CN106603364A - Ethernet communication method for real-time transmission - Google Patents

Abstract

The present invention provides a kind of Ethernet communication method that can be used for real-time transmission, and this Ethernet comprises a plurality of nodes that are equal and have mutual communication connections, each node has a data link layer for data transmission, and the data it transmits includes Time-triggered data and event-triggered data are characterized in that a session layer is set above the data link layer for data transmission coordination between nodes during the data transmission process, and the session layer divides the communication time into duration Equal and cyclically repeated communication loops, each communication loop includes a static segment and a dynamic segment set in sequence, the static segment consists of multiple time slots with equal duration and different numbers, used for time-triggered data transmission , the dynamic segment is used for event-triggered data transmission according to priority, wherein each time slot corresponds to a node or a time-triggered data transmission task.

Description

An Ethernet Communication Method Applicable to Real-time Transmission

technical field

The invention relates to an Ethernet communication method, in particular to an Ethernet communication method which can be used for real-time transmission.

Background technique

Ethernet is currently the most widely used LAN communication technology. After more than 40 years of development, its transmission medium has been continuously improved, and its transmission rate and efficiency have been greatly improved. As the Metro Ethernet Forum (MEF) continues to widely apply Ethernet technology as a switching technology and transmission technology to the construction of MANs, Ethernet is not limited to LAN applications, but can be more widely used in MANs. (MAN) and Wide Area Network (WAN) domains.

The existing Ethernet data transmission mostly adopts the CSMA/CD media access control mechanism, and the transmission conflict between nodes is processed by the BEB algorithm, which has the defect of queuing delay, which makes it unable to be effectively used in industrial control. Therefore, the field bus technology that can better realize real-time and deterministic communication, or the comprehensive control network combining Ethernet and field bus, is still widely used in industrial control.

However, compared with fieldbus, Ethernet has the following advantages: (1) rich hardware and software resources, wide application, low cost; (2) high communication rate, faster than any current fieldbus; (3) Ethernet It supports multiple transmission media, supports bus and star topologies, and is easy to connect to the Internet, so it has strong scalability and can seamlessly integrate information from industrial control networks to realize remote monitoring, equipment management, software maintenance and Troubleshooting. Therefore, improving the communication mode of Ethernet, enabling Ethernet to realize real-time deterministic communication, and improving its real-time performance, determinism and communication reliability have become one of the urgent needs of Ethernet development.

Contents of the invention

In order to solve the above problems, a kind of Ethernet capable of realizing real-time communication is provided, and the present invention adopts the following technical solutions:

The present invention provides a kind of Ethernet communication method that can be used for real-time transmission, and this Ethernet comprises a plurality of nodes that are equal and have mutual communication connections, each node has a data link layer for data transmission, and the data it transmits Including time-triggered data and event-triggered data, it is characterized in that a session layer is set above the data link layer for data transmission coordination between nodes in the data transmission process, and the session layer divides the communication time into continuous A communication cycle with equal time and repeated cycles. Each communication cycle includes a static segment and a dynamic segment set in sequence. The static segment consists of multiple time slots with equal duration and different numbers, which are used for time-triggered data transmission. Transmission, the dynamic segment is used for event-triggered data transmission according to priority, where each time slot corresponds to a node or a time-triggered data transmission task, and the session layer is at least used to record the time slot number, start and end time, and each Nodes or data transmission tasks corresponding to time slots.

The Ethernet communication method that can be used for real-time transmission provided by the present invention can also have the following technical features: wherein, the dynamic segment is composed of a plurality of mini-slots with equal duration and different numbers, and each node has a different priority , when a node needs to transmit event-triggered data, the node with the highest priority occupies a certain number of mini-slots for event-triggered data transmission, and the session layer is also used to record and send and receive the number and start and end time of the mini-slot, The priority of the nodes and the queue of nodes that require event-triggered data transfers.

The Ethernet communication method that can be used for real-time transmission provided by the present invention can also have the following technical features: wherein, when a node completes an event-triggered data transmission, the node sends an end message through the session layer, allowing the next priority Nodes at the same level perform event-triggered data transmission.

The Ethernet communication method that can be used for real-time transmission provided by the present invention can also have the following technical features: wherein, the data transmission in the static segment adopts a predetermined fixed bandwidth, and the data transmission in the dynamic segment adopts a variable bandwidth.

The Ethernet communication method for real-time transmission provided by the present invention may also have the following technical features: wherein, the communication cycle further includes an idle segment set after the dynamic segment, and all nodes in the idle segment do not perform data transmission.

Invention function and effect

According to the Ethernet communication method that can be used for real-time transmission provided by the present invention, since a layer of session layer is added on the data link layer, the session layer divides the communication time into communication loops with equal duration and repeated cycles. Each cycle has a static segment, which includes a number of time slots with different numbers and one-to-one correspondence with nodes or transmission tasks, so that time-triggered communication between nodes can be performed and the completion of scheduled transmission tasks can be guaranteed, making Ethernet The time-deterministic communication is realized, and it can be applied in the network environment with real-time communication requirements.

Description of drawings

Fig. 1 is the structural representation of the Ethernet communication system that Ethernet communication method of the present invention adopts;

Fig. 2 is a structural schematic diagram of the communication cycle of the present invention;

Fig. 3 is a schematic structural diagram of a time slot and a mini-slot in the present invention.

detailed description

The specific implementation manners of the present invention will be described below in conjunction with the accompanying drawings.

The Ethernet communication system adopted by the Ethernet communication method of the present invention includes a plurality of nodes that are equal and have mutual communication connections.

FIG. 1 is a schematic structural diagram of an Ethernet communication system adopted by the Ethernet communication method of the present invention.

As shown in Figure 1, each node has an application layer, a transport layer, a network layer, a session layer, a data link layer, and a physical layer arranged from top to bottom. Among them, the settings and structures of the application layer, transport layer, network layer, data link layer and physical layer are the same as those of the usual Ethernet system. Among them, the application layer is the highest layer, which is the interactive interface between the user and the network, and is responsible for processing specific details of the network. The application layer can provide users with a variety of application protocols, such as HTTP, SMTP and FTP, etc. to provide end-user services; It is used for communication between Internet terminals and provides end-to-end communication for applications on multiple hosts. The network layer is also called the Internet layer, and its main functions are: logical addressing, data encapsulation, processing and transmission, routing, etc.

The data link layer mainly includes a logical link control sublayer (Logical Link Control, LLC) and a media access control sublayer (Media Access Control, MAC). Among them, the logical link control sublayer is used for receiving filtering, sending and receiving overload notification, and recovery management, and the media access control sublayer is used for data encapsulation/disassembly, frame encoding, media access management, etc. The session layer is located above the data link layer and is used for coordination and control in the process of data transmission between nodes. In addition, the physical layer acts as a transmission medium for bit encoding and decoding, bit timing, and synchronization.

Fig. 2 is a schematic structural diagram of the communication cycle of the present invention.

As shown in FIG. 2, the session layer of the present invention completes the coordination work in the communication process by dividing the communication time into communication cycles with equal duration and repeated cycles. Each communication cycle includes a static segment, a dynamic segment, and an idle segment set in sequence. The static segment is used for deterministic real-time communication, and its data transmission adopts a preset predetermined bandwidth; the dynamic segment is used for event-triggered data transmission. Its data transmission uses variable bandwidth. The idle segment is the end stage of the communication cycle, in which the network is in an idle mode, and each node does not transmit data. During system configuration, the time between each node is synchronized in advance, so the start moment of each communication cycle is derived from a trigger signal of a synchronous time base.

Fig. 3 is a schematic structural diagram of a time slot and a mini-slot in the present invention.

As shown in Figure 3, the static segment is divided into n time slots (that is, slots) with the same duration, and the numbers of these time slots are different, so the number of each time slot is unique, that is, these time slots Sorted by time, numbered from slot 1 to slot n. Moreover, the duration, start time and end time of each time slot are all set during system configuration; when using dual-channel mode communication, the time slot format (number, duration, start and end time) on the two channels ) is also exactly the same. Each time slot corresponds to a node or data transmission task that needs to be transmitted regularly, and the corresponding relationship is realized by one-to-one correspondence between the number of the node or task and the number of the time slot. For example, when a node has a need for timing transmission, it is allocated a time slot with a certain number during system configuration, and the session layer of the node allows it to start timing data transmission at the beginning of the time slot. And let it stop transmitting at the end of the time slot.

Among them, the session layer records the number of these time slots, the start and end time, and the corresponding node or task number, so that the nodes that need to perform scheduled transmission and the nodes required for the scheduled transmission task can perform data transmission in their corresponding time slots.

As shown in Figure 3, the dynamic segment is divided into multiple mini-slots of the same duration, and these mini-slots also have different numbers. In this embodiment, the mini-slots are numbered continuously according to the slot numbers of the same communication cycle, that is, the mini-slots are numbered n+1, n+2, n+3, . . . , n+x. When a node needs to perform event-triggered data transmission, the node sends a message requesting data transmission to the network, and records its number into the event-triggered data transmission queue. Different nodes have different priorities, which are also assigned to each node during system configuration and recorded in the session layer.

When a node has the highest priority in the event-triggered data transmission queue, the node will occupy a certain number of mini-slots and use these mini-slots as dynamic time slots for event-triggered data transmission. The corresponding dynamic segment data frame. The end of each dynamic segment data frame includes an end-of-frame identifier, allowing the session layer of other nodes to receive the information sent by the node, so that the next priority node continues to occupy a certain number of mini-slots after this mini-slot. to transfer.

Among them, the session layer also records the numbers of these mini-slots, the start and end times, the node queues that need to perform event-triggered data transmission, and the priority of each node. Let the nodes that need to perform timing transmission and the nodes required for timing transmission tasks perform data transmission in their corresponding time slots.

Function and effect of embodiment

According to the Ethernet communication method that can be used for real-time transmission provided by this embodiment, since a layer of session layer is added on the data link layer, the session layer divides the communication time into communication loops with equal duration and repeated cycles, each Each communication cycle has a static segment, which includes multiple time slots with different numbers and one-to-one correspondence with nodes or transmission tasks, so that time-triggered communication between nodes is possible and the completion of scheduled transmission tasks is guaranteed, making Ethernet The network realizes time-deterministic communication and can be applied to network environments with real-time communication requirements.

In addition, since the dynamic segment can also be divided into multiple mini-slots with the same duration through the session layer, the nodes can occupy a certain number of mini-slots according to the priority for event-triggered data transmission, and the priority of the node and Corresponding event-triggered data transmission can be sent, received and recorded through the session layer, so the Ethernet communication method that can be used for real-time transmission in this embodiment can also realize event-triggered communication according to priority at the same time, so that the present embodiment The Ethernet involved is deterministic, fault-tolerant, and strong real-time.

Claims (5)

1. An Ethernet communication method that can be used for real-time transmission, the Ethernet includes a plurality of nodes that are equal and have mutual communication connections, each node has a data link layer for data transmission, and the data it transmits includes time Triggered data and event-triggered data, characterized by: setting a session layer above the data link layer for data transmission coordination between the nodes during the data transmission process, The session layer divides the communication time into communication cycles with equal duration and repeated cycles, each of which includes a static segment and a dynamic segment set in sequence, The static segment is composed of a plurality of time slots with equal duration and different numbers, and is used for the transmission of the time-triggered data, The dynamic segment is used to transmit the event-triggered data according to the priority, Wherein, each time slot corresponds to a node or a time-triggered data transmission task, The session layer is at least used to record the time slot number, start and end time, and the node or data transmission task corresponding to each time slot. 2. the Ethernet communication method that can be used for real-time transmission according to claim 1, is characterized in that: Wherein, the dynamic segment is composed of a plurality of mini-slots with equal duration and different numbers, Each of the nodes has a different priority. When the nodes need to transmit event-triggered data, the node with the highest priority occupies a certain number of mini-slots to transmit the event-triggered data. transmission, The session layer is also used to record and send and receive the number and start and end time of the mini-slot, the priority of the node, and the queue of nodes that need to perform the event-triggered data transmission. 3. the Ethernet communication method that can be used for real-time transmission according to claim 2, is characterized in that: Wherein, when one of the nodes completes an event-triggered data transmission, the node sends an end message through the session layer to allow the next priority node to perform event-triggered data transmission. 4. the Ethernet communication method that can be used for real-time transmission according to claim 1, is characterized in that: Wherein, the data transmission in the static segment adopts a predetermined fixed bandwidth, Data transmission within the dynamic segment employs a variable bandwidth. 5. the Ethernet communication method that can be used for real-time transmission according to claim 1, is characterized in that: Wherein, the communication cycle further includes an idle segment set after the dynamic segment, and all the nodes in the idle segment do not perform the data transmission.