Patent Application
20110002228
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.
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's equipment.
Communications networks that transmit messages as packets are called packet switched networks. In order to test a packet switched network or a device included in a communications network, it is often desirable to generate network traffic having a data rate equal to the line rate or maximum possible data rate of the network communication path or device.
A series of packets originating from a single source and having a specific type of packet and a specific rate will be referred to herein as a “stream.” A source may be, for example, a port on a network interface. A source may support multiple outgoing streams simultaneously and concurrently, for example to accommodate multiple packet types or rates. “Simultaneously” means “at exactly the same time.” “Concurrently” means “within the same time.”
For the purpose of reporting network traffic data, the packets within a stream may be organized into flows, where a “flow” is any plurality of data units for which network traffic statistics are accumulated and reported. The data units in a given flow may be distinguished by a flow identifier contained in each data unit. The flow identifier may be, for example, an address, a port number, a tag, or some other field or combination of fields within each data unit.
A plurality of concurrent streams may be combined to form the output from a traffic generator, which will be referred to herein as “test traffic”. The streams within the traffic may be combined through interleaving. The interleaving may be balanced, unbalanced, and distributed among the represented streams. The data rate of the test traffic may be equal to the line rate of a network communication path over which the output is transmitted. Although the packets within a given stream may be transmitted at the line rate, the average data rate of each stream over time may be much lower, since a plurality of interleaved streams may share the data rate of the test traffic. To test a modern “triple play” network and network equipment, the test traffic may contain simulated data, audio, and video streams.
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.
In block diagrams, arrow-terminated lines may indicate data paths rather than signals. Each data path may be multiple bits in width. For example, each data path may consist of 4, 8, 16, 32, 64, or more parallel connections.
Referring now to
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 114 and a backplane 112 contained or enclosed within a chassis 110. The chassis 110 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
The network cards 114 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 114 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 114 may provide one or more network ports. The ports of the network cards 114 may be connected to the network through a communication medium 185, which may be a wire, an optical fiber, a wireless link, or other communication medium. Each network card 114 may support a single communications protocol, may support a number of related protocols, or may support a number of unrelated protocols. The network cards 114 may be permanently installed in the network test equipment 100 or may be removable.
The backplane 112 may serve as a bus or communications medium for the network cards 114. The backplane 112 may also provide power to the network cards 120.
The network devices 195 may be any devices capable of communicating over the network 190. The network devices 195 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, and multiplexers. In addition, the network devices 195 may include appliances, alarm systems, and any other device or system capable of communicating over a network.
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 195 may communicate simultaneously with one another, and there may be plural logical communications between the network test equipment 100 and a given network device 195. The network itself may be comprised of numerous nodes providing numerous physical and logical paths for data to travel.
Referring now to
Within this description, the term “engine” means a collection of hardware, which may be augmented by firmware and/or software, that performs the described functions. An engine may typically be designed using a hardware description language (HDL) that defines the engine primarily in functional terms. The HDL design may be verified using an HDL simulation tool. The verified HDL design may then be converted into a gate netlist or other physical description of the engine in a process commonly termed “synthesis”. The synthesis may be performed automatically using a synthesis tool. The gate netlist or other physical description may be further converted into programming code for implementing the engine in a programmable device such as a field programmable gate array (FPGA), a programmable logic device (PLD), or a programmable logic arrays (PLA). The gate netlist or other physical description may be converted into process instructions and masks for fabricating the engine within an application specific integrated circuit (ASIC).
Within this description, the term “unit” also means a collection of hardware, firmware, and/or software, which may be on a larger scale than an “engine”. For example, a unit may contain multiple engines, some of which may perform similar functions in parallel. The terms “engine” and “unit” do not imply any physical separation or demarcation. All or portions of one or more units and/or engines may be collocated on a common card, such as a network card 114, or within a common FPGA, ASIC, or other circuit device.
The CPU 284 may provide the scheduler 220 with instructions 286 to form a plurality of streams that may be interleaved to form test traffic 282. Each of the streams may include a sequence of packets. The packets within each stream may be of the same general type but may vary in length and content. The scheduler 220 may perform multiple functions including scheduling the sequence of packets to be generated and determining the length and variable content for each packet.
The scheduler 220 may pass packet forming data 266 required to generate each packet to the transmit engine 270. The packet forming data 266 passed from the scheduler 220 to the transmit engine 270 may include a stream identifier which identifies the type of packet, a packet length, variable data to be incorporated into the packet, and instructions for filling the packet payload.
The network interface unit 280 may convert the test traffic 282 from the transmit engine 270 into the electrical, optical, or wireless signal format required to transmit the data flow to the network under test 290 via a link 285, which may be a wire, an optical fiber, a wireless link, or other communication link.
The CPU 284 may include a processor, a memory coupled to the processor, and various specialized units, circuits, software and interfaces for providing the functionality and features described here. The processes, functionality and features may be embodied in whole or in part in software which operates on the processor and may be in the form of firmware, an application program, an applet (e.g., a Java applet), a browser plug-in, a COM object, a dynamic linked library (DLL), a script, one or more subroutines, or an operating system component or service. The hardware and software and their functions may be distributed such that some functions are performed by the processor and others by other devices.
The scheduler 220, the transmit engine 270, the CPU 284, and the network interface unit 280 may include one or more of: logic arrays, memories, analog circuits, digital circuits, software, firmware, and processors such as microprocessors, field programmable gate arrays (FPGAs), application specific integrated circuits (ASICs), programmable logic devices (PLDs) and programmable logic arrays (PLAs). The physical partitioning of the components of the traffic generator 200 may be different from the functional partitioning shown in
The data flow to the network over the link 285 may have a maximum data rate, commonly termed the “line rate”. The data flow over the link 285 may use encoding to facilitate transmission. The encoding may cause the line rate and the actual clock rate for the data to be different. For example, the actual clock rate of a 10 GHz link using 64 bit to 66 bit encoding may be 10.3125 GHz. Although the data rate through the traffic generator may be the same as the line rate, the data paths between the various functional blocks may transmit multiple bits in parallel such that the actual clock rate within the functional blocks may be less than the line rate. For example, a traffic generator with a 10 GHz line rate may process 50 bits in parallel and have an internal clock rate of about 200 MHz.
The memory 350 may be loaded with the definitions of a plurality of streams that constitute a testing session. The memory may be loaded from the CPU 284 shown in
The memory 350 may be dynamic random access memory (DRAM) or static random access memory (SRAM). The memory 350 may be implemented within an ASIC, FPGA or other circuit device containing all or portions of the stream scheduler 325, the length generator 360, and the overlay engine 362. The memory 350 may be implemented wholly or partially with DRAM or SRAM memory chips external to the ASIC, FPGA or other device.
The stream scheduler 325 may generate next packet data 348 defining the next packet to be formed by first determining the next stream to contribute a packet to the test traffic based on the stream definitions and timing information stored in the memory 350. When a large number of streams must be scheduled, the scheduler 320 may include a plurality of parallel stream schedulers 325. Although
After the stream scheduler 325 or arbitrator 334 has identified the next stream and the next packet to be formed, the length generator 360 may establish the length of the next packet. The length of the next packet may be constant within the stream, may be random, may be calculated by adding a predetermined constant to the length of the previous packet in the stream, or may be established in some other manner.
After the stream scheduler 325 has identified the next stream to be formed, the overlay engine 362 may establish overlay data for the next packet. The overlay engine 362 may determine the overlay data concurrently or after the length generator 360 determines the packet length. The overlay data may be any data that is not constant between packets of the next stream. The overlay data may be established by calculation, such as by adding a predetermined number to the corresponding data of the previous packet in the stream. The overlay data may also be determined randomly, may be determined from a table of stored values, or may be determined in some other manner as instructed by the stream definition for the next packet. One or more fields of overlay data may be established for each packet. Each field of overlay data may be established in a different manner.
The overlay engine 362 may provide packet forming data 366 to the transmit engine or transmit engines. The packet forming data may include length data, overlay data, and other information necessary to form the packet.
Referring now to
The plurality of slow timers 430 may be implemented with an arithmetic logic unit (ALU) 432, a working memory 452, and two banks of control memory 454A, 454B. The working memory and the banks of control memory 454A, 454B may be portions of the memory 350. The ALU 432, in conjunction with the working memory 452, may operate as a plurality of independent count-down timers. In the example of
The two control memories 454A, 454B may be used alternately, such that one control memory may be used by the slow timers 430 while the second control memory is being loaded with new or revised control data. The control memories 454A, 454B may be loaded by a processor such as the CPU 284 or another processor. The control memory used by the slow timers 430 may then be switched to reconfigure the operation of the slow timers 430 on the fly without interrupting the test traffic being generated. The ALU 432 may receive, from the CPU 284 or another source, a control memory bank select signal 438 indicating which of the two control memories 454A, 454B should be used by the slow timers 430.
The data stored in each control memory 454A, 454B may include, for each slow timer, a timer initial value (IV0-IVN-1), a timer interval (Interval0-IntervalN-1), a stream number or other data to identify the stream associated with the timer (Stream0-StreamN-1), a maximum number of packets to be initiated by each timer (MaxCnt0-MaxCntN-1), and status data (Status0-StatusN-1). The initial value (TV1-IVN-1), the timer interval (Interval1-IntervalN-1), and the present timer value (TV1-TVN-1) of each slow timer may be expressed in clock cycles and fractions of a clock cycle. The status data (Status0-StatusN-1) may include a bit indicating if the stream associated with a timer is enabled, and a bit indicating if the associated timer should be re-initialized when the control memory select signal changes state. The status data (Status0-StatusN-1) may include other information.
The ALU 432 may update the timer value (TV) and the packet count (PC) for one timer during each clock cycle in rotation, such that each of the timers is updated once every N clock cycles. The ALU 432 may include an update pointer 434 that designates one of the count-down timers to be updated. The update pointer may be incremented every clock cycle. Since each timer operates slowly with respect to the internal clock, the timers are referred to herein as “slow timers” as distinguished from typical count-down timers that decrement on every clock. Since a single ALU 432 services a plurality of N slow timers, the amount of logic circuits required may be substantially reduced compared to an alternative approach in which each timer is updated every clock cycle. The ALU 432 may also receive, from the CPU 284 or another source, an initialize signal 436.
The temporal interpolator 440 may be implemented with a circular buffer memory 442 having N memory slots, identified in
When the ALU 432 determines, based on the timer value TV associated with the count-down timer designated by the update pointer 434, that a packet should be initiated, the ALU 432 may store packet data in a slot within the circular buffer memory 442 of the temporal interpolator 440. The packet data stored in the circular buffer memory 442 may include a stream number associated with the designated count-down timer and fractional bits of the associated timer value. The fractional bits may be used subsequently, for example within the network interface unit 280, to adjust the departure time of the packet to be formed. The packet data stored in the circular buffer memory 442 may include additional information.
The operation of the slow timers 430 may be understood by considering
At 515, the ALU 432 may increment the update pointer 434 to designate the next count-down timer to be updated. At 525, the ALU may read the timer value (TV) associated with the designated count-down timer from the working memory 452 and may read the control data associated with the designated count-down timer from the active one of the control memories 454A, 454B.
The timer value TV may indicate how many clock periods remain before a packet associated with the designated count-down timer should be initiated. TV may be defined in whole or fractional clocks. At 530, the ALU 432 may determine if TV is greater than or equal to N, the number of slow timers serviced by the ALU 432. If TV is greater than or equal to N, the ALU may determine that the designated count-down timer does not need to initiate formation of a packet during this update cycle, which is to say that the designated count-down timer will be updated at least once more before an associated packet must be initiated. In this case, at 535, the ALU may reduce TV by N and store the updated TV into the working memory 452 at 540. Note that, since TV is defined in clock periods and since the designated count-down timer is only updated every N clocks, TV may be reduced by N each time the designated count-down timer is updated. The process may then await the next clock to update the next count-down timer.
If, at 530, a determination is made that TV is less than N, the stream scheduler 425 should initiate a packet associated with the designated count-down timer within the next N clocks. Specifically, if TV has a value k, where k<N, a packet associated with designated count-down timer should be initiated, if possible, k clocks into the future. In this case, at 545, the ALU may write packet data associated with the designated count-down timer into the temporal interpolator 440 such that the packet data is delayed by k clocks before being output as the next stream data 448. When the temporal interpolator 440 is implemented by a circular buffer 442, the write logic 446 may add the value k onto the value of the read pointer 444 to determine where to write the packet data.
The packet data written by the ALU into the circular buffer 442 may include the stream number and some or all of the status bits associated with the designated count-down timer, both of which were read from the control memory 454A or 454B at 525. The packet data written by the ALU into the circular buffer 442 may also include the fractional bits of the timer value TV. The packet data written by the ALU into the circular buffer 442 may also include a least-significant portion of the packet count PC.
Each slot in the circular buffer 442 may have an associated status bit 448 that is cleared every time the slot is read and set by the write logic 446 when packet data is written to the slot. Thus the status bit 448 may indicate when the associated slot in the circular buffer 442 is full or empty. When the ALU attempts, at 545, to write packet data to a slot in the circular buffer 442 that is full, the write logic 446 may redirect the packet data to the closest available empty slot.
After packet data is written at 545, the ALU may update TV by subtracting N and adding the interval for the designated count-down timer, which was previously read from the control memory 454A or 454B at 525. The updated TV may be stored in the working memory 452 at 540, and the process may then await the next clock to update the next count-down timer.
The operation of the stream scheduler 425 may be better understood through the examples of
The operation of the slow timers 430 may be further understood by considering
The actions 815, 825, 830, 835, and 840 are essentially the same as the counterpart actions in
In response to an initialize signal received at 805, at 810 the ALU 432 may set the timer value (TV) for each of N count-down timers to the corresponding initial value (IV) read from the control memory 454A or 454B. Additionally, at 810 the ALU 432 may set a packet count (PC) for each of N count-down timers to zero.
After initialization, each of the plurality of count-down timers may be updated in rotation as previously described in conjunction with
Additionally, at 820, the ALU 432 may determine if a switch between two banks of control memory 454A, 454B has occurred since the designated count-down timer was previously updated. When a bank switch has not occurred, the process may proceed at 830 as previously described. When a bank switch has occurred, at 870 the ALU 432 may determine, from a portion of the status information for the designated count-down timer read at 825, if the designated count-down timer should be reinitialized. For example, the parameters, such as interval, initial value, and stream identifier of a count-down timer assigned to a continuing stream may not change when the control memory banks are switched. In this case, the designated count-down timer may not require initialization in response to the bank switch and the process may proceed at 830. In some cases, such as a count-down timer being re-assigned to a new stream or when the number of count-down timers assigned to a continuing stream is changed, the designated count-down timer may require initialization. In this case, the designated count-down timer may be re0initialized at 875 by setting the count value CV to the initial value read at 825 and by setting the packet count PC to zero.
Referring now to
The start event at 905 may be, for example, the receipt of an initialize signal such as the initialize signal 436 in
At 915, one of the N count-down timers may be designated to be updated. The count-down timer to be updated may be designated, for example, by an update pointer which is incremented each cycle of a clock, such that each count-down timer is designated in rotation every N cycles of the clock.
At 920, a timer value and control data associated with the designated count-down timer may be read from a memory.
At 925, a determination may be made from the timer value whether a packet should be formed. Specifically, when the timer value is less than N (the number of count-down timers), packet data defining a packet to be formed may be stored in a temporal interpolator at 945. The packet data may then be delayed, at 955, for a period based on the timer value before the packet data is output to a transmit engine that will form the packet. Specifically, the packet data may be delayed for a number of clock cycles equal to the timer value at the time the packet data was stored in the temporal interpolator at 945.
The timer value may be updated at 930. When a determination was made at 925 that the timer value was greater than or equal to N, the timer value may be updated at 935 by subtracting N from the timer value. When a determination was made at 925, the timer value was less than N, the timer value may be updating by adding a respective predetermined interval to the timer value at 950 and then subtracting N from the sum at 935. The net effect of the actions at 950 and 935 may be to increase the timer value by the difference between the respective interval and N.
The updated timer value may be stored in the memory 940, and the process may repeat from 915. The process 900 may repeat the actions from 915 to 940 once for each cycle of the clock.
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.
For means-plus-function limitations recited in the claims, the means are not intended to be limited to the means disclosed herein for performing the recited function, but are intended to cover in scope any means, known now or later developed, for performing the recited function.
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.
