JP6012908B2 - Relay device - Google Patents

Description

  The present invention relates to a relay device constituting a ring network.

  In the industrial field, Ethernet (registered trademark) has been developed, and a network (hereinafter referred to as an FA network) connecting FA (Factory Automation) devices has been constructed by Ethernet. In the FA network, when realizing high-speed and high-precision motion control, it is sometimes required to transfer a frame for time synchronization at a fixed delay so that there is no delay fluctuation in each node or relay device. is there.

  In the above system, an apparatus that performs store-and-forward transfer control in which a frame is temporarily stored in a memory and then transferred cannot be applied. This is because an Ethernet frame having a variable frame length has different transfer delays depending on the frame length.

  A similar problem exists in a ring network that is a ring network. In other words, even if each device constituting the ring network can transfer with a fixed delay, the delay time depends on the direction of the clockwise or counterclockwise transfer depending on the location of the failed device or the communication line. Different cases occur.

  As a prior art for solving the above problem in a ring network, there is an invention described in Patent Document 1. In the invention described in Patent Document 1, a master station and a plurality of slave stations are connected in a ring shape, and the master station is connected to the slave station through two routes, clockwise and counterclockwise. When a synchronization frame is periodically transmitted, the slave station includes a slave clock, a synchronization effective interval setting unit that sets a synchronization effective interval for each of the two paths, and a synchronization frame reception end time included in the synchronization effective interval Synchronization is performed by providing a synchronization correction unit that corrects the slave clock with the synchronization frame only.

JP 2011-199420 A

  However, in the invention described in Patent Document 1, the master node and the slave node themselves perform time synchronization, and cannot be applied to a network having a configuration via a communication device such as an Ethernet switch. was there.

  The present invention has been made in view of the above, and an object of the present invention is to obtain a relay device that realizes time synchronization in a ring network.

  In order to solve the above-described problems and achieve the object, the present invention is a relay device that constitutes a ring network, and is forwarded from outside the ring network to a clockwise route within the ring network by another relay device. The first queue that holds the frame when a specific frame is received, and the specific queue that is transferred from the outside of the ring network to the counterclockwise path in the ring network by the other relay device Based on the second queue holding the frame, the frame transfer time in the clockwise route from the other relay device to itself, and the frame transfer time in the counterclockwise route from the other relay device to itself Thus, a delay is given to the held frame for the first queue or the second queue, and then output. Characterized in that it comprises a delay adjusting unit for giving instructions, the.

  The relay device according to the present invention has an effect that a ring network capable of time synchronization can be realized because the frame transfer delay time does not change even when path switching occurs in the ring network.

FIG. 1 is a diagram illustrating an example of a communication system configured to include a relay device according to the present invention. FIG. 2 is a diagram showing a logical configuration of the ring network shown in FIG. FIG. 3 is a diagram illustrating an example of a ring network in which a failure has occurred. FIG. 4 is a diagram showing a logical configuration of the ring network shown in FIG. FIG. 5 is a diagram illustrating an example of the transmission processing unit of the switch device. FIG. 6 is a diagram illustrating an example of a reception processing unit of the switch device. FIG. 7 is a diagram illustrating an example of a main part of the switch device to which the master node is connected. FIG. 8 is a diagram illustrating an example of a main part of the switch device to which the slave node is connected. FIG. 9 is a sequence diagram illustrating a delay time measurement operation.

  Embodiments of a relay device according to the present invention will be described below in detail with reference to the drawings. Note that the present invention is not limited to the embodiments.

Embodiment 1 FIG.
FIG. 1 is a diagram illustrating an example of a communication system configured to include a relay device according to the present invention.

  In the communication system shown in FIG. 1, the switch devices 11 to 16 constitute a ring network 1. These switch devices correspond to the relay device according to the present invention, and are connected to other switch devices via an Ethernet cable. A master node 21 is connected to the switch device 11 via an Ethernet cable. Similarly, a slave node 22 is connected to the switch device 12, a slave node 23 is connected to the switch device 13, and a slave node 24 is connected to the switch device 14 via an Ethernet cable. The master node 21 is a node that has the master time of the entire system and periodically transmits a time synchronization frame. When the slave node 22 to the slave node 24 receive the time synchronization frame from the master node 21 sent by the fixed delay transfer via the ring network 1, the master time information included in the received frame is received. Is used to perform time synchronization with the master node 21.

  A ring blocking port 30 is set in the switch device 12. This ring blocking port 30 is a blocking port in Ethernet ring protection (ERP) defined by ITU-T G.8032. User frames are not transferred from this blocked port. That is, the logical configuration of the ring network 1 shown in FIG. 1 is as shown in FIG. In this case, for example, the master node 21 and the slave node 23 are in a state of performing communication via the communication path 41 indicated by a dotted line.

  Here, for example, when a failure 40 as shown in FIG. 3, that is, when a line failure occurs between the switch device 13 and the switch device 14, new ring block ports 31 and ring block ports 32 are set. At the same time, the ring closing port 30 is released. As a result, the logical configuration of the ring network 1 after the failure occurs is as shown in FIG. Further, since the master node 21 and the slave node 23 cannot continue the communication via the communication path 41 illustrated in FIG. 2, the master node 21 and the slave node 23 are switched to communicate via the communication path 42 indicated by the dotted line in FIG. 4.

  Next, the configuration of the switch device 13 will be described. In addition, although the switch apparatus 13 is demonstrated here as an example, it is the same also about another switch apparatus.

  FIG. 5 is a diagram illustrating an example of each component (transmission processing unit) that processes a frame to be transmitted to the master node 21 among the components of the switch device 13. As shown in FIG. 5, the transmission processing unit includes delay adjustment queues 201 and 205, fixed delay queues 202 and 206, normal queues 203 and 207, read control units 204 and 208, and delay adjustment unit 209. Prepare.

  The delay adjustment queue 201 queues the fixed delay frame for the master node 21 input from the slave node 23 (that is, the fixed delay frame transmitted / received between the slave node 23 connected to itself and the master node 21). To do. The fixed delay queue 202 queues fixed delay frames input from other switch devices constituting the ring network. The normal queue 203 queues a frame (hereinafter referred to as a normal frame) that does not need to be transferred with a fixed delay among frames input from the slave node 23. The read control unit 204 reads frames from the delay adjustment queue 201, the fixed delay queue 202, and the normal queue 203 in a predetermined order and outputs them to the clockwise side (switch device 12). The above are the components that process the frames transferred clockwise.

  The delay adjustment queue 205 queues a fixed delay frame for the master node 21 input from the slave node 23. The fixed delay queue 206 queues fixed delay frames input from other switch devices constituting the ring network. The normal queue 207 queues normal frames. The read control unit 208 reads frames from the delay adjustment queue 205, the fixed delay queue 206, and the normal queue 207 in a predetermined order and outputs them to the counterclockwise side (switch device 14). The above is a component for processing a frame to be transferred counterclockwise.

  The delay adjustment unit 209 sets a delay time for the delay adjustment queue 201 and the delay adjustment queue 205, and the delay time is set regardless of whether the frame is transferred through a clockwise route or a counterclockwise route. Is fixed (so that the delay time until reaching the master node 21 is the same).

  FIG. 6 is a diagram illustrating an example of each component (reception processing unit) that processes a frame transmitted from the master node 21 among the components of the switch device 13. As shown in FIG. 6, the reception processing unit includes frame transfer units 301 and 302, delay adjustment queues 303 and 304, a normal queue 305, a read control unit 306, and a delay adjustment unit 307.

  The frame transfer unit 301 receives a frame from a clockwise route (receives a frame from the switch device 14). When the received frame is destined for the slave node 23 under its control, it is determined whether it is a fixed delay frame or a normal frame. If it is a fixed delay frame, it is transferred to the delay adjustment queue 303, and if it is a normal frame, it is transferred to the normal queue 305. To do. If the received frame is not addressed to the slave node 23, the frame is transferred to a clockwise route (transferred to the switch device 12). On the other hand, the frame transfer unit 302 receives a frame from a counterclockwise path (receives a frame from the switch device 12). When the received frame is addressed to the slave node 23 under its control, it is determined whether it is a fixed delay frame or a normal frame, and if it is a fixed delay frame, it is transferred to the delay adjustment queue 304, and if it is a normal frame, it is transferred to the normal queue 305 To do. If the received frame is not addressed to the slave node 23, it is transferred to a counterclockwise path (transferred to the switch device 14).

  The delay adjustment queue 303 queues fixed delay frames transmitted through a clockwise route, and the delay adjustment queue 304 queues fixed delay frames transmitted through a counterclockwise route. The normal queue 305 queues normal frames.

  The read control unit 306 reads frames from the delay adjustment queue 303, the delay adjustment queue 304, and the normal queue 305 in a predetermined order and outputs them to the slave node 23. The delay adjustment unit 307 sets a delay time for the delay adjustment queues 303 and 304, and when the frame from the master node 21 is transferred through either the clockwise route or the counterclockwise route. Also adjust the delay time to be fixed.

  For convenience of explanation, each of the transmission processing unit and the reception processing unit includes a delay adjustment unit. However, only one delay adjustment unit is provided outside the transmission processing unit and the reception processing unit, and one delay adjustment unit is provided. You may make it instruct | indicate the delay time given to a frame with respect to the delay adjustment queues 201 and 205 of a transmission process part, and the delay adjustment queues 303 and 304 of a reception process part.

  Next, the operation of the switch device according to this exemplary embodiment will be described. As an example, the operation of the switch device 13 will be described. Here, the switch device 13 has a delay time to itself when the switch device 11 to which the master node 21 is connected transmits a frame in a clockwise direction (until the switch device 11 reaches itself after the frame is transmitted). The delay time when the switch device 11 transmits the frame counterclockwise is assumed to be known in advance. Note that the delay time to the switch device 13 when the switch device 11 transmits the frame clockwise is the same as the delay time to the switch device 11 when the switch device 13 transmits the frame counterclockwise. The switch device 13 measures the delay time when the delay time is predicted to change, such as when a ring network is constructed, when the number of switch devices constituting the ring network fluctuates, or when a failed switch device is replaced. Control frames are transmitted and received in each path, and the delay time in each path is measured. In the present embodiment, the delay time in the clockwise path from the switch device 13 to the switch device 11 is 2 μs, and the delay time in the counterclockwise path is 4 μs.

  In this case, the delay time in the clockwise route is 2 μs shorter than the delay time in the counterclockwise route. Therefore, in the transmission processing unit illustrated in FIG. 5, the delay adjustment unit 209 receives and holds a fixed delay frame to be transmitted to the master node 21 through the clockwise path among the frames input from the slave node 23. A fixed delay transfer of 2 μs is instructed to the queue 201. That is, it instructs to output after adding a delay of 2 μs. The delay adjustment queue 205 is not instructed to add a delay. On the other hand, in the reception processing unit illustrated in FIG. 6, the delay adjustment unit 307 instructs the delay adjustment queue 304 that receives and holds the frame transferred through the counterclockwise path to perform a fixed delay transfer of 2 μs. .

  As a result, the switch device 13 can fix the delay time until the frame transmitted from the slave node 23 reaches the master node 21 regardless of the transfer path. Further, the delay time until the frame transmitted from the master node 21 reaches the slave node 23 can be fixed regardless of the transfer path.

  In the network having the configuration shown in FIG. 2, the fixed delay frame transmitted from the slave node 23 is transferred to the master node 21 in 4 μs. On the other hand, in the state at the time of failure shown in FIG. 4, the fixed delay frame transmitted from the slave node 23 is added with a delay of 2 μs in the delay adjustment queue 201 of the switch device 13, so Thus, the data is transferred in the same 4 μs counterclockwise direction. Further, the fixed delay frame from the master node 21 to the slave node 23 reaches the switch device 13 in the clockwise direction in the normal state (the state shown in FIG. 2 before the failure occurs), and the delay in this case The time is 4 μs. On the other hand, when a failure occurs (the state shown in FIG. 4), the frame arrives at the switch device 13 with a delay time of 2 μs, and the same transfer time of 4 μs is obtained by adding a delay of 2 μs in the delay adjustment queue 304. It becomes.

  The operation of the switch device 13 described in the present embodiment is an operation when the delay adjustment is not performed in the switch device 11 to which the master node 21 is connected. Therefore, the switch device 13 is configured to adjust the delay time both when a frame is transmitted to the switch device 11 and when a frame is received from the switch device 11. When the switch device 11 has a function of adjusting the delay time, the switch device 13 may adjust the delay time in either the fixed delay frame transmission process or the reception process. For example, when the switching device 11 performs the above-described delay addition of 2 μs in the reception processing of the fixed delay frame, the switching device 13 does not adjust the delay time in the frame transmission processing. However, when the switch device 11 to which the master node 21 is connected performs delay adjustment, the delay time to each switch device to which the slave node is connected is managed, and a delay having a different value for each frame transmission destination switch device. Therefore, the processing becomes complicated and the load increases. For this reason, it is desirable that each switch device to which the slave node is connected performs delay adjustment both at the time of transmission and at the time of reception.

  Although the switch device 13 has been described, the same applies to other switch devices (switch devices 12, 14, etc.) to which the slave node is connected.

  As described above, the switch device according to the present embodiment holds in advance information on the difference in delay time in the ring network between when the fixed delay frame is transmitted clockwise and when it is transmitted counterclockwise. We decided to adjust the delay according to the frame transfer path. Specifically, a delay is added when a fixed delay frame is transmitted through a path with a small delay and when a fixed delay frame is received through a path with a small delay. Thereby, even when a failure occurs in the ring network and the path is switched, the fixed delay transfer of the fixed delay frame can be continued. In the conventional technology, the master node or slave node itself performed the operation for time synchronization. However, fixed delay transfer is possible even through a communication device such as an Ethernet switch, realizing time synchronization. it can.

  When synchronization between the local time managed by each slave node and the master time managed by the master node is realized, each switch device sends a time synchronization frame sent to each slave node by the master node. May be transferred with a fixed delay. That is, each switch device may adjust the delay at least when receiving a time synchronization frame to be transferred to a slave node connected to the switch device.

  Although the present embodiment has been described on the assumption that a time synchronization frame is transferred with a fixed delay, this embodiment can also be applied to a case where a frame other than a time synchronization frame is transferred with a fixed delay.

Embodiment 2. FIG.
In the first embodiment, the description has been made on the assumption that the switch device 11 to which the master node 21 is connected knows in advance the transfer delay time in each route (clockwise route, counterclockwise route). Next, an embodiment that dynamically acquires a transfer delay time to realize fixed delay transfer will be described. The overall configuration of the communication system is the same as that of the first embodiment (see FIG. 1).

  FIG. 7 is a diagram illustrating an example of a main part of the switch device 11 to which the master node 21 is connected. The switch device 11 naturally includes the same components as the transmission processing unit and the reception processing unit (see FIGS. 5 and 6) included in the switch device 13 described in the first embodiment. In FIG. 7, the description is omitted to simplify the description. In FIG. 7, only the components related to the operation of dynamically acquiring the transfer delay time are shown.

  As illustrated in FIG. 7, the switch device 11 includes a synchronization frame snoop unit 402, a delay measurement unit 403, and a switch unit 404 as a configuration for acquiring the transfer delay time. Every time a frame is received, the synchronization frame snoop unit 402 snoops the received frame to check whether it is a synchronization frame addressed to a slave node. The delay measurement unit 403 measures the delay time in each path based on the snooping result in the synchronization frame snoop unit 402. The switch unit 404 transmits and receives frames to and from other switch devices. For example, a delay measurement request or a delay measurement answer, which will be described later, is transmitted / received.

  In the switch device 11 illustrated in FIG. 7, a port (not shown) to which the master node 21 is connected receives a synchronization frame 401 that the master node 21 periodically transmits. In this case, the synchronization frame snoop unit 402 detects that the master node 21 is connected to itself (switch device 11) and the synchronization frame 401 is periodically transmitted. When detecting that the synchronization frame 401 is periodically transmitted from the master node 21, the synchronization frame snoop unit 402 notifies the delay measurement unit 403 to that effect. Upon receiving this notification, the delay measuring unit 403 instructs the switch unit 404 to transfer to the switch unit 404 when receiving a frame for measuring the delay time.

  FIG. 8 is a diagram illustrating an example of a main part of the switch device 13 to which the slave node 23 is connected. As in FIG. 7, the same components as those of the transmission processing unit and the reception processing unit (see FIGS. 5 and 6) described in the first embodiment are not described for the sake of simplicity.

  As illustrated in FIG. 8, the switch device 13 includes a switch unit 501, a synchronization frame snoop unit 503, and a delay measurement unit 504. As is clear from a comparison between FIGS. 8 and 7, the basic configurations of the switch device 13 and the switch device 11 are the same. However, the operation of each component is different. That is, each switch device performs different operations when the master node is connected and when the slave node is connected.

  In the switch device 13 to which the slave node 23 is connected, the switch unit 501 receives the synchronization frame transmitted from the master node 21 from the clockwise route or the counterclockwise route, and then sends it to the synchronization frame snoop unit 503. Forward. When receiving the synchronization frame from the switch unit 501, the synchronization frame snoop unit 503 instructs the delay measurement unit 504 to measure the delay time. When receiving the delay time measurement instruction, the delay measuring unit 504 measures the delay time between the master node 21 and the switch device 11 connected in accordance with the sequence shown in FIG. That is, the delay measuring unit 504 transmits and receives a frame for measuring the delay time to and from the switch device 11 according to the sequence of FIG. Specifically, a delay measurement request is transmitted, and a delay measurement answer is received as a response thereto. The frame transmission / reception according to the sequence of FIG. 9 is performed in both the clockwise route and the counterclockwise route. At this time, the synchronization frame snoop unit 503 performs control so that the synchronization frame 502 is not transferred to the slave node side until the delay time measurement by the delay measurement unit 504 is completed. When the delay time measurement is completed, the delay measurement unit 504 notifies the synchronization frame snoop unit 503 to that effect, and the synchronization frame snoop unit 503 receiving the notification transfers the synchronization frame 502 to the slave node side. Resume operation.

  The delay time measurement operation by the delay measurement unit 504 will be described in detail with reference to FIG.

As shown in FIG. 9, first, the delay measurement unit 504 of the switch device 13 holds the local time (T0) and uses the frame to which the information of the local time (T0) is added as a delay measurement request. Send to. Next, in the switch device 11 that has received the delay measurement request, the delay measurement unit 403 returns a frame to which the internal processing time (Tm) is added as a delay measurement answer. The switch device 11 transmits a delay measurement answer in the direction in which the delay measurement request is received. That is, when a delay measurement request is received through a clockwise route, the switch device 11 transmits a delay measurement answer through a counterclockwise route. For example, when receiving a delay measurement request from the switch device 13 via the switch device 12, the switch device 11 returns a delay measurement answer via the switch device 12. When receiving the delay measurement answer, the delay measurement unit 504 of the switch device 13 confirms the reception time (T1) and calculates the delay time Td according to the following equation (1). The delay measuring unit 504 notifies the delay adjusting unit 209 and the delay adjusting unit 307 (see FIGS. 5 and 6) of the calculated delay time Td and holds them, or holds them in a storage unit not shown. The delay measurement unit 504 may hold the delay time Td and notify it in response to a request from the delay adjustment unit 209 or the delay adjustment unit 307.
Td = (Ts−Tm) / 2 = (T1−T0−Tm) / 2 (1)

  The delay measuring unit 504 calculates the delay time Td for both the clockwise route and the counterclockwise route.

  As described above, according to the present embodiment, the switch device automatically detects the master node and measures the delay time in both the clockwise route and the counterclockwise route. Even when a failure occurs in the network, fixed delay transfer can be realized.

  In addition, by performing the measurement operation of the delay time Td described in the present embodiment at a constant period, the delay time Td that cannot be achieved in the first embodiment can be updated, and even if the delay time changes, a fixed delay is possible. The transfer can be continued.

  In order to realize this embodiment, the ring blocking port 30 transfers the synchronization frame in the same manner as the control frame of the Ethernet ring, and the switch device connected to the master node goes around the ring. When the received synchronization frame is received, it is discarded.

  As described above, the relay apparatus according to the present invention is useful when realizing fixed delay transfer of frames in a ring network.

  11, 12, 13, 14, 15, 16 Switch device, 21 Master node, 22, 23, 24 Slave node, 30, 31, 32 Ring blocked port, 40 Fault, 41, 42 Communication path, 201, 205, 303, 304 delay adjustment queue, 202, 206 fixed delay queue, 203, 207, 305 normal queue, 204, 208, 306 read control unit, 209, 307 delay adjustment unit, 301, 302 frame transfer unit, 401, 502 synchronization frame, 402, 503 Frame snoop unit for synchronization, 403, 504 Delay measurement unit, 404, 501 Switch unit.

Claims (7)

A relay device constituting a ring network,
A first queue that holds a specific frame transferred by another relay device from outside the ring network to a clockwise route in the ring network;
A second queue that holds a specific frame transferred from the outside of the ring network to the counterclockwise path in the ring network by the other relay device;
Based on the frame transfer time on the clockwise route from the other relay device to itself and the frame transfer time on the counterclockwise route from the other relay device to itself, the first queue or the first queue A delay adjustment unit that instructs the queue of 2 to output after delaying the held frame;
A relay device comprising: The required time from when the other relay device transmits the specific frame to the clockwise route until it is stored in the first queue and output from the first queue is defined as the first required time. The time required from when the other relay device transmits the specific frame to the counterclockwise route until it is stored in the second queue and output from the second queue is the second time required. When
The delay adjusting unit gives an instruction to the first queue or the second queue so that the first required time is equal to the second required time. Relay device.   2. The first queue and the second queue hold a frame which is a transmission source of a master node managing a master time and needs to be transferred with a fixed delay. 2. The relay device according to 2. A third queue that holds the frame when it receives a specific frame transferred from the ring network by itself and transferred to the clockwise route in the ring network, and transferred from the ring network by the other relay device;
A fourth queue that holds a frame when it is transferred from outside the ring network, when the other relay device receives the specific frame that is transferred to the counterclockwise route in the ring network, and forwarded outside the ring network;
With
The delay adjustment unit, based on the frame transfer time in the clockwise route from the other relay device to itself and the frame transfer time in the counterclockwise route from the other relay device to itself, Instructing the third queue or the fourth queue to output after delaying the held frame.
The relay apparatus according to claim 1, 2, or 3. The time required from when the specific frame is stored in the third queue to the clockwise route to reach the other relay device is defined as a third required time, and is stored in the fourth queue. When the required time from when the specific frame is stored to the left-handed route to reach the other relay device is the fourth required time,
The delay adjusting unit gives an instruction to the third queue or the fourth queue so that the third required time is equal to the fourth required time. Relay device.   6. The third queue and the fourth queue hold a frame that is destined to a master node that manages the master time and that needs to be transferred with a fixed delay. The relay device described. Set the other relay device as the destination of the frame transfer time measurement frame and transmit it to the clockwise route and the counterclockwise route, and transmit the frame transfer time measurement frame to the clockwise route Based on the received time and the time transmitted to the counterclockwise route, the time when the response frame for the frame transfer time measurement frame is received via the clockwise route and the time received via the counterclockwise route, A delay time measuring unit that calculates a frame transfer time in the clockwise route from the other relay device to itself and a frame transfer time in the counterclockwise route from the other relay device to itself;
The relay apparatus according to claim 1, further comprising:

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