US-12627525-B2 - Network switch, communication system and method for operating a communication system for transmitting time-critical data

US12627525B2US 12627525 B2US12627525 B2US 12627525B2US-12627525-B2

Abstract

Method for operating a communication system for transmitting time-critical data, wherein the datagrams are forwarded from a first communication device to a first network switch based on an identifier of a first virtual local network and a priority specification, where the first network switch encapsulates the datagrams sent by the first communication device in respective data frames, which are assigned to a data stream through a third sub-network, and inserts an identifier of a second virtual local network into the data frames, resources along a selected path are reserved in the third sub-network based on the identifier of the second virtual local network and a second network switch removes the datagrams encapsulated in the data frames assigned to the data stream from the received data frames and forwards the removed datagrams to a second communication device based on the identifier of the first virtual local network and the priority specification.

Inventors

Markus Neumann

Assignees

SIEMENS AKTIENGESELLSCHAFT

Dates

Publication Date: 20260512
Application Date: 20210428
Priority Date: 20200528

Claims (14)

1 . A method for operating a communication system for transmitting time-critical data, datagrams being sent from a first communication device in a first sub-network and being sent to a second communication device in a second sub-network via a third sub-network, the first and third sub-networks being interconnected via a first network switch, and the second and third sub-networks being interconnected via a second network switch, the method comprising: inserting, by the first communication device, an identifier of a first virtual local network and a priority specification into the datagrams; forwarding the datagrams from the first communication device to the first network switch utilizing the identifier of the first virtual local network and the priority specification; encapsulating, by the first switch, the datagrams sent by the first communication device in respective data frames which are assigned to a data stream through the third sub-network, and inserting an identifier of a second virtual local network into the data frames; reserving resources along a selected path between the first switch and the second switch utilizing the identifier of the second virtual local network to transmit the data stream in the third sub-network; extracting, by the second network switch, the datagrams encapsulated in the data frames assigned to the data stream from received data frames and forwarding the extracted datagrams to the second communication device utilizing the identifier of the first virtual local network and the priority specification; wherein at least one of the first network switch and the second network switch encapsulates respective datagrams by inserting the respective datagrams into a user data region of the data frames; wherein the user data region comprises the identifier of the first virtual local network and the priority specification; and wherein the data frames in which the respective datagrams are encapsulated are VXLAN frames or frames for Layer 2 tunneling of the datagrams.
2 . The method as claimed in claim 1 , wherein at least one of the first network switch and the second network switch specifies quality of service parameters in a reservation request to reserve the resources for the data stream along the selected path; wherein each communication device forwarding data frames along the selected path or a communication control device uses the service quality parameters to verify when a reservation request is made whether sufficient resources are available in the respective communication device for data transmission in compliance with the specified quality of service parameters; wherein the communication devices along the selected path or the communication control device for the data stream, in cases of sufficient resources existing, determine respective configuration information; and wherein the communication devices along the selected path are configured according to the determined configuration information for resource provision for the data stream.
3 . The method as claimed in claim 2 , wherein the resources to be provided by the communication devices along the selected path include at least one of (i) usable transmission time windows, (ii) bandwidth, (iii) guaranteed maximum latency, (iv) queue count, (v) queue cache and (vi) address cache in network switches or bridges.
4 . The method as claimed in claim 3 , wherein the third sub-network is a time-sensitive network.
5 . The method as claimed in claim 4 , wherein the time-sensitive network is compliant with at least one of (i) Institute of Electrical and Electronics Engineers (IEEE) standard 802.3-2018, (ii) IEEE standard 802.1Q-2018, (iii) IEEE standard 802.1AB-2016, (iv) IEEE standard 802.1AS-2011, (v) IEEE standard 802.1BA-2011 and (vi) IEEE standard 802.1CB-2017.
6 . The method as claimed in claim 2 , wherein the third sub-network is a time-sensitive network.
7 . The method as claimed in claim 6 , wherein the time-sensitive network is compliant with at least one of (i) Institute of Electrical and Electronics Engineers (IEEE) standard 802.3-2018, (ii) IEEE standard 802.1Q-2018, (iii) IEEE standard 802.1AB-2016, (iv) IEEE standard 802.1AS-2011, (v) IEEE standard 802.1BA-2011 and (vi) IEEE standard 802.1CB-2017.
8 . The method as claimed in claim 6 , wherein forwarding of data frames within the third sub-network is controlled by at least one of (i) Frame Preemption, (ii) Time-Aware Shaper, (iii) Credit-based Shaper, (iv) Burst Limiting Shaper, (v) Peristaltic Shaper and (vi) priority-based in accordance with Institute of Electrical and Electronics Engineers (IEEE) standard 802.1Q-2018.
9 . The method as claimed in claim 2 , wherein the data stream is configured bi-directionally in response to a reservation request.
10 . The method as claimed in claim 1 , wherein the second communication device inserts the identifier of the first virtual local network and the priority specification into datagrams to be sent to the first communication device; wherein the datagrams to be sent to the first communication device are forwarded from the second communication device to the second network switch utilizing the identifier of the first virtual local network and the priority specification; wherein the second switch encapsulates the datagrams sent by the second communication device in respective data frames which are assigned to the data stream through the third sub-network, and inserts the identifier of the second virtual local network into the data frames; and wherein the first network switch extracts the datagrams encapsulated in the data frames assigned to the data stream from received data frames and forwards the extracted datagrams to the first communication device using the identifier of the first virtual local network and the priority specification.
11 . The method as claimed in claim 1 , wherein the first and second sub-networks are assigned to PROFINET cells, wherein the third sub-network is a TSN-based transit network; and wherein the datagrams are PROFINET frames.
12 . The method as claimed in claim 1 , wherein at least one of the first switch and second switch assigns the identifier of the second virtual local network to data frames to be sent through the third sub-network which encapsulates datagrams, based on Ingress ports.
13 . A network switch, comprising: a plurality of ports for connecting to at least one of communication devices and communication terminals forwarding datagrams; wherein the network switch is configured to: send datagrams from a first communication device in a first sub-network and to a second communication device in a second sub-network via a third sub-network, an identifier of a first virtual local network and a priority specification being inserted into datagrams sent by the first communication device; encapsulate the datagrams sent by the first communication device in respective data frames which are assigned to a data stream through the third sub-network, and to insert an identifier of a second virtual local network into the data frames; extract the datagrams encapsulated in the data frames assigned to the data stream from received data frames; and forward the extracted datagrams to the second communication device using the identifier of the first virtual local network and the priority specification, wherein the network switch encapsulates respective datagrams by inserting the respective datagrams into a user data region of the data frames; wherein the user data region comprises the identifier of the first virtual local network and the priority specification; and wherein the data frames in which the respective datagrams are encapsulated are VXLAN frames or frames for Layer 2 tunneling of the datagrams.
14 . A communication system for transmitting time-critical data, comprising: a first sub-network; a second sub-network; a third sub-network; a first network switch which interconnects the first and third sub-networks; a second network switch which interconnects the second and third sub-networks; and a first communication device in the first sub-network and a second communication device in the second sub-network, the first communication device being configured to send datagrams to the second communication device via the third sub-network and to insert into the datagrams an identifier of a first virtual local network and a priority specification, on the basis of which the datagrams are forwarded from the first communication device to the first network switch; wherein the first switch is configured to encapsulate the datagrams sent by the first communication device in data frames assigned to a data stream through the third sub-network, and to insert in the data frames of a second virtual local network an identifier, on the basis of which resources along a selected path between the first switch and the second switch are reserved to transmit the data stream in the third sub-network, wherein the second network switch is configured to extract the datagrams encapsulated in the data frames assigned to the data stream from received data frames and to forward the extracted datagrams to the second communication device utilizing the identifier of the first virtual local network and the priority specification; wherein at least one of the first network switch and the second network switch encapsulates respective datagrams by inserting the respective datagrams into a user data region of the data frames; wherein the user data region comprises the identifier of the first virtual local network and the priority specification; and wherein the data frames in which the respective datagrams are encapsulated are VXLAN frames or frames for Layer 2 tunneling of the datagrams.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS This is a U.S. national stage of application No. PCT/EP2021/061123 filed 28 Apr. 2021. Priority is claimed on European Application No. 20177065.8 filed 28 May 2020, the content of which is incorporated herein by reference in its entirety. BACKGROUND OF THE INVENTION 1. Field of the Invention The invention relates to a network switch, a communication system and method for operating the communication system for transmitting time-critical data, in particular control data in an industrial automation system. 2. Description of the Related Art An industrial automation system usually comprises a large number of automation devices networked together via an industrial communication network and is used as part of a production or process automation system for controlling or regulating plants, machines or devices. Due to time-critical constraints 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. For example, because of their use for often very different applications, problems can arise in Ethernet-based communication networks when network resources are allocated for the transmission of data streams or data frames with real-time requirements competing for the transmission of data frames with large useful data content without specific service-level requirements. This can result in data streams or data frames with real-time requirements not being delivered in accordance with the requested or required quality of service. Prioritized transmission of data frames is possible, for example, on the basis of virtual local area networks or virtual local area networks (VLAN) in accordance with the Institute of Electrical and Electronics Engineers (IEEE) 802.1Q standard, via appropriate tags inserted in data frames. For the synchronized and prioritized transmission of audio and video data streams (audio/video bridging) over communication networks, bandwidth reservation is provided for individual communication connections that are assigned a highest priority. Resources required for the transmission of audio and video data streams are reserved in communication devices, such as network switches. However, the forwarding of high-priority data frames only occurs after a successful reservation. Bandwidth monitoring is used to ensure that sufficient bandwidth is reserved in relation to the actual bandwidth used. A communication link that uses more bandwidth than is reserved would otherwise cause a malfunction of an entire communication network, and in the worst case, disable it due to overloading. Credit-based Shapers (CBS) have been defined as a measure of bandwidth monitoring for the secure transmission of audio and video data streams over Ethernet-based communication networks in accordance with the IEEE 802.1 Qav standard. A credit-based shaper defines a transmission pause after each transmitted data frame to ensure bandwidth limitation in relation to a reserved bandwidth. However, in industrial automation systems when many data frames with low user data content are transferred for control data, which can be better regarded as data bundles or bursts, such forced pauses are extremely problematic. WO 2019/001718 A1 describes a method for data transmission that allows a combination of protected communication and low network configuration overhead. When reserving resources for transferring data streams (streams) from a sender to a receiver, at least two paths are reserved, at least some sections of which are redundant. Extending a reservation protocol automatically configures duplicate filters on network nodes assigned to redundant path sections during a resource reservation. European patent application 20170149.7 discloses a method for transmitting time-critical data, in which selected datagrams are assigned to data streams and transmitted between first communication devices and second communication devices via paths comprising at least the first and second communication devices. Reservation requests to provide resources for transferring the data streams are each transmitted to a domain controller. In the event of reservation requests, the domain controllers check whether the respective first and second communication device are contained in the same domain. Cross-domain reservation requests are each forwarded to a higher-level communication control device. The higher-level communication control device identifies domains affected by the reservation requests and transmits partial reservation requests restricted to respective sections of the paths to the domain controllers of the identified domains. EP 3 035 606 A1 describes a method for data transmission in a communication network comprising at least 2 virtual local networks, in which data streams are each assigned a data stream-specific target device identifier. When a data stream is t