Ring Network

Abstract

To provide a ring network that can provide efficient and stable communication.SOLUTION: A ring network according to an embodiment includes a plurality of communication devices. Each of the plurality of communication devices includes: a first Ethernet interface connected to an adjacent communication device on one side and a second Ethernet interface connected to an adjacent communication device on the other side; and a host device that can transmit and receive data to and from other communication devices in the plurality of communication devices using the first Ethernet interface and the second Ethernet interface. The plurality of communication devices include a first communication device. The first communication device is configured to transmit, in a first time period, a first frame from its second Ethernet interface in a clockwise direction and a second frame from its first Ethernet interface in a counterclockwise direction.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The embodiment relates to a ring network. [Background technology]

[0002] 2. Description of the Related Art A network system (hereinafter referred to as a "ring network") in which a ring topology is constructed by a plurality of devices each having an Ethernet interface is known. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 7035877 Summary of the Invention [Problem to be solved by the invention]

[0004] To provide a ring network capable of realizing efficient and stable communication. [Means for solving the problem]

[0005] The ring network of an embodiment includes a plurality of communication devices. Each of the plurality of communication devices has a first Ethernet interface connected to an adjacent communication device on one side, a second Ethernet interface connected to an adjacent communication device on the other side, and a host device capable of transmitting and receiving data to and from other communication devices on the ring network using the first Ethernet interface and the second Ethernet interface. The plurality of communication devices includes a first communication device. The first communication device transmits a first frame from its second Ethernet interface in a clockwise direction and a second frame from its first Ethernet interface in a counterclockwise direction within a first period. [Brief explanation of the drawings]

[0006] [Figure 1] FIG. 1 is a schematic diagram showing an example of the overall configuration of a ring network according to a first embodiment. [Figure 2] FIG. 2 is a block diagram showing an example of the hardware configuration of the communication device according to the first embodiment. [Figure 3] FIG. 2 is a block diagram showing an example of the functional configuration of the communication device according to the first embodiment. [Figure 4] 6 is a flowchart showing an example of a route information collection operation in the ring network according to the first embodiment. [Figure 5] FIG. 2 is a schematic diagram showing an example of the configuration of a route search frame generated by the communication device according to the first embodiment. [Figure 6] FIG. 3 is a schematic diagram showing a specific example of a path information collection operation in the ring network according to the first embodiment. [Figure 7] 4 is a table showing an example of the format of a route information table generated by the communication device according to the first embodiment. [Figure 8] FIG. 2 is a schematic diagram showing an example of a GCL setting used in the ring network according to the first embodiment. [Figure 9] 6 is a flowchart showing an example of a transfer path determination operation in the ring network according to the first embodiment. [Figure 10] FIG. 10 is a block diagram showing an example of the functional configuration of a communication device according to a second embodiment. [Figure 11] 10 is a flowchart showing an example of an abnormality determination operation in a ring network according to the second embodiment. [Figure 12] FIG. 10 is a schematic diagram showing a first example of an abnormality that occurs in the ring network according to the second embodiment. [Figure 13] 10 is a table showing an example of the configuration of a route information table generated in response to a first example of an abnormality that has occurred in a ring network according to the second embodiment. [Figure 14] FIG. 10 is a schematic diagram showing a second example of an abnormality that occurs in the ring network according to the second embodiment. [Figure 15] 10 is a table showing an example of the configuration of a route information table generated in response to a second example of an abnormality that has occurred in the ring network according to the second embodiment. [Figure 16] FIG. 10 is a schematic diagram showing a third example of an abnormality that occurs in the ring network according to the second embodiment. [Figure 17] 10 is a table showing an example of the configuration of a route information table generated in response to a third example of an abnormality that has occurred in the ring network according to the second embodiment. [Figure 18] FIG. 10 is a schematic diagram showing a fourth example of an abnormality that occurs in the ring network according to the second embodiment. [Figure 19] 10 is a table showing an example of the configuration of a route information table generated in response to a fourth example of an abnormality that has occurred in the ring network according to the second embodiment. [Figure 20] FIG. 10 is a schematic diagram showing a fifth example of an abnormality that occurs in the ring network according to the second embodiment. [Figure 21] 10 is a table showing an example of the configuration of a route information table generated in response to a fifth example of an abnormality that has occurred in the ring network according to the second embodiment. [Figure 22] FIG. 11 is a schematic diagram showing an example of the configuration of a ring network according to a third embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0007] Each embodiment will be described below with reference to the drawings. Each embodiment illustrates an apparatus or method for embodying the technical idea of ​​the invention. The drawings are schematic or conceptual. Illustration of the configuration is omitted as appropriate. In this specification, components having substantially the same function and configuration are assigned the same reference numerals. Numbers and letters added to the reference numerals are used to refer to the same reference numerals and to distinguish between similar elements.

[0008] <1> First embodiment In the ring network 1 according to the first embodiment, each communication device 10 acquires communication path information by circulating a frame for acquiring the communication path information. Then, each communication device 10 determines the traffic transmission direction based on the acquired communication path information. The ring network 1 according to the first embodiment will be described in detail below.

[0009] <1-1> Configuration First, the configuration of the ring network 1 according to the first embodiment will be described.

[0010] <1-1-1> Overall configuration of ring network 1 FIG. 1 is a schematic diagram showing an example of the overall configuration of a ring network 1 according to the first embodiment. As shown in FIG. 1, the ring network 1 includes a plurality of communication devices 10 connected in a ring shape. In this specification, a ring network constructed with eight communication devices 10A, 10B, 10C, 10D, 10E, 10F, 10G, and 10H will be described as an example. Ethernet (registered trademark) is a type of computer network standard.

[0011] Each communication device 10 has two Ethernet interfaces (Ethernet I / F) ETH0 and ETH1. The Ethernet interfaces ETH0 and ETH1 have different MAC addresses. The eight communication devices 10A to 10H are connected in a ring network via the Ethernet interfaces ETH. Specifically, ETH1 of the communication device 10A is connected to ETH0 of the communication device 10B, ETH1 of the communication device 10B is connected to ETH0 of the communication device 10C, ..., ETH1 of the communication device 10G is connected to ETH0 of the communication device 10H, and ETH1 of the communication device 10H is connected to ETH0 of the communication device 10A. In this specification, two communication devices 10 connected without passing through another communication device 10 are referred to as "adjacent communication devices 10." In the ring network 1, any Ethernet frame transmitted from any communication device 10 is simply referred to as a "frame."

[0012] In the ring network 1, frames are transferred in a clockwise direction (CW) or counterclockwise direction (CCW) via one of the Ethernet interfaces ETH of the source communication device 10. When a frame transmitted from one of the ETHs of the source communication device is received by the other ETH of the source communication device 10, the source communication device 10 drops the received frame. The source communication device 10 determines whether the frame was transmitted by its own Ethernet interface ETH by referencing the source MAC address in the frame. This allows the ring network 1 to prevent the same frame from circulating multiple times on the ring network 1.

[0013] In the ring network 1 in this specification, communication between adjacent communication devices 10 via the Ethernet interface ETH is performed in accordance with IEEE802. 1st rule The transfer of frames between adjacent communication devices 10 is performed at the MAC (Media Access Control) layer. That is, each communication device 10 on the ring network 1 has an LSI (Large Scale Integration) capable of performing MAC layer processing.

[0014] In the ring network 1 in this specification, the same time is shared among all communication devices 10. That is, in each embodiment described below, it is assumed that clock synchronization is complete among all communication devices 10. The method of clock synchronization among multiple communication devices 10 complies with, for example, IEEE802.1AS-2020 (Timing and Synchronization). IEEE802.1AS-2020 specifies a protocol for accurately synchronizing clocks for systems that communicate using Ethernet. IEEE802.1AS-2020 enables multiple communication devices 10 to recognize and share the same time. Furthermore, the ring network 1 in this specification complies with TSN (Time Sensitive Networking). TSN is a group of network standards that guarantees time synchronization in data communication and ensures real-time performance.

[0015] In the ring network 1 described herein, frames transmitted by a source communication device 10 are transmitted from the corresponding Ethernet interface ETH in accordance with a GCL (Gate Control List). The GCL is a transmission schedule assigned to each communication device 10. The GCL is shared by all Ethernet interfaces ETH on the ring network 1. In other words, the same GCL is set in advance in the MAC layer of each communication device 10. The method for setting the GCL complies with, for example, IEEE802.1Qbv-2015 (Enhancements for Scheduled Traffic). IEEE802.1Qbv-2015 specifies that traffic with different priorities be transmitted based on a schedule (GCL). IEEE802.1Qbv-2015 allows each communication device 10 to transmit low-priority frames without guarantee (best effort) while transmitting high-priority frames with low latency.

[0016] <1-1-2> Hardware configuration of communication device 10 2 is a block diagram showing an example of a hardware configuration of the communication device 10 according to the first embodiment. As shown in FIG. 2, the communication device 10 includes, for example, a host device 20 and a communication IC 30. The host device 20 and the communication IC 30 are configured to be able to communicate with each other. The connection between the host device 20 and the communication IC 30 may be, for example, SAS (serial attached SCSI (small computer system interface)), SATA (serial ATA (advanced technology attachment)), PCIe TM (peripheral component interconnect express).

[0017] The host device 20 is a device that handles traffic communicated over the ring network 1. The host device 20 may include a camera, a sensor, a communication module, a central processing unit, etc. For example, in the ring network 1, different functions are assigned to the host device 20 of each communication device 10. The host device 20 includes, for example, a CPU (Central Processing Unit) 21, a ROM (Read Only Memory) 22, a RAM (Random Access Memory) 23, a function unit 24, and a hardware interface (I / F) 25.

[0018] The CPU 21 is an integrated circuit capable of executing various programs. The CPU 21 controls the overall operation of the host device 20. The ROM 22 is a non-volatile semiconductor memory. The ROM 22 stores programs and control data for controlling the host device 20. The RAM 23 is, for example, a volatile semiconductor memory. The RAM 23 is used as a working area for the CPU 21. The functional unit 24 is configured to realize functions assigned to the communication device 10. A different device can be assigned as the functional unit 24 for each communication device 10. The hardware I / F 25 is a circuit used to send and receive data (traffic) to and from the communication IC 30.

[0019] The communication IC 30 is an LSI having a function of transmitting and receiving traffic in each communication device 10. The communication IC 30 transmits traffic received from the host device 20 to another communication device 10. The communication IC 30 transfers traffic received from an adjacent communication device 10 addressed to another communication device 10 on one side to the adjacent communication device 10 on the other side. The communication IC 30 transmits traffic received from another communication device 10 addressed to itself to the host device 20. The communication IC 30 has, for example, a CPU 31, a ROM 32, a RAM 33, a hardware interface (I / F) 34, an Ethernet interface (I / F) 35, and an Ethernet interface (I / F) 36.

[0020] The CPU 31 is an integrated circuit capable of executing various programs. The CPU 31 controls the overall operation of the communication IC 30. The ROM 32 is a non-volatile semiconductor memory. The ROM 32 stores programs and control data for controlling the communication IC 30. The RAM 33 is, for example, a volatile semiconductor memory. The RAM 33 is used as a working area for the CPU 31. The hardware I / F 34 is a circuit used to send and receive data to and from the host device 20. That is, the hardware I / F 34 of the communication IC 30 is connected to the hardware I / F 25 of the host device 20.

[0021] Each of the Ethernet I / Fs 35 and 36 is a network interface used for communication between the communication devices 10 in the ring network 1. The Ethernet I / Fs 35 and 36 correspond to the Ethernet interfaces ETH0 and ETH1, respectively, described using FIG. 1. That is, the Ethernet I / F 35 is connected to ETH1 of the adjacent communication device 10 on one side. The Ethernet I / F 36 is connected to ETH0 of the adjacent communication device 10 on the other side. Different MAC addresses are assigned to the Ethernet I / Fs 35 and 36. In the ring network 1, the MAC address assigned to each Ethernet I / F is a unique address.

[0022] <1-1-3> Functional configuration of the communication device 10 3 is a block diagram showing an example of the functional configuration of the communication device 10 according to the first embodiment. As shown in FIG. 3, the host device 20 functions as a computer including, for example, a data transmitter / receiver 201, a time synchronizer 202, a route information collector 203, and a transfer route switcher 204. The communication IC 30 functions as a computer including a data transmitter / receiver 301 and signal processors 302 and 303. The data transmitter / receivers 201 and 301 are functional blocks corresponding to the hardware I / Fs 25 and 34, respectively. The time synchronizer 202, the route information collector 203, and the transfer route switcher 204 are functional blocks mainly realized by the CPU 21. The signal processors 302 and 303 are functional blocks corresponding to the Ethernet interfaces ETH0 and EHT1, respectively.

[0023] In the communication device 10, traffic (data) between the host device 20 and the communication IC 30 is communicated via data transmitter / receiver units 201 and 301. The time synchronization unit 202 of the host device 20 performs processing related to time synchronization within the ring network 1. The route information collection unit 203 collects route information from a route search frame RSF and updates the route information table RI based on the collected route information. The route search frame RSF is an Ethernet frame used to search for routes on the ring network 1 and collect information about each communication device 10. The route information table RI includes parameters related to communication routes within the ring network 1. The route information table RI is stored in, for example, RAM 23. When the host device 20 generates traffic for another communication device 10, the transfer route switching unit 204 determines the transfer route for the traffic based on the information written in the route information table RI.

[0024] Each of the signal processing units 302 and 303 of the communication IC 30 has a portion that functions as a MAC layer. Each of the signal processing units 302 and 303 generates a frame based on traffic received from the host device 20 or traffic received from other communication devices 10, and transmits the generated frame to an adjacent communication device 10. Each of the signal processing units 302 and 303 also forwards data included in a frame addressed to the communication device 10 to which it belongs or transmitted by broadcast to the host device 20. The same GCL is set in the MAC layer of each of the signal processing units 302 and 303. That is, based on a schedule specified by the same GCL within the ring network 1, the signal processing unit 302 (ETH0) transmits a frame to an adjacent communication device 10 on one side, and the signal processing unit 303 (ETH1) transmits a frame to an adjacent communication device 10 on the other side.

[0025] <1-2> Operation Next, the operation of the ring network 1 according to the first embodiment will be described. Each communication device 10 in the ring network 1 executes a route collection operation to update the route information table RI. Then, when transmitting traffic to another communication device 10, each communication device 10 in the ring network 1 executes a forwarding route determination operation to determine the traffic transmission route based on the updated route information table RI. Below, the route collection operation and the forwarding route determination operation will be described in detail in turn.

[0026] <1-2-1> Route information collection operation 4 is a flowchart showing an example of a route information collection operation in the ring network 1 according to the first embodiment. The flow of the route information collection operation in the ring network 1 according to the first embodiment will be described below with reference to FIG.

[0027] Each communication device 10 refers to the current time and the GCL, and when it confirms that it is the period allocated for transmitting its own route search frame RSF, it starts (starts) the series of processes shown in Fig. 4. Hereinafter, the period allocated for transmitting the route search frame RSF will also be referred to as a "transmission schedule."

[0028] First, the communication device 10 (source communication device 10) to which a transmission schedule is assigned simultaneously transmits a route search frame RSF in the counterclockwise direction CCW from the Ethernet interface ETH0 and in the clockwise direction CW from the Ethernet interface ETH1 (S10). At this time, the source communication device 10 specifies the MAC address owned by the Ethernet interface ETH used to transmit the route search frame RSF as the source MAC address, and specifies the MAC address owned by the other Ethernet interface ETH of the source communication device 10 as the destination MAC address. Note that the transmission timings of the route search frame RSF by the Ethernet interfaces ETH0 and ETH1 may be different, but are preferably approximately simultaneous. The route search frame RSF may be generated based on an instruction from the host device 20, or may be generated autonomously by the Ethernet interface ETH or the CPU 31 based on the GCL.

[0029] Then, the communication device 10 that receives the route search frame RSF (a communication device 10 other than the sender within the ring network 1) appends the MAC address and reception timestamp of the receiving Ethernet interface ETH and the MAC address and transmission timestamp of the sending Ethernet interface ETH to the route search frame RSF, and transfers the appended route search frame RSF to the next communication device 10 (S11). The transmission timestamp is a timestamp that indicates the time when the sending Ethernet interface ETH transmits the route search frame RSF. The reception timestamp is a timestamp that indicates the time when the receiving Ethernet interface ETH received the route search frame RSF.

[0030] Thereafter, the communication device 10 that is the source of the route search frame RSF receives the route search frame RSF transferred in the counterclockwise direction CCW and the route search frame RSF transferred in the clockwise direction CW, and updates the route information table RI based on the received route search frame RSF (S12). Specifically, in the communication device 10 that is the source of the route search frame RSF, information included in the route search frame RSF received by the Ethernet interface ETH of the communication IC 30 is transferred to the host device 20. Then, the route information collection unit 203 of the host device 20 calculates a transfer time corresponding to each MAC address based on the reception timestamp and transmission timestamp added by each communication device 10, and records the calculation result in the route information table RI. This "transfer time" is a time calculated, for example, by subtracting the transmission time of the route search frame RSF from the reception or transmission timestamp.

[0031] (1: Configuration of the route search frame RSF) Fig. 5 is a schematic diagram showing an example of the configuration of a route search frame RSF generated by the communication device 10 according to the first embodiment. As shown in Fig. 5, the route search frame RSF includes a preamble, an SFD (Start Frame Delimiter), a destination MAC address, a source MAC address, an Ethertype, a payload, and an FCS (Frame Check Sequence).

[0032] The preamble indicates the start position of the frame. The SFD is a specific bit string placed at the end of the preamble. The set of the preamble and SFD is added to the beginning of each unit of data transmission and reception in Ethernet. The destination MAC address indicates the MAC address of the destination of the frame. The source MAC address indicates the MAC address of the sender of the frame. The Ethertype indicates, for example, the protocol encapsulated in the payload of the frame. The route search frame RSF uses a unique Ethertype. For example, the Ethertype applied to the route search frame RSF is 0x88B6 (IEEE Std 802 - Local Experimental Ethertype) defined in IEEE 802 Numbers. The payload stores the data to be transmitted. The FCS is placed at the end of the frame and is data used to check whether the data contained in the received frame contains any errors.

[0033] Furthermore, the payload of the route search frame RSF may include multiple timestamp sets. The timestamp set is information that is added to the payload of the route search frame RSF when the route search frame RSF passes through one communication device 10. The timestamp set includes the MAC address and reception timestamp of the Ethernet interface ETH on the receiving side of the communication device 10 that forwards the route search frame RSF, and the MAC address and transmission timestamp of the Ethernet interface ETH on the transmitting side. Note that the number of timestamp sets included in the payload changes depending on the number of communication devices 10 that forward the route search frame RSF. Specifically, the number of timestamp sets included in the payload corresponds to the number of communication devices 10 through which the route search frame RSF transmitted from the source communication device 10 passes before returning to the source communication device 10 in the route information collection operation.

[0034] The reception timestamp and transmission timestamp inserted into the route search frame RSF may be the times when the route search frame RSF was received and transmitted during the previous route search operation. In this case, for example, the Ethernet interface ETH of each communication device 10 stores information about the route search frame RSF of the sender, and the reception timestamp and transmission timestamp. Then, when the Ethernet interface ETH of each communication device 10 receives a route search frame RSF from another communication device 10, it references the information about the sender and adds information about the reception timestamp and transmission timestamp of the route search frame RSF previously received from that sender to the payload of the route search frame RSF.

[0035] (2: Example of route search operation) Fig. 6 is a schematic diagram showing a specific example of a route information collection operation in the ring network 1 according to the first embodiment. In the example shown in Fig. 6, the communication device 10A corresponds to the communication device 10 that is the source of the route search frame RSF. Note that the following description will exemplify a case in which the communication device 10A is the communication device 10A that is the source of the route search frame RSF, but it is also possible for other communication devices 10 to perform the same operation as the communication device 10A.

[0036] When the communication device 10A starts a route search operation, the Ethernet interface ETH0 of the communication device 10A specifies the Ethernet interfaces ETH0 and ETH1 of the communication device 10A as the source and destination MAC addresses, respectively, and transmits a route search frame RSF in the counterclockwise direction CCW. Also, the Ethernet interface ETH1 of the communication device 10A specifies the Ethernet interfaces ETH1 and ETH0 of the communication device 10A as the source and destination MAC addresses, respectively, and transmits a route search frame RSF in the clockwise direction CW. The transmission timing of the route search frame RSF by the Ethernet interfaces ETH0 and ETH1 of the communication device 10A is, for example, simultaneous.

[0037] The payload of the route search frame RSF transmitted from the communication device 10A in the clockwise direction CW and counterclockwise direction CCW contains the MAC address and reception timestamp of the receiving Ethernet interface ETH of all communication devices 10 except for itself on the route of the ring network 1, and the MAC address and transmission timestamp of the transmitting Ethernet interface ETH. In this specification, the transmission timestamp and reception timestamp in the clockwise direction CW of the communication device 10i (i is any one of A to H) are respectively referred to as "T i,TX,CW " and "T i,RX,CW Similarly, the transmission timestamp and reception timestamp in the counterclockwise direction CCW in the communication device 10i are defined as "T i,TX,CCW " and "T i,RX,CCW " is defined as

[0038] Specifically, for example, when a route search frame RSF transmitted in the counterclockwise direction CCW passes through the communication device 10H, the communication device 10H adds the MAC address of the receiving Ethernet interface ETH1 and the reception timestamp T H,RX,CCW , the MAC address of the sending Ethernet interface ETH0, and the sending timestamp T H,TX,CCW For example, when a route search frame RSF transmitted in the clockwise direction CW passes through the communication device 10B, the communication device 10B adds the MAC address of the receiving Ethernet interface ETH0 and the reception timestamp T B,RX,CW , the MAC address of the sending Ethernet interface ETH1, and the sending timestamp T B,TX,CW Add the following in this order:

[0039] In this example, the route search frame RSF transmitted in the counterclockwise direction CCW is transferred in order through a plurality of communication devices 10H, 10G, 10F, 10E, 10D, 10C, and 10B arranged in the counterclockwise direction CCW, and is finally received by the Ethernet interface ETH1 of the communication device 10A. On the other hand, the route search frame RSF transmitted in the clockwise direction CW is transferred in order through a plurality of communication devices 10B, 10C, 10D, 10F, 10G, and 10H arranged in the clockwise direction CW, and is finally received by the Ethernet interface ETH0 of the communication device 10A. The communication device 10A then reads out information contained in the payload of the route search frame RSF that has circulated through the ring network 1 in the counterclockwise direction CCW and information contained in the payload of the route search frame RSF that has circulated through the ring network 1 in the clockwise direction CW. This allows the communication device 10A to obtain identification information (MAC addresses) and reception and transmission timestamp information for all communication devices 10 on the communication path in each of the clockwise direction CW and counterclockwise direction CCW, and to update the route information table RI.

[0040] (3: Configuration of routing information table RI) FIG. 7 is a table illustrating an example of the format of a route information table RI generated by the communication device 10 according to the first embodiment. FIG. 7 corresponds to the route information table RI generated by the communication device 10A. The communication device 10A can generate the route information table RI illustrated in FIG. 7 based on information contained in the payload of a route search frame RSF that has circulated around the ring network 1 in the clockwise direction (CW) and information contained in the payload of a route search frame RSF that has circulated around the ring network 1 in the counterclockwise direction (CCW). Note that, similar to the communication device 10A, other communication devices 10 can also generate route information tables RI that include information on the MAC addresses and timestamps of communication devices 10 other than itself. Hereinafter, the MAC address of the Ethernet interface ETH on the receiving side of the communication device 10i (where i is any one of A to H) will be referred to as “10i-ERX.” Furthermore, the MAC address of the Ethernet interface ETH on the transmitting side of the communication device 10i will be referred to as “10i-ETX.”

[0041] As shown in FIG. 7, the route information table RI of the communication device 10A stores information relating to the number of hops HN, MAC addresses, and transfer times relative to the communication device 10A, in association with each of the clockwise direction CW and counterclockwise direction CCW. The number of hops HN (Number of hops) is the number of transfer / relay facilities that must be passed through to reach the communication partner on the communication network. That is, in this specification, it corresponds to the number of communication devices 10 that must be passed through to reach the destination communication device 10 on the ring network 1. Also, in this specification, a bridge transfer between the Ethernet interfaces ETH0 and ETH1 of the same communication device 10 is also considered a hop.

[0042] First, the information associated with the clockwise CW will be described. HN=1 is associated with the MAC address 10B-ERX (ETH0 of the communication device 10B). HN=2 is associated with the MAC address 10B-ETX (ETH1 of the communication device 10B). HN=3 is associated with the MAC address 10C-ERX (ETH0 of the communication device 10C). The same applies to the correspondence between the other numbers. HN=12 is associated with the MAC address 10G-ETX (ETH1 of the communication device 10G). HN=13 is associated with the MAC address 10H-ERX (ETH0 of the communication device 10H). HN=14 is associated with the MAC address 10H-ETX (ETH1 of the communication device 10H). The transfer time in the clockwise CW is calculated from the difference between the reception or transmission timestamp and the transmission timestamp of ETH1 of the communication device 10A. Specifically, the transfer time associated with 10B-ERX in the clockwise direction (CW) is T B,RX,CW -T A,TX,CW The transfer time associated with 10B-ETX in the clockwise direction CW is T B,TX,CW -T A,TX,CW The transfer time associated with 10C-ERX in the clockwise direction (CW) is T C,RX,CW -T A,TX,CW The same applies to the other numbers. In the clockwise direction (CW), the transfer time associated with 10H-ETX is T H,TX,CW -T A,TX,CW It is calculated as follows.

[0043] Next, information associated with the counterclockwise direction CCW will be described. HN=1 is associated with MAC address 10H-ERX (ETH1 of the communication device 10H). HN=2 is associated with MAC address 10H-ETX (ETH0 of the communication device 10H). HN=3 is associated with MAC address 10G-ERX (ETH1 of the communication device 10G). ... HN=12 is associated with MAC address 10C-ETX (ETH0 of the communication device 10C). HN=13 is associated with MAC address 10B-ERX (ETH1 of the communication device 10B). HN=14 is associated with MAC address 10B-ETX (ETH0 of the communication device 10B). The transfer time in the counterclockwise direction CCW is calculated from the difference between the reception or transmission timestamp and the transmission timestamp of ETH0 of the communication device 10A. Specifically, the transfer time associated with 10H-ERX in the counterclockwise direction CCW is T H,RX,CCW -T A,TX,CCW The transfer time associated with 10H-ETX in the counterclockwise direction CCW is T H,TX,CCW -T A,TX,CCW The transfer time associated with 10G-ERX in the counterclockwise direction (CCW) is calculated as T G,RX,CCW -T A,TX,CCW … The transfer time associated with 10B-ETX in the counterclockwise direction CCW is T B,TX,CCW -T A,TX,CCW It is calculated as follows.

[0044] (4: GCL (Gate Control List) Settings) FIG. 8 is a schematic diagram showing an example of the setting of a GCL used in the ring network 1 according to the first embodiment. As shown in FIG. 8, a predetermined schedule period is set by the GCL. In the schedule period, a period (Open) in which traffic transmission is permitted and a period (Close) in which traffic transmission is prohibited are set for each traffic priority and traffic type. Permission and prohibition of traffic transmission can be set for each communication device 10. The period (transmittable period) in which traffic transmission is permitted is also called a slot. A slot is set, for example, in association with the transmission of a route search frame RSF in both directions (clockwise direction CW and counterclockwise direction CCW) of each communication device 10. Then, the route search frame RSF from each communication device 10 is transmitted in the associated slot.

[0045] In this example, eight slots are set corresponding to the eight communication devices 10A to 10H, respectively. Specifically, the schedule cycle includes service periods SP1 to SP8. In each service period SP, slots permitting traffic transmission are assigned to a high-priority frame HPF including high-priority traffic, a medium-priority frame MPF including medium-priority traffic, a low-priority frame LPF including low-priority traffic, and a route search frame RSF. In the slots assigned to the route search frame RSP in service period SP1, the source is set to only the communication device 10A. In the slots assigned to the route search frame RSP in service period SP2, the source is set to only the communication device 10B. The same applies to the other numerical correspondences. In the slots assigned to the route search frame RSP in service period SP8, the source is set to only the communication device 10H.

[0046] In slots allocated for transmitting route search frames RSF in each service period SP, route search frames RSF transmitted from one source circulate within the ring network 1. This allows multiple route search frames RSF transmitted from different communication devices 10 to be transmitted without contention within the slot and without disrupting other traffic. Furthermore, route search frames RSF are periodically transmitted from the Ethernet interfaces ETH of all communication devices 10 on the ring network 1 by repeating the schedule period. Therefore, in each communication device 10, the transfer time information for all communication devices 10 other than itself within the ring network 1 in the route information table RI is recalculated based on the latest timestamps by the process of S12 shown in FIG. 4.

[0047] 8 illustrates an example in which a slot for performing a route information collection operation is assigned to each communication device 10, but this is not limiting. In a slot assigned to the route search frame RSF, communication between multiple communication devices 10 may be permitted. In a slot assigned to the route search frame RSF, it is sufficient that communication contention within the slot can be suppressed. By permitting communication between multiple communication devices 10 in the slot, the ring network 1 can shorten the update period of the route information table RI.

[0048] <1-2-2> Transfer path determination operation 9 is a flowchart showing an example of a transfer route determination operation in the ring network according to the first embodiment. The flow of the transfer route determination operation in the ring network 1 according to the first embodiment will be described below with reference to FIG.

[0049] When transmitting traffic based on the GCL, each communication device 10 starts the series of processes shown in FIG. 9 (Start).

[0050] First, the communication device 10 refers to the route information table RI and determines whether "TTcw = TTccw" is satisfied (S20). TTcw is the time (transfer time) until the frame reaches the Ethernet interface ETH0 of the communication device 10, which is the destination of the traffic, when the frame is transmitted in the clockwise direction CW. TTccw is the time (transfer time) until the frame reaches the Ethernet interface ETH1 of the communication device 10, which is the destination of the traffic, when the frame is transmitted in the counterclockwise direction CCW.

[0051] In the process of S20, if "TTcw = TTccw" is not satisfied (S20: NO), the communication device 10 refers to the route information table RI and determines whether "TTcw < TTccw" is satisfied (S21).

[0052] In the process of S21, if "TTcw < TTccw" is satisfied (S21: YES), the communication device 10 determines the transfer direction of the frame to be the clockwise direction CW (S22) and ends the series of processes in FIG. 9 (end).

[0053] In the process of S21, if "TTcw < TTccw" is not satisfied (S21: NO), the communication device 10 determines the transfer direction of the frame to be the counterclockwise direction CCW (S23) and ends the series of processes in FIG. 9 (end).

[0054] In the process of S20, if "TTcw = TTccw" is satisfied (S20: YES), the communication device 10 refers to the route information table RI and determines whether "HNcw = HNccw" is satisfied (S24). HNCW is the number of hops HN until the frame reaches the Ethernet interface ETH0 of the communication device 10, which is the destination of the traffic, when the frame is transmitted in the clockwise direction CW. HNccw is the number of hops HN until the frame reaches the Ethernet interface ETH1 of the communication device 10, which is the destination of the traffic, when the frame is transmitted in the counterclockwise direction CCW.

[0055] In the process of S24, when "HNcw = HNccw" is satisfied (S24: YES), the communication device 10 determines the frame transfer direction to the clockwise direction CW (S25), and ends the series of processes in FIG. 9 (end).

[0056] In the process of S24, when "HNcw = HNccw" is not satisfied (S24: NO), the communication device 10 refers to the path information table RI and determines whether "HNcw < HNccw" is satisfied (S26).

[0057] In the process of S26, when "HNcw < HNccw" is satisfied (S26: YES), the communication device 10 determines the frame transfer direction to the clockwise direction CW (S27), and ends the series of processes in FIG. 9 (end).

[0058] In the process of S26, when "HNcw < HNccw" is not satisfied (S26: NO), the communication device 10 determines the frame transfer direction to the counterclockwise direction CCW (S28), and ends the series of processes in FIG. 9 (end).

[0059] As described above, when each communication device 10 transfers an arbitrary frame to another communication device 10 specified by the destination MAC address, it can determine the traffic transfer direction based on the path information table RI. Thereafter, each communication device 10 transmits the frame in the determined transfer direction.

[0060] Note that each communication device 10 transfers the frame received by one Ethernet interface ETH to either the host device 20 or another communication device 10 connected to the other Ethernet interface ETH based on the destination MAC address included in the header of the frame. When the traffic is a broadcast packet, the communication device 10 may transfer the frame received by one Ethernet interface ETH to both the host device 20 and another communication device 10 connected to the other Ethernet interface ETH.

[0061] In the above description, the case where the transfer direction is determined to be the clockwise direction CW when HNcw=HNccw in the process of S24 has been exemplified, but is not limited to this. When HNcw=HNccw, the transfer direction may be determined to be the counterclockwise direction CCW. The frame transfer direction when the transfer time and the number of hops are the same in the clockwise direction CW and the counterclockwise direction CCW can be designed arbitrarily.

[0062] <1-3> Effects of the first embodiment The ring network 1 according to the first embodiment can realize efficient and stable communication. The effects of the first embodiment will be described in detail below.

[0063] Ring networks consisting of multiple communication devices with Ethernet interfaces are known as network systems used in automobiles (vehicles), etc. In addition, as communication between multiple communication devices becomes more complex in ring networks, there is a demand for efficient and stable communication.

[0064] Therefore, each communication device 10 in the ring network 1 according to the first embodiment conforms to TSN and acquires information about routes within the ring network 1 using one type of dedicated Ethernet frame (route search frame RSF). Specifically, each communication device 10 transmits a route search frame RSP in both directions through a route information collection operation, and receives the bidirectional route search frame RSF that has circulated within the ring network 1. Then, each communication device 10 acquires, from the received bidirectional route search frame RSF, identification information (MAC address) of any communication device 10 on the ring network 1, the position to each communication device 10 (number of hops HN), and transfer time (reception and transmission timestamps), and records these in a route information table RI.

[0065] Each communication device 10 can perform route information collection operations without disrupting other communications through advanced traffic control using TSN. Furthermore, in the ring network 1, all communication devices 10 have the same time due to time synchronization. Therefore, each communication device 10 can calculate and compare transfer times between any points based on information acquired from the route search frame RSF circulating within the ring network 1.

[0066] In the ring network 1 according to the first embodiment, each communication device 10 determines an optimal transfer path based on the path information (MAC address / number of hops (number of relays) / transfer time) recorded in the path information table RI. Specifically, each communication device 10 compares the number of hops and transfer time in the MAC address of the Ethernet interface ETH on the receiving side of the destination communication device 10 in the clockwise direction CW with the number of hops and transfer time in the MAC address of the Ethernet interface ETH on the receiving side in the counterclockwise direction CCW. Then, each communication device 10 determines the communication path that has the shorter transfer time between the clockwise direction CW and the counterclockwise direction CCW.

[0067] As a result, each communication device 10 in the ring network 1 according to the first embodiment can determine a transfer route that can transfer traffic in the shortest time. Therefore, the ring network 1 according to the first embodiment can achieve efficient communication. Furthermore, when the transfer time is equal in both directions, each communication device determines the route with the fewer hops as the communication route. This allows the ring network 1 to reduce the number of communication devices 10 through which a frame passes, thereby achieving stable communication.

[0068] <2> Second embodiment Each communication device 10 in the ring network 1 according to the second embodiment determines whether or not there is a failure or delay on the ring network 1 based on the reception status of the route search frame RSF transmitted by itself and the reception status of the route search frame RSF transmitted from the other communication devices 10. Then, each communication device 10 in the ring network 1 according to the second embodiment determines the traffic transmission direction based on the state of the failure or delay. The ring network 1 according to the second embodiment will be described in detail below.

[0069] <2-1> Configuration The configuration of the ring network 1 according to the second embodiment is the same as that of the first embodiment, except for the functional configuration of the communication device 10.

[0070] (Functional configuration of communication device 10) FIG. 10 is a block diagram showing an example of the functional configuration of a communication device 10 according to the second embodiment. As shown in FIG. 10, in the communication device 10 according to the second embodiment, the host device 20 further includes an abnormality detection unit 205. The abnormality detection unit 205 refers to the route information table RI to detect whether a failure or delay has occurred in the ring network 1. If a failure or delay has occurred, the abnormality detection unit 205 identifies the location where the failure or delay has occurred. Furthermore, in the second embodiment, the route information table RI further records information indicating the forwarding status of frames for a corresponding MAC address.

[0071] The forwarding status of the route search frame RSF is expressed in three types, for example, "possible (forwarding possible)", "not possible (forwarding not possible)", and "delayed (forwarding delay)". A forwarding status of "possible" indicates that the communication device 10 that stores the route information table RI in question is able to send frames to the corresponding MAC address. A forwarding status of "not possible" indicates that the communication device 10 that stores the route information table RI in question is unable to send frames to the corresponding MAC address. A forwarding status of "delayed" indicates that the communication device 10 that stores the route information table RI in question is experiencing a delay in sending frames to the corresponding MAC address.

[0072] <2-2> Operation The ring network 1 according to the second embodiment transmits a route search frame RSF in the clockwise direction CW and counterclockwise direction CCW in the route information collection operation, and then executes an abnormality determination operation to determine whether there is a fault or delay on the ring network 1. The abnormality determination operation and the method for identifying the location of the abnormality in the second embodiment will be described below in order.

[0073] <2-2-1> Abnormality judgment operation 11 is a flowchart showing an example of an abnormality determination operation in the ring network according to the second embodiment. The flow of the abnormality determination operation in the ring network 1 according to the second embodiment will be described below with reference to FIG.

[0074] When the process of S10 of the route information collection operation is executed, the communication device 10 starts the abnormality determination operation (start).

[0075] First, the communication device 10 checks whether or not a route search frame RSF has been received in both directions (clockwise direction CW and counterclockwise direction CCW) within a timeout period (S30). The timeout period corresponds to a threshold value used to determine whether or not a failure has occurred on the ring network 1. An example of setting the timeout period will be described later.

[0076] In the process of S30, if a bidirectional route search frame RSF is received within the timeout period (S30: YES), the communication device 10 determines that no failure has occurred on the ring network 1. Then, the communication device 10 is configured to determine the frame forwarding direction based on the bidirectional forwarding time and the number of hops HN when transmitting future traffic (S31). This setting corresponds to the forwarding path determination operation described in the first embodiment. When the process of S31 is completed, the communication device 10 ends the series of processes in FIG. 11 (END).

[0077] In the process of S30, if a bidirectional route search frame RSF is not received within the timeout period (S30: NO), the communication device 10 determines that a failure or delay has occurred on the ring network 1. Then, the communication device 10 identifies the location of the failure or delay within the ring network 1 (i.e., the location of the abnormality) (S32).

[0078] When the process of S32 is completed and the location of the abnormality is identified, the communication device 10 is configured to determine the frame transfer direction taking into account the failure or delay when transmitting traffic in the future (S33). Specific examples of a method for identifying the location of the abnormality and a method for determining the frame transfer direction taking into account the failure or delay will be described later. When the process of S33 is completed, the communication device 10 ends the series of processes in FIG. 11 (END).

[0079] (Example of setting the timeout time) Here, an example of setting the timeout period will be described. In this setting example, a case will be described in which an n-th (n is an integer equal to or greater than 3) transmission of a route search frame RSF is started in both directions from an arbitrary communication device 10i. Hereinafter, the timeout period in the clockwise direction CW will be referred to as "Timeout i,CW " and the timeout period in the counterclockwise direction (CCW) is defined as "Timeout i,CCW "In the following formula, "dir" indicates either the clockwise direction CW or the counterclockwise direction CCW. i,TX,dir"(n)" indicates the time when the nth route search frame is transmitted from any communication device 10i. i,RX,dir (n)" indicates the time when the nth route search frame is received by any communication device 10i.

[0080] Timeout i,CW and Timeout i,CCW is shown in the following equation (1).

[0081]

number

[0082] μ included in Eq. (1) i,dir (n, m) are calculated using the following formula (2).

[0083]

number

[0084] σ included in Eq. (1) i,dir (n, m) are calculated using the following formula (3).

[0085]

number

[0086] As shown in equation (1), the timeout period is calculated by adding the moving average of the time required for the route search frame RSF to circulate on the ring network 1 from the (n-1-m)th time (m is a positive integer) to the (n-1)th time in the communication device 10i and three times its standard deviation. Therefore, when the communication device 10i transmits the route search frame RSF, the timeout period is calculated by adding the moving average of the time required for the route search frame RSF to circulate on the ring network 1 from the (n-1-m)th time (m is a positive integer) to the (n-1)th time in the communication device 10i. i,TX,dir (n)+Timeout i,dir Based on the fact that the route search frame RSF arrives at the receiving-side Ethernet interface ETH of the communication device 10i within "10.5.5", it can be determined that no failure has occurred on the ring network 1.

[0087] <2-2-2> How to identify the location of the abnormality Next, a method for identifying the location of an abnormality in the ring network 1 according to the second embodiment will be described. Any communication device 10i determines that a failure has occurred on the ring network 1 when a route search frame RSF transmitted by itself does not arrive at its own receiving Ethernet interface ETH before a timeout period has elapsed. Then, in the ring network 1 according to the second embodiment, each communication device 10 can identify the location of an abnormality (failure or delay) on the ring network 1 by analyzing the reception status of the route search frame RSF transmitted from the other communication devices 10. Then, each communication device 10 according to the second embodiment can determine the communication route of traffic according to the occurrence status of failures and delays on the ring network 1.

[0088] Below, first to fifth examples will be described as specific examples of abnormalities (failures or delays) that occur on the ring network 1, and their detection methods.

[0089] (Example 1) FIG. 12 is a schematic diagram showing a first example of an abnormality that occurs in the ring network 1 according to the second embodiment. The first example corresponds to a case where the line between two adjacent communication devices 10 is disconnected. FIG. 12 illustrates a case where the line between communication devices 10D and 10E is disconnected, causing a failure. The following describes a method by which the communication device 10A identifies the location of the abnormality shown in FIG. 12. The communication device 10A can estimate the location of the failure based on the reception status of route search frames RSF transmitted from other communication devices 10 in the clockwise direction CW and the counterclockwise direction CCW, and the route information table RI.

[0090] First, a method of determining whether or not a route search frame RSF transmitted from an arbitrary communication device 10i has reached the communication device 10A will be described. A,dir" If the following equation (4) is satisfied, the communication device 10A determines that the route search frame RSF transmitted from any communication device 10i in the direction indicated by "dir" has not reached the communication device 10A. Note that the method of checking whether the route search frame RSF has reached using equation (4) can also be used in the second to fifth examples described below.

[0091]

number

[0092] μ included in Eq. (4) i,A,dir (n, m) are calculated using the following equation (5).

[0093]

number

[0094] σ included in Eq. (4) i,A,dir (n, m) are calculated using the following equation (6).

[0095]

number

[0096] When the line between the communication devices 10D and 10E is disconnected, the communication device 10A can receive, in the clockwise direction CW, a route search frame RSF transmitted from each of the communication devices 10E to 10H, but cannot receive a route search frame RSF transmitted from each of the communication devices 10B to 10D. Also, in the counterclockwise direction CW, the communication device 10A can receive, in the counterclockwise direction CW, a route search frame RSF transmitted from each of the communication devices 10B to 10D, but cannot receive a route search frame RSF transmitted from each of the communication devices 10E to 10H.

[0097] Then, the communication device 10A updates the route information table RI based on the reception status of the route information table RI from the other communication devices 10. An example of the configuration of the route information table RI in the first example is shown in FIG. 13. As shown in FIG. 13, in this example, in the clockwise direction CW, "transfer possible" is recorded in association with the ETH MAC addresses of the transmitting and receiving sides of each of the communication devices 10B to 10D. In the clockwise direction CW, "transfer impossible" is recorded in association with the ETH MAC addresses of the transmitting and receiving sides of each of the communication devices 10E to 10H. In addition, in the counterclockwise direction CCW, "transfer possible" is recorded in association with the ETH MAC addresses of the transmitting and receiving sides of each of the communication devices 10H to 10E. In the counterclockwise direction CCW, "transfer impossible" is recorded in association with the ETH MAC addresses of the transmitting and receiving sides of each of the communication devices 10B to 10D.

[0098] Based on the updated route information table RI and the arrival status of the route search frame RSF from the other communication device 10, the communication device 10A can infer that a failure has occurred between the communication devices 10D and 10E in the clockwise direction CW, and that a failure has occurred between the communication devices 10E and 10D in the counterclockwise direction CCW. In other words, the communication device 10A can infer that a failure has occurred in the two-way communication between the communication devices 10D and 10E.

[0099] Furthermore, the communication device 10A can determine the optimal transfer path for a frame based on the updated route information table RI. For example, when traffic to the communication device 10D occurs, the communication device 10A determines the transfer direction of the frame to the communication device 10D to be the clockwise direction (CW), which can avoid the failure point, regardless of the transfer time or the number of hops. Similarly, when traffic to the communication device 10E occurs, the communication device 10A determines the transfer direction of the frame to the communication device 10E to be the counterclockwise direction (CCW), which can avoid the failure point, regardless of the transfer time or the number of hops.

[0100] (Example 2) FIG. 14 is a schematic diagram showing a second example of an abnormality that occurs in the ring network 1 according to the second embodiment. The second example corresponds to a case where frames cannot be transferred in only one direction between two adjacent communication devices 10. FIG. 14 illustrates a case where a failure occurs in communication from communication device 10E to communication device 10D. A method for communication device 10A to identify the location of the abnormality shown in FIG. 14 will be described below.

[0101] When a failure occurs in communication from the communication device 10E to the communication device 10D, the communication device 10A can receive a route search frame RSF transmitted from each of the communication devices 10B to 10H in the clockwise direction CW. That is, in this example, all of the communication devices 10 can forward frames as usual in the clockwise direction CW. On the other hand, the communication device 10A can receive a route search frame RSF transmitted from each of the communication devices 10E to 10H in the counterclockwise direction CW, but cannot receive a route search frame RSF transmitted from each of the communication devices 10B to 10D.

[0102] Then, the communication device 10A updates the route information table RI based on the reception status of the route information table RI from the other communication devices 10. An example of the configuration of the route information table RI in the second example is shown in FIG. 15. As shown in FIG. 15, in this example, in the clockwise direction CW, "transfer possible" is recorded in association with the MAC addresses of the ETHs on the transmitting and receiving sides of all of the communication devices 10B to 10H except for itself. Also, in the counterclockwise direction CCW, "transfer possible" is recorded in association with the MAC addresses of the ETHs on the transmitting and receiving sides of the communication devices 10H to 10E. In the counterclockwise direction CCW, "transfer impossible" is recorded in association with the MAC addresses of the ETHs on the transmitting and receiving sides of the communication devices 10B to 10D.

[0103] Based on the updated route information table RI, the communication device 10A can infer that a failure has occurred only in the counterclockwise direction CCW between the communication devices 10E and 10D.

[0104] Furthermore, the communication device 10A can determine the optimal forwarding path for the frame based on the updated route information table RI. For example, when traffic to the communication device 10D occurs, the communication device 10A determines the forwarding path for the frame to the communication device 10D by the forwarding path determination operation described in the first embodiment. After that, when the determined forwarding path includes the detected failure point, the communication device 10A changes the forwarding path to the clockwise direction CW, taking the failure point into consideration.

[0105] (Example 3) FIG. 16 is a schematic diagram showing a third example of an abnormality that has occurred in the ring network 1 according to the second embodiment. The third example corresponds to a case where frames cannot be transferred between the Ethernet interfaces ETH0 and ETH1 in a certain communication device 10 (i.e., a case where bridge transfer is not possible within the communication device 10). FIG. 16 illustrates a case where a failure has occurred between ETH0 and ETH1 in a communication device 10D. However, in this example, it is assumed that data can be transferred normally between each Ethernet interface ETH and the host device 20 in the communication device 10D. A method for the communication device 10A to identify the location of the abnormality shown in FIG. 16 will be described below.

[0106] When a failure occurs between ETH0 and ETH1 in the communication device 10D, the communication device 10A can receive, in the clockwise direction CW, a route search frame RSF transmitted from each of the communication devices 10D to 10H, but cannot receive a route search frame RSF transmitted from each of the communication devices 10B and 10C. Furthermore, the communication device 10A can receive, in the counterclockwise direction CW, a route search frame RSF transmitted from each of the communication devices 10B to 10D, but cannot receive a route search frame RSF transmitted from each of the communication devices 10E to 10H.

[0107] Then, the communication device 10A updates the route information table RI based on the reception status of the route information table RI from the other communication devices 10. An example of the configuration of the route information table RI in the third example is shown in FIG. 17. As shown in FIG. 17, in this example, in the clockwise direction CW, "transfer possible" is recorded in association with the ETH MAC addresses of the transmitting and receiving sides of the communication devices 10B and 10C, respectively, and the ETH MAC address of the receiving side of the communication device 10D. In the clockwise direction CW, "transfer impossible" is recorded in association with the ETH MAC address of the transmitting side of the communication device 10D, and the ETH MAC addresses of the transmitting and receiving sides of the communication devices 10E to 10H. Furthermore, in the counterclockwise direction CCW, "transfer possible" is recorded in association with the ETH MAC addresses of the transmitting and receiving sides of the communication devices 10H to 10E, respectively, and the ETH MAC address of the receiving side of the communication device 10D. In the counterclockwise direction CCW, the transfer not possible is recorded in association with the ETH MAC address of the sender of the communication device 10D and the ETH MAC addresses of the sender and receiver of the communication devices 10B and 10C.

[0108] Based on the updated route information table RI, the communication device 10A can infer that a failure has occurred between the communication devices 10C and 10E in the clockwise direction CW, and that a failure has occurred between the communication devices 10C and 10E in the counterclockwise direction CCW. Furthermore, because the communication device 10A can receive the route search frame RSF transmitted from the communication device 10D in both directions, it can also infer that the connections between the communication devices 10C and 10D, and between the communication devices 10D and 10E, are normal. From the above, the communication device 10A can infer that bridge forwarding between the Ethernet interfaces ETH0 and ETH1 in the communication device 10D is not being performed normally.

[0109] Furthermore, the communication device 10A can determine the optimal forwarding path for a frame based on the updated route information table RI. For example, when traffic to the communication device 10D occurs, the communication device 10A determines the forwarding path for the frame to the communication device 10D by the forwarding path determination operation described in the first embodiment, because the communication device 10D does not need to consider this failure in forwarding frames. On the other hand, the communication device 10A first determines the forwarding path for the frame to another communication device in which no failure has occurred by the forwarding path determination operation described in the first embodiment. Thereafter, if the determined forwarding path includes the failure point (communication device 10D), the communication device 10A changes the forwarding path to one that does not include the failure point and forwards the frame.

[0110] (Example 4) FIG. 18 is a schematic diagram showing a fourth example of an abnormality that has occurred in the ring network 1 according to the second embodiment. The fourth example corresponds to a case where the internal operation of a certain communication device 10 is not functioning normally. FIG. 18 illustrates a case where the internal operation of a communication device 10D is not functioning normally. However, in this example, it is assumed that each Ethernet interface ETH of the communication device 10D is normally connected to the Ethernet interface ETH of an adjacent communication device 10. A method for the communication device 10A to identify the location of the abnormality shown in FIG. 18 will be described below.

[0111] When the internal operation of the communication device 10D is not functioning normally, the communication device 10A can receive, in the clockwise direction CW, a route search frame RSF transmitted from each of the communication devices 10E to 10H, but cannot receive a route search frame RSF transmitted from each of the communication devices 10B to 10D. Furthermore, the communication device 10A can receive, in the counterclockwise direction CW, a route search frame RSF transmitted from each of the communication devices 10B and 10C, but cannot receive a route search frame RSF transmitted from each of the communication devices 10D to 10H.

[0112] Then, the communication device 10A updates the route information table RI based on the reception status of the route information table RI from the other communication devices 10. An example of the configuration of the route information table RI in the fourth example is shown in FIG. 19. As shown in FIG. 19, in this example, in the clockwise direction CW, "transfer possible" is recorded in association with the MAC addresses of the ETHs on the transmitting and receiving sides of the communication devices 10B and 10C, respectively. Also, in the clockwise direction CW, "transfer impossible" is recorded in association with the MAC addresses of the ETHs on the transmitting and receiving sides of the communication devices 10D to 10H, respectively. Also, in the counterclockwise direction CCW, "transfer possible" is recorded in association with the MAC addresses of the ETHs on the transmitting and receiving sides of the communication devices 10H to 10E, respectively. Also, in the counterclockwise direction CCW, "transfer impossible" is recorded in association with the MAC addresses of the ETHs on the transmitting and receiving sides of the communication devices 10B to 10D, respectively.

[0113] Based on the updated route information table RI, the communication device 10A can infer that a failure has occurred between the communication devices 10C and 10D in the clockwise direction CW, and that a failure has occurred between the communication devices 10E and 10D in the counterclockwise direction CCW. Furthermore, since the communication device 10A has not received the route search frame RSF transmitted from the communication device 10D in both directions, the communication device 10A can infer that frames cannot be transferred between the communication devices 10C and 10E, including the communication device 10D. In other words, the communication device 10A can infer that when transferring frames to the communication device 10D, the communication device 10A cannot transfer frames in both directions.

[0114] Furthermore, the communication device 10A can determine the optimal forwarding path for the frame based on the updated route information table RI. For example, when traffic occurs to a destination other than the communication device 10D, the communication device 10A first determines the forwarding path for the frame by the forwarding path determination operation described in the first embodiment. After that, if the determined forwarding path includes the detected failure point (communication device 10D), the communication device 10A changes the forwarding path to one that does not include the failure point and forwards the frame.

[0115] (Example 5) FIG. 20 is a schematic diagram showing a fifth example of an abnormality that has occurred in the ring network 1 according to the second embodiment. The fifth example corresponds to a case where a delay in frame forwarding occurs on a certain path on the ring network 1. FIG. 20 illustrates a case where the time required for bridge forwarding between the Ethernet interfaces ETH0 and ETH1 of the communication device 10F is slower than usual. However, in this example, it is assumed that the route search frame RSF transmitted from the communication device 10A satisfies equation (1) and is received by the communication device 10A. A method by which the communication device 10A identifies the location of the abnormality shown in FIG. 20 will be described below.

[0116] In this example, the communication device 10A can receive route search frames RSF from all communication devices 10 except itself in both the clockwise direction CW and the counterclockwise direction CCW, satisfying formula (1). On the other hand, the communication device 10A receives route search frames RSF transmitted from each of the communication devices 10B to 10E in the clockwise direction CW and route search frames RSF transmitted from each of the communication devices 10G and 10H in the counterclockwise direction CW, in a state satisfying formula (4).

[0117] Then, the communication device 10A updates the route information table RI based on the reception status of the route information table RI from the other communication devices 10. An example of the configuration of the route information table RI in the fifth example is shown in FIG. 21. As shown in FIG. 21, in this example, in the clockwise direction CW, "transfer possible" is recorded in association with the MAC addresses of the ETHs of the transmitting and receiving sides of each of the communication devices 10B to 10E and the MAC address of the ETH of the receiving side of the communication device 10F. In the clockwise direction CW, "transfer delay" is recorded in association with the MAC addresses of the ETHs of the transmitting and receiving sides of the communication devices 10G and 10H. Furthermore, in the counterclockwise direction CCW, "transfer possible" is recorded in association with the MAC addresses of the ETHs of the transmitting and receiving sides of each of the communication devices 10H and 10G and the MAC address of the ETH of the receiving side of the communication device 10F. In the counterclockwise direction CCW, the transfer delay is recorded in association with the ETH MAC address of the transmitting side of the communication device 10F and the ETH MAC addresses of the transmitting and receiving sides of each of the communication devices 10F to 10B.

[0118] Based on the updated route information table RI, the communication device 10A can infer that a larger than normal delay is occurring in frame transfer between the communication devices 10E and 10F in the clockwise direction CW, and between the communication devices 10G and 10F in the counterclockwise direction CCW. Furthermore, because the communication device 10A can receive the route search frame RSF transmitted from the communication device 10F in both directions as normal, it can infer that a larger than normal delay is occurring in bridge transfer between the Ethernet interfaces ETH0 and ETH1 of the communication device 10F.

[0119] Furthermore, the communication device 10A can determine the optimal transfer path for the frame based on the updated route information table RI. Specifically, when a communication device 10 in which a delay is occurring is included on the ring network 1, the communication device 10A executes a transfer path determination operation that takes the delay into consideration. For example, when traffic to the communication device 10D occurs, the communication device 10A first compares the transfer times to the communication device 10D in both directions, as in the transfer path determination operation of the first embodiment. Here, when the counterclockwise direction CCW is selected, the communication device 10F is included in the transfer path from the communication device 10A to the communication device 10D. In this case, the communication device 10A determines the transfer path by also taking into consideration the delay occurring in the communication device 10F. The delay time Delay occurring in the communication device 10F F,dir is expressed by the following equation (7).

[0120]

number

[0121] Delay time occurring in the counterclockwise direction (CCW) of the communication device 10F F,CCW As shown in equation (7), the delay time can be calculated based on the time it takes for the route search frame RSF transmitted in the counterclockwise direction CCW from the communication device 10G adjacent to the ETH on the receiving side of the communication device 10F in the counterclockwise direction CCW to reach the communication device 10A. The communication device 10A then adds the calculated delay time to the transfer time to the communication device 10D in the counterclockwise direction CCW and compares the transfer times to the communication device 10D in both directions. The communication device 10A then determines the transfer route of the frame in the direction with the shortest transfer time. In this way, the communication device 10A can determine the optimal transfer route of the frame when a delay in frame transfer occurs on a certain route on the ring network 1.

[0122] The delay time of any communication device 10i other than the communication device 10F can be calculated using the same calculation as in equation (7). In this case, in equation (7), the part corresponding to the communication device 10G is replaced with the value of the communication device 10 adjacent to ETH on the receiving side of the communication device 10i in both directions. In the fifth example, each communication device 10 may determine the transfer path of the frame in the direction with the shortest transfer time, taking into account the delay time when passing through the communication device 10 in which a delay occurs.

[0123] <2-3> Effects of the second embodiment The effects of the ring network 1 according to the second embodiment will be described below.

[0124] When a failure occurs in an Ethernet communication path, including a ring network, multiple communication paths can be selected using protocols such as RSTP (Rapid Spanning Tree Protocol). However, RSTP does not take into account the transfer time between communication paths, making it difficult to select a path that takes into account the transfer efficiency between communication paths or localized failures caused by abnormal transfer delays. Furthermore, when a localized failure occurs, it is possible to transfer frames by bypassing the point of failure. However, because this detouring process is performed near the point of failure, there is a possibility that a communication path requiring a longer transfer time than usual will be selected.

[0125] Therefore, the ring network 1 according to the second embodiment identifies the presence or absence of an abnormality (failure or delay) on the communication path and the location of the occurrence based on the result of circulating the route search frame RSF on the ring network 1. Then, in the second embodiment, the transfer direction of the frame is determined based on the presence or absence of a failure on the communication path, also utilizing the transfer path determination operation described in the first embodiment.

[0126] This allows each communication device 10 in the second embodiment to select an optimal communication route that avoids failure points. That is, in the second embodiment, even if an abnormality occurs on the ring network 1, each communication device 10 can select a route with a shorter transfer time and transfer the frame to any communication device 10. Therefore, the ring network 1 according to the second embodiment is as efficient as the first embodiment, and can achieve more stable communication than the first embodiment.

[0127] <3> Third embodiment The third embodiment relates to a specific example in which the ring network 1 described in the first and second embodiments is mounted on a vehicle. Details of the third embodiment will be described below.

[0128] <3-1> Configuration Fig. 22 is a schematic diagram showing an example of the configuration of a ring network 1 according to the third embodiment. As shown in Fig. 22, the ring network 1 is mounted on a vehicle 2. The top of the paper in Fig. 22 corresponds to the front of the vehicle body of the vehicle 2. The vehicle 2 includes, for example, communication devices 10A to 10H, similar to the first and second embodiments.

[0129] In the third embodiment, the communication device 10A is disposed on the front right side of the vehicle 2 and functions as a forward monitoring unit and a telematics unit. The forward monitoring unit is, for example, a camera capable of capturing images in front of the vehicle body. The telematics unit is a communication module (for example, a GPS) capable of communicating with the outside. The communication device 10B is disposed on the right side of the vehicle 2 and functions as a side monitoring unit. The side monitoring unit of the communication device 10B is, for example, a camera capable of capturing images of the right side of the vehicle body. The communication device 10C is disposed on the rear right side of the vehicle 2 and functions as a rear monitoring unit. The rear monitoring unit is, for example, a camera capable of capturing images of the rear of the vehicle body. The communication device 10D is disposed on the rear center part of the vehicle 2 and functions as a first central processing unit. The first central processing unit is, for example, a first computer used to control the vehicle 2. The communication device 10E is disposed on the rear left side of the vehicle 2 and functions as a rear monitoring unit. The communication device 10F is disposed on the left side of the vehicle 2 and functions as a side monitoring unit. The side monitoring unit of communication device 10F is, for example, a camera capable of capturing images of the left side of the vehicle body. Communication device 10G is disposed on the front left side of vehicle 2 and functions as a front monitoring unit and a navigation unit. The navigation unit is, for example, a car navigation system that guides the driver in the direction of travel of vehicle 2 based on the position and destination of vehicle 2. Communication device 10H is disposed on the front center part of vehicle 2 and functions as a second central processing unit. The second central processing unit is, for example, a first computer used to control vehicle 2.

[0130] In the ring network 1 according to the third embodiment, as in the first embodiment, slots for a high-priority frame HPF, a medium-priority frame MPF, a low-priority frame LPF, and a route search frame RSF are set as a GCL shared by each communication device 10. In the vehicle 2, the high-priority frame HPF is used, for example, in communication with an ECU (Engine Control Unit). In the vehicle 2, the medium-priority frame MPF is used, for example, in communication of control signals for doors, etc. In the vehicle 2, the low-priority frame LPF is used, for example, in Internet access. In the vehicle 2, the route search frame RSF is used to realize the route information collection operation and the transfer route determination operation described in the first and second embodiments.

[0131] The above-described configuration of the ring network 1 is merely an example. When the vehicle 2 is equipped with the ring network 1, the functions assigned to each communication device 10 may be configured differently.

[0132] <3-2> Effects of the third embodiment As described above, in the third embodiment, the ring network 1 described in the first and second embodiments is used in an in-vehicle communication network system that complies with TSN. This allows the vehicle 2 according to the third embodiment to improve the efficiency and stability of communication between the communication devices 10. Therefore, the vehicle 2 according to the third embodiment can improve the safety performance of the vehicle.

[0133] <4> others In the ring network 1, the CPU 21 of the host device 20 and the CPU 31 of the communication IC 30 may each be other circuits. For example, the host device 20 and the communication IC 30 may each be equipped with an MPU (Micro Processing Unit) instead of a CPU. Each of the processes described in the embodiments may be realized by dedicated hardware. The processes of the host device 20 and the communication IC 30 may be a mixture of processes executed by software and processes executed by hardware, or may be only one of them.

[0134] In the above embodiments, the flowcharts used to explain the operations are merely examples. The order of the processes of each operation described in the embodiments may be changed as far as possible, and other processes may be added. For example, the flow of the route information collection operation and the forwarding route determination operation described in the first embodiment are merely examples. Furthermore, the format of the Ethernet frame described in the first embodiment is merely an example. The ring network 1 may apply other formats to the route search frame RSF as long as it is capable of performing the operations described in the embodiments. In the above embodiments, the number of communication devices 10 included in the ring network 1 may be three or more.

[0135] In this specification, the term "clockwise direction CW" refers to the direction in which, among multiple communication devices 10 connected in a ring, a frame is transmitted to an adjacent communication device 10 on one side, and the frame circulates on the ring network 1. The term "counterclockwise direction CCW" refers to the direction in which, among multiple communication devices 10 connected in a ring, a frame is transmitted to an adjacent communication device 10 on the other side, and the frame circulates on the ring network 1. In this specification, the same definition of the transmission direction of the communication devices 10 in the ring network 1 may be applied among multiple communication devices 10. In this specification, "substantially simultaneously" refers to a time difference that is less than a predetermined time. For example, when the transmission timings of the route search frames RSF by the Ethernet interfaces ETH0 and ETH1 are substantially simultaneous, this means that the difference between the transmission time of the RSF by ETH0 and the transmission time of the RSF by ETH1 is less than a predetermined time. In this specification, this predetermined time is at least equal to or less than the length of the slot assigned to the route search frame RSF by the GCL.

[0136] Although several embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be embodied in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included within the scope and spirit of the invention, and are also included in the scope of the invention and its equivalents as defined in the claims. [Explanation of symbols]

[0137] 1... ring network, 2... vehicle, 10... communication device, 20... host device, 21... CPU, 22... ROM, 23... RAM, 24... functional unit, 25... hardware interface, 31... CPU, 32... ROM, 33... RAM, 34... hardware interface, 35, 36... Ethernet interface, 201... data transmission / reception unit, 202... time synchronization unit, 203... route information collection unit, 204... transfer route switching unit, 205... abnormality detection unit, 301... data transmission / reception unit, 302, 303... signal processing unit, ETH... Ethernet interface, 30... communication IC

Claims

1. A ring network comprising a plurality of communication devices, Each of the plurality of communication devices has a first Ethernet interface connected to an adjacent communication device on one side, a second Ethernet interface connected to an adjacent communication device on the other side, and a host device capable of transmitting and receiving data to and from other communication devices on the ring network using the first Ethernet interface and the second Ethernet interface; the plurality of communication devices include a first communication device and a second communication device; the first communication device transmits a first frame from its second Ethernet interface in a clockwise direction and a second frame from its first Ethernet interface in a counterclockwise direction within a first period; the second communication device, when receiving the first frame generated by the first communication device, adding to a payload of the first frame a MAC address of the first Ethernet interface of the first communication device, a reception timestamp of the first frame, a MAC address of the second Ethernet interface of the first communication device, and a transmission timestamp of the first frame, and transmitting the first frame to an adjacent communication device in the clockwise direction; when receiving the second frame generated by the first communication device, adding to the payload of the second frame the MAC address of the second Ethernet interface of the first communication device, a reception timestamp of the second frame, the MAC address of the first Ethernet interface of the first communication device, and a transmission timestamp of the second frame, and transmitting the second frame to the adjacent communication device in the counterclockwise direction; Ring network.

2. the first communication device transmits the first frame and the second frame at substantially the same time; The ring network of claim 1 .

3. The EtherType of the first frame and the second frame is the same. The ring network of claim 1 .

4. the first communication device stores a route information table in which information regarding frame forwarding in the clockwise direction to the plurality of communication devices excluding itself and information regarding frame forwarding in the counterclockwise direction to the plurality of communication devices excluding itself are recorded; In the first communication device, the host device updates the route information table based on information included in the payload of the first frame received by the first Ethernet interface and information included in the payload of the second frame received by the second Ethernet interface. The ring network of claim 1 .

5. The first communication device calculate a transfer time of the frame in the clockwise direction to the second communication device based on a difference in the clockwise direction between a reception timestamp of the second communication device and a time at which the second Ethernet interface of the second communication device transmitted the first frame, and record the calculation result in the route information table; calculate a transfer time of the frame in the counterclockwise direction to the second communication device based on a difference between a reception timestamp of the second communication device in the counterclockwise direction and a time at which the first Ethernet interface of the second communication device transmits the second frame, and record the calculation result in the route information table; The ring network of claim 4.

6. when traffic to the second communication device occurs, the first communication device determines a forwarding route for the traffic in the clockwise direction or the counterclockwise direction, whichever direction provides the shortest forwarding time to the second communication device, based on the route information table. The ring network of claim 5 .

7. the first communication device associates a hop count based on the number of Ethernet interfaces traversed to reach the second communication device with a MAC address of the first Ethernet interface and a MAC address of the second Ethernet interface of the second communication device in each of the clockwise direction and the counterclockwise direction, and records the hop count in the route information table; The ring network of claim 5 .

8. When traffic to the second communication device occurs and the forwarding times in the clockwise direction and the counterclockwise direction recorded in the route information table are the same, the first communication device determines a forwarding route for the traffic to be the direction with the fewer hops between the clockwise direction and the counterclockwise direction. The ring network of claim 7.

9. the first communication device determines a forwarding route for the traffic in the clockwise direction when traffic to the second communication device occurs, the forwarding times in the clockwise direction and the counterclockwise direction recorded in the route information table are the same, and the number of hops in the clockwise direction and the counterclockwise direction are the same; The ring network of claim 7.

10. the first communication device detects whether a failure has occurred on the network based on whether the first frame and the second frame have been received within a timeout period after transmitting the first frame and the second frame, respectively; The ring network of claim 1 .

11. A ring network comprising a plurality of communication devices, Each of the plurality of communication devices has a first Ethernet interface connected to an adjacent communication device on one side, a second Ethernet interface connected to an adjacent communication device on the other side, and a host device capable of transmitting and receiving data to and from other communication devices on the ring network using the first Ethernet interface and the second Ethernet interface; the plurality of communication devices includes a first communication device; the first communication device transmits a first frame from its second Ethernet interface in a clockwise direction and a second frame from its first Ethernet interface in a counterclockwise direction within a first period; each of the plurality of communication devices has an opportunity to transmit the first frame, which designates its own first Ethernet interface as a destination, from its own second Ethernet interface in the clockwise direction, and to transmit the second frame, which designates its own second Ethernet interface as a destination, from its own first Ethernet interface in the counterclockwise direction; the first communication device identifies a location where a failure has occurred on the network based on a reception status of the first frame and the second frame generated by another communication device; Ring network.

12. the plurality of communication devices includes a second communication device; When traffic to the second communication device occurs, the first communication device determines a forwarding path for the traffic in one of the clockwise direction and the counterclockwise direction, which is a direction that does not include a failure in the communication path between the first communication device and the second communication device. The ring network of claim 11.

13. the first communication device stores a route information table in which information regarding frame forwarding in the clockwise direction to the plurality of communication devices excluding itself and information regarding frame forwarding in the counterclockwise direction to the plurality of communication devices excluding itself are recorded; In the first communication device, the host device updates the route information table based on information included in the payload of the first frame received by the first Ethernet interface and information included in the payload of the second frame received by the second Ethernet interface. The ring network of claim 11.

14. the first communication device records at least one of information on whether a frame can be forwarded and information on a delay of a frame in the route information table, corresponding to each of the clockwise direction and the counterclockwise direction, based on a reception status of the first frame and the second frame from another communication device; The ring network of claim 13.

15. the plurality of communication devices includes a second communication device; When traffic to the second communication device occurs, the first communication device determines, based on the route information table, either the clockwise direction or the counterclockwise direction as a transfer direction of the traffic, and when a failure is included in the determined transfer direction, changes the transfer direction to a direction that does not include the failure or a direction that takes a shorter transfer time. The ring network of claim 14.

16. each of the plurality of communication devices, when a frame identical to a frame transmitted from one of the first Ethernet interface and the second Ethernet interface is received by the other of the first Ethernet interface and the second Ethernet interface, drops the received frame; The ring network of claim 11.

17. the host device of the first communication device, when the first frame and the second frame generated by itself reach the host device, acquires information about communication devices other than itself from the first frame and the second frame; 17. The ring network of claim 16.

18. the plurality of communication devices share a periodic transmission schedule; the transmission schedule includes the first period and a third period allocated to communication of frames other than the first frame and the second frame; The ring network of claim 11.

19. the plurality of communication devices are mounted on a vehicle, the host device of each of the plurality of communication devices is used to control the vehicle; The ring network of claim 11.

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