Method for transmitting time-critical data within a communication system and communication control device

Description

[0001] The present invention relates to a method for transmitting time-critical data, in particular control data in an industrial automation system, within a communication system and to a communication control device provided for carrying out the method.

[0002] An industrial automation system typically comprises a large number of automation devices interconnected via an industrial communication network and is used to control or regulate systems, machines, or devices within the framework of production or process automation. Due to the time-critical conditions in industrial automation systems, real-time communication protocols such as PROFINET, PROFIBUS, Real-Time Ethernet, or Time-Sensitive Networking (TSN) are predominantly used for communication between automation devices.

[0003] Due to their often highly diverse use in Ethernet-based communication networks, problems can arise, for example, when network resources for transmitting data streams or data frames with real-time requirements are used concurrently with transmitting data frames with large payloads without specific quality of service requirements. This can result in data streams or data frames with real-time requirements not being transmitted according to the requested or required quality of service.

[0004] According to EP 3 038 325 A1, for data transmission in a communication network of an industrial automation system, first data frames comprising control data for the automation system are transmitted by coupling communication devices of the communication network only within periodic first time intervals. Second data frames, which are assigned to sequences of data streams comprising data frames, or third data frames, for whose transmission no quality of service or a quality of service below a predetermined threshold is specified, are transmitted within periodic second time intervals. The first time intervals are divided into first and second subintervals. First data frames to be forwarded are inserted into a first or second queue in alternating subintervals and are alternately removed from the queues for forwarding.

[0005] WO 2019 / 001718 A1 describes a data transmission method that combines secure communication with minimal network configuration effort. When reserving resources for transmitting data streams from a sender to a receiver, at least two paths that are at least partially redundant are reserved. By extending a reservation protocol, duplicate filters are automatically configured at network nodes assigned to redundant path sections during a resource reservation.

[0006] WO 2020 / 114706 A1 discloses a communication system for transmitting time-critical data, in which selected datagrams are assigned to data streams and transmitted via paths for the data streams. Reservation requests, each of which includes at least information about a first and second network node and quality of service parameters, are transmitted to a higher-level communication control device by a reservation function component assigned to a first or second communication terminal or a communication device connected to it that forwards datagrams.The higher-level communication control device determines a path for each reservation request and checks whether sufficient resources are available in communication devices along the respective path for the transmission of the data streams while adhering to the specified quality of service parameters, and determines a proposed local cycle duration for selected communication devices.

[0007] "Reconfiguration Algorithms for High Precision Communications in Time Sensitive Networks: Time-Aware Shaper Configuration with IEEE 802.10cc (Extended Version)" (ARXIV.ORG, CORNELL UNIVERSITY LIBRARY, 201 OLIN LIBRARY CORNELL UNIVERSITY ITHACA, NY 14853, June 27, 2019 (2019-06-27)) describes a method for transmitting time-critical data within a communications system. Selected datagrams are assigned to data streams and transmitted from first communication devices to second communication devices via third communication devices along comprehensive paths. A higher-level communications control device determines a path for each data stream and, if sufficient resources are available, reserves resources for transmitting the respective data stream via the third communication devices.If sufficient resources are available, the higher-level communication control device configures third communication devices connected to at least a first or second communication device in such a way that datagrams assigned to data streams are each queued in transmission queues reserved for data streams.

[0008] US 2006 / 092963 A1 relates to a method for communication within a network, in which a profile for a data flow with a guaranteed Quality of Service (QoS) is first generated in a wireless network client. Upon receipt of the profile, a configuration parameter is created to achieve QoS for the data flow. A layer of a data path assigned to the data flow is configured according to this configuration parameter. If sufficient resources are not available, the data flow is treated as best-effort traffic.

[0009] Even with a central stream reservation model, stream reservation requests are generally transmitted independently of one another to a central network controller (CNC) or to a higher-level communications control device. Upon receipt of a stream reservation request, the central network controller immediately schedules reservation requests, provided sufficient resources are available in the respective communications system. This is commonly referred to as incremental scheduling. This can result in the central network controller having to reject a stream reservation request for an inherently high-priority process, particularly a time-critical control process in an industrial automation system, if, for example, after reserving system resources for a less time-critical application, e.g., a data analysis application, there are no longer sufficient system resources available.

[0010] The present invention is based on the object of providing a method for transmitting time-critical data within a communication system, which enables efficient resource reservation and reliable establishment of data streams for transmitting high-priority data, and of specifying a suitable device for carrying out the method.

[0011] This object is achieved according to the invention by a method having the features specified in claim 1 and by a communication control device having the features specified in claim 14. Advantageous further developments are specified in the dependent claims.

[0012] According to the inventive method for transmitting time-critical data within a communications system, selected datagrams are assigned to data streams and transmitted from first communication devices to second communication devices via paths comprising third communication devices. To announce subscribeable data streams, the first communication devices each send first datagrams comprising a data stream identifier and specify quality of service parameters for the respective data stream in the first datagrams. In contrast, the second communication devices each send second datagrams to reserve resources to be provided by the third communication devices for transmitting the data streams, specifying the respective data stream identifier in these second datagrams.For the first and second datagrams, a higher-level communication control device, in particular a central network controller, determines a path for the respective data stream and, if sufficient availability exists, reserves resources for transmitting the respective data stream via the third communication devices.

[0013] The resources to be provided by the third communication devices in particular include, for example, usable transmission time slots, bandwidth, guaranteed maximum latency, number of queues, queue cache, or address cache in switches or bridges. The data stream identifiers are preferably provided to the respective first communication device by the higher-level communication control device in response to a reservation request from a first communication device. Furthermore, according to the invention, the data streams are each identified for a transmit queue assignment of their datagrams by their data stream identifier and their assignment to a virtual local network, in particular in accordance with IEEE 802.1 CB.

[0014] If sufficient resources are available, the higher-level communication control device configures at least third communication devices connected to a first or second communication device, according to the invention, such that datagrams assigned to data streams are each queued in transmission queues reserved for data streams. In contrast, if sufficient resources are insufficient or uncertain, the higher-level communication control device configures at least the third communication devices connected to a first or second communication device, at least temporarily, such that datagrams assigned to selected data streams are each queued in a transmission queue for data traffic that is handled without a specific quality of service assurance.Advantageously, the higher-level communication control device configures at least the third communication devices connected to a first or second communication device, each by entries in a respective forwarding database, for which virtual local network is assigned to a data stream or whether and with which priority datagrams assigned to a data stream are each queued in a transmission queue reserved for data streams.

[0015] Overall, the present invention makes it possible to avoid reserving resources for streams whose applications or associated processes have a lower priority than applications or processes for which resources are to be reserved later, so that reserving resources for streams can be ensured for high-priority applications or processes. This is particularly relevant for dynamic allocation of resources for streams during a bootstrapping process, where the order in which reservation requests arrive is sometimes difficult to predict. Thus, with the present invention, it is sufficient that, in response to stream reservation requests, only a respective stream ID is initially announced in the communication system, without immediately reserving resources.According to the invention, this can be done at a later point in time, for example when an overview of all reservation requests to be considered is available.

[0016] According to a particularly preferred embodiment of the present invention, the higher-level communication control device configures, if sufficient resources are available, third communication devices connected to at least one first or second communication device in such a way that the data streams are each assigned to a virtual local network and datagrams assigned to data streams are each queued in the respective transmission queues reserved for data streams on the basis of this assignment.If sufficient resources are insufficient or uncertain, the higher-level communication control device advantageously configures at least the third communication devices connected to a first or second communication device, at least temporarily, to assign selected data streams to a virtual local network, based on which assignment, datagrams assigned to the respective selected data stream are each placed in the respective send queue for data traffic that is handled without a specific quality of service assurance. Thus, the assignment of the virtual local network can change whether and with what priority datagrams assigned to a data stream are each placed in a send queue reserved for data streams.Therefore, it is easy to dynamically prioritize stream reservation requests by rewriting VLAN priority values ​​in edge bridges or switches depending on network load.

[0017] Preferably, during ongoing operation of the communication system, the higher-level communication control device creates an updated prioritization of all data streams in a time- or event-controlled manner and, based on the updated prioritization and currently available resources, determines which data streams are to be treated, at least temporarily, as selected data streams. In particular, the higher-level communication control device can configure at least the third communication devices connected to a first or second communication device during startup of the communication system such that all data streams are initially assigned to a virtual local network, based on which assignment datagrams assigned to the respective selected data stream are each placed in the respective send queue for data traffic that is treated without a specific quality of service assurance.Advantageously, after operation starts, the higher-level communication control device creates a prioritization of all data streams and, based on the prioritization and available resources, determines which data streams are to be treated as selected data streams, at least temporarily. This ensures reliable reservation of resources for transmitting streams assigned to high-priority control applications or processes, at least for these control applications or processes.

[0018] According to a particularly preferred embodiment of the present invention, the communication devices are interconnected via a time-sensitive network, in particular in accordance with IEEE 802.3-2018, IEEE 802.1Q-2018, IEEE 802.1AB-2016, IEEE 802.1AS-2011, IEEE 802.1BA-2011, and / or IEEE 802.1CB-2017. Forwarding of the selected datagrams is advantageously controlled by means of frame preemption, in particular in accordance with IEEE 802.1Q-2018, time-aware shaper, in particular in accordance with IEEE 802.1Q-2018, credit-based shaper, in particular in accordance with IEEE 802.1Q-2018, burst-limiting shaper, peristaltic shaper, and / or priority-based shaper.

[0019] In addition, the third communication devices preferably each contain send queues reserved at least for first data streams with increased real-time requirements, send queues reserved for second data streams without increased real-time requirements, and send queues for data traffic without a specific quality of service assurance, in particular best-effort data traffic. The higher-level communication control device initially reserves resources for transmitting the respective data stream via the third communication devices only for the first data streams, subject to sufficient availability, and configures the third communication devices to treat the second data streams at least temporarily as selected data streams, i.e., as best-effort data traffic.Advantageously, if sufficient resources are available to transmit the first data streams via the third communication devices, the higher-level communication control device checks whether sufficient resources are available to transmit the second data streams. Accordingly, the third communication devices are each configured to queue the datagrams assigned to the second data streams in the transmission queues reserved for the second data streams. This ensures that resources for transmitting data streams are successively reserved according to a respective assigned data traffic class.

[0020] The communication control device according to the invention is provided for carrying out a method according to the preceding embodiments and comprises at least one connection for connecting to a communication device that forwards datagrams. The communication control device is designed and configured to determine a path for the respective data stream in response to first datagrams sent by first communication devices for announcing subscribeable data streams and to second datagrams sent by second communication devices for reserving resources to be provided by third communication devices for transmitting the data streams, and, if sufficient availability exists, to reserve resources for transmitting the respective data stream via the third communication devices.

[0021] Furthermore, the communication control device according to the invention is designed and configured, when sufficient resources are available, to configure third communication devices connected to at least a first or second communication device so that datagrams assigned to data streams are each placed in transmission queues reserved for data streams. The communication control device is also designed and configured to configure the third communication devices so that the data streams are each identified by their data stream identifier and their assignment to a virtual local network for a transmission queue assignment of their datagrams.In addition, the communication control device is designed and configured to, in the event of a lack of or uncertain availability of sufficient resources, at least temporarily configure at least the third communication devices connected to a first or second communication device so that datagrams assigned to selected data streams are each placed in a transmission queue for data traffic that is handled without a specific quality of service assurance.

[0022] The present invention will be explained in more detail below using an exemplary embodiment with reference to the drawing. Figure 1 shows a communication system for an industrial automation system comprising several communication devices, Figure 2 shows a flow chart for a reservation of resources for the transmission of data streams within the communication system according to Figure 1 .

[0023] The Figure 1The illustrated communication system for an industrial automation system comprises a plurality of bridges or switches 101-103 as communication devices forwarding datagrams and a higher-level control device or a central network controller 400 assigned to them. The bridges or switches 101-103 each comprise a plurality of ports and a backplane switch as a coupling element and are used in particular for connecting programmable logic controllers 201, operator control and monitoring stations 202, I / O controllers or I / O modules, which also represent communication devices or communication terminals. In the present embodiment, the communication system is designed as a time-sensitive network, in particular according to IEEE802.3-2018, IEEE 802.1Q-2018, IEEE 802.1AB-2016, IEEE 802.1AS-2011, IEEE 802.1BA-2011 or IEEE 802.1CB-2017.Forwarding of data frames within the communication system can be controlled, for example, by means of frame preemption according to IEEE 802.1Q-2018, time-aware shaper according to IEEE 802.1Q-2018, credit-based shaper according to IEEE 802.1Q-2018, burst-limiting shaper, peristaltic shaper or priority-based shaper.

[0024] Programmable logic controllers 201 typically each comprise a communication module, a central processing unit, and at least one input / output unit. Input / output units can also be configured as decentralized peripheral modules located remotely from a programmable logic controller. A programmable logic controller 201 can be connected to a switch or router or additionally to a fieldbus via the communication module. The input / output unit is used to exchange control and measured variables between the programmable logic controller 201 and a machine or device 210 controlled by the programmable logic controller 201. The central processing unit is provided, in particular, for determining suitable control variables from acquired measured variables. The above components of the programmable logic controller 201 are connected to one another, for example, via a backplane bus system.

[0025] I / O modules can also be provided for exchanging control and measurement variables with connected machines or devices. I / O modules can be controlled, in particular, using an I / O controller per automation cell. Alternatively, I / O modules can also be controlled by a remote programmable logic controller.

[0026] An operator control and monitoring station 202 is used to visualize process data or measurement and control variables that are processed or acquired by programmable logic controllers, input / output units, or sensors. In particular, an operator control and monitoring station 202 is used to display values ​​of a control loop and to change control parameters. Operator control and monitoring stations 202 comprise at least a graphical user interface, an input device, a processor unit, and a communications module.

[0027] Using first communication or automation devices, which in particular have a talker or provider function, information or services are provided via data streams for use by second communication or automation devices, which in particular have a listener or consumer function. An automation device can simultaneously have one or more talker functions and one or more listener functions, for example, if it provides automation services on the one hand and uses automation services of other devices on the other.

[0028] The programmable logic controller 201 can, for example, provide measured values ​​and thus have a talker function. In contrast, the operator control and monitoring station 202 can have a listener function and, in particular, receive information provided by the programmable logic controller 201. In principle, the operator control and monitoring station 202 could analyze information received from the programmable logic controller 201 and, based on this, specify control parameters for the programmable logic controller 201. Thus, both the programmable logic controller 201 and the operator control and monitoring station 202 can perform both functions. Therefore, data streams in response to reservation requests are preferably set up bidirectionally.

[0029] To transmit time-critical data, at least selected data frames (frames) are assigned to 300 data streams and transmitted between first communication devices 201 with a talker function and second communication devices 202 with a listener function via the bridges or switches 101-103. In the present exemplary embodiment, the programmable logic controller 201 represents a first communication device with a talker function, while the operator control and monitoring station 202 represents a second communication device with a listener function. The bridges or switches 101-103 represent third communication devices that forward datagrams.

[0030] First communication devices, such as the programmable logic controller 201, send first datagrams 301 each comprising a data stream identifier to announce subscribeable data streams and specify quality of service parameters for the respective data stream in the first datagrams 301. The data stream identifier is communicated to the respective first communication device in response to a stream reservation request 401 directed to a central network controller 400 by means of a message 402 comprising the data stream identifier.

[0031] Second communication devices, such as the operator control and monitoring station 202, send second datagrams 302 to reserve resources to be provided by the bridges or switches 101-103 for transmitting the data streams, specifying the respective data stream identifier in these datagrams. The resources to be provided by the bridges or switches 101-103 include, in particular, usable transmission time slots, bandwidth, guaranteed maximum latency, number of queues, queue cache, and address cache.

[0032] According to step 1 of the Figure 2According to the flowchart shown, the central network controller 400 continuously checks whether reservation requests need to be met based on the existing first 301 and second datagrams 302. If reservation requests exist, the central network controller 400 determines a path for the respective data stream for the first 301 and second datagrams 302 (step 2). In addition, the central network controller 400 determines the resources required to transmit the respective data stream via the bridges or switches 101-103 in accordance with step 3. The central network controller 400 then checks whether sufficient resources are available to transmit the respective data stream via the bridges or switches 101-103 (step 4). If this is the case, the central network controller 400 reserves the required resources.

[0033] In particular, if sufficient resources are available, the central network controller 400 configures at least the switch 101 connected to the programmable logic controller 201 and the switch 102 connected to the operator control and monitoring station 202 (step 5) so that data frames 300 assigned to data streams are each queued in send queues 111-112, 121-122 of the switches 101, 102 reserved for data streams (step 6). For this purpose, the central network controller 400 transmits messages 403 with corresponding configuration data to the switches 101, 102. The remaining switches 103 can also be configured in a corresponding manner along the respectively determined path.

[0034] If sufficient resources are lacking or uncertain, the central network controller 400 configures at least the switch 101 connected to the programmable logic controller 201 and the switch 102 connected to the operator control and monitoring station 202 (step 7) so that data frames 300 assigned to selected data streams are each queued in a transmit queue 113, 123 for data traffic (step 8) that is handled without a specific quality of service assurance. This transmit queue assignment for the data frames assigned to the selected data streams can be changed according to step 9 after a defined period of time or on an event-based basis, particularly when sufficient resources are available again.

[0035] In the present exemplary embodiment, the switches 101-103 each have send queues 111, 121 reserved at least for first data streams with increased real-time requirements, send queues 112, 122 reserved for second data streams without increased real-time requirements, and send queues 113, 123 for best-effort data traffic. Preferably, the central network controller 400—for example, during a system start—initially reserves resources only for the first data streams, if sufficient availability exists, for transmitting the respective data stream via the switches 101-103 and configures the switches 101-103 to treat the second data streams at least temporarily as selected data streams. In this case, the data frames assigned to the second data streams are thus treated at least temporarily as best-effort data traffic and are accordingly queued in the send queues 113, 123.

[0036] If sufficient resources are available to transmit the first data streams via switches 101-103, the central network controller 400 can advantageously subsequently check whether sufficient resources are available to transmit the second data streams. Accordingly, switches 101-103 are each configured to queue the datagrams assigned to the second data streams in the send queues 112, 122 reserved for the second data streams.

[0037] According to a preferred embodiment, the central network controller 400 configures the switches 101-103, if sufficient resources are available, so that the data streams are each assigned to a virtual local area network (VLAN), and datagrams assigned to data streams are each queued into the respective send queues 111-112, 121-122 reserved for data streams on the basis of this assignment. Furthermore, in this embodiment, if sufficient resources are not available or are uncertain, the central network controller 400 configures the switches 101-103, at least temporarily, so that selected data streams are each assigned to a virtual local area network, based on whose assignment datagrams assigned to the respective selected data stream are each queued into the respective send queue for data traffic that is treated without a specific quality of service assurance or as best-effort data traffic.

[0038] Advantageously, by assigning the virtual local network, it is possible to easily and reliably change whether and with what priority datagrams assigned to a data stream are each queued in a send queue reserved for data streams. For this purpose, the central network controller 400 sends messages 404 with updated configuration data to switches 101-103 affected by such a change. Using the messages 403, 404 with the configuration data or updated configuration data, the central network controller 400 configures the switches 101-103, respectively, by entries in a respective forwarding database (FDB), as to which virtual local network is assigned to a data stream, and whether and with what priority datagrams assigned to a data stream are each queued in a send queue reserved for data streams.For a transmit queue assignment of their data frames 300, the data streams are preferably each identified by their data stream identifier and their assignment to a virtual local area network, in particular according to IEEE 802.1 CB.

[0039] For example, during ongoing operation of the communication system, the central network controller 400 can create an updated prioritization of all data streams in a time- or event-driven manner and, based on the updated prioritization and currently available resources, determine which data streams are to be treated, at least temporarily, as selected data streams or as best-effort data traffic. In particular, the central network controller 400 can configure the switches 101-103 during startup of the communication system so that all data streams are initially assigned to a virtual local network, based on which assignment the data frames 300 assigned to the respective selected data stream are each placed in the respective send queue 113, 123 for best-effort data traffic.After the start of operation, the central network controller 400 creates a prioritization of all data streams and, based on the prioritization and available resources, determines which data streams are to be treated as best-effort data traffic, at least temporarily.

Claims

1. Method for the transmission of time-critical data within a communication system, in which - selected datagrams (300) are assigned to data streams and are transmitted from first communication devices (201) to second communication devices (202) via third communication devices (101-103) comprising paths, - the first communication devices send first datagrams (301) comprising a data stream identifier in each case for notification of subscribable data streams and specify quality-of-service parameters in the first datagrams for the respective data stream, - the second communication devices send, in each case, second datagrams (302) for reserving resources to be provided by the third communication devices for a transmission of the data streams and specify in these the respective data stream identifier, - a higher-level communication control facility (400) determines a path on the first and second datagrams in each case for the respective data stream and, if sufficient resources are available, reserves resources for the transmission of the respective data stream via the third communication devices, - if sufficient resources are available, the higher-level communication control facility (400) configures at least third communication devices (101, 102) connected to a first or second communication device, in each case, such that datagrams assigned to data streams are placed in send queues (111-112, 121-122) reserved for data streams, - the data streams are identified in each case for a send queue assignment of their datagrams (300) by their data stream identifier and their assignment to a virtual local network, - if there is a lack or uncertainty of availability of sufficient resources, the higher-level communication control facility (400) at least temporarily configures at least the third communication devices connected to a first or second communication device in each case, such that datagrams assigned to selected data streams are placed in a send queue (113, 123) for data traffic in each case, which data traffic is not covered by specific quality of service assurance.

2. Method according to claim 1, in which, if sufficient resources are available, the higher-level communication control facility (400) configures at least third communication devices (101, 102) connected to a first or second communication device (201, 202), in each case, such that the data streams are each assigned to a virtual local network and datagrams (300) assigned to data streams are placed in each case in the respective send queues (111-112, 121-122) reserved for data streams based on this assignment, and in which, if there is a lack or uncertainty of availability of sufficient resources, the higher-level communication control facility (400) at least temporarily configures at least the third communication devices connected to a first or second communication device, in each case, such that selected data streams are each assigned to a virtual local network, on the basis of which assignment datagrams assigned to the respective selected data stream are placed in the respective send queue (113, 123) for data traffic in each case, which data traffic is not covered by specific quality of service assurance.

3. Method according to claim 2, in which the assignment of the virtual local network changes whether and / or with what priority datagrams assigned to a data stream are each placed in a send queue reserved for data streams.

4. Method according to one of claims 2 or 3, in which, during ongoing operation of the communication system on a time- and / or event-driven basis, the higher-level communication control facility (400) creates an updated prioritisation of all data streams and determines which data streams are to be treated, at least temporarily, as selected data streams on the basis of the updated prioritisation and on the basis of currently available resources.

5. Method according to one of claims 2 to 4, in which the higher-level communication control facility (400) configures at least the third communication devices (101, 102) connected to a first or second communication device (201, 202), in each case, during a start of operation of the communication system, such that all data streams are each first assigned to a virtual local network, on the basis of which assignment datagrams assigned to the respective selected data stream are placed in the respective send queue (113, 123) for data traffic in each case, which data traffic is not covered by specific quality of service assurance.

6. Method according to claim 5, in which, after the start of operation, the higher-level communication control facility (400) creates a prioritisation of all data streams and determines which data streams are to be treated, at least temporarily, as selected data streams on the basis of the prioritisation and on the basis of available resources.

7. Method according to one of claims 1 to 6, in which the data stream identifiers are provided, in response to a reservation request (401) of a first communication device (201), by the higher-level communication control facility (400), to the respective first communication device.

8. Method according to one of claims 1 to 7, in which the higher-level communication control facility (400) configures at least the third communication devices (101, 102) connected to a first or second communication device (201, 202), in each case, by way of entries in a respective forwarding database, as to which virtual local network is assigned to a data stream in each case and / or whether and / or with what priority datagrams assigned to a data stream are each placed in a send queue reserved for data streams.

9. Method according to one of claims 1 to 8, in which the resources to be provided by the third communication devices (101-103) in particular comprise usable transfer time windows, bandwidth, assured maximum latency, queue count, queue cache and / or address cache in switches or bridges.

10. Method according to one of claims 1 to 9, in which the communication devices (101-103, 201-202) are interconnected via a time-sensitive network, in particular according to IEEE802.3-2018, IEEE 802.1Q-2018, IEEE 802.1AB-2016, IEEE 802.1AS-2011, IEEE 802.1BA-2011 and / or IEEE 802.1CB-2017.

11. Method according to claim 10, in which a forwarding of the selected datagrams (300) is controlled by means of frame preemption, in particular in accordance with IEEE 802.1Q-2018, by means of time-aware shapers, in particular in accordance with IEEE 802.1Q-2018, by means of credit-based shapers, in particular in accordance with IEEE 802.1Q-2018, by means of burst limiting shapers, by means of peristaltic shapers and / or by means of priority-based shapers.

12. Method according to one of claims 9 or 10, in which, in each case, in the third communication devices (101-103), send queues (111, 121) reserved at least for first data streams with increased real-time requirements, send queues (112, 122) reserved for second data streams without increased real-time requirements and send queues (113, 123) for data traffic without specific quality of service assurance, in particular best effort data traffic, are provided, in which, where there is sufficient availability, the higher-level communication control facility (400) only then reserves resources for transmission of the respective data stream for the first data streams via the third communication devices and configures the third communication devices in each case to treat the second data streams at least temporarily as selected data streams.

13. Method according to claim 12, in which, if sufficient resources are available for transmitting the first data streams via the third communication devices (101-103), the higher-level communication control facility (400) checks whether sufficient resources are available for transmitting the second data streams, and accordingly configures the third communication devices in each case to place the datagrams assigned to the second data streams into the send queues (112, 122) reserved for the second data streams.

14. Communication control facility with - at least one connection for connecting to a communication device forwarding datagrams, - wherein the communication control facility (400) is embodied and designed to determine a path in each case for the respective data stream on first datagrams (301) sent by first communication devices (201) for notification of subscribable data streams, and on second datagrams (302) sent by second communication devices (201) for reserving resources to be provided by third communication devices (101-103) for a transmission of the data streams and if there is sufficient availability, to reserve resources for the transmission of the respective data stream via the third communication devices, - wherein, if sufficient resources are available, the communication control facility is further embodied and designed to configure at least third communication devices (101, 102) connected to a first or second communication device (201, 202), in each case, such that datagrams (300) assigned to data streams are each placed in send queues (111-112, 121-122) reserved for data streams, - wherein the communication control facility is further embodied and designed to configure the third communication devices (101-103) such that the data streams are identified in each case for a send queue assignment of their datagrams (300) by their data stream identifier and their assignment to a virtual local network, - wherein, if there is a lack or uncertainty of availability of sufficient resources or if the resources are insecure, the communication control facility is further embodied and designed to at least temporarily configure, in each case, at least the third communication devices connected to a first or second communication device, such that datagrams assigned to selected data streams are each placed in a send queue (113, 123) for data traffic, which data traffic is not covered by specific quality of service assurance.