WO2024125731A1 - Procédé de test d'un bus de communication - Google Patents

Procédé de test d'un bus de communication Download PDF

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Publication number
WO2024125731A1
WO2024125731A1 PCT/DE2023/200240 DE2023200240W WO2024125731A1 WO 2024125731 A1 WO2024125731 A1 WO 2024125731A1 DE 2023200240 W DE2023200240 W DE 2023200240W WO 2024125731 A1 WO2024125731 A1 WO 2024125731A1
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WIPO (PCT)
Prior art keywords
data
transmission cycle
network device
transmission
communication medium
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PCT/DE2023/200240
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German (de)
English (en)
Inventor
Helge ZINNER
Daniel HOPF
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Continental Automotive Technologies GmbH
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Publication of WO2024125731A1 publication Critical patent/WO2024125731A1/fr

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Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L43/00—Arrangements for monitoring or testing data switching networks
    • H04L43/08—Monitoring or testing based on specific metrics, e.g. QoS, energy consumption or environmental parameters
    • H04L43/0876—Network utilisation, e.g. volume of load or congestion level
    • H04L43/0888—Throughput
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L12/00—Data switching networks
    • H04L12/28—Data switching networks characterised by path configuration, e.g. LAN [Local Area Networks] or WAN [Wide Area Networks]
    • H04L12/40—Bus networks
    • H04L12/407—Bus networks with decentralised control
    • H04L12/413—Bus networks with decentralised control with random access, e.g. carrier-sense multiple-access with collision detection [CSMA-CD]
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L43/00—Arrangements for monitoring or testing data switching networks
    • H04L43/08—Monitoring or testing based on specific metrics, e.g. QoS, energy consumption or environmental parameters
    • H04L43/0876—Network utilisation, e.g. volume of load or congestion level
    • H04L43/0894—Packet rate
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L43/00—Arrangements for monitoring or testing data switching networks
    • H04L43/50—Testing arrangements

Definitions

  • the present invention relates to communication over a communication medium shared by multiple network devices, in particular to monitoring the integrity of the communication.
  • communication medium is used to refer to wireless, wired or other media-based transmission media, i.e. synonymously to acoustic signals, light waves, radio waves or electrical signals transmitted via electrical conductors, unless the context necessarily requires a specification of one of these communication media.
  • IP Internet Protocol
  • Each of these subsystems uses its own hardware interface with different EMC behavior and uses different software stacks.
  • a consistently Ethernet-based network architecture offers many advantages because it always works with the same protocol regardless of the physical layer.
  • a data frame always looks the same regardless of whether it is transmitted at 10 Mbit/s or 10 Gbit/s. Scaling the bandwidth for specific applications does not require complex gateways.
  • a single switch can often be equipped with the appropriate interfaces that enable communication at different speeds. The data frames can then switch from one domain to another without modifying the data by buffering it accordingly.
  • an electrical Ethernet connection that is implemented as a point-to-point connection between two network devices or a network device and a switch with one line requires a dedicated physical interface at each end of the line, generally referred to as a PHY, which is responsible for encoding and decoding data between the digital side of the system and a propagation or transmission medium.
  • a switch requires a separate PHY for each network device connected to it, so that a large number of connections are required in a network.
  • An example system 10 with four network devices 12, 14, 18, and 20 connected via a switch 16 is shown in Figure 1. A total of 8 physical interfaces are required for the four point-to-point connections so that all five network devices can communicate with each other.
  • Ethernet systems are known in which a bus topology is used (10BASE2, 10BASE5).
  • a coaxial cable 22 connects the five network devices 12, 14, 16, 18 and 20.
  • Each of the network devices 12, 14, 16, 18 and 20 is connected to the coaxial cable 22 via a spur line and a connection box 12a, 14a, 16a, 18a and 20a.
  • the outer conductor of the coaxial cable 22 is interrupted at certain points in the connection boxes 12a, 14a, 16a, 18a and 20a, and a contact pin is inserted into the connection box 12a, 14a, 16a, 18a and 20a.
  • 10BASE-T1 S One of the variants specified under this IEEE standard is called 10BASE-T1 S, where the S stands for Short Reach, and can use a multidrop or bus topology in which all nodes are connected via a single two-wire twisted pair cable. This eliminates the need for switches, i.e. the number of physical interfaces is smaller than in a system with one switch, and no coaxial cable is required. Connecting spur lines to a twisted pair cable can also be implemented passively, easily and inexpensively.
  • a long-range variant - called 10BASE-T1 L (L for Long Reach) - has been defined for distances of up to 1 km. The long-reach variant uses point-to-point connections.
  • At least eight network devices can be connected to one another via a 10BASE-T1 S bus system, with the maximum bus length being 25 m.
  • the individual network devices can be connected to the bus line using spur lines that are no more than 10 cm long. All nodes share the bandwidth of 10 Mbit/s.
  • Figure 3 shows a corresponding example of a 10BASE-T 1 S network with five network devices 12, 14, 16, 18, 20 connected via a shared communication medium 24, e.g. a bus line formed by a twisted pair of wires.
  • the dashed line indicates the logical connections between the network devices, the solid line indicates the physical connections.
  • the standard specifies an arbitration scheme that enables full utilization of the available bandwidth with reduced latency and high Quality of Service (QoS).
  • QoS Quality of Service
  • One of the possible arbitration schemes is known as Physical Layer Collision Avoidance - PLCA
  • another arbitration scheme known as Carrier Sense Multiple Access/Collision Detection - CSMA/CD
  • the CSMA/CD access method allows every network device to access the network and send data as soon as no other network device is sending data.
  • a regulation that ensures that each of the network devices in a network has the opportunity to send data within a specified period of time is not included in the CSMA/CD access method and must be implemented at a higher protocol level.
  • the PLCA access method is conceptually similar to a token ring method or TDMA (Time Division Multiple Access).
  • each network device is configured with a node ID, and the network device with node ID 0 is designated as the PLCA coordinator.
  • the coordinator initiates a communication cycle by sending an agreed sequence of data bits or octets, also called a beacon message or a beacon frame.
  • the other nodes use this beacon message to coordinate their clocks.
  • beacon message and beacon frame are used synonymously in this description.
  • each network device In order to determine when it is allowed to send data in the PLCA access procedure, each network device "listens" on the bus line and waits until the network device with a node ID one lower than its own completes the transmission. After each transmission process by a network device, which can be marked as completed by an agreed sequence of data bits or octets at the end of a transmission, there follows a period known as the transmit opportunity or TO time window.
  • the TO time window can be 20 bits long, for example, i.e. it can correspond to a period of time within which 20 bits can be sent at the nominal data rate of the data bus.
  • the network device whose node ID is one higher than that of the network device that has just completed its transmission can begin transmission.
  • Each node can send all of its data, although each network device typically only sends one frame. However, a network device can send several consecutive data frames in what is known as burst mode, with commit messages sent between the respective data frames marking the communication medium as still occupied by the network device currently sending. If a network device does not send and allows the TO time window reserved for it to expire, another TO time window follows for the next network device. In this way, even in a cycle in which not all network devices are sending, the coordinator can determine or assume the end of the cycle and start a new cycle.
  • the PLCA coordinator After the last network device has received and, if necessary, used the opportunity to transmit data, the PLCA coordinator initiates the next cycle with another beacon message.
  • Access using PLCA achieves a higher throughput than TDMA or Token Ring because the network devices do not have to split their messages into multiple time slots.
  • the transmit opportunity phase with its 20 bits is shorter than a token packet. Since the participants on the bus may or may not take advantage of their opportunity to transmit, the duration of a complete transmission cycle cannot be determined exactly in advance.
  • FIG 4. An example of the messages sent by network devices in the order of their node IDs over the shared communication medium is shown in Figure 4.
  • the start of a transmission cycle is initiated with a corresponding bit sequence B, also known as a beacon.
  • a TO time window within which the network device with the lowest node ID can start sending its message, in this case the node ID with the value 0, which also sent the beacon bit sequence.
  • the TO time window is hatched in the figure.
  • the end of transmission by a network device is followed by the T0 time window for the next network device.
  • the network device that is allowed to transmit can start transmitting immediately at the beginning of the TO time window or at any time within the TO time window.
  • the TO time window can be started, for example, by a signal representing the end of a transmission by a network device.
  • This signal can be, for example, an end-of-frame signal (EOF).
  • EEF end-of-frame signal
  • the end of a TO time window can be determined by a counter or timer.
  • the end of the TO time window is reached when the network device that is allowed to transmit has not started a transmission during an agreed time, corresponding to an agreed number of data bits sent at the nominal data rate of the shared communication medium.
  • SOF start-of-frame signal
  • the counter for the TO time window can be stopped. This process repeats until the last network device has sent its message or allowed its TO time window to expire.
  • a new beacon bit sequence is then sent, which begins a new transmission cycle.
  • the length or duration of each transmission cycle is determined by the length of the beacon bit sequence, the length of the messages sent by the network devices, or the TO time windows that are completely or partially unused, and can vary from transmission cycle to transmission cycle.
  • FIG. 6 An example representation of the error in the sequence of messages sent by the network devices in the order of their node IDs over the shared communication medium is shown in Figure 6.
  • the representation essentially corresponds to the representation in Figure 4, except that the message from Node 2 is disturbed.
  • This disturbance can consist, for example, in Node 2 not sending at all, sending incompletely, or sending random bit sequences due to a disturbance in the connection between the processor and the network interface.
  • Such an error is not recognizable at the access control level in normal operation and would have to be recognized at higher protocol levels.
  • the individual network devices provide little computing power and memory and also have to be particularly cost-effective, such capabilities cannot always be available.
  • Figure 7 shows the network from Figure 3 with an error affecting the bus line 24, for example a temporary disturbance triggered by an electromagnetic interference pulse.
  • the physical connection between the network interface and the bus line 24 is not disturbed.
  • the disturbance is shown as local in the figure, it occurs at all interfaces almost simultaneously due to the short length and low attenuation of the bus line and thus disturbs the correct reception of data bits or octets of a message, for example by changing a signal level in such a way that the value of one or more data bits is changed, or by a voltage level being applied to the receivers of the interfaces which overrides them.
  • An example representation of the error in the sequence of messages sent by the network devices in the order of their node IDs over the shared communication medium is shown in Figure 8.
  • the representation essentially corresponds to the representation in Figure 4, except that in the exemplary representation in Figure 8 the beacon bit sequence is disturbed, for example by an electrical or electromagnetic interference pulse at the time when the Coordinator has sent the beacon bit sequence.
  • the network devices with node IDs greater than 0 cannot therefore recognize the start of a new transmission cycle and will not send their messages.
  • the coordinator will therefore only recognize TO time slots that are not being used by the other network devices and will begin a new transmission cycle when the number of elapsed, unused TO time slots corresponds to the number of network devices connected via the shared communication medium.
  • the transmission cycle x+1 shown in Figure 8 is very short, but for the other network devices, the transmission cycle x is longer than for the coordinator.
  • Such a change cannot be reliably recognized on OSI layers 1 and 2 of the communication connection during normal operation and would have to be recognized and, if necessary, corrected at higher protocol levels, as in the error example described with reference to Figure 5.
  • a network of the type described above in which a large number of network devices are connected to one another via a shared communication medium, is used in a system that places high demands on the reliability and security of communication, e.g. in a system with several network devices that communicate with one another in connection with partially or highly automated driving, frequent, ideally continuous, integrity checks of the communication are essential.
  • the term network device includes all possible types of network devices, including networked sensors and network devices that process signals from networked sensors.
  • a method for monitoring the integrity of communication between a plurality of network devices connected via a shared communication medium which can each send a message via the shared communication medium within a transmission cycle initiated and terminated by a first network device, also referred to as a coordinator, comprises listening to at least certain parts of the communication on the communication medium within the transmission cycle.
  • the message sent by the respective network device can have any length, ie comprise one or more Ethernet frames, whereby the length of the or the Ethernet frames can be between 64 and 1518 bytes. Sending so-called jumbo frames with a longer length is also possible in principle, although in this case all of the network devices connected via the communication medium must support these jumbo frames. If a network device sends several consecutive frames, which is also known as burst mode, the network device can send a commit signal after a sent frame to signal to the other network devices that another frame is following.
  • the start of a transmission cycle is marked by a sequence of data bits.
  • the end of a transmission cycle can be represented, for example, by a sequence of data bits that mark the start of a subsequent transmission cycle.
  • the end of a transmission cycle can also be represented by a sequence of data bits that mark the end of the transmission of the last network device. The latter may require that all network devices that carry out the process know at least the number of network devices in the network, for example through appropriate parameterization or through independent learning during operation.
  • Listening accordingly includes at least the detection and/or evaluation of data bits or sequences of data bits that mark the beginning and end of a transmission cycle, and of data bits or sequences of data bits or octets that mark the beginning and end of a transmission by a network device.
  • the start of a transmission by a network device can already be recognized by the fact that a first data bit is sent within a TO time window.
  • the protocol used can ensure that only a network device that is actually currently sending is sending.
  • Listening also includes the detection and/or evaluation of a transmission option not used by a network device within a transmission cycle. If at least one of the network devices in the network transmits messages in burst mode, listening also includes the detection and/or evaluation of sequences of data bits that represent commit signals.
  • Network devices that also send messages in burst mode can do this, for example, when initializing the network. or, if the number and type of network devices of the system using the network is known from the outset and remains unchanged, a corresponding configuration can be made in advance in the network devices.
  • Each network device in the network is assigned a unique node ID, usually a number within an interval starting with 0 and ending with the number n of network devices in the network.
  • the network device with the lowest node ID i.e. node ID 0
  • the network device with the lowest node ID is the first network device, i.e. the coordinator, which initiates the transmission cycle and is also the first to transmit its data.
  • Each network device implements a node ID counter, which is reset to 0 at the beginning of each transmission cycle.
  • the node ID counter can be a simple counter implemented in software.
  • a network device does not necessarily have to send within a transmission cycle.
  • the detection and evaluation of a transmission option not used by a network device can therefore include, for example, the detection and evaluation of a TO time window.
  • a TO time window has a predetermined period of time, e.g. the period that would have been required to transmit a predetermined number of data bits at the nominal data rate of the shared communication medium.
  • a TO time window follows the end of a transmission, e.g. a sequence of data bits representing the end of a data frame. As soon as no data bits are detected during the entire duration of a TO time window, i.e.
  • each network device increases the node ID counter and waits during a new TO time window to see whether data bits are received, or sends its own data bits. Transmission over the communication medium if the value of the node ID counter corresponds to its node ID.
  • a network device can also send a commit message during the TO time window if, for example, the network device is not yet ready to send the message but will be shortly. In this case, the other network devices wait beyond the end of the TO time window until the network device that sent the commit signal has sent its message. In the following TO time window, the next network device whose node ID matches the counter value can then send.
  • the method also comprises determining the duration of a transmission cycle.
  • the duration of a transmission cycle can be determined, for example, by measuring the time elapsed between two consecutive sequences of data bits identifying the start of a transmission cycle. If the end of a transmission cycle is signaled by a sequence of data bits that marks the end of the transmission of the last network device, the time elapsed between the start of the transmission cycle and this sequence can be measured. Since the length of the transmission cycles can vary depending on the number of network devices that actually transmit data and the number of data bits or octets sent by each network device, the duration of each individual transmission cycle is determined individually.
  • the amount of data transmitted within the transmission cycle is determined, and the amount of data expected within the transmission cycle is calculated.
  • the determined amount of data is then compared with the calculated amount of data.
  • a data rate can be determined from the measured duration of the transmission cycle and the amount of data transmitted via the communication medium during the transmission cycle, which is compared with a nominal data rate of the network. If the determined and calculated amount of data or the determined and nominal data rate match within a tolerance window, the method is repeated for a subsequent transmission cycle. Otherwise, at least one of the network devices that carried out the method goes into error mode. In error mode, a network device can take different measures depending on the type and severity of the error.
  • information relating to the error can be stored locally in the network device, in an audit-proof storage device that is communicatively connected to the network device, and/or in a cloud.
  • the log level i.e. the amount of data and level of detail of the information stored, can also be tightened on a case-by-case basis so that additional data is available for troubleshooting.
  • the network device can stop its own communication via the shared communication medium, or the network device with the lowest node ID, which has the role of coordinator, can be notified so that it can prevent further communication on the data bus if necessary.
  • CSMA/CD Carrier-Sense Multiple Access/Collision Detection
  • communication no longer takes place in cycles initiated by a coordinator, and no beacon frames are sent. Instead, all network devices listen for possible communication on the communication medium and try to send if no other network device is currently sending. If collisions occur, the network devices wait a certain amount of time with randomly generated waiting times before they try to send again.
  • the method is carried out for each transmission cycle, continuous or quasi-continuous monitoring of the integrity of the communication is possible.
  • the new transmission cycle is already monitored and the amount of data transmitted in the new transmission cycle is started to be determined, while the expected amount of data for the previous cycle is calculated and the determined and expected amount of data for the completed transmission cycle are compared.
  • random monitoring may also be sufficient, which is carried out cyclically on a regular basis or at irregular intervals.
  • the method can also be carried out over several transmission cycles, i.e. the determination of the amount of data transmitted and the calculation of the expected amount of data can take place over several transmission cycles.
  • the method can also be carried out for a shorter period of time than one transmission cycle, even over parts of two consecutive transmission cycles. It would be possible, for example, to monitor the integrity of the communication for only a selection of network devices. In this case, the "shortened transmission cycle" could be determined using the node ID counter. In principle, it is therefore possible to start and end the determination of the amount of data transmitted within a transmission cycle, or to start within a first transmission cycle and end it within a subsequent transmission cycle, i.e. not necessarily at the beginning and at the end.
  • determining a data volume or data rate transmitted within a transmission cycle includes counting all data bits or octets transmitted via the communication medium within a transmission cycle, possibly including those transmitted by a network device carrying out the method itself, provided that it sends a message within the transmission cycle. This embodiment could be used, for example, on layer 1 of the OSI layer model if the network device carrying out the method is not set up to evaluate the communication on a higher layer of the OSI layer model.
  • determining an amount of data transmitted within a transmission cycle or the data rate comprises detecting the start and end of a transmission of a network device.
  • the amount of data sent by a respective network device can be calculated by multiplying the time period between the start and end of the transmission by the nominal data rate of the shared communication medium.
  • the calculated data amounts of all network devices that have transmitted during a transmission cycle are summed up.
  • determining a data volume or data rate transmitted within a transmission cycle comprises evaluating information contained in transmissions of a transmission cycle about the number of data bits or octets transmitted in the respective transmission, possibly including those transmitted by a network device carrying out the method itself, provided that it sends a message within the transmission cycle.
  • the number of data bits or octets can be corrected by the data bits or octets required for the communication protocol, including the number of data bits or octets that are sent to initiate and possibly to end a transmission cycle.
  • the network interface of a device using the method executing network device is put into a special operating mode in which the contents of transmissions not sent to the network device are also evaluated.
  • This operating mode is also known as "promiscuous mode”. Determining the number of data bits or octets transmitted can then include evaluating information transmitted in higher protocol layers about the amount of data sent in a transmission.
  • the method used to determine the amount of data transmitted within a transmission cycle or the data rate or the type of data recorded for this purpose can be selected, for example, depending on the number of network devices connected to one another via the shared communication medium, the maximum duration of the TO time window and/or the duration of the sequence of data bits or octets characterizing the start and end of the transmission cycle.
  • one method may dispense with explicitly recording one or more signal components, for example the sequence of data bits or octets characterizing the start and end of a transmission cycle, the duration of unused TO time windows or commit signals, while another method explicitly records one or more of these signal components.
  • determining a data volume or data rate transmitted within a transmission cycle comprises replacing a period of a TO time window or a the transmission opportunity not used by a network device by the number of data bits or octets that could be transmitted during the elapsed time period or the duration of a TO time window.
  • the number of bits that could theoretically have been sent before the network device actually started transmitting or the number of data bits or octets that could be transmitted during a TO time window can be calculated, for example, from the nominal transmission speed of the shared communication medium and the elapsed time.
  • This number can also correspond to a predetermined number of data bits that is taken into account as a representative of the unused transmission opportunity for determining the amount of data transmitted within a transmission cycle, because no data bits or octets are sent during an unused TO time window.
  • the node IDs are permanently assigned to the network devices before or when the system is put into operation.
  • the node IDs it is also possible for the node IDs to be reassigned during operation, for example cyclically at fixed time intervals, in order to allow access to new network devices that have been added to the network, or in order to maintain a continuous series of node IDs, for example if a network device has been removed from the network.
  • the latter can be announced by the network device in a corresponding message, but it can also be assumed, for example, if a network device has not used a predetermined number of TO time slots of consecutive transmission cycles.
  • At least the network device executing the method can also switch to an error mode.
  • the predetermined value may be different for each network device and may be announced via broadcast messages when the system is started up or may be stored in a memory accessible to the network device executing the procedure.
  • calculating an amount of data expected within a transmission cycle comprises multiplying the cycle duration by the nominal data rate of the communication medium. This embodiment may This can be used especially when transmission cycles follow one another immediately without any major delay.
  • a network device comprises one or more processors, volatile and non-volatile memory associated with it or these, and a physical network interface communicatively connected to the one or more processors and configured to send and/or receive via a communication medium shared by multiple network devices.
  • the elements of the network device are communicatively connected to one another by means of one or more data lines or buses.
  • Computer program instructions are stored in the non-volatile memory which, when executed by the at least one processor, configure the network device to carry out one or more embodiments of the method according to the invention.
  • a system in particular a vehicle system, comprises two or more network devices networked via a communication medium shared by several network devices.
  • at least one of the network devices is set up to carry out at least one embodiment of the method according to the invention described above.
  • a computer program product contains instructions which, when executed by a computer, cause the computer to carry out one or more embodiments and further developments of the method described above.
  • the computer program product can be stored on a computer-readable medium or data carrier.
  • the medium or data carrier can be physically embodied, for example as a hard disk, CD, DVD, flash memory or the like, but the medium or data carrier can also comprise a modulated electrical, electromagnetic or optical signal that can be transmitted by a computer by means of a corresponding receiver and stored in the computer's memory.
  • the method described above and the network devices executing the method can advantageously be implemented without changes to existing hardware and can be integrated into existing networks accordingly, since the protocols already used do not have to be changed and the function of the network is not impaired by higher usage or latencies.
  • the operational reliability of systems e.g. sensor networks and control units that control and execute actions based on sensor data
  • systems e.g. sensor networks and control units that control and execute actions based on sensor data
  • Errors can be detected quickly and appropriate measures can be taken more quickly to restore safe operation or to switch to a safe operating mode.
  • the method described above and the network devices executing the method can be used platform-independently and therefore flexibly due to the simple and lean implementation.
  • Fig. 1 shows an exemplary network known from the prior art with four network devices connected via a switch
  • Fig. 2 shows an exemplary network known from the prior art with five network devices connected via a 10BASE2 or 10BASE5,
  • Fig. 3 shows an exemplary network known from the prior art with five network devices connected via a twisted pair of wires
  • Fig. 4 is an example of messages sent by network devices in the order of their node IDs over the shared communication medium
  • Fig. 5 the network from Figure 3 with a fault in the network interface of a network device
  • Fig. 6 is an exemplary representation of an error in a network device in the sequence of messages sent by the network devices in the order of their node IDs over the shared communication medium
  • Fig. 7 the network from Figure 3 with a fault affecting the bus line
  • Fig. 8 is an exemplary representation of a transient disturbance affecting the bus line in the sequence of messages sent by the network devices in the order of their node IDs over the shared communication medium
  • Fig. 9 is a schematic flow chart of the basic procedure of the method.
  • Fig. 10 is an exemplary schematic flow diagram of monitoring the communication on the shared communication medium
  • Fig. 11 is an exemplary schematic flow chart for selecting one of two options for determining the amount of data transmitted over the shared communication medium during a transmission cycle depending on parameters of the shared communication medium and the network,
  • Fig. 12 is an exemplary schematic flow diagram of an alternative method for selecting one of two measurement methods for determining the amount of data transmitted over the shared communication medium during a transmission cycle depending on parameters of the shared communication medium and the network when at least one network device sends messages in burst mode,
  • Fig. 13 is an exemplary schematic flow diagram for determining the integrity of communication during a transmission cycle
  • Fig. 14 shows a first part of an exemplary schematic flow diagram of a method for determining the data bits or octets sent within a transmission cycle on the physical layer
  • Fig. 15 shows a second part of an exemplary schematic flow diagram of a method for determining a data volume transmitted within a transmission cycle on the physical layer
  • Fig. 16 is an exemplary block diagram of a network device configured to carry out one or more aspects of the method according to the invention.
  • Figure 9 shows a schematic flow diagram of the basic sequence of the method 100.
  • step 110 the communication on the shared communication medium is listened to or monitored, whereby at least sequences of data bits or octets are detected and evaluated, which mark the start and end of a transmission by a network device, and transmission options not used by network devices within a transmission cycle are detected and evaluated.
  • step 120 the determination of its duration begins in step 120. For this purpose, for example, the time elapsed between two consecutive sequences of data bits representing the start of a transmission cycle can be measured.
  • step 130 the amount of data transmitted during the transmission cycle via the shared communication medium is determined, for example by counting the data bits or octets transmitted via the shared communication medium or in another way.
  • Data from the monitoring in step 110 can also be used here, as indicated by the separate arrow, for example special sequences of data bits or octets detected during the monitoring, which serve to control the transmission.
  • step 140 an expected amount of data within the transmission cycle is calculated. This can be based on the duration of the transmission cycle and the nominal data rate of the shared communication medium as well as the number of network devices connected via it. For this purpose, the duration of the transmission cycle determined in step 120 is supplied, as indicated by the arrow.
  • step 150 the integrity of the communication via the shared communication medium is checked.
  • the integrity is determined, for example, by comparing the calculated expected data volume with the data volume determined by monitoring the communication. It is also possible to calculate a data rate from the data volume determined by monitoring the communication and the duration of the transmission cycle, which is then compared with the nominal data rate of the shared communication medium.
  • a tolerance range can be used to suppress measurement inaccuracies that are unavoidable due to the lack of synchronization between the network devices and possibly slightly differing transmission data rates of different network devices when determining the integrity.
  • Figure 10 shows an example of a schematic flow diagram of listening in or monitoring, in step 110, the communication on the shared communication medium.
  • step 110 the communication on the shared communication medium.
  • Network devices that can be operated in so-called promiscuous mode can listen in not only to the address data of data packets not addressed to them, but also to the other content of the transmissions, or at least count the number of data bits or octets of transmissions not addressed to them.
  • step 111 data from a transmission is received accordingly, and in step 112 the length of the transmission is determined or extracted, i.e. the number of data bits or octets.
  • a network device executing the method can also evaluate the content of transmissions not addressed to the network device, for example information about the length of a transmission contained in a header, counting all data bits or octets of the transmission is not necessary. In this case, it is sufficient if the network device can determine the end of a transmission, for example by receiving a signal representing the end of a data frame (EOF) or another signal agreed in a protocol used. If the transmission is directed to the network device executing the method, which is determined by a check in step 113, the received data bits or octets are also forwarded for further processing in higher protocol layers in step 114.
  • EEF end of a data frame
  • the data not required to determine the amount of data transmitted can be discarded in step 115, provided they are not used for other purposes by the network device executing the method.
  • the listening or monitoring of the communication on the shared communication medium is repeated at least until a signal representing the end of a transmission cycle is received, i.e. a corresponding sequence of data bits.
  • Figure 11 shows an example schematic flow chart for selecting one of two options for determining, in step 130, the amount of data transmitted during a transmission cycle via the shared communication medium depending on parameters of the shared communication medium and the network.
  • the number of network devices connected via the shared communication medium is determined, in step 1302 the number of data bits or octets in the sequence of data bits representing the start of a transmission cycle and possibly the end of a transmission cycle, and in step 1303 the number of data bits or octets that correspond to the TO time window.
  • This information about the parameters of the protocol used for communication also referred to as signal components, can be read out, for example, from a configuration file that is accessible locally or via the network to all network devices carrying out the method.
  • step 1305 it is checked whether the total number of data bits or octets of the signal components, which results from the sum of the number of data bits or octets in the sequence of data bits representing the start of a transmission cycle and, if applicable, the end of a transmission cycle and the product of the number of network devices connected via the shared communication medium and the number of data bits or octets representing the TO time window, plus a measurement inaccuracy, is equal to or greater than the number of data bits or octets of the shortest possible transmission of a network device, e.g. the shortest length of a data frame.
  • the number of data bits or octets of the signal components is recorded in step 1306, in addition to determining the number of data bits or octets transmitted in the messages of the network devices in step 1307.
  • Figure 12 shows an exemplary schematic flow diagram of an alternative method for selecting one of two measurement methods for determining, in step 130, the amount of data transmitted over the shared communication medium during a transmission cycle as a function of parameters of the shared communication medium and the network when at least one network device sends messages in burst mode.
  • Steps 1301, 1302 and 1303 correspond to those described with reference to Figure 11.
  • step 1304 the number of network devices that send several consecutive data frames in burst mode in a message is determined.
  • At least one network device transmits in burst mode, a larger number of data bits or octets for signal components can occur within a transmission cycle, among other things because in burst mode a network device can send up to 255 data frames in succession, and a commit signal is sent for each sent data frame, which tells the other network devices in the network that the network device currently actively accessing the communication medium will send further data frames.
  • the more network devices send additional data bits or octets for signal components the more likely it is that the number of data bits or octets in the shortest possible message from a network device will be reached or exceeded simply by the sum of the data bits or octets of the signal components, so that it becomes necessary to also record the data bits or octets of the signal components and to include them in the calculation of the number of data bits or octets transmitted or the data rate for a transmission cycle.
  • step 1305 when determining the number of data bits or octets for signal components, the sum described with reference to step 1305 in Figure 11 is the product of the number of network devices transmitting in burst mode, the number of data bits or octets of the additional TO time slots and the maximum number of data packets in burst mode, i.e. 255, is added.
  • step 1306 in addition to determining the number of data bits or octets transmitted in the messages of the network devices in step 1307, the number of data bits or octets of the signal components is recorded.
  • FIG. 13 shows an example schematic flow diagram of the steps of a method 150 for determining the integrity of communication during a transmission cycle.
  • a "real bus load" is first determined by subtracting the number of data bits or octets actually transmitted via the shared communication medium from the number of data bits or octets that can be transmitted at the nominal data rate during the duration of the transmission cycle.
  • step 152 it is checked whether the real bus load is a positive number. If this is not the case, i.e.
  • step 156 in which this error is signaled and/or treated differently.
  • Such an error can arise, for example, because the end of a transmission cycle was not recognized.
  • the method follows the "yes" branch and next checks, in step 153, whether the number representing the real bus load is greater than the number of data bits or octets of the shortest possible transmission of a network device, e.g. the shortest length of a data frame.
  • step 154 the method follows the "no" branch to step 154, which may, for example, include waiting for the determination of the integrity of the communication for the next transmission cycle. If the number representing the real bus load is greater than the number of data bits or octets of the shortest possible transmission of a network device, at least one data frame has been lost and the method follows the "yes" branch to step 155. In step 155, this second type of error is signaled and/or treated differently.
  • Figure 14 shows a first part of an exemplary schematic flow diagram of a method 1100 for listening and a method 1300 for determining the data bits or octets sent within a transmission cycle on the physical layer, i.e. layer 1 of the OSI layer model.
  • This method can be used, for example, if a network device executing the method according to the invention does not support listening to communication on layer 2 that is not intended for the network device itself, i.e. the layer 2 frames cannot be analyzed.
  • those data bits or octets that are used for signaling are also directly recorded, i.e., the sequences of data bits or octets that signal the start of a transmission cycle (beacon), the start (SOF) or the end of a transmission (EOF), and the sequences of data bits or octets that signal a further assignment (commit).
  • an initialization of the network device executing the method can take place before the start of the method, in which, for example, the number of data bits or octets of a message identifying the start or end of a transmission cycle, the number of network devices and their properties and the like are read from a database (not shown in the figure).
  • step 1101 it is checked whether a sequence of data bits or octets characterizing the start of a new transmission cycle has been received. If this is not the case, the "no" branch of step 1101 is branched off and the test is repeated.
  • step 140 branches off into the "yes" branch to the methods represented by steps 140 and 150, in which the amount of data expected within the previous transmission cycle is calculated and the integrity of the communication for the previous cycle is checked.
  • a flow chart of an exemplary method 150 which is used in the analysis on the Layer 1 of the OSI layer model is described below with reference to Figure 15. The number of data bits or octets that could have been sent while waiting for a sequence of data bits or octets indicating the start of a new transmission cycle is determined in step 1301a and taken into account accordingly when checking the integrity of the communication, indicated by the dashed arrow from step 1301a to step 140.
  • step 1102 In parallel to checking the integrity of the communication, in step 1102, respective counters for the network device that is allowed to send next, for the TO time slots not used by network devices and for the number of data bits or octets transmitted during the current transmission period, and in step 1103 a timeout counter for the current TO time slot are reset and started. In step 1104, it is checked whether all network devices had the opportunity to send in the current transmission cycle, i.e. whether the counter for the network device that is allowed to send next has reached a value that corresponds to the last network device in the group of network devices connected via the shared communication medium. If this is the case, i.e.
  • step 1104 if all network devices had the opportunity to transmit a message during the current transmission cycle, the method follows the "yes" branch from step 1104 back to step 1101, in which it waits for the start of the next transmission cycle. Otherwise, the method follows the "no" branch from step 1104 to step 1301, in which all data bits or octets sent on the shared communication medium are received and counted.
  • Received sequences of data bits or octets are checked in step 1302 to see whether they mark the beginning of a transmission by a network device, for example, form a start-of-frame signal or the like. If this is the case, the method follows the "yes" branch of step 1302 and waits, in step 1303, for a sequence of data bits or octets that mark the end of a transmission by a network device.
  • the received data bits or octets are checked in step 1304 to see whether, instead of a sequence of data bits or octets that marks the end of the transmission, there is a sequence of data bits or octets that marks the beginning of a new transmission cycle.
  • step 1305 for example, the network device executing the method can be put into an error mode and/or the network device can announce the detected error via the network.
  • step 1303 If a sequence of data bits or octets is received in step 1303 that indicates the end of a transmission by a network device, "yes" branch of step 1303, the counter for the network device that is allowed to send next is incremented in step 1306 and the method continues with step 1104.
  • step 1104 checks whether all network devices have had the opportunity to send in the current transmission cycle. If this is not the case, the part of the method beginning with step 1301 is continued for the next network device.
  • step 1302 If the check in step 1302 does not find a sequence of data bits or octets that indicates the start of a transmission by a network device, the method follows the "no" branch of step 1302 and checks in step 1307 whether a received sequence of data bits or octets indicates the start of a transmission cycle. If this is the case, "yes" branch of step 1304, an error must be present because not all network devices connected via the shared communication medium have had the opportunity to send a message or at least to allow their respective TO time windows to elapse, and the method continues with step 1305. As already described above, in step 1305, for example, the network device executing the method can be put into an error mode and/or the network device can announce the detected error via the network.
  • step 1308 If no sequence of data bits or octets marking the start of a transmission cycle was detected in step 1307 (“no” branch of step 1304), a check is made in step 1308 as to whether the timeout counter for the current TO time window has expired. If this is not the case (“no” branch of step 1308), while the shared communication medium is unused, i.e. idle, reception or waiting continues until a data bit marking the start of a transmission or a sequence of data bits or octets marking the start of a transmission is detected. was, that is, whether the network device started sending until the timeout counter expired.
  • step 1308 the counter for the TO time slots not used by network devices is incremented in step 1309 and the method continues with step 1308.
  • step 1301 All data bits or octets received in the meantime, including the sequences of data bits or octets indicating the beginning or end of a transmission, are counted by step 1301, which runs in parallel with the checks of the received data bits or octets.
  • the number of data bits or octets that could have been sent by a network device between the beginning of the TO time window and the beginning of the transmission is either added to the number of data bits or octets sent over the shared communication medium at this point, or later when checking the integrity of the communication.
  • Data bits or octets intended for the network device executing the procedure are forwarded to higher protocol layers (not shown in the figure).
  • the amount of data sent by a network device that is currently permitted to access the shared communication medium or determined for this network device using the method described above is added to the amount of data that has already been sent by or determined for other network devices during the current transmission cycle.
  • Figure 15 shows an exemplary flow chart of the steps for determining the duration of a transmission cycle and for checking the integrity of the communication for a transmission cycle.
  • the time is calculated which has elapsed between the reception of a sequence of data bits or octets characterizing the beginning of a transmission cycle and the reception of a sequence of data bits or octets characterizing the end of a transmission cycle.
  • the end of a transmission cycle can be can also be signaled by the start of a subsequent transmission cycle.
  • a timer can be used for the calculation, which is started at the start of a transmission cycle and stopped at the end of a transmission cycle.
  • step 140 an expected data volume within the transmission cycle is calculated. This can be done, for example, on the basis of the duration of the transmission cycle and the nominal data rate of the shared communication medium.
  • step 150 the amount of data transmitted during the transmission cycle via the shared communication medium, determined in step 130, which runs parallel to determining the duration of the transmission cycle, is compared with the expected amount of data calculated in step 140. If the data bits or octets that could theoretically be transmitted during an unused TO time window were not already taken into account when determining the transmitted data bits or octets, these are determined in step 1399 by multiplying the number of network devices that did not transmit by the number of data bits or octets that could theoretically be transmitted during a TO time window and added to the data bits or octets actually received.
  • the network device may enter various error modes of operation.
  • the possible error modes may include using a different method for accessing the shared communication medium, e.g. CSMA/CD, enhanced logging of communications over the shared communication medium, placing the system in safe mode, sending one or more messages to a remote system, or the like.
  • Figure 16 shows an exemplary block diagram of a network device 400 configured to carry out one or more aspects of the method according to the invention.
  • the network device 400 comprises volatile and non-volatile memory 404, 406 and a communication interface 408.
  • the elements of the network device are communicatively connected to one another via one or more data connections or buses 410.
  • the non-volatile memory 406 contains computer program instructions which, when executed by the microprocessor 402, configure the network device to carry out at least one embodiment of the method according to the invention.
  • Network device 406 non-volatile memory
  • Connection box 1300 determine the amount of data sent

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Abstract

Un procédé de surveillance de l'intégrité de la communication entre de multiples dispositifs de réseau, connectés via un support de communication partagé, qui sont chacun capables de transmettre un message via le support de communication partagé dans un cycle de transmission déclenché par un premier dispositif de réseau comprend l'espionnage sur au moins certaines parties de la communication sur le support de communication dans un cycle de transmission. L'espionnage comprend au moins la détection et l'évaluation de bits de données ou d'octets qui marquent le début et la fin du cycle de transmission et le début et la fin d'une transmission par un dispositif de réseau. L'espionnage comprend également la détection et l'évaluation d'une opportunité de transmission qui n'est pas utilisée par un dispositif de réseau dans un cycle de transmission. Selon l'invention, la durée d'un cycle de transmission est déterminée et un volume de données transmises dans le cycle de transmission ou un débit de données obtenues pour le cycle de transmission est déterminé. En comparant un volume de données attendues dans le cycle de transmission ou le débit de données nominal au volume de données transmis, ou au débit de données obtenu, l'intégrité de la communication sur le support de communication peut être surveillée.
PCT/DE2023/200240 2022-12-13 2023-12-01 Procédé de test d'un bus de communication WO2024125731A1 (fr)

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