WO2020211921A1

WO2020211921A1 - Method for transmitting data, network node, network, computer program and computer-readable medium

Info

Publication number: WO2020211921A1
Application number: PCT/EP2019/059669
Authority: WO
Inventors: Feng Chen; Franz-Josef GÖTZ; Marcel Kiessling; An Ninh NGUYEN; Jürgen Schmitt
Original assignee: Siemens Aktiengesellschaft
Priority date: 2019-04-15
Filing date: 2019-04-15
Publication date: 2020-10-22

Abstract

The invention relates to a method for transmitting data in a network having a plurality of network nodes (B1-B10), in which network protected connections for secured data transmission with guaranteed latency are to be established, wherein: a latency is calculated for ports (P1-P5) of network nodes (B1-B10); the number of fan-in ports is incorporated into the calculation of the latency; and logical topologies (9-16, 21-24) for protected connections are established in the network, and for at least one port (P1-P5) of at least one network node (B1-B10), the number of other ports (P1-P5) is determined, at which data of one or more protected connections, which is to be forwarded via the at least one observed port (P1-P5), can arrive according to the established topologies (9-16, 21-24), and the number of other ports (P1-P5) thus determined is incorporated, as the number of fan-in ports, into the calculation of the maximum latency for the at least one observed port (P1-P5). The invention further relates to a network node (B2-B10), to a network, to a computer program and to a computer-readable medium.

Description

description

Method for data transmission, network node, network, computer program and computer-readable medium

The invention relates to a method for data transmission in a particularly industrial network with several network nodes, in which protected connections are to be set up for a secured data transmission, with a particular maximum latency being calculated for ports of network nodes, and a fan in the calculation of the latency -In- number of ports is included. In addition, the invention relates to a network node, a network, a computer program and a computer-readable medium.

In the IEEE, the expansions of the TSN (Time-Sensitive Networking, successor group of the AVB (Audio / Video Bridging Taskgroup) working group mean that periodic or cyclical transmissions, so-called streams, are particularly protected in the network by a secure, deterministic Various hardware extensions were defined to enable a defined forwarding behavior for the selected protected connections, streams. The stream reservation protocol (SRP, see IEEE 802.1 Q-2018) was introduced to set up protected connections, so that the mechanisms do not have to be set up manually and end devices can log on to a network. An automatic configuration of SRP can guarantee a secure transmission within a certain maximum latency for streams with a successful reservation. TSN includes a multitude of standards. R an example in this context, in addition to reservation (IEEE 802.1 Q-2018, IEEE 802.1 Qcc), is time synchronization (IEEE 802.1 AS-REV) and frame preemption (IEEE 802.1 Q-2018). In the context of AVB or TSN, a sender is also referred to as a talker and a receiver as a listener.

For deterministic forwarding within a network node, especially a bridge, it is necessary to determine the maximum delay time within the node. In addition to the cable lengths and the internal processing time, the amount of data with the same priority (in-class interference) plays a role, as this can potentially delay the transmission. The times until a stream transmission can be started can be accelerated by the preemption mechanism, the pausing of a data transmission with a lower priority and later continuation. Within the class, however, all incoming data packets / frames with the same priority from all other ports must be taken into account, since no further differentiation takes place within the class.

So that all delays do not have to be recalculated for each registration, a class is introduced at AVB and the worst case is assumed for the latency calculation. So that statements can be made about the bandwidth, the stream message describes the amount of data for each stream with reference to a class. In this way, the amount of data currently used in the stream can be determined with a successful registration. In the configuration phase of the network, a maximum amount of data must be defined for each class. With AVB, for example, this can be 75% (standard value) of the available bandwidth. Depending on the local resources (FDB entries, queue memory), streams can then be reserved up to the maximum bandwidth.

In a worst-case scenario, one frame from each receiving port and the maximum delay until the stream data begins to be sent is taken into account for the latency calculation. The assumed number of fan-in receiving ports then corresponds to the number of all ports on the node with the exception of the send port (total number of ports on the node minus one or for one Node with n ports n-1). In the case of nodes, in particular bridges with a large number of ports, this creates a very large number of frames that (can) arrive at the same time for the worst-case scenario and therefore a high maximum latency. In reality, however, not all ports of the network nodes are used for protected connections. In this case, a maximum latency, which was determined assuming a number of fan-in ports from all possible receiving ports, i.e. n-1, practically represents an "overestimation".

In order to limit the maximum number in the configuration phase, the parameter "msrpMaxFanlnPorts" was defined. By configuring a value smaller than the actually possible total number of receiving ports (n-1 for n ports), the maximum local latency can be reduced because the Number of ports from "msrpMaxFanlnPorts" is considered for the maximum latency. The number of ports from "msrpMaxFanlnPorts" is reduced compared to n-1 ports. For example, for a network node such as a bridge with 8 ports (nl = 7 possible receiving ports for data forwarding) a reduced number of ports from "msrpMaxFanlnPorts" of 4 should be laid as a basis. Such a reduced number of ports applies “globally” to the respective bridge and thus to all ports considered or serving as send ports.

In the article entitled "Calculating the Delay Added by Qav Stream Queue" (see

http: // www. ieee802. org / 1 / files / public / docs2009 / av-fuller- queue-delay-calculation-0809-v02.pdf) describes the delay calculation for the CBSA Shaper used by AVB (CBSA stands for Credit-based Shaper Algorithm). There, the effect of a lower / reduced number of ports is indicated by the "fanlnLimit" parameter. At that time, the function of the maximum (reduced) number of fan-in ports of MSRP was not yet defined in the final standard. In IEEE 802.1Q-2014 in the annex "L.3.1.2 Fan-in delay" is defined as the influence of the number of receiving ports on the latency of the bridge. The above article served as the basis for the nex L. However, this parameter must be configured before the network is commissioned. When there is a change in operation, the local latency of the bridge changes, and so does the "Accumulated Latency" (added latency of a

Streams along all bridges passed so far) of the streams through the bridge. However, according to the definition of the AVB, a change leads to an error in the stream announcement (especially Talker Advertise) and leads to the removal of all reservations for the affected streams that are transmitted through the bridge in the network.

Based on this, there is a need for a better worst-case analysis.

It is therefore an object of the present invention to specify a method for data transmission in an especially industrial network which enables an improved worst-case analysis.

This object is achieved in a method of the type mentioned in that one or more logical topologies for protected connections are set up in the network, and for at least one port of at least one network node it is determined how many of the other ports of the at least one network node are According to the established logical topology or topologies, data of one or more protected connections that are to be forwarded via the at least one port under consideration can be included, and the number of further ports thus determined as the number of fan-in ports in the calculation of the particular maximum latency for the at least one considered port is included.

The present invention is based on the knowledge that the logical topology used plays a role in the forwarding of data of protected connections, in particular stream data. Several different logical topologies are possible, especially in networks with several applications. Only those for connecting one Logical topology required ports of a bridge are used and the stream announcement (also referred to as a stream description and given for example by a talker advertise) is only forwarded via these ports.

The basic idea of the present invention consists in taking into account or using the logical topologies set up in a network for an adaptation of the worst-case consideration.

In the case of a group (a logical topology usually exists for a group of connected or neighboring end devices and network nodes), possible interference for a stream can only come from other streams in the same group. When using several groups / several logical topologies, the interference can come from all groups / logical topologies that use the respective send port. If these do not overlap, there is no mutual interference. Depending on the logical topologies in a network, a much smaller number of ports can be used to determine the maximum latency of a bridge than the number of fan-in ports, even though many ports make reservations for streams.

Therefore, depending on the logical topologies set up in the network, the worst-case analysis is carried out with a correspondingly adapted, lower number of ports (worst-case number of receive ports). The logical topologies are in a network e.g. by configuring a VLAN ID for each group (for example, one field bus segment with actuators and sensors and the associated, in particular, virtual control) using management or by configuring it through MVRP in the network, before the individual reservations of streams are made.

Only those of the other ports are preferred as fan-in ports and are included in the number of fan-in ports, which belong to at least one logical topology to which the respective port under consideration also belongs.

Furthermore, in particular a maximum latency is calculated for the at least one considered port. An accumulated latency, in particular a maximum accumulated latency, can also be calculated.

To determine the number of latency ports for a send port, the ports used in the logical network topologies and the ports to which end devices that communicate via the logical network topologies are connected are taken into account as possible fan-in ports. An individual determination of the latency is carried out for each port of a device, in that each port is considered as a send port. Network ports that are not used in the logical topologies of the (in each case considered) send port are, however, not considered / taken into account. In other words, in contrast to the state of the art, these ports are not included in the number of fan-in ports.

The fan-in port number determined according to the invention taking into account the logical topology (s) for at least one transmission port of stream data is then alternatively to a fan-in port number of n-1 (for network nodes with n ports) or alternatively to one Although it is reduced compared to n-1, it is used for the latency calculation in each case for an entire network node (for example in accordance with the “fanln limit”) specified number of fan-in ports.

Since, according to the invention, ports that can be sent via the data of protected connections are considered individually and an associated number of fan-in ports is determined individually for them, taking into account the set up logical topology (s), there are also asymmetrical fan-in constellations -Port number possible, which is particularly advantageous in the industrial environment, where there is often a data exchange in a star-shaped constellation namely between a central control (or several provided at a central point, especially virtual controls) and several fieldbus segments is required. In such a case, for example, more fan-in ports can be used for one or more considered (sending) ports of a network node according to the established logical topology (s) (for example, several virtual networks for the several fieldbus segments with associated control) belong to one or more other considered (send) ports, to which, for example, only one fan-in port belongs.

It should be noted that each port of a network node can in principle be both a send and receive port (and fan-in port) or can serve both as a send and receive port. The maximum latency is to be determined for a port if data is to be forwarded / sent via this port, i.e. for a port if this has the role of a send or output port for the data transmission under consideration. If you consider a port as a send port, all other ports of the (respective) node - with regard to these ports as send ports - are possible receiving ports, via which data could in principle arrive that are to be forwarded via the port under consideration (send port).

In the context of the present invention, a port is (in each case) considered which represents a transmission port for data from one or more protected connections. The further ports in relation to the (each) considered send port are then (each) possible receive ports. For the transmit port or ports under consideration, which each belong to one or more logical topologies or are located in one or more logical topologies, the number of receive ports that belong to the same logical topology (s) is determined. lie therein), i.e. also to the logical topology or topologies of the send port.

By considering logi

cal / virtual topologies, which are particularly suitable for Stream reservation are set up in the network, the number of input / receiving ports, which can represent an additional latency for the forwarding device, can be limited or reduced compared to the prior art. The delay in the local network node / the local bridge is adapted to the logical / virtual topology, which results in a lower forwarding time.

The shorter forwarding time means that fewer internal resources have to be reserved for a reservation (queue resources). This allows more protected connections, especially streams, to be reserved.

Since the latency for _real-Z eitanwendungen plays an important role, individual network can network node, such as Bridges larger networks may be used or the application cycles may be reduced (increasing the quality of control) by a lower latency.

Following the calculation according to the invention of the particular maximum latency of a port under consideration, preferably a plurality of ports under consideration, at least one protected connection can be set up which uses the port or ports as send ports, and data can be transmitted via this.

A network node can also be integrated into a device, for example a terminal. A latency calculation can also be carried out in the manner according to the invention for one or more transmission ports of network nodes integrated in devices, for example terminals, taking into account one or more logical topologies set up in the network.

In industrial networks, end devices with integrated network nodes are often given by simple field devices that include at least one sensor and / or at least one actuator or with at least one sensor and / or at least one Actuator connected or connectable, and preferably have an integrated switch.

An example of a protected connection is a stream as defined by the Audio / Video Bridging (AVB) Task Group and in particular by the Time-Sensitive Networking (TSN) Task Group in the international IEEE 802.1 standard. For a protected connection, resources are or are appropriately reserved at the network nodes involved in a manner previously known from the prior art. A protected connection is characterized in particular by a unique identifier assigned to this, in particular a stream identifier, preferably in the form of a stream ID.

Of course, it is possible that an adapted number of fan-in ports is determined for several ports, preferably several network nodes, taking into account the logical topology or topologies set up in the network and used for the latency calculation for each of the several ports. Correspondingly, a further embodiment is characterized in that, for several ports, several network nodes are determined at how many of the further ports of the respective network node, based on the established logical topology or topologies, data from one or more protected connections via the respective port under consideration are to be forwarded, and the number of further ports determined in this way is included as the number of fan-in ports in the calculation of the maximum latency for each of the several ports considered.

This is particularly preferably done for each port which, according to the logical topology (s), represents or can represent a send port for data ge protected connections and preferably belongs to a network node with more than two ports. In a further development, it is therefore determined for each port that represents a send port for data from one or more protected connections according to the set up logical topology or topologies, at how many of the respective wide ren ports of the respective network node due to the established logical topology or topologies data of one or more protected connections that are to be forwarded via the respective port under consideration, and the number of further ports determined in this way as fan-in port number in the Calculation of the maximum latency for each of these ports is included. The required latency information is then available for all transmission ports of data of protected connections, in particular stream data, belonging to the or at least one of the logical topologies set up.

It is also possible that in a network for each transmission port of each network node it is determined to how many of the further ports of the respective network node according to the established logical topology or topologies data of one or more protected connections that are to be forwarded via the respective port under consideration , and the number of additional ports determined in this way is included as the number of fan-in ports in the calculation of the maximum latency for each of these ports. It should be noted that this can be dispensed with for network nodes that only have two ports. Accordingly, this determination can be made for all network nodes with more than two ports.

The respective logical topology or the respective logical topology comprises in an advantageous embodiment a virtual network and / or a stream class or is given by a virtual network and / or a stream class. The respective logical topology or the respective logical topology preferably comprises the entire or only a partial area of the physical network. The or each of the virtual networks (VLANs) then expediently has a VLAN ID or the virtual network or networks are (each) configured by a VLAN ID. Each virtual network usually has an active topology ("Active Topology" - according to IEEE 802.1 Q). The logical topology to be considered is then in particular still restricted by the SRP domain (according to IEEE 802.1 Q). For each stream class is the area in the network in which these is defined by SRP in the form of the SRP domain (see in particular the "SRPdomainBoundaryPort" value in the IEEE 802. IQ standard - Chapter 35 Stream Reservation Protocol (SRP)) and only includes connections between devices that support the respective stream class.

The or in the case of several of the respective logical topology is also preferably one which is set up for a stream reservation in the network.

The or, in the case of more than one, the respective logical topology can furthermore preferably belong to a coherent group of neighboring terminals and network nodes.

At least one logical topology can also be given by a virtual network configured for a group of terminals and network nodes, preferably with an associated VLAN ID. If a plurality of logical topologies are set up in the network, these can each be given by a virtual network configured for a group of terminals and, in particular, network nodes connecting them, preferably with an associated VLAN ID. Then at least one terminal and / or at least one network node can be part of at least two different groups. In other words, there can be overlaps, one or more terminals and / or one or more network nodes can be a member or part of more than one logical topolo

gie / associated group or belong to more than one logical topology / associated group.

In a further advantageous embodiment, the respective group or groups comprises a fieldbus segment with actuators and / or sensors and at least one associated, in particular virtual, controller.

The sensors and actuators must continue to be supplied with data, particularly when the controls (e.g. PLC) of fieldbus systems are virtualized. Are several fieldbus segments te with sensors and / or actuators and at least one associated controller (PLC) are available, and if the controls are implemented in a virtualized manner at a central point, for example on a high-performance industrial PC, all fieldbus segments are connected to the industrial PC , so a star-shaped configuration. For each fieldbus segment including the respective virtualized controller, a logical topology belongs in particular, or a logical topology is defined by the corresponding group of terminals and network nodes. In particular, a virtual network and / or a stream class can be set up for each fieldbus segment with control, which or which forms one of the several logical topologies in the network. The procedure according to the invention has proven particularly advantageous for such a constellation. At the transmission ports, in particular of network nodes that are between the central industrial PC with the virtualized controls and the respective associated sensors and / or actuators, at least one direction, in particular in the direction of the sensors and / or actuators, can be based on the logical Topologies significantly lower number of ports can be determined.

A further advantageous embodiment ensures that data of protected connections to be forwarded via the respective send port of a respective network node cannot arrive at the respective network node via a number of receiving ports that exceeds the number of fan-in ports.

Monitoring or checking can be introduced to maintain the maximum number of ports.

A stream description can be distributed in the network to set up protected connections. Then every network node that receives a stream description via one of its ports (receiving port) and forwards it via another of its ports (sending port) can check whether the one ne port (receiving port) has already been taken into account for forwarding via the other port (sending port). In the event that one port (receiving port) has not yet been taken into account and the maximum number of ports has already been reached, it is preferred to provide the stream description with an error code.

When the stream description is passed on (e.g. Talker Adver- tise, see IEEE 802.1) in the network, a check can also be made at each port (potential send port) to determine whether the associated receive port has already been taken into account for the forwarding at this port. If this is not the case and the maximum number of ports has already been reached, the stream description is provided with an error code (Talker Failed) and logins to the stream via this port are excluded. As soon as a reservation of a

Streams takes place, this is expediently repeated for all previously passed stream descriptions without reservation, since the number of receiving ports still available could have changed to 0. This ensures that the information distributed to potential other listeners in the network is kept up-to-date and that, after logging in, a further logon that is no longer possible is signaled from the network to the other network devices (network nodes) and end devices. However, as with SRP, a rejection of the reservation, which would have been possible based on the information prior to the registration, cannot be completely ruled out.

In other words, the process corresponds to the checking of the available bandwidth defined in SRP when the stream description is passed on. When the data is passed on, a check is made as to whether a registration to the stream would be possible with the current reserved bandwidth. If another stream is registered, this also changes and the check must also be repeated for all streams without a reservation. If the bandwidth for streams is no longer sufficient, the stream description (Talker Advertise) is marked with a Provide an error code (Talker Failed) and prevent the reservation for this stream in the further network via this port and the end devices are informed that the affected streams cannot be made available. Analogous to this, an intelligent "fan-in" check of the receiving ports can be implemented.

Another object of the invention is a network node which forms and / or is set up to carry out the method according to the invention.

The network node according to the invention can be, for example, a bridge or a switch.

The network node according to the invention expediently has at least two ports.

The network node according to the invention is furthermore preferably designed and / or set up to calculate a maximum latency, in particular, a number of fan-in ports being included in the calculation of the latency, and to determine how for at least one of its ports many of its other ports, based on one or more logical topologies for protected connections that are set up in a network in which the network node participates, can receive data from one or more protected connections that are to be forwarded via the at least one considered port, and to include the number of further ports determined in this way as the number of fan-in ports in the calculation of the maximum latency for the at least one considered port.

The invention also relates to a network, in particular for an automation system and / or manufacturing system, with one or more network nodes according to the invention. The network includes, in particular, at least one, preferably several, controllers and associated field devices. The network is expediently Ethernet-capable; it is in particular an Ethernet-based network. In particular, so that protected connections, for example streams with guaranteed quality of service (English: Quality of Service, QoS) are supported, the network or, in particular, at least the network nodes involved are preferably AVB- or TSN-capable, supports or support the device in particular protected connections with reserved network resources at the participating network nodes. AVB and TSN are sufficiently known from the prior art. A reservation protocol, for example SRP and / or MSRP, in particular in accordance with IEEE 802.1 Q, is preferably used to set up or establish protected connections, in particular streams. The network node or nodes according to the invention are preferably designed and / or set up accordingly.

The present invention also relates to a computer program which comprises program code means for performing the steps of the method according to the invention.

Finally, the subject matter of the invention is a computer-readable medium which comprises instructions which, when they are executed on at least one computer, cause the at least one computer to carry out the steps of the method according to the invention.

The computer-readable medium can be, for example, a CD-ROM or DVD or a USB or flash memory. It should be noted that a computer-readable medium should not be understood exclusively as a physical medium, but rather such a medium can also be present, for example, in the form of a data stream and / or a signal that represents a data stream.

Further features and advantages of the present invention who based on the following description of the invention Embodiments with reference to the accompanying drawing voltage clearly. In it is

FIG. 1 shows a purely schematic representation of an industrial network in which several logical topologies are set up;

FIG. 2 shows several network nodes of an industrial network in a purely schematic representation;

FIG. 3 shows the industrial network from FIG. 1, the associated number of fan-in ports being indicated on some transmission ports of some logical topologies; and

FIG. 4 shows a purely schematic representation of a further industrial network.

The same components or elements are provided with the same reference symbols in the figures.

FIG. 1 shows an industrial, Ethernet-based network with several network nodes B1-B9 in a purely schematic representation. The network nodes B1-B10 support TSN standards, in particular the reservation of network resources for real-time data transmission with guaranteed latency, so that at least the segment of the network spanned by them is TSN-capable. The network nodes B2-B10 are provided by bridges that form a redundant backbone network (segment) with or in a ring topology. Further networks or network segments (or sub-networks) 1, 2, 3 that do not support a TSN are connected to network node B2.

A central industrial PC 4, on which two virtualized / virtual memory-programmable controllers 5 (also referred to as vSPS) are provided or implemented, takes part in the industrial network. The network node Bl is a provided or implemented on the industrial PC 4 vir- Current switch (vSwitch). In the exemplary embodiment described here, the further network nodes B2-B10 are separate, physical bridges B2-B10 from the industrial PC 4.

There are also two ("physical") programmable logic controllers 6, which are also separate from the industrial PC 4 and located elsewhere in the network, as well as a large number of distributed field devices with an integrated switch 7 or distributed field devices without an integrated switch 8, each comprising a sensor and / or actuator or being connected to such.

The controllers 5, 6 and the field devices 7, 8 represent end devices (in some cases end devices 7 with an integrated network node).

The actuators must cyclically receive control values in a manner known per se from one of the controllers 5, 6 in order to act accordingly on a technical process not shown in any further detail in the figures. The technical process can be monitored in a well-known manner by means of the sensors. Specifically, these record measured values, which are also to be transmitted cyclically to an associated controller 5, 6. The control values and the measured values are transmitted as user data content of data packets and the transmission must take place in real time. For this purpose, protected connections, in this case TSN streams in the sense of IEEE 802.1, are to be set up in the network. This includes the publication of stream announcements or stream descriptions, in particular in the form of talker advertisements, and the reservation of resources at the network nodes involved, specifically both on bridges B1-B9 and integrated switches of the field devices 7.

Several logical topologies 9-13 are set up in the network for stream reservation. Each respective logical topology 9-13 is provided by a virtual network (VLAN), each with the associated VLAN ID and / or a stream class.

Each logical topology 9-13 belongs to a coherent group of neighboring terminals 5-8 and network nodes, which in turn includes both the separate bridges B1-B9 and integrated switches. Specifically, each of the logical topologies 9-13 is given by a virtual network (VLAN) configured for a group G1-G5 of terminals 5-8 and network nodes B1-B10 with the associated VLAN ID.

In FIG. 1, the group members belonging to the respective logical topology 9-13 are framed by a border line. A solid line is used for the logical topology 9, a dash-dotted line for the logical topology 10, a double-dotted line for the logical topology 11, a dashed line for the logical topology 12 and a dotted line for the logical topology 13.

The groups G1-G5 and the associated logical topologies 9-13 are as follows in the exemplary embodiment described here.

One of the virtual controllers 5 of the industrial PCS 4, specifically the vSPS 6 on the right in FIG. 1, the bridges B1-B8 and the lower controller 6 in FIG. 1, which is connected to the node B8, belong to the group Gl and logical topology 9 .

The group G2 and logical topology 10 also include the vSPS 5 on the right in FIG. 1 on the industrial PC 4, the nodes B1-B7 and the three field devices 7, 8 arranged in a line topology at the bottom left in FIG the first field device 7 of the line is connected to the node B4.

The group G3 and logical topology 11 include the vSPS 5 on the left in FIG. 1 on the industrial PC 4, the nodes B1-B7 and the six field devices arranged in a ring topology 8, one of which is connected to node B5 and one of which is connected to node B6.

The group G4 and logical topology 12 include the lower controller 6 in FIG. 1, which is connected to the node B8 and the nodes B8-B10 and the five field devices 7, 8, which are connected to the nodes B8, B9 and B10, partly indirectly are connected via further field devices 7.

A terminal, specifically the lower physical control 6 in FIG. 1, and several of the bridges B1-B10 are each part of more than one group G1-G5, that is, each belong to more than one logical topology 9-13. The field devices 7, 8, on the other hand, only belong to one group G1-G5 and logical topology 9-13.

Each of the groups G1-G5 comprises a field bus segment with actuators and / or sensors and at least one controller 5, 6.

The logical topology 9 is used so that the physical control 6 can communicate with the higher-level virtualized control 5 belonging to group Gl on the industrial PC 4. The logical topology 10 is used so that the three field devices 7, 8 can communicate with group G2 with the associated virtualized controller 5. The logical topology 11 is used to enable the six field devices 7 of group G3 to communicate with the associated virtualized controller 5 on the industrial PC 4. The logical topology 12 is used to ensure that the field devices 7, 8 of the group G4 can communicate with the associated local, physical controller 6 and the logical topology 13 that the three field devices 7, 8 of the group G5 with the associated local len, physical controller 6 can communicate.

In other words, with regard to group G4, there is a local control with fieldbus communication and, in addition, communication between the local control 6 and the higher-level virtualized control 5 of group Gl. In terms of Group G5 means that there is only purely local real-time communication in the associated virtual network (VLAN).

For the deterministic forwarding of stream data within the network nodes B1-B10 and the switches integrated in the field devices 7, it is necessary to determine the maximum delay time within the respective node B1-B10. In addition to the cable lengths and the internal processing time, the volume of data with the same priority (in-class interference) plays a role, as this can potentially delay the transmission. Within the class, all incoming data packets / frames with the same priority from all other ports P1-P5 must be taken into account, since there is no further differentiation within the class.

So that all delays do not have to be recalculated for each registration, a class is introduced at AVB and the worst case is assumed for the latency calculation. So that statements can be made about the bandwidth, the stream message describes the amount of data for each stream with reference to a class. In this way, the amount of data currently used in the stream can be determined with a successful registration. In the configuration phase of the network, a maximum amount of data must be defined for each class. With AVB, for example, this can be 75% (standard value) of the available bandwidth. Depending on the local resources (FDB entries, queue memory), streams can then be reserved up to the maximum bandwidth. In a worst-case scenario, a frame / data packet from each receiving port and the maximum delay until the stream data begins to be sent are taken into account for the latency calculation.

The assumed number of fan-in receiving ports then corresponds to the number of all ports of the node with the exception of the sending port (total number of ports of the node minus one or for a node with n ports n-1). In the case of nodes with a very large number of ports P1-P5, this creates a very large number of frames that (can) arrive at the same time for the worst-case scenario and therefore a high maximum latency. In the present case, the nodes B2 to B8 each have 8 ports. It should be noted that only some of the ports P1-P5 are shown in the figures and, for the sake of clarity, not all ports P1-P5 of all network nodes B1-B10 are provided with reference symbols in FIG.

In reality, however, often not all ports P1-P5 of network nodes B1-B10 are used for protected connections. This is also the case in the scenario shown as an example in FIG. In this case, a maximum latency, which was determined assuming a number of fan-in ports from all possible receiving ports, i.e. n-1, practically represents an "overestimation". For 8 ports, a fan In-Port number of 7 for each considered port serving as a send port.

In order to limit the maximum number in the configuration phase, the parameter "msrpMaxFanlnPorts" was defined. By configuring a value smaller than the actually possible total number of receiving ports (n-1 for n ports), the maximum local latency can be reduced because the Number of ports from "msrpMaxFanlnPorts" is considered for the maximum latency. The number of ports from "msrpMaxFanlnPorts" is reduced compared to n-1 ports. For example, for a network node such as a bridge with 8 ports (nl = 7 possible receiving ports for data forwarding) a reduced number of ports from "msrpMaxFanlnPorts" of 4 should be laid as a basis. Such a reduced number of ports applies “globally” to the respective bridge B2-B7 and thus to all ports considered or serving as send ports.

The logical topology used plays a role in forwarding data from protected connections, in particular stream data. Especially in networks with several applications, several different logical topologies 9- 13 possible, as shown schematically in FIG. Only the ports of a bridge B2-B7 required to connect a logical topology 9-13 are used and the stream announcement (also referred to as a stream description and given, for example, by a talker advert) is only forwarded via these ports. If there is only one group, possible interference for a stream can only come from other streams in the same group. When using several groups G1-G5 / logical topologies 9-13 (see FIG. 1), the interference can come from all groups G1-G5 that use the transmission port (considered in each case). If these do not overlap, there is no influence.

This is illustrated again in FIG. 2, which shows a further, purely exemplary industrial network. Only a few network nodes in the form of bridges B1-B7 are shown, but participating terminals are not shown again. In the example according to FIG. 2, three logical topologies 14, 15, 16 are set up in the network. Since these do not overlap in the scenario shown in FIG. 2, there is no mutual influence. In FIG. 2, on the right, the nodes B1, B2 and B5 are again shown separately, with the number of ports P1-P4 used in the respective logical / virtual topology 14-16 being specified in addition to the nodes B1, B2, B5.

This makes it clear that, depending on the logical topologies 9-16 set up in a network in particular for stream reservation, a much smaller number of ports can be used as the number of fan-in ports for determining the maximum latency of the bridges B1-B10, although there are many Ports P1-P5 make reservations for streams.

The invention therefore provides that for at least one port P1-P5 at least one network node B1-B10 is determined at how many of the further ports P1-P5 of the at least one network node B1-B10 according to the established logical topologies 9-16 data of one or more protected connections that are to be forwarded via the at least one considered port P1-P5, and the thus determined number of further ports P1-P5 as fan-in port number in the calculation of the in particular, maximum latency for the at least one considered port P1-P5 is included.

In the exemplary embodiment described here, for each port P1-P5, which, in accordance with the established logical topologies 9-16, represents a send port for data from one or more protected connections (and which in particular to a network node B2-B10 with more than two ports P1- P5 belongs) determines how many of the respective further ports P1-P5 of the respective network node B2-B10 according to the established logical topologies 9-16 data of one or more protected connections that are to be forwarded via the respective port PI PS can be received , and the number of further ports P1-P5 determined in this way flows into the calculation of the maximum latency for each of these ports as the number of fan-in ports.

Specifically, only those of the (each) additional ports P1-P5 are considered fan-in ports and are included in the number of fan-in ports that belong to at least one logical topology 9-16, to which the port under consideration also belongs P1-P5 heard.

The fact that the number of fan-in ports is calculated for each of these ports P1-P5 of nodes B2-B10 means that individual ports are considered and different numbers of fan-in ports are obtained for different ports P1-P5 of a node B2-B10 can be, which represents a significant difference compared to the prior art. Asymmetrical constellations are also possible at nodes B2-B10. FIG. 3 again shows the network according to FIG. 1, the resulting number of fan-in ports reduced in the manner according to the invention, at least for some ports P1-P5 of some network nodes B2-B10, for example, each directly next to ports P1-P5 is registered.

The reduction in the number of fan-in ports according to the invention becomes particularly clear if one considers node B3, of which five ports P1-P5 are shown. For the two ports PI and P2 of this node there is a number of fan-in ports of only 1, since only one of the other 7 ports (of which only four more are shown in the figure) also correspond to those logical topologies 9, 10 and 11 ge, to which the port PI or P2 - each viewed as a send port - belongs, and can only receive data of protected connections via a further port PI, P2 according to the established logical topologies 9-13, which can be received via the (each) considered port PI, P2 are to be forwarded.

The procedure according to the invention has proven to be particularly advantageous when data exchange in a star-shaped constellation, for example between a central controller or several, in particular virtual controllers, provided at a central location and several fieldbus segments is required. Such a constellation is shown purely schematically and by way of example in FIG. Here is an industrial PC 4 on which a total of four virtualized memory-programmable controllers 5 (vSPS) are provided or implemented, and which - as in FIGS. 1 and 3 - has an internal switch B1, via a separate bridge B2 a total of four field bus segments 17-20 is connected. The bridge B2 is to be understood here as an example. Of course, there can also be several nodes between the industrial PC 4 and the field bus segments 17-20.

Each field bus segment 17-20 can comprise several field devices and further nodes, as shown in FIG. The associated logical topologies 21-24 are here simply indicated by arrows with solid, dashed, dash-dotted or dotted lines.

In such a case, for example, many fan-in ports (in this case P2, P3, P4 and P5) can belong to one or more fan-in ports (in this case P2, P3, P4 and P5), for example PI of node B2, according to the established logical topologies 21-24 several other considered (send) ports, for example P2, P3, P4 or P5, significantly fewer, in the present case only one, namely PI. Such an “asymmetrical” number of fan-in ports is determined according to the invention and taken into account. The number of fan-in ports determined according to the invention is also entered in FIG. 4 next to the (transmission) port P1-P5.

One obtains a very advantageous result compared to a number of fan-in ports reduced to 4 according to the prior art according to "msrpMaxFanlnPorts", for example, which would apply to all ports P1-P5 of node B2 across the board / "globally" the “overestimation” that would result for a “global” number of fan-in ports (of 4, for example) for ports P2 to P5 is avoided according to the invention by taking into account the logical topologies 21-24.

By considering logi

rule / virtual topologies 9-16, 21-24, which are set up in particular for stream reservation in the network, the number of input / receiving ports, which can represent additional latency for forwarding, ge compared to the prior art can be significantly limited or . be reduced. The delay in the local network node / the local bridge B2-B10 is passed on to the logi

cal / virtual topologies 9-16, 21-24 adapted, which results in a lower forwarding time.

Due to the lower forwarding time, fewer internal resources have to be reserved for a reservation (queue resources). will be. This allows more protected connections, especially streams, to be reserved.

Since the latency for _real-Z eitanwendungen plays an important role, individual network can lower latency network node B2-B10 larger networks may be used or the application cycles may be reduced (increasing the Quali ty of the control).

Following the calculation according to the invention of the particular maximum latency of the respective ports P1-P5 under consideration, at least one protected connection can be set up that uses the port (s) P1-P5 as send port, and data can be transmitted via this port in real time .

Monitoring or checking can be carried out to maintain the maximum number of ports. In particular, it can be ensured that data of protected connections to be forwarded via the respective send port P1-P5 of a respective network node B1-B10 cannot arrive at the respective network node B1-B10 via a number of reception ports PI PS that corresponds to the number of fan-in ports exceeds. Every network node B1-B10 that receives a stream description via a port (receiving port) P1-P5 and forwards it via another port (sending port) P1-P5 can check whether the one port (receiving port) P1-P5 is suitable for forwarding via which has already been taken into account at the port (send port) P1-P5. In the event that one port (reception sport) P1-P5 has not yet been taken into account and the maximum number of ports has already been reached, the stream description is preferably provided with an error code. As soon as a reservation of a

Streams takes place, this is expediently repeated for all previously passed stream descriptions without reservation, since the number of receiving ports still available could have changed to 0.

In other words, the process corresponds to the checking of the available bandwidth defined in SRP during the transfer the stream description. When the data is passed on, a check is made as to whether a registration to the stream would be possible with the current reserved bandwidth. If another stream is registered, this also changes and the check must also be repeated for all streams without a reservation. If the bandwidth for streams is no longer sufficient, the stream description (Talker Advertise) is provided with an error code (Talker Failed) and the reservation for this stream in the further network via this port is prevented. Analogous to this, an intelligent "fan-in" check of the receiving ports can be implemented.

It should be noted that bridges B2-B7 from FIGS. 1 and 3 and nodes B1-B7 from FIG. 2 are all exemplary embodiments of network nodes according to the invention which are designed and / or set up to carry out the described exemplary embodiment of the method according to the invention.

The industrial networks shown in FIGS. 1 to 3 are also exemplary embodiments of networks according to the invention.

Although the invention has been illustrated and described in more detail by the preferred exemplary embodiment, the invention is not restricted by the examples disclosed and other variations can be derived therefrom by the person skilled in the art without departing from the scope of the invention.

Claims

1. A method for data transmission in a particularly industrial network with several network nodes (B1-B10), in which protected connections are to be set up for secure data transmission, with latency for ports (P1-P5) of network nodes (B1-B10) is calculated, and a number of fan-in ports is included in the calculation of the latency, characterized in that

one or more logical topologies (9-16, 21-24) are set up for protected connections in the network, and at least one network node (B1-B10) is determined for at least one port (P1-P5), at how many of the others Ports (P1-P5) of the at least one network node (B1-B10) according to the established logical topology or topologies (9-16, 21-24) Data of one or more protected connections that are transmitted via the at least one considered port (PI PS) are to be forwarded, can be received, and the thus determined number of further ports (P1-P5) is included as the number of fan-in ports in the calculation of the latency for the at least one port under consideration (P1-P5).

2. The method according to claim 1,

characterized in that

only those of the other ports (P1-P5) are considered to be fan-in ports and are included in the number of fan-in ports that belong to at least one logical topology (9-16, 21-24), which also includes the or the respective considered port (PI PS) belongs.

3. The method according to claim 1 or 2,

characterized in that

the or the respective logical topology (9-16, 21-24) is set up for a stream reservation in the network, and / or the or the respective logical topology (9-16, 21-24) for a virtual network and / or a Stream class includes or is given by it.

4. The method according to any one of the preceding claims, characterized in that

which or the respective logical topology (9-16, 21-24) belongs to a coherent group (G1-G5) of adjacent end devices (4, 6, 7, 8) and network nodes (B1-B10).

5. The method according to any one of the preceding claims, characterized in that

at least one logical topology (9-16, 21-24) for a virtual network configured for a group (G1-G5) of terminals (4, 6, 7, 8) and network nodes (B1-B10) is given, with preferred

several logical topologies (9-16, 21-24) are set up, each given by a virtual network configured for a group (G1-G5) of terminals (4, 6, 7, 8) and network nodes (B1-B10) are, where at least one terminal (4, 6, 7, 8) and / or at least one network node (B1-B10) is part of at least two different groups (G1-G5).

6. The method according to claim 5,

characterized in that

which or each group (G1-G5) comprises a field bus segment (17-20) with actuators and / or sensors and at least one controller (5, 6).

7. The method according to claim 5 and 6,

characterized in that

several groups (G1-G5) each comprise a virtual controller (5) and the virtual controllers (5) of several groups (G1-G5) are provided on a terminal (4), and this terminal (4) is part of the groups (G1- G5) is at least two different logical topologies (9-16, 21-24).

8. The method according to any one of the preceding claims, characterized in that

for each port (P1-P5), which has a send port according to the established logical topology or topologies (9-16, 21-24) (P1-P5) represents data from one or more protected connections, it is determined at how many of the further ports (P1-P5) of the respective network node (B1-B10) according to the established logical topology or topologies (9-16 , 21-24) for data from one or more protected connections that are to be forwarded via the respective port (P1-P5) under consideration, and the number of further ports (P1-P5) determined in this way as the number of fan-in ports is included in the calculation of the latency for each of these ports (P1-P5).

9. The method according to any one of the preceding claims, characterized in that

it is guaranteed that data of protected connections to be forwarded via the respective port (P1-P5) of a respective network node (B1-B10) to be forwarded do not arrive at the respective network node (B1-B10) via more further ports (P1-P5) than are taken into account in the number of fan-in ports for the respective port under consideration (P1-P5).

10. The method according to claim 9,

characterized in that

a stream description is distributed in the network to set up protected connections, and each network node (B1-B10) that receives a stream description via one of its ports (P1-P5) and forwards another of its ports (P1-P5) checks whether one port (P1-P5) has already been taken into account for forwarding via the other port (P1-P5), and preferably in the event that one port (P1-P5) has not yet been taken into account and the maximum number of ports has already been reached is, the stream description is provided with an error code.

11. Network node (B2-B10) which is designed and / or set up to carry out the method according to one of the preceding claims.

12. Network node (B2-B10) according to claim 11,

characterized in that

the network node (B2-B10) is designed and / or set up to calculate a latency, a number of fan-in ports being included in the calculation of the latency, and to determine for at least one of its ports (P1-P5) on how many of its other ports (P1-P5) according to one or more logical topologies (9-16, 21-24) for protected connections that are set up in a network in which the network node (B2-B10) participates , data from one or more protected connections that are to be forwarded via the at least one considered port (P1-P5) can be received, and the number of further ports (P1-P5) determined in this way as the number of fan-in ports in the Calculation of the latency for the at least one considered port (P1-P5) to flow into.

13. Network, in particular for an automation system and / or manufacturing system, with at least one network node according to claim 11 or 12.

14. Computer program comprising program code means for implementing the method according to one of claims 1 to 10.

15. A computer-readable medium comprising instructions which, when executed on at least one computer, cause the at least one computer to perform the steps of the method according to any one of claims 1 to 10.