Communication device and communication method

Abstract

One aspect of the present invention relates to a communication device that relays communication between a lower-level device and a higher-level device, the communication device comprising: a media access control (MAC) address learning unit that, on the basis of a downlink communication frame from the higher-level device, learns a MAC address of a device serving as a transmission source of the downlink communication frame; and a management unit that manages a communication management table for determining whether or not to perform learning of the MAC address. The communication management table holds a connection state with the communication device of each of the lower-level devices, and the MAC address learning unit determines whether or not to perform MAC address learning on the lower-level device on the basis of the connection state of each of the lower-level devices.

Description

Communication device and communication method

[0001] The present invention relates to a technique for communicating using a MAC (Media Access Control) address.

[0002] Conventionally, a communication device having a plurality of ports has a function of learning the MAC addresses of devices connected to each port and transferring frames to the correct port based on the learning results. This can avoid bandwidth compression due to flooding or ARP (Address Resolution Protocol) and a decrease in the processing capacity of network devices. MAC address learning is a commonly used technique in communication devices. Also, in MAC address learning, when it is detected that a downlink frame received from an upper device and an uplink frame received from a lower device are transmitted from the same MAC address, the frame is discarded, thereby suppressing the frame from looping in the network and causing congestion (see, for example, Patent Document 1).

[0003] PCT / JP2020 / 041896

[0004] However, in the conventional technology, when changing a communication device in the system, the availability of the system may decrease due to the MAC address learning function. For example, the communication interruption time may become long, or the occurrence of a user loop in the communication device may not be appropriately detected (see, for example, FIG. 10).

[0005] FIG. 10 is a diagram for explaining an example of a situation where communication interruption occurs when switching a communication device by MAC address learning of the conventional method. In FIG. 8, a first upper device 93 and a second upper device 94 are connected to the upper side of the first communication device 91 and the second communication device 92, and a terminal device 95 and a user terminal 96 are connected to the lower side. FIG. 10 shows a situation where the communication device used by the user terminal 96 to communicate with the first upper device 93 is switched from the first communication device 91 to the second communication device 92 by performing the following procedures (1) and (2).

[0006] Procedure (1): Configure the second communication device 92 with the same VLAN settings as the first communication device 91, and ensure that both the first communication device 91 and the second communication device 92 are connected to the second host device 94. Procedure (2): Reconnect the cable L connecting the termination device 95 to the first communication device 91 to the second communication device 92.

[0007] In Figure 10, for simplicity, a single termination device 95 is shown. However, in reality, multiple termination devices are connected to a communication device. If the switching on the higher-level device (wiring, VLAN settings, etc.) is performed after switching the wiring of all termination devices, the communication downtime will be long. Therefore, by connecting the second communication device 92, which has the same VLAN settings as the first communication device 91, to the second higher-level device 94 in advance using procedure (1), and then performing the termination device switching in procedure (2), it is possible to enable the user terminal 96 to start communicating immediately after the destination of the termination device is switched.

[0008] In this case, if, before the switchover of the communication devices, a situation occurs where a frame transmitted from the user terminal 96 is flooded by the second higher-level device 94, for example, by ARP, the frame is output to all ports of the second higher-level device 94 except the receiving port. That is, in this case, the frame is received by the first higher-level device 93 and the second communication device 92. At this time, the second communication device 92 adds the MAC address of the user terminal 96 to the MAC table that stores the learning results of the downlink frame using its MAC address learning function. On the other hand, if the user terminal 96 transmits an uplink frame after the switchover of the communication devices, the second communication device 92 also adds the MAC address of the user terminal 96 to the MAC table of the uplink frame using its MAC address learning function.

[0009] Subsequently, when the second communication device 92 receives a frame from user terminal 96, it determines that a user loop has occurred because the MAC address of user terminal 96 is registered in both the uplink frame's MAC table and the downlink frame's MAC table, and discards the frame. This results in a communication interruption at user terminal 96. Depending on the aging timer for MAC address learning (the time interval for erasing the MAC learning table), this communication interruption generally lasts for about 5 minutes or more. It is possible to shorten the communication interruption time by shortening the aging timer, but in that case, there is a concern that user loops may not be properly detected.

[0010] In view of the above circumstances, the present invention aims to provide a technology that can suppress the decrease in system availability when communication equipment is replaced.

[0011] One aspect of the present invention is a communication device that relays communication between a lower-level device and a higher-level device, comprising: a MAC address learning unit that learns the MAC (Media Access Control) address of the source device of a downlink communication frame based on a downlink communication frame from the higher-level device; and a management unit that manages a communication management table for determining whether or not to perform MAC address learning, wherein the communication management table maintains the connection status with the communication device for each lower-level device, and the MAC address learning unit determines whether or not to perform MAC address learning for each lower-level device based on the connection status for each lower-level device.

[0012] One aspect of the present invention is a control method for a communication device that relays communication between a lower-level device and a higher-level device, which performs a MAC address learning process to learn the MAC (Media Access Control) address of the source device of a downlink communication frame based on a downlink communication frame from the higher-level device, and a management process to manage a communication management table for determining whether or not to perform MAC address learning, wherein the communication management table maintains the connection status with the communication device for each lower-level device, and the MAC address learning process determines whether or not to perform MAC address learning for each lower-level device based on the connection status for each lower-level device.

[0013] This invention makes it possible to suppress the decrease in system availability caused by MAC address learning functions when replacing communication devices within a system.

[0014] This figure shows an example of the system configuration of the communication system 1 of the embodiment. This figure illustrates the situation in which the second communication device 20B of the embodiment performs MAC address learning and the situation in which it does not perform MAC address learning. This figure shows an example of the contents of the communication management table T1. This figure illustrates the manner of MAC address learning when switching the destination of the second termination device 30B from the first communication device 20A to the second communication device 20B in the communication system 1 of the embodiment. This is a diagram (part 1) illustrating the system state transition when switching the destination of the second termination device 30B from the first communication device 20A to the second communication device 20B in the communication system 1 of the embodiment. This is a diagram (part 2) illustrating the system state transition when switching the destination of the second termination device 30B from the first communication device 20A to the second communication device 20B in the communication system 1 of the embodiment. This figure shows an example of the configuration of the communication device 20 of the embodiment. This is a diagram (part 1) illustrating the system state transition during switching when the communication system 1 of the embodiment is applied to the optical communication system 2. This is a diagram (part 2) illustrating the transition of the system state during switching when the communication system 1 of the embodiment is applied to the optical communication system 2. This diagram explains the prior art.

[0015] Embodiments of the present invention will be described in detail with reference to the drawings. Figure 1 is a diagram showing an example of the system configuration of a communication system 1 of the embodiment. The communication system 1 comprises a first higher-level device 10A, a second higher-level device 10B, a first communication device 20A, a second communication device 20B, a first termination device 30A, and a second termination device 30B. The first user terminal 40A and the second user terminal 40B are communication terminals used by users of the communication system 1. For example, the first user terminal 40A and the second user terminal 40B may be devices such as PCs, tablets, or smartphones. Hereinafter, the side of the higher-level device 10 as seen from the user terminal 40 will be referred to as "upstream," and the side of the user terminal 40 as seen from the higher-level device 10 will be referred to as "downstream." Also, hereafter, communication from the downstream side to the upstream side will be referred to as "upstream communication," and the frames of upstream communication will be referred to as "upstream frames." Similarly, hereafter, communication from the upstream side to the downstream side will be referred to as "downstream communication," and the frames of downstream communication will be referred to as "downstream frames." Furthermore, in the following, when a lower-level device is directly or indirectly connected to a higher-level device, it may be described as the higher-level device "accommodating" the lower-level device.

[0016] In other words, in Figure 1, the first host device 10A houses the second host device 10B, and the second host device 10B houses the first communication device 20A and the second communication device 20B. Furthermore, the first communication device 20A houses the first termination device 30A and the second termination device 30B, and the first termination device 30A and the second termination device 30B house the first user terminal 40A and the second user terminal 40B, respectively.

[0017] Figure 1 illustrates a scenario in communication system 1 where the destination of the second termination device 30B, which accommodates the second user terminal 40B, is updated (switched / migrated) from the first communication device 20A to the second communication device 20B. That is, the first communication device 20A is the source of the switch / migration, and the second communication device 20B is the destination of the switch / migration. Figure 1 shows the state of communication system 1 before the switch. In Figure 1, the destination second communication device 20B is accommodated in the second higher-level device 10B, but neither termination device 30 is accommodated. In this state, by switching the connection destination of the second termination device 30B from the first communication device 20A to the second communication device 20B, the destination of the first user terminal 40A and the second user terminal 40B is updated from the first communication device 20A to the second communication device 20B.

[0018] In the situation shown in Figure 1, uplink communications originating from the first user terminal 40A and the second user terminal 40B are forwarded to the second higher-level device 10B via the first termination device 30A and the second termination device 30B, and the first communication device 20A, respectively. If the communications are flooded at the second higher-level device 10B, they are forwarded to both the first higher-level device 10A and the second communication device 20B. In this case, while conventional MAC (Media Access Control) address learning methods learn the MAC addresses of the source first user terminal 40A and the second user terminal 40B for downlink communications, the second communication device 20B in this embodiment is configured not to learn the MAC address for downlink communications in the pre-switching situation shown in Figure 1, but to do so after the switch. This means that immediately after the destination of the second communication device 20B is switched, the MAC address of the second user terminal 40B is not registered in the MAC table for downlink communications. Therefore, according to the second communication device 20B of this embodiment, it is possible to suppress the detection of a user loop for the second user terminal 40B during switching, thereby suppressing a decrease in the availability of the communication system 1 when the communication device 20 is updated.

[0019] Figure 2 illustrates the situation in which the second communication device 20B of the embodiment performs MAC address learning and the situation in which it does not perform MAC address learning. The situation shown in Figure 2 is when the second communication device 20B is housed in the second host device 10B and also houses the second termination device 30B. In the situation in Figure 2, the second communication device 20B does not house the first termination device 30A. This situation is, for example, after the destination of the second termination device 30B has been changed from the first communication device 20A to the second communication device 20B. In this situation, the first termination device 30A is not connected to the second communication device 20B and therefore cannot communicate with the host device. On the other hand, in this situation, the second termination device 30B is connected to the second communication device 20B and therefore can communicate with the host device. In other words, in the situation shown in Figure 2, the first termination device 30A is in a state where communication is not permitted (communication not permitted state), and the second termination device 30B is in a state where communication is permitted (communication permitted state).

[0020] The first termination device 30A, which is in a communication-unauthorized state, does not receive downlink frames from the upstream side via the second communication device 20B, so there is no need to detect user loops. On the other hand, the second termination device 30B, which is in a communication-authorized state, may receive downlink frames from the upstream side via the second communication device 20B, so it is necessary to detect user loops. For these reasons, the second communication device 20B in this embodiment is configured not to learn the MAC address of the termination device 30 in a communication-unauthorized state (the first termination device 30A in Figure 2), but to learn the MAC address of the termination device 30 in a communication-authorized state (the second termination device 30B in Figure 2). Here, we have described the case where the element separating the communication-authorized state and the communication-unauthorized state is the presence or absence of a physical connection, but this element may be extended to the presence or absence of a logical connection. For example, the communication-unauthorized state may be a situation in which frames are discarded for some reason, even though it is electrically possible to send and receive frames.

[0021] The second communication device 20B can recognize the communication status (communication permitted or communication not permitted) of the first termination device 30A and the second termination device 30B by referring to the following communication management table T1, for example. The communication management table T1 is registered in the second communication device 20B in advance, before the second communication device 20B is connected to the second higher-level device 10B.

[0022] Figure 3 shows an example of the contents of the communication management table T1. The communication management table T1 is configured as a table that associates, for example, the identification information (ID) of the termination device 30 connected to the second communication device 20B, the MAC address of the upper-level interface of the termination device 30, the VLAN ID of the VLAN (Virtual LAN) assigned to the MAC address, the communication status of the downlink communication identified by the combination of the MAC address and the VLAN ID (communication permitted or communication not permitted), and whether or not MAC address learning has been performed according to the communication status. The VLAN ID may be represented by a combination of the service provider VLAN ID (SVID) and the customer VLAN ID (CVID).

[0023] Figure 3 shows an example where the first termination device 30A is in a communication-unauthorized state and the second termination device 30B is in a communication-authorized state. When the communication status value is "communication-unauthorized state", the MAC address learning value is set to "do not perform", and when the communication status value is "communication-authorized state", the MAC address learning value is set to "perform". The communication status value may be updated by the administrator of the communication system 1, or the second termination device 30B may be configured to update it in response to changes in the communication status. The MAC address learning value may also be updated by the administrator of the communication system 1, or it may be automatically changed in response to the communication status value. When the communication management table T1 is as shown in Figure 3, the second communication device 20B operates in a way that it does not perform MAC address learning for the first termination device 30A, but performs learning for the second termination device 30B during downlink communication.

[0024] Figure 4 illustrates the MAC address learning process in the communication system 1 of the embodiment when switching the destination of the second termination device 30B from the first communication device 20A to the second communication device 20B. The left side of the figure shows the situation before the switch, and the right side shows the situation after the switch. Before the switch, the communication status of both the first termination device 30A and the second termination device 30B to the second communication device 20B is in a communication-unauthorized state. Of these, the communication status of the first termination device 30A is changed to a "communication-authorized state" in conjunction with the switch in destination.

[0025] As described above, before the destination switchover, both the first termination device 30A and the second termination device 30B are in a state where communication with the second communication device 20B is not permitted. Therefore, if uplink frames from the first user terminal 40A and the second user terminal 40B are forwarded from the second upper-level device 10B to the second communication device 20B due to flooding or the like, the second communication device 20B will not perform MAC address learning for both VLANs (VLAN #1 and VLAN #2) of the first termination device 30A and the second termination device 30B.

[0026] On the other hand, after the switchover of the receiving device, the first termination device 30A is in a state where it is not authorized to communicate with the second communication device 20B, and the second termination device 30B is in a state where it is authorized to communicate with the second communication device 20B. Therefore, if an uplink frame from the first user terminal 40A is forwarded to the second communication device 20B due to flooding or the like, the second communication device 20B does not perform MAC address learning for the first termination device 30A. On the other hand, if a downlink frame destined for the second user terminal 40B is forwarded to the second communication device 20B due to flooding or the like, the second communication device 20B performs MAC address learning for the second termination device 30B. Therefore, according to the second communication device 20B of this embodiment, even if an uplink frame from the second termination device 30B is received from the second higher-level device 10B before the switchover, MAC address learning can be avoided, thus suppressing the detection of user loops after the switchover for the second termination device 30B.

[0027] Figures 5 and 6 illustrate the system state transitions in the communication system 1 of the embodiment when switching the destination of the second termination device 30B from the first communication device 20A to the second communication device 20B. Figure 5 illustrates the first and second phases of this transition, and Figure 6 illustrates the third and fourth phases of this transition.

[0028] (1) Phase 1 Phase 1 is a phase in which pre-configuration is performed on the second communication device 20B, which will be the switching target. Phase 1 is a pre-process phase in which the second communication device 20B is connected to the network of the communication system 1, and in Phase 1, the second communication device 20B is not connected to either the second upper-level device 10B or the second termination device 30B. For example, in Phase 1, the communication management table T1A illustrated in Figure 5 is registered for the second communication device 20B. That is, in Phase 1, the communication status of all termination devices 30 for the second communication device 20B becomes a communication unauthorized state (unauthorized). For simplicity, below we will refer to the VLAN ID corresponding to the first termination device 30A as "VLAN1" and the VLAN ID corresponding to the second termination device 30B as "VLAN2".

[0029] (2) Phase 2 Phase 2 is the phase in which the second communication device 20B, which was pre-configured in Phase 1, is physically connected to the network of the communication system 1. Specifically, in Phase 2, the second communication device 20B is connected to the second higher-level device 10B. Note that the communication management table of the second communication device 20B remains unchanged in Phase 2 and is the same as the communication management table T1A registered in Phase 1. In other words, in Phase 2 as well, the communication status of all termination devices 30 to the second communication device 20B remains in the communication unauthorized state (unauthorized).

[0030] (3) Third Phase The third phase is the phase in which the second communication device 20B, which was connected to the second higher-level device 10B in the second phase, becomes able to communicate with the second higher-level device 10B. The communication management table of the second communication device 20B remains unchanged in the third phase and is the same as the contents of the communication management table T1A registered in the first phase. That is, even in the third phase, the communication status of all termination devices 30 to the second communication device 20B remains in the communication not permitted state (not permitted). For this reason, even in the third phase, the second communication device 20B is controlled not to perform MAC address learning for all communication devices 20.

[0031] (4) Phase 4 Phase 4 is the phase in which the physical connection of the second termination device 30B to be switched is changed from the first communication device 20A to the second communication device 20B. In Phase 4, after the connection of the second termination device 30B is switched, the communication status of the second termination device 30B to be switched is changed from a communication unauthorized state (unauthorized) to a communication authorized state (authorized) (communication management table T1B). This change is made, for example, by the administrator of communication system 1. As a result of this change, the second communication device 20B performs MAC address learning on frames of VLAN #2 related to the second user terminal 40B among the frames received from the second upper-level device 10B, and can detect user loops (dashed line frames) that may occur for VLAN #2 due to factors other than the switching of the destination.

[0032] On the other hand, for the first termination device 30A, which is not subject to switching, the communication status remains unauthorized (unauthorized) even after the destination of the second termination device 30B is changed. Therefore, the second communication device 20B does not perform MAC address learning for VLAN #1 frames related to the first user terminal 40A even after the destination of the second termination device 30B is changed. With this MAC address learning control method, the second communication device 20B can be prevented from performing MAC address learning for uplink frames from the second user terminal 40B (which is connected to the second termination device 30B that is subject to switching) with respect to downlink communication from the second upper-level device 10B. As a result, the second communication device 20B that is the destination of the switching can suppress the detection of a user loop for the second user terminal 40B that is subject to switching when the destination is switched.

[0033] In other words, while conventional MAC address learning was performed for all frames received from other devices, the second communication device 20B in this embodiment is configured to determine whether or not to perform MAC address learning based on the communication status (communication permitted or communication not permitted). Furthermore, before switching the connection destination of the second termination device 30B from the first communication device 20A to the second communication device 20B, MAC address learning is disabled for at least the VLAN to be switched before switching the destination, thereby suppressing the detection of user loops during the switch for the second user terminal 40B to be switched.

[0034] Therefore, according to the second communication device 20B of the embodiment described above, it is possible to suppress a decrease in the availability of the communication system 1 when the first communication device 20A is replaced.

[0035] Figure 9 shows an example configuration of a communication device 20 according to an embodiment. The communication device 20 comprises, for example, a communication unit 210, a storage unit 220, and a control unit 230. The control unit 230 is configured using a processor such as a CPU (Central Processing Unit) and memory. The control unit 230 functions as a communication control unit 221, a MAC address learning unit 222, and a management unit 223 when the processor executes a program. Note that all or part of each function of the control unit 230 may be implemented using hardware such as an ASIC (Application Specific Integrated Circuit), a PLD (Programmable Logic Device), or an FPGA (Field Programmable Gate Array). The above program may be recorded on a computer-readable recording medium. Computer-readable recording media include, for example, portable media such as flexible disks, magneto-optical disks, ROMs, CD-ROMs, semiconductor storage devices (e.g., SSDs: Solid State Drives), and storage devices such as hard disks and semiconductor storage devices built into a computer system. The above program may be transmitted via a telecommunications line.

[0036] The communication unit 210 is a communication device. The communication unit 210 may be configured, for example, as a network interface. The communication unit 210 communicates data with other devices via the network NW in accordance with the control of the control unit 230. The communication unit 210 may be a device that performs wireless communication or a device that performs wired communication.

[0037] The storage unit 220 is configured using a storage device such as a magnetic hard disk drive or a semiconductor storage device. The storage unit 220 stores data used by the control unit 230. The storage unit 220 is used, for example, as an area for storing the communication management table T1.

[0038] The control unit 230 controls communication between the communication device 20 and other devices. More specifically, the control unit 230 comprises a communication control unit 231, a MAC address learning unit 232, and a management unit 233. The communication control unit 231 performs communication control based on MAC addresses and communication control based on IP (Internet Protocol). The MAC address learning unit 232 performs MAC address learning based on the communication frame received by the communication device 20, and stores the MAC address of the source of the communication frame in association with the interface of the communication device 20 (such as MAC address or VLAN ID). The MAC address learning unit 232 determines whether or not to perform MAC address learning for downlink communication for each termination device 30 that the communication device 20 accommodates, based on the communication status of each termination device 30, using the MAC address learning control method described above. The management unit 233 manages a communication management table T1 for determining whether or not to perform MAC address learning. The management unit 233 may be configured to receive operations from the administrator of the communication device 1 and manage the communication management table T1 in accordance with those operations. Furthermore, if the communication status of each termination device 30 (communication permitted or communication not permitted) is controlled by the communication control unit 231, the management unit 233 may be configured to manage the communication management table T1 based on the control results of the communication control unit 231.

[0039] <Modification> Figures 8 and 9 illustrate the changes in system state during switching when the communication system 1 of the embodiment is applied to the optical communication system 2. For example, Figures 8 and 9 show an example in which the communication system 1 of the embodiment is applied to the optical communication system 2 by defining the authentication state by MAC address authentication of the OLT (Optical Line Termination) as the communication permission setting. In this case, the communication permission setting is updated by the MAC address authentication function of the OLT according to the physical connection status between the ONU and the OLT. In this case, when updating the OLT in the optical communication system 2, it is only necessary to change the destination of the ONU from the old OLT to the new OLT, and it is possible to suppress the detection of user loops and the occurrence of communication interruptions during switching.

[0040] In the above embodiment, we described a case where MAC address learning is not performed for all terminal devices 30 in the second communication device 20B before switching the destination of the second terminal device 30B. However, in order to prevent user loops related to the second terminal device 30B from being detected during the switch, MAC address learning may be omitted only for the second terminal device 30B that is being switched.

[0041] In the above embodiment, we described a case where, after switching the destination of the second termination device 30B, the second communication device 20B performs MAC address learning for the second termination device 30B that is subject to switching, but does not perform MAC address learning for the first termination device 30A that is not subject to switching. However, regardless of whether or not they are subject to switching, MAC address learning may be performed for all termination devices 30 after the switch.

[0042] While embodiments of this invention have been described in detail above with reference to the drawings, the specific configuration is not limited to these embodiments and includes designs and the like that do not depart from the spirit of this invention.

[0043] The present invention relates to a system that communicates using MAC (Media Access Control) addresses and is applicable to systems where the connection destination of a communication device may be changed.

[0044] 1...Communication system, 2...Optical communication system, 10...Higher-level device, 10A...First higher-level device, 10B...Second higher-level device, 20...Communication device, 20A...First communication device, 20B...Second communication device, 30...Terminal device, 30A...First terminal device, 30B...Second terminal device, 40...User terminal, 40A...First user terminal, 40B...Second user terminal, 91...First communication device, 92...Second communication device, 93...First higher-level device, 94...Second higher-level device, 95...Terminal device, 96...User terminal

Claims

1. A communication device that relays communication between a lower-level device and a higher-level device, comprising: a MAC address learning unit that learns the MAC (Media Access Control) address of the source device of a downlink communication frame based on a downlink communication frame from the higher-level device; and a management unit that manages a communication management table for determining whether or not to perform MAC address learning, wherein the communication management table maintains the connection status with the communication device for each lower-level device, and the MAC address learning unit determines whether or not to perform MAC address learning for each lower-level device based on the connection status for each lower-level device.

2. The communication device according to claim 1, wherein the MAC address learning unit does not perform MAC address learning for the subordinate device when the subordinate device is in a communication-unauthorized state and is not permitted to communicate with the communication device, and performs MAC address learning for the subordinate device when the subordinate device is in a communication-authorized state and is permitted to communicate with the communication device.

3. The communication device according to claim 2, wherein the communication management table includes the connection status of other subordinate devices housed in other communication devices, and in the communication management table, the connection status of the other subordinate devices is changed from a communication-unauthorized state to a communication-authorized state when the destination of the other subordinate devices is changed from the other communication device to the communication device itself.

4. A control method for a communication device that relays communication between a lower-level device and a higher-level device, comprising: a MAC address learning process that learns the MAC (Media Access Control) address of the source device of a downlink communication frame based on a downlink communication frame from the higher-level device; and a management process that manages a communication management table for determining whether or not to perform MAC address learning, wherein the communication management table maintains the connection status with the communication device for each lower-level device, and the MAC address learning process determines whether or not to perform MAC address learning for each lower-level device based on the connection status for each lower-level device.

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