WO2020125987A1

WO2020125987A1 - Method for data communication having a predefined request for fail-safe protection, communication device, computer program, and computer-readable medium

Info

Publication number: WO2020125987A1
Application number: PCT/EP2018/086124
Authority: WO
Inventors: Feng Chen; Franz-Josef GÖTZ; Marcel Kiessling; An Ninh NGUYEN; Jürgen Schmitt
Original assignee: Siemens Aktiengesellschaft
Priority date: 2018-12-20
Filing date: 2018-12-20
Publication date: 2020-06-25

Abstract

The invention relates to a method for data communication in a redundantly operatable network having a plurality of network nodes (1), wherein between at least two communication partners (2, 3), data are to be transmitted. A predefined request for fail-safe protection of the data transmission is present, and in the network, two or more different redundancy modes (Ma-Mn) are supported. The redundancy modes (N, SWO, E2E, SP) supported in the network, in each case can be communicated, in particular to at least one of the at least two communication partners (2, 3), via an associated virtual network (B VLAN), in which the respective redundancy mode (M1-Mn) can be used. From the redundancy modes (M1-Mn), a suitable redundancy mode (M1-Mn) is automatically selected based on the predefined request for fail-safe protection, and preferably, data between the at least two communication partners (2, 3) are transmitted via the virtual network (B VLAN) associated with the automatically selected redundancy mode (M1-Mn). The invention further relates to a communication device, to a computer program, and to a computer-readable medium.

Description

description

METHOD FOR DATA COMMUNICATION WITH SPECIFIC REQUIREMENTS FOR DEFAULT SAFETY, COMMUNICATION DEVICE, COMPUTER PROGRAM AND

COMPUTER READABLE MEDIUM

The invention relates to a method for data communication in a redundantly operable, in particular industrial, network with a plurality of network nodes. Furthermore, the invention relates to a communication device, a computer program and a computer-readable medium.

Communication interruptions are a major problem, particularly in industrial networks, which connect a large number of industrial automation devices of an automation system to one another, for example for manufacturing or process automation. Due to messages that are not or not completely transmitted, in particular data frames, a transition of a system into prevent a safe operating state or remain in such a state. In the worst case, there may even be a complete failure of, for example, a production system or an expensive downtime.

Real-time communication protocols such as PROFINET, PROFIBUS or Real-Time Ethernet are mainly used for communication in industrial communication networks.

In order to be able to compensate for failures in communication connections or devices, communication protocols that guarantee redundancy have been developed. The (Rapid) Spanning Tree Protocol ((R) STP) and the Media Redundancy Protocol (MRP) can be mentioned here purely as examples, via which highly available, redundantly operable industrial networks can be obtained. Through the Spanning Tree Protocol (STP), which is in IEEE

802. ID is defined, a loop-free network topology can be ensured by identifying multiple connections leading to loops and converting a network topology into a tree topology by deactivating selected redundant connections. If a connection or a network node fails, a network reconfiguration can be carried out by determining a new tree topology, taking into account failed connections or components. For this purpose, the network nodes exchange configuration messages with one another with topology information, which is also referred to as Bridge Protocol Data Units (BPDU). A further development of the Spanning Tree Protocol is the Rapid Spanning Tree Protocol (RSTP), which is defined in IEEE 802.1D-2004. While all connections in the STP are interrupted when a network component fails until a new tree topology is determined, only those connections fail in the RSTP that are directly affected by a failure.

According to the applicant's knowledge, in particular in the industrial sector, the networks have so far been specially designed for the respective requirement. Redundancy is ensured, for example, by lines connected to form rings in the field level.

In the event of high demands on reliability, two completely separate networks are set up, as provided for in the Parallel Redundancy Protocol (PRP, see for example IEC62439-3). In contrast to reconfiguration-based redundancy protocols such as RSTP or MRP, which always require a certain switchover time for a new configuration in the event of errors or failures in the network, PRP offers the advantage that continuous operation is guaranteed in the event of an error in one of the redundant networks can. According to the applicant's knowledge, the High availability Seamless Redundancy (HSR) protocol is preferred for ring topologies, which is standardized together with PRP in IEC62439-3: 2016.

Usually Ethernet is used so each that a _real-Z eitübertragung is possible through the different fieldbus systems. To enable redundancy, separate redundancy mechanisms were introduced, such as the High Speed Redundancy Protocol (HRP) for ring redundancy with switchover.

The applicant is aware that the ring topology is often built up in higher-level networks in industry. In meshed networks, usually only one way is activated, e.g. by RSTP to resolve loops.

Until now, real-time data could not be transmitted via routed paths, since PROFINET describes the communication via IP, but this has not been implemented by any manufacturer.

Furthermore, as far as the applicant is aware, it currently applies in principle that only one mechanism for redundancy is currently available for all applications in a network in the entire network. The mechanism used must be designed for the highest requirement, which means that even for applications with lower requirements, the redundancy mechanism required for the application with the highest requirements must always be used. This leads to a high resource requirement in the end devices and possibly unnecessarily occupies resources on the routes used.

At HSR, for example, the data for best effort communication is transferred to every link in the network. For example, IP applications often overlay TCP to compensate for the failure of a single link if packet loss is to be avoided. By expanding Ethernet in the AVB Task Group (see in particular IEEE 802.1), it is possible to protect a stream (periodic transmission of data frames) in a network and to guarantee transmission within a certain latency. A reservation protocol for automatic configuration was defined for this.

The reservation protocol checks all network resources required for data transmission, for example filter database entries (abbreviated FDB entries), queue memory, link bandwidth, in particular at the send port, and / or other resources at the participating network nodes on the transmission path and, if available, reserved.

Time Sensitive Networking (TSN) is a series of standards that extends the bridging standard IEEE 802. IQ to include mechanisms for the transmission of real-time-critical data over Ethernet networks. The standards mentioned include, for example, time synchronization (IEEE 802. lAS-Rev), frame preemption (IEEE 802.1Qbu) and reservation (IEEE 802.1Qca, IEEE 802.1Qcc) and other standards.

In particular, so that the behavior of a stream can be determined, shapers, such as the so-called credit-based shapers (abbreviated to CBS, see in particular IEEE 802.1Qav), were introduced. This ensures that there is a certain pause after each data frame when sending stream data. This enables the next network node, for example the next bridge on the transmission path, to ensure that there is no burst of stream data and that the incoming data amount corresponds to the reserved bandwidth.

A secure transmission with a known transmission time is ensured in particular by TSN and the introduced shapers and the associated preferred treatment of streams. Due to the further development of Ethernet in the IEEE, further mechanisms for forwarding are now available. To the knowledge of the applicant, however, it has so far been necessary to configure in advance which redundancy method is used in the network, and the hardware must be selected accordingly so that the application requirements are met. The applicant is aware that so far this has been based on the design of AVB for the home network area, where there is no physical redundancy, or a switchover takes place through RSTP and a brief failure of all communication is tolerated.

Based on this, the object of the present invention is to provide a method for data communication in a redundant operable, in particular industrial network, with which a high level of reliability is possible while at the same time particularly efficient use of available resources. In addition, it is an object of the invention to provide a device which is suitable for carrying out such a method.

The first-mentioned object is achieved by a method for data communication in a redundantly operable, in particular industrial network with a plurality of network nodes, where data is preferably transmitted in the context of and / or for an application between at least two communication partners, in particular in the form of terminal devices where there is a given requirement for the reliability of data transmission and two or more different redundancy modes are to be supported in the network,

in which

the redundancy modes supported in the network are each communicated to an associated virtual network in which the respective redundancy mode can be used, in particular to at least one of the at least two communication partners,

- from the redundancy modes, a suitable redundancy mode is automatically selected in the light of the given requirements for the reliability, and - Preferably data between the at least two communication partners are transmitted via the virtual network belonging to the automatically selected redundancy mode.

In other words, the basic idea of the present invention is to support a number of different redundancy modes in a particularly industrial network, and to communicate these along with associated virtual networks in which they can be used, preferably at least one of the communication partners involved.

Each redundancy mode is preferably assigned at least one, in particular exactly one virtual network, in particular base VLAN or at least one, in particular exactly one base VID.

The different virtual networks belonging to the respective redundancy mode are preferably base VLANs (English: Base VLANs), in particular in the sense of IEEE 808. IQ, or the different virtual networks belonging to the respective redundancy mode preferably each represented and / or identifiable and / or defined by a base VLAN (base VLAN) and / or base VID (base VID).

From the redundancy modes communicated according to the invention, a mode which is suitable in the light of the specified requirement of the respective application is selected automatically and the data is expediently transferred between the communication partners involved via the at least one virtual network belonging to the selected mode, in particular a special VLAN or base VID basis.

The redundancy modes and associated virtual networks, in particular base VLANs or base VIDs, can be communicated, for example, by sending messages with the corresponding content. It should be noted that even a mode in which no failure safety is offered represents a redundancy mode in the sense of the present application, in particular a redundancy mode with zero redundancy or a mode that does not offer redundancy. A network that supports, for example, a mode or in which a mode is provided or implemented in which redundancy is guaranteed, and a mode in which no redundancy is guaranteed represents a network in which two redundancy modes are supported or are provided or implemented.

The procedure according to the invention makes it possible for an application or, in the event that several applications want to use a network, to communicate each application its request for communication. The existing redundancy capabilities can be described by the network itself. Mapping can then be used to select a redundancy mode that is sufficient for the respective application. As a result, only the mechanism that is really needed by the application can be used. This saves resources in the network. In particular, either the use of a weaker network to meet all requirements is possible, or the use of other applications in the same network, since resources are still available.

Another advantage of the invention is that the operation of application (s) and network is decoupled. The network can be upgraded and changed regardless of the application or applications. If the application (s) has changed requirements, they can also be set independently of the network. During commissioning, in particular when setting up streams for real-time, secure data transmission, the newly introduced description of the network capabilities is then used to map the redundancy mechanisms or modes provided by the network. The data that are to be transmitted between the communication partners involved, which are preferably given by terminal devices, are preferably sensor data and / or control values for one or more actuators of one of these that are detected by an automation system. The communication partners can be, for example, one or more in particular programmable logic controllers and / or IO devices or the like.

End devices are to be understood in particular in a manner known per se to be devices which represent an initial source and / or a final destination of data, in particular data frames, in a network, which are transmitted or are to be transmitted in the network. They are preferably end stations in the sense of IEEE802.1Q.

The procedure according to the invention is particularly advantageous in the event that several applications want or need to use a (physical) network.

Accordingly, a further preferred embodiment of the method according to the invention is characterized in that

- For several applications and / or in the context of several applications, data are to be transmitted between at least two communication partners belonging to the respective application, wherein there is a predetermined requirement for the reliability of the data transmission for each application, and

- For each application, a redundancy mode is automatically selected from the supported redundancy modes in the light of the requirement for failure safety that belongs to the respective application.

Data is then preferred between the communication partners belonging to each application via the transmit selected virtual network for the selected redundancy mode.

Furthermore, it can be provided that different redundancy modes are automatically selected and used for different applications in the network.

The redundancy modes supported in the network, in addition to the associated virtual networks, are preferably communicated to at least one of the communication partners of the respective application. The message is particularly preferably sent to one or the communication partner (talker) representing the transmitter and / or to one or the communication partner representing the transmitter.

At least one redundancy mode is preferably assigned a specific redundancy mechanism or a specific redundancy method, or at least one redundancy mode includes one or such. In particular, several redundancy modes are each assigned to the redundancy mechanism or redundancy method. Purely by way of example for redundancy mechanisms or redundancy methods, end-to-end, switchover, ie switching, and / or segment protection redundancy mechanisms or methods are mentioned.

It can also be provided that at least one redundancy mode is not assigned a redundancy mechanism or method, or at least one redundancy mode is not or does not include such, which then in particular represents at least one redundancy mode with zero redundancy or without redundancy.

It may be that one or more redundancy modes are given or defined by a specific redundancy method or a specific redundancy mechanism or the lack thereof. However, it is also possible that one or more redundancy modes in addition to a redundancy method or mechanism, such as switchover, end-to-end or segment protection, or the lack of such, include additional functions and / or aspects.

Examples of additional functions are an auto repair function and / or the need for registration of MAC addresses and / or support for frame replication and elimination by at least some network nodes, in particular in accordance with IEE802.1CB.

For example, a first redundancy mode supported in a network can be characterized in that a switchover redundancy method is or can be used in it and an auto-repair function takes effect, in particular in the event of a fault or defect in a network node, and that it is necessary to register MAC addresses. A second redundancy mode can, for example, be characterized in that an end-to-end

Redundancy method or mechanism is or can be used, and an auto repair function takes effect, but it is not necessary to register MAC addresses. Further redundancy modes can be distinguished by further combinations of redundancy processes and any additional functions, or also by the fact that they do not include a redundancy method, but other functions.

A network in which the method according to the invention is carried out is preferably an Ethernet-based or Ethernet-capable network, preferably in the sense of IEEE802.3.

It should be noted that a network is to be understood as a physical network without further designation. One or more virtual networks can be set up in a physical network in a well known manner.

With Ethernet in particular, the distinction between several virtual networks in a physical network is usually usually by IDs belonging to the respective virtual network, in particular VLAN IDs, which are also referred to as VIDs for short.

The virtual networks in which the respective redundancy mode can be used are preferably so-called basic virtual networks or base VLANs or base VIDs, in particular in the sense of IEEE802.1Q, each of which has one or more IDs (see ), in particular VID (s).

Appropriately, at least one, preferably exactly one virtual (base) network is administratively available for each supported redundancy mode. If the virtual network belonging to the respective base VLAN is used for data transmission, the forwarding mechanism belonging to the respective basic VLAN automatically takes effect, preferably according to IEEE802.1Q, and the associated redundancy mode or this (if applicable ) associated redundancy mechanism or the redundancy procedure associated with this (if applicable). According to

According to IEEE802.1Q, each VID is assigned exactly one base VID, which defines the forwarding mechanism. In the IEEE 802.1 Q standard, these are in particular STP, RSTP, MSTP and the forwarding developments Shortest Path Bridging (SPB). Each virtual network is assigned an associated forwarding mechanism via the associated base VLAN, which serves as the basis for a redundancy mode.

In particular, the associated redundancy mode is configured in the respective virtual network.

In a particularly preferred embodiment, the supported redundancy modes and associated virtual networks are transmitted in the form of network availability vectors. The supported redundancy modes and associated virtual networks in the form of network availability vectors are preferably transmitted to at least one of the at least one two communication partners belonging to the respective application.

The network availability vectors can also be referred to as network availability vector and abbreviated to NAV. The network availability vectors (NAVs) are preferably bit vectors which are given in a manner known per se by a sequence of bits with assigned meaning.

It can be provided that the NAVs for all available redundancy modes are sent in a packet in succession as TLV (Type Length Value). Of course, it is also possible that a packet is sent for each NAV or only a few NAVs are combined in one packet.

If the capabilities of the network are described in one or more network availability vectors (NAVs), it is further preferably provided that each network availability vector specifies at least one redundancy mechanism or redundancy method or indicates that such is missing , in particular in the form of a bit value representing the mechanism or the method or the lack of such a bit value, and preferably an indication of whether or not an auto repair function is activated in the event of a failure, in particular of a network node, and / or whether a registration of MAC address is necessary or not.

As a purely exemplary example, it should be mentioned for a bit sequence that, for example, a bit of a corresponding vector indicates whether or not a registration of a MAC address is necessary, for example two bits following it can represent a total of four different redundancy mechanisms or redundancy methods, and one thereon The following bit indicates whether an auto repair function is activated or deactivated. For example, a 0 bit can indicate that no such function is supported or one is deactivated, and a 1-bit to indicate the existence or being activated of such a function. The same applies to the need to register MAC addresses.

It can also be provided that it is stated whether at least some of the network nodes support frame replication and elimination, in particular in accordance with IEEE802.1CB. A corresponding notification or notices are preferably sent to at least one of the at least two communication partners of the or each application.

Then it can further be provided that the network availability vectors include the information as to whether at least some of the network nodes support frame replication and elimination or not. For example, at least one further bit field can be provided in the vector or vectors, for example in front of the bit field for the need to register MAC addresses. A bit of 0 or 1 can then be used to indicate whether frame replication and elimination (abbreviated FRER for Frame Replication and Elimination for Reliability. See in particular IEEE802.1 CB) is not supported or possible, or is it the case .

In a further advantageous embodiment, it can be provided that at least one of the two communication partners of the or each application is informed whether at least one of the at least two communication partners of the or the respective application is performing frame replication and elimination, in particular in accordance with

IEEE802.1CB supported. Particularly preferably, at least one sending communication partner who wants to send data to at least one receiving communication partner is informed whether the at least one receiving communication partner supports frame replication and elimination or not. If frame replication and elimination is supported by the recipient, that is to say the data sink or the destination, this is not necessary by the network nodes via which the frames are forwarded to the recipient. This is particularly due to the fact that the elimination or the filtering out or also the discarding of duplicate frames based on redundancy can then be carried out directly at or by the recipient. If this function is not supported by a receiver, the last network node in front of the receiver, which can also be referred to as a receiving node on the receiving side, has to eliminate replicated or duplicated frames for redundancy reasons in order to avoid problems.

It should be noted that, in particular in the context of AVB and TSN, transmitters are also referred to as talkers and receivers as listeners.

In a further development of the method according to the invention, it can further be provided that the virtual networks belonging to the supported redundancy modes preferably together with one or more IDs, in particular VIDs, preferably at least one of the at least two communication partners of or depending on the application as type-length values, in particular Configuration type length values are transmitted.

This form has proven to be particularly suitable. The transmission is preferably carried out together with the information about the redundancy mode belonging to the respective virtual network, in particular Base VLAN. It has proven to be particularly advantageous if the associated virtual network, in particular Base VLAN, in which the mode can be used, preferably together with the one or more belonging to the virtual network, if a bit vector with information about an available redundancy mode IDs, in particular VID (s), are transmitted via or in a TLV following the bit vector in particular. A bit vector with the specification of a redundancy mode with a TLV after it with the information about an associated virtual network, in particular Base VLAN along with IDs or IDs belonging to it, can be transmitted, for example, as part of an LLDP message or form one .

Furthermore, preferably together with the virtual networks belonging to the various redundancy modes, IDs belonging to the virtual networks, in particular VLAN IDs or VIDs, are communicated.

It should be noted that a virtual network, in particular base VLAN or base VLAN, can either include only one ID, in particular VLAN ID or VID, or can also include several IDs, in particular VLAN IDs or VIDs. If several IDs belong to a virtual network, these are expediently all communicated either together with the corresponding redundancy mode and the virtual network, or this information is obtained in another way, for example from a central configurator or the like. According to IEEE 802.1 Q, each VID is clearly assigned a base VLAN. The configuration of the assignment can follow, for example, the standardized management objects. A number of IDs will be present in particular if, for a redundancy mode, a number of paths, in particular disjoint paths, at least in sections, are preferably used simultaneously for the forwarding of data frames. Then, each path has its own VID, which in particular can be used to control or control forwarding.

It has proven to be particularly suitable that the redundancy modes supported in the network and in particular the associated virtual networks are communicated by at least one preferably all network node, in particular via a protocol which is suitable for exchanging messages between adjacent network devices. The link layer discovery protocol (LLDP), in particular in accordance with IEEE802.1AB, can be used as a protocol and / or for example Reservation protocol, preferably the Stream Reservation Protocol (SRP), in particular according to IEEE 802.1 Q, and / or MSRP or the like.

Furthermore, it can be provided that at least one, in particular all network nodes periodically send messages with which at least one, preferably exactly one of the supported redundancy modes is communicated together with the associated virtual network. Corresponding information transfer can in turn take place in the form of network availability vectors, which can be part of messages that are sent in the context of appropriate protocols or also represent own messages.

It should be noted that it is also not excluded that the communication partners, in particular terminals, receive the information about available redundancy modes and associated virtual networks from a location other than one or more network nodes. This can also come from a central configurator, for example.

Accordingly, a further embodiment is characterized in that the redundancy modes supported in the network and in particular the associated virtual networks are particularly preferably communicated directly to at least one of the at least two communication partners of the or the respective application by a preferably central configuration unit.

In addition, it can be provided that the automatic selection of a suitable redundancy mode for the or each application from the supported redundancy modes includes or is carried out by a mapping, which has proven to be a particularly suitable option.

Redundancy in a network, i.e. network redundancy, means in particular that alternative or additional devices or paths within the network infrastructure are available that can be used in the event of a failure or error or unavailability to continue to ensure data transmission. The fact that a redundancy mode or redundancy method or mechanism is supported means, for example, that in the event of a failure or error or the unavailability of one or more network devices or paths in particular, an automatic change to one or more other devices or Paths done.

As an alternative to a change in response to a failure or error or the unavailability of one or more network devices (nodes) or paths, in particular according to IEEE 802.1 CB, several paths can also be used in parallel and at network nodes that lie on several paths, each depending because incoming first duplicates are discarded.

The various redundancy mechanisms or methods supported in accordance with the invention in a network, of which at least one redundancy mode is preferably assigned to one, can in principle be any method known from the prior art. Switchover redundancy mechanisms such as the Rapid Spanning Tree Protocol (RSTP) and / or the Multiple Spanning Tree Protocol (MSTP, see in particular IEEE802.1Q) and / or ring MRP (MRP for media redundancy protocol) are examples in this context stands, see in particular IEC62439) and / or the shortest path. Of course, alternatively or additionally, a bumpless mechanism, an end-to-end redundancy mechanism between transmitter and receiver or several end-to-end redundancy mechanisms in the network between network components can be supported. As another example of alternatively or additionally possible redundancy mechanisms, frame replication and elimination redundancy mechanisms may be mentioned, which preferably comprise segment protection. In connection with frame replication and elimination, reference is made in particular to frame replication and elimination for reliability (FRER) according to IEEE802.1CB.

Redundancy modes comprising two or more different redundancy mechanisms are preferably supported or implemented and can be used via the associated virtual network, so that there is a high degree of flexibility.

The method according to the invention has proven to be particularly advantageous in the field of real-time data communication, particularly in industrial networks. A further advantageous embodiment is accordingly characterized in that a protected connection is set up for the data transmission between the or the respective at least two communication partners of the or each application, for which network resources are preferably reserved at participating network nodes. The data transmission is then preferably carried out via the or the respective protected connection, in particular in the form of a stream and / or using reserved resources.

In particular, so that 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, in particular support or support the establishment of protected connections reserved network resources at the participating network nodes. This is well known from the prior art.

If the data are to be transmitted as streams (in particular periodic transmission of data frames or packets) and / or using reserved resources, the newly added description of the network redundancy functions, in particular the network availability vectors, is preferably used during the setup of the stream (s) mapping to the mechanisms provided by the network. Based on the requirements of the application for the availability / reliability of the data transmission, a corresponding available redundancy mechanism in the form of a redundancy mode - possibly with additional functions - can be selected that fulfills the requirements (possibly as well as possible). The base VLAN to be used and thus the VID or the VIDs to be used result from the selection of the redundancy mode.

Another object of the invention is a communication device. This is designed and / or set up to carry out a method accordingly to the preceding description.

The device according to the invention is preferably designed and / or set up to support a plurality of network redundancy modes and / or to periodically send out messages with which the supported redundancy modes are each known with an associated virtual network in which the respective redundancy mode can be used can be made or made known. Such a communication device is preferably a network infrastructure device, for example in the form of a bridge or a switch. It has proven to be particularly expedient if a protocol is supported for the announcement which is suitable for exchanging messages between neighboring network devices, particularly preferably the Link Layer Discovery Protocol, in particular in accordance with IEEE802.1AB.

Alternatively or additionally, the device according to the invention can be designed and / or set up to receive information about the redundancy modes supported in the network in each case with an associated virtual network, in which the respective redundancy mode can be used, and for at least one application, within the scope of which and / or for the data to be sent and / or received by the device, a predetermined requirement for the reliability to determine the data transmission, and to automatically select a redundancy mode suitable from the redundancy modes in the light of the specified requirements for fail-safety. Such a communication device is in particular a terminal device, which represents an original source and or a final destination of data.

The invention also relates to an industrial network, in particular, which comprises one or more communication devices according to the invention.

The invention further relates to a computer program which comprises program code means for carrying out the steps of the method for data communication according to the invention.

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

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 only be understood as a physical medium, but also, for example, in the form of a data stream and / or a signal which represents a data stream.

Further features and advantages of the present invention who the reference to the following description of embodiments according to the invention with reference to the accompanying drawing clearly. In it

Figure 1 is a purely schematic partial representation of an industrial, Ethernet-based network with several network nodes; FIG. 2 shows a table with the possible combinations that result from the redundancy mechanisms supported in the network, the CB (FRER) support on the part of the network nodes, the auto repair function and the CB (FRER) support on the part of the end devices;

FIG. 3 shows a purely schematic representation of a NAV and a bit for FRER support on the part of the end devices, which together form an Availability Selector (AS);

FIG. 4 shows a purely schematic representation of a configuration TLV with the base VLANs belonging to the redundancy mechanisms and VIDs belonging to them;

FIG. 5 shows the partial representation according to FIG. 1 for the case in which FRER with segment protection is selected as the redundancy mode; and

FIG. 6 shows the partial representation according to FIG. 1 in the event that an end-to-end redundancy mode is selected.

FIG. 1 shows a purely schematic partial illustration of an industrial Ethernet-based network with several network nodes 1, which are given in the form of bridges in the exemplary embodiment shown. In addition to a total of ten network nodes 1, two communication partners can be recognized in the form of end devices, of which one communication partner 2 would like to send data to another communication partner 3. Correspondingly, the communication partner 2 represents a transmitter and is also referred to here as a talker.

The communication partner 3, which should be the recipient of the data sent, is referred to below as the listener.

It should be noted that the network, which is only shown in part, can comprise or comprise a large number of further network nodes 1, and further communication partners can participate or participate in the network. In the exemplary embodiment described here, the talker 2 would like to periodically send data frames in real time with guaranteed quality of service, in particular guaranteed maximum latency, to the listener 3 in the context of or for a control application for an industrial process (not shown). Accordingly, a TSN stream should be set up between Talker 2 and Listener 3. For this, a stream announcement with a stream description, in particular a talker advert, is sent by the talker 2 in a well-known manner and forwarded via the network node 1 to the listener 3, who can log on to the stream, whereby for the secure transmission supply at the participating network nodes 1 network resources, e.g. bandwidth and / or filter database entries and / or queue memory, if they are available. The establishment of streams and associated reservation using a reservation protocol is well known from the prior art and is not explained in more detail here. In this context, purely by way of example, reference should be made to the standards IEE802.1Q, IEE802.1AS, IEE802.1BA and IEE802.1CB.

In particular, since the useful data contained in the data frames are required for real-time control, considerable problems would be associated with a failure of the data transmission. Therefore, the application has a predetermined, high requirement for the reliability of the data transmission.

As can be seen, the talker 2 and the listener 3 are connected to one another via two coupled ring segments SI and SII and there are at least partially disjoint paths de PI and P2 via which the talker 2 and the listener 3 are connected and communicate with one another can. Since at least two redundant paths are available, reliability / redundancy can be guaranteed. The cloud 4 in FIG. 1 indicates the redundant path domain. The network supports various redundancy modes Ml-Mn (see Figure 3). Each redundancy mode Ml-Mn includes a specific redundancy mechanism / a specific redundancy method and optionally further functions, in this case specifically whether the network node 1 and thus also the edge port at which the listener 3 is present at the next network node 1, frame replication and Elimination support or this function is activated and / or available or not, the need to register the MAC addresses and an auto repair function. The table according to FIG. 2 shows various possible combinations of redundancy mechanisms and the optional additional functions auto repair and FRER support through edge ports. The abbreviation ES stands for end station, that is to say end device (talker 2 and listener 3), the abbreviation EP for edge port, specifically relates to the edge port of the network node 1 at which the talker 2 or listener 3 is located on the transmitter or receiver side gen edge network node 1 is present. The abbreviation NW for network, the abbreviation AP for auto repair and FRER for frame replication and elimination for reliability. The "!" before the respective abbreviation indicates that the corresponding function is not available or is activated.

The available redundancy mechanisms are abbreviated in the table with SWO, E2E, and SP. N stands for "None", i.e. no redundancy or with a redundancy of "zero", SWO for switch chover, i.e. for a switchover redundancy mechanism, as can be provided by RSTP, MSTP or SP, E2E for End-2 -End, i.e. end-to-end redundancy, and SP for segment protection, i.e. segment protection, especially FRER with segment protection. The table does not take into account whether or not it is necessary to register MAC addresses.

The different redundancy modes Ml-Mn with the associated redundancy mechanisms or methods can be used in different basic virtual networks (Base VLANs) that are administratively available in the network. these can simply called Base VLAN1, Base VLAN2, ..., Base VLANn.

An embodiment of the method according to the invention is carried out in order to enable a high level of reliability with optimal use of available resources, in particular also in the case of using the network by several applications.

In the context of the exemplary embodiment shown, in a first step the redundancy modes Ml-Mn supported in the network with the respectively associated virtual network, specifically the assigned base VLANs in which the respective redundancy mode Ml-Mn can be used, are the talker 2 communicated.

Specifically, all network nodes 1 periodically send LLDP messages (LLDP stands for the well-known Link Layer Discovery Protocol) with which end devices are informed about the network availability options. The talker 2 receives corresponding messages from the network node 1 which is closest to it and which can also be referred to as a transmitter-side edge node.

The network availability options, in particular the supported redundancy modes Ml-Mn, are transmitted in the form of network availability vectors NAV, which are given by bit vectors.

FIG. 3 shows, purely schematically, an example of a NAV which represents a redundancy mode Ml-Mn. The NAV comprises five consecutive bits 5-9, the first bit 5 indicating whether the network node 1 and thus also the edge port at which the listener 3 is connected to the next network node 1 support frame replication and elimination FRER or this function is activated and / or available or not (in the figure it is indicated with "EP" that the information relates to the "edge port", that is to say edge port), the second bit 6 indicates whether a registration of the MAC addresses is necessary or not, the third and fourth bits 7, 8 an available one

Specify the redundancy mode RM, and the fifth and last bit 9, whether an auto repair function AR is activated or not. For the designations in bold in FIG. 3, which can be 0 or 1 as usual, it is always the case that 0 indicates that the function is not activated and 1 that this is the case.

With the third and fourth bits 7, 8 for the redundancy mechanism RM, the absence of a redundancy mechanism with N or one of the three redundancy mechanisms mentioned, i.e. switchover SWO, end-to-end E2E and segment-protected SP, is indicated in each case by the bit sequence 00 , 01 10 and 11 in that order.

It should be noted that the availability in network 1 can be communicated or defined via bits 6-9, which is abbreviated to ViN in FIG. 3.

The availability of a redundancy mode Ml-Mn can accordingly be communicated in or with a NAV. In order to communicate the overall available redundancy modes Ml-Mn, several NAVs are sent in succession in one packet as a TLV. Of course, it is also possible for each NAV to be sent in its own packet.

It should be noted that, according to the table in FIG. 2, there are a total of 32 possible combinations from none or one of the four redundancy mechanisms SWO, E2E, SP, the auto repair function that may be present, and the necessary registration of MAC addresses and the existing FRER support, if any. If all of these combinations are (should) be supported in a network, which is possible but not absolutely necessary, 32 NAVs with a corresponding Base VLAN would be communicated. It is also communicated, in the present case via a further bit 10, whether locally (indicated in FIG. 3 with "L") on the part of a terminal or the terminals, specifically the listener 3, frame replication and elimination FRER (in particular CB according to

IEE802.1CB) is supported or not. This message is not sent by the network nodes 1 to the end devices, such as the NAVs, but this information is provided locally by the listener 3 or talker 2 and evaluated locally. It also applies here that 0 indicates that this is not supported and 1 that there is support.

A NAV together with bit 6 with the information about the terminal-side FRER support is also referred to in the present case as the availability selector or availability selector AS. The Availability Selector AS thus results from the capabilities of the network together with the support of CB / FRER according to IEE802.1CB in the end device, specifically the list ner 3 or talker 2.

Each base VLAN, in which a certain redundancy mode Ml-Mn can be used, comprises one or more VIDs which are to be used for data transmission, in particular the forwarding of data frames from the talker 2 to the listener 3 . are. The network describes what VIDs belong to which base VLAN. Specifically, corresponding configuration TLVs (TLV stands for Type Length Value in a well-known manner) are transmitted. FIG. 4 shows the structure of a configuration TLV in a purely schematic manner, in which a base VLAN (abbreviated in the figure with B VLAN) is contained with the associated VID (s). In the context of the exemplary embodiment described here, the TLVs with the base VLANs and associated or associated VIDs are each periodically sent together with the NAVs (see FIG. 4) by the network node 1, that is to say also via the LLDP messages. In each case, a NAV is followed by a TLV with the associated Base VLAN and the VDI (s) of the Base VLAN. Of the NAV therefore precedes the TLV like a header. This is to be understood as playful and therefore not restrictive.

From the redundancy modes Ml-Mn communicated via the LLDP messages, a redundancy mode Ml-Mn that is suitable in the light of the requirements for fail-safety specified by the application is automatically selected and data frames are then automatically selected between the two communication partners 2, 3 Redundancy mode Ml-Mn associated virtual network transmitted. The selection is made by mapping the requirement or requirements of the application and the notified network availability, together with the local capabilities of the terminal device 2, 3 itself.

In the example described here, a redundancy mode with SP, in the present case FRER with segment protection, is selected as the redundancy mechanism for the real-time transmission of the control data. This particularly robust mechanism is chosen because the Talker 2 and Listener 3 are comparatively far from each other, for example at different ends of a larger system.

The base VLAN belonging to this mode and communicated to the talker 2 together with the NAV belonging to the mode, or the associated VID or the associated VIDS, are then assigned by the talker 2 when the stream is set up for the real-time transmission of the control data the listener 3 used. The VID, which belongs to the automatically selected redundancy mode Ml-Mn, is contained in the Talker Advertise and the Listener Join. If several VIDs are included, i.e. several paths have to be set up, a talker advertise and listener join is carried out for each path and thus each VID, which then contain one of the VIDs.

In FIGS. 5 and 6, the situation resulting for two different redundancy mechanisms for the constellation according to FIG. 1 - purely by way of example and schematically - is illustrated. FIG. 5 shows the situation for the use of frame replication and elimination for redundancy (FRER) and segment protection, that is to say for the redundancy mode selected by the control application (the situation after the stream setup and activation of the is shown Forwarding).

The transmitted data frames are transmitted from the talker 2 to the first network node 1 using a first VID0. This is indicated by an arrow with a solid line. It should be noted that in the purely schematic FIG. 5 the data frames are not shown, but only arrows which represent their transmission path.

The incoming data frames are duplicated from the network node 1 closest to the talker 2 and the one frame is forwarded in each case via the lower path PI and the second frame in each case via the upper path P2, the VIDs VIDI and VID2 being used. Data transmission using VIDI is indicated by arrows with dash-dotted lines, that of VID2 by arrows with dashed lines. The network node 1 is designed and / or set up to carry out the duplication.

A stream merge function with duplicate elimination takes place at the four network nodes 1 which connect the two segments SI and SII to one another and at the network node 1 closest to the listener 3, that is to say the receiver-side edge node 1. The first incoming duplicate is duplicated for each further path and forwarded with the required VID of the respective path on the path or paths, and all further incoming duplicates are discarded. The corresponding places are marked with a circle symbol, which is provided with the reference number 11.

If a network node 1 fails on path PI or path P2, the other path PI, P2 can be used, where occur nits _Z at any Shift. In the event of an error, only a duplicate arrives at the locations provided with the reference number 11, which is treated as the first incoming duplicate and is accordingly itself duplicated again for each further path and provided with the corresponding VID of the path. Since no further duplicates arrive due to the error, they do not have to be discarded.

If another application would like to transmit data from the talker 2 to the listener 3, its specified requirement for failure safety is considered and a suitable redundancy mode is also automatically selected for this, and data are transmitted using the virtual network associated with the redundancy mode, in particular base VLAN.

Purely by way of example, it should be mentioned that data is to be transmitted from the talker 2 to the list tener 3 as part of one or for a further control application, the talker 2 and listener 3 not being far apart, and a redundancy mechanism that is less robust compared to SP being sufficient. Then, for example, a mode can be selected which includes end-to-end redundancy E2E.

The situation resulting in such a case for the data transmission is shown in FIG. 6 (situation after the stream setup and activation of the forwarding).

Talker 2 then duplicates each of the data frames to be sent periodically via the stream. One frame is forwarded to path ner 3 via path PI, that is to say in FIG. 6 below, using the VIDI of the base VLAN for end-to-end redundancy E2E. This is indicated in FIG. 6 by dash-dotted arrows pointing from the talker 2 to the listener 3. According to this mechanism, two frames leave the talker 2 and two frames arrive at the listener 3, which is indicated by the two arrows between the Talker 2 and the first network node 1 and the last network node 1 and the listener is indicated.

The respective second data frame is sent periodically to the listener 3 via the path P2, that is to say in FIG. 6 above, using the VID2 of the base VAN for the end-to-end redundancy E2E (indicated by arrows with a broken line).

If a network node 1 fails on path PI or path P2, the other path PI, P2 can be used in each case. Since the transmission is interrupted in the event of an error due to the failure of network node 1, the duplicated frames in network node 1 are discarded on network node 1 that preceded the path.

A video transmission application for which image data are to be transmitted from the talker 2 to the listener 3 may be mentioned as an example of an application in the light of which a switchover redundancy mechanism SWO would be suitable in terms of the reliability. Since a short failure of the video sequence or a jerk can be accepted, a switchover time can be accepted and switchover can be used. Then a virtual network belonging to a mode with switchover redundancy SWO is used. The associated base VLAN and the associated VIDs have been communicated to the talker via the LLDP message with the corresponding NAV and TLV.

For example, an application in which data that are sent from the talker 2 to the list ner 3 can subsequently be evaluated completely without a security mechanism against failure, that is to say without a redundancy mechanism. If "N" N can be selected for the redundancy mode, a virtual network, in particular Base VLAN, is used for the data transmission, which belongs to a mode without a redundancy mechanism. The base VLAN and the associated VID (since there are no additional, redundant paths, it is in this one If there is only one VID), the talker has also been informed of an associated LLDP message with NAV and TLV.

Even if the application examples for a transmission of data frames from the talker 2 to the listener 3 have been described above, it goes without saying that the processes are the same if data are to be transmitted between other communication partners and / or between more than two com communication partners.

Furthermore, it should be noted that both the network nodes 1 read and the terminals 2, 3 represent exemplary embodiments of communication devices according to the invention. They are designed and / or set up to carry out the described exemplary embodiment of the method according to the invention.

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

Claims

1. A method for data communication in a redundant be operable, in particular industrial network with several network nodes (1), wherein between at least two communication partners (2, 3), in particular in the form of terminals, data preferably in the context of and / or for an application are to be transmitted, there being a predetermined requirement for the reliability of the data transmission, and two or more different redundancy modes (Ml-Mn) are supported in the network,

in which

- The redundancy modes supported in the network (Ml-Mn) each with an associated virtual network (B

VLAN) in which the respective redundancy mode (Ml-Mn) can be used, in particular at least one of the at least two communication partners (2, 3) is communicated,

- from the redundancy modes (Ml-Mn), a suitable redundancy mode (Ml-Mn) is automatically selected in the light of the specified requirements for reliability, and

- Preferably, data between the at least two communication partners (2, 3) are transmitted via the virtual network (B VLAN) belonging to the automatically selected redundancy mode (Ml-Mn).

2. The method according to claim 1,

characterized in that

- for several applications and / or in the context of several applications, data are to be transmitted between at least two communication partners (2, 3) belonging to the respective application,

- For each application, there is a specified requirement for the reliability of the data transmission, and for each application from the supported redundancy modes (Ml-Mn) an automatically selected redundancy mode (Ml-Mn) is selected in the light of the requirement for the reliability that belongs to the respective application will, and

- Preferably, data is transmitted between the communication partners (2, 3) belonging to each application via the virtual network (B VLAN) belonging to the respectively selected redundancy mode (Ml-Mn).

3. The method according to claim 2,

characterized in that

Different redundancy modes (Ml-Mn) can be automatically selected and used for different applications in the network.

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

at least one redundancy mode (Ml-Mn) a specific redundancy mechanism (SWO, E2E, SP) and preferably additional functions, in particular an auto repair function and / or the need to register MAC addresses and / or support frame replication and Eli Mining by at least some network nodes, in particular according to IEE802.1CB, and / or at least one redundancy mode does not include a redundancy mechanism (N) and preferably additional functions, in particular an auto repair function (AR) and / or the need for a registration of MAC Addresses (MA) and / or support for frame replication and elimination by at least some network nodes (FRER), in particular in accordance with IEE802.1CB.

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

characterized in that

In particular, at least one of the at least two communication partners (2, 3) of the or each application, the supported redundancy modes (Ml-Mn) are transmitted in the form of network availability vectors (NAV), preferably for each available redundancy mode (Ml- Mn) at least one network availability vector (NAV) is transmitted, and / or wherein each network availability vector (NAV) the specification of a redundancy mechanism (SWO, E2E, SP) or an indication that one is missing, in particular in the form of a bit value (7, 8) representing the mechanism or the absence of such a value and preferably an indication of whether or not an auto-repair function is activated in the event of a failure, in particular of a network node (1), and / or whether registration of MAC addresses is necessary or not included.

6. The method according to any one of the preceding claims,

characterized in that

in particular at least one of the at least two communication partners (2, 3) who or each application is informed whether at least some of the network nodes (1) have frame replication and elimination (FRER), in particular in accordance with

IEE802.1CB, support.

7. The method according to claim 5 and 6,

characterized in that

the network availability vectors (NAV) comprise the information as to whether at least some of the network nodes (1) have frame replication and elimination, in particular in accordance with

Support IEE802.1CB or not.

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

at least one of the at least two communication partners (2, 3) of the or each application is informed whether at least one further of the at least two communication partners (2, 3) of the or the respective application is performing frame replication and elimination (FRER), in particular in accordance with IEE802 .1CB supported.

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

the virtual networks (B VLAN) belonging to the supported redundancy modes (Ml-Mn), in particular at least one of the at least two communication partners (2, 3) of the or each application as type-length values, in particular configurations-type-length values Values are transmitted.

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

together with the virtual networks (B VLAN) belonging to the different redundancy modes (Ml-Mn), IDs belonging to the virtual networks (B VLAN), in particular VIDs, are communicated.

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

the redundancy modes (Ml-Mn) supported in the network and in particular the associated virtual networks (B VLAN) are communicated by at least one, preferably all, network nodes (1), in particular using a protocol which is suitable for sending messages between neighboring network devices ( 1) to exchange, particularly preferably via the Link Layer Discovery Protocol, in particular according to IEEE802.1AB, and / or via a stream reservation protocol, preferably according to IEEE 802.1 Q, in particular via SRP.

12. The method according to claim 11,

characterized in that

at least one preferably periodically sends out all network nodes (1) with which at least one, preferably exactly one of the supported redundancy modes (Ml-Mn) is communicated together with the associated virtual network (B VLAN).

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

the redundancy modes (M2-Mn) supported in the network and in particular the associated virtual networks (B VLAN) are preferably communicated directly by a preferably central configuration unit, preferably at least one of the at least two communication partners (2, 3) to the respective application.

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

the automatic selection of a suitable redundancy mode (Ml-Mn) for the or each application from the supported redundancy modes (Ml-Mn) includes mapping or is carried out by such.

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

at least one redundancy mode (Ml-Mn) at least one switchover redundancy mechanism (SWO), in particular RSTP and / or MSTP and / or ring MRP and / or shortest path, or at least one end-to-end redundancy mechanism (E2E) or at least includes a frame replication and elimination redundancy mechanism (FRER), in particular with segment protection (SP).

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

a protected connection is set up for the data transmission between the or the respective we at least two communication partners (2, 3) of the or each application, for which network resources are preferably reserved at participating network nodes (1), and the data transmission via the or the respective protected Connection in particular in the form of a stream and / or using reserved resources.

17. Communication device (1, 2, 3) for performing the method according to one of the preceding claims.

18. Device (1) according to claim 17,

characterized in that

the device (1) is designed and / or set up to support several network redundancy modes (Ml-Mn) and preferably periodically send out messages with which the supported redundancy modes (Ml-Mn)) each have an associated virtual network (B VLAN) in which the respective redundancy mode (Ml-Mn) can be used, can be made known or can be made known.

19. Device (2, 3) according to claim 17 or 18,

characterized in that

the device (2, 3) is designed and / or set up to provide information about the redundancy mo di (Ml-Mn) supported in the network, in each case with an associated virtual network (B VLAN) in which the respective redundancy mode can be used receive,

for at least one request, within the scope of which and / or for the data to be sent and / or received from the device (2, 3), to determine a predetermined request for the reliability of the data transmission, and

from the redundancy modes (Ml-Mn) automatically select a redundancy mode (Ml-Mn) that is suitable in the light of the specified requirements for reliability.

20. Computer program comprising program code means for performing the method according to one of claims 1 to 16.

21. A computer readable medium comprising instructions which, when executed on at least one computer, cause the at least one computer to carry out the steps of the method according to one of claims 1 to 16.