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EP-4742617-A1 - METHOD OF TRANSMITTING DATAGRAMS ACCORDING TO A REDUNDANCY PROTOCOL AND NETWORK DEVICE

EP4742617A1EP 4742617 A1EP4742617 A1EP 4742617A1EP-4742617-A1

Abstract

The invention relates to transmitting datagrams according to a redundancy protocol, wherein the datagrams are originally transmitted according to a first redundancy protocol which is employed for redundantly transmitting the datagrams within a first network section (MRP1, MRP2, MRP3, MRP4, RSTP1, RSTP2). Between a first endpoint and a second endpoint, the datagrams are transmitted via a second network section (HSR1) in which a second redundancy protocol is employed, wherein the two endpoints interface the first network section and the second network section. Upon detecting a topology change in the first network section by a detecting network device (111), the detecting network device sends a topology change notification (TC) to other network devices in the first network section, the topology change notification causing network devices (111-112, 121-124, 131-132, 141-145, 151-153) in the first network section to update their respective source address table. Upon receiving the topology change notification at a first endpoint device (201-206, 209-210) comprising the first endpoint, the first endpoint device clears its source address table immediately or after waiting a predetermined first duration and starts learning source addresses of other network devices. Upon receiving the topology change notification at a second endpoint device comprising the second endpoint, the second endpoint device waits a predetermined second duration before clearing its source address table and starting to learn source addresses of other network devices, the second duration being longer than the first duration.

Inventors

  • KESKIN, FARUK
  • Meenakshi Sundaram, Singaravelan

Assignees

  • Siemens Aktiengesellschaft

Dates

Publication Date
20260513
Application Date
20241111

Claims (15)

  1. Method of transmitting datagrams according to a redundancy protocol, wherein - the datagrams are originally transmitted according to a first redundancy protocol which is employed for redundantly transmitting the datagrams within a first network section (MRP1, MRP2, MRP3, MRP4, RSTP1, RSTP2), - the datagrams are transmitted between a first endpoint and a second endpoint via a second network section (HSR1) in which a second redundancy protocol is employed, wherein the two endpoints interface the first network section and the second network section, - upon detecting a topology change in the first network section by a detecting network device (111), the detecting network device sends a topology change notification (TC) to other network devices in the first network section, the topology change notification causing network devices (111-112, 121-124, 131-132, 141-145, 151-153) in the first network section to update their respective source address table, - upon receiving the topology change notification at a first endpoint device (201-206, 209-210) comprising the first endpoint, the first endpoint device clears its source address table immediately or after waiting a predetermined first duration and starts learning source addresses of other network devices, - upon receiving the topology change notification at a second endpoint device comprising the second endpoint, the second endpoint device waits a predetermined second duration before clearing its source address table and starting to learn source addresses of other network devices, the second duration being longer than the first duration.
  2. Method according to claim 1, wherein the first redundancy protocol is a media redundancy protocol, particularly MRP, or a spanning tree protocol, particularly STP, RSTP, or MSTP, and wherein the second redundancy protocol is a seamless ring redundancy protocol, particularly HSR, a parallel redundancy protocol, particularly PRP, or a protocol for redundantly transmitting streams, particularly FRER.
  3. Method according to one of the claims 1 or 2, wherein the two endpoints are each associated with an interlink port of an HSR or PRP network device (201-206, 209-210), particularly an HSR/PRP RedBox, and wherein datagrams from the first network section are transparently tunneled through the second network section (HSR1) via the interlink ports.
  4. Method according to claim 3, wherein the topology change notification (TC) is received via the interlink port of one HSR or PRP network device (201-206, 209-210) only, wherein the first endpoint device is the HSR or PRP network device receiving the topology change notification via its interlink port, and wherein the second endpoint device is the HSR or PRP network device receiving the topology change notification via the second network section.
  5. Method according to claim 4, wherein, upon receiving the topology change notification (TC) at the first endpoint device (201-206, 209-210), the first endpoint device clears its source address table essentially immediately and starts learning source addresses of other network devices in the first network section,
  6. Method according to one of the claims 4 or 5, wherein the first redundancy protocol is a media redundancy protocol, particularly MRP.
  7. Method according to claim 3, wherein an HSR or PRP network device (201-206, 209-210) having received a topology change (TC) notification via its interlink port waits the first duration, whether a corresponding topology change notification is received via the second network section (HSR1), and wherein said HSR or PRP network device acts as the first endpoint device in absence of a corresponding topology change notification received via the second network section during the first duration.
  8. Method according to one of the claims 3 or 7, wherein an HSR or PRP network device (201-206, 209-210) having received a topology change notification (TC) via the second network section (HSR1) waits at least the first duration, whether a corresponding topology change notification is received via its interlink port, and wherein said HSR or PRP network device acts as the second endpoint device in absence of a corresponding topology change notification received via its interlink port during at least the first duration.
  9. Method according to one of the claims 7 or 8, wherein waiting the first duration or the at least first duration is skipped for at least one predetermined first redundancy protocol, and wherein an information on the employed first redundancy protocol is derived from the received topology change notification.
  10. Method according to one of the claims 3, 7 or 8, wherein the two HSR or PRP network devices determine their respective role as the first second endpoint device or as the second endpoint device based on a source address in a corresponding topology change notification forwarded over the second network section, if the topology change notification is received via the interlink ports of both HSR or PRP network devices.
  11. Method according to one of the claims 7, 8 or 10, wherein the first redundancy protocol is a spanning tree protocol, particularly STP, RSTP, or MSTP.
  12. Method according to one of the claims 1 to 11, wherein the second duration is shorter than a reconfiguration time after network topology changes achieved by means of the first redundancy protocol.
  13. Network device for transmitting datagrams according to a redundancy protocol, wherein the network device is configured to - transmit the datagrams according to a first redundancy protocol which is employed for redundantly transmitting the datagrams within a first network section (MRP1, MRP2, MRP3, MRP4, RSTP1, RSTP2), - selectively act as a first endpoint device (201-206, 209-210) comprising a first endpoint or as a second endpoint device comprising a second endpoint, wherein the datagrams are transmitted between the two endpoints via a second network section (HSR1) in which a second redundancy protocol is employed, and wherein the first endpoint and the second endpoint interface the first network section and the second network section, - receive topology change notifications (TC) causing network devices (111-112, 121-124, 131-132, 141-145, 151-153) in the first network section to update their respective source address table, wherein, upon detecting a topology change in the first network section by a detecting network device (111), the detecting network device sends a topology change notification to other network devices in the first network section, - upon receiving a topology change notification when acting as a first endpoint device, clear its source address table immediately or after waiting a predetermined first duration, and start learning source addresses of other network devices, - upon receiving a topology change notification when acting as a second endpoint device, wait a predetermined second duration before clearing its source address table and starting to learn source addresses of other network devices, the second duration being longer than the first duration.
  14. Network device according to claim 13, wherein the network device comprises a switch functionality and/or HSR/PRP RedBox functionality.
  15. Network device according to one of the claims 13 or 14, wherein the network device is configured to implement a method according to one of the claims 1 to 12.

Description

The present invention relates to a method of transmitting datagrams according to a redundancy protocol, e.g. within a communication network of an industrial automation system, and a network device for transmitting datagrams according to a redundancy protocol. Industrial automation systems are designed to monitor and control technical processes, particularly for factory, process or building automation, and provide for operating control devices, sensors, machines, and industrial plants autonomously and substantially independent from human intervention. Usually, industrial automation systems comprise a plurality of automation devices interconnected with each other via an industrial communication network. Due to a continuously growing impact of information technology on industrial automation systems, approaches for reliably providing monitoring and control functions within industrial automation systems gain increasing importance. Challenges experienced in industrial automation systems frequently result from message traffic with a large number of messages which are relatively short. Generally, interruptions of communication connections might cause an unfavourable repetition of transmission of messages. Again, this usually results in additional loads on communication connections, which may further lead to malfunctions or system faults. If messages are not transmitted at all or not transmitted completely, an industrial automation system may be prevented from changing into a safe operating state or from remaining in such a safe operating state. Finally, this may lead to a costly outage of an entire production system. In EP 3 881 506 B1, a method for operating a communication system having redundant routers is described, wherein datagrams are forwarded within the communication system from source communication devices to destination communication devices by routers on the basis of routing information stored in routing tables of the routers. According to EP 3 881 506 B1, within a communication system having redundant routers, datagrams are forwarded from source communication devices to target communication devices by means of routers based on routing information stored in routing tables of the routers. For each end device, a virtual router is configured as a default gateway. The virtual router is associated with a group of several routers. Routers from the same group select among themselves a router operated as the active default gateway. The routers not operated as the active default gateway are operated as reserve gateways. The reserve gateways request from the active default gateway a transmission of stored address associations between data link layer addresses and network layer addresses of all detected communication devices. Only upon request, the active default gateway transmits all stored address associations in bundled form to a requesting reserve gateway. The reserve gateways update their respective configuration based on the address associations transmitted by the active default gateway directly and without waiting for results from a training process carried out by themselves. In case of a failure of the active default gateway and selecting a new active default gateway, the new active default gateway takes over all address associations transmitted before the failure and a virtual data link layer address assigned to the virtual router for its operation as new active default gateway. EP4283925A1 relates to a secure transmission of time-critical data within a communication system, which comprises several local networks, in which data is transmitted by means of switching, and an overlay network, in which data is transmitted by means of routing. A gateway system is provided for connecting the communication system to at least one unsecured external network. Network layer communication over the overlay network is only authorized between authenticated system components. Switches authenticate connected end devices and assign them to a physical or logical local network according to a respective end device identity. Data link layer communication is implicitly authorized within the local networks based on an assignment of the respective end devices to the same local network. Communication at OSI layer 3-7 between end devices on different local networks or with end devices in the unsecured external network is authorized using zero trust proxies, each of which is assigned to a local network. Network devices acting as endpoint devices interconnecting network sections in which different redundancy protocols are employed usually clear their source address tables after having received a topology change notification from one of the network sections. If a first network section is coupled to a second network section via two endpoint devices, clearing the source address tables simultaneously in both endpoint devices in response to a topology change notification from the first network section may lead to a traffic loss in the seco