Methods used to run the network

Abstract

A method for operating a network is proposed, the network having a plurality of participants in the network. The network comprises at least one switch (10, 11, 12), at least two terminals and at least one controller. According to the invention, the controller now communicates with one of the terminals via an application protocol. For this purpose, data are sent and / or received as data packets. For the time plannability of the communication, time slots are provided for sending data packets, which are adapted to the maximum possible packet size. For this purpose, the time slots have a time start and a time end, wherein the time slots can overlap in different branches of the network. The packet size (5) can be varied in order to optimize the communication time. In order not to waste bandwidth in the network, the time slots are adapted to the packet size (6) accordingly by varying the time start and the time end.

Description

Technical Field

[0001] The invention relates to a method for operating a network, in particular an automation network. Background Art

[0002] The method is intended to be suitable for integrating components of an automation network into an existing multifunctional network, for example into an Ethernet network, in particular into a fieldbus network designed as an Ethernet bus.

[0003] In existing automation networks such as SERCOS III, there is usually a limitation that the devices in the automation network are the only users of the network. And although the automation network is also implemented as an Ethernet network, it is not easy to integrate such an automation network into an existing network.

[0004] These difficulties include limitations, for example, related to the network topology, which in turn make integration into other networks difficult or even impossible.

[0005] It should also be possible to integrate automation networks into TSN networks. TSN was developed to enable time-intensive data transmission in the network. TSN functions also make it possible to predict transmission times. The TSN network is standardized under IEEE 802.1.

[0006] In the example of SERCOS III network, the packet size of the data to be sent and / or received can be specified at the beginning of communication between two participants in the network. Because it is not confirmed at the beginning of communication how much data to send, the packet size of the data is first maximized.

[0007] During communication, the packet size can then be adapted to the data volume in order to optimize communication in the network. In particular, when using TSN networks, the adaptation of the packet size is an aid to the plannability of data transmission.

[0008] For this purpose, corresponding time slots are provided for the data packets, in which the data packets are sent. To calculate the total communication time, the individual time slots can then be added up, since all data packets are sent or received in these time slots.

[0009] For example, a corresponding known communication in an automation network is known from WO 2018 / 215209 A1. In this case, the individual devices are mainly connected in a linear topology and can realize corresponding communication via data telegrams.

[0010] A method for industrial communication via TSN is also known from WO 2017 / 093014 A1, which discloses basic communications and protocols in a TSN-enabled network.

[0011] EP 1 193 926 A2 discloses an automation network with data communication which utilizes time slots and also discloses the modification of data packets within the time slots.

[0012] US 2011 / 0182300 A1 also discloses a network in which time slots are used. Here, individual data packets can be transferred to other time slots. However, this method contains the risk that the time domain required for the transfer is already occupied by other data flows. Summary of the invention

[0013] The object of the present invention is therefore to integrate an automation network into an existing network, in particular into a TSN network. Furthermore, the data transmission should be optimized in terms of time with regard to the communication between the various network participants.

[0014] This object is achieved with a method for operating a network according to the application.

[0015] The present invention relates to a method for operating a network, wherein the network has a plurality of participants in the network, the network includes at least one switch, at least two terminal devices and at least one controller, characterized in that the controller communicates with one of the terminal devices via an application protocol, for which purpose data is sent and / or received as a data packet, a time slot for sending and / or receiving the data packet is set during initialization of the communication, the time slot is adapted to the maximum possible packet size, the time slot has a time start and a time end, the time slots overlap in time and the time start of the time slot is before the time start of the data packet actually sent, and when the packet size changes, the time slot is adapted to the packet size by changing the time start and the time end.

[0016] Therefore, a method for operating a network is proposed, which has a plurality of participants and at least one switch. In this case, the switch acts as a node in the network and can send or receive data in all directions of the node. The switch also includes a programmable logic device, which can store and use relationships with other participants in the network.

[0017] Likewise, the network also includes at least two terminal devices and a controller. The controller is also called a master station in the automation network.

[0018] According to the present invention, the controller can send data to a certain terminal device via an application protocol in order to control the terminal device. Here, the application protocol is implemented via the application layer of the OSI network model. This means that the communication is implemented in OSI layer 7 via the application protocol.

[0019] The data sent in this way is divided into data packets according to the specifications for the Internet network and sent via the data link layer of the network. This means that the individual data packets are transmitted within the data link layer or network layer (i.e. layer 2 or 3 of the OSI model). Data packets are therefore transmitted in layer 2 as frames (Frame) or in layer 3 as packets.

[0020] Advantageously, the data are sent as a TSN data stream, which means that the data stream of the sent and / or received data is provided with a time-intensive feature according to IEEE 802.1.

[0021] According to the invention, time slots are now provided for sending and / or receiving data. These time slots are initially adapted to the maximum and / or minimum or any other conceivable packet size or number of packets at the beginning of communication. At the beginning of communication, the amount of data to be sent has not yet been confirmed, so that the time slots are initially defined according to the maximum packet size or number of packets.

[0022] The time slots each contain a time start and a time end. All time slots therefore have a runtime, with the aid of which the transmission time of the data can be calculated, i.e. by adding up the runtimes of the time slots. Alternatively or additionally, the transmission time of the data can be calculated purely via the transmission speed and the amount of data and is not influenced by the time slots.

[0023] The initiation of communication can be achieved by a participant in the network that is capable of this. In the case of a SERCOS III network, this participant is usually a controller or a host.

[0024] During the communication, the packet size of the data packets can be optimized. This means that the initial packet size is reduced or increased during the communication within the range of a minimum and a maximum packet size and a number of packets. This changes the occupation of the available time slots by the data packets. As a result, the entire communication either lasts longer (in the case of a larger amount of data) or the transmission is shortened (due to a reduced amount of data).

[0025] The oversized time slots ensure that the communication is not artificially slowed down, for example by also planning the reduced packet size. After the communication has finally been established and the application has processed the final amount of data, the reservation of time slots can be optimized. So far, it has only been known to adapt the end of the time slot to the communication requirements, because the initial reservation has previously set the beginning of the time slot according to the maximum packet size. This results in gap times during which packets must remain at the switch until the next time slot begins.

[0026] Optimizing such gap times means that all time slots will be moved forward. This means that the communication duration varies in continuous operation, which is known as jitter. In particular, such jitter should be avoided in streaming applications because it hinders efficient data transmission on the one hand and causes additional gaps or interruptions on the receiving end on the other hand. In the case of SERCOS III networks, as soon as jitter occurs, the network is put into an error state.

[0027] In order to avoid jitter, the reduced time slot must be shifted. In order to avoid the aforementioned error state, the reduction and shift of the time slot must actually occur simultaneously, which is not actually possible up to now.

[0028] However, by initially designing the time slots for the minimum and / or maximum packet size, it is possible to shift not only the end of time but also the beginning of time. Then, due to the oversizing of the time slots at the beginning of the communication, the time slots may now overlap in time and the beginning of time of the time slot is before the beginning of time of the data packet actually sent.

[0029] For overlapping of time slots, the time slots can preferably be adapted to the minimum expected packet size. This occurs by selecting the time start of the individual time slots in such a way that the subsequent time slots have a time start corresponding to the minimum expected packet size.

[0030] By overlapping the time slots in time, gaps between individual data packets can be avoided when the data packets are reduced. The time slots can then be adapted to the packet size of the data packets via the time start and time end.

[0031] Since no gaps occur when shrinking the data packets, jitter effects are avoided and the data flow remains consistent. The adaptation of the time slots is therefore not time-critical in the claimed method. Accordingly, the packet size change can be decoupled from the adaptation of the time slots without jitter effects or error states occurring.

[0032] In this case, the data packets and their size are controlled by protocols in layer 2 or layer 3 of the OSI model, so that the application protocol does not recognize the optimization of the data transmission.

[0033] The switches should be arranged at nodes of the network, preferably between the controller and the terminal, so that different topologies can be interconnected in the network starting from these nodes.

[0034] The terminals of an automation network can be connected in series in a ring or line, depending on the topology. This also corresponds to the normal function of an automation network. In principle, multiple automation networks can thus be interconnected together in one network via switches, wherein participants that are not part of an automation network can also participate in the same network.

[0035] It is preferably provided that the controllers and the terminals are participants in an automation bus. The bus is then operated as an automation network with Ethernet specifications. The number of controllers and terminals in the network is not limited.

[0036] As a special embodiment, the switch can be replaced by a router, since the router also contains the functionality of a switch. Other participants, such as PCs, servers and / or hubs, can also be present.

[0037] It is preferably provided that the controller and / or the switch (or router) are configured by a network management system, which is preferably implemented as software, in order to be able to implement a desired routing of data from the network participants to the terminal. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Further features are apparent from the accompanying drawings.

[0039] Figure 1 A block diagram showing the problem to date with respect to packet size variation;

[0040] Figure 2 A block diagram showing a method according to the present invention;

[0041] Figure 3 The operation phases are shown taking a SERCOS III network as an example. DETAILED DESCRIPTION

[0042] Figure 1 A schematic diagram of a portion of the communication in a network is shown. The data to be transmitted are divided into data packets and sent or received using the currently available bandwidth of the network.

[0043] The data packets are shown in the figure as areas with oblique hatching. By way of example, the communication includes three data packets, which are sent or received via different cycles of the network. The term cycle is understood here in accordance with IEEE 802.1Q ("time-aware shaping"). The individual cycles are shown here as dotted areas and can be responded to by the three switches 10, 11, 12.

[0044] The following time slots are provided for the data packets, which are indicated by the vertically shaded areas. At the beginning of the communication, these time slots are defined according to the maximum packet size. Thus, the time start of the time slot coincides with the start of the data packet. The time end of the time slot may be greater than the time end of the data packet due to the maximum size assumption. The maximum packet size is thus affected by the amount of data and the bandwidth available. This is standardized in IEEE 802.1Qbv.

[0045] In order to optimize the communication time, the respective packet size of the data packets is varied according to the optimal value in terms of time. This shortens the data packets, which is shown under step 1.

[0046] The shortening of the data packets and the time slots, which have remained the same length, create time gaps between the individual data packets. The individual time slots are implemented adjacently, which means that the end of a time slot is shown at the same time as the beginning of another time slot. This results in continuous communication. However, the available bandwidth is not used efficiently when the data packets are shortened.

[0047] In order to efficiently utilize the bandwidth, the time slot can be shortened by adapting the time end of the time slot to the time end of the data packet. This is shown in step 2. However, this results in gaps in the data stream transmission during communication, which are known as jitter effects and lead to errors in the network. In the case of a SERCOS III network, this results in an error state.

[0048] Therefore, the time slots must be displaced or shifted so that a coherent data stream is generated again. This is shown in step 3. In order to avoid an erroneous state, steps 2 and 3 must be performed together (simultaneously), which is equivalent to step 4, but is not practically possible, because the shifting of time slots is also erroneous. Due to the shift, the time slot may fall into the already reserved time domain.

[0049] Figure 2 The solution according to the invention to the above-mentioned problem is shown. Here, time slots are also generated at the beginning of the communication, which are adapted to the maximum possible packet size. However, according to the invention, these time slots are designed in such a way that they overlap. The continuous data flow is ensured by the different time starts of the data packets within these time slots. Therefore, the time start of the time slot no longer coincides with the time start of the data packet.

[0050] If the data packets are now reduced, a continuous data flow can still be ensured by overlapping the time slots without error states occurring. This is shown in step 5.

[0051] Now, the communication will always still work properly without errors, but it will not be efficient due to the length of the time slots.

[0052] Accordingly, it is proposed to adapt the time slot to the shortened data packet in such a way that the temporal end of the time slot is adapted not only to the data packet but also to the temporal beginning. This is shown in step 6 .

[0053] The method enables the size of the data packets to be optimized without having to shift the time slots. The adaptation of the time slots to the data packets is decoupled from the reduction of the data packets, thereby eliminating possible sources of errors.

[0054] exist Figure 3The method is explained in the following using the SERCOS III operating phase. First, communication is initiated using SERCOS III (NRT) and then the topology of the network is determined in the direction of M according to the application protocol (CP0).

[0055] Next, the configuration is loaded and executed in the direction of S (CP1). In the next step, the data packet size is determined in the direction of S and optimized during the communication (CP2). From this point on, the terminal device acting as the communication receiver is sensitive to jitter.

[0056] CP3 includes the actual communication with an optimized packet size. CP4 ends the communication and enables the next communication working according to the same principle.

[0057] Thus, the method according to the invention is implemented in the marked area. Accordingly, the initial packet size and time slot size are specified starting from CP2 and optimized between CP2 and CP3 (see Figure 2 5 and 6 in the previous step).

[0058] The present application is not limited to the aforementioned features. Instead, other implementations can be envisioned. Thus, a router or server can also be used to replace at least one switch. Similarly, other participants, such as a PC or a hub, can be used.

Claims

1. A method for operating a network having a plurality of participants in the network, the network comprising at least one switch (10, 11, 12), at least two terminals and at least one controller, It is characterized in that The controller communicates with one of the terminal devices via an application protocol, To this end, data is sent and / or received as data packets. During the initialization of the communication, a time slot is set for sending and / or receiving a data packet, the time slot being adapted to the maximum possible packet size, the time slot having a time start and a time end, the time slots overlapping in time and the time start of the time slot being before the time start of the data packet actually sent, And when the packet size changes (5), the time slot is adapted to the packet size by changing the time start and time end (6).

2. The method according to claim 1, characterized in that The temporal start of each time slot is adapted to the smallest possible packet size.

3. The method according to claim 1, characterized in that The network is implemented as an automation network.

4. The method according to any one of claims 1 to 3, characterized in that The size of the time slot is adapted by the controller during initialization of the communication according to the maximum possible packet size.

5. The method according to any one of claims 1 to 3, characterized in that The change in packet size is performed during the communication.

6. The method according to any one of claims 1 to 3, characterized in that The change in the packet size and the change in the time start and time end are not temporally related to each other.

7. The method according to any one of claims 1 to 3, characterized in that The change in the packet size and the change in the time start and time end are controlled by a protocol which operates independently of the application protocol. 8 . The method according to claim 1 , wherein the participants are connected to the switches ( 10 , 11 , 12 ) in a ring topology or a line topology.

9. The method according to any one of claims 1 to 3, characterized in that The at least two terminal devices are connected in series.

10. The method according to any one of claims 1 to 3, characterized in that The communication takes place within the data link layer of the network via data packets.

11. The method according to any one of claims 1 to 3, characterized in that The switches (10, 11, 12) are implemented as routers or servers.

12. The method according to any one of claims 1 to 3, characterized in that There are multiple controllers as participants in the network.

13. The method according to any one of claims 1 to 3, characterized in that The configuration of the controller and / or the switch is implemented through a network management system.

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