JP2007067887A - Communications system, communication device, and line control method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a communications system capable of switching lines without producing data duplication or missing, even when transmitting asynchronous data. <P>SOLUTION: A higher-level device 1 inserts a control information, indicative of a switching timing into data for both of a working line of a switching source and a reserved line of a switching destination, when the status of transmitting data by the working line is switched to a status of transmitting data by the reserved line. A lower-level device 2 adjusts the timing so that the order of data is maintained, and switches from the working line to the reserved line, based on a position of the control information of the working line and the position of the control information of the reserved circuit inserted by the higher-level device 1. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a communication system in which apparatuses are connected by a plurality of lines constituting redundancy.

  Conventionally, a communication system in which devices are connected by a plurality of redundant lines has been used (see, for example, Patent Document 1). Redundant configurations include 1: 1 redundancy and N: 1 redundancy.

  N: 1 redundancy is a configuration in which one protection line is provided for N working lines. By switching the data transmitted on the working line where the failure has occurred to the protection line and transmitting the data, data transmission can be continued even in the event of a failure. Hereinafter, this switching is referred to as “preliminary switching”.

  In N: 1 redundancy, a plurality of working lines share one protection line. Therefore, when a more serious failure occurs in another working line or when the failure of the working line that caused the switching is recovered, It is also conceivable to return the data switched to the line to the original working line. Hereinafter, this switching is referred to as “recovery switching”.

  Also, in general, in line switching, it is desirable to complete the switching without interruption without losing data.

  FIG. 21 is a block diagram showing a configuration of a relay apparatus used in a conventional communication system having an N: 1 redundant line. This relay apparatus is configured to have N: 1 redundancy on both the front and rear lines.

  Referring to FIG. 21, the relay device includes a switching unit 905, selection circuits 911 to 91N, delay circuits 921 to 92N, main signal interfaces 931 to 93N, buffer memory units 941 to 94N, a phase adjustment unit 91S, a delay circuit unit 92Y, It has a main signal interface section 93Y and a buffer memory section 94Y.

  The data of the working line # 1 is input as a main signal to the selection circuit unit 911 via the delay circuit unit 921 and directly. The selection circuit unit 911 selects and outputs either the data input via the delay circuit unit 921 or the directly input data. Usually, the directly input data is selected. A main signal from the selection circuit unit 911 is input to the switching unit 905 via the main signal interface 931 and the buffer memory unit 941.

  Data writing to the buffer memory unit 941 is controlled by a write control signal from the main signal interface 931. Further, reading of data from the buffer memory unit 941 is controlled by a read control signal from the main signal interface 931. The main signal interface 931 generates a write control signal and a read control signal from the reference frame of the main signal.

  Similarly, the data on the working line #N is input as a main signal to the selection circuit unit 91N via the delay circuit unit 92N or directly. The main signal is input from the selection circuit unit 91N to the switching unit 905 via the main signal interface 93N and the buffer memory unit 94N.

  In addition, the data on the standby system line is input to the delay circuit unit 92Y as a main signal. The main signal is input from the delay circuit unit 92Y to the switching unit 905 via the main signal interface 93Y and the buffer memory unit 94Y.

  The delay circuit unit 92Y delays the data of the main signal in accordance with an instruction from the phase adjustment unit 91S when switching any of the working lines on the upstream side (upper side) of the relay apparatus to the protection line.

  The phase adjustment unit 91S delays the standby main signal in accordance with the main signal of the active line to be switched to the standby line, so that the standby buffer memory unit 94Y reads data at the same timing as the active line. To be able to.

  The buffer memory unit 94Y uses the read control signal from the main signal interface corresponding to the active line to be switched to the protection line to match the read timing with that of the active buffer memory part.

  The switching unit 905 outputs the main signal data from each higher-order line of the relay apparatus to a desired subsequent (lower-order) line.

  Next, as an example, the operation when the data on the higher-side working line # 1 is switched to the protection line will be described.

  As a normal state, the main signal from the upper working system line # 1 is input to the selection circuit unit 911 and the delay circuit 921. The selection circuit unit 911 selects whether or not to delay the active main signal, but here it is not delayed. Therefore, the working main signal is directly input to the main signal interface unit 931. The working main signal input to the main signal interface unit 931 is temporarily stored in the buffer memory unit 941 by a write control signal from the main signal interface unit 931.

  On the other hand, the main signal from the protection line is input to the delay circuit unit 92Y. The delay circuit unit 92Y receives the main signal from the standby system line under the control of the phase adjustment unit 91S so that the data in the buffer memory unit 94Y can be normally read out at the same timing as the active system # 1 to be switched. Delay.

  The standby main signal delayed by the delay circuit 92Y is input to the main signal interface unit 93Y. The main signal interface unit 93Y sends a write control signal to the buffer memory unit 94Y together with the input standby system main signal, and temporarily records the data of the standby system main signal in the buffer memory unit 94Y.

  The active main signal and the standby main signal stored in each of the buffer memory units 941 and 94Y are read at the same timing by the read control signal generated from the reference frame by the main signal interface unit 931 of the active # 1. It is. There is no time difference between the active main signal and the standby main signal read from the buffer memory units 941 and 94Y at the same timing. Therefore, the switching unit 905 can perform switching without interruption between the main signal of the active system # 1 and the standby system main signal.

With such a configuration, it is possible to switch and receive the data transmitted by switching the working line from the working line to the protection line by the upper apparatus without interruption in the lower apparatus.
JP-A-4-266233

  However, the conventional relay apparatus matches the read timings of the two buffer memory units with the read control signal generated from the reference frame. Therefore, it is effective for lines that transmit frame-synchronized continuous signals, but for lines where asynchronous data with varying delays is transmitted within a frame, it is ensured that there is no data duplication or lossless switching. I can't.

  An object of the present invention is to provide a communication system, a communication apparatus, and a line control method capable of switching lines without causing duplication or omission of data even when asynchronous data is transmitted.

In order to achieve the above object, a communication system of the present invention is a communication system using a redundant configuration consisting of a working line and a protection line for connection between devices,
When switching from a state in which data is transmitted on the working line to the protection line, a host device that inserts control information indicating switching timing into data of both the switching source working line and the switching destination protection line and transmits the control information;
It is possible to receive both data transmitted from the host device on the working line and data transmitted on the protection line, and the position of the control information of the working line inserted by the host device and the control of the protection line inserted by the host device. A subordinate device that adjusts the timing so as to maintain the data order based on the position of the information and switches from the working line to the protection line.

  According to the present invention, when line switching is performed, the upper apparatus inserts control information indicating the switching timing into the data of both the switching source and switching destination lines, and the lower apparatus transmits control information from the switching source line. As the order is restored by adjusting the timing of the data of the switching source line and the data of the switching destination line based on the position where the control information from the switching destination line is inserted, asynchronous data is transmitted. Also, line switching can be performed without causing duplication or omission of data. In addition, according to the present invention, since the higher-level device and the lower-level device also use the protection line for transmission and reception of control information, even if the working line becomes incapable of communicating data due to a failure, it shares information for control with each other. Therefore, highly reliable line switching can be performed.

In addition, the host device controls the switching position corresponding to the data of the working line and the data of the protection line so that the data before the control information of the working line and the data after the control information of the protection line are continuous. Insert each information,
Subordinate device is
If the control information from the working line arrives before the control information from the protection line, the acquisition of data from the working line is stopped before the control information from the working line. When control information arrives, start acquiring data from the protection line,
If the control information from the protection line arrives before the control information from the working line, temporarily store the data after the protection information of the protection line and receive the control information from the working line. The data of the reserved line that has been held may be connected after the data from the working line before the control information.

In addition, the higher-order device inserts a predetermined number of the control information continuously after the switching position of the working line,
When the subordinate apparatus cannot receive the control information from the working line even after a predetermined time has elapsed since receiving the control information from the protection line, the data of the protection line starting from the stored data It is good also as switching to.

  According to this, even if the quality of the working line is lowered to such an extent that the transmission of control information is hindered, the switching can be reliably completed by the retransmission of the control information and the switching due to timeout.

In addition, in switching to return to the original working line from the state where switching to the protection line is performed,
The host device inserts control information indicating switching timing into data of both the protection line of the switching source and the working line of the switching destination, and transmits the data.
The subordinate apparatus performs timing so as to maintain the order of data based on the position of the control information of the working line inserted by the upper apparatus and the position of the control information of the protection line inserted by the upper apparatus. May be switched to switch from the protection line to the working line.

In addition, the lower-level device performs an error check on the working line, and sends control information for instructing switching of the working line, generated based on the detected error level, to the higher-level device via the protection line. Send
When the upper apparatus receives the control information from the lower apparatus, the upper apparatus may start switching of the working line instructed by the control information.

In addition, there are a plurality of working lines and one protection line, and the plurality of working lines and one protection line constitute N: 1 redundancy,
The lower-level device may check each of the plurality of working lines and select a working line having the highest error level as a switching target.

  According to this, when detecting a failure in a plurality of working lines, the lower level apparatus selects the line with the highest error level and instructs the higher order apparatus to switch the line, so that the working line with the highest error level is reserved. It is possible to switch to the line and maintain the operation of the working line as much as possible.

  In addition, the lower-level device switches to the protection line when an error having a higher level than the error level of the working line occurs in a state where any of the working lines is switched to the protection line. After the working line is restored, the working line in which a high level error has occurred may be switched to the protection line.

  According to this, when a failure with a higher error level occurs in another working line while a certain working line is in standby switching, the lower-level device performs standby switching for the working line in which a failure with a higher error level occurs. Therefore, the working line with the highest error level can be switched over, and the working line operation can be maintained as much as possible.

In addition, the higher-level device pseudo-generates control information indicating the error level of the working line and transmits the control information to the lower-level device via the working line,
When the lower level device receives control information indicating the error level from the working line, the lower level device may transmit control information instructing switching of the working line to the higher level device via the protection line.

  According to this, in addition to the switching based on the error state detected by the lower level device, the lower level device can also start switching based on the input of control information from the higher level device, so it is necessary to add large special equipment to each device. Remote switching control can be executed.

  According to the present invention, when line switching is performed, the upper apparatus inserts control information indicating the switching timing into the data of both the switching source and switching destination lines, and the lower apparatus transmits control information from the switching source line. As the order is restored by adjusting the timing of the data of the switching source line and the data of the switching destination line based on the position where the control information from the switching destination line is inserted, asynchronous data is transmitted. Also, line switching can be performed without causing duplication or omission of data.

  Embodiments for carrying out the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a block diagram showing a schematic configuration of a communication system according to the present embodiment. Referring to FIG. 1, the communication system includes an upper relay device 1 and a lower relay device 2. The upper relay apparatus 1 and the lower relay apparatus 2 are connected to N active lines # 1 to #N by one protection line. These lines constitute N: 1 redundancy, and when a failure occurs in any of the working lines, the data transmitted on the line is switched to the protection line. The data on the working line and the protection line are transmitted asynchronously to the frame, and in this embodiment, are transmitted by packets.

  FIG. 2 is a block diagram illustrating a configuration of the upper relay apparatus and the lower relay apparatus illustrated in FIG. Here, a configuration related to data in a direction from the higher-level relay device 1 to the lower-level relay device 2 is shown. Here, as an example, there are three active lines.

  Referring to FIG. 2, the upper relay apparatus 1 includes output switching units 10 to 12, a selection function unit 13, transmission function units 14 to 16, a reception function unit 17, and a transmission function unit 18. In addition, the lower relay apparatus 2 includes reception function units 20 to 23 and a transmission function unit 24.

  The output switching unit 10 of the higher-level relay apparatus 1 receives data on the higher-order side (left side in the drawing) line # 0 and sends the received data to the transmission function unit 14 in a normal state. Normal time refers to a state where switching to the protection line is not performed.

  When the output switching unit 10 receives a control packet indicating “preliminary switching” of the line # 0 from the reception function unit 17, the output switching unit 10 switches the output destination of the reception data to the selection function unit 13, and receives the control data as the head. Is sent to the selection switching unit 13. At the same time, the output switching unit 10 continuously sends a control packet indicating “preliminary switching” of the line # 0 to the transmission function unit 14 instead of the reception data.

  The transmission function unit 14 transmits the data or control packet from the output switching unit 10 to the lower level relay apparatus 2 via the line # 0.

  The output switching units 11 and 12 correspond to the lines # 1 and # 2, respectively, and operate in the same manner as the output switching unit 10 described above. The transmission function units 15 and 16 correspond to the lines # 1 and # 2, respectively, and operate in the same manner as the transmission function unit 14 described above.

  The reception function unit 17 receives data from the lower relay apparatus 2 via the protection line. If there is a control packet in the received data, the reception function unit 17 transmits the control packet to the output switching units 10 to 12.

  The selection function unit 13 selects data from any of the output switching units 10 to 12 and sends it to the transmission function unit 18. Since there is a control packet indicating “preliminary switching” at the head of the data from the output switching units 10 to 12, the selection function unit 13 selects the line when detecting the control packet, and thereafter the data of the line May be sent to the transmission function unit 18. Even if another control packet is detected, the selection function unit 13 does not perform switching.

  The transmission function unit 18 transmits the data from the selection function unit 13 to the lower level relay apparatus 2 via the protection line.

  The reception function unit 20 of the lower level relay apparatus 2 receives data received from the higher level relay apparatus 1 via the higher-order line # 0, or is received by the reception function part 23 via the protection line. One of the sent data is selected and output to the lower line # 0. At normal time, the reception function unit 20 outputs the data received via the upper line # 0 to the lower line # 0.

  The reception function unit 20 also checks for the presence of a data error by using a CRC code (cyclic redundancy check code) included in the packet received from the line # 0. When an error is detected, a control packet indicating an “error state” is generated and sent to the transmission function unit 24.

  When receiving the control packet indicating “standby switching” or the control packet indicating “recovery switching” of the line # 0 from the reception function unit 23 of the protection line, the reception function unit 20 receives the line according to the instruction of the control packet. Switch the selection state. For example, when receiving a control packet indicating “standby switching” of the line # 0 from the reception function unit 23, the reception function unit 20 outputs the data from the reception function unit 23 of the protection line to the lower line # 0. When receiving a control packet indicating “recovery switching” of the line # 0 from the reception function unit 23, the reception function unit 20 outputs the data from the higher-order line # 0 to the lower-order line # 0.

  The reception function units 21 and 22 correspond to the lines # 1 and # 2, respectively, and operate in the same manner as the reception function unit 20 described above.

  The reception function unit 23 receives data from the higher-level relay device 1 via the protection line and sends the data to the reception function units 20 to 22. At that time, the reception function unit 23 sends not only the control packet but also all received data to the reception function units 20 to 22.

  The transmission function unit 24 obtains the line quality of each of the lines # 0 to # 2 based on the control packet indicating the “error state” from the reception function units 20 to 22, and determines the line to be switched from the line quality to the protection line. to decide. For example, the line with the highest error level (low line quality) may be switched. If it is determined that one of the lines should be switched to the protection line, the transmission function unit 24 generates a control packet indicating “protection switching” of the line, and transmits the control packet to the upper relay apparatus 1 via the protection line. .

  Further, when the transmission function unit 24 detects that the line quality of the lines other than the line under standby switching has deteriorated as compared with the line under standby switching, the transmission function unit 24 “restores” the line under standby switching to the upper relay apparatus 1. After transmitting a control packet indicating “switching”, a control packet indicating “preliminary switching” of a line with degraded quality is transmitted.

  FIG. 3 is a block diagram illustrating the configuration of the output switching unit 10 of the higher-level relay device 1 and the reception function unit 20 of the lower-level relay device 2 illustrated in FIG. Referring to FIG. 3, the output switching unit 10 of the upper relay apparatus 1 includes an output control unit 101 and a frame detection unit 102. The reception function unit 20 of the lower level relay apparatus 2 includes an ERR (error) detection unit 201, a selection unit 202, and a frame generation unit 203.

  When the frame detection unit 102 receives a control packet related to the line # 0 from the reception function unit 17, the frame detection unit 102 sends the control packet to the output control unit 101.

  The output control unit 101 normally sends data from the upper line # 0 to the transmission function unit 14. However, when receiving the control packet indicating “preliminary switching” from the frame detection unit 102, the output control unit 101 transmits a control packet indicating “preliminary switching” between the packets included in the data from the upper line # 0. The data after the control packet is sent to the selection function unit 13. At the same time, the output control unit 101 does not send data after the control packet to the transmission function unit 14 and continuously sends control packets indicating “preliminary switching”.

  Further, when a control packet indicating “recovery switching” of the line # 0 is received during the preliminary switching of the line # 0, the output control unit 101 receives “in between packets included in the data from the upper line # 0”. A control packet indicating “recovery switching” is inserted, and data after the control packet is sent to the transmission function unit 14. At the same time, the output control unit 101 does not send data after the control packet to the selection function unit 13 but sends only one control packet indicating “recovery switching”.

  The ERR detection unit 201 of the lower relay apparatus 2 checks the error of the data received from the upper relay apparatus 1 via the line # 0 by CRC. When an error is detected, the ERR detection unit 201 notifies the frame generation unit 203 to that effect. Further, the ERR detection unit 203 repairs a bit error that can be corrected by CRC, and transfers the data to the selection unit 202.

  The frame generation unit 203 obtains an error level based on the notification from the ERR detection unit 201, generates a control packet indicating an “error state” according to the error level, and sends the control packet to the transmission function unit 24. The error level can be obtained, for example, by periodically calculating an average value of the number of error detections.

  The selection unit 202 selects and outputs either data received from the higher-level relay apparatus 1 via the line # 0 and the ERR detection unit 201 or data received via the protection line and the reception function unit 23. . At that time, when receiving a control packet of line # 0 from the reception function unit 23, the selection unit 202 performs selection according to the content of the control packet. For example, upon receiving a control packet indicating “standby switching”, the selection unit 202 selects data via the protection line and the reception function unit 23. When receiving the control packet indicating “recovery switching”, the selection unit 202 selects data via the line # 0 and the ERR detection unit 201.

  A detailed operation of the selection unit 202 at the “preliminary switching” will be described.

  A control packet indicating “standby switching” is sent from both the working line # 0 and the protection line.

  When the control packet indicating “standby switching” via the line # 0 and the ERR detection unit 201 arrives at the selection unit 202 before the control packet via the protection line and the reception function unit 23, the selection unit 202 All control packets from the ERR detection unit 201 are discarded, and after receiving the control packet from the reception function unit 23, data excluding the control packet is output to the lower line # 0.

  On the other hand, when the control packet indicating “standby switching” via the protection line and the reception function unit 23 arrives at the selection unit 202 prior to the control packet via the line # 0 and the ERR detection unit 201, the selection unit 202 Temporarily stores the data other than the control packet from the reception function unit 23, and stores the stored data after the arrival of the control packet from the ERR detection unit 201. Output to 0.

  When the selection unit 202 receives a control packet from the reception function unit 23, the selection unit 202 starts counting a timer for a timeout time recorded in the packet. When the timer times out in a state where the control packet from the ERR detection unit 201 has not arrived, the selection unit 202 starts to output the temporarily held data to the line # 0 on the lower side.

  A detailed operation of the selection unit 202 at the time of “recovery switching” will be described.

  A control packet indicating “recovery switching” is also sent from both the working line # 0 and the protection line.

  When the control packet indicating “recovery switching” via the line # 0 and the ERR detection unit 201 arrives at the selection unit 202 prior to the control packet via the protection line and the reception function unit 23, the selection unit 202 The data excluding the control packet is retained by temporarily holding it. Then, after receiving the control packet from the reception function unit 23, the selection unit 202 starts to output the stored data to the lower line # 0.

  On the other hand, when the control packet indicating “recovery switching” via the protection line and the reception function unit 23 arrives at the selection unit 202 prior to the control packet via the line # 0 and the ERR detection unit 201, the selection unit 202 After receiving the control packet from the ERR detector 201, the subsequent data excluding the control packet is output to the lower line # 0.

  Next, in the communication system according to the present embodiment, an operation for switching data transmitted on the working line # 0 to a protection line will be described.

  FIG. 4 is a flowchart showing an operation at the time of preliminary switching in the communication system according to the present embodiment. Referring to FIG. 4, when a failure occurs in the line # 0 between the upper relay apparatus 1 and the lower relay apparatus 2 and an error occurs in communication data (step A1), the ERR in the reception function unit 20 of the lower relay apparatus 2 The detection unit 201 detects an error by CRC (step A2). The ERR detection unit 201 that has detected the error notifies the frame generation unit 203 to that effect.

  Receiving the notification, the frame generation unit 203 generates a control packet indicating an “error state” (step A3) and sends it to the transmission function unit 24.

  FIG. 5 is a diagram illustrating an implementation example of the control packet in the present embodiment. Referring to FIG. 5, the control packet includes a header information part 301 including destination information, a payload information part 302 including significant information, and a CRC information part 303 for error detection / correction.

  The header information portion 301 has an identification bit indicating the type of packet. In the identification bit, “0” indicates a transfer packet, and “1” indicates a control packet.

  The payload information section 302 includes an information bit 304 in addition to a line number bit indicating a line number and a type bit indicating the type of a control packet. In the line number bit, “00” indicates the line # 0, “01” indicates the line # 1, and “10” indicates the line # 2. In the type bit, “01” indicates preliminary switching, “10” indicates recovery switching, and “00” indicates notification of an error state or the like. The control packet indicating the “error state” of the line # 0 generated by the frame generation unit 203 has the identification bit “1”, the line number “00”, and the type bit “00”. The information bit 304 stores information indicating “error level” as shown in FIG. The error level indicates an average value of the number of error detections, and is, for example, the number of CRC error detections per second.

  Returning to the description of FIG. 4, the transmission function unit 24 compares the error level with the other lines # 1 to # 2 and determines whether or not the preliminary switching of the line # 0 is necessary (step A4). If preliminary switching is not necessary, the process returns to step A2.

  If it is determined that the standby switching is necessary, the transmission function unit 24 generates a control packet indicating “standby switching” of the line # 0 (step A5), and transmits the control packet to the higher-level relay apparatus 1 via the backup line. The control packet indicating “preliminary switching” of the line # 0 has the identification bit “1”, the line number bit “00”, and the type bit “01” in FIG. The information bit 304 stores information indicating “time-out time” as shown in FIG. The timeout time is the maximum value of the waiting time in the switching operation of the selection unit 202 described later.

  When receiving the control packet, the reception function unit 17 of the higher-level relay apparatus 1 transfers the control packet to the output switching units 10 to 12 (step A6). The output switching unit 11 of the line # 1 and the output switching unit 12 of the line # 2 ignore this control packet because the line number bits do not match their own line numbers.

  When the frame detection unit 102 in the output switching unit 10 detects a control packet indicating “preliminary switching” of the line # 0 (step A7), the frame detection unit 102 sends the control packet to the output control unit 101. The output control unit 101 that has received the control packet indicating “standby switching” of the line # 0 performs a predetermined standby switching operation.

  FIG. 8 is a diagram for explaining the preliminary switching operation. Referring to FIG. 8, from the top, data of line # 0 input to output control unit 101, data sent from output control unit 101 to selection function unit 13, and data sent from output control unit 101 to transmission function unit 14 It is shown.

  The output control unit 101 outputs data from the higher-order line # 0 to the transmission function unit 14, but when it receives a control packet indicating "preliminary switching" on the line # 0, it selects the subsequent data. Part 13 will be sent. In FIG. 8, data 401 is sent to the transmission function unit 14, and data 402 and later are sent to the selection function unit 13. At that time, the output control unit 101 inserts a control packet 405 indicating “preliminary switching” of the line # 0 before the data 402 for the selection function unit 13, and for the transmission function unit 14, After the data 401, a control packet indicating “preliminary switching” of the line # 0 is continuously transmitted.

  Returning to the description of FIG. 4, when the selection function unit 13 receives a control packet (control packet 405 in FIG. 8) indicating “preliminary switching” of the line # 0 from the output control unit 101, the output control unit 101 of the line # 0. The control packet 405 and the subsequent data are selected and sent to the transmission function unit 18 (step A9). The transmission function unit 18 outputs the data from the selection function unit 13 to the protection line.

  As described above, switching of the upper relay apparatus 1 is performed. Hereinafter, the switching operation of the lower relay apparatus 2 will be described.

  The data sent to the transmission function unit 14 in FIG. 8 is sent to the lower level relay device 2 via the line # 0, and reaches the selection unit 202 via the ERR detection unit 201 in the lower level relay device 2. Also, the data sent to the selection signal function unit 13 in FIG. 8 is sent from the transmission function unit 18 to the lower level relay device 2 via the protection line, and in the lower level relay device 2 via the reception function unit 23, the selection unit. 202 is reached. The switching operation of the lower relay apparatus 2 differs depending on which control packet arrives first.

  FIG. 9 is a flowchart showing the preliminary switching operation of the lower level relay apparatus when the control packet on line # 0 arrives first. FIG. 10 is a diagram for explaining the recovery switching operation of the lower relay apparatus when the control packet on line # 0 arrives first.

  Referring to FIG. 9, upon receiving control packet 406 from line # 0, selection unit 202 stops transferring data from line # 0 with data 401 as a boundary (step B1). Thereafter, control packets are input from the line # 0, but the selection unit 202 does not transfer them to the lower side. Referring to FIG. 10, from the top, data received by the selection unit 202 via line # 0, data received by the selection unit 202 via the protection line, and data transferred to the lower side by the selection unit 202 are shown. Has been. Data 401 from line # 0 is transferred to the lower side, but is not transferred after control packet 406.

  Returning to FIG. 9, next, when receiving the control packet 405 from the protection line, the selection unit 202 starts to transfer data from the protection line to the lower side with the data 402 as the head (step B2). Referring to FIG. 10, data 402 and 403 following the control packet 405 received via the protection line are transferred to the lower side. Thereby, the preliminary switching operation of the lower relay apparatus 2 is completed (step B3).

  FIG. 11 is a flowchart showing the standby switching operation of the lower level relay apparatus when the control packet of the backup line arrives first. FIG. 12 is a diagram for explaining the standby switching operation of the lower level relay apparatus when the control packet for the backup line arrives first.

  Referring to FIG. 11, when receiving the control packet 405 from the protection line, the selection unit 202 starts counting the timer while temporarily holding the subsequent data 402 to 404 (step C1). Referring to FIG. 12, from the top, data received by the selection unit 202 via line # 0, data received by the selection unit 202 via the protection line, and data transferred to the lower side by the selection unit 202 are shown. Has been. Since the control packet 405 has arrived before the control packet 406, the selection unit 202 temporarily holds the data 402 to 404.

  Next, the selection unit 202 determines whether or not a control packet has been received from the line # 0 (step C2). When the control packet 406 is received from the line # 0, the selection unit 202 stops transferring the data from the line # 0 and starts to transfer the data 402 to 404 from the reserved line that has been held to the lower side. (Step C3), the preliminary switching is completed (Step C4).

  If the control packet 406 from line # 0 is not received in step C2, the selection unit 202 next determines whether or not the timer has timed out (step C5). When the error of the line # 0 increases, it is considered that the control packet 406 is not transmitted normally and is lost. Even so, in order to reliably complete the switching, the output control unit 101 of the higher-level relay device 1 continuously transmits the same control packet, and the lower-level relay device 2 performs determination by a timer.

  If the timer has timed out, the selection unit 202 stops transferring the data from the line # 0 and starts transferring the data 402 to 404 from the reserved protection line to the lower side (step C6), The preliminary switching is completed (step C4). If the timer has not timed out in step C5, the selection unit 202 returns to the process of step C2. The reception function unit 21 of the line # 1 and the reception function unit 22 of the line # 2 also receive the control packet 405, but ignore it because the line number bit does not match their own line number.

  Next, in the communication system of this embodiment, an operation when the error level of the line # 1 becomes higher than the line # 0 in a state where the line # 0 is switched to the protection line will be described. In that case, the communication system of the present embodiment performs preliminary switching of line # 1 after performing recovery switching of line # 0.

  FIG. 13 is a flowchart showing an operation when changing a line to be switched for standby in the communication system according to the present embodiment. As an initial state, it is assumed that line # 0 is switched to a protection line and is in operation (step D1). In this state, when a failure occurs in the line # 1 between the higher-level relay device 1 and the lower-level relay device 2 and the data has an error, the reception function unit 21 of the lower-level relay device 2 detects the error by CRC (Step D2). ).

  The reception function unit 21 generates a control packet indicating the “error state” of the line # 1, thereby notifying the transmission function unit 24 of the error level (step D3).

  Upon receiving the control packet, the transmission function unit 24 compares the error level of the line # 0 and the error level of the line # 1, and determines whether or not to change the switch target to the protection line to the line # 1 (step D4). . If it is okay to keep the line # 0 preliminarily switched, the process returns to step D2.

  If the error level of the line # 1 is higher than that of the line # 0, the transmission function unit 24 determines to change the switching target, sends a control packet indicating “recovery switching” of the line # 0, and then the line # 1. A control packet indicating “preliminary switching” is transmitted (step D5).

  The reception function unit 17 of the higher-level relay apparatus 1 transfers the control packet received via the protection line to the frame detection unit 102 of the output switching unit 10 (step D6).

  Upon receiving the control packet indicating the “recovery switching” of the line # 0 via the protection line, the output switching unit 10 performs the recovery switching operation of the line # 0 (step D7). Further, the output switching unit 11 that has received the control packet indicating “standby switching” of the line # 1 via the protection line performs the operation of the protection switching of the line # 1 (step D8).

  FIG. 14 is a diagram for explaining the operations of the output switching unit of line # 0 and the output switching unit of line # 1 that have received a control packet in the operation of FIG. Referring to FIG. 14, data input from line # 0 to output switching unit 10, data sent from output switching unit 10 to selection function unit 13, and data sent from output switching unit 10 to transmission function unit 14 from above. , Data input from the line # 1 to the output switching unit 11, data sent from the output switching unit 11 to the selection function unit 13, data sent from the output switching unit 11 to the transmission function unit 15, and transmission function from the selection function unit 13 Data sent to the unit 18 is shown.

  When the output switching unit 10 receives a control packet indicating “recovery switching” on the line # 0 from the reception function unit 17, the output switching unit 10 transmits a control packet 505 indicating “recovery switching” after the data 501 to the selection function unit 13. To stop sending data. Further, the output switching unit 10 sends a control packet 506 indicating “recovery switching” to the transmission function unit 14, and thereafter starts to transfer the data 502 to 504 of the line # 0.

  When the output switching unit 11 receives a control packet indicating “preliminary switching” of the line # 1 from the reception function unit 17, the output switching unit 11 transmits a control packet 605 indicating “preliminary switching” to the selection function unit 13. Transfer of data 603 to 604 of line # 1 is started. Further, the output switching unit 11 sends one control packet 606 indicating “preliminary switching” after the data 602 to the transmission function unit 15.

  As a result of these operations, the selection function unit 13 stops transferring the data from the line # 0 at the data 501 and starts transferring the data from the line # 1 from the data 603 (step D9).

  The standby switching operation of the reception function unit 21 in the line # 1 of the lower level relay apparatus 2 is the same as the flowcharts shown in FIGS.

  On the other hand, the data sent to the transmission function unit 14 in FIG. 14 is sent to the lower level relay device 2 via the line # 0, and reaches the selection unit 202 in the lower level relay device 2. Further, the data sent to the selection signal function unit 13 of FIG. 14 is sent from the transmission function unit 18 to the lower level relay device 2 via the protection line, and in the lower level relay device 2 via the reception function unit 23, the selection unit. 202 is reached. The restoration switching operation of the lower level relay apparatus 2 differs depending on which control packet arrives first.

  FIG. 15 is a flowchart showing the recovery switching operation of the lower level relay apparatus when the control packet on line # 0 arrives first. FIG. 16 is a diagram for explaining the recovery switching operation of the lower relay apparatus when the control packet on line # 0 arrives first.

  Referring to FIG. 15, upon receiving control packet 506 from line # 0, selection unit 202 temporarily retains data after data 502 (step E1). Referring to FIG. 16, from the top, data received by the selection unit 202 via the protection line, data received by the selection unit 202 via the line # 0, and data transferred by the selection unit 202 to the lower side are shown. Has been. Data 502 to 504 after receiving the control packet 506 is not immediately transferred to the downstream side.

  Returning to FIG. 15, next, when the selection unit 202 receives the control packet 505 from the protection line, the selection unit 202 stops the transfer of data from the protection line thereafter and the line # 0 from the stored data 502 to 504. Starts to be transferred to the lower side (step E2). Referring to FIG. 16, the transfer of the protection line data is stopped at the data 501 by the reception of the control packet 505, and thereafter, the data 502 to 504 from the line # 1 are transferred. Thereby, the restoration switching operation of the lower relay apparatus 2 is completed (step E3).

  FIG. 17 is a flowchart showing the recovery switching operation of the lower relay apparatus when the control packet for the protection line arrives first. FIG. 18 is a diagram for explaining the recovery switching operation of the lower relay apparatus when the protection packet for the protection line arrives first.

  Referring to FIG. 17, when receiving the control packet 505 from the protection line, the selection unit 202 stops the subsequent data transfer and starts counting the timer (step F1). Referring to FIG. 18, from the top, data received by the selection unit 202 via the protection line, data received by the selection unit 202 via the line # 1, and data transferred to the lower side by the selection unit 202 are shown. Has been. Since the control packet 505 arrives before the control packet 506, the selection unit 202 stops transferring data from the protection line.

  Next, the selection unit 202 determines whether or not a control packet has been received from the line # 0 (step F2). If the control packet 506 is received from the line # 0, the selection unit 202 starts to transfer the data 502 to 503 from the line # 1 to the lower side (step F3) and completes the preliminary switching (step F4).

  If the control packet 506 from the line # 0 is not received in step F2, the selection unit 202 next determines whether or not the timer has timed out (step F5).

  If the timer has timed out, the selection unit 202 starts data transfer from the line # 0 (step F6) and completes the recovery switching (step F4). If the timer has not timed out in step F5, the selection unit 202 returns to the process in step F2. The reception function unit 21 of the line # 1 and the reception function unit 22 of the line # 2 also receive the control packet 405, but ignore it because the line number bit does not match their own line number.

  As described above, according to the present embodiment, when line switching is performed, the upper relay apparatus 1 inserts a control packet indicating the switching timing into the data of both the switching source and switching destination lines. Then, based on the position where the control packet from the switching source line and the control packet from the switching destination line are inserted, the subordinate relay device 2 determines the timing of the switching source line data and the switching destination line data. Adjust to restore order. Therefore, even if asynchronous data is transmitted, the line can be switched without causing data duplication or omission.

  Further, according to this embodiment, the upper relay apparatus 1 and the lower relay apparatus 2 transmit and receive control packets using the protection line. Therefore, even if the working line is in a state where data cannot be communicated due to a failure, information for control can be shared with each other, and line switching with high reliability can be performed.

  Further, according to the present embodiment, when detecting a failure in a plurality of working lines, the lower relay apparatus 2 selects a line with the highest error level and instructs the upper relay apparatus 1 to perform preliminary switching of the lines. Therefore, the working line with the highest error level can be switched to the protection line, and the operation of the working line can be maintained as much as possible.

  Further, according to the present embodiment, when a failure with a higher error level occurs in another active line in a state where a certain active line is switched to standby, the lower-level repeater 2 causes a failure with a high error level. The existing working line is the target of standby switching. Therefore, the working line with the highest error level can be switched over, and the working line can be maintained as much as possible.

  Another embodiment of the present invention will be described. The communication system according to another embodiment has the same configuration as that shown in FIGS.

  FIG. 19 is a block diagram illustrating configurations of the output switching unit 10 of the higher-level relay device 1 and the reception function unit 20 of the lower-level relay device 2 according to another embodiment. According to FIG. 19, the output switching unit 10 of the higher-level relay device 1 includes the output control unit 101 and the frame detection unit 102 as in the configuration illustrated in FIG. 3. The reception function unit 20 of the lower level relay apparatus 2 includes an ERR detection unit 201, a selection unit 202, and a frame generation unit 203.

  However, FIG. 19 differs from FIG. 3 in that there is a connection path 204 through which data from the working line # 0 is directly input to the frame generation unit 203 without passing through the ERR detection unit 201.

  FIG. 20 is a block diagram illustrating a configuration of the frame generation unit 203 according to another embodiment. Referring to FIG. 20, the frame generation unit 203 includes a notification packet generation unit 211 and a notification packet detection unit 212.

  The notification packet generation unit 211 obtains an error level based on the notification from the ERR detection unit 201, generates a control packet indicating an “error state” corresponding to the error level, and sends the control packet to the notification packet detection circuit 212.

  The notification packet detection circuit 212 detects the control packet from the data from the connection path 204 in addition to sending the control packet generated by the notification packet generation circuit 211 to the transmission function unit 24, and the detected control packet is also transmitted by the transmission function unit. Send to 24.

  Thereby, the lower relay apparatus 2 can also start switching based on the input of the control packet indicating the “error state” from the upper relay apparatus 1 in addition to the switching based on the error state detected by itself. Using this, it is possible to execute switching control from a remote location.

  For example, the higher-level relay device 1 may include a function for generating and transmitting a control packet indicating an “error state” in a pseudo manner in the transmission function unit 14.

  In addition, when priority is given to switching due to a failure that has occurred in the lower relay apparatus 2 over control from the upper relay apparatus 1, the error level of the control packet indicating the “error state” from the upper relay apparatus 1 is switched. The minimum level to do is good. In this case, if the standby switching due to the failure of another active line is performed, the recovery switching of the failed line is not performed by the control from the higher-level relay device 1. Further, even if the standby switching is performed by the control from the upper relay apparatus 1, if a failure occurs in any of the other lines, the failed line can be preferentially switched.

  Further, after repairing the failure of the working line in which the standby switching has occurred, the recovery switching can be remotely activated by inserting a control packet indicating “recovery switching” from the higher-level relay apparatus 1.

  According to the present embodiment, since the lower level relay device 2 operates in response to the control packet inserted in the data from the higher level relay device 1, remote switching control without adding large special equipment to each device Can be executed.

It is a block diagram which shows schematic structure of the communication system by this embodiment. FIG. 2 is a block diagram illustrating configurations of an upper relay device and a lower relay device illustrated in FIG. 1. FIG. 3 is a block diagram illustrating a configuration of an output switching unit of the higher-order relay device and a reception function unit of the lower-level relay device illustrated in FIG. 2. It is a flowchart which shows the operation | movement at the time of the preliminary | backup switch in the communication system by this embodiment. It is a figure which shows the example of mounting of the control packet in this embodiment. It is a figure which shows the information bit of the control packet which shows "error state". It is a figure which shows the information bit of the control packet which shows "preliminary switching." It is a figure for demonstrating preliminary | backup switching operation | movement. It is a flowchart which shows the preliminary | backup switching operation | movement of a low-order relay apparatus when the control packet of line | wire # 0 arrives first. It is a figure for demonstrating the recovery switching operation | movement of a low-order relay apparatus when the control packet of line | wire # 0 arrives first. It is a flowchart which shows the backup switching operation | movement of a low-order relay apparatus when the control packet of a protection line arrives first. It is a figure for demonstrating the backup switching operation | movement of a low-order relay apparatus when the control packet of a protection line arrives first. It is a flowchart which shows the operation | movement at the time of changing the line | wire for the standby switching in the communication system by this embodiment. It is a figure for demonstrating operation | movement of the output switching part of the line # 0 which received the control packet in the operation | movement of FIG. 13, and the output switching part of the line # 1. It is a flowchart which shows the recovery switching operation | movement of a low-order relay apparatus when the control packet of circuit | line # 0 arrives first. It is a figure for demonstrating the recovery switching operation | movement of a low-order relay apparatus when the control packet of line | wire # 0 arrives first. It is a flowchart which shows the recovery switching operation | movement of a low-order relay apparatus when the control packet of a protection line arrives first. It is a figure for demonstrating the recovery switching operation | movement of a low-order relay apparatus when the control packet of a protection line arrives first. It is a block diagram which shows the structure of the output switching part of the high-order relay apparatus of another embodiment, and the receiving function part of a low-order relay apparatus. It is a block diagram which shows the structure of the frame generation part 203 of other embodiment. It is a block diagram which shows the structure of the relay apparatus used for the conventional communication system provided with N: 1 redundant line.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Upper relay apparatus 2 Lower relay apparatus 10-12 Output switching part 13 Selection function part 14-16 Transmission function part 17 Reception function part 18 Transmission function part 20-23 Reception function part 24 Transmission function part 101 Output control part 102 Frame detection part 201 ERR (error) detection unit 202 selection unit 203 frame generation unit 204 connection path 211 notification packet generation unit 212 notification packet detection unit 301 header information unit 302 payload information unit 303 CRC information unit 304 information bits 401 to 404, 501 to 504, 601-604 data 405, 406, 505, 506, 605, 606 control packet A1-A9, B1-B3, C1-C6, D1-D9, E1-E3, F1-F4 steps

Claims (11)

A communication system using a redundant configuration consisting of a working line and a protection line for connection between devices,
When switching from the state in which data is transmitted on the working line to the protection line, the control information indicating the switching timing is inserted into the data of both the switching source working line and the switching destination protection line and transmitted. Equipment,
Both the data transmitted on the working line and the data transmitted on the protection line can be received from the upper apparatus, and the position of the control information on the working line inserted by the upper apparatus and the upper apparatus A communication system comprising: a subordinate device that adjusts timing so as to maintain the data order based on the position of the control information of the inserted protection line and switches from the working line to the protection line. The higher-level device is configured to correspond the data on the working line and the data on the protection line so that the data before the control information on the working line and the data after the control information on the protection line are continuous. Insert the control information at the switching position to be
The subordinate device is:
When the control information from the working line arrives before the control information from the protection line, the acquisition of data from the working line is stopped before the control information from the working line. In addition, when the control information from the protection line arrives, acquisition of data from the protection line is started,
When the control information from the protection line arrives before the control information from the working line, the data after the control information of the protection line is temporarily stored, and the working line When the control information from is received, after the data from the working line before the control information, the data of the retained protection line is connected,
The communication system according to claim 1. The host device continuously inserts the control information after the switching position of the working line a predetermined number of times,
When the lower-level device cannot receive the control information from the active line even after a predetermined time has elapsed after receiving the control information from the protection line, data on the protection line starting from the stored data Switch to
The communication system according to claim 2. In switching to return to the original working line from the state where switching to the protection line is performed,
The host device inserts control information indicating switching timing into data of both the protection line of the switching source and the working line of the switching destination, and transmits the data.
The subordinate apparatus performs timing so as to maintain the order of data based on the position of the control information of the working line inserted by the upper apparatus and the position of the control information of the protection line inserted by the upper apparatus. The communication system according to claim 1, wherein the communication line is switched from the protection line to the working line. The lower-level device performs an error check on the working line, and transmits control information that is generated based on the detected error level to instruct switching of the working line to the higher-level device via the protection line. ,
When the higher order device receives the control information from the lower order device, it starts switching the working line instructed by the control information.
The communication system according to any one of claims 1 to 4. A plurality of the working lines and one protection line, and a plurality of the working lines and one protection line constitute N: 1 redundancy;
The lower device is performing an error check of each of the plurality of working lines, and selects the working line with the highest error level as a switching target.
The communication system according to claim 5.   In the state where one of the working lines is switched to the protection line, when the error having a level higher than the error level of the working line occurs in another working line, the subordinate apparatus switches to the protection line. The communication system according to claim 6, wherein after the line is restored, the working line in which a high level error has occurred is switched to the protection line. The higher-level device artificially generates control information indicating an error level of the working line and transmits the control information to the lower-level device via the working line,
When the lower device receives control information indicating the error level from the working line, the lower device transmits control information instructing switching of the working line to the upper device via the protection line.
The communication system according to any one of claims 5 to 7. A communication device used as a host device in a communication system using a redundant configuration composed of a working line and a protection line for connection between a host device and a host device,
When switching from the state in which data is transmitted on the working line to the protection line, control is performed to switch data to the working line before the switching timing and to the protection line after the switching timing, and to indicate the switching timing An output switching unit that inserts information into the data of both the working line of the switching source and the protection line of the switching destination;
A first transmission function unit that transmits data for the working line from the output switching unit to the lower-level device via the working line;
A second transmission function unit that transmits data for the protection line from the output switching unit to the lower-level device via the protection line;
A communication device. A communication device used as a lower-level device in a communication system using a redundant configuration consisting of a working line and a protection line for connection between a higher-level device and a lower-level device,
A first reception function unit for receiving data transmitted from the host device via the protection line;
Receives data transmitted from the higher-level device through the working line, receives data received by the first reception function unit, and both the working line as a switching source and the protection line as a switching destination are received by the higher-level device. A second reception function unit for adjusting the timing so as to maintain the order of the data based on both positions of the control information indicating the switching timing inserted in the data, and switching from the working line to the protection line;
A communication device. A line control method in a communication system using redundancy consisting of a working line and a protection line for connection between a higher-level device and a lower-level device,
When switching from the state in which data is transmitted on the working line to the protection line, the higher-level device inserts control information indicating switching timing into data on both the switching source working line and the switching destination protection line. And transmitting to the lower device,
Timing is set so that the lower order apparatus maintains the data order based on the position of the control information of the working line inserted by the higher order apparatus and the position of the control information of the protection line inserted by the higher order apparatus. And switching from the working line to the protection line.

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