Network device of ring-shaped network and ring-shaped network system

Abstract

To solve the issue that the source of generation of an abnormality cannot be specified while an abnormality of any network device can be detected by comparing monitor data with a reference value.SOLUTION: Whether a difference between the number of errors of a reception packet and the number of errors of a transmission packet is within a predetermined range is determined, and the soundness of the whole network can be maintained by removing a network out of the range from a network.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present application relates to a network device for a ring network and a ring network system. [Background technology]

[0002] Conventionally, a method has been proposed for detecting an abnormality in a network device that constitutes a network by comparing data flowing through the device with known data when the abnormality occurs in the network device.

[0003] For example, in a communication system having a master station and multiple slave stations connected in a loop, the slave stations measure the error occurrence rate at their own stations by comparing a test signal received from the master station with a test signal that should have been received (see, for example, Patent Document 1).

[0004] Furthermore, in a cell processing device of an ATM network, a check is made to see whether the cell processing device is operating normally by comparing monitoring data, in which a predetermined monitoring expectation value has been overwritten on empty cells in the main signal cell stream, with the monitoring expectation value created in a monitoring expectation value generator at the downstream stage of the circuit (see, for example, Patent Document 2). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2013-85116 A [Patent Document 2] Japanese Patent Application Publication No. 9-214511 Summary of the Invention [Problem to be solved by the invention]

[0006] In a ring network in which multiple devices are connected in a ring shape, if an abnormality is detected, and the device in which the abnormality occurs can be identified and removed from the network, the abnormality can be prevented from propagating to normal devices, and the health of the entire network can be maintained. However, the devices disclosed in Patent Documents 1 and 2 can detect abnormalities by comparing monitoring data with reference values, but have a problem in that they cannot identify the source of the abnormality. In addition, there is a problem in that the device in which the abnormality occurs continues to operate in the same way as it does normally, which can have a negative effect on other devices.

[0007] The present application has been made to solve the above-mentioned problems, and aims to obtain a device that can remove a network device that is determined to be abnormal from the network, thereby maintaining the health of the entire network. [Means for solving the problem]

[0008] The network device of the ring network disclosed in the present application comprises: a receive error counter that counts the number of errors in received packets; a transmission error counter that counts the number of errors in transmitted packets; an error difference calculation unit that calculates a difference between the number of reception errors counted by the reception error counter and the number of transmission errors counted by the transmission error counter; a determination unit that determines whether or not the difference value calculated by the error difference calculation unit is within a predetermined range; The device is characterized by comprising a withdrawal unit which withdraws the device from the network when the difference value is not within the range.

[0009] In addition, the network device of the ring network disclosed in the present application is a reception error detection code check unit that detects whether or not an error detection code added to a received packet is inverted; a transmission error detection code check unit that detects whether or not an error detection code added to a transmission packet is inverted; a receive error counter for detecting the number of errors in received packets whose error detection code has not been inverted; a transmission error counter for detecting the number of errors in a transmission packet in which the error detection code is not inverted; an error difference calculation unit that calculates a difference between the number of reception errors counted by the reception error counter and the number of transmission errors counted by the transmission error counter; a determination unit that determines whether or not the difference value calculated by the error difference calculation unit is within a predetermined range; a disconnection unit that disconnects the device from the network when the difference value is not within the range; The present invention is characterized by comprising:

[0010] In addition, the network device of the ring network disclosed in the present application is a reception error check unit that detects an error in a received packet; a transmission error check unit for detecting errors in a transmission packet; a discard unit that discards a received packet in which an error has been detected by the reception error check unit; The present invention is characterized by comprising a disconnection unit which disconnects the terminal from the network when an error is detected by the transmission error check unit.

[0011] In addition, the network device of the ring network disclosed in the present application is a received packet acquisition unit that acquires a copy of a received packet; a transmission packet acquisition unit that acquires a copy of a transmission packet to be transmitted; a frame comparison unit for comparing a copy of the received packet with a copy of the transmitted packet to determine whether they match; a disconnection unit that disconnects the device from the network if the device does not match; The present invention is characterized by comprising: Effect of the Invention

[0012] According to the network device of the ring network disclosed in the present application, the health of the entire network can be maintained by identifying the network device in which an anomaly is occurring and removing it. [Brief description of the drawings]

[0013] [Figure 1] 1 is a block diagram showing a schematic configuration of a network system including a network device according to a first embodiment. [Diagram 2] 1 is a block diagram showing a schematic configuration of a network device according to a first embodiment. [Diagram 3] 5 is a flowchart showing an abnormality detection procedure performed by the network device according to the first embodiment. [Figure 4] FIG. 11 is a block diagram showing a schematic configuration of a network device according to a second embodiment. [Diagram 5] 11 is a flowchart showing an abnormality detection procedure performed by the network device according to the second embodiment. [Figure 6] FIG. 11 is a block diagram showing a schematic configuration of a network device according to a third embodiment. [Figure 7] 11 is a flowchart showing an abnormality detection procedure performed by a network device according to a third embodiment. [Figure 8] FIG. 13 is a block diagram showing a schematic configuration of a network device according to a fourth embodiment. [Figure 9] 13 is a flowchart showing an abnormality detection procedure performed by a network device according to a fourth embodiment. [Figure 10] FIG. 2 is a diagram illustrating an example of hardware of a microcomputer in a network device according to an embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] Hereinafter, preferred embodiments of the network device for a ring network according to the present invention will be described with reference to the drawings. Note that the same reference numerals are used to designate the same contents and corresponding parts, and detailed descriptions thereof will be omitted. In the following embodiments, the same reference numerals are used to designate the same components, and redundant descriptions will be omitted.

[0015] Embodiment 1 1 is a block diagram showing a schematic configuration of a network system including network devices according to embodiment 1. Network devices 1 to 6 are connected in a ring shape to form a ring network.

[0016] Each of the network devices 1 to 6 has two ports capable of transmitting and receiving data, and is connected to an adjacent network device. For example, the port 10a of the network device 1 is connected to the network device 2, and the port 10b is connected to the network device 6. In this manner, the network devices 1 to 6 are connected to their adjacent network devices to form a ring. The connections may be made by optical fiber or coaxial cable.

[0017] In such a ring network system, a code that enables the destination and source of each packet to be identified is added to each packet. For example, among packets received by network device 1, packets that are not addressed to the network device itself are transmitted to port 10b on the opposite side to the received packet. This operation is called relay. That is, referring to FIG. 2, a packet to be relayed received at port 10a is transmitted from port 10b via receiver 11a, relay unit 13, and transmitter 12a. In this embodiment, the unit of data for transmission and reception is called a packet, but may also be called a frame or a segment.

[0018] In the first embodiment, it is assumed that packets are sent with the destination being network device 1 so that they go around the ring network shown in FIG. 1 and return to network device 1, and that all packets originating from devices other than network device 1 are relayed.

[0019] For example, in FIG. 1, a control packet transmitted from port 10a of network device 1 passes through network device 2, network device 3, network device 4, network device 5, and network device 6 in this order, before returning to network device 1 (indicated by dashed line A in FIG. 1).

[0020] Conversely, a control packet transmitted from port 10b of network device 1 passes through network device 6, network device 5, network device 4, network device 3, and network device 2 in this order, and returns to network device 1 (dashed line B in FIG. 1).

[0021] In this way, all the network devices 1 to 6 connected to the network can generate network connection information and grasp the network connection state by receiving the transmitted control packet. Then, when each network device transmits communication data, it selects the route closest to the destination network device according to the grasped network connection state.

[0022] 2 is a block diagram showing a schematic configuration of a network device according to embodiment 1. The network device 1 has two ports 10a and 10b, and is provided with receivers 11a and 11b for receiving packets and transmitters 12a and 12b for transmitting packets, respectively.

[0023] The relay unit 13 relays packets between the port 10a and the port 10b. That is, it transfers the packets to the data processing unit 14, and also transfers the packets to the transmitters 12a and 12b for transmission to the port opposite to the port where the packets were received. The transmitters 12a and 12b transmit the packets as transmission packets to adjacent network devices. Furthermore, the relay unit 13 transfers the data in the packets whose destination includes the network device 1 itself to the data processing unit 14. An example of the packets relayed in this manner is the control packet described above. When relaying a received packet, relay unit 13 may transmit the received packet to data processing unit 14 even if the destination does not include its own network device 1. In this case, relay unit 13 or data processing unit 14 may remove the header portion of the received packet received by receivers 11a and 11b, and the data processing unit 14 may acquire the remaining transmission data. For relaying, transmitters 12a and 12b may generate a packet again from the transmission data from which the header portion has been removed (add a header, etc.).

[0024] Furthermore, the data processing unit 14 generates communication data to be transmitted from the local network device 1, and transfers it to the relay unit 13. The relay unit 13 determines which port is closer to the network device (station) that is the destination of the transmitted communication data, and transfers it to the transmitting unit of this port. The transmitting units 12a and 12b generate packets for transmitting the communication data, and transmit them to the adjacent network device. Note that the generation of the packets may be performed by the data processing unit 14.

[0025] The reception error counters 15a, 15b are arranged on the input side of the reception units 11a, 11b so as to detect errors in packets received by the reception units 11a, 11b and count the number of errors.

[0026] The transmission error counters 16a, 16b are arranged on the output side of the transmission units 12a, 12b so as to detect errors in packets transmitted via the transmission units 12a, 12b and count the number of errors.

[0027] As an example of the error detection for counting the number of errors in the reception error counters 15a, 15b and the transmission error counters 16a, 16b, a detection method using a frame check sequence (FCS), a detection method using a summation check, or a detection method using a parity check may be used. If the error detection code added to the packet does not match as a result of these checks, an error is counted.

[0028] The error difference calculation units 17a, 17b compare the reception error count values ​​detected by the reception error counters 15a, 15b with the transmission error count values ​​detected by the transmission error counters 16a, 16b, and calculate the difference between the error counts.

[0029] The judgment units 18a and 18b judge whether or not the network device 1 itself has an abnormality based on whether or not the difference value of the error count calculated by the error difference calculation units 17a and 17b is within a predetermined threshold range.

[0030] The disconnection unit 19 disconnects the network device 1 from the ring network when the network device 1 is determined to be abnormal based on the determination results of the determination units 18a and 18b. As a disconnection configuration, the network device 1 may be bypassed by an optical switch.

[0031] Next, the operation will be described. In the first embodiment, the number of errors in packets received by the network device 1 itself and in packets sent from the network device 1 itself is monitored to detect an abnormality in the network device 1 itself and to keep the entire ring type network system in a normal state.

[0032] In a ring network system, normal control packets must be periodically transmitted from each of the network devices 1 to 6. For example, if an abnormal control packet is generated inside the network device 1, the abnormal control packet is transmitted to each device, and each network device cannot receive normal data from the network device 1. Furthermore, the network device 1 generating the abnormal control packet cannot recognize that it is in an abnormal state and continues communication, resulting in continuous communication failure.

[0033] To avoid this, the number of errors in the receiving control packets is monitored by the receiving error counters 15a, 15b, and the number of errors in the sending control packets is monitored by the sending error counters 16a, 16b. The error difference calculated by the error difference calculation units 17a, 17b is used to check whether the number of abnormalities is increasing within the network device 1 itself.

[0034] In addition, the communication data for the network device 1 itself is generated by the data processing unit 14, and when passing through the relay unit 13, the port that is closer to the destination network device (station) is determined, and the data is transmitted to this port 10a or port 10b via the transmission units 12a, 12b.

[0035] Error difference calculation units 17a, 17b calculate the difference between the number of errors detected by reception error counters 15a, 15b and transmission error counters 16a, 16b. If the difference value calculated by error difference calculation units 17a, 17b is greater than a predetermined threshold, determination units 18a, 18b determine that the local network device 1 is an abnormal device generating abnormal packets. If it is determined that the local network device 1 is in an abnormal state, a withdrawal unit 19 causes the local device to withdraw from the ring network.

[0036] FIG. 3 is a flowchart showing an abnormality detection procedure performed by the network device according to the first embodiment. (1) In the case of packets received from the ports 10a and 10b (step S1 in FIG. 3), the reception error counters 15a and 15b detect the number of errors in the received packets (step S2). The detected count numbers of reception errors are notified to the error difference calculation units 17a and 17b (step S3). (2) Among the received packets, the relayed packets are transmitted as transmission packets via the transmission units 12a and 12b, and the transmission error counters 16a and 16b detect the number of errors in the transmission packets (step S4). The detected transmission error counts are notified to the error difference calculation units 17a and 17b (step S5). (3) When transmitting communication data of the own network device 1, the packets created by the transmitters 12a and 12b are subjected to detection of the number of errors by the transmission error counters 16a and 16b in the same manner as the packets to be relayed (step S4). The detected count number of transmission errors is notified to the error difference calculation units 17a and 17b (step S5). (4) The error difference calculators 17a and 17b calculate the difference between the notified reception error count number and transmission error count number (step S6). (5) The calculated difference in error counts is compared with a predetermined threshold by the determination units 18a and 18b (step S7), and if the difference in error counts is equal to or less than the threshold, the network device 1 is determined to be normal and communication of the network device 1 is continued (step S8).If the difference in error counts exceeds the threshold, the network device 1 is determined to be abnormal, and the disconnection unit 19 disconnects the network device 1 from the network (step S9).

[0037] As described above, according to the first embodiment, the error count of the packet received by the network device 1 itself and the error count count of the packet transmitted by the network device 1 itself are counted, and the error difference calculation units 17a and 17b calculate the difference in the error count. If the same number of errors are detected both during reception and during forwarding, it can be determined that no new errors have occurred in the network device 1 itself and that the network device 1 is operating normally. If a difference in the number of errors is observed between during reception and during forwarding, it can be determined that some abnormality has occurred in the network device 1 itself and that the network device 1 is not operating normally. In this way, the network device 1 itself can detect an abnormality. In addition, when an abnormality is detected, the network device 1 itself is separated from the network, which has the effect of not adversely affecting other network devices on the network. This makes it possible to prevent the entire network from failing to function, and maintain a normal network state.

[0038] Embodiment 2 Next, a second embodiment will be described with reference to the drawings. Fig. 4 is a block diagram showing a schematic configuration of a network device according to the second embodiment. In Fig. 4, ports 10a, 10b, receivers 11a, 11b, transmitters 12a, 12b, relay unit 13, data processor 14, and disconnector 19 are the same as those in Fig. 2. Fig. 4 has reception error check units 20a, 20b instead of reception error counters 15a, 15b in Fig. 2, transmission error check units 21a, 21b instead of transmission error counters 16a, 16b, and a discard unit 22 instead of error difference calculation units 17a, 17b and determination units 18a, 18b.

[0039] The reception error check units 20a, 20b are arranged on the input side of the reception units 11a, 11b and check for errors in packets input to the reception units 11a, 11b. The transmission error check units 21a, 21b are arranged on the output side of the transmission units 12a, 12b and check for errors in packets transmitted from the transmission units 12a, 12b. The discard unit 22 discards the received packet if an error is detected as a result of the check by the reception error check units 20a, 20b. The withdrawal unit 19 withdraws the network device 1 from the ring network if an error is detected by the transmission error check units 21a, 21b.

[0040] By providing reception error check units 20a, 20b and discard unit 22, error packets detected by reception error check units 20a, 20b are discarded by discard unit 22, thereby preventing the error packets from being relayed within network device 1. Also, by detecting errors by transmission error check units 21a, 21b, the state of network device 1 itself can be determined, and network device 1 itself can be disconnected from the network by disconnection unit 19.

[0041] FIG. 5 is a flowchart showing an abnormality detection procedure performed by the network device 1 according to the second embodiment. (1) A packet is received from port 10a or port 10b (step S11). The received packet is checked for errors by reception error check units 20a and 20b. If an error is detected as a result of the check (step S12), the received packet in which the error was detected is discarded by discard unit 22 (step S13). (2) The received packets in which no errors are detected are relayed from the receivers 11a and 11b to the transmitter 12a via the relay unit 13 (step S14). In this case, the relayed packets are input to the transmitters 12a and 12b as transmission packets. (3) When communication data of the network device 1 itself is to be transmitted, the packets created by the transmitting units 12a and 12b are processed by the transmitting units 12a and 12b in the same manner as packets to be relayed. (4) The transmission error check units 21a and 21b check the transmission packets sent from the transmission units 12a and 12b for errors (step S15). (5) If an error is detected by the transmission error check units 21a and 21b, the device is disconnected from the network by the disconnection unit 19 (step S16). (6) The transmission packet in which no error is detected is transmitted from port 10a or port 10b (step S17).

[0042] As described above, according to the second embodiment, by removing the network device from the network when an error is detected in a transmitted packet, it is possible to prevent adverse effects on other network devices on the ring network. In addition, by having a function to discard a received packet when an error is detected, it is possible to prevent the error packet from being relayed within the network device, thereby preventing adverse effects on other functions within the network device.

[0043] Embodiment 3 Next, a third embodiment will be described with reference to the drawings. Fig. 6 is a block diagram showing a schematic configuration of a network device according to embodiment 3. In Fig. 6, ports 10a, 10b, receivers 11a, 11b, transmitters 12a, 12b, relay unit 13, data processor 14, and detacher 19 are the same as those in Fig. 2. In Fig. 6, received packet acquirers 23a, 23b are provided instead of the received error counters 15a, 15b in Fig. 2, transmitted packet acquirers 24a, 24b are provided instead of the transmitted error counters 16a, 16b, and packet comparators 25a, 25b are provided instead of the error difference calculators 17a, 17b and the judgers 18a, 18b.

[0044] The received packet acquisition units 23a and 23b are arranged on the input side of the receiving units 11a and 11b, and acquire copies of received packets input to the receiving units 11a and 11b. In this case, the copy includes temporarily storing the bit information of the received packets in a buffer. The transmitted packet acquisition units 24a and 24b are arranged on the output side of the transmitting units 12a and 12b, and acquire copies of transmitted packets transmitted from the transmitting units 12a and 12b. In this case, the copy includes temporarily storing the bit information of the transmitted packets in a buffer, as in the case of the copy of the received packets. The packet comparison units 25a and 25b compare the copies of the received packets acquired by the received packet acquisition units 23a and 23b with the copies of the transmitted packets acquired by the transmitted packet acquisition units 24a and 24b, in units of bits, for all data including the headers constituting the packets. The removal unit 19 removes the own network device 1 from the ring network when the packet comparison units 25a and 25b find that the copies of the received packets do not match the copies of the transmitted packets.

[0045] In the third embodiment, the received packet acquisition units 23a, 23b, the transmitted packet acquisition units 24a, 24b, and the packet comparison units 25a, 25b compare packets transmitted and received, thereby determining the state of the network device 1 itself, and the device can be removed from the network by the removal unit 19.

[0046] FIG. 7 is a flowchart showing an abnormality detection procedure performed by the network device 1 according to the third embodiment. (1) Packets are received from the ports 10a and 10b (step S21). From the received packets, received packet acquisition units 23a and 23b create copies of the received packets and acquire them (step S22). (2) The received packets are relayed from the receivers 11a and 11b via the relay unit 13 to the transmitters 12a and 12b. (3) The transmission packet acquisition units 24a and 24b create copies of the transmission packets transmitted from the transmission units 12a and 12b and acquire them (step S23). (4) The packet comparison units 25a and 25b compare the copy of the received packet with the copy of the transmitted packet (step S24). (5) If the comparison result indicates no match, the device is removed from the network by the removal unit 19 (step S25). If the copy of the received packet matches the copy of the transmitted packet, the packet is transmitted from ports 10a and 10b (step S26). (6) When communication data of the network device 1 itself is to be transmitted, packets that are generated by the transmitting units 12a and 12b and transmitted from the transmitting units 12a and 12b are not subject to comparison by the packet comparing units 25a and 25b.

[0047] As described above, according to the third embodiment, the network device can detect anomalies by itself by comparing a copy of a packet it receives with a copy of a packet it transmits. This makes it possible to maintain the integrity of all data being transmitted and received. In addition, when an anomaly is detected, the network device is separated from the network, which has the effect of preventing adverse effects on other network devices on the network. This makes it possible to prevent the entire network from failing to function, and maintain a normal network state.

[0048] Embodiment 4 Next, a fourth embodiment will be described with reference to the drawings. Fig. 8 is a block diagram showing a schematic configuration of a network device according to the fourth embodiment. In Fig. 8, ports 10a, 10b, receivers 11a, 11b, transmitters 12a, 12b, relay unit 13, data processor 14, receive error counters 15a, 15b, transmit error counters 16a, 16b, error difference calculators 17a, 17b, judgers 18a, 18b, and separator 19 are the same as those in Fig. 2.

[0049] In FIG. 8, there are provided transmission error detection code check units 26a, 26b which determine whether or not the error detection code added to a transmission packet transmitted from ports 10a, 10b has been inverted, reception error detection code check units 27a, 27b which determine whether or not the error detection code added to a reception packet received from ports 10a, 10b has been inverted, and error detection code inversion units 28a, 28b which invert the error detection code of a transmission packet in which an error has been detected by the transmission error counters 16a, 16b.

[0050] In the fourth embodiment, errors are detected by an error detection code added to a packet. When an error in a transmission packet is detected by the transmission error counters 16a and 16b, the error detection code added to the transmission packet is inverted by the error detection code inverting units 28a and 28b, and the transmission packet is transmitted to the next device from the ports 10a and 10b.

[0051] The reception error detection code check units 27a, 27b determine whether the error detection code added to the reception packet received from the ports 10a, 10b is inverted or not, and if it is determined that the error detection code is inverted, the reception error counters 15a, 15b do not count errors. The transmission error detection code check units 26a, 26b determine whether the error detection code added to the transmission packet transmitted from the ports 10a, 10b is inverted or not, and if it is determined that the error detection code is inverted, the transmission error counters 16a, 16b do not count errors.

[0052] This allows the reception error counters 15a, 15b and the transmission error counters 16a, 16b to count errors that occur only in the network device 1 itself, without counting packet errors that occur in other network devices.

[0053] FIG. 9 is a flowchart showing an abnormality detection procedure performed by the network device according to the fourth embodiment. (1) A packet is received from the port 10a, 10b (step S31). The received error detection code check units 27a, 27b check whether the error detection code added to the received packet is inverted (step S32). (2) If the error detection code is inverted, the reception error counters 15a and 15b do not count errors in the received packet (step S33). (3) If the error detection code is not inverted, the presence or absence of an error in the received packet is detected (step S34). (4) The number of errors detected in step S34 by the reception error counters 15a and 15b is notified to the error difference calculation section (step S35). (5) The received packet is relayed and passes through the transmitter as a transmission packet, and the transmission error detection code check units 26a and 26b check whether the error detection code added to the transmission packet has been inverted (step S36). (6) If the error detection code added to the transmission packet is inverted, the transmission error counters 16a and 16b do not count errors in the transmission packet (step S37). (7) If the error detection code added to the transmission packet is not inverted, the transmission error counters 16a, 16b detect an error in the transmission packet (step S38). If an error is detected, the error detection code inversion units 28a, 28b invert the error detection code added to the transmission packet and transmit the transmission packet to the next device (step S39). (8) The transmission error counters 16a and 16b notify the number of errors detected in step S39 to the air difference calculation unit (step S40). (9) The error difference calculators 17a and 17b calculate the difference between the number of errors in the received packets detected by the reception error counters 15a and 15b and the number of errors in the transmitted packets detected by the transmission error counters 16a and 16b (step S41). (10) The calculated error count difference is compared with a preset threshold value by the judgment units 18a, 18b, and if the error count difference is less than or equal to the threshold value, the network device 1 is judged to be normal (step S42), and communication of the network device 1 is continued (step S43). (11) If the difference in the number of errors exceeds a threshold, the network device 1 is determined to be abnormal, and the device is caused to leave the network by the leaving unit 19 (step S44).

[0054] As described above, according to the fourth embodiment, by counting only the number of received packet errors and the number of transmitted packet errors generated in the own network device without counting the number of packet errors generated in other network devices, the own network device can detect an abnormality by itself, and can prevent the own network device from being mistakenly removed from the network due to an error in another network device. In addition, when an abnormality in the own network device is detected, the own network device is removed from the network, which has the effect of preventing adverse effects on other network devices on the network. Therefore, it is possible to prevent the entire network from failing to function, and to maintain a normal network state.

[0055] An example of the hardware of the microcomputer in the network device 1 is shown in FIG. 10. The network device 1 is composed of a processor 100 and a storage device 200. Although not shown, the storage device 200 includes a volatile storage device such as a random access memory and a non-volatile auxiliary storage device such as a flash memory. Also, instead of the flash memory, an auxiliary storage device such as a hard disk may be included. The processor 100 performs the operations of, for example, the above-mentioned embodiments 1 to 4 by executing a program input from the storage device 200. In this case, the program is input from the auxiliary storage device to the processor 100 via the volatile storage device. Also, the processor 100 may output data such as a calculation result to the volatile storage device of the storage device 200, or may store the data in the auxiliary storage device via the volatile storage device.

[0056] Although the present application describes various exemplary embodiments and examples, the various features, aspects, and functions described in one or more embodiments are not limited to application to a particular embodiment, but may be applied to the embodiments alone or in various combinations. Therefore, countless modifications not exemplified are assumed within the scope of the technology disclosed in the present specification, including, for example, modifying, adding, or omitting at least one component, and further, extracting at least one component and combining it with a component of another embodiment. [Explanation of symbols]

[0057] 1 to 6: network devices, 10a, 10b: ports, 11a, 11b: receivers, 12a, 12b: transmitters, 13: relay units, 14: data processing units, 15a, 15b: receiver error counters, 16a, 16b: transmitter error counters, 17a, 17b: error difference calculation units, 18a, 18b: judgement units, 19: detachment units, 20a, 20b: receiver error check units, 21a, 21b: transmitter error check units, 22: discard units, 23a, 23b: receiver packet acquisition units, 24a, 24b: transmitter packet acquisition units, 25a, 25b: packet comparison units, 26a, 26b: transmitter error detection code check units, 27a, 27b: receiver error detection code check units, 28a, 28b: error detection code inversion units, 100: processor, 200: storage device.

Claims

1. a receive error counter that counts the number of errors in received packets; a transmission error counter that counts the number of errors in transmitted packets; an error difference calculation unit that calculates a difference between the number of reception errors counted by the reception error counter and the number of transmission errors counted by the transmission error counter; a determination unit that determines whether or not the difference value calculated by the error difference calculation unit is within a predetermined range; a disconnection unit that disconnects the device from the network when the difference value is not within the range; A network device for a ring network comprising:

2. a reception error detection code check unit that detects whether or not an error detection code added to a received packet is inverted; a transmission error detection code check unit that detects whether or not an error detection code added to a transmission packet is inverted; a reception error counter for detecting the number of errors in the received packet in which the error detection code is not inverted; a transmission error counter for detecting the number of errors in the transmission packet in which the error detection code is not inverted; an error difference calculation unit that calculates a difference between the number of reception errors counted by the reception error counter and the number of transmission errors counted by the transmission error counter; a determination unit that determines whether or not the difference value calculated by the error difference calculation unit is within a predetermined range; a disconnection unit that disconnects the device from the network when the difference value is not within the range; A network device for a ring network comprising:

3. 3. The network device of the ring network according to claim 2, wherein, when an error is detected in the transmission packet, an error detection code inverting unit inverts the error detection code of the transmission packet and then transmits the transmission packet.

4. 4. A network device for a ring network according to claim 1, wherein the transmission error counter and the reception error counter perform error detection using a frame check sequence, and if the error detection codes added to the received packet and the transmitted packet do not match, it is deemed to be an error and is counted.

5. 4. A network device for a ring network as claimed in claim 1, wherein the transmission error counter and the reception error counter perform error detection by sum check, and if the error detection codes added to the received packet and the transmitted packet do not match, it is deemed to be an error and is counted.

6. 4. A network device for a ring network as claimed in claim 1, wherein the transmission error counter and the reception error counter perform error detection by parity check, and if the error detection codes added to the received packet and the transmitted packet do not match, it is deemed to be an error and is counted.

7. a reception error check unit that detects an error in a received packet; a transmission error check unit for detecting errors in a transmission packet; a discard unit that discards a received packet in which an error has been detected by the reception error check unit; a disconnection unit that disconnects the terminal from the network when an error is detected by the transmission error check unit; A network device for a ring network comprising:

8. 8. The network device for a ring network according to claim 7, wherein the transmission error check section and the reception error check section perform error detection using a frame check sequence.

9. 8. The network device for a ring network according to claim 7, wherein the transmission error check section and the reception error check section carry out error detection by means of a sum check.

10. 8. The network device for a ring network according to claim 7, wherein the transmission error check section and the reception error check section perform error detection by a parity check.

11. a received packet acquisition unit that acquires a copy of a received packet; a transmission packet acquisition unit that acquires a copy of a transmission packet to be transmitted; a frame comparison unit that compares the copy of the received packet with the copy of the transmitted packet and determines whether they match; a disconnection unit that disconnects the device from the network if the device does not match; A network device for a ring network comprising:

12. 12. The network device of the ring network according to claim 1, wherein the disconnection unit disconnects from the network by bypassing the network using an optical switch.

13. 12. A network device for a ring network according to claim 1, wherein a code that enables identification of a destination of the transmitted packet is added to the transmitted packet, thereby making it possible to identify a source network device from the transmitted packet.

14. 12. A ring network system comprising the network devices according to claim 1, 2, 7 and 11 connected in a ring shape.

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