Patent Publication Number: US-8526470-B2

Title: Synchronized commands for network testing

Description:
NOTICE OF COPYRIGHTS AND TRADE DRESS 
     A portion of the disclosure of this patent document contains material which is subject to copyright protection. This patent document may show and/or describe matter which is or may become trade dress of the owner. The copyright and trade dress owner has no objection to the facsimile reproduction by anyone of the patent disclosure as it appears in the Patent and Trademark Office patent files or records, but otherwise reserves all copyright and trade dress rights whatsoever. 
     BACKGROUND 
     1. Field 
     This disclosure relates to generating traffic for testing a network or network device. 
     2. Description of the Related Art 
     In many types of communications networks, each message to be sent is divided into portions of fixed or variable length. Each portion may be referred to as a packet, a frame, a cell, a datagram, a data unit, or other unit of information, all of which are referred to herein as packets. 
     Each packet contains a portion of an original message, commonly called the payload of the packet. The payload of a packet may contain data, or may contain voice or video information. The payload of a packet may also contain network management and control information. In addition, each packet contains identification and routing information, commonly called a packet header. The packets are sent individually over the network through multiple switches or nodes. The packets are reassembled into the message at a final destination using the information contained in the packet headers, before the message is delivered to a target device or end user. At the receiving end, the reassembled message is passed to the end user in a format compatible with the user&#39;s equipment. 
     Communications networks that transmit messages as packets are called packet switched networks. Packet switched networks commonly contain a mesh of transmission paths which intersect at hubs or nodes. At least some of the nodes may include a switching device or router that receives packets arriving at the node and retransmits the packets along appropriate outgoing paths. Packet switched networks are governed by a layered structure of industry-standard protocols. Layers 1, 2, 3, 4, and 7 of the structure are the physical layer, the data link layer, the network layer, the transport layer, and the application layer, respectively. 
     Layer 1 protocols define the physical (electrical, optical, or wireless) interface between nodes of the network. Layer 1 protocols include various Ethernet physical configurations, the Synchronous Optical Network (SONET) and other optical connection protocols, and various wireless protocols such as Wi-Fi. 
     Layer 2 protocols govern how data is logically transferred between nodes of the network. Layer 2 protocols include the Ethernet, Asynchronous Transfer Mode, Frame Relay, Point to Point Protocol, Layer 2 Tunneling Protocol, Fiber Distributed Data Interface, Synchronous Data Link Control, High-Level Data Link Control, Integrated Services Digital Network, Token Ring, various wireless protocols, various Ethernet and Fibre Channel protocols, and other protocols. 
     Layer 3 protocols govern how packets are routed from a source to a destination along paths connecting multiple nodes of the network. The dominant layer 3 protocols are the well-known Internet Protocol version 4 (IPv4) and version 6 (IPv6). A packet switched network may need to route IP packets using a mixture of layer 2 protocols. At least some of the nodes of the network may include a router that extracts a destination address from a network layer header contained within each packet. The router then uses the destination address to determine the route or path along which the packet should be retransmitted. A typical packet may pass through a plurality of routers, each of which repeats the actions of extracting the destination address and determining the route or path along which the packet should be retransmitted. 
     Layer 4 protocols govern end-to-end message delivery in a network. In particular, the Transmission Control Protocol (TCP) provides for reliable delivery of packets streams using a system of sequential acknowledgement and retransmission when necessary. TCP is a connection-oriented protocol in which two devices exchange messages to open a virtual connection via the network. Once a connection is opened, bidirectional communications may occur between the connected devices. The connection may exist until closed unilaterally by one of the devices. Opening and closing a connection both require several steps at which specific messages are exchanged between the two devices. A connection may also be closed when an anticipated response is not received by one device for a predetermined period of time, commonly called a “time-out”. A TCP connection is considered to be “stateful” since each device must maintain information describing the state of the connection (being opened, established, being closed), what data has been sent, and what sent data has been acknowledged. The User Datagram Protocol (UDP) is an alternative layer 4 protocol that provides for delivery of packet streams. UDP connections are stateless and do not provide for reliable delivery. 
     Layer 7 protocols include the Hyper-Text Transfer Protocol (HTTP) used to convey HTML documents such as Web pages, and the Simple Mail Transfer Protocol (SMTP) and Post Office Protocol (POPS) used to convey electronic mail messages. Other layer 7 protocols include Simple Message System (SMS), File Transfer Protocol (FTP), Real Time Protocol (RTP), Real-time Transport Control Protocol (RTCP), Real Time Streaming Protocol (RTSP), Media Gateway Control Protocol (MEGACO), Session Initiation Protocol (SIP), and other protocols used to transfer data, voice, video, and network control information over a network. 
     In order to test a packet switched network or a device included in a packet switched communications network, test traffic comprising a large number of packets may be generated, transmitted into the network at one or more ports, and received at different ports. In this context, the term “port” refers to a communications connection between the network and the equipment used to test the network. The term “port unit” refers to a module within the network test equipment that connects to the network at a port. The received test traffic may be analyzed to measure the performance of the network. Each port unit connected to the network may be both a source of test traffic and a destination for test traffic. Each port unit may emulate a plurality of logical source or destination addresses. Each port unit may emulate a plurality of network users, clients, peers, servers, or other network devices. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a block diagram of a network environment. 
         FIG. 2  is a flow chart of a process for testing a network. 
         FIG. 3  is a flow chart of a process for defining test traffic. 
         FIG. 4  is a graphical representation of an exemplary emulated user activity. 
         FIG. 5  is a graphical representation of another exemplary emulated user activity. 
         FIG. 6  is a representation of a graphical user interface. 
         FIG. 7  is a graphical representation of an emulated user community. 
     
    
    
     Throughout this description, elements appearing in block diagrams are assigned three-digit reference designators, where the most significant digit is the figure number and the two least significant digits are specific to the element. An element that is not described in conjunction with a block diagram may be presumed to have the same characteristics and function as a previously-described element having a reference designator with the same least significant digits. 
     DETAILED DESCRIPTION 
     Description of Apparatus 
       FIG. 1  shows a block diagram of a network environment. The environment may include a test administrator  105 , network test equipment  100 , and a network  190  which includes one or more network devices  192 . 
     The network test equipment  100  may be a network testing device, performance analyzer, conformance validation system, network analyzer, or network management system. The network test equipment  100  may include one or more network cards  106  and a backplane  104  contained or enclosed within a chassis  102 . The chassis  102  may be a fixed or portable chassis, cabinet, or enclosure suitable to contain the network test equipment. The network test equipment  100  may be an integrated unit, as shown in  FIG. 1 . Alternatively, the network test equipment  100  may comprise a number of separate units cooperative to provide traffic generation and/or analysis. The network test equipment  100  and the network cards  106  may support one or more well known standards or protocols such as the various Ethernet and Fibre Channel standards, and may support proprietary protocols as well. 
     The network cards  106  may include one or more field programmable gate arrays (FPGAs), application specific integrated circuits (ASICs), programmable logic devices (PLDs), programmable logic arrays (PLAs), processors, and other kinds of devices. In addition, the network cards  106  may include software and/or firmware. The term network card encompasses line cards, test cards, analysis cards, network line cards, load modules, interface cards, network interface cards, data interface cards, packet engine cards, service cards, smart cards, switch cards, relay access cards, and the like. The term network card also encompasses modules, units, and assemblies that may include multiple printed circuit boards. Each network card  106  may support a single communications protocol, may support a number of related protocols, or may support a number of unrelated protocols. The network cards  106  may be permanently installed in the network test equipment  100  or may be removable. 
     Each network card  106  may contain one or more port unit  110 . Each port unit may include circuits and software to generate test traffic and/or to receive and analyze test traffic. Each port unit may be coupled to the test administrator  105 . Each port unit  110  may connect to the network  190  through one or more ports. Each port unit  110  may be connected to the network  190  through a communication medium  195 , which may be a wire, an optical fiber, a wireless link, or other communication medium. 
     The backplane  104  may serve as a bus or communications medium for the network cards  106 . The backplane  104  may also provide power to the network cards  106 . 
     The test administrator  105  may be a computing device included within or coupled to the network test equipment  100 . The test administrator  105  may include an operator interface (not shown) that may be used to plan a test session, to control the test session, and/or to view test results during and after the test session. The operator interface may include, for example, a display and a keyboard, mouse, and/or other input devices (not shown). The test administrator  105  may include or be coupled to a printer or other data output device (not shown) for output of test results. The test administrator  105  may include or be coupled to a storage device (not shown) for storing test data and results for future review and/or analysis. 
     The network  190  may be a Local Area Network (LAN), a Wide Area Network (WAN), a Storage Area Network (SAN), wired, wireless, or a combination of these, and may include or be the Internet. Communications on the network  190  may take various forms, including frames, cells, datagrams, packets or other units of information, all of which are referred to herein as packets. The network test equipment  100  and the network devices  192  may communicate simultaneously with one another, and there may be plural logical communications paths between the network test equipment  100  and a given network device  192 . The network itself may be comprised of numerous nodes providing numerous physical and logical paths for data to travel. 
     The one or more network devices  192  may be any devices capable of communicating over the network  190 . The one or more network devices  192  may be computing devices such as workstations, personal computers, servers, portable computers, personal digital assistants (PDAs), computing tablets, cellular/mobile telephones, e-mail appliances, and the like; peripheral devices such as printers, scanners, facsimile machines and the like; network capable storage devices including disk drives such as network attached storage (NAS) and storage area network (SAN) devices; networking devices such as routers, relays, hubs, switches, bridges, server load balancers (SLBs), and multiplexers. In addition, the one or more network devices  192  may include appliances, alarm systems, and any other device or system capable of communicating over a network. The network  190  may consist of a single network device  192  or a plurality of network devices interconnected by a plurality of communications paths, all of which will be referred to herein as the network under test (NUT). 
     Description of Processes 
     Referring now to  FIG. 2 , a process  200  for testing a NUT may start at  205  and finish at  295 . The process  200  may be executed within a test environment such as that shown in  FIG. 1 . The process  200  may be performed using a test administrator  105  in conjunction with network test equipment  100 . The process  200  may be used to test a network such as the network  190  and/or a network device such as the network device  192 . 
     The process  200  may include creating a test plan at  210 , initializing a test system and the NUT at  270 , running a test session according to the test plan at  275 , and reporting test results at  280 . For ease of description, these actions are shown to be sequential in  FIG. 2 . However, these actions may be performed, to at least some extent, concurrently. For example, interim test results may be reported at  280  while a test session is still running at  275 . Further, the process  200  may be, to at least some extent, cyclic. For example, interim test results reported at  280  may be used to modify the test plan, either automatically or as a result of some user action, as indicated by dashed line  285 . 
     Creating a test plan at  210  may include defining the network and/or device to be tested (the network under test or NUT) and the architecture of the test system at  215 . Defining the test system at  215  may include defining the test equipment that will conduct the test, including the number and type of port units that will be connected to the network or device under test. Defining the test system at  215  may also include definitions of what each port unit will represent or emulate during the test. For example, a particular port unit may be tasked to emulate a local area network encompassing a particular block of IP (internet protocol) addresses. For further example, a port unit may be tasked to emulate a large plurality of user devices that access a wireless network through a particular access point. 
     After the NUT and the test system are defined at  215 , the test traffic to be generated during the test session may be defined. The test traffic and the techniques used to define the test traffic may depend on the type of network or device to be tested. For example, when a NUT is a switch or router operating at layer 2 or layer 3 of the network structure, the test traffic may include a large plurality of IP packets apparently originating from a plurality of source IP addresses and destined for a plurality of destination IP addresses. In this case, the actual content of the IP packets may be unimportant. However, when the NUT operates at a higher layer of the network structure (for example, a server, a server load balancer, a network security device that performs packet inspection, and other network devices), the test traffic may include or be a plurality of simulated application-layer transactions. In this case, the test traffic may be defined at  220  by a plurality of emulated user (EU) activities, each of which causes some traffic to be generated and transmitted via the NUT. 
     An EU activity may be any activity or transaction that can be performed by a user computing device, where a “user computing device” is any device that receives services from or via a network. User computing devices may include personal computers, laptop computers, set top boxes, video game systems, personal video recorders, telephones, smart phones, personal digital assistants, e-mail appliances, and any other computing device connected to a network. During a subsequent test session, the test system may emulate EUs performing the activities defined at  220  and thus automatically convert the defined EU activities into traffic for testing the NUT. 
     Referring now to  FIG. 3 , a process  320  for defining test traffic in terms of EU activities may be suitable for use at  220  in the process  200  of  FIG. 2 . After the test system and the NUT are defined (at  215  in  FIG. 2 ), an EU activity may be defined. Defining the EU activity may begin by identifying the EU at  332 . The EU may be identified by assigning a MAC (media access control) address, an IP address, an IMSI (international mobile subscriber identification), an MSIN (mobile subscriber identification number), or in some other way that distinguishes the EU. The EU identification may also indicate, in view of the test system definition from  215 , what portion of the test system will emulate the EU and how the EU will be connected to the NUT. 
     The activity of the EU identified at  332  may include one or more commands. Each command may be associated with a protocol, which is to say that each command may be defined by and form a part of a communications protocol. Each EU activity may include one or more layer 4-7 commands defined at  334  and/or one or more layer 2-3 commands defined at  336 . In this context, a “layer 2-3” command is a command associated with a layer 2 or layer 3 protocol. Similarly, a “layer 4-7 command” is a command associated with a layer 4 to layer 7 protocol. An EU activity may include commands from multiple layer 2-3 and/or layer 4-7 protocols 
     The one or more layer 4-7 commands defined at  334  may be, for example, commands or requests to be made by the EU according to a layer 7 protocol such as HTTP, FTP, SMS, SMTP, POP3, SIP, and other application layer protocols used to transfer data, voice, video, and network control information over a network. The one or more layer 4-7 commands may, for example, cause a test system to emulate a user performing some task such as browsing the Internet, sending e-mail or text messages, making VOIP (voice over Internet protocol) or cellular telephone calls, or some other activity. The one or more layer 2-3 commands may be commands that affect the NUT and/or the connection between the EU and the NUT independent of the execution of the layer 4-7 commands. For example, when the NUT is a portion of a wireless network, possible layer 2-3 commands include, for example, requesting a bearer modification, emulating a handoff between cells, emulating a tracking area update, and other network management actions performed within wireless networks. When the NUT is a portion of a wired network, possible layer 2-3 commands include, for example, a DHCP (Dynamic Host Configuration Protocol) request and a DHCP release. 
     At  338 , at least a first command associated with a first protocol and a second command associated with a second protocol different from the first protocol may be synchronized. The first and second commands may be layer 4-7 commands entered at  334 . The first and second commands may be layer 2-3 commands entered at  336 . The first and second commands may include a layer 4-7 command and a layer 2-3 command. In this context, the term “synchronized” means that a desired temporal relationship is defined between two or more commands. Examples of a desired temporal relationship include requiring that commands be performed in a specific order, or requiring that certain commands be performed concurrently, or requiring that commands associated with different protocols be interleaved in a prescribed order. Continuing the example of a wireless network, a command to emulate a cell handoff may be synchronized with an FTP Get command such that the emulated cell handoff occurs during the downloading of a file from the NUT. More than two commands may be synchronized at  338 . 
       FIG. 4  is a graphical representation of an example EU activity  400  which may be defined using the process  320 . The EU activity  400  may start at  405 . The EU activity  400  may include two layer 2-3 commands  410  and  445 , and three HTTP commands  420 ,  425 ,  430  that are performed within a loop defined by a loop start  415  and a loop end  435 . The loop from  415  to  435  may be performed a designated number of times. Optionally, one or more parameters of the HTTP commands  420 ,  425 ,  430  may be changed at  440  each time the loop is repeated. After the loop has repeated the designated number of times, the EU activity  400  may end at  450 . 
     Each EU activity defined in the process  320  may be independent of other EU activities. Layer 2-3 commands such as the Bearer Modification command  410  and the Teardown Session command  450  within the EU activity  400  may not have any effect on other EU activities. 
       FIG. 5  is a graphical representation of a more complex EU activity  500  which also may be defined using the process  320 . The EU activity  500  may start at  505 . The EU activity  500  may include layer 2-3 commands  510 ,  515 ,  520 , and  525 ; FTP commands  530 ,  535 ,  540 ,  545 , and  550 ; and HTTP commands  555 ,  560 , and  565 . The layer 2-3 commands may include commands from two or more layer 2-3 protocols. In this example, the FTP commands  530 - 550  may be emulated using a wireless layer 2 protocol such as eGTP (Extended GPRS Tunneling Protocol), and the HTTP commands  555 - 565  may be emulated using a wired layer 2 protocol such as an Ethernet protocol. In this case, layer 2-3 commands  510 ,  520 , and  525  may be eGTP Bearer Modification, Handover, and Tear Down commands and layer 2-3 command  515  may be a DHCP Request command. 
     Synchronization links  570 ,  575 ,  580 ,  585 ,  590  may be defined between commands such that the FTP Login command  530  is executed after the Bearer Modification command  510 , the DHCP Request command  515  is executed between the Bearer Modification command  510  and the HTTP Get command  555 , the Handover command  520  is executed during execution of the FTP Get command  540 , the FTP Quit command  550  is executed after the HTTP Post command  565 , and the Tear Down Session command  525  is executed after the FTP Quit command  550 . Other types of synchronization may be defined between commands. Synchronization may be defined between layer 2-3 commands and layer 4-7 commands, between layer 2-3 commands of the same or different protocols, and between layer 4-7 commands of the same or different protocols. 
     EU activities, such as the EU activities  400  and  500 , may be defined by a test engineer via a user interface to a test administrator computing device such as the test administrator  105 . The test administrator computing device may provide a graphical user interface (GUI) to facilitate defining user actions. 
       FIG. 6  is a representation of a GUI  600  as it may appear after an EU activity similar to the EU activity  500  of  FIG. 5  has been defined. The GUI  600  is an example of the nearly unlimited number of possible configurations of a GUI for defining EU activities. The GUI  600  may have a plurality of panes  610 ,  620 ,  630  showing commands for a corresponding plurality of protocols. In this example, pane  610  shows HTTP commands, pane  620  shows FTP commands, and pane  630  shows control plane commands for a wireless network using eGTP. The GUI  600  may include an identifier  650  for the EU activity being defined, and a plurality of control buttons  640 . The control buttons  640  may include (from left to right) controls to add, delete, edit, or replace a command within the EU activity. The control buttons may also include a control to link or synchronize commands, a control to check whether the defined commands are self-consistent and executable, a control to indicate that the definition of a particular EU activity is done, and a control to start defining a new EU activity. These controls may be augmented by pop-up lists, pull-down menus, and additional display screens to facilitate defining each EU activity. For example, clicking or designating the “add” button may open a pull-down list of the possible commands that may be added. Similarly, highlighting a particular command and designating the “edit” button may open a pop-up editable list of parameters associated with the highlighted command. 
     Referring back to  FIG. 3 , the process  320  for defining test traffic may be cyclic in nature. At  340  a determination may be made if additional EU activities are required during a test session, and the actions from  332 - 338  may be repeated as necessary until all EU activities are defined. 
     A test session for a complex NUT may require test traffic including literally millions of packets representing the activities of thousands or hundreds of thousands of EUs. It may be impractical or undesirable to individually define the activity of each EU. Therefore a finite number of EU activities may be defined at  332 - 338  and then replicated to form an EU “community” including a large plurality of EUs to be emulated by the test system. When a determination is made at  340  that all EU activities are defined, an EU community may be defined at  342   
     Referring now to  FIG. 7 , an exemplary EU community  700  may be composed of a plurality of EUs, each of which is performing or executing a defined EU activity. The exemplary EU community  700  includes EUs replicating three different EU activities  710 ,  720 ,  730 . In this patent, the term “replicate” means “to copy, but not necessarily identically”. The replicas of a given EU activity may differ in some aspect. For example, each replica of a given EU activity may be assigned a different MAC or IP address, or may be assigned a different mobile user identification number. The example EU community  700  contains m replicas of EU activity 1, n replicas of EU activity 2, and p replicas of EU activity 3, where m, n, and p are positive, and possibly large, integers. An EU community may include more one or more different EU activities. The number of EU activities may be smaller than a number of EUs within an EU community. For example, the number of EUs in an EU community may be N and the number of predefined user activities may be M, where N and M are positive integers and N is greater than or equal to M. The number of replicas of each EU activity within an EU community may be the same or different for each EU activity. 
     At least some of the EU activities within an EU community may include one or more layer 4-7 commands and one or more layer 2-3 commands synchronized with another layer 2-3 command or one of the layer 4-7 commands. An EU activity may contain a plurality of layer 4-7 commands and a plurality of layer 2-3 commands, at least some of which are synchronized with layer 4-7 commands. An EU activity may contain a plurality of layer 4-7 commands, some of which may be synchronized with other layer 4-7 commands. 
     Referring back to  FIG. 2 , after the test traffic is defined at  220 , the test system and the NUT may be initialized at  270 . Initializing the test system at  270  may include transferring data and instructions to the port units of the test system to enable the port units to emulate the EU activities defined at  220 . Initializing the test system may also include providing instructions to the port units indicating what test results should be captured during the test session. These instructions may include instructions to accumulate certain traffic statistics as well as instructions and criteria for capturing packets entering and/or exiting the NUT. Initializing the test system and the NUT at  270  may include the test system and the NUT exchanging information such that the NUT becomes aware of the configuration of the test system. For example, the test system and the NUT may use standard routing protocols and/or discovery protocols to inform the NUT what IP addresses are emulated at each port unit of the test system. 
     When the test traffic is defined at  220  in terms of application-layer EU activities, each defined EU activity may result in one or a plurality of packets that may be generated and transmitted during the ensuing test session. For example, an HTTP Get command may result in the opening of a TCP connection (which involves the exchange of several TCP/IP packets) followed by a single TCP/IP packet conveying the HTTP Get request. The HTTP Get command may also result in a test port unit generating and transmitting one or more TCP/IP packets to the NUT, or a test port unit emulating a server responding to the HTTP Get request. An FTP Put command may result in generation and transmission of a large plurality of TCP/IP packets representing the content of the file that is being uploaded. When the test traffic is defined at  220  in terms of application-layer EU activities, initializing the test system at  270  may also include translating at least some EU activities into instructions for a plurality of packets to be generated and sent during the test session. Alternatively, EU activities may be communicated to test equipment port units and may be translated into appropriate packets in real-time as the test session progresses. 
     After the test system and the NUT are initialized at  270 , the test session may be run or executed at  275 . Running the test session may include executing the EU activities defined at  220 , which is to say the test equipment may emulate users performing the defined EU activities. Executing the EU activities may include generating and transmitting test traffic to the NUT, receiving test traffic transmitted through the NUT and/or responses generated within the NUT, and accumulating test data such as received traffic statistics and captured packets. The defined replicas of a given EU activity may or may not be executed concurrently. For example, the number of concurrent replicas of one or more EU activities may be gradually increased during a test session to investigate the effect of increasing traffic load on the performance of a NUT. For example, Published Patent Application No. US2011/0022700A1 describes how a GUI may be used to define a timeline for scaling traffic load during a test session. 
     Interim and final results of the test performed at  275  may be reported at  280 . Reporting test results at  280  may include processing (i.e. sorting, filtering, and/or aggregating) traffic statistics; displaying the processed traffic statistics; storing and/or printing raw or processed traffic statistics; and storing, displaying, and/or printing captured packets. Although the results of each executed EU activity may not be individually reported at  280 , each EU activity may contribute, to some extent, to the test results reported at  280 . For example, the test results reported at  280  may include test statistics such as a total number of packets received, a number of packets received out-of-order, an average packet latency time, a maximum number of concurrent connections, and other statistics, each of which may be aggregated over some or all of the executed EU activities. 
     Closing Comments 
     Throughout this description, the embodiments and examples shown should be considered as exemplars, rather than limitations on the apparatus and procedures disclosed or claimed. Although many of the examples presented herein involve specific combinations of method acts or system elements, it should be understood that those acts and those elements may be combined in other ways to accomplish the same objectives. With regard to flowcharts, additional and fewer steps may be taken, and the steps as shown may be combined or further refined to achieve the methods described herein. Acts, elements and features discussed only in connection with one embodiment are not intended to be excluded from a similar role in other embodiments. 
     As used herein, “plurality” means two or more. As used herein, a “set” of items may include one or more of such items. As used herein, whether in the written description or the claims, the terms “comprising”, “including”, “carrying”, “having”, “containing”, “involving”, and the like are to be understood to be open-ended, i.e., to mean including but not limited to. Only the transitional phrases “consisting of” and “consisting essentially of”, respectively, are closed or semi-closed transitional phrases with respect to claims. Use of ordinal terms such as “first”, “second”, “third”, etc., in the claims to modify a claim element does not by itself connote any priority, precedence, or order of one claim element over another or the temporal order in which acts of a method are performed, but are used merely as labels to distinguish one claim element having a certain name from another element having a same name (but for use of the ordinal term) to distinguish the claim elements. As used herein, “and/or” means that the listed items are alternatives, but the alternatives also include any combination of the listed items.