Method for configuring a communication network for cyclically transmitting messages

Abstract

The invention describes a method for configuring a communication network with industrial real-time capability, the communication network being used for cyclic transmission of messages (NWM), each of which includes one or more data sets (DS1, ..., DS4). The communication network (1) has a message source (10) for generating and cyclically transmitting messages (NWM), at least one message receiver (16, 17, 18) for receiving and processing the messages (NWM), and at least one network component (12, 14) for forwarding the messages (NWM) from the message source to the message receiver. The configuration includes determining (S1) a network topology of the communication network (1), the communication network being used for transmitting a data stream to be sent by the message source (10), wherein the messages (NWM) with all data sets are respectively cyclically transmitted. It is determined (S2) which data sets in the data stream a corresponding one of the message receivers wants to receive. Furthermore, by determining from the network topology the components connected to the corresponding network component and the data sets required for the connected message receivers, a corresponding filter (12F, 14F) is determined (S3) and set (S4) for each network component. As a result, during operation of the communication network (1), only the required data sets are transmitted in the message (NWM) in the downstream direction of the data flow.

Description

Technical Field

[0001] The invention relates to a method for configuring an industrial real-time capable communication network for cyclically transmitting messages. Background Art

[0002] In industrial communication networks, efforts are being made to reduce the load on the communication network as much as possible when transmitting data. This should be achieved in particular by not transmitting unnecessary data via the communication network at all. This is the only way to reliably implement the required real-time functions and comply with the relevant standards.

[0003] However, the communication used in industrial communication networks via the OPC UA PubSub Part 14 (Open Platform Communications Unified Architecture Publish / Subscribe) standard offsets this effort. A typical industrial communication network comprises a message source as a sender, at least one message receiver as a receiver and at least one network component as a corresponding connection element between the sender and (multiple) receivers. When communicating via OPC UA PubSub, on the side of the message source (the so-called publisher), data is obtained from a model, packaged into corresponding groups of the model and sent as messages (so-called network messages or network information). The corresponding message receiver (the so-called subscriber) receives the message and checks which groups it subscribes to and uses the corresponding information from the message. When receiving a message, groups that are not relevant to the relevant message receiver are discarded by the message receiver. The load on the message receiver is thus reduced by discarding unnecessary groups.

[0004] However, the communication network is burdened by the transmission of unnecessary information. To date, this additional load has been accepted at the expense of the communication network, which, however, increases its costs and has a negative impact on the real-time capability of the data transmission with respect to delay times and / or jitter. Summary of the invention

[0005] The object of the present invention is to provide a method for configuring an industrial real-time capable communication network for transmitting messages and an industrial real-time capable communication network, which are improved in terms of function and / or structure so that the load on the communication network during the cyclic transmission of messages remains as low as possible.

[0006] These objects are achieved by the method according to the invention and the communication network according to the invention. Advantageous embodiments are given in the various embodiments.

[0007] A method for configuring an industrial real-time capable communication network for cyclic transmission of messages is proposed. The respective message comprises one or more data sets. The communication network comprises a message source, at least one message receiver and at least one network component as a message forwarding component. The message source is designed to generate messages and to send messages cyclically. The at least one message receiver is designed to receive and process messages. At least one network component receives messages from one of the message source or the network component and forwards them to at least one message receiver or one of the network components.

[0008] The method comprises the step of determining the network topology of a communication network, the communication network being used to transmit a data stream to be sent by a message source in the future, in which messages with all data sets are respectively sent cyclically. The method comprises the step of deriving which data sets or which data sets in the data stream a corresponding one of the message receivers wants to receive (i.e. subscribe to). A further step comprises deriving a corresponding filter for each network component by deriving from the network topology the components including message receivers and / or network components connected to the corresponding network component and the data sets required by the connected message receivers. Finally, the method comprises the step of setting a corresponding filter in each network component, whereby, during operation of the communication network, the received messages are filtered in the downstream direction of the data stream and only the data sets required downstream are transmitted in the message. The required data sets are the data sets subscribed to by the message receivers.

[0009] According to another aspect of the present invention, a communication network with industrial real-time capability is proposed, which is designed for cyclic transmission of messages. The corresponding message includes one or more data sets. The communication network includes: a message source for generating messages and cyclically sending messages; at least one message receiver for receiving and processing messages; and at least one network component as a message forwarding component for receiving messages from a message source or one of the network components and forwarding them to at least one message receiver or one of the network components. The communication network is designed to determine the network topology of the communication network, and the communication network is used to transmit a data stream to be sent from the message source in the future, wherein messages with all data sets are respectively sent cyclically. The communication network is also designed to derive which or which data sets in the data stream the corresponding message receiver wants to receive (i.e. subscribe to). In addition, the communication network is designed to determine the corresponding filters of the network components by deriving the components (including message receivers and / or network components) connected to the corresponding network components from the network topology and the data sets required by the connected message receivers. Finally, the communication network is designed to set the corresponding filters in each network component, thereby filtering the received messages in the message in the downstream direction of the data stream during the operation of the communication network, and only transmitting the required data sets.

[0010] A method for distributing data by means of multicast is known from EP2355403, wherein receivers and senders distribute their data via a publish / subscribe mechanism. In this case, data packets can be filtered in the network according to existing topological information.

[0011] The proposed invention makes it possible to eliminate unnecessary data traffic from a communication network at an early stage. To achieve this, the data path is first known by determining the network topology of the communication network. In order to understand the content to be transmitted, it is determined which data sets in the data stream a corresponding one of the message receivers wants to receive. Using this information, it is possible to determine a corresponding filter for each network component present in the communication network, so that a part of the data set included in the message can be filtered out from the data stream with a high probability by the filter, so that the load on the communication network can be reduced. Thus, distributed filtering of application-oriented data information is achieved on the transport layer. In this case, restrictions as would be expected in the case of a violation of layer separation (layer separation (Layer-Trennung)) do not occur in the communication network.

[0012] The proposed filter method can be easily implemented in industrial communication networks, because compared to today's standards, only the filter mechanism needs to be added to the network components. Since this is an application-specific extension, all remaining network traffic within the communication network is not affected by this extension. Here, the data flow forms a natural shield between the communication of different applications.

[0013] In particular, the communication network is based on the OPC UA PubSub standard. Accordingly, the message source is designed to generate messages according to the OPC UA PubSub standard. When communicating via OPC UA PubSub, the message source obtains data from the model, packages them into corresponding data sets, and sends them via messages. Message receivers receive messages and check the data sets to which they are subscribed. Since data sets that are not subscribed by message receivers have been filtered out in the network components, there is no need to discard unsubscribed data sets in the message receiver, thereby resulting in a reduction in the load of the message receiver in addition to reducing the network load.

[0014] The determination of the network topology is preferably based on the IEEE 802.1 standard TSN (Time Sensitive Networking). TSN assumes that the communication network knows the data path, because the data path is derived within the scope of TSN itself. Therefore, the step of determining the network topology can be implemented by the known mechanisms of TSN. However, TSN has no knowledge of the content of the message and the data transmitted via the data path. Therefore, by combining TSN with the mechanisms of OPC UA PubSub, a filtering mechanism can be implemented, which can realize a one-time determined dynamic path for the content included in the message.

[0015] Another useful design provides that each data set in the message is provided with a data set identifier, the so-called data set writer ID (Dataset WriterID), wherein the data set identifier is processed as a filter criterion in the filter. The data set identifier can thus be used to forward data sets that are important for the relevant message receiver, i.e. data sets that have been subscribed to by the message receiver, on the data path. Filtering of the data set identifier can be realized in a simple manner, since the data set identifier has an n-bit value, for example n=16. Therefore, filtering can be realized selectively by a filter implemented in software or hardware.

[0016] In addition, it is advantageous if the filters of each network component are configured only according to the data sets required for the connected message receivers. Here, the configuration includes determining and setting the corresponding filters.

[0017] It is also advantageous if the filter of each network component is additionally configured as a function of the network components connected in the downstream direction of the data flow and the data sets required for the message receivers connected to the network components. For this purpose, for example, the network components can exchange data with one another, for example by traversing a path from the respective subscriber back in the direction of the message source in order to determine which data sets are required for the relevant subscriber or for all subscribers arranged downstream of the relevant network component. This process can particularly significantly reduce the network load.

[0018] In addition, it is also advantageous if the determination and setting of the corresponding filters is performed once before the data stream is established and sent, thereby defining the dynamically planned path once with respect to the data sets and message sources subscribed by the corresponding message receiver.

[0019] According to another advantageous embodiment, the determination and setting of the corresponding filter is performed by a superior computing unit, which obtains or queries information from the message receivers about which data sets in the data stream the corresponding one of the message receivers wants to receive (subscribe to). Alternatively, the determination and setting of the corresponding filter is performed by the corresponding network component, which obtains or queries information from the message receivers about which data sets the corresponding one of the message receivers wants to receive (subscribe to). In particular, the corresponding network component obtains or queries information about which data sets are required in the data stream from a network component connected in the downstream direction of the data stream. This corresponds to the above-mentioned passage through the path from behind in the direction of the message source.

[0020] The invention also comprises a method for cyclic transmission of messages in a communication network configured according to the invention.

[0021] In addition, a computer program product is proposed, which can be directly loaded into the internal memory of a digital computer and includes software code segments, which, when the product is run on the computer, implement the steps of the method described herein. The computer program product can be embodied in the form of a physical storage medium such as a USB flash drive, a high-density digital video disk (DVD), a read-only disk (CD-ROM), a flash memory, etc. Similarly, the computer program product can be designed in the form of a signal that can be loaded via a wireless or wired network.

[0022] The industrial real-time-capable communication network described above may also include further components which allow the implementation of advantageous or preferred embodiments of the method according to the invention either individually or in any desired combination. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The present invention will be explained in more detail below based on the description of the embodiments in the accompanying drawings. Shown in the drawings:

[0024] Figure 1 A schematic diagram of an industrial communication network is shown, in which conventional transmission of data streams is implemented;

[0025] Figure 2 Shows Figure 1 Schematic diagram of an industrial communication network shown in , in which a first embodiment variant of the method according to the invention enables the transmission of data streams;

[0026] Figure 3 Shown in Figure 1 Schematic diagram of an industrial communication network shown in , in which a second practical variant of the method according to the invention implements the transmission of data streams; and

[0027] Figure 4A flow chart illustrating the execution of the steps of the method according to the invention is shown. DETAILED DESCRIPTION

[0028] Figure 1 1 shows a schematic diagram of an exemplary, simple industrial real-time capable communication network 1. Figure 1 In the communication network 1 shown, cyclically transmitted messages NWM are transmitted in a conventional manner from senders to receivers.

[0029] The communication network 1 includes a message source 10 as a transmitter, which is also called a publisher. The message source 10 is designed to generate messages NWM and send them out cyclically. Each message NWM sent by the message source 10 includes multiple data sets DS. The cyclic transmission of multiple messages NWM is called a data stream. The number of data sets DS in the message NWM can be any number in principle, that is, 1 or more. In the present embodiment, it is assumed that the corresponding message NWM includes four different data sets "1", "2", "3" and "4", which are referred to as DS1, ..., DS4 below for simplicity.

[0030] The communication network 1 comprises, for example, three message receivers 16, 17, 18 as receivers of the message NWM, which are also referred to as subscribers. The number of message receivers can also be greater or less than three. The message receivers 16, 17, 18 are designed to receive the message NWM and process the data set DS or only a part of the data set DS contained in the message NWM. The message receivers 16, 17, 18 are not directly connected to the message source 10. Instead, a plurality of network components 12, 14 are provided as switching or forwarding components, which connect the message source 10 and the message receivers 16, 17, 18 in the communication network 1. The network components 12, 14 are, for example, bridges. The message NWM is then transmitted to the message receivers 16, 17, 18 via the network components 12, 14 along a predetermined interconnection path.

[0031] In the present embodiment, only two network components 12, 14 are shown, wherein the number can also be greater or less than two. In the topology shown here only as an example, the network component 12 is connected to the message source 10. In the downstream direction of the data flow sent from the message source 10, the network component 14 and the message receiver 17 are also connected to the network component 12. The message receivers 16, 18 are in turn connected to the network component 14 in the downstream direction.

[0032] The cyclic transmission of NWM messages in the communication network 1 is implemented in a communication according to the OPC UA PubSub standard. In this case, the data sets DS1, ..., DS4 are obtained by the message source 10 according to a model not shown, packaged into the message NWM and sent out as a data stream, that is, as a cyclic sequence of messages NWM with all data sets DS1, ..., DS4. The message NWM is transmitted from the message source 10 as a broadcast message to the network component 12 in a cyclic sequence. The network component 12, for its part, transmits the message NWM to the network component 14 and the message receiver 17 directly connected thereto. The network component 14 in turn transmits the message NWM to the message receivers 16, 18.

[0033] From the basis Figure 1 As can be seen from the diagram of FIG, which shows the content of the message NWM at the output of each component to the receiver, the message NWM is forwarded unchanged from the network component 12, 14 to the connected message receivers 16, 17, 18. The message receivers 16, 17, 18 receive the message NWM and check which data sets DS the message is subscribed to, i.e. which data sets are to be received. Figure 1 In the embodiment of , data receiver 16 has subscribed to data sets DS1, DS3, DS4, for example. Data receiver 17 has subscribed to data sets DS1, DS2, and data receiver 18 has subscribed to data sets DS1, DS2. The corresponding unsubscribed data sets are then discarded in the corresponding data receivers 16, 17, 18. This means that message receiver 16 discards data set 2, and message receivers 17, 18 discard data sets 3 and 4.

[0034] It is obvious that in this case, regardless of the data sets processed by the message receivers 16, 17, 18, the communication network 1 is subject to a high data load.

[0035] Figure 2 The process according to the invention is shown, which allows the cyclic transmission of the message NWM with reduced load. Here, the topology corresponds to the combination of Figure 1 Describes the topology.

[0036] Figure 2 The communication network 1 shown in FIG. 1 also uses communication via OPC UA PubSub, i.e. the message source 10 sends messages NWM containing data sets DS1, ..., DS4 in a cyclic sequence. In order to reduce the network load, the network topology of the communication network 1 is determined once ( Figure 4Step S1 in the figure is used to transmit the data stream to be sent by the message source 10. Therefore, in this first step, the understanding of the data path of the communication network is obtained by the physical arrangement of the components (i.e. the message source 10, at least one network component 12, 14 and at least one message receiver 16, 17, 18) connected to each other via a transmission medium (line or wireless communication link). The determination of the network topology can be based on the TSN (Time Sensitive Network) standard.

[0037] In the next step S2 ( Figure 4 ), it is determined which or which of the data sets DS1, ..., DS4 in the data stream a corresponding one of the message receivers 16, 17, 18 wants to receive, i.e. subscribe to. In this second step, the understanding of what the message receiver needs is thus determined. Figure 2 In the illustrated embodiment, it is assumed that the message receiver 16 has subscribed to the data sets DS1, DS3 and DS4 and the message receivers 17, 18 have subscribed to the data sets DS1, DS2.

[0038] Steps S1 and S2 can be performed once by a (not shown) superordinate computing unit or after each change in the network topology due to the addition or removal of components. Within the scope of step S2, the superordinate computing unit can, for example, actively retrieve the data sets required (i.e. subscribed) by the message receivers 16, 17, 18 or receive information from them within the scope of the start step. Alternatively, information about which data sets DS1, ..., DS4 should be received by the corresponding message receivers 16, 17, 18 can be retrieved or obtained from the corresponding computing units of the network components 12, 14.

[0039] If, in addition to knowing the data path, it is also known how much information is needed from the message receivers 16, 17, 18, then in step S3 ( Figure 4 ) can define corresponding filter criteria or filters 12F, 14F for each component that forwards messages. The components that forward messages are network components 12, 14. In this case, the components connected downstream of the respective network components 12, 14 are determined by the network topology, including message receivers 16, 17, 18 and / or network components 14 and data sets DS1, ..., DS4 required for the connected message receivers 16, 17, 18.

[0040] In step S3, the filter criteria of the filter 12F are derived, according to which the network component 12 only needs to forward the data sets DS1 and DS2 to the message receiver 17 directly connected to the network component. In contrast, the network component 12 does not need to transmit the data sets DS3 and DS4 that are not required by the message receiver 17. Therefore, the message NWM of the message receiver 17 only needs to include DS1 and DS2. In contrast, the network component 12 must transmit the message NWM with all the data sets DS1, ..., DS4 to the network component 14 according to the intersection of all required data sets DS of the downstream connection components in this embodiment. As the filter criteria of the filter 14F of the network component 14, it is determined that the message receiver 16 only needs the data sets DS1, DS3, DS4 and the message receiver 18 needs the data sets DS1 and DS2. Therefore, the message NWM transmitted to the message receiver 16 only needs to include the data sets DS1, DS2, DS3. The message NWM transmitted to the message receiver 18 only needs to include the data sets DS1 and DS2.

[0041] In step S4( Figure 4 ), then corresponding filters 12F, 14F are set in the associated network components 12, 14. This means that a filter 12F is set in the network component 12 and a filter 14F is set in the network component 14. Thus, when the communication network 1 is in operation, only the required data sets can be transmitted in the downstream direction of the data flow in the message NWM.

[0042] The filtering of the message NWM by the filter 12F, 14F can be realized in a simple manner using a data set identifier (not explicitly shown). For this purpose, a data set identifier is provided in the message NWM for each data set DS1, ..., DS4. The data set identifier is then processed in the filter 12F, 14F as a filter criterion. The filter 12F, 14F can optionally be realized in software or hardware. If the already mentioned data set identifier is realized as a filter criterion, the realization in hardware is particularly easy.

[0043] exist Figure 2 In the design example shown, the filters 12F, 14F of each network element 12, 14 are configured only in dependence on the data sets required by the connected message receivers 16, 17, 18. The configuration includes determining and setting the corresponding filters. According to the above-described embodiment, the network element 12 transmits the message received from the message source 10 to the network element 14 without change, i.e. the message NWM includes all data sets DS1, ..., DS4.

[0044] Figure 3An embodiment based on the same network topology is shown, wherein the filters 12F, 14F of the network elements 12, 14 are configured according to the data sets subscribed to by the message receivers 16, 17, 18. For the purpose of illustrating this example, it is assumed that Figure 2 Differently, the message receiver 16 has subscribed to the data sets DS3, DS4 and the message receiver 18 has subscribed to the data sets DS1, DS3. Therefore, the network component 14 is not connected in the downstream direction to any component that is processing (subscribing to) the data set DS2. Within the scope of step S2, the network component 14, which determines which data set or data sets in the data stream the corresponding one of the message receivers wants to receive, can send the following information to the network component 12, namely that the record DS2 is not required. The network component 12 then sends a message NWM to the network component 14, which only includes the data sets DS1, DS3, DS4, but not the data set DS2. This leads to a further reduction in the network load.

[0045] The described process provides for distributed filtering of application-oriented data information at the transport level. Therefore, the filters are distributed, since the filters in different network components have different filter configurations. In a strict sense, this contradicts the separation of network layers. In the context of the present invention, this advancement is advantageously considered to significantly reduce the overall network load. In this case, no restrictions are created in the communication network as would be expected in a violation of the layer separation.

[0046] Compared to today's standards, the only thing to be added to the data sets DS1, ..., DS4 is the respective data set identifier, which can then be processed in the filters 12F, 14F.

[0047] The entire remaining network traffic in the communication network is not affected due to the application-specific expansion in the network components 12, 14. Here, the data stream forms a natural shield between the communications of different application programs.

Claims

1. A method for configuring an industrial real-time communication network for cyclically transmitting messages (NWM), wherein: The corresponding message (NWM) comprises a plurality of data sets, and wherein the communication network (1) comprises: - a message source (10), the message source being designed to generate the message (NWM) and to cyclically send the message; - at least one message receiver (16, 17, 18) designed to receive and process the message (NWM); - at least one network component (12, 14) receiving the message from the message source (10) or one of the network components (12) and forwarding the message to at least one of the message receivers (16, 17, 18) or one of the network components (14); The method comprises the following steps: - determining a network topology of the communication network (1) for transmitting a data stream to be sent in the future by the message source (10), in which the message (NWM) with all data sets is respectively sent cyclically; - deriving which data sets or data sets in the data stream a corresponding one of the message receivers (16, 17, 18) wants to receive; - determining a corresponding filter (12F, 14F) for each of the network components (12, 14) by deriving from the network topology the components connected to the corresponding network component (12, 14) and the data sets required for the connected message receivers (16, 17, 18), wherein the components include the message receivers (16, 17, 18) and / or the network components (14); - in each of the network components (12, 14), a corresponding filter (12F, 14F) is provided, whereby during operation of the communication network (1) in the downstream direction of the data flow, received messages (NWM) are filtered and only required data sets are transmitted.

2. The method according to claim 1, wherein: The communication network (1) is based on the OPC UA PubSub standard.

3. The method according to claim 1 or 2, wherein: The network topology is determined based on the TSN standard.

4. The method according to claim 1 or 2, wherein: Each of the data sets in the message is provided with a data set identifier, wherein the data set identifier is processed as a filter criterion in the filter (12F, 14F).

5. The method according to claim 1 or 2, wherein: The filter (12F, 14F) of each of the network components (12, 14) is configured according to a data set required for the directly connected message receivers (16, 17, 18).

6. The method according to claim 5, wherein: The filter (12F, 14F) of each network component (12, 14) is also configured according to the network component (14) indirectly connected in the downstream direction of the data flow and the data set required for the message receiver (16, 17, 18) connected to the network component.

7. The method according to claim 1 or 2, wherein: The determination and setting of the corresponding filters (12F, 14F) are completed once before establishing and sending the data stream.

8. The method according to claim 1 or 2, wherein: The determination and setting of the respective filters (12F, 14F) are performed by a higher-level computing unit which obtains or queries information from the message receivers (16, 17, 18) about which data sets in the data stream a respective one of the message receivers (16, 17, 18) wants to receive.

9. The method according to claim 1 or 2, wherein: The determination and setting of the respective filter (12F, 14F) is performed by the respective network component (12, 14), which obtains or queries information from the message receivers (16, 17, 18) about which data sets in the data stream the respective one of the message receivers (16, 17, 18) wants to receive.

10. The method according to claim 9, wherein: The respective network component (12, 14) obtains or queries information about which data sets in the data flow are required from a network component (14) connected in the downstream direction of the data flow.

11. The method according to claim 1 or 2, wherein: Filtering is performed by filters (12F, 14F) implemented in software or hardware.

12. A computer program product which can be directly loaded into the internal memory of a digital computer and comprises software code sections by means of which the steps of the method according to any one of claims 1 to 11 are performed when the computer program product is run on a computer.

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