Optical Communication Device and Program

Abstract

To reduce a period of a communication failure.SOLUTION: An OLT 100 includes: a volatile storage device 102 that stores an authentication table 120 containing an address assign to a client device 300 from a DHCP server 400 and information on the client device; a non-volatile storage device 103 that stores backup information 130 as information similar to the authentication table 120; and a control part 110. The control part 110 performs an instruction to an ONU 200 when a failure occurs in the OLT 100, and after the OLT 100 is restored so that the client device 300 is not connected to an internet network 20, stores the backup information 130 stored in the non-volatile storage device 103 into the volatile storage device 102, and performs an instruction to the ONU 200 so that the client device 300 can be connected to the internet network 20.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present disclosure relates to an optical communication device and program thereof.

Background Art

[0002] Communication systems including a PON (Passive Optical Network) system, which is an optical communication system, are known. The PON system includes an optical communication device (also referred to as a "parent station device") installed in a communications carrier's premises and a plurality of optical communication devices (also referred to as "sub-station devices") installed on the subscriber side. The parent station device is called an OLT (Optical Line Termination). The sub-station device is called an ONU (Optical Network Unit).

[0003] In a communication system including a PON system, IPoE (IP over Ethernet (registered trademark)) is used as a technology for connecting to a higher-level network such as the Internet. In addition, the communication system includes a DHCP (Dynamic Host Configuration Protocol) server. The DHCP server can assign an IP (Internet Protocol) address to a client device connected to the ONU. The client device can connect to the higher-level network using the assigned IP address.

[0004] Here, a technique for causing a client device to acquire an IP address has been proposed. For example, when a failure occurs in the OLT, the ONU causes the client device to execute an IP address acquisition request (see Patent Document 1).

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] By the way, in a communication system, when a failure occurs in the OLT, filtering is executed so that the client device connected to the ONU cannot be connected to the network. There is a method to cancel the filtering. This is a method of canceling the filtering at the timing when the client device transmits a DHCP renew message. However, the client device does not transmit a DHCP renew message until it approaches the expiration of the lease time. Therefore, in the client device, the communication failure continues until the lease time expires.

[0007] An object of the present disclosure is to shorten the period of communication failure.

Means for Solving the Problems

[0008] An optical communication device according to an aspect of the present disclosure is provided. The optical communication device is a master station device that communicates with a slave station device that communicates with a client device and is connected to the network, and manages an address used when connecting to the network. The optical communication device includes a volatile storage device that stores authentication information including an address assigned to the client device from the management device and information regarding the client device, a non-volatile storage device that stores backup information that is the same information as the authentication information, and a control unit. After a failure occurs in the master station device and the master station device recovers, the control unit instructs the slave station device so that the client device cannot be connected to the network, stores the backup information stored in the non-volatile storage device in the volatile storage device, and instructs the slave station device so that the client device can be connected to the network.

Effects of the Invention

[0009] According to the present disclosure, the period of communication failure can be shortened.

Brief Description of the Drawings

[0010]

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Mode for Carrying Out the Invention

[0011] Hereinafter, embodiments will be described with reference to the drawings. The following embodiments are merely examples, and various modifications are possible within the scope of the present disclosure.

[0012] Embodiment 1. FIG. 1 is a diagram showing a communication system according to Embodiment 1. The communication system includes a PON system 10, client devices 300, 301, 302, 303, 304, a DHCP server 400, a switch 600, and an HGW (Home Gate Way) 700. The PON system 10 includes an OLT 100, ONUs 200, 201, 202, and an optical coupler 500.

[0013] The OLT 100 and the optical coupler 500 are connected by an optical fiber. The ONUs 200 to 202 and the optical coupler 500 are connected by an optical fiber. The OLT 100 is also referred to as a master station device or an optical communication device. The OLT 100 communicates with the ONUs 200 to 202 and the DHCP server 400. Also, the OLT 100 is connected to the Internet network 20. The Internet network 20 is also referred to as a network. The ONUs 200 to 202 are also referred to as slave station devices.

[0014] The client devices 300 to 304 are also referred to as DHCP client devices. For example, the client devices 300 to 304 are PCs (Personal Computers) or televisions. The client devices 300 to 304 communicate with the ONUs 200 to 202. The client devices 300 to 304 access the Internet network 20 using the assigned IP (Internet Protocol) addresses. For example, the client device 300 accesses the Internet network 20 via the ONU 200 and the OLT 100 using the assigned IP address.

[0015] The DHCP server 400 manages the IP addresses used when connecting to the Internet network 20. The DHCP server 400 assigns and releases IP addresses based on DHCP. Note that the DHCP server 400 is also referred to as a management device.

[0016] Next, the assignment of IP addresses will be described. FIG. 2 is a sequence diagram showing the IP address allocation process of Embodiment 1. FIG. 2 illustrates the case where the DHCP server 400 assigns an IP address to the client device 300. Also, FIG. 2 omits the optical coupler 500.

[0017] (Step ST101) The client device 300 sends a DHCP discover message to the DHCP server 400. The DHCP discover message is a message requesting the allocation of an IP address. (Step ST102) The DHCP server 400 sends a DHCP offer message to the client device 300. The DHCP offer message is a message indicating an IP address that the client device 300 can use.

[0018] (Step ST103) If there is no problem with the IP address indicated by the DHCP offer message, the client device 300 sends a DHCP request message to the DHCP server 400. The DHCP request message is a message formally requesting the DHCP server 400 to allocate an IP address. (Step ST104) The DHCP server 400 sends a DHCP ack message to the client device 300. The DHCP ack message is a message for causing the client device 300 to set an IP address. The client device 300 sets the IP address according to the DHCP ack message. Thereby, the client device 300 can connect to the Internet network 20 using the IP address.

[0019] An expiration date is set for the IP address assigned to the DHCP server 400. The expiration date is also referred to as the lease time. When the client device 300 wants to use the IP address beyond the lease time, it can update the lease time of the IP address by sending a DHCP renew message to the DHCP server 400 around the expiration of the lease time.

[0020] In addition, DHCP defines a DHCP forcerenew message for forcibly executing the acquisition of an IP address. For example, when the client device 300 receives the DHCP forcerenew message, it sends a DHCP discover message to the DHCP server 400. Thereafter, by executing steps ST102 to 104, the client device 300 re-acquires an IP address.

[0021] Next, the main hardware configuration of the OLT 100 will be described. FIG. 3 is a diagram showing the hardware configuration of the OLT according to the first embodiment. The OLT 100 includes a processor 101, a volatile memory device 102, and a non-volatile memory device 103.

[0022] The processor 101 controls the entire OLT 100. For example, the processor 101 is a CPU (Central Processing Unit), an FPGA (Field Programmable Gate Array), or the like. The processor 101 may be a multi-processor. In addition, the OLT 100 may include a processing circuit.

[0023] The volatile memory device 102 is the main memory device of the OLT 100. For example, the volatile memory device 102 is a RAM (Random Access Memory). The non-volatile memory device 103 is the auxiliary storage device of the OLT 100. For example, the non-volatile memory device 103 is an HDD (Hard Disk Drive) or an SSD (Solid State Drive).

[0024] The ONUs 200 to 202, the client devices 300 to 304, and the DHCP server 400 each include a processor, a volatile memory device, and a non-volatile memory device, similar to the OLT 100.

[0025] Here, the processes executed by the OLT 100, ONU 200, client device 300, and DHCP server 400 are the same as the processes executed by each of the OLT 100, ONU 201, DHCP server 400, and client devices 301, 302, 303. Also, the processes executed by the OLT 100, ONU 200, client device 300, and DHCP server 400 are the same as the processes executed by the OLT 100, ONU 202, client device 304, and DHCP server 400. Therefore, the processes executed by the OLT 100, ONU 200, client device 300, and DHCP server 400 will be mainly described.

[0026] FIG. 4 is a block diagram showing the functions of the OLT and ONU according to Embodiment 1. The OLT 100 includes a control unit 110. The control unit 110 includes a PON control unit 111 and a message processing unit 112.

[0027] Part or all of the control unit 110, PON control unit 111, and message processing unit 112 may be realized by a processing circuit. Part or all of the control unit 110, PON control unit 111, and message processing unit 112 may be realized as modules of a program executed by the processor 101.

[0028] The ONU 200 includes a control unit 210 and an interface unit 220. The control unit 210 includes a PON control unit 211 and a packet filter unit 212. The interface unit 220 includes a port 221.

[0029] Part or all of the control unit 210, PON control unit 211, packet filter unit 212, and interface unit 220 may be realized by a processing circuit included in the ONU 200. Part or all of the control unit 210, PON control unit 211, packet filter unit 212, and interface unit 220 may be realized as modules of a program executed by a processor included in the ONU 200.

[0030] First, the functions of the OLT 100 will be described.

[0031] The PON control unit 111 can mutually convert optical signals and electrical signals. Also, the PON control unit 111 transmits the information generated by the message processing unit 112 to the ONU 200.

[0032] The message processing unit 112 executes snooping. For example, the message processing unit 112 acquires the DHCP request message transmitted by the client device 300. The message processing unit 112 acquires the physical address of the client device 300, the information of the ONU to which the client device 300 is connected (i.e., the information indicating the ONU 200), and the port information of port 221 from the DHCP request message. For example, the physical address is a MAC (Media Access Control) address. Hereinafter, the physical address shall be the MAC address.

[0033] Also, for example, the message processing unit 112 acquires the DHCP ack message transmitted by the client device 300. The message processing unit 112 acquires the IP address from the DHCP ack message. The IP address is the IP address assigned from the DHCP server 400 to the client device 300.

[0034] The message processing unit 112 generates combination information using the MAC address, IP address, information indicating the ONU 200, and port information acquired by snooping. The message processing unit 112 registers the combination information in the authentication table 120. Thereby, the user authentication registration of the client device 300 in the PON system 10 is completed. The OLT 100 can execute user authentication for the client device 300 accessing the Internet network 20 using the combination information. Here, the authentication table 120 is also referred to as authentication information. Also, the MAC address is also referred to as information regarding the client device 300.

[0035] In addition, the message processing unit 112 generates combination information corresponding to each of the client devices 301 to 304. The message processing unit 112 registers the generated plurality of combination information in the authentication table 120.

[0036] Here, the authentication table 120 is stored in the volatile storage device 102. Therefore, when a failure occurs in the OLT 100, the authentication table 120 disappears. Therefore, the message processing unit 112 stores backup information 130, which is the same information as the authentication table 120, in the non-volatile storage device 103. The backup information 130 is updated periodically. Here, the authentication table 120 is also referred to as the Binding Table.

[0037] The message processing unit 112 registers the combination information in the authentication table 120 and generates packet filter information. Specifically, the message processing unit 112 generates packet filter information using the combination information.

[0038] The packet filter information includes the IP address assigned to the client device 300 and filter execution information. Valid or invalid is set in the filter execution information. Here, the packet filter information is received by the packet filter unit 212. When valid is set in the filter execution information, the packet filter unit 212 determines whether the IP address included in the packet transmitted by the client device 300 matches the IP address indicated by the packet filter information. When they match, the packet filter unit 212 allows the packet transmitted by the client device 300 to pass through. On the other hand, when invalid is set in the filter execution information, the packet filter unit 212 discards the packet including the IP address indicated by the packet filter information. That is, the packet filter unit 212 discards the packet transmitted by the client device 300. The client device 300 cannot connect to the Internet network 20 because the packet is discarded. The message processing unit 112 transmits the packet filter information to the ONU 200 via the PON control unit 111.

[0039] Next, the functions of the ONU 200 will be described.

[0040] The PON control unit 211 can mutually convert optical signals and electrical signals. Also, the PON control unit 211 transmits the packet filter information received from the OLT 100 to the packet filter unit 212. The packet filter unit 212 passes or discards the packets transmitted by the client device 300 using the packet filter information. The interface unit 220 communicates with the client device 300 via the port 221.

[0041] Here, a failure may occur in the OLT 100. For example, the failure is a malfunction or a power cut. As described above, when a failure occurs in the OLT 100, the authentication table 120 disappears. When the authentication table 120 disappears, the OLT 100 sets the filter execution information to invalid. The reason for setting it to invalid is as follows. The OLT 100 manages the client device 300 to which an IP address is assigned in the authentication table 120. When the authentication table 120 disappears, the OLT 100 cannot manage the client device 300. Then, the OLT 100 sets the filter execution information to invalid in order to prevent a client device 300 that is not managed by the OLT 100 from communicating via the OLT 100.

[0042] Here, there is a method for setting the filter execution information set to invalid to valid. This method will be described. The IP address assigned to the client device 300 is a dynamic IP address. An expiration date is set for the dynamic IP address. The expiration date is also referred to as the lease time. The client device 300 can send a DHCP renew message to the DHCP server 400 when the lease time is about to expire. After detecting the DHCP renew message by snooping, the OLT 100 sets the filter execution information to valid. However, this method has the following problems. A long time is set for the lease time. Therefore, the client device 300 does not send a DHCP renew message until the lease time approaches expiration. Therefore, in the client device 300, the communication failure continues until the lease time expires.

[0043] Also, the OLT 100 can be connected to a maximum of 64 ONUs. Many client devices are connected to the ONUs. If all client devices do not send a DHCP renew message as described above, the communication failures in the communication system will not be eliminated.

[0044] Therefore, in Embodiment 1, it will be described that even when a communication failure occurs in the client device, it can recover from the communication failure in a short time.

[0045] Next, the processing executed in the communication system will be described using a sequence diagram. FIG. 5 is a sequence diagram (Part 1) showing an example of the processing executed in the communication system of Embodiment 1. (Step ST111) The client device 300 sends a DHCP discover message to the DHCP server 400. (Step ST112) The DHCP server 400 sends a DHCP offer message to the client device 300. (Step ST113) The client device 300 sends a DHCP request message to the DHCP server 400. Also, the message processing unit 112 performs snooping. As a result, the message processing unit 112 obtains the MAC address of the client device 300 from the DHCP request message and the like.

[0046] (Step ST114) The DHCP server 400 transmits a DHCP ack message to the client device 300. Also, the message processing unit 112 performs snooping. As a result, the message processing unit 112 obtains an IP address from the DHCP ack message. The message processing unit 112 generates combination information using the MAC address, IP address, information indicating the ONU 200, and port information obtained by snooping. The message processing unit 112 registers the combination information in the authentication table 120. The message processing unit 112 stores backup information 130, which is the same information as the authentication table 120, in the non-volatile storage device 103. The message processing unit 112 generates packet filter information.

[0047] (Step ST115) The message processing unit 112 of the OLT 100 transmits the packet filter information to the ONU 200 via the PON control unit 111. (Step ST116) The message processing unit 112 of the OLT 100 transmits an effective setting instruction to the ONU 200 via the PON control unit 111. (Step ST117) The packet filter unit 212 of the ONU 200 sets the validity to the filter execution information corresponding to the IP address assigned to the client device 300.

[0048] FIG. 6 is a sequence diagram (part 2) showing an example of processing executed in the communication system of Embodiment 1. (Step ST121) A failure occurs in the OLT 100. For example, a power cut occurs in the OLT 100. As a result, the authentication table 120 disappears. (Step ST122) The communication state (hereinafter, link state) between the OLT 100 and the ONU 200 transitions to a disconnected state (hereinafter, link down).

[0049] (Step ST123) The OLT 100 recovers when power is turned on. (Step ST124) The PON control unit 111 of the OLT 100 sets the link state with the ONU 200 to a connected state (hereinafter, link up).

[0050] (Step ST125) The PON control unit 111 of the OLT 100 detects link up. The PON control unit 111 of the OLT 100 sends a link up notification to the message processing unit 112. The message processing unit 112 of the OLT 100 sends an invalid setting instruction to the ONU 200 via the PON control unit 111. In other words, the message processing unit 112 of the OLT 100 instructs the ONU 200 so that the client device 300 does not connect to the Internet network 20.

[0051] (Step ST126) The packet filter unit 212 of the ONU 200 sets invalid in the filter execution information corresponding to the IP address assigned to the client device 300. As a result, the client device 300 cannot access the Internet network 20. That is, the client device 300 cannot connect to the Internet network 20 with the address assigned from the DHCP server 400.

[0052] (Step ST127) The message processing unit 112 of the OLT 100 stores the backup information 130 stored in the non-volatile storage device 103 in the volatile storage device 102. (Step ST128) The message processing unit 112 of the OLT 100 sends a valid setting instruction to the ONU 200 via the PON control unit 111. In other words, the message processing unit 112 of the OLT 100 instructs the ONU 200 so that the client device 300 can connect to the Internet network 20.

[0053] In addition, when the ONU 200 detects a link down, the ONU 200 may delete the packet filter information. In such a case, the message processing unit 112 generates the packet filter information based on the backup information 130 and transmits the packet filter information to the ONU 200. Then, the message processing unit 112 transmits an effective setting instruction to the ONU 200 via the PON control unit 111.

[0054] (Step ST129) The packet filter unit 212 of the ONU 200 sets the filter execution information corresponding to the IP address assigned to the client device 300 to effective. As a result, the client device 300 can access the Internet network 20.

[0055] Also, in step ST125, when the PON control unit 111 of the OLT 100 detects a link up with the ONUs 201 and 202, the message processing unit 112 of the OLT 100 transmits an invalid setting instruction to the ONUs 201 and 202 via the PON control unit 111. As a result, the packet filter units of the ONUs 201 and 202 set the filter execution information to invalid.

[0056] Furthermore, in step ST128, the message processing unit 112 of the OLT 100 transmits an effective setting instruction to the ONUs 201 and 202 via the PON control unit 111. As a result, the packet filter units of the ONUs 201 and 202 set the filter execution information to effective. As a result, the client devices 301 to 304 can access the Internet network 20.

[0057] Next, the processing after the message processing unit 112 stores the backup information 130 in the volatile storage device 102 will be described using a flowchart. FIG. 7 is a flowchart showing an example of the processing after storing the backup information in Embodiment 1. Also, in FIG. 7, the case where the packet filter information is generated will be described. (Step S11) The message processing unit 112 generates packet filter information based on the backup information 130 and transmits the packet filter information to the ONU 200. Also, the message processing unit 112 transmits an effective setting instruction to the ONU 200 via the PON control unit 111.

[0058] (Step S12) The message processing unit 112 transmits a DHCP forcerenew message to the client device 300 via the PON control unit 111. (Step S13) The PON control unit 111 determines whether a DHCP discover message is received within a predetermined period. The DHCP discover message is a response to the DHCP forcerenew message. If a DHCP discover message is received, the process proceeds to step S14. If a DHCP discover message is not received, the process proceeds to step S17.

[0059] (Step S14) The message processing unit 112 determines whether the MAC address and IP address included in the DHCP discover message are included in the backup information 130. If the MAC address and IP address are not included in the backup information 130, the process proceeds to step S15. If the MAC address and IP address are included in the backup information 130, the process proceeds to step S16.

[0060] (Step S15) The message processing unit 112 transmits the DHCP discover message to the DHCP server 400 via the PON control unit 111. Thereby, the client device 300 can obtain a new IP address. For example, step S15 is executed when the backup information 130 is not in the latest state, when the lease time of the IP address has expired during a communication failure, when the client device 300 has acquired an IP address before the backup information 130 is stored in the volatile memory device 102, and so on.

[0061] (Step S16) Since the communication failure of the client device 300 whose MAC address is included in the DHCP discover message has been resolved, the message processing unit 112 does not need to send the DHCP discover message to the DHCP server 400. Therefore, the message processing unit 112 discards the DHCP discover message. By discarding the DHCP discover message, the OLT 100 can prevent a new IP address from being assigned to the client device 300.

[0062] (Step S17) The message processing unit 112 sends a DHCP release message to the DHCP server 400 via the PON control unit 111. The DHCP release message includes the IP address assigned to the client device 300. By sending the DHCP release message, the IP address is returned. (Step S18) The message processing unit 112 deletes the combination information of the client device 300 from the backup information 130.

[0063] In FIG. 7, the processing between the OLT 100 and the client device 300 is described. The same processing is performed between the OLT 100 and the client devices 301 to 304.

[0064] According to Embodiment 1, the OLT 100 stores the backup information 130 in the volatile memory device 102 and transmits a valid setting instruction to the ONU 200. As a result, the communication failure is resolved in the client device 300. Thereby, the client device 300 can access the Internet network 20 without waiting for the expiration of the lease time of the IP address. That is, the OLT 100 can shorten the communication failure period of the client device 300.

[0065] Also, after the OLT 100 stores the backup information 130 in the volatile memory device 102, it transmits a valid setting instruction to the ONUs 201 and 202. As a result, the communication failure is resolved in the client devices 301 to 304. Thereby, in the communication system, the communication failure period is shortened.

[0066] Embodiment 2. Next, Embodiment 2 will be described. In Embodiment 2, matters different from Embodiment 1 will be mainly described. And in Embodiment 2, the description of matters common to Embodiment 1 will be omitted. In Embodiment 1, the case where the ONU has packet filter information and the ONU performs filtering was described. In Embodiment 2, the case where the OLT has packet filter information and the OLT performs filtering will be described.

[0067] FIG. 8 is a diagram showing the communication system of Embodiment 2. The communication system includes a PON system 10. The PON system 10 includes an OLT 100a, ONUs 200a, 201a, 202a, and an optical coupler 500.

[0068] FIG. 9 is a block diagram showing the functions of the OLT and ONU in Embodiment 2. The OLT 100a has a packet filter unit 140. Part or all of the packet filter section 140 may be implemented by a processing circuit. Part or all of the packet filter section 140 may be implemented as a module of a program executed by the processor 101. The packet filter section 140 uses packet filter information to pass or discard packets transmitted by the client devices 300 to 304.

[0069] ONUs 200a, 201a, and 202a are the same as ONUs 200, 201, and 202, except that they do not have a packet filter section. Therefore, a detailed description of ONUs 200a, 201a, and 202a is omitted.

[0070] Next, the processing executed in the communication system will be described using a sequence diagram. FIG. 10 is a sequence diagram (part 1) showing an example of the processing executed in the communication system of Embodiment 2. (Step ST131) The client device 300 transmits a DHCP discover message to the DHCP server 400. (Step ST132) The DHCP server 400 transmits a DHCP offer message to the client device 300.

[0071] (Step ST133) The client device 300 transmits a DHCP request message to the DHCP server 400. Also, the message processing section 112 performs snooping. Thereby, the message processing section 112 acquires the MAC address of the client device 300 and the like from the DHCP request message.

[0072] (Step ST134) The DHCP server 400 transmits a DHCP ack message to the client device 300. Also, the message processing section 112 performs snooping. Thereby, the message processing section 112 acquires the IP address from the DHCP ack message.

[0073] (Step ST135) The message processing unit 112 of the OLT 100a generates combination information using the MAC address, IP address, information indicating the ONU 200, and port information obtained by snooping. The message processing unit 112 registers the combination information in the authentication table 120. The message processing unit 112 stores backup information 130, which is the same information as the authentication table 120, in the non-volatile storage device 103. The message processing unit 112 generates packet filter information.

[0074] (Step ST136) The message processing unit 112 of the OLT 100a transmits a valid setting instruction to the packet filter unit 140. The packet filter unit 140 sets valid in the filter execution information corresponding to the IP address assigned to the client device 300.

[0075] FIG. 11 is a sequence diagram (part 2) showing an example of the processing executed in the communication system of Embodiment 2. (Step ST141) A failure occurs in the OLT 100a. For example, in the OLT 100a, a power cut occurs. As a result, the authentication table 120 disappears. (Step ST142) The link state between the OLT 100a and the ONU 200a transitions to link down.

[0076] (Step ST143) The OLT 100a recovers when the power is turned on. (Step ST144) The PON control unit 111 of the OLT 100a brings the link state with the ONU 200a to link up.

[0077] (Step ST145) The PON control unit 111 of the OLT 100a detects link-up. The PON control unit 111 of the OLT 100a sends a link-up notification to the message processing unit 112. The message processing unit 112 of the OLT 100a sends an invalid setting instruction to the packet filter unit 140. The packet filter unit 140 sets invalid in the filter execution information corresponding to the IP address assigned to the client device 300. In this way, the packet filter unit 140 controls so that the client device 300 does not connect to the Internet network 20. As a result, the client device 300 cannot access the Internet network 20. That is, the client device 300 cannot connect to the Internet network 20 with the address assigned from the DHCP server 400.

[0078] (Step ST146) The message processing unit 112 of the OLT 100a stores the backup information 130 stored in the non-volatile storage device 103 in the volatile storage device 102. (Step ST147) The message processing unit 112 of the OLT 100a sends a valid setting instruction to the packet filter unit 140. The packet filter unit 140 sets valid in the filter execution information corresponding to the IP address assigned to the client device 300. In this way, the packet filter unit 140 controls so that the client device 300 can connect to the Internet network 20. As a result, the client device 300 can access the Internet network 20.

[0079] Also, in step ST145, when the PON control unit 111 of the OLT 100a detects link-up with the ONUs 201a and 202a, the message processing unit 112 of the OLT 100a sends an invalid setting instruction to the packet filter unit 140. As a result, the packet filter unit 140 sets invalid in the filter execution information corresponding to the client devices 301 to 304.

[0080] Furthermore, in step ST147, the message processing unit 112 of the OLT 100a transmits a valid setting instruction to the packet filter unit 140. As a result, the packet filter unit 140 sets all filter execution information to valid. As a result, the client devices 301 to 304 can access the Internet network 20.

[0081] Also, the OLT 100a may execute the process of FIG. 7 except for step S11.

[0082] According to the second embodiment, the OLT 100a stores the backup information 130 in the volatile storage device 102 and sets the filter execution information corresponding to the client device 300 to valid. As a result, the communication failure is resolved in the client device 300. Thereby, the client device 300 can access the Internet network 20 without waiting for the expiration of the lease time of the IP address. That is, the OLT 100a can shorten the period of the communication failure of the client device 300.

[0083] Also, after storing the backup information 130 in the volatile storage device 102, the OLT 100a sets the filter execution information corresponding to the client devices 301 to 304 to valid. As a result, the communication failure is resolved in the client devices 301 to 304. Thereby, in the communication system, the period of the communication failure is shortened.

[0084] The features in each of the above-described embodiments can be appropriately combined with each other.

Explanation of Reference Numerals

[0085] 10 PON system, 20 Internet network, 100, 100a OLT, 101 processor, 102 volatile memory device, 103 non-volatile memory device, 110 control unit, 111 PON control unit, 112 message processing unit, 120 authentication table, 130 backup information, 140 packet filter unit, 200~202, 200a~202a ONU, 210 control unit, 211 PON control unit, 212 packet filter unit, 220 interface unit, 221 port, 300~304 client device, 400 DHCP server, 500 optical coupler, 600 switch, 700 HGW.

Claims

1. An optical communication device which is a master station device that communicates with a slave station device communicating with a client device and connects to the network, and manages an address used when connecting to the network, comprising: a volatile memory device that stores authentication information including an address assigned to the client device from the management device and information regarding the client device; a non-volatile memory device that stores backup information which is the same information as the authentication information; a control unit; and having: After a failure occurs in the master station device and the master station device recovers, the control unit instructs the slave station device so that the client device does not connect to the network, stores the backup information stored in the non-volatile memory device in the volatile memory device, and instructs the slave station device so that the client device can connect to the network. Optical communication device.

2. An optical communication device which is a master station device that communicates with a slave station device communicating with a client device and connects to the network, and manages an address used when connecting to the network, comprising: a volatile memory device that stores authentication information including an address assigned to the client device from the management device and information regarding the client device; a non-volatile memory device that stores backup information which is the same information as the authentication information; a control unit; a packet filter unit; and having: After a failure occurs in the master station device and the master station device recovers, the packet filter unit controls so that the client device does not connect to the network. After control is performed so that the client device does not connect to the network, the control unit stores the backup information stored in the non-volatile memory device in the volatile memory device. After the backup information is stored in the volatile memory device, the packet filter unit controls so that the client device can connect to the network. Optical communication device.

3. When the control unit transmits a DHCP force renew message to the client device and receives a DHCP discover message, if the information indicating the client device contained in the DHCP discover message and the address are included in the backup information, the control unit discards the DHCP discover message. The optical communication device according to claim 1 or 2. **Claim 4**: A program for causing a processor to function as the control unit of the optical communication device according to any one of claims 1, 2, and 3. **Claim 5**: A program for causing a processor to function as the packet filter unit of the optical communication device according to claim 2 or claim 3 that cites claim 2.

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