type of controller implementing model predictive control (MPC) or other advanced predictive control (APC). As a particular example, each controller  106  could represent a computing device running a real-time operating system. 
         [0018]    Two networks  108  are coupled to the controllers  106 . The networks  108  facilitate interaction with the controllers  106 , such as by transporting data to and from the controllers  106 . The networks  108  could represent any suitable networks or combination of networks. As a particular example, the networks  108  could represent a redundant pair of Ethernet networks, such as a FAULT TOLERANT ETHERNET (FTE) network from HONEYWELL INTERNATIONAL INC. 
         [0019]    In accordance with this disclosure, the system  100  also includes a security appliance  160 . The security appliance  160  integrates the network  104  (such as a potentially insecure legacy Ethernet or serial network) with a controller (such as controller  106 ) on a modern secure network  108 . For example, the security appliance  160  can include multiple Ethernet ports, and one or two Ethernet ports can be connected to the network  108  (the secure network) while other Ethernet ports (such as two Ethernet ports, two RS-232 ports, or two RS485 ports) can be connected to the network  104  (the legacy network) or directly to third party devices (such the controller  106 , the actuator  102   b,  the sensor  102   a,  or the like). 
         [0020]    In other words, the security appliance  160  isolates the network  108  and the from the network  104 . The security appliance  160  is configured, when deployed in read-only mode, to block all attempts by devices connected to the network  108  to write to devices (such as third party devices) connected to the network  104 . The security appliance  160  is also configured to provide security to devices connected to the networks while allowing validated protocol messages to be pass through the networks. The security appliance  160  can be configured by an end user to perform protocol conversion and other data manipulation using an embedded IEC 6111 environment. Features of the security appliance  160  are discussed further herein. 
         [0021]    At least one switch/firewall  110  couples the networks  108  to two networks  112 . The switch/firewall  110  may transport traffic from one network to another. The switch/firewall  110  may also block traffic on one network from reaching another network. The switch/firewall  110  includes any suitable structure for providing communication between networks, such as a HONEYWELL CONTROL FIREWALL (CF9) device. The networks  112  could represent any suitable networks, such as an FTE network. 
         [0022]    In the Purdue model, “Level 2” may include one or more machine-level controllers  114  coupled to the networks  112 . The machine-level controllers  114  perform various functions to support the operation and control of the controllers  106 , sensors  102   a,  and actuators  102   b,  which could be associated with a particular piece of industrial equipment (such as a boiler or other machine). For example, the machine-level controllers  114  could log information collected or generated by the controllers  106 , such as measurement data from the sensors  102   a  or control signals for the actuators  102   b.  The machine-level controllers  114  could also execute applications that control the operation of the controllers  106 , thereby controlling the operation of the actuators  102   b.  In addition, the machine-level controllers  114  could provide secure access to the controllers  106 . Each of the machine-level controllers  114  includes any suitable structure for providing access to, control of, or operations related to a machine or other individual piece of equipment. Each of the machine-level controllers  114  could, for example, represent a server computing device running a MICROSOFT WINDOWS operating system. Although not shown, different machine-level controllers  114  could be used to control different pieces of equipment in a process system (where each piece of equipment is associated with one or more controllers  106 , sensors  102   a,  and actuators  102   b ). 
         [0023]    One or more operator stations  116  are coupled to the networks  112 . The operator stations  116  represent computing or communication devices providing user access to the machine-level controllers  114 , which could then provide user access to the controllers  106  (and possibly the sensors  102   a  and actuators  102   b ). As particular examples, the operator stations  116  could allow users to review the operational history of the sensors  102   a  and actuators  102   b  using information collected by the controllers  106  and/or the machine-level controllers  114 . The operator stations  116  could also allow the users to adjust the operation of the sensors  102   a,  actuators  102   b,  controllers  106 , or machine-level controllers  114 . In addition, the operator stations  116  could receive and display warnings, alerts, or other messages or displays generated by the controllers  106  or the machine-level controllers  114 . Each of the operator stations  116  includes any suitable structure for supporting user access and control of one or more components in the system  100 . Each of the operator stations  116  could, for example, represent a computing device running a MICROSOFT WINDOWS operating system. 
         [0024]    At least one router/firewall  118  couples the networks  112  to two networks  120 . The router/firewall  118  includes any suitable structure for providing communication between networks, such as a secure router or combination router/firewall. The networks  120  could represent any suitable networks, such as an FTE network. 
         [0025]    In the Purdue model, “Level 3” may include one or more unit-level controllers  122  coupled to the networks  120 . Each unit-level controller  122  is typically associated with a unit in a process system, which represents a collection of different machines operating together to implement at least part of a process. The unit-level controllers  122  perform various functions to support the operation and control of components in the lower levels. For example, the unit-level controllers  122  could log information collected or generated by the components in the lower levels, execute applications that control the components in the lower levels, and provide secure access to the components in the lower levels. Each of the unit-level controllers  122  includes any suitable structure for providing access to, control of, or operations related to one or more machines or other pieces of equipment in a process unit. Each of the unit-level controllers  122  could, for example, represent a server computing device running a MICROSOFT WINDOWS operating system. Although not shown, different unit-level controllers  122  could be used to control different units in a process system (where each unit is associated with one or more machine-level controllers  114 , controllers  106 , sensors  102   a,  and actuators  102   b ). 
         [0026]    Access to the unit-level controllers  122  may be provided by one or more operator stations  124 . Each of the operator stations  124  includes any suitable structure for supporting user access and control of one or more components in the system  100 . Each of the operator stations  124  could, for example, represent a computing device running a MICROSOFT WINDOWS operating system. 
         [0027]    At least one router/firewall  126  couples the networks  120  to two networks  128 . The router/firewall  126  includes any suitable structure for providing communication between networks, such as a secure router or combination router/firewall. The networks  128  could represent any suitable networks, such as an FTE network. 
         [0028]    In the Purdue model, “Level 4” may include one or more plant-level controllers  130  coupled to the networks  128 . Each plant-level controller  130  is typically associated with one of the plants  101   a - 101   n,  which may include one or more process units that implement the same, similar, or different processes. The plant-level controllers  130  perform various functions to support the operation and control of components in the lower levels. As particular examples, the plant-level controller  130  could execute one or more manufacturing execution system (MES) applications, scheduling applications, or other or additional plant or process control applications. Each of the plant-level controllers  130  includes any suitable structure for providing access to, control of, or operations related to one or more process units in a process plant. Each of the plant-level controllers  130  could, for example, represent a server computing device running a MICROSOFT WINDOWS operating system. 
         [0029]    Access to the plant-level controllers  130  may be provided by one or more operator stations  132 . Each of the operator stations  132  includes any suitable structure for supporting user access and control of one or more components in the system  100 . Each of the operator stations  132  could, for example, represent a computing device running a MICROSOFT WINDOWS operating system. 
         [0030]    At least one router/firewall  134  couples the networks  128  to one or more networks  136 . The router/firewall  134  includes any suitable structure for providing communication between networks, such as a secure router or combination router/firewall. The network  136  could represent any suitable network, such as an enterprise-wide Ethernet or other network or all or a portion of a larger network (such as the Internet). 
         [0031]    In the Purdue model, “Level 5” may include one or more enterprise-level controllers  138  coupled to the network  136 . Each enterprise-level controller  138  is typically able to perform planning operations for multiple plants  101   a - 101   n  and to control various aspects of the plants  101   a - 101   n.  The enterprise-level controllers  138  can also perform various functions to support the operation and control of components in the plants  101   a - 101   n.  As particular examples, the enterprise-level controller  138  could execute one or more order processing applications, enterprise resource planning (ERP) applications, advanced planning and scheduling (APS) applications, or any other or additional enterprise control applications. Each of the enterprise-level controllers  138  includes any suitable structure for providing access to, control of, or operations related to the control of one or more plants. Each of the enterprise-level controllers  138  could, for example, represent a server computing device running a MICROSOFT WINDOWS operating system. In this document, the term “enterprise” refers to an organization having one or more plants or other processing facilities to be managed. Note that if a single plant  101   a  is to be managed, the functionality of the enterprise-level controller  138  could be incorporated into the plant-level controller  130 . 
         [0032]    Access to the enterprise-level controllers  138  may be provided by one or more operator stations  140 . Each of the operator stations  140  includes any suitable structure for supporting user access and control of one or more components in the system  100 . Each of the operator stations  140  could, for example, represent a computing device running a MICROSOFT WINDOWS operating system. 
         [0033]    Various levels of the Purdue model can include other components, such as one or more databases. The database(s) associated with each level could store any suitable information associated with that level or one or more other levels of the system  100 . For example, a historian  141  can be coupled to the network  136 . The historian  141  could represent a component that stores various information about the system  100 . The historian  141  could, for instance, store information used during production scheduling and optimization. The historian  141  represents any suitable structure for storing and facilitating retrieval of information. Although shown as a single centralized component coupled to the network  136 , the historian  141  could be located elsewhere in the system  100 , or multiple historians could be distributed in different locations in the system  100 . 
         [0034]    In particular embodiments, the various controllers and operator stations in  FIG. 1  may represent computing devices. For example, each of the controllers  106 ,  114 ,  122 ,  130 ,  138  could include one or more processing devices  142  and one or more memories  144  for storing instructions and data used, generated, or collected by the processing device(s)  142 . Each of the controllers  106 ,  114 ,  122 ,  130 ,  138  could also include at least one network interface  146 , such as one or more Ethernet interfaces or wireless transceivers. Also, each of the operator stations  116 ,  124 ,  132 , and  140  could include one or more processing devices  148  and one or more memories  150  for storing instructions and data used, generated, or collected by the processing device(s)  148 . Each of the operator stations  116 ,  124 ,  132 , and  140  could also include at least one network interface  152 , such as one or more Ethernet interfaces or wireless transceivers. 
         [0035]    Although  FIG. 1  illustrates one example of an industrial process control and automation system  100 , various changes may be made to  FIG. 1 . For example, a control and automation system could include any number of sensors, actuators, controllers, servers, operator stations, networks, risk managers, and other components. Also, the makeup and arrangement of the system  100  in  FIG. 1  is for illustration only. Components could be added, omitted, combined, or placed in any other suitable configuration according to particular needs. For example, while the industrial process control and automation system  100  can be based on the Purdue model, the security appliance  160  can be implemented to link between a secure and less secure network. Further, particular functions have been described as being performed by particular components of the system  100 . This is for illustration only. In general, control and automation systems are highly configurable and can be configured in any suitable manner according to particular needs. 
         [0036]      FIG. 2  illustrates an example configuration of the security appliance  160  according to this disclosure. As shown in  FIG. 2 , the security appliance  160  includes a bus system  205 , which supports communication between at least one processing device  210 , at least one storage device  215 , at least one communications unit  220 , and at least one input/output (I/O) unit  225 . 
         [0037]    The processing device  210  executes instructions that may be loaded into a memory  230 . The processing device  210  may include any suitable number(s) and type(s) of processors or other devices in any suitable arrangement. Example types of processing devices  210  include microprocessors, microcontrollers, digital signal processors, field programmable gate arrays, application specific integrated circuits, and discreet circuitry. 
         [0038]    The memory  230  and a persistent storage  235  are examples of storage devices  215 , which represent any structure(s) capable of storing and facilitating retrieval of information (such as data, program code, and/or other suitable information on a temporary or permanent basis). The memory  230  may represent a random access memory or any other suitable volatile or non-volatile storage device(s). The persistent storage  235  may contain one or more components or devices supporting longer-term storage of data, such as a ready only memory, hard drive, Flash memory, or optical disc. 
         [0039]    The communications unit  220  supports communications with other systems or devices. For example, the communications unit  220  could include a network interface card or a wireless transceiver facilitating communications over the network  136 . The communications unit  220  may support communications through any suitable physical or wireless communication link(s). 
         [0040]    The I/O unit  225  allows for input and output of data. For example, the I/O unit  225  may provide a connection for user input through a keyboard, mouse, keypad, touchscreen, or other suitable input device. The I/O unit  225  may also send output to a display, printer, or other suitable output device. 
         [0041]    Although  FIG. 2  illustrates one example configuration of a security appliance  160 , various changes may be made to  FIG. 2 . For example, the security appliance  160  can come in a wide variety of configurations. The security appliance  160  shown in  FIG. 2  is meant to illustrate one example type of security appliance and does not limit this disclosure to a particular type of security appliance. 
         [0042]      FIG. 3  illustrates multiple components of a security appliance  160  according to this disclosure. As shown in  FIG. 3 , the security appliance  160  includes an IEC 61131 environment. The security appliance  160  includes a deep packet inspection component  305 . The deep packet inspection component  305  allows the security appliance  160  to provide a deep packet inspection firewall that supports both read-only and write only options. The deep packet inspection component  305  allows the security appliance  160  to provide deep packet inspection for all supported protocols of messages passing through the security appliance  160 . 
         [0043]    The security appliance  160  also supports multiple protocols through a multiple protocol support component  310 . The multiple protocol support component  310  allows the security appliance  160 , for example, to support any open standards based industrial protocol. The security appliance  160  also includes an embedded IEC 61131-3 component  315 . The embedded IEC 61131-3 component  315  provides the security appliance  160  with an environment that allows the security appliance  160  to manipulate data that passes through the security appliance  160 . The embedded IEC 61131-3 component  315  also allows the security appliance  160  to concentrate data as well as convert data protocols as data passes through the security appliance  160 . In other words, the embedded IEC 61131-3 component  315  allows the security appliance  160  to act as both a data concentrator and a pass-through protocol converter. A data concentrator can, for example, group data from two or more devices and transmit that data in a single table or a plurality data packet slots to a requesting controller or operator station so that the controller or operator station is unable to identify that the data is coming from the two or more devices. In other words, the controller or operator station can only identify that the data is coming from the data concentrator and not the particular two or more devices. The embedded IEC 61131-3 component  315  also allows the security appliance  160  to combine the features of a programmable logic controller, a protocol gateway, and a security appliance. The security appliance  160  also includes a security component  320 . The security component  320  allows the security appliance to provide modern cyber-security features including IPsec with X.509 certificate M2M endpoint authentication and cryptographically secure storage for digital certificates and digital keys. 
         [0044]    Although  FIG. 3  illustrates one example of a security appliance  160 , various changes may be made to  FIG. 3 . The security appliance  160  shown in  FIG. 3  is meant to illustrate one example type of security appliance and does not limit this disclosure to a particular type of security appliance. 
         [0045]      FIG. 4  illustrates an example method  400  according to this disclosure. The method  400  can be implemented using any suitable devices and in any suitable systems. For example, as discussed below, the method  400  is implemented with a security appliance  160  discussed herein. For ease of explanation, the method  400  is described with respect to the system  100  of  FIG. 1 . 
         [0046]    As shown in  FIG. 4 , at step  405 , a security appliance  160  configures with a first device in a first network. The first device utilizes a first communication protocol with a first level of security. At step  410 , the security appliance  160  receives data from the first device through the first communication protocol over the first network. The security appliance  160  is configured to concentrate data as well as communicate data communicating between a network utilizing a less secure protocol and network utilizing a more secure protocol using an embedded IEC 61131-3 component  315 . At step  415 , the security appliance  160  analyzes the received data and determines a second device on a second network using a second communication protocol having a second level of security that is higher than the first level of security that is intended to receive the data. The second device can receive data on a second network utilizing a second protocol that is more secure than the first protocol. In an embodiment, the first communication protocol and the second communication protocol are not compatible protocols. At step  420 , the security appliance  160 , using the embedded IEC 61131-3 component  315 , authenticates the received data so that the received data can be communicated through the second network using the second secure protocol. At step  425 , the security appliance  160  transmits the data using the second communication protocol to the second device. 
         [0047]    Although  FIG. 4  illustrates one example of the method  400 , various changes may be made to  FIG. 4 . For example, while shown as a series of steps, various steps shown in  FIG. 4  could overlap, occur in parallel, occur in a different order, or occur multiple times. Moreover, some steps could be combined or removed and additional steps could be added according to particular needs. 
         [0048]      FIG. 5  illustrates an example method  500  according to this disclosure. The method  500  can be implemented using any suitable devices and in any suitable systems. For example, as discussed below, the method  500  is implemented with a security appliance  160  discussed herein. For ease of explanation, the method  500  is described with respect to the system  100  of  FIG. 1 . 
         [0049]    As shown in  FIG. 5 , at step  505 , a security appliance  160  configures with a second device within a second network using a second secure protocol. At step  510 , the security appliance  160  receives data from the second device via the second network using the second secure protocol. In an embodiment, the security appliance  160  can receive data from the second device in response to transmitting data to the second device (for example, in response to transmitting data as described at step  425  of  FIG. 4 ). The security appliance  160  is configured to concentrate data as data is received the security appliance  160  using an embedded IEC 61131-3 component  315 . At step  515 , the security appliance  160  analyzes the received data and determines a first device that is intended to receive the data. The first device utilizes a first communication protocol different from the second communication protocol. In an embodiment, the second communication protocol and the first communication protocol are not compatible protocols. At step  520 , the security appliance  160 , using the embedded IEC 61131-3 component  315 , authenticates the received data so that the received data can be communicated through the first network using the first secure protocol. At step  525 , the security appliance  160  transmits the data using the first communication protocol to the first device. 
         [0050]    Although  FIG. 5  illustrates one example of the method  500 , various changes may be made to  FIG. 5 . For example, while shown as a series of steps, various steps shown in  FIG. 5  could overlap, occur in parallel, occur in a different order, or occur multiple times. Moreover, some steps could be combined or removed and additional steps could be added according to particular needs. 
         [0051]    In some embodiments, various functions described in this patent document are implemented or supported by a computer program that is formed from computer readable program code and that is embodied in a computer readable medium. The phrase “computer readable program code” includes any type of computer code, including source code, object code, and executable code. The phrase “computer readable medium” includes any type of medium capable of being accessed by a computer, such as read only memory (ROM), random access memory (RAM), a hard disk drive, a compact disc (CD), a digital video disc (DVD), or any other type of memory. A “non-transitory” computer readable medium excludes wired, wireless, optical, or other communication links that transport transitory electrical or other signals. A non-transitory computer readable medium includes media where data can be permanently stored and media where data can be stored and later overwritten, such as a rewritable optical disc or an erasable memory device. 
         [0052]    It may be advantageous to set forth definitions of certain words and phrases used throughout this patent document. The terms “application” and “program” refer to one or more computer programs, software components, sets of instructions, procedures, functions, objects, classes, instances, related data, or a portion thereof adapted for implementation in a suitable computer code (including source code, object code, or executable code). The term “communicate,” as well as derivatives thereof, encompasses both direct and indirect communication. The terms “include” and “comprise,” as well as derivatives thereof, mean inclusion without limitation. The term “or” is inclusive, meaning and/or. The phrase “associated with,” as well as derivatives thereof, may mean to include, be included within, interconnect with, contain, be contained within, connect to or with, couple to or with, be communicable with, cooperate with, interleave, juxtapose, be proximate to, be bound to or with, have, have a property of, have a relationship to or with, or the like. The phrase “at least one of,” when used with a list of items, means that different combinations of one or more of the listed items may be used, and only one item in the list may be needed. For example, “at least one of: A, B, and C” includes any of the following combinations: A, B, C, A and B, A and C, B and C, and A and B and C. 
         [0053]    The description in the present application should not be read as implying that any particular element, step, or function is an essential or critical element that must be included in the claim scope. The scope of patented subject matter is defined only by the allowed claims. Moreover, none of the claims is intended to invoke 35 U.S.C. §112(f) with respect to any of the appended claims or claim elements unless the exact words “means for” or “step for” are explicitly used in the particular claim, followed by a participle phrase identifying a function. Use of terms such as (but not limited to) “mechanism,” “module,” “device,” “unit,” “component,” “element,” “member,” “apparatus,” “machine,” “system,” “processor,” or “controller” within a claim is understood and intended to refer to structures known to those skilled in the relevant art, as further modified or enhanced by the features of the claims themselves, and is not intended to invoke 35 U.S.C. §112(f). 
         [0054]    While this disclosure has described certain embodiments and generally associated methods, alterations and permutations of these embodiments and methods will be apparent to those skilled in the art. Accordingly, the above description of example embodiments does not define or constrain this disclosure. Other changes, substitutions, and alterations are also possible without departing from the spirit and scope of this disclosure, as defined by the following claims.