JP6988272B2 - Station side terminal device and route switching method - Google Patents

Description

The present invention is a station-side termination device capable of dynamically switching the connection with the subscriber-side termination device dynamically and without interruption, and route switching for switching the connection between the subscriber-side termination device and the station-side termination device without interruption. Regarding the method.

In recent years, a service called FTTH (Fiber To The Home) using an optical fiber for a transmission line has become widespread for the purpose of providing a high-speed and wide-band broadband service to general private homes. For the provision of broadband services by FTTH, an optical access network called a passive optical subscriber network (PON) is often used.

The PON uses an optical passive element called an optical splitter (optical coupler) to combine one station-side terminal unit (OLT: Optical Line Terminal) and a plurality of subscriber-side terminal units (ONU: Optical Network Unit). It is configured by connecting one-to-many by branching the optical cable of the book. In PON, the FTTH service can be economically provided by sharing an optical fiber, an OLT, or the like with a plurality of subscribers.

Some PONs are called 10G-EPON (10 Gigabit Ethernet® PON) (see, for example, Non-Patent Document 1). In the PON described in Non-Patent Document 1, TDMA (Time Division Multiple Access) technology is used for communication (upstream communication) from the ONU to the OLT, and collision of signals from each ONU is avoided. .. PON using this TDMA technology is also called TDM-PON.

Furthermore, in order to meet the increasing communication demand in future optical access networks, multiple TDM-PONs will be integrated into one PON infrastructure (PON infrastructure) using WDM (Wavelength Division Multiplexing) technology as a next-generation PON with a transmission rate exceeding 10 Gbps. ), And research and development on WDM / TDM-PON (TWDM-PON) constructed on the above is progressing (see, for example, Patent Document 1). By using TWDM-PON, the transmission capacity in the PON infrastructure can be increased.

FIG. 6 shows an outline of TWDM-PON disclosed in Patent Document 1. As shown in FIG. 6, TWDM-PON1 includes OLT2 and a plurality of ONU6-1 to ONU6-m (m is an integer of 2 or more). The OLT 2 includes a control device 3 for controlling TWDM-PON 1, a plurality of OSUs (Optical Subscriber Units) 4 (4-1 to 4-n: n is an integer of 2 or more), and a plurality of OSUs 4 connected to each of the control devices 3. It is configured to include an optical transmitter / receiver 5 (5-1 to 5-n). Each optical transmitter / receiver 5 is connected to a plurality of ONUs 6 via an optical splitter 7.

Regarding uplink communication, the reception wavelengths of the optical transmitters / receivers 5 of the OLT 2 are fixedly assigned so that the reception wavelengths of the optical transmitters / receivers 5 of the OLT 2 do not overlap. In this case, the connection between each optical transmitter / receiver 5 of the OLT 2 and the ONU 6 can be dynamically switched by changing the transmission wavelength of the optical transmitter / receiver (not shown) of the ONU 6. As for the communication from the OLT 2 to the ONU 6 (downlink communication), the transmission wavelength of each optical transmitter / receiver 5 of the OLT 2 is fixedly assigned and the reception wavelength of the optical transmitter / receiver of the ONU 6 is changed to change the reception wavelength of the OLT 2 as in the uplink communication. The connection between each optical transmitter / receiver 5 and the ONU 6 can be dynamically switched. For this reason, TWDM-PON1 not only widens the bandwidth, but also distributes the load according to traffic fluctuations, improves reliability by switching routes in the event of a failure, and saves power by sleeping the optical transmitter / receiver and device circuit at the time of low load. There are advantages of.

Here, in the TWDM-PON1, for example, when dynamically switching the connection between the OLT 2 and the ONU 6 regarding downlink communication, the optical transmitter / receiver 5 of the OLT 2 is switched and the reception wavelength of the ONU 6 is switched. During the switching time until the reception wavelength of the ONU 6 is switched from the wavelength before the switching to the wavelength after the switching, the ONU 6 cannot receive the downlink communication packet (hereinafter, also simply referred to as “downlink packet”). However, in multimedia applications and the like, it is desirable that packet loss does not occur during the switching time in terms of service quality, and switching processing without interruption is required.

Therefore, in order to avoid packet loss of downlink communication during the switching time, it is necessary to buffer the packet addressed to the ONU 6 to be switched by the OLT 2 during the switching time. As a means of switching the communication route while buffering the input packet, a technique has been proposed in which a buffer is provided in front of the switch for switching the route and the route is switched by the switch according to the destination of the input packet (). For example, see Patent Document 2).

Japanese Unexamined Patent Publication No. 2011-055407 Japanese Unexamined Patent Publication No. 10-229404

IEEE (Institute of Electrical and Electronics Engineers) std 802.3av-2009

Here, in the TWDM-PON, the OLT identifies the downlink packet in the ONU unit, and distributes the packet to the optical transmitter / receiver of the OSU to which the transmission wavelength corresponding to the reception wavelength of the ONU at that time is assigned.

When the configuration disclosed in Patent Document 2 described above is applied in order to perform path switching in TWDM-PON without interruption, the buffers in the pre-switch stage are mounted for the number of ONUs accommodated in TWDM-PON. There is a need to. Therefore, when the number of ONUs accommodated is large, the circuit scale increases. Further, since each buffer needs a capacity that can hold packets for the switching time, a large buffer amount is required when the switching time is long. Increasing the circuit scale and the amount of buffers poses a problem in terms of device feasibility.

Further, if a shared buffer method in which a buffer is shared is applied in order to save the buffer amount, the address management information increases as the number of ONUs accommodated increases. Therefore, when the number of ONUs to be accommodated is large, a large memory is required for address management, which poses a problem in terms of device feasibility.

On the other hand, not only in TWDM-PON but also in a communication system having a route switching function, it may be necessary to stop the route switching process once started due to a system failure or the like. When the route switching process is stopped, it is necessary to return to the state of the device before switching, but it is preferable that this return process is also performed without interruption. Neither of the above patent documents discloses a specific method for performing such a route switching stop process without interruption.

The present invention has been made in view of the above-mentioned problems. An object of the present invention is a station-side termination device capable of dynamically changing the connection with the subscriber-side termination device without causing packet loss even when the number of subscriber-side termination devices accommodated is large. It is an object of the present invention to provide a route switching method for changing the connection between the subscriber-side termination device and the station-side termination device without increasing the circuit scale. Further, an object of the present invention is that even if it becomes necessary to stop the wavelength switching operation for some reason during the wavelength switching operation, the station can be restored to the state before the switching without causing packet loss. The purpose is to provide a side termination device and a route switching method.

In order to achieve the above-mentioned object, the station-side termination device according to the present invention sends one or a plurality of switching buffers and a packet addressed to the subscriber-side termination device to be switched to the switching buffer. A plurality of termination devices each having a division and connected to one or more subscriber-side termination devices via a route by a transmission path, and a received packet are registered by the subscriber-side termination device to the destination of the packet. When the route is switched, the terminal device distribution unit includes the terminal device distribution unit that sends the packet to the terminal device, and the terminal device distribution unit switches the packet addressed to the subscriber side terminal device to be switched. The subscriber-side termination device distribution unit of each of the termination device of the switching source and the termination device of the switching destination sends a packet addressed to the subscriber-side termination device to be switched to the switching buffer. It is sent to.

In order to achieve the above-mentioned object, the route switching method according to the present invention comprises one or a plurality of switching buffers and a subscriber-side termination device distribution for sending a packet addressed to the subscriber-side termination device to be switched to the switching buffer. It is a route switching method by a station-side termination device including a plurality of termination devices, each of which is provided with a unit and is connected to one or a plurality of subscriber-side termination devices via a path by a transmission path, and the switching of the path occurs. In this case, the subscriber-side termination device distribution unit of each of the switching source termination device and the switching destination termination device sends a packet addressed to the subscriber-side termination device to be switched to the switching buffer, and the route switching is performed. If it is performed normally, the switching source terminating device discards the packet stored in the switching buffer, and the switching destination terminating device sends the packet stored in the switching buffer to the switching target subscriber side terminating device. By sending it, the route is switched without interruption.

According to the station-side termination device and the route switching method according to the present invention, even if the number of subscriber-side termination devices accommodated is large, the connection with the subscriber-side termination device without causing packet loss. It is possible to provide a station-side termination device that can dynamically change the frequency and a route switching method without increasing the circuit scale. Further, according to the station-side termination device and the route switching method according to the present invention, even if it becomes necessary to stop the route switching operation for some reason during the wavelength switching operation, before switching without causing packet loss. It is possible to recover to the state of.

It is a main part block diagram of TWDM-PON for demonstrating the route switching method which concerns on this embodiment. It is a schematic diagram for demonstrating the route switching method which concerns on 1st Embodiment. It is a sequence diagram for demonstrating the route switching method which concerns on 1st Embodiment. It is a schematic diagram for demonstrating the route switching method which concerns on 2nd Embodiment. It is a sequence diagram for demonstrating the route switching method which concerns on 2nd Embodiment. It is a block diagram for demonstrating TWDM-PON which concerns on a prior art.

Hereinafter, embodiments of the present invention will be described with reference to the drawings, but the respective figures are merely schematic to the extent that the present invention can be understood. Further, although a suitable configuration example of the present invention will be described below, numerical conditions and the like are merely suitable examples. Therefore, the present invention is not limited to the following embodiments, and many modifications or modifications can be made to achieve the effects of the present invention without departing from the scope of the configuration of the present invention.

A configuration example of a TWDM-PON including an OLT according to the present embodiment will be described with reference to FIG. 1. FIG. 1 is a configuration diagram of a main part of TWDM-PON for explaining a route switching method according to the present embodiment described later.

TWDM-PON is an optical access network using a PON system. In the TWDM-PON (optical communication system), a downlink signal from the OLT (optical network unit) to the ONU (subscriber-side termination device) and an uplink signal from the ONU to the OLT are transmitted and received. Further, the uplink signal and the downlink signal are data signals transmitted and received between the upper network connected to the OLT (not shown) and the user terminal or the like connected to the ONU (not shown). And there are control signals used to establish the PON link. Here, the data signal (downlink packet) included in the downlink signal will be described, and the description of the control signal included in the uplink signal and the downlink signal may be omitted.

The TWDM-PON 10 includes one OLT 100, a plurality of ONU300-1 to m (m is an integer of 2 or more, generically referred to as "ONU300"), and an optical splitter 400 which is an optical passive element. An optical fiber is connected between the OLT 100 and the optical splitter 400, and between the ONU 300-1 to m and the optical splitter 400, respectively.

The OLT 100 includes an LLID identification unit 110, an OSU distribution unit (termination device distribution unit) 120, and a plurality of OSUs (termination devices) 200-1 to n (n is an integer of 2 or more, collectively referred to as "OSU200"). It is configured to include a plurality of optical transmitters 130-1 to n (collectively referred to as "optical transmitter 130") and an OLT control unit (station-side termination device control unit) 140.

The LLID identification unit 110 is connected to the OSU distribution unit 120. The LLID identification unit 110 identifies the destination ONU 300 based on the identification information of the downlink packet input from the upper network. As the identification information of the downlink packet, for example, a VLAN ID (Virtual Local Area Identifier: VID) included in the packet (frame) of Ethernet (registered trademark) can be used. The LLID identification unit 110 has an LLID identification table 112 that associates a VID with a logical link identifier (LLID: Logical Link ID). Basically, the LLID is assigned one-to-one to the connected ONU300. Therefore, the LLID identification unit 110 can identify the destination ONU 300 from the VID of the downlink packet by using the LLID identification table 112. The LLID identification unit 110 adds the LLID assigned to the destination ONU 300 to the downlink packet and sends it to the OSU distribution unit 120.

The OSU distribution unit 120 is connected to a plurality of OSUs 200-1 to n. In TWDM-PON10, each ONU300-1 to m is registered in any of a plurality of OSU200-1 to n. The OSU distribution unit 120 has an LLID allocation table 122 that associates the LLID with the OSU 200. The OSU distribution unit 120 uses the LLID allocation table 122 to identify the OSU 200 in which the destination ONU 300 is registered from the LLID of the received downlink packet. In the LLID allocation table 122 according to the present embodiment, each OSU200 is registered for each LLID using two parameters, the switching source OSU200 and the switching destination OSU200, in order to be used in the route switching described later. The OSU distribution unit 120 sends a downlink packet to the identified OSU 200.

The OSU200-1 to n are connected one-to-one with the optical transmitters 130-1 to n. Further, different wavelengths (λ1 to λn) are fixedly assigned to the optical transmitters 130-1 to n. The optical transmitters 130-1 to n are connected to the ONU 300-1 to m via an optical splitter 400.

The downlink packet input to the OSU 200 is sent to the destination ONU 300 at the wavelength assigned to the optical transmitter 130 via the connected optical transmitter 130. Here, since the OSU200-1 to n are connected to the optical transmitters 130-1 to n on a one-to-one basis, the transmission wavelength of the downlink packet is determined by the OSU200 in which the destination ONU300 is registered. Therefore, in the following description, the wavelength assigned to the optical transmitters 130-1 to n connected to a certain OSU200-1 to n may be expressed as the wavelength assigned to the OSU200-1 to n.

Each OSU200-1 to n includes an ONU distribution unit (subscriber side termination device distribution unit) 210, a buffer unit 220, a scheduler unit 250, and a control signal generation unit 260, respectively. The buffer unit 220 includes one through queue 222 and one or more switching queues 224-1 to k (k is an integer of 1 or more) in parallel. The number k of the switching queue 224 corresponds to the number of route switching that can be performed at the same time. Therefore, it is preferable to provide a plurality of switching queues 224. On the other hand, if the number k of the switching queue 224 increases, the circuit scale will increase. Therefore, it is preferable to reduce the number k of the switching queue 224 to be smaller than the number of ONUs 300 that can be registered in each OSU200 to suppress an increase in the circuit scale. The switching queue 224 corresponds to the "switching buffer" according to the present invention.

When the ONU 300, which is the destination of the packet, is the non-switching target, the ONU distribution unit 210 sends the packet to the through queue 222. Further, when the ONU 300, which is the destination of the packet, is the switching target, the ONU distribution unit 210 sends the packet to any of the switching queues 224-1 to k. Which of the plurality of switching queues the ONU distribution unit 210 sends the packet addressed to the ONU 300 to be switched is determined with reference to the learning table 212. The learning table 212 according to the present embodiment has a function of temporarily storing the ONU 300 to be switched. In the following, when a certain ONU 300 is a switching target in the learning table 212, it may be expressed as “learned”, and when it is not a switching target, it may be expressed as “unlearned”.

When the ONU 300 to be switched has not been learned, that is, when the ONU 300 to be switched is not registered in the learning table 212, the ONU distribution unit 210 sends the ONU 300 to any of the unused switching queues 224. At this time, the ONU distribution unit 210 registers the switching queue 224 to which the packet has been sent in the learning table 212, and considers that the learning has been completed. When the ONU 300 to be switched has already been learned, the ONU distribution unit 210 sends a packet to the switching queue 224 registered in the learning table 212.

The control signal generation unit 260 generates a control signal such as a gate packet used to establish a PON link. The ONU 300 can be instructed to switch the reception wavelength by using this control signal.

The through queue 222 and the plurality of switching queues 224-1 to k issue a transmission request to the scheduler unit 250 when a packet is input. The scheduler unit 250 adjusts the output in response to a downlink packet transmission request from each of the queues 222 and 224-1 to k and a control signal transmission request from the control signal generation unit 260, and the optical transmitters 130-1 to 130-1 to A downlink signal is sent to each ONU 300 via n.

The OLT control unit 140 controls the entire OLT 100 and the OSU 200 mounted on the OLT 100. For example, the OLT control unit 140 rewrites the LLID identification table 112 and the LLID allocation table 122. In addition, the traffic passing through the OLT 100 is monitored, and the timing and contents of the route switching are determined. It also monitors the reading from the scheduler unit 250 of each OSU 200.

Further, when the OLT control unit 140 changes the OSU200 of the registration destination of the ONU300 to be switched, the ONU300 to be switched from the OSU200 of the switching source, registered to the OSU200 of the switching destination, and the OSU200 of the switching destination. Notify. Regarding this notification, the OLT control unit 140 may directly instruct the OSU 200, or may be added to the packet sent to each OSU 200 and sent.

The ONU 300 includes an optical receiver 330 for receiving downlink packets. The reception wavelength of the optical receiver 330 is variable, and is set so that downlink packets having a wavelength assigned to the registered OSU 200 can be received.

Configurations other than those described above can be configured in the same manner as known TWDM-PON.

Next, a route switching method according to the present embodiment will be described with reference to FIGS. 2 and 3.
FIG. 2 is a schematic diagram for explaining a route switching method, and FIG. 3 is a sequence diagram in which downlink packets sent from an upper network via SNI (Server Name Interface) are received by each ONU 300. be. Here, the LLID of ONU300-1 is 10, the LLID of ONU300-2 is 20, and the LLID of ONU300-3 is 30. That is, in the LLID identification table 112, ONU = 1 is assigned to LLID = 10, LLID = 20, ONU = 2, and ONU = 3 is assigned to LLID = 30. In FIG. 3, OSU200-1 is referred to as "OSU1", OSU200-2 is referred to as "OSU2", ONU300-1 is referred to as "ONU1", ONU300-2 is referred to as "ONU2", and ONU300-3 is referred to as "ONU3". It is written. Further, among the input packets from SNI shown in FIG. 3, X indicates a packet destined for ONU1, Y indicates ONU2, and Z indicates a packet destined for ONU3. Further, the appendices "I" to "VI" shown in FIGS. 2 and 3 each represent a time.

At time I, ONU300-1 is registered in OSU200-1, ONU300-2 is registered in OSU200-1, and ONU300-3 is registered in OSU200-2. That is, in the LLID allocation table 122, the switching source OSU (hereinafter, “source OSU”) = 1, the switching destination OSU (hereinafter, “destination OSU”) = 1, LLID = 20, and the source OSU = 1 at LLID = 10. , The original OSU = 2 and the original OSU = 2 are assigned to the destination OSU = 1 and LLID = 30.
Therefore, the OSU distribution unit 120 sends the packet Xi (i = 0, 1, ...) To the ONU300-1 to the OSU200-1, and the packet Yj (j = 0, 1, ...) To the ONU300-2. ) Is sent to OSU200-1, and the packet Zk (k = 0, 1, ...) Addressed to ONU300-3 is sent to OSU200-2. Here, it is assumed that the transmission wavelength of OSU200-1 is set to λ1 and the transmission wavelength of OSU200-2 is set to λ2.

The packet Xi is sent to the ONU300-1 via the through queue 222 of the OSU200-1, the scheduler unit 250, and the optical transmitter 130-1 with the LLID identifier = 10 as a downlink signal of the wavelength λ1. The packet Yj passes through the through queue 222 of the OSU200-1, the scheduler unit 250, and the optical transmitter 130-1, and is sent to the ONU300-2 with the LLID identifier = 20 as a downlink signal of the wavelength λ1. The packet Zk passes through the through queue 222 of the OSU200-2, the scheduler unit 250, and the optical transmitter 130-2, and is sent to the ONU300-3 with the LLID identifier = 30 as a downlink signal having a wavelength of λ2.

Here, consider a case where the registration destination (accommodation destination) of ONU300-1 is switched from OSU200-1 to OSU200-2. This switching is performed based on the instruction of the OLT control unit 140, for example, for the purpose of distributing the communication load.

At time II, the OLT control unit 140 rewrites the LLID allocation table 122 and allocates the original OSU = 1 and the destination OSU = 2 to LLID = 10 (see time II in FIG. 2). After the LLID allocation table 122 is rewritten in this way, the packet addressed to ONU300-1 sent from the upper network to the OLT100 is sent to both OSU200-1 and OSU200-2.

However, at this point, since the reception wavelength of ONU300-1 is λ1, the downlink signal of wavelength λ2 from OSU200-2 cannot be received. Therefore, the OSU200-1 needs to instruct the ONU300-1 to switch the reception wavelength to λ2. However, there is a possibility that packets addressed to ONU300-1 are stored in OSU200-1 in an untransmitted state. In addition, it may take time to switch the reception wavelength on the ONU300-1.

Therefore, in consideration of the time required for wavelength switching of ONU300-1 and the time until the packets addressed to ONU300-1 stored in OSU200-1 disappear, the wavelength of ONU300-1 is switched in addition to the wavelength switching. It is better to give instructions at the same timing. The instruction is given by transmitting the XS packet shown in FIG. 3 to ONU300-1, and the switching wavelength and switching timing are notified to ONU300-1. The XS packet is transmitted from the control signal generation unit 260 of the OSU200-1.

After time II, when the OSU200-1 and the OSU200-2 receive the packet addressed to the ONU300-1, they determine whether or not the ONU300-1 is the ONU300 to be switched. At time II, when the LLID allocation table 122 is rewritten, the OLT control unit 140 notifies OSU200-1 and OSU200-2 that the ONU300-1 is the ONU300 to be switched. The ONU distribution unit 210 of each of the OSU200-1 and the OSU200-2 recognizes that the ONU300-1 is the ONU300 to be switched by this notification.

Subsequently, at time III, each ONU distribution unit 210 of OSU200-1 and OSU200-2 determines whether ONU300-1 has been learned or has not been learned in the learning table 212. Here, since ONU300-1 is not registered, it is determined that ONU300-1 has not been learned. The ONU distribution unit 210 sends an unlearned packet addressed to the ONU 300 to one of the unused switching queues, and causes the learning table to learn the switching queue. Here, the switching queue 224-1 is selected as the unused switching queue. The switching queue may be selected by selecting an unused switching queue, in ascending order of numbers, or randomly.

After the switching queue 224-1 is selected, the packet addressed to ONU300-1 is sent to the switching queue 224-1, and 10 in the LLID column of each learning table 212 of OSU200-1 and OSU200-2, the queue column. 1 is registered in (see time III in FIG. 2). As a result, ONU300-1 has been learned. After the ONU300-1 has been learned, the ONU distribution unit 210 of each of the OSU200-1 and the OSU200-2 switches the packet addressed to the ONU300-1 in the switching queue 224-1 by referring to the learning table 212. Send to.

Next, at time IV, ONU300-1 executes wavelength switching for switching the reception wavelength from λ1 to λ2. By this time IV, the wavelength switching timing is adjusted so that the packets addressed to the ONU 300 accumulated in the OSU 200 disappear. After the switching of the reception wavelength is completed in the ONU300-1, a control signal such as a gate signal is sent from the OSU200-2 to the ONU300-1, and when the OSU200-2 receives a response from the ONU300-1, the wavelength switching is completed. ..

After that, at time V, the OLT control unit 140 rewrites the LLID allocation table 122, and allocates the source OSU = 2 and the destination OSU = 2 to LLID = 10 (see time V in FIG. 2). The packet addressed to ONU300-1 sent from the upper network to the OLT100 after rewriting the LLID allocation table 122 is sent to the OSU200-2. At the same time, the scheduler unit 250 of the OSU200-2 transmits the packet stored in the switching queue 224-1 to the ONU300-1. Further, the OSU200-1 clears (discards) the packets stored in the switching queue 224-1 and releases the learning entry. The learning entry is released by deleting the ONU300-1 and the switching queue 224-1 from the learning table 212. Further, OSU200-1 targets ONU300-1 for non-switching.

At time VI, the packets stored in the switching queue 224-1 of OSU200-2 disappear, and the learning entry is released. The learning entry is released by deleting the ONU300-1 and the switching queue 224-1 from the learning table 212. Further, OSU200-2 targets ONU300-1 for non-switching. After the learning entry is released and the ONU300-1 becomes the non-switchable target, the packet addressed to the ONU300-1 is sent to the optical transmitter 130-2 via the through queue 222 of the OSU200-2 and the scheduler unit 250.

Even when the registration destination of ONU300-2 is changed from OSU200-1 to OSU200-2 while the route of ONU300-1 is being switched, the route can be switched by the above process. In this case, since the switching queue 224-1 has been used, for example, the switching queue 224-2 is used as an unused switching queue. The OLT control unit 140 monitors the progress of route switching, and limits the number of ONUs 300 that simultaneously perform wavelength switching to the number of switching queues or less.

According to the OLT (station-side optical network unit) and the route switching method of the present invention, the number of ONUs 300 that perform switching processing at the same time is limited, and the switching queue for holding the packet during switching processing is increased from the number of ONUs accommodated. Can be reduced. In addition, since the number of queues is reduced, the amount of memory required for buffer address management can be reduced. This makes it possible to economically provide an OLT and a route switching method capable of non-instantaneous switching.

[Second Embodiment]
A station-side termination device and a route switching method according to the present embodiment will be described with reference to FIGS. 4 and 5. The route switching method according to the present embodiment is a method before switching without causing packet loss when it becomes necessary to stop the route switching operation for some reason during the route switching operation described in the above embodiment. This is a route switching method that makes it possible to restore the state. Therefore, since the configuration of the TWDM-PON including the station-side termination device according to the present embodiment is the same as that of the TWDM-PON 10 according to the above embodiment, a detailed description will be given with reference to FIG. 1 if necessary. Omit. In FIG. 5, OSU200-1 is referred to as “OSU1”, OSU200-2 is referred to as “OSU2”, ONU300-1 is referred to as “ONU1”, ONU300-2 is referred to as “ONU2”, and ONU300-3 is referred to as “ONU3”. It is written.

FIG. 4 is a schematic diagram for explaining a route switching method according to the present embodiment, and FIG. 5 is a sequence diagram until an input packet from SNI is received by each ONU. Since the operation of the route switching method according to the present embodiment up to time IV is the same as that of the above embodiment, detailed description thereof will be omitted.

As shown in FIG. 5, in order to stop the wavelength switching before the wavelength switching of ONU300-1 is completed at time V, the OLT control unit 140 gives an instruction to stop the wavelength switching using the XT packet shown in FIG. Notified to ONU300-1. The XT packet is transmitted from the control signal generation unit 260 of the OSU200-1. The ONU300-1 that has received the XT packet switches back to the switching source wavelength.

At the same time, the OLT control unit 140 rewrites the LLID allocation table 122 and allocates the original OSU = 1 and the destination OSU = 1 to the LLID = 10 (see time V in FIG. 4). The packet addressed to ONU300-1 sent from the upper network to the OLT100 after the LLID allocation table 122 is rewritten is sent to the OSU200-1. Further, the OSU200-2 clears (discards) the packets stored in the switching queue 224-1 and releases the learning entry (see time V in FIG. 5). The learning entry is released by deleting ONU300-1 and the switching queue 224-1 from the learning table. Further, OSU200-2 targets ONU300-1 for non-switching.

After that, after the time required for the ONU300-1 to switch back to the switching source wavelength elapses, the scheduler unit 250 of the OSU200-1 transmits the packet stored in the switching queue 224-1 to the ONU300-1.

At time VI, the packets stored in the switching queue 224-1 of OSU200-1 are exhausted, and the learning entry is released (see time VI in FIG. 5). The learning entry is released by deleting ONU300-1 and the switching queue 224-1 from the learning table. Further, OSU200-1 targets ONU300-1 for non-switching. After the learning entry is released and the ONU300-1 becomes a non-switchable target, the packet addressed to the ONU300-1 is sent to the optical transmitter 130-1 via the through queue 222 of the OSU200-1 and the scheduler unit 150.

Here, an application example of the station-side termination device and the route switching method according to the present embodiment will be described. The stop of the route switching according to the present embodiment may be forcibly performed by the system operator of the TWDM-PON10, but in this case, it is based on the result of the failure monitoring unit provided in each part of the TWDM-PON10. This is an example of the OLT 100 performing independently. The OLT 100 constantly monitors the operating state of each part of the TWDM-PON 10, including the ONU 300 under its control. Then, when the route switching is executed due to the failure and the TWDM-PON10 system does not operate normally, the route switching stop process is executed. In this case, the sequence of stopping the route switching is as follows.
(1) Route switching execution. The route switching sequence is started by the procedure described above.
(2) A failure occurred in OSU200-2 before the route switching was completed. The mode of failure is not particularly limited, but in this example, it is a failure of the transmission wavelength due to, for example, a failure of the optical transmitter 130-2. The OLT 100 constantly monitors the operating state of the transmission wavelength of each optical transmitter 130. If the route is switched while the optical transmitter 130-2 is out of order, the packet addressed to ONU300-1 cannot be transmitted.
(3) Triggered by the failure detection of the transmission wavelength, the OLT 100 transmits the above-mentioned XT packet toward the ONU300-1 via the OSU200-1.
(4) The sequence of the route switching stop process is started by the above-mentioned procedure. The reception wavelength of ONU300-1 shown in FIG. 5 is switched back.
(5) Route switching stop processing is completed.
As described above, the operation of the OLT 100 in the process of stopping the route switching due to the failure of the OLT 100 is the same as the operation of the OLT for stopping the route switching described above. However, the factor of the process of stopping the route switching is not limited to the failure of the OLT, and may be, for example, a failure occurring in any of the ONU 300s.

According to the OLT (station side terminal device) and the route switching method according to the present embodiment, even if the switching operation is to be stopped during the route switching due to some factor such as a device failure, the switching operation is performed without packet loss. It is possible to stop and switch back to the original state.

Here, in the present embodiment, an example in which one switching queue is used for one ONU to be switched has been described, but the present invention is not limited to this. For example, it is also possible to switch the routes of a plurality of ONUs having the same wavelength switching time using one switching queue.

In each of the above embodiments, an embodiment in which the station-side termination device and the route switching method according to the present invention are applied to TWDM-PON has been described as an example, but the present invention is not limited to this. The station-side termination device and the route switching method according to the present invention may be applied to, for example, in a general network, route switching for load balancing and non-interruptive switching to a redundant route when a failure occurs. Of course, even when applied to a general network, the route switching stop processing is performed according to the above-mentioned procedure.

1 TWDM-PON
2 OLT
3 Controller 4 OSU
5 Optical transmitter / receiver 6 ONU
7 Optical splitter 10 TWDM-PON
100 OLT
110 LLID identification unit 112 LLID identification table 120 OSU distribution unit 122 LLID allocation table 130, 130-1, 130-2, ..., 130-n optical transmitter 140 OLT control unit 200, 200-1, 200-2 , ..., 200-n OSU
210 ONU distribution unit 212 Learning table 220 Buffer unit 222 Through queue 224, 224-1, ..., 224-k Switching queue 250 Scheduler unit 260 Control signal generation unit 300, 300-1, 300-2, ... , 300-m ONU
330, 330-1, 330-2, ..., 330-m Optical receiver 400 Optical splitter

Claims (8)

It is provided with one or more switching buffers and a subscriber-side termination device distribution unit that sends packets addressed to the subscriber-side termination device to be switched to the switching buffer, and one or more subscriptions via a path by a transmission line, respectively. Multiple termination devices connected to the termination device on the user side,
Includes a termination device distribution unit that sends the received packet to the termination device in which the subscriber-side termination device of the destination of the packet is registered.
When the route switching occurs, the termination device distribution unit sends a packet addressed to the subscriber side termination device to be switched to the switching source termination device and the switching destination termination device.
Are each of the subscriber side terminating device distribution unit subscriber side terminating device sending that station side terminating device to the switching buffer packets addressed to the switching target switching source termination device and the switching destination end device,
Station side terminal device control unit and
The identifier assigned to each of the subscriber-side termination devices and the termination device in which the subscriber-side termination device is registered are switched to the first termination device indicating the currently connected termination device. Further includes an identifier assignment table, which is designated and associated with a second termination device indicating the termination device to be switched to in the case.
The terminating device distribution unit determines the terminating device to which the received packet is sent by referring to the identifier assignment table.
The station-side termination device control unit writes a second termination device corresponding to the identifier of the subscriber-side termination device to be switched from the switching source termination device to the switching destination termination device when the route switching occurs. It is a station-side termination device to be replaced.
After the instruction to execute the switching process accompanying the switching of the route is sent from the terminal device of the switching source to the subscriber-side terminal device to be switched, the switching of the route is stopped until the switching process is completed. If so
The station-side termination device control unit sends an instruction to stop the switching process to the subscriber-side termination device to be switched via the switching source termination device.
The subscriber-side termination device to be switched upon receiving the instruction to stop the switching process returns the state of its own device to the state before receiving the instruction to execute the switching process.
Station side termination device . It is provided with one or more switching buffers and a subscriber-side termination device distribution unit that sends packets addressed to the subscriber-side termination device to be switched to the switching buffer, and one or more subscriptions via a path by a transmission line, respectively. Multiple termination devices connected to the termination device on the user side,
Includes a termination device distribution unit that sends the received packet to the termination device in which the subscriber-side termination device of the destination of the packet is registered.
When the route switching occurs, the termination device distribution unit sends a packet addressed to the subscriber side termination device to be switched to the switching source termination device and the switching destination termination device.
Are each of the subscriber side terminating device distribution unit subscriber side terminating device sending that station side terminating device to the switching buffer packets addressed to the switching target switching source termination device and the switching destination end device,
Station side terminal device control unit and
The identifier assigned to each of the subscriber-side termination devices and the termination device in which the subscriber-side termination device is registered are switched to the first termination device indicating the currently connected termination device. Further includes an identifier assignment table, which is designated and associated with a second termination device indicating the termination device to be switched to in the case.
The terminating device distribution unit determines the terminating device to which the received packet is sent by referring to the identifier assignment table.
The station-side termination device control unit writes a second termination device corresponding to the identifier of the subscriber-side termination device to be switched from the switching source termination device to the switching destination termination device when the route switching occurs. It is a station-side termination device to be replaced.
The transmission line is an optical transmission line.
Each of the subscriber-side termination devices is connected to the termination device by setting the reception wavelength to the transmission wavelength of the termination device to which the connection destination is connected.
When the path switching occurs, the station-side termination device control unit receives timing information set so that the wavelength switching is completed after the packets sent to the switching buffer of the switching source termination device are exhausted. The included instruction for wavelength switching from the transmission wavelength of the switching source termination device to the transmission wavelength of the switching destination termination device is sent to the subscriber-side termination device to be switched via the switching source termination device.
When the switching of the path is stopped after the wavelength switching instruction is sent from the switching source terminating device to the subscriber-side terminating device to be switched and before the wavelength switching is completed.
The station-side termination device control unit sends an instruction to stop wavelength switching to the subscriber-side termination device to be switched via the termination device of the switching source.
The subscriber-side termination device to be switched upon receiving the wavelength switching stop instruction switches the reception wavelength back from the transmission wavelength of the switching destination termination device to the transmission wavelength of the switching source termination device.
Station side termination device. After the wavelength switching stop instruction is sent to the subscriber-side termination device to be switched, the station-side termination device control unit has a second unit corresponding to the identifier of the subscriber-side termination device to be switched in the identifier assignment table. Write back the termination device of the above from the termination device of the switching destination to the termination device of the switching source,
After the write-back is complete
The switching destination terminating device sets the subscriber-side terminating device to be switched as the non-switching target after discarding the packets stored in the switching buffer before the write-back.
The switching source terminating device sends the packet accumulated in the switching buffer after the switching back is completed to the switching target subscriber side terminating device, and then sets the switching target subscriber side terminating device as the non-switching target.
The station-side termination device according to claim 2. Each includes one or more switching buffers and a subscriber-side termination device distribution unit that sends a packet addressed to the subscriber-side termination device to be switched to the switching buffer, and one or more subscriptions via a path by a transmission line, respectively. This is a route switching method using a station-side termination device that includes multiple termination devices connected to the main-side termination device.
When the route is switched, the subscriber-side termination device distribution unit of each of the switching source termination device and the switching destination termination device sends a packet addressed to the subscriber-side termination device to be switched to the switching buffer. Send,
When the route is switched normally, the switching source terminating device discards the packet stored in the switching buffer, and the switching destination terminating device subscribes the packet stored in the switching buffer to the switching target. a toggle its route switching method the path without interruption by sending a shut-side terminating device,
When the switching of the route is stopped, the switching destination terminating device discards the packet stored in the switching buffer, and the switching source terminating device subscribes the packet stored in the switching buffer to the switching target. By sending to the terminal device on the user side, the route is cut back without interruption.
Route switching method . The transmission line is an optical transmission line.
Each of the subscriber-side termination devices is connected to the termination device by setting the reception wavelength to the transmission wavelength of the termination device to which the connection destination is connected.
When the path switching occurs, the station-side termination device control unit receives timing information set so that the wavelength switching is completed after the packets sent to the switching buffer of the switching source termination device are exhausted. The included instruction for wavelength switching from the transmission wavelength of the switching source termination device to the transmission wavelength of the switching destination termination device is sent to the subscriber-side termination device to be switched via the switching source termination device.
The station-side termination device according to claim 1. After the wavelength switching instruction is sent to the subscriber termination device to be switched, the station-side termination device control unit switches the first termination device corresponding to the identifier of the subscriber-side termination device to be switched. Rewrite from the terminal device to the terminal device to be switched to,
After the wavelength switching is completed,
The switching source termination device discards the packets stored in the switching buffer and then targets the switching target subscriber-side termination device for non-switching.
The switching destination terminating device sends the packet stored in the switching buffer to the switching target subscriber-side terminating device, and then sets the switching target subscriber-side terminating device as the non-switching target.
The station-side termination device according to claim 5. After the instruction to execute the switching process accompanying the switching of the route is sent from the terminal device of the switching source to the subscriber-side terminal device to be switched, the switching of the route is stopped until the switching process is completed. If so
The station-side termination device control unit sends an instruction to stop the switching process to the subscriber-side termination device to be switched via the switching source termination device.
The subscriber-side termination device to be switched upon receiving the instruction to stop the switching process returns the state of its own device to the state before receiving the instruction to execute the switching process.
The station-side termination device according to claim 2. After the wavelength switching instruction is sent to the subscriber termination device to be switched, the station-side termination device control unit switches the first termination device corresponding to the identifier of the subscriber-side termination device to be switched. Rewrite from the terminal device to the terminal device to be switched to,
After the wavelength switching is completed,
The switching source termination device discards the packets stored in the switching buffer and then targets the switching target subscriber-side termination device for non-switching.
The switching destination terminating device sends the packet stored in the switching buffer to the switching target subscriber-side terminating device, and then sets the switching target subscriber-side terminating device as the non-switching target.
The station-side termination device according to claim 2.

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