Delay adjustment device and redundant line system

Abstract

This delay adjustment device absorbs the inter-system delay difference and fluctuation between lines in two systems to enable inter-system uninterruptible switching. The delay adjustment device is provided with a first transmission / reception unit, a second transmission / reception unit, and a control unit. The control unit controls the transmittable timing of frames of each transmission / reception unit to be a constant interval. The control unit calculates a delay difference time on the basis of the difference between the frame reception times of the transmission / reception units. The control unit sets the delay difference time in the transmission / reception unit that received a frame first. The one transmission / reception unit in which the delay difference time is set transmits the frame, which is stored in a buffer, to a reception device at the next transmittable timing after the delay difference time has elapsed following reception of the frame. The other transmission / reception unit in which the delay difference time is not set transmits the frame, which is stored in a buffer, to the reception device at the next transmittable timing after reception of the frame.

Description

Technical Field

[0001] The present disclosure relates to a delay adjustment device and a redundant line system, and particularly to a delay adjustment device and a redundant line system that enable seamless switching of redundant communication lines.

Background Art

[0002] For example, as disclosed in Non-Patent Document 1, a seamless switching technique is known. The seamless switching technique is a redundancy technique in which a transmission device copies the same frame to two redundant paths, and a receiving device checks the received frames and selects and transmits a normal frame, so as not to cause a communication interruption during a transmission line failure.

Prior Art Documents

Non-Patent Documents

[0003]

Non-Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] For example, in a dedicated line service, when a momentary interruption occurs in the line due to maintenance work or the like, it is necessary to go through the procedure of borrowing a line after obtaining the prior consent of the customer, which complicates the work of the maintainer. In addition, when the lines to be accommodated include important lines such as telemedicine, momentary interruptions of the lines are not allowed, so it is necessary to ensure seamless switching in the redundant lines.

[0005] The host device and the subordinate device having a redundant switching function between the operation system and the standby system are connected between the devices by two systems of an operation system line and a standby system line. When the operation system line is composed of a wire such as an optical cable and the standby system line is composed of a transmission device such as a wireless system, a large delay difference occurs between the systems. In addition, when a transmission device is applied to the line, jitter (variation in delay time) is inserted by the transmission device. Jitter is the degree of change in the delay time. In order to perform seamless redundant switching between devices, the inter-system delay difference and fluctuation must be less than the upper limit value. In order to suppress interruption, a mechanism for reducing the inter-system delay difference and fluctuation between devices is desired.

[0006] The present disclosure has been made to solve the above-described problems, and an object thereof is to provide a delay adjustment device and a redundant line system that absorb the inter-system delay difference and fluctuation of two systems of lines and enable seamless switching between systems.

Means for Solving the Problems

[0007] The first aspect relates to a delay adjustment device. The delay adjustment device is provided in a redundant line system. The redundant line system is a system in which a transmission device and a reception device are connected by two systems of a first path and a second path. The first path and the second path transmit the same frame. The delay adjustment device connects between the transmission device and the reception device. The delay adjustment device includes a first transceiver, a second transceiver, and a control unit. The first transceiver temporarily stores the frame received from the transmission device via the first path in the first buffer. The second transceiver temporarily stores the frame received from the transmission device via the second path in the second buffer. The control unit controls the transmission enable timing of the frames in the first transceiver and the second transceiver at regular intervals. The control unit calculates a delay difference time based on the difference between the first reception time of the measurement frame received from the transmission device via the first path and the second reception time of the measurement frame received from the transmission device via the second path. When the first reception time is earlier than the second reception time, the control unit sets the delay difference time in the first transmission / reception unit. When the second reception time is earlier than the first reception time, the control unit sets the delay difference time in the second transmission / reception unit. When the delay difference time is set, the first transmission / reception unit transmits the frame stored in the first buffer to the receiving device at the next transmission possible timing after the delay difference time has elapsed since the frame was received. When the delay difference time is not set, the first transmission / reception unit transmits the frame stored in the first buffer to the receiving device at the next transmission possible timing after the frame was received. When the delay difference time is set, the second transmission / reception unit transmits the frame stored in the second buffer to the receiving device at the next transmission possible timing after the delay difference time has elapsed since the frame was received. When the delay difference time is not set, the second transmission / reception unit transmits the frame stored in the second buffer to the receiving device at the next transmission possible timing after the frame was received.

[0008] In addition to the first aspect, the second aspect further has the following features. When the first reception time is earlier than the second reception time, the control unit sets the size of the first buffer to be larger than that of the second buffer as the delay difference time is larger. When the second reception time is earlier than the first reception time, the control unit sets the size of the second buffer to be larger than that of the first buffer as the delay difference time is larger.

[0009] The third aspect relates to a redundant line system. The redundant line system is a system that connects between a transmitting device and a receiving device through two paths, a first path and a second path. The first path and the second path transmit the same frame. The redundant line system includes a delay adjustment device that connects between the transmitting device and the receiving device. The delay adjustment device includes a first transceiver, a second transceiver, and a control unit. The first transceiver temporarily stores the frame received from the transmitting device via the first path in a first buffer. The second transceiver temporarily stores the frame received from the transmitting device via the second path in a second buffer. The control unit controls the transmission enable timing of the frames in the first transceiver and the second transceiver at regular intervals. The control unit calculates a delay difference time based on the difference between a first reception time of a measurement frame received from the transmitting device via the first path and a second reception time of the measurement frame received from the transmitting device via the second path. When the first reception time is earlier than the second reception time, the control unit sets the delay difference time in the first transceiver. When the second reception time is earlier than the first reception time, the control unit sets the delay difference time in the second transceiver. When the delay difference time is set, the first transceiver transmits the frame stored in the first buffer to the receiving device at the next transmission enable timing after the delay difference time has elapsed since the frame was received. When the delay difference time is not set, the first transceiver transmits the frame stored in the first buffer to the receiving device at the next transmission enable timing after the frame was received. When the delay difference time is set, the second transceiver transmits the frame stored in the second buffer to the receiving device at the next transmission enable timing after the delay difference time has elapsed since the frame was received. When the delay difference time is not set, the second transceiver transmits the frame stored in the second buffer to the receiving device at the next transmit-able timing after receiving the frame.

[0010] The fourth aspect further has the following features in addition to the third aspect. When the first reception time is earlier than the second reception time, the control unit sets the size of the first buffer to be larger than that of the second buffer as the delay difference time is larger. When the second reception time is earlier than the first reception time, the control unit sets the size of the second buffer to be larger than that of the first buffer as the delay difference time is larger.

Advantages of the Invention

[0011] According to the present disclosure, by fixedly setting the calculated delay difference time in the transceiver that first receives the frame among the two transceivers, the inter-system delay difference can be absorbed. Further, by controlling the transmit-able timing of the frame sent from the buffer at regular intervals, the fluctuations occurring in a wireless system or the like can be absorbed. By absorbing the inter-system delay difference and fluctuations, high service quality due to seamless switching between systems can be ensured. According to the present disclosure, even when the two communication paths are configured using arbitrary devices, the inter-system delay difference and fluctuations can be absorbed, and seamless switching between systems is possible.

Brief Description of the Drawings

[0012]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Embodiments for Carrying Out the Invention

[0013] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the drawings, the same reference numerals are assigned to common elements, and duplicate descriptions are omitted.

[0014] Embodiment 1. 1. Redundant line system FIG. 1 is a diagram for explaining a configuration example of a redundant line system according to the embodiment. The redundant line system shown in FIG. 1 includes a delay adjustment device 1, an upper device 2, a lower device 3, and a relay device 4 (an operation system relay device 4a and a standby system relay device 4b). In the following description, regarding the application of the delay adjustment device 1, the flow of a signal in the downstream direction from the upper device 2 to the lower device 3 will be described as an example. In this case, the upper device 2 functions as a transmission device, and the lower device 3 functions as a reception device.

[0015] The redundant line system connects between the upper device 2 and the lower device 3 with two systems: an operation system communication path (first path) and a standby system communication path (second path). The same frame copied in the upper device 2 as the transmission device is transmitted to the lower device 3 as the reception device via two redundant paths. The transmission method is, for example, Ethernet (registered trademark). The upper device 2 and the lower device 3 have a redundant switching function between the operation / standby systems.

[0016] The relay device 4 is composed of, for example, a wired optical cable or a wireless transmission device. As an example, the operation system communication path is composed of one or more operation system relay devices 4a having an optical cable. The standby system communication path is composed of one or more standby system relay devices 4b having a transmission device such as a wireless system. In paths with different path lengths and facilities, a large delay difference may occur between the paths. Further, when a transmission device is applied to a redundant line, fluctuations of the transmission device are inserted.

[0017] The delay adjustment device 1 is a device for absorbing the inter-system delay difference and fluctuations. The delay adjustment device 1 shown in FIG. 1 is connected between the relay device 4 and the lower device 3, that is, immediately upstream of the receiving device. The delay adjustment device 1 arranged in this way absorbs the inter-system delay difference and fluctuations of the frames transmitted from the two systems of the operation system relay device 4a and the standby system relay device 4b, and transmits them to the operation system interface unit and the standby system interface unit of the lower device 3.

[0018] 2. Outline of the Function of the Delay Adjustment Device FIG. 2 is a block diagram illustrating an outline of the functions of the delay adjustment device 1 according to the embodiment.

[0019] The delay adjustment device 1 enables seamless switching between the operation system and the standby system by the upper device 2 and the lower device 3 by absorbing the inter-system delay difference and fluctuations (jitter). The delay adjustment device 1 includes an operation system interface unit 10 (first transmission / reception unit), a standby system interface unit 20 (second transmission / reception unit), and a control unit 30.

[0020] 2-1. Operation System Interface Unit The operation system interface unit 10 includes a relay-side interface 11, an operation-side buffer 12 (first buffer), and a node-side interface 13.

[0021] The relay-side interface 11 has a communication circuit and is connected to the operation system relay device 4a in FIG. 1. The relay-side interface 11 outputs the frame received from the operation system relay device 4a on the operation system communication path to the operation-side buffer 12. Also, the relay-side interface 11 outputs the signal arrival information of the received frame to the control unit 30.

[0022] The operation-side buffer 12 is a FIFO-type buffer, that is, a queue. The operation-side buffer 12 temporarily stores the frame input from the relay-side interface 11 via the operation system communication path in order to absorb the inter-system delay difference and fluctuation.

[0023] The node-side interface 13 has a communication circuit and is connected to the operation system interface section of the lower device 3 in FIG. 1. The node-side interface 13 can transmit the frame temporarily stored in the operation-side buffer 12 to the operation system interface section of the lower device 3.

[0024] In the operation system interface section 10, the transmission enable timing and the delay difference time can be set by the control unit 30 described later. The timing at which a frame can be transmitted arrives at regular intervals. The operation system interface section 10 can transmit the frame stored in the operation-side buffer 12 in frame units each time the transmission enable timing at regular intervals arrives. However, this is not the case until the delay difference time has elapsed when the delay difference time is set.

[0025] When the delay difference time is set, the operation system interface section 10 transmits the frame stored in the operation-side buffer 12 to the lower device 3 at the next arrival transmission enable timing after the delay difference time has elapsed since the frame was received. Also, when the delay difference time is not set, the operation system interface section 10 transmits the frame stored in the operation-side buffer 12 to the lower device 3 at the next arrival transmission enable timing after the frame is received.

[0026] 2-2. Standby System Interface Section The standby interface unit 20 has the same configuration as the operation interface unit 10. The standby interface unit 20 includes a relay-side interface 21, a standby-side buffer 22 (second buffer), and a node-side interface 23.

[0027] The relay-side interface 21 has a communication circuit and is connected to the standby relay device 4b in FIG. 1. The relay-side interface 21 outputs the frame received from the standby relay device 4b on the standby communication path to the standby-side buffer 22. Also, the relay-side interface 21 outputs the signal arrival information of the received frame to the control unit 30.

[0028] The standby-side buffer 22 is a FIFO-type buffer, that is, a queue. The standby-side buffer 22 temporarily stores the frame input from the relay-side interface 21 via the standby communication path in order to absorb the inter-system delay difference and fluctuation.

[0029] The node-side interface 23 has a communication circuit and is connected to the standby interface unit of the lower device 3 in FIG. 1. The node-side interface 23 can transmit the frame temporarily stored in the standby-side buffer 22 to the standby interface unit of the lower device 3.

[0030] The transmission timing and the delay difference time can be set in the standby interface unit 20 by the control unit 30 described later. The timing at which the frame can be transmitted arrives at regular intervals. The standby interface unit 20 can transmit the frame stored in the standby-side buffer 22 in frame units each time the transmission timing at regular intervals arrives. However, this is not the case until the delay difference time has elapsed when the delay difference time is set.

[0031] When a delay difference time is set, the standby interface unit 20 transmits the frame stored in the standby buffer 22 to the lower device 3 at the next available transmission timing after the delay difference time has elapsed since the frame was received. Also, when no delay difference time is set, the standby interface unit 20 transmits the frame stored in the standby buffer 22 to the lower device 3 at the next available transmission timing after the frame is received.

[0032] 2-3. Control Unit The control unit 30 inputs signal arrival information from the operation interface unit 10. The signal arrival information of the operation system includes the reception time (first reception time TA) of the frame received by the operation interface unit 10. Also, the control unit 30 inputs signal arrival information from the standby interface unit 20. The signal arrival information of the standby system includes the reception time (second reception time TB) of the frame received by the standby interface unit 20.

[0033] For convenience, the frame targeted by the delay difference detection process 31 is referred to as the measurement frame. The delay difference detection process 31 calculates the delay difference time based on the absolute value of the difference between the first reception time TA of the measurement frame received from the upper device 2 via the operation system communication path and the second reception time TB of the measurement frame received from the upper device 2 via the standby system communication path. The delay difference detection process 31 sets the delay difference time for the interface unit that received the measurement frame first among the operation interface unit 10 and the standby interface unit 20.

[0034] Also, the control unit 30 controls the frame transmission available timings in the operation interface unit 10 and the standby interface unit 20 at regular intervals.

[0035] Further, the control unit 30 may set a larger buffer size for the interface unit that received the measurement packet earlier as the measured delay difference time is larger. For example, when the first reception time TA is earlier than the second reception time TB, the control unit 30 sets the size of the operation-side buffer 12 to be larger than that of the standby-side buffer 22 as the delay difference time is larger. When the second reception time TB is earlier than the first reception time TA, the control unit 30 sets the size of the standby-side buffer 22 to be larger than that of the operation-side buffer 12 as the delay difference time is larger.

[0036] 3. Delay difference and fluctuation absorption processing 3-1. Specific example FIG. 3 is a timing chart for explaining an example to which the delay difference and fluctuation absorption processing according to the embodiment is applied.

[0037] In FIG. 3, the transmission enable timings of the frames in the operation system interface unit 10 and the standby system interface unit 20 are set at a constant interval T. Ta is the reception time of a frame (hereinafter referred to as frame A) received by the operation system interface unit 10 after the measurement frame. Tb is the reception time of frame A received by the standby system interface unit 20. X is the delay difference time calculated by the control unit 30 for the measurement frame received before frame A. In FIG. 3, it is assumed that the delay difference time X is set in the operation system interface unit 10. Y is the transmission waiting time from time Tc to the transmission enable timing T3.

[0038] At time Ta, the operation system interface unit 10 receives frame A and temporarily stores frame A in the operation-side buffer 12. The delay difference time X is set in the operation system interface unit 10. Therefore, the operation system interface unit 10 waits from time Ta until time Tc when the delay difference time X has elapsed. Thereafter, the operation system interface unit 10 transmits frame A stored in the operation-side buffer 12 to the lower device 3 at the next transmission enable timing T3.

[0039] At time Tb, the standby interface unit 20 receives frame A and temporarily stores frame A in the standby buffer 22. No delay difference time X is set in the standby interface unit 20. Therefore, at the next transmission available timing T3, the standby interface unit transmits frame A stored in the standby buffer 22 to the lower device 3.

[0040] Thus, in the example of FIG. 3, the delay adjustment device 1 can absorb the delay difference and fluctuation by setting the delay difference time X in the operation interface unit 10 and setting the transmission available timing at a constant interval T in the operation interface unit 10 and the standby interface unit 20.

[0041] 3-2. Example of flowchart FIG. 4 is a flowchart illustrating the delay difference and fluctuation absorption process executed by the delay adjustment device 1 according to the embodiment. Note that the transmission available timing of the frame in the operation interface unit 10 and the standby interface unit 20 is set at a constant interval.

[0042] In step S100, when the operation interface unit 10 receives a frame, it temporarily stores the frame in the operation buffer 12.

[0043] In step S101, the operation interface unit 10 outputs signal arrival information to the control unit 30. The signal arrival information includes the reception time of the frame (the first reception time TA).

[0044] In step S200, when the standby interface unit 20 receives a frame, it temporarily stores the frame in the standby buffer 22.

[0045] In step S201, the standby interface unit 20 outputs signal arrival information to the control unit 30. The signal arrival information includes the reception time of the frame (the second reception time TB).

[0046] In step S300, the control unit 30 calculates a delay difference time (delay amount) based on the absolute value of the difference between the first reception time TA and the second reception time TB. Further, the control unit 30 outputs an instruction to unset the delay difference time to the operation system interface unit 10 and the standby system interface unit 20 in order to reset the delay difference time set in any of the interface units once.

[0047] In step S301, the control unit 30 compares the first reception time TA and the second reception time TB. When TA < TB, the control unit 30 outputs the delay difference time to the operation system interface unit 10. When TA > TB, the control unit 30 outputs the delay difference time to the standby system interface unit 20. Note that when TA = TB, since the delay difference time is 0, there is no need to output the delay difference time.

[0048] When TA < TB, in step S102, the operation system interface unit 10 sets the delay difference time input from the control unit 30. The set delay difference time is applied to the process of step S103 when the next frame is received.

[0049] When TA > TB, in step S202, the standby system interface unit 20 sets the delay difference time input from the control unit 30. The set delay difference time is applied to the process of step S203 when the next frame is received.

[0050] Incidentally, the processing regarding the delay difference time according to steps S101, S102, S200, S201, S300, and S301 described above may be executed every time a frame is received, or may be executed every predetermined cycle. That is, the recalculation and resetting of the delay difference time may be executed after a predetermined period.

[0051] Return to step S100 and continue the explanation. After receiving a frame in step S100 described above, the process of step S103 is executed. In step S103, the operation system interface unit 10 determines whether a delay difference time is set. If a delay difference time is set, the process of step S104 is executed. If a delay difference time is not set, the process of step S105 is executed.

[0052] When a delay difference time is set, in step S104, the operation system interface unit 10 transmits the frame stored in the operation side buffer 12 to the lower device 3 at the next transmission possible timing after the delay difference time has elapsed since receiving the frame.

[0053] On the other hand, when a delay difference time is not set, in step S105, the operation system interface unit 10 transmits the frame stored in the operation side buffer 12 to the lower device 3 at the next transmission possible timing after receiving the frame.

[0054] Return to step S200 and continue the explanation. After receiving a frame in step S200 described above, the process of step S203 is executed. In step S203, the standby system interface unit 20 determines whether a delay difference time is set. If a delay difference time is set, the process of step S204 is executed. If a delay difference time is not set, the process of step S205 is executed.

[0055] When a delay difference time is set, in step S204, the standby system interface unit 20 transmits the frame stored in the standby side buffer 22 to the lower device 3 at the next transmission possible timing after the delay difference time has elapsed since receiving the frame.

[0056] On the other hand, when a delay difference time is not set, in step S205, the standby system interface unit 20 transmits the frame stored in the standby side buffer 22 to the lower device 3 at the next transmission possible timing after receiving the frame.

[0057] 4. Modification Example Incidentally, in the above-described embodiment, the application of the delay adjustment device 1 to the downstream signal from the upper device 2 to the lower device 3 has been described. However, the delay adjustment device 1 can also be applied to the upstream signal from the lower device 3 to the upper device 2. In this case, the delay adjustment device 1 is connected between the upper device 2 and the relay device 4, and the lower device 3 functions as a transmission device, and the upper device 2 functions as a reception device.

[0058] Also, in the above-described embodiment, the operation system interface unit 10 is used as the first transmission / reception unit, and the standby system interface unit 20 is used as the second transmission / reception unit. However, the operation system interface unit 10 may be used as the second transmission / reception unit, and the standby system interface unit 20 may be used as the first transmission / reception unit. That is, either of the two transmission / reception units of the delay adjustment device 1 may be connected to the operation system or the standby system. The delay difference time is set in an appropriate one of the transmission / reception units.

[0059] 5. Effects As described above, according to the redundant line system according to the present embodiment, the delay difference time calculated based on the difference in the signal reception times of the operation system and the standby system is fixedly set in the transmission / reception unit that receives the frame first among the two transmission / reception units, so that the inter-system delay difference can be absorbed. Further, by controlling the transmission enable timing of the frames sent from the buffer at regular intervals, the fluctuations generated in a wireless system or the like can be absorbed. By absorbing the inter-system delay difference and fluctuations, a high service quality can be ensured by seamless switching between systems. The delay adjustment device 1 can absorb the inter-system delay difference and fluctuations even when the two communication paths are configured using arbitrary devices, and seamless switching between systems is possible. Also, since seamless switching is possible, line borrowing from the customer is not required in maintenance work, and reduction of maintenance operation can be achieved.

[0060] 6. Hardware Configuration Example FIG. 5 is a block diagram showing an example of the hardware configuration of the delay adjustment device 1 according to the embodiment. The delay adjustment device 1 includes a control device 90, an operation system communication circuit 95, and a standby system communication circuit 96.

[0061] The control device 90 controls the delay adjustment device 1. For example, the control device 90 includes one or more processors 91 (hereinafter simply referred to as "processor 91") and one or more storage devices 92 (hereinafter simply referred to as "storage device 92"). The processor 91 performs various information processes (including the processes of each part shown in FIG. 2). The processor 91 includes, for example, a CPU. The storage device 92 stores various information necessary for the processes by the processor 91. Examples of the storage device 92 include a volatile memory, a non-volatile memory, an HDD, an SSD, etc. The functions of the control device 90 are realized when the processor 91 executes a control program which is a computer program. The control program is stored in the storage device 92. The control program may be recorded on a computer-readable recording medium. The operation-side buffer 12 and the standby-side buffer 22 in FIG. 2 may be realized by a part of the storage device 92.

[0062] The operation system communication circuit 95 includes the relay-side interface 11 and the node-side interface 13 in FIG. 2. Note that the operation system communication circuit 95 may include a storage device that functions as the operation-side buffer 12 in FIG. 2. The standby system communication circuit 96 includes the relay-side interface 21 and the node-side interface 23 in FIG. 2. Note that the standby system communication circuit 96 may include a storage device that functions as the standby-side buffer 22 in FIG. 2.

[0063] The embodiments of the present invention have been described above. However, the present invention is not limited to the above-described embodiments, and various modifications can be made and implemented without departing from the spirit of the present invention. In the above-described embodiments, when referring to the number of each element such as the number, quantity, amount, range, etc., the present invention is not limited to the recited number, except when specifically stated or when clearly specified by the principle. Also, the structures and the like described in the above-described embodiments are not necessarily essential to the present invention, except when specifically stated or clearly specified by the principle.

Explanation of Reference Numerals

[0064] 1 Delay adjustment device 2 Upper-level device 3 Lower-level device 4 Relay device 4a Operation system relay device 4b Standby system relay device 10 Operation system interface unit 11 Relay-side interface 12 Operation-side buffer 13 Node-side interface 20 Standby system interface unit 21 Relay-side interface 22 Standby-side buffer 23 Node-side interface 30 Control unit 31 Delay difference detection process 90 Control device 91 Processor 92 Storage device 95 Operation system communication circuit 96 Standby system communication circuit

Claims

1. A delay adjustment device provided in a redundant line system that connects between a transmission device and a reception device through two systems of a first path and a second path, and the first path and the second path transmit the same frame, wherein the delay adjustment device, connects between the transmission device and the reception device, a first transceiver that temporarily stores the frame received from the transmission device via the first path in a first buffer; a second transceiver that temporarily stores the frame received from the transmission device via the second path in a second buffer; and a control unit that controls the transmission enable timing of the frames in the first transceiver and the second transceiver at regular intervals, wherein the control unit, calculates a delay difference time based on a difference between a first reception time of a measurement frame received from the transmission device via the first path and a second reception time of the measurement frame received from the transmission device via the second path, when the first reception time is earlier than the second reception time, sets the delay difference time in the first transceiver, and the larger the delay difference time is, the larger the size of the first buffer is set compared to the second buffer, when the second reception time is earlier than the first reception time, sets the delay difference time in the second transceiver, and the larger the delay difference time is, the larger the size of the second buffer is set compared to the first buffer, wherein the first transceiver, when the delay difference time is set, transmits the frame stored in the first buffer to the reception device at the next transmission enable timing after the delay difference time has elapsed since the frame was received, when the delay difference time is not set, transmits the frame stored in the first buffer to the reception device at the next transmission enable timing after the frame was received, wherein the second transceiver, when the delay difference time is set, transmits the frame stored in the second buffer to the reception device at the next transmission enable timing after the delay difference time has elapsed since the frame was received, when the delay difference time is not set, transmits the frame stored in the second buffer to the reception device at the next transmission enable timing after the frame was received, characterized by the delay adjustment device.

2. A redundant line system that connects between a transmitting device and a receiving device through two systems of a first path and a second path, and the first path and the second path transmit the same frame. It includes a delay adjustment device that connects between the transmitting device and the receiving device. The delay adjustment device A first transceiver that temporarily stores the frame received from the transmitting device via the first path in a first buffer. A second transceiver that temporarily stores the frame received from the transmitting device via the second path in a second buffer. A control unit that controls the transmission enable timing of the frames in the first transceiver and the second transceiver at regular intervals. The control unit Calculates a delay difference time based on the difference between the first reception time of a measurement frame received from the transmitting device via the first path and the second reception time of the measurement frame received from the transmitting device via the second path. When the first reception time is earlier than the second reception time, the delay difference time is set in the first transceiver, and the larger the delay difference time, the larger the size of the first buffer is set compared to the second buffer. When the second reception time is earlier than the first reception time, the delay difference time is set in the second transceiver, and the larger the delay difference time, the larger the size of the second buffer is set compared to the first buffer. The first transceiver When the delay difference time is set, the frame stored in the first buffer is transmitted to the receiving device at the next transmission enable timing after the delay difference time has elapsed since the frame was received. When the delay difference time is not set, the frame stored in the first buffer is transmitted to the receiving device at the next transmission enable timing after the frame is received. The second transceiver When the delay difference time is set, the frame stored in the second buffer is transmitted to the receiving device at the next transmission enable timing after the delay difference time has elapsed since the frame was received. When the delay difference time is not set, the frame stored in the second buffer is transmitted to the receiving device at the next transmission enable timing after the frame is received. A redundant line system characterized by the above.

Images