Method for the redundant transmission of messages within a communication system having a multi-ring topology, and communication system

Abstract

The invention relates to a method for the redundant transmission of messages within a communication system having a multi-ring topology, in which the messages are transmitted between communication devices (101-102, 111-112, 121-123, 131-134) that are each connected to one another in a ring topology. A respective selected communication device (111, 123, 133) within a fault-free ring blocks one of its ports, by means of which it is connected to the ring, so as to prevent forwarding of messages containing payload data. The communication devices each comprise at least two ports connected to a ring, and transmit messages originating from each of them into the respective ring via both ports. Communication devices (101-102) that are connected to multiple rings operate their ports (A1-A2, A3-A4, A5-A6, B1-B2, B3-B4, B5-B6) assigned to the respective ring in isolation from all other ports. Messages are forwarded only to ports that are not isolated from one another.

Description

202504771 Foreign version 1 Description Methods for redundant transmission of messages within a communication system with a multiple ring topology and communication system The present invention relates to a method for the redundant transmission of messages within a communication system with a multiple ring topology and a communication system suitable for carrying out the method, in particular for an industrial automation system. An industrial automation system typically comprises a large number of automation devices interconnected via an industrial communication network and serves to control or regulate plants, machines, or equipment within the context of manufacturing or process automation. Due to time-critical conditions in industrial automation systems, real-time communication protocols such as PROFINET, PROFIBUS, Real-Time Ethernet, or Time-Sensitive Networking (TSN) are predominantly used for communication between automation devices. Due to their use for often highly diverse applications, problems can arise in Ethernet-based communication networks, for example, when network resources for transmitting data streams or data frames with real-time requirements are competing for the transmission of data frames with large payloads without specific quality of service requirements. This can lead to data streams or data frames with real-time requirements not being transmitted according to the requested or required quality of service. Numerous redundancy protocols have been developed, particularly for industrial communication systems, to compensate for line or component failures or malfunctions. It is important to distinguish between interruptible redundancy methods, such as MRP (Media Redundancy Protocol) or RSTP / MSTP (Rapid / Multiple Spanning Tree Protocol), which switch from primary to backup paths during reconfiguration, and seamless redundancy methods. Seamless redundancy methods, such as HSR (High-availability Seamless Redundancy), PRP (Parallel Redundancy Protocol), or MRPD (Media Redundancy for Planned Duplication), generally do not require reconfiguration of the communication system, thus avoiding even brief communication interruptions. 2 EP 2838220 B1 relates to a method for redundant message transmission in a communication network with an arbitrarily meshed network topology. Several communication devices each comprise a first and a second transmitting and receiving unit. Each transmitting and receiving unit is assigned a signal processing unit, which duplicates messages to be sent redundantly by the communication device and transmits them to the receiving units. Messages redundantly received by the transmitting and receiving units are detected by the transmitting and receiving units at the communication device. For a communication link that is at least partially redundant between two network nodes, independent paths are determined within the communication network. Messages to be transmitted redundantly are exchanged within the communication network according to forwarding rules corresponding to the determined paths. From EP 4425875 A1, a method for highly available data transmission within a communication system is known. The system comprises a first and a second network segment, which are redundantly connected to each other via at least one first and a second coupling link. Within the first network segment, messages with user data are transmitted according to a spanning tree protocol, and messages with topology information are forwarded, also via the coupling links and within the second network segment. In a fault-free state, user data transmission between the two network segments occurs only via a first coupling device of the first network segment and the first coupling link. If no topology information is received via the second coupling link, a coupling port of a second coupling device is switched to an edge port mode.Devices in the second network segment delete their respective MAC address tables upon receiving topology information forwarded via the coupling port of the second coupling device. The earlier international patent application PCT / EP2025 / 081197 describes a method for transmitting datagrams according to a redundancy protocol, in which the datagrams are initially transmitted according to a first redundancy protocol used for redundant transmission of the datagrams within a first network segment. Between a first endpoint and a second endpoint, the datagrams are transmitted via a second network segment using a second redundancy protocol. The two endpoints connect the first and second network segments. Upon detection of a topology change in the first network segment, the second network segment is used. 3 When a detecting network device detects a topology change, it sends a topology change notification to other network devices in the first network segment. This causes the network devices in the first network segment to update their respective source address tables. Upon receiving the topology change notification at a first endpoint device encompassing the first endpoint, the first endpoint device deletes its source address table immediately or after waiting a predetermined initial duration and begins learning source addresses from other network devices. Upon receiving the topology change notification at a second endpoint device encompassing the second endpoint, the second endpoint device waits a predetermined second duration before deleting its source address table and beginning to learn source addresses from other network devices. The second duration is longer than the first. US Patent 2015 / 0138950 A1 discloses a redundant network implementation method in which ring networks with at least two nodes are used, interconnected via ring ports. In an initial state, all nodes are set as master stations, with the ring ports placed in a half-blocked state. In this state, MAC addresses from data sources are not accepted, and data messages are blocked, while protocol messages are forwarded. A master station is chosen by exchanging master station election messages containing node quality comparison vectors. At the chosen master station, one of the ports is kept in a half-blocked state, while the other ports are set to a forwarding state.A double ring network can be formed if two single ring networks have two shared nodes, with one of the ring networks operating as the primary ring network and the other as the secondary ring network.

[0034] The interconnected nodes can be selected as the master station and standby master station of the secondary ring network. The primary ring network manages the state of its ring ports and is responsible for forwarding protocol messages from the secondary ring network. Port isolation for communication devices connected to multiple rings is not disclosed in US 2015 / 0138950 A1. In MRP multi-ring topologies, MRP devices can operate as MRP clients for more than one ring instance. To ensure loop-free data exchange within such communication networks, it has previously been necessary to provide a separate VLAN (virtual local area network) configuration for each ring instance, both during initial setup and during subsequent configurations. 4 Operation. This involves a considerable amount of effort on the one hand, and on the other hand, not all switches support a comprehensive VLAN configuration. The present invention is based on the objective of providing a method for the redundant transmission of messages within a communication system with a multiple ring topology, which enables a low-effort and efficient configuration of communication devices, such as switches or bridges, and of providing a suitable implementation for carrying out the method. This problem is solved according to the invention by a method having the features specified in claim 1 and by a communication system having the features specified in claim 12. Advantageous embodiments of the present invention are specified in the dependent claims. According to the inventive method for the redundant transmission of messages within a communication system with a multiple ring topology, the messages are transmitted between communication devices connected to each other in a ring topology. Within a healthy ring, a selected communication device blocks one of its ports, through which it is connected to the ring, from forwarding messages containing user data. Preferably, the messages between the communication devices within the same ring are transmitted according to the Media Redundancy Protocol (MRP), wherein the selected communication devices are MRP redundancy managers, while all other communication devices are MRP clients. According to the invention, the communication devices each comprise at least two ports connected by a ring and send outgoing messages from each of these ports into the respective ring via both ports. Communication devices connected to multiple rings operate their ports assigned to the respective ring in isolation from all other ports. Messages are only forwarded to ports that are not isolated from each other. To establish port isolation, a list of destination ports on the same communication device is defined for each isolated port, to which the respective isolated port is permitted to send messages. Messages sent to ports not included in the list of destination ports are advantageously discarded or deleted from the respective send queue. In particular, the port isolation is configured for the isolated ports without configuring a virtual local area network (VLAN).The present invention thus enables a 202504771 foreign version. 5 Simplified setup of redundancy procedures in communication systems with a multi-ring topology, i.e., with several interconnected rings. Significant simplification can be achieved, particularly by eliminating the previously required VLAN configuration. In principle, non-ring ports of the communication devices can also be included in port isolation on the respective communication device for a selected ring. According to an advantageous embodiment of the present invention, the selected communication devices each send diagnostic messages to detect a link interruption within their respective ring. If a previously sent diagnostic message is not received, the selected communication devices detect a link interruption within their respective ring. After detecting a link interruption, the selected communication devices switch their blocked port to a forwarding state. In this way, a redundancy method can be implemented, and the formation of loops in a communication network can be prevented.Furthermore, if a ring is error-free, with the exception of the respective selected communication device, all communication devices within the ring preferably disable the learning of source MAC addresses from received messages on their ports assigned to the ring and delete their respective source address table. According to a particularly preferred embodiment of the present invention, the communication devices or MRP clients monitor diagnostic messages sent by the respective selected communication device or MRP redundancy manager to detect a link interruption within the respective ring. If the diagnostic messages from the respective MRP redundancy manager fail to materialize for a predetermined period, the MRP clients terminate the isolated operation of their ports assigned to the respective ring. In this way, redundancy methods can be used in communication networks with a multi-ring topology without requiring routing between the individual rings to establish connectivity between the rings and prevent loops. Preferably, upon detecting a link interruption, the MRP clients send a topology change message within the respective ring. Upon receiving such a topology change message, the MRP clients terminate the isolated operation of their ports that are assigned to a ring affected by the topology change message. (Furthermore, 202504771 Foreign Version) 6 Upon receiving a topology change notification, MRP clients delete their respective source address tables and reactivate the teaching of source MAC addresses to their ports assigned to the ring affected by the topology change notification. This allows redundancy procedures to be implemented particularly reliably and efficiently in multi-ring communication networks without the need for VLANs and routing. In principle, only one MRP redundancy manager can be designated for all rings within a multi-ring topology. In this case, if the MRP redundancy manager fails or shuts down, the MRP clients terminate the isolated operation of all their ports.In contrast, when receiving recurring diagnostic messages from the respective MRP redundancy manager, the MRP clients advantageously operate their ports assigned to the respective ring in isolation, thereby disabling the learning of source MAC addresses on their ports assigned to the respective ring. The communication system according to the invention is designed to carry out a method as described above and features a multiple ring topology as well as several communication devices interconnected in a ring topology. Within a fault-free ring, a selected communication device is configured to block one of its ports, through which it is connected to the ring, from forwarding messages containing user data. The communication devices each comprise at least two ports connected to a ring and are configured to send outgoing messages from each device to the respective ring via both ports. Furthermore, communication devices connected to multiple rings are configured to operate their ports assigned to the respective ring in isolation from all other ports. Messages are only forwarded to ports that are not isolated from each other.To set up port isolation, a list of destination ports on the same communication device is defined for each isolated port, to which the respective isolated port is allowed to send messages. The present invention is explained in more detail below using an exemplary embodiment with reference to the drawing. It shows Figure 1 shows a communication system with a total of three selected communication devices and a multiple ring topology for redundant transmission of messages between communication devices connected to each other in a ring topology, 202504771 Foreign version 7 Figure 2 shows a simplified version of the communication system shown in Figure 1 with only one selected communication device. Figure 3 shows the communication system according to Figure 2 with a multiple fault in one ring, Figure 4 shows the communication system according to Figure 2 with a failure of the selected communication device. The communication system shown in Figure 1 has a multiple ring topology and comprises several communication devices 101-102, 111-112, 121-123, 131-134, each connected in a ring topology. The communication devices 101-102, 111-112, 121-123, 131-134 are, in particular, switches or bridges. In the present embodiment, a first ring with dashed links comprises the communication devices 101-102, 111-112, while a second ring with links shown in normal line thickness comprises the communication devices 101-102, 121-123. Furthermore, a third ring with links shown in thick line thickness comprises the communication devices 101-102, 131-134. With the exception of communication devices 101-102, all communication devices 111-112, 121-123, and 131-134 are assigned to only one ring. Communication devices 101-102, however, are assigned to all three rings.In particular, the communication devices 111-112, 121-123, 131-134 each comprise at least 2 ports connected to a ring and send outgoing messages via both ports into the respective ring for redundant transmission. Within the first ring, communication device 111 is directly connected to communication devices 101 and 102, which in turn are each directly connected to communication device 112. Furthermore, within the second ring, communication device 121 is directly connected to communication devices 101 and 102. Additionally, communication device 101 is directly connected to communication device 122, while communication device 102 is also directly connected to communication device 123. Finally, communication devices 122 and 123 are directly connected to each other within the second ring. Furthermore, within the third ring, communication device 131 is directly connected to communication devices 101 and 102. Additionally, communication device 101 is directly connected to communication device 132, while communication device 102 is also directly connected to communication device 134.Finally, within the third 202504771 foreign version. 8 The communication device 133 is directly connected to both the communication device 132 and the communication device 134. According to the embodiment shown in Figure 1, each ring contains a selected communication device 111, 123, 133. In a topologically sound ring without link or port failures, each device blocks one of its ports connected to the ring from forwarding messages containing user data. This is symbolized by an asterisk next to the respective port in Figure 1. For example, on the selected communication device 111 within the first ring, the port on the link to communication device 101 is blocked, while on the selected communication device 123 within the second ring, the port on the link to communication device 102 is blocked. Furthermore, in this embodiment, on the selected communication device 133 within the third ring, the port on the link to communication device 132 is blocked.Links disabled by blocking the respective ports for user data transmission are shown in gray in Figure 1. The selected communication devices 111, 123, and 133 each send diagnostic messages 10 to detect a link interruption within their respective ring. If a previously sent diagnostic message 10 is not received, the selected communication devices 111, 123, and 133 detect a link interruption within their respective ring. After detecting a link interruption, the selected communication devices 111, 123, and 133 each switch their previously blocked port to a forwarding state. In this embodiment, the messages between the communication devices 101-102, 111-112, 121-123, and 131-134 within the same ring are transmitted according to the Media Redundancy Protocol (MRP). The selected communication devices 111, 123, 133 are each MRP redundancy managers, while all other communication devices 101-102, 112, 121-122, 131-132, 134 are MRP clients. MRP clients 101 and 102, which are connected to multiple rings, operate their respective ring-assigned ports A1-A2, A3-A4, A5-A6, B1-B2, B3-B4, and B5-B6 in isolation from all other ports. Messages are only forwarded to ports that are not isolated from each other. In Figure 1, this is symbolized by a graphic marker on each port that is isolated from all other ports: a diamond on ports A1-A2 and B1-B2 for the first ring, a circle on ports A3-A4 and B3-B4 for the second ring, and a square on ports A5-A6 and B5-B6 for the third ring. (External version 202504771) 9 If a ring is error-free, with the exception of MRP redundancy managers 111, 123, 133, all MRP clients 101-102, 112, 121-122, 131-132, 134 disable the learning of source MAC addresses from messages received within the respective ring at their ports assigned to the respective ring and delete their respective source address table. To configure port isolation, a list of destination ports on the same communication device is preferably defined for each isolated port. These destination ports are the ones to which the isolated port is permitted to send messages. Accordingly, messages sent to ports not included in the destination port list are discarded or deleted from their respective send queues. Specifically, port isolation is configured for each isolated port without configuring a virtual local area network (VLAN). In the variant of the communication system shown in Figure 2, as per Figure 1, only one MRP Redundancy Manager 201 is provided for all three rings, for the sake of simplicity. The first ring, represented by dashed links, includes MRP Redundancy Manager 201 and MRP Clients 202, 211-212. The second ring, represented by links with a normal line thickness, includes MRP Redundancy Manager 201 and MRP Clients 202, 221-223. The third ring, represented by links with a thick line thickness, includes MRP Redundancy Manager 201 and MRP Clients 202, 231-234. With the exception of MRP Client 202, all MRP Clients 211-212, 221-223, and 231-234 are assigned to only one ring. In contrast, the MRP client 202 is assigned to all three rings. Analogous to previous descriptions, in the variant shown in Figure 2, within the first ring, MRP client 211 is directly connected to MRP redundancy manager 201 and MRP client 202, which in turn are each directly connected to MRP client 212. Furthermore, within the second ring, MRP client 221 is directly connected to MRP redundancy manager 201 and MRP client 202. Additionally, MRP redundancy manager 201 is directly connected to MRP client 222, while MRP client 202 is also directly connected to MRP client 223. Finally, MRP client 222 and MRP client 223 are directly connected to each other within the second ring. Finally, within the third ring, MRP client 231 is directly connected to MRP redundancy manager 201 and MRP client 202. Furthermore, the MRP Redundancy Manager 201 is directly connected to the MRP Client 232, while the MRP Client 202 is additionally directly connected to the MRP Client 234.Finally, within the third ring, MRP client 233 is directly connected to both MRP client 232 and MRP client 234. 202504771 Foreign version. 10 According to the variant shown in Figure 2, the MRP redundancy manager 201 blocks one of its ports per ring to prevent the forwarding of messages containing user data in topologically sound rings. This is also symbolized by an asterisk next to the respective port in Figure 2. For example, within the first ring, the port on the link to MRP client 212 is blocked on the MRP redundancy manager 201, while within the second ring, the port on the link to MRP client 222 is blocked. Furthermore, in this embodiment, the port on the link to MRP client 231 within the third ring is also blocked on the MRP redundancy manager 201. Links deactivated by blocking the respective ports for user data transmission are also shown in gray in Figure 2. The MRP client 202, which is connected to all three rings, operates its ports P1-P2, P3-P4, and P5-P6 assigned to each ring in isolation from all other ports, analogous to the above descriptions. This is also symbolized in Figure 2 by a diamond on ports P1-P2 for the first ring, by a circle on ports P3-P4 for the second ring, and by a square on ports P5-P6 for the third ring. Additionally, in the variant shown in Figure 2, an automation device 213, for example, a programmable logic controller (PLC), is connected to a non-ring port of the MRP client 202. In this embodiment, the automation device is included in port isolation on the MRP client 202 for the first ring. This is symbolized by a diamond on the non-ring port of the MRP client 202. MRP clients 202, 211-212, 221-223, and 231-234 monitor diagnostic messages 10 sent by their respective MRP redundancy managers to detect link breaks within their respective rings. Upon detection of a link break, MRP clients 202, 211-212, 221-223, and 231-234 send a topology change message 11 within their respective rings. MRP clients with active port isolation terminate isolated operation of their ports assigned to the respective ring, or of ports assigned to a ring affected by the topology change message, if diagnostic messages 10 from the respective MRP redundancy manager are not received for a predefined period (e.g., 60 ms) or upon receipt of a topology change message 11. Furthermore, the MRP clients delete the diagnostic messages if they are not received. Upon receiving the topology change message, the MRP client advantageously updates its respective source address table and reactivates the teaching of source MAC addresses to its ports, which are assigned to the ring affected by the absence of diagnostic messages or the topology change message. Furthermore, isolation of non-ring ports is also terminated when the MRP client removes port isolations of assigned ring instances. 202504771 Foreign version 11 Figure 3 shows the communication system according to Figure 2 with a multiple fault in one of the three rings. According to the present embodiment, two links in the second ring have failed: the link between MRP Manager 201 and MRP Client 221, and the link between MRP Clients 222-223. In this case, MRP Client 202, which is assigned to all three rings, no longer receives diagnostic messages 10 from MRP Redundancy Manager 201 via the second ring. Consequently, MRP Client 202 terminates its port isolations with respect to the second ring. This is symbolized in Figure 3 by the removal of the diamonds used to mark the port isolations at ports P3-P4. If the MRP Redundancy Manager 201 is shut down or fails completely, the MRP clients with active port isolation terminate the isolated operation of all their ports. Figure 4 illustrates such a failure, which manifests as a link-down on all six links of the MRP Redundancy Manager 201 to the MRP clients 211-212, 221-222, and 231-231. In this case, the diagnostic messages 10 do not reach the MRP client 202, which is assigned to all three rings, via any of the three rings. Consequently, the MRP client 202 terminates its port isolations with respect to all three rings. This is symbolized in Figure 4 by the removal of all port isolation markers on ports P1-P6. When recurring diagnostic messages are received from the MRP Redundancy Manager, the MRP clients preferably automatically return their ports assigned to the respective ring to isolated operation and disable the learning of source MAC addresses on their ports assigned to the respective ring.

Claims

202504771 Foreign version 12 Patent claims 1. Method for redundant transmission of messages within a communication system with a multiple ring topology, in which - the messages are transmitted between communication devices (101-102, 111-112, 121-123, 131-134) connected to each other in a ring topology, whereby a selected communication device within (111, 123, 133) of a fault-free ring blocks one of its ports, through which it is connected to the ring, from forwarding messages with payload data, - the communication devices each comprise at least 2 ports connected by a ring and each send outgoing messages via both ports into the respective ring, - Communication devices (101-102) connected to multiple rings operate their respective ring-assigned ports (A1-A2, A3-A4, A5-A6, B1-B2, B3-B4, B5-B6) in isolation from all other ports, with messages only being forwarded to non-isolated ports, - to set up port isolation, a list of destination ports on the same communication device is defined for each isolated port, to which the respective isolated port is allowed to send messages.

2. Method according to claim 1, where messages sent to ports not included in the list of destination ports are discarded and / or deleted from their respective send queues.

3. Method according to one of claims 1 or 2, where the port isolation setup for the isolated ports is defined without configuring a virtual local area network (VLAN).

4. Method according to any one of claims 1 to 3, where the selected communication devices (101-102) each send diagnostic messages (10) to detect a link interruption within their respective ring, where the selected communication devices each detect a link interruption within their respective ring if a previously sent diagnostic message is not received, and where the selected communication devices each switch their blocked port to a forwarding state after detecting a link interruption. 202504771 Foreign version 13 5. Method according to any one of claims 1 to 4, In the case of an error-free ring, with the exception of the respective selected communication device, all communication devices within the ring deactivate the learning of source MAC addresses from received messages on their ports assigned to the ring and delete their respective source address table.

6. Method according to any one of claims 1 to 5, where messages between communication devices within the same ring are transmitted according to Media Redundancy Protocol (MRP), where the selected communication devices are each MRP redundancy managers, and where all other communication devices are MRP clients.

7. Method according to claim 6, in which the MRP clients (202, 211-212, 221-223, 231-234) monitor diagnostic messages (10) sent by the respective MRP redundancy manager (201) to detect a link interruption within the respective ring and in which, in the event of a failure to receive diagnostic messages from the respective MRP redundancy manager for a specified period of time, the MRP clients (202) terminate isolated operation of their ports (P3-P4; P1-P6) assigned to the respective ring.

8. Method according to claim 7, where the MRP clients (202, 211-212, 221-223, 231-234) send a topology change message (11) within the respective ring upon detection of a link break, where the MRP clients (202) terminate the isolated operation of their ports (P3-P4; P1-P6) assigned to a ring affected by the topology change message upon receipt, and where the MRP clients additionally delete their respective source address table and reactivate the teaching of source MAC addresses on their ports assigned to the ring affected by the topology change message upon receipt of the topology change message.

9. Method according to one of claims 6 or 7, where, within the multi-ring topology, exactly one MRP redundancy manager is provided for all rings, and where, in the event of a failure or shutdown of the MRP redundancy manager, the MRP clients cease the isolated operation of all their ports. 202504771 Foreign version 14 10. Method according to any one of claims 7 to 9, where, upon receiving recurring diagnostic messages from the respective MRP redundancy manager, the MRP clients operate their ports assigned to the respective ring in isolation and disable the learning of source MAC addresses on their ports assigned to the respective ring.

11. Method according to any one of claims 1 to 10, The non-ring ports of the communication devices are each included in port isolation on the respective communication device for a selected ring.

12. Communication system for carrying out a method according to one of claims 1 to 11, wherein the communication system - has a multiple ring topology and several communication devices connected to each other in a ring topology, wherein one selected communication device is configured within a fault-free ring to block one of its ports, through which it is connected to the ring, from forwarding messages containing payload data, - wherein the communication devices each comprise at least 2 ports connected in a ring and are configured to send outgoing messages from them via both ports into the respective ring, - wherein communication devices connected to multiple rings are configured to operate their ports assigned to the respective ring in isolation from all other ports, with messages being forwarded only to non-isolated ports and, for the establishment of port isolation, a list of destination ports on the same communication device is specified for each isolated port, to which the respective isolated port may send messages.

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