JP2007067601A - Optical line terminal switching method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a technique of switching an active optical line terminal (OLT) into a standby OLT without causing a data loss. <P>SOLUTION: An L3 switch (40) with a port mirror ring function is located to an upstream of OLTs (10a, 10b), and a 2:1 photocoupler (60) is located to the downstream. Prior to starting the switching, management information and setting information are transferred from the OLT (10a) to the OLT (10b). When a particular frame for denoting start of the switching is inputted from a switch (40) to the OLTs (10a, 10b), the OLT (10a) stops capturing downlink data, and the OLT (10b) starts capturing the downlink data. The OLT (10a) temporarily halts band allocation to ONUs (68-1 to 68-n), instructs the OLT (10b) to capture uplink data and to restart the band allocation to the ONUs (68-1 to 68-n). When the OLT (10a) has no downlink data, the OLT (10a) transfers the management information to the OLT (10b). The OLT (10b) is brought into an ordinary operation. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for switching a center-side optical terminal device of an optical transmission system that can accommodate a plurality of users.

  A PON (Passive Optical Network) system is an optical terminal device OLT (Optical Line Terminal) disposed in a center station and a plurality of user terminal optical terminal devices ONU (Optical Network Unit). An optical transmission system connected via an optical element (for example, Patent Document 1).

The PON system is not only spread as an Internet access line, but is being used as a system that provides broadcasting, data communication, and data in a composite manner. The number of users that can be connected to one system is also increasing.
JP 2005-175599 A

  When using for broadcasting or telephone, disconnection due to failure of network equipment should be avoided as much as possible. OLT replacement needs to be performed as quickly as possible because it leads to a temporary suspension of service to all users under the control. Ideally, no disconnection should occur, but at least it is desirable not to make the user aware of the temporary disconnection.

  The OLT is generally replaced in the case of a failure, but may be replaced with an OLT having an improved function. For example, when a 1 Gbps-based service is being provided, a 1 Gbps OLT is switched to a 1 Gbps / 2 Gbps OLT in preparation for a future higher speed service, for example, a 2 Gbps service. .

  The service interruption time is the time required to switch the optical fiber from the existing OLT to the new OLT, and the new OLT knows all users (ONUs) connected to the optical fiber and their services, and restores the service status. It takes time to complete. The former time can be reduced to zero by arranging a 2: 1 optical coupler in advance between the working OLT and the spare OLT and the optical fiber.

  It is an object of the present invention to provide an optical terminal device switching method that can significantly reduce the time of service interruption.

  The optical termination device switching method according to the present invention is an optical network in which a plurality of user optical termination devices are connected to an optical termination device of a center station via an optical transmission line, and the optical termination device of the center station is changed from a working OLT to a standby OLT. It is a method to switch to. First, a switch having a function of port mirroring of data to the current OLT and the spare OLT is prepared upstream of the current OLT and the spare OLT. Downstream of the working OLT and the spare OLT, downstream signal light is supplied from the working OLT (10a) and the spare OLT to the optical transmission line, and upstream signal light from the optical transmission line is supplied to the working OLT. And an optical coupler to be supplied to the spare OLT is prepared. A control device for controlling switching from the current OLT to the spare OLT is prepared. The spare OLT is activated in a standby mode in which passive operation is performed, and port mirroring of the switch to the current OLT and the spare OLT is enabled. The management information and setting information of the working OLT are transferred to the spare OLT. The downlink data path is switched from the working OLT to the spare OLT. The uplink data path is switched from the working OLT to the backup OLT. Then, the current OLT is completely transferred to the spare OLT.

  According to the present invention, it is possible to switch from the working OLT to the backup OLT without any loss of downlink data. The upstream data transmission can be stopped in a very short time. As a result, the working OLT can be switched to the spare OLT with virtually no instantaneous interruption.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 shows a schematic block diagram of an embodiment of the present invention. In the center station, a current optical terminal device (OLT) 10a, a spare optical terminal device (OLT) 10b, and a control device 30 that controls switching from the working OLT 10a to the spare OLT 10b are provided in the same rack. Be contained. The L3 (Layer 3) switch 40 mediates upstream data between the upstream network and the OLTs 10a and 10b.

  The 2: 1 optical coupler 60 includes a pair of input / output ports and a multiplexing / demultiplexing port. The user-side input / output port of the active OLT 10a is connected to one of the pair of input / output ports, and the other is reserved. The user side input / output port of the OLT 10b is connected. The multiplexing / demultiplexing port of the optical coupler 60 is connected to the multiplexing / demultiplexing port of the 1: n optical coupler 64 via the optical fiber 62 that constitutes the optical transmission line of the PON system. The 1: n optical coupler 64 includes n input / output ports in addition to one multiplexing / demultiplexing port, and each input / output port receives light from each user via different optical fibers 66-1 to 66-n. It connects to a terminal unit (ONU: Optical Network Unit) 68-1 to 68-n.

  The active OLT 10a and the spare OLT 10b have the same configuration and function. The basic operation will be described. The symbol “a” is added to the component of the active OLT 10a, and the symbol “b” is added to the component of the spare OLT 10b.

  The network interface 12a includes a LAN (Local Area Network) transceiver. The network interface 12a supplies the data signal from the switch 40 to the downlink buffer 14a. The downlink buffer 14a transmits a data signal directed to the OLT 10a itself among the data signals from the network interface 12a to the CPU 16a, specifically to any of the subordinate ONUs 68-1 to 68-n. A data signal (downstream signal) to be supplied is supplied to the electric / optical converter 18a. The CPU 16a also supplies control signals and the like to be supplied to the subordinate ONUs 68-1 to 68-n to the downstream buffer 14a. Further, the CPU 16a sniffs the downstream signal in the downstream buffer 14a and performs necessary control.

  The electrical / optical converter 18a converts the data signal from the downstream buffer 14a into an optical signal, and supplies the optical signal to the wavelength division multiplexing (WDM) optical coupler 20a. The WDM optical coupler 20a supplies the downstream optical signal from the electrical / optical converter 18a to one input / output port of the optical coupler 60a. This downstream optical signal enters the optical coupler 64 through the optical coupler 60 and the optical fiber 62, and is divided into n parts here. Each optical signal divided by the optical coupler 64 enters each user's ONUs 68-1 to 68-n via optical fibers 661-1 to 66-n.

  On the other hand, each ONU 68-1 to 68-n outputs the upstream optical signal light to the optical fibers 66-1 to 66-n. The upstream optical signal carries a data signal addressed to the OLTs 10a and 10b and a data signal addressed to a device connected to the upstream network. Data signals addressed to the OLTs 10a and 10b include a control signal and a response signal for establishing a logical link. The optical coupler 64 outputs the upstream optical signal from each of the optical fibers 66-1 to 66-n to the optical fiber 62 from the multiplexing / demultiplexing port. The optical coupler 60 divides the upstream optical signal from the optical fiber 62 into two parts, one is supplied from the input / output port to the WDM coupler 20a of the OLT 10a, and the other is supplied from another input / output port to the WDM coupler 20b of the OLT 10b.

  The WDM coupler 20a supplies the upstream optical signal from the optical coupler 60 to the optical / electrical converter 22a. The optical / electrical converter 22a converts the upstream optical signal from the WDM coupler 20a into an electrical signal and supplies the electrical signal to the upstream buffer 24a. The upstream buffer 24a uses the electrical signal from the optical / electrical converter 22a to send the data signal or the like directed to the OLT 10a itself to the CPU 16a and the remaining data signal, specifically, the data to the device connected to the upstream network. A signal is supplied to the network interface 12a. The CPU 16a also supplies a data signal or the like directed to a device connected to the upstream network to the upstream buffer 24a. Furthermore, the CPU 16a sniffs the data signal in the upstream buffer 24a and performs necessary control. The network interface 12a supplies the data from the upstream buffer 24a to the L3 switch 40.

  The CPU 16a stores information necessary for managing the subordinate ONUs 68-1 to 69-n and various setting information in the memory 26a. The setting information is immutable information set by a reservation, for example, the number of LLIDs (logical link identifiers), VLAN mode validity / invalidity, IGMP Snooping validity / invalidity, and subordinates of each ONU 68-1 to 68-n. Including home gateway re-authentication interval. The management information is information that fluctuates depending on the operation status. Specifically, the number of currently connected ONUs, information for identifying each connected ONU, and assigned to each connected ONU. It consists of a bandwidth allocation amount, an IGMP snooping (Snooping) table, and a MAC address learning table. The MAC address learning table stores actual or virtual MAC addresses that can be allocated to the ONUs to be connected and the services of the subordinate electronic devices and the LAN interface.

  The CPU 16a also performs flow control to prevent data from overflowing from the down buffer 14a and the up buffer 24b. Since the contents of the flow control are well known, detailed description is omitted. Further, the CPU 16a can stop taking in the data of the down buffer 14a and the up buffer 24b, and can discard the data stored in the down buffers 14a and 16a without outputting them to the succeeding apparatus.

  The spare OLT 10b operates in exactly the same manner as the active OLT 10a after switching. However, in the standby state before switching, the backup OLT 10b only intercepts an upstream signal and a downstream signal, but does not output a signal, as will be described in detail later.

  The control device 30 includes a CPU 32 that controls switching from the active OLT 10a to the spare OLT 10b, and a memory 34 that temporarily stores setting information and spare information transferred from the working OLT 10a to the spare OLT 10b at the time of switching.

  The L3 switch 40 includes a network interface 42a connected to the network interface 12a of the OLT 10a, a network interface 42b connected to the network interface 12b of the spare OLT 10b, and a network interface 44 connected to the higher level network. Between the network interfaces 42a and 42b and the network interface 44, a buffer 46 including a down buffer 46a and an up buffer 46b is disposed. Note that the down buffer 46a and the up buffer 46b are shown in order to facilitate understanding of the operation of the present embodiment, and actually there is a buffer for each network interface.

  The CPU 48 controls the entire L3 switch 40. The port mirroring control device 50 built in the CPU 48 controls the port mirroring of the network interfaces 42a and 42b. Details of this port mirroring control will be described later. The CPU 32 of the control device 30 is connected to the CPU 48 via the control port 54.

  Data directed from the upper network to the OLT 10a or its subordinates is supplied from the network interface 44 to the buffer 46 and stored in the downstream buffer 46a according to the destination address. The downlink data stored in the downlink buffer 46a is sequentially read and supplied from the network interface 42a to the working OLT 10a.

  When port mirroring for the network interfaces 42a and 42b by the port mirroring control device 50 is valid, the same data is supplied from the downlink buffer 46a to both network interfaces 42a and 42b.

  The data supplied from the active OLT 10a to the network interface 42a is temporarily stored in the upstream buffer 46b of the buffer 46, and is transmitted from the network interface 44 to the upper network.

  The CPU 48 performs flow control to prevent data from overflowing from the down buffer 46a and the up buffer 46b. Since the contents of the flow control are well known, detailed description is omitted.

  The special frame generation device 52 generates a special frame indicating the start of the switching operation from the active OLT 10a to the spare OLT 10b in accordance with a control signal from the CPU 48. This special frame is used to synchronize the downlink data stored in the downlink buffer 14a of the active OLT 10a and the downlink data stored in the downlink buffer 14b of the backup OLT 10b, and the OLTs 10a and 10b start switching on the downlink data. It is also a delimiter frame to inform to. The special frame may be any bit pattern as long as it can be distinguished from the control signals directed to the CPUs 16a and 16b and the downlink data directed to the subordinate ONUs 68-1 to 69-n. For example, data including data that is not included in a normal frame, for example, data having a transmission source MAC address and / or a destination MAC address of 0: 0: 0: 0: 0: 0. However, from the viewpoint of avoiding unnecessary traffic, the destination is preferably the MAC address of an arbitrary device connected to the ONUs 68-1 to 68-n under the OLT 10a.

  The switching operation from the working OLT 10a to the spare OLT 10b in this embodiment will be described with reference to FIGS. FIG. 2 shows an operation flowchart of the control device 30. FIG. 3 shows an operation flowchart of the OLT 10a. FIG. 4 shows an operation flowchart of the OLT 30b.

  The control device 30 starts the standby OLT 10b in a standby mode in which passive operation is performed, instructs the L3 switch 40 to mirror the downstream data supplied from the higher-level network to the active OLT 10a, and starts the switching process to the active OLT 10a. (S1).

  Here, the working OLT 10a fully uses the downlink buffer 14a, and the control device 30 knows in advance the usage size of the downlink buffer 14a of the working OLT 10a and the size of the downlink buffer 14b of the spare OLT 10b. And When any one is unknown, the control apparatus 30 should just inquire with OLT10a, 10b in the step S1.

  In the standby mode, the spare OLT 10b only transfers the data input from the network interface 12b to the downlink buffer 14b to the CPU 16b for content confirmation, and does not accumulate in the downlink buffer 14b. Similarly, data input from the optical / electrical converter 22b to the upstream buffer 14b is only transferred to the CPU 16b for content confirmation and is not stored in the upstream buffer 24b. The OLT 10b in the standby mode does not perform an active operation for managing the subordinate ONUs, but only operates passively. Unless otherwise permitted, no signal is sent to either the L3 switch 40 or the optical coupler 60. Do not output.

  In the L3 switch 40, the port mirroring control device 50 of the CPU 48 enables port mirroring of the downlink data for the network interface 42a to the network interface 42b. Thereby, the downlink data from the higher level network is supplied to both the working OLT 10a and the spare OLT 10b.

  The control device 30 instructs the active OLT 10a to reduce the use size of the downlink buffer 14a so that the size of the downlink buffer 14b of the backup OLT 10b is larger than a certain margin than the use size of the downlink buffer 14a of the active OLT 10a. (S2). When the working OLT 10a receives an instruction to start the switching process (S21), the working OLT 10a enters the switching mode, and reduces the size of the downlink buffer 14a by a certain margin (S22). In the switching mode, the process of searching for a newly participating ONU is paused.

  The margin secured in the downlink buffer 14b is determined to such an extent that the downlink data amount within the time required for switching from the active OLT 10a to the backup OLT 10b can be accepted. As a result, in this embodiment, it is possible to reduce the possibility of losing downlink data when switching from the working OLT 10a to the backup OLT 10b. Of course, if the buffer size of the downlink buffer 14b of the spare OLT 10b is sufficient to hold the downlink data received during the switching from the active OLT 10a to the spare OLT 10b, such adjustment of the downlink buffer size is unnecessary. .

  After adjusting the downlink buffer size, the working OLT 10a transmits management information and setting information to the control device 30 (S23), and waits for reception of a special frame from the L3 switch 40 (S24). As described above, the management information is made up of information that dynamically changes depending on the situation, and the setting information is made up of invariant information set in advance in the subordinate PON system.

  The control device 30 transfers the management information and setting information from the active OLT 10a to the backup OLT 10b (S3). The spare OLT 10b receives management information and setting information from the control device 30, stores them in the memory 26b (S41), and waits for reception of a special frame from the L3 switch 40 (S42).

  The control device 30 instructs the L3 switch 49 to output the special frame toward the OLT 10a (S4). In accordance with this instruction, the CPU 48 of the L3 switch 40 instructs the special frame generation device 52 to output a special frame. The special frame output from the special frame generation device 52 is added to the tail end of the downlink buffer 46a. Of course, a special frame may be inserted at the forefront of the downstream buffer 46a by interruption. When the special frame is read from the downstream buffer 46a, the special frame is supplied to the active OLT 10a and the spare OLT 10b via the network interfaces 42a and 42b by the port mirroring function.

  The active OLT 10a waits for reception of a special frame while supplying downlink data to the subordinate ONUs 68-1 to 68-n via the downlink buffer 14a (S24). When receiving the special frame (S24), the active OLT 10a stops taking downstream data after the special frame into the downlink buffer 14a (S25). The OLT 10a may turn off the flow control with the L3 switch 40 side and cancel the data captured in the buffer 14a without stopping the capturing of the downstream data into the downstream buffer 14a. By stopping the capture, the downlink buffer 14a only reads the stored data to the electrical / optical converter 18a, and the amount of data stored in the downlink buffer 14a decreases in accordance with the data read.

  Further, the OLT 10a suspends bandwidth allocation to the ONUs 68-1 to 68-n according to instructions from the control device 30 (S26). After this suspension of bandwidth allocation, the ONUs 68-1 to 68-n cannot transmit uplink data.

  On the other hand, when receiving the special frame (S42), the OLT 10b starts taking downstream data following the special frame into the buffer 14b using this as a trigger (S43). Then, it waits for an instruction to start uplink frame reception (S44).

  After step S26, the OLT 10a waits for reception of all upstream data frames from the ONUs 68-1 to 68-n (S27). This is to receive the uplink data transmitted from the ONUs 68-1 to 68-n before the bandwidth allocation suspension (S26). When the all-up data frame is received from the ONUs 68-1 to 68-n (S27), the OLT 10a notifies the control device 30 to that effect (S28).

  When receiving the notification of reception of all uplink frames from the OLT 10a (S6), the control device 30 instructs the OLT 10a to stop reception (capture) of the uplink data frame and instructs the OLT 10b to start reception (capture) of the uplink data frame ( S7). The OLT 10a stops taking upstream data into the upstream buffer 24a in accordance with the upstream frame reception stop instruction from the control device 30 (S29). However, the OLT 10a can receive control data from the ONUs 68-1 to 68-n. The stop of the upstream data capture into the upstream buffer 24a of the OLT 10a substantially includes an operation of not reading the data captured with the upstream data into the upstream buffer 24a to the network interface 12a. This method helps to update the management information, for example the IGMP snooping table, as correctly as possible.

  On the other hand, the OLT 10b starts taking upstream data into the buffer 24b (S45) in accordance with an instruction to start receiving upstream frames from the control device 30 (S44). As a result, the upstream data to be supplied to the upper network thereafter passes through the upstream buffer 24b of the OLT 10b. The OLT 10b waits for reception of management information from the control device 30 (S46).

  The control device 30 instructs the OLT 10a to resume bandwidth allocation to the ONU (S8). At this point, since the downlink data still passes through the ONU 10a, the ONU 10a is in charge of bandwidth allocation. This is because the bandwidth allocation control signal is multiplexed with downlink data and transmitted to the ONUs 68-1 to 68-n. In accordance with this instruction, the OLT 10a resumes bandwidth allocation to the ONUs 68-1 to 68-n (S30). Accordingly, the ONUs 68-1 to 68-n can transmit uplink data.

  When the downlink buffer 14a becomes empty, that is, when all the downlink data before reception of the special frame has been read from the downlink buffer 14a (S31), the OLT 10a notifies the control device 30 to that effect, and the ONUs 68-1 to 68- The bandwidth allocation to n is stopped, and the management information with the contents updated so far is transmitted to the control device 30 (S32).

  The control device 30 waits for a notification from the OLT 10a that the downlink buffer 14a has become empty (S9). Upon receiving this notification (S9) and receiving the management information (S10), the control device 30 instructs the L3 switch 40 to switch the mirroring port between the network interfaces 42a and 42b (S11). In accordance with this instruction, the port mirroring control device 50 of the L3 switch 40 supplies the downlink data read from the downlink buffer 46a to the network interface 42b, supplies the same data to the network interface 42a, and the uplink data from the network interface 42b. Are stored in the upstream buffer 46b, the network interfaces 42a and 42b and the buffer 46 are controlled. At this time, the L3 switch 40 may stop mirroring the downlink data to the interfaces 42a and 42b.

  The control device 30 further transmits management information to the OLT 10b, instructs to shift to normal operation (S12), and shuts down the OLT 10a (S13). When receiving the management information from the control device 30 (S46), the OLT 10b updates the management information in the memory 26b with the received management information (S47). When the OLT 10b receives an instruction to shift to the normal operation from the control device 30 (S48), the OLT 10b shifts to the normal operation (S49). In normal operation, the OLT 10b manages the ONUs 768-1 to 68-n using management information and setting information stored in the memory 26b. Normally, it is necessary to start from the confirmation process of the ONUs 68-1 to 68-n. However, since the management information updated to the latest can be used, the management burden of the OLT 10b is reduced.

  In FIGS. 2 to 4, uplink and downlink are simultaneously switched from the working OLT 10a to the backup OLT 10b. However, the uplink data may be switched from the working OLT 10a to the backup OLT 10b, and then the downlink data may be switched from the working OLT 10a to the backup OLT 10b. Of course, the downlink data may be switched from the working OLT 10a to the backup OLT 10b first, and then the uplink data may be switched from the working OLT 10a to the backup OLT 10b.

  An operation example in which the uplink data is switched from the working OLT 10a to the backup OLT 10b and then the downlink data is switched from the working OLT 10a to the backup OLT 10b will be described. FIG. 5 shows an operation flowchart of the control device 30. FIG. 6 shows an operation flowchart of the OLT 10a. FIG. 7 shows an operation flowchart of the OLT 30b.

  The control device 30 activates the spare OLT 10b in the standby mode, instructs the L3 switch 40 to mirror the downlink data supplied from the higher level network to the active OLT 10a to the spare OLT 10b, and instructs the active OLT 10a to start the switching process. (S101).

  As in the previous operation, the working OLT 10a uses the downstream buffer 14a fully, and the control device 30 knows in advance the size of the downstream buffer 14a in the working OLT 10a and the size of the downstream buffer 14b in the backup OLT 10b. It shall be. When any one is unknown, the control apparatus 30 should just inquire with OLT10a, 10b in the step S1.

  In the standby mode, the spare OLT 10b only transfers the data input from the network interface 12b to the downlink buffer 14b to the CPU 16b for content confirmation, and does not accumulate in the downlink buffer 14b. Similarly, data input from the optical / electrical converter 22b to the upstream buffer 14b is only transferred to the CPU 16b for content confirmation and is not stored in the upstream buffer 24b.

  In the L3 switch 40, the port mirroring control device 50 of the CPU 48 enables port mirroring of the downlink data for the network interface 42a to the network interface 42b. Thereby, the downlink data from the higher level network is supplied to both the working OLT 10a and the spare OLT 10b.

  The control device 30 instructs the active OLT 10a to reduce the use size of the downlink buffer 14a so that the size of the downlink buffer 14b of the backup OLT 10b is larger than a certain margin than the use size of the downlink buffer 14a of the active OLT 10a. (S102). When receiving the instruction to start the switching process (S121), the active OLT 10a enters the switching mode and reduces the size of the downlink buffer 14a by a certain margin (S122). In the switching mode, the process of searching for a newly participating ONU is paused.

  The margin secured in the downlink buffer 14b is determined to such an extent that the downlink data amount within the time required for switching from the active OLT 10a to the backup OLT 10b can be accepted. As a result, in this embodiment, it is possible to reduce the possibility of losing downlink data when switching from the working OLT 10a to the backup OLT 10b. Of course, if the buffer size of the downlink buffer 14b of the spare OLT 10b is sufficient to hold the downlink data received during the switching from the active OLT 10a to the spare OLT 10b, such adjustment of the downlink buffer size is unnecessary. .

  After adjusting the downlink buffer size, the active OLT 10a transmits management information and setting information to the control device 30 (S123). The control device 30 transfers the management information and setting information from the active OLT 10a to the backup OLT 10b (S103). The spare OLT 10b receives management information and setting information from the control device 30, and stores them in the memory 26b (S141).

  First, the upstream system is switched from the active OLT 10a to the spare OLT 10b. For this purpose, the control device 30 instructs the active OLT 10a to stop allocating bandwidth to the ONUs 68-1 to 68-n (S104), and waits for notification of reception of all uplink frames from the O + T 10a (S105). The OLT 10a suspends bandwidth allocation to the ONUs 68-1 to 68-n according to this instruction from the control device 30 (S124). After this suspension of bandwidth allocation, the ONUs 68-1 to 68-n cannot transmit uplink data.

  After S124, the OLT 10a waits for reception of all upstream frames from the ONUs 68-1 to 68-n (S125). This is because the upstream data transmitted by the ONUs 68-1 to 68-n is received before the bandwidth allocation suspension (S124). When all the upstream frames are received from the ONUs 68-1 to 68-n (S125), the OLT 10a notifies the control device 30 to that effect (S126).

  When receiving the notification of reception of all uplink frames from the OLT 10a (S105), the control device 30 instructs the OLT 10a to stop reception (capture) of the uplink data frame and instructs the OLT 10b to start reception (capture) of the uplink data frame ( S106). The OLT 10a stops taking upstream data into the upstream buffer 24a in accordance with the upstream data frame reception stop instruction from the control device 30 (S127). However, the OLT 10a can receive control data from the ONUs 68-1 to 68-n. Stopping the capture of the upstream data frame into the upstream buffer 24a of the OLT 10a substantially includes an operation of not reading the data captured with the upstream data into the upstream buffer 24a to the network interface 12a. This method helps to update the management information, for example the IGMP snooping table, as correctly as possible.

  On the other hand, the OLT 10b starts taking upstream data into the buffer 24b in accordance with an instruction to start receiving upstream frames from the control device 30 (S142) (S143). As a result, the upstream data to be supplied to the upper network thereafter passes through the upstream buffer 24b of the OLT 10b. The OLT 10b manages the data in the upstream buffer 24b using the management information and the setting information received in step S141.

  The control device 30 instructs the OLT 10a to resume bandwidth allocation to the ONUs 68-1 to 68-n (S107). At this point, since the downlink data still passes through the ONU 10a, the ONU 10a is in charge of bandwidth allocation. This is because the bandwidth allocation control signal is multiplexed with downlink data and transmitted to the ONUs 68-1 to 68-n. In accordance with this instruction, the OLT 10a resumes bandwidth allocation to the ONUs 68-1 to 68-n (S128). Accordingly, the ONUs 68-1 to 68-n can transmit uplink data.

  The control device 30 instructs the L3 switch 49 to output the special frame toward the OLT 10a (S108). In accordance with this instruction, the CPU 48 of the L3 switch 40 instructs the special frame generation device 52 to output a special frame. The special frame output from the special frame generation device 52 is added to the tail end of the downlink buffer 46a. Of course, a special frame may be inserted at the forefront of the downstream buffer 46a by interruption. When the special frame is read from the downstream buffer 46a, the special frame is supplied to the active OLT 10a and the spare OLT 10b via the network interfaces 42a and 42b by the port mirroring function.

  The active OLT 10a waits for reception of a special frame while supplying downlink data to the subordinate ONUs 68-1 to 68-n via the downlink buffer 14a (S129). When the active OLT 10a receives a special frame from the L3 switch 40 (S129), the working OLT 10a stops taking downstream data after the special frame into the downlink buffer 14a (S130). The OLT 10a may turn off the flow control with the L3 switch 40 side and cancel the data captured in the buffer 14a without stopping the capturing of the downstream data into the downstream buffer 14a. By stopping the capture, the downlink buffer 14a only reads the stored data to the electrical / optical converter 18a, and the amount of data stored in the downlink buffer 14a decreases in accordance with the data read.

  When the downlink buffer 14a is emptied, that is, when all the downlink data before reception of the special frame has been read from the buffer 14a (S131), the OLT 10a notifies the control device 30 to that effect and sends to the ONUs 68-1 to 68-n. And the management information of the contents updated so far are transmitted to the control device 30 (S132).

  On the other hand, the OLT 10b also waits for reception of a special frame from the L3 switch 40 (S144). When receiving the special frame (S144), the OLT 10b starts taking downstream data following the special frame into the buffer 14b using this as a trigger (S145). Then, it waits for reception of management information (S146).

  The control device 30 waits for a notification from the OLT 10a that the downlink buffer 14a has become empty (S109). Upon receiving this notification (S109) and receiving management information (S110), the control device 30 instructs the L3 switch 40 to switch the mirroring port between the network interfaces 42a and 42b (S111). In accordance with this instruction, the port mirroring control device 50 of the L3 switch 40 supplies the downlink data read from the downlink buffer 46a to the network interface 42b, supplies the same data to the network interface 42a, and the uplink data from the network interface 42b. Are stored in the upstream buffer 46b, the network interfaces 42a and 42b and the buffer 46 are controlled. At this time, the L3 switch 40 may stop mirroring the downlink data to the interfaces 42a and 42b.

  The control device 30 further transmits management information to the OLT 10b, instructs to shift to normal operation (S112), and shuts down the OLT 10a (S113). When receiving the management information from the control device 30 (S146), the OLT 10b updates the management information in the memory 26b with the received management information (S147). Further, when the OLT 10b receives an instruction to shift to the normal operation from the control device 30 (S148), the OLT 10b shifts to the normal operation (S149). In a normal operation, the OLT 10b manages the ONUs 768-1 to 68-n using management information and setting information stored in the memory 26b. Normally, it is necessary to start from the confirmation process of the ONUs 68-1 to 68-n. However, since the management information updated to the latest can be used, the management burden of the OLT 10b is reduced.

  The active OLT 10a and the spare OLT 10b do not have to have the same performance. For example, when the OLT 10a corresponds to 1 Gbps, the OLT 10b may correspond to a higher speed, for example, 2 Gbps. The present invention is generally applicable not only when the active device is switched to a backup device as a backup, but also when the active device is switched to another device.

  In the above embodiment, the special frame generation device 52 is arranged in the L3 switch 40. However, as shown in FIG. 8, the control device 30a is connected to the L3 switch 40a via the network interfaces 36 and 42c. , 42c, the control device 30a may transmit to the L3 switch 40a a special frame addressed to the OLT 10a or the ONUs 68-1 to 69-n subordinate thereto. FIG. 8 shows a schematic block diagram of an embodiment modified in such a manner.

  The CPU 32a outputs a special frame to the network interface 36. The special frame enters the buffer 46 via the network interfaces 36 and 42c, and is supplied from the downstream buffer 46a to the OLTs 10a and 10b via the network interfaces 42a and 42b by port mirroring. By designating the OLT 10a or the subordinate ONUs 68-1 to 69-n and the like as the destination of the special frame, the special frame input from the control device 30a to the network interface 42c is transferred to the network interfaces 42a and 42b.

  Although the invention has been described with reference to specific illustrative embodiments, various modifications and alterations may be made to the above-described embodiments without departing from the scope of the invention as defined in the claims. This is obvious to an engineer in the field to which the present invention belongs, and such changes and modifications are also included in the technical scope of the present invention.

1 shows a schematic block diagram of an embodiment of the present invention. It is an operation | movement flowchart of the control apparatus 30 in a 1st operation example. It is an operation | movement flowchart of OLT10a in a 1st operation example. It is an operation | movement flowchart of OLT30b in a 1st operation example. It is an operation | movement flowchart of the control apparatus 30 in a 2nd operation example. It is an operation | movement flowchart of OLT10a in a 2nd operation example. It is an operation | movement flowchart of OLT30b in a 2nd operation example. The schematic block diagram of a modified embodiment of the present invention is shown.

Explanation of symbols

10a: Working optical termination device (OLT)
10b: Backup optical termination device (OLT)
12a, 12b: Network interfaces 14a, 14b: Downstream buffers 16a, 16b: CPU
18a, 18b: electrical / optical converters 20a, 20b: wavelength division multiplexing (WDM) optical couplers 22a, 22b: optical / electrical converters 24a, 24b: upstream buffers 26a, 26b: memories 30, 30a: control device 32: CPU
34: Memory 36: Network interface 40, 40a: L3 switches 42a, 42b, 42c, 44: Network interface 46: Buffer 46a: Down buffer 46b: Up buffer 48: CPU
50: Port mirroring controller 52: Special frame generator 60: 2: 1 optical coupler 62: Optical fiber 64: Optical couplers 66-1 to 66-n: Optical fibers 68-1 to 68-n: Optical terminator ( ONU)

Claims (5)

In an optical network in which a plurality of user optical termination devices are connected to an optical termination device of a center station via an optical transmission line, the optical termination device of the center station is switched from a working OLT to a standby OLT,
A switch (40) having a function of port mirroring of data to the working OLT and the spare OLT is prepared upstream of the working OLT (10a) and the spare OLT (10b).
Downstream signals from the working OLT (10a) and the spare OLT (10b) to the optical transmission lines (62, 64, 66-1 to n) are provided downstream of the working OLT (10a) and the spare OLT (10b). An optical coupler (60) for supplying light and supplying upstream signal light from the optical transmission line (62, 64, 66-1 to n) to the working OLT and the backup OLT is prepared.
A control device (30) for controlling switching from the current OLT (10a) to the spare OLT (10b) is prepared,
An activation step of activating the standby OLT in a standby mode for passive operation and enabling port mirroring of the switch (40) to the active OLT (10a) and the standby OLT (10b);
A management / setting information transfer step of transferring management information and setting information of the active OLT (10a) to the backup OLT (10b);
A downlink switching step for switching the downlink data path from the active OLT (10a) to the backup OLT (10b);
An uplink switching step for switching the path of the uplink data from the active OLT (10a) to the backup OLT (10b);
A method of switching an optical terminal device, comprising: a complete transition step of completely transitioning from a working OLT (10a) to a standby OLT (10b). The complete transition step is
An update step of updating the management information of the spare OLT (10b) with the management information of the active OLT (10a);
2. The optical terminal switching method according to claim 1, further comprising: a normal operation instruction step for instructing the normal operation of the spare OLT (10b). The downlink switching step is
Supplying a predetermined frame from the switch to both the working OLT (10a) and the spare OLT (10b);
In response to reception of the predetermined frame, the working OLT (10a) stops capturing subsequent downstream data of the predetermined frame;
In response to receiving the predetermined frame, the spare OLT (10b) starts capturing downstream data subsequent to the predetermined frame;
3. The optical terminal switching method according to claim 1, further comprising a step of notifying the control device that the working OLT (10a) has no remaining downlink data. The uplink switching step is
Suspending bandwidth allocation to the user optical termination device by the working OLT (10a);
In response to reception of all uplink data before suspension of bandwidth allocation by the current OLT (10a), the reception of the uplink data of the current OLT (10a) is stopped and the uplink data of the backup OLT (10b) A step of starting reception;
The method for switching an optical terminal device according to any one of claims 1 to 3, further comprising a step of resuming bandwidth allocation to the user optical terminal device by the working OLT (10a).   Furthermore, before executing the downlink switching step, a step of reducing the size of the downlink data buffer of the active OLT (10a) by a predetermined amount from the downlink data buffer of the backup OLT (10b) is provided. The optical termination device switching method according to claim 1, wherein the optical termination device is switched.

Images