JP2019047168A - Office side termination device and route changeover method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a station-side termination device and a route switching method capable of recovering to a state before switching without causing packet loss even when it becomes necessary to stop the wavelength switching operation during the wavelength switching operation. To provide. A switching buffer and a subscriber-side termination device distribution unit that sends a packet addressed to a subscriber-side termination device to be switched to the switching buffer are provided, respectively, and one or a plurality of subscribers are provided via a path by a transmission path. Route switching includes a plurality of termination devices connected to the side termination device and 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 above occurs, the terminating device distribution unit sends a packet addressed to the subscriber-side terminating device to be switched to the switching source terminating device and the switching destination terminating device, and the switching source terminating device and the switching destination terminating device. Each subscriber-side termination device distribution unit sends a packet addressed to the subscriber-side termination device to be switched to the switching buffer. [Selection diagram] Fig. 3

Description

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

  2. Description of the Related Art In recent years, a service called FTTH (Fiber To The Home) using an optical fiber as a transmission path has been widespread for the purpose of providing high-speed and broadband broadband services to general private homes. For providing broadband services by FTTH, an optical access network called a passive optical network (PON) is often used.

  The PON is composed of one station-side terminal device (OLT) and a plurality of subscriber-side terminal devices (ONU: Optical Network Unit) using an optical passive element called an optical splitter (optical coupler). A single optical cable is branched and connected in a one-to-many manner. In PON, an FTTH service can be economically provided by sharing an optical fiber, an OLT, and the like with a plurality of subscribers.

  There is a PON called 10G-EPON (10 Gigabit Ethernet (registered trademark) PON) (for example, see Non-Patent Document 1). In the PON described in this Non-Patent Document 1, TDMA (Time Division Multiple Access) technology is used for communication (uplink 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 respond to an increase in communication demand in the future optical access network, as a next-generation PON having a transmission rate exceeding 10 Gbps, a plurality of TDM-PONs are integrated into one PON infrastructure (PON infrastructure) using WDM (Wavelength Division Multiplexing) technology. ) Research and development related to WDM / TDM-PON (TWDM-PON) constructed 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, the TWDM-PON 1 includes an OLT 2 and a plurality of ONUs 6-1 to ONUs 6-m (m is an integer of 2 or more). The OLT 2 includes a control device 3 that controls the 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 OSUs 4. And an optical transceiver 5 (5-1 to 5-n). Each optical transceiver 5 is connected to a plurality of ONUs 6 via an optical splitter 7.

  For uplink communication, the reception wavelengths of the optical transceivers 5 of the OLT 2 are fixedly assigned so that the reception wavelengths of the optical transceivers 5 of the OLT 2 do not overlap. In this case, the connection between each optical transceiver 5 of the OLT 2 and the ONU 6 can be dynamically switched by changing the transmission wavelength of the optical transceiver (not shown) of the ONU 6. Regarding communication (downlink communication) from OLT 2 to ONU 6, similarly to uplink communication, the transmission wavelength of each optical transceiver 5 of OLT 2 is fixedly assigned, and the reception wavelength of the optical transceiver of ONU 6 is changed, thereby changing OLT 2. The connection between each optical transceiver 5 and the ONU 6 can be dynamically switched. For this reason, TWDM-PON1 has not only wide bandwidth, but also load distribution according to traffic fluctuations, high reliability by path switching at the time of failure, power saving by sleep of optical transceiver and device circuit at low load, etc. There are advantages.

  Here, in the TWDM-PON 1, for example, when the connection between the OLT 2 and the ONU 6 relating to downlink communication is dynamically switched, the optical transceiver 5 of the OLT 2 is switched and the reception wavelength of the ONU 6 is switched. During the switching time until the received wavelength of the ONU 6 is switched from the pre-switching wavelength to the post-switching wavelength, the ONU 6 cannot receive a 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 instantaneous interruption is required.

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

JP 2011-055407 A JP-A-10-229404

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

  Here, in TWDM-PON, the OLT identifies downstream packets in units of ONUs, and distributes the packets to OSU optical transceivers that are assigned transmission wavelengths corresponding to the ONU reception wavelengths at that time.

  When applying the configuration disclosed in Patent Document 2 described above in order to perform path switching without interruption in TWDM-PON, the number of ONUs accommodated in the TWDM-PON is mounted as many buffers as the previous stage of the switch. There is a need to. For this reason, when the number of ONUs accommodated is large, the circuit scale increases. In addition, each buffer requires a capacity that can hold packets for the switching time, and therefore a large buffer amount is required if the time required for switching is long. An increase in circuit scale and buffer amount is a problem in terms of device feasibility.

  Further, when a shared buffer method for sharing a buffer is applied in order to save the buffer amount, the address management information increases as the number of ONUs accommodated increases. For this reason, when the number of ONUs to be accommodated is large, a large memory is required for address management, which is a problem in terms of apparatus feasibility.

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

  The present invention has been made in view of the above-described problems. An object of the present invention is to provide 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. Another object of the present invention is to provide a path switching method for changing the connection between a subscriber-side terminal device and a station-side terminal device without increasing the circuit scale. Further, an object of the present invention is to provide a station that can be restored to the state before switching without causing packet loss even when it is necessary to stop the wavelength switching operation due to some factor during the wavelength switching operation. It is to provide a side termination device and a path switching method.

  In order to achieve the above-described object, a station-side terminating device according to the present invention includes a subscriber-side terminating device that sends one or a plurality of switching buffers and packets addressed to a switching target subscriber-side terminating device to the switching buffer. Each terminal has a branching unit, each of which is connected to one or more subscriber-side terminal devices via a transmission path, and the received packet is registered by the subscriber-side terminal device that is the destination of the packet And a terminating device allocating unit for sending to the terminating device, and when the switching of the path occurs, the terminating device allocating unit sends a packet addressed to the switching target side terminating device to the switching source The subscriber side termination device allocating section of each of the switching source termination device and the switching destination termination device sends a packet addressed to the switching target subscriber side termination device to the switching buffer. What to send to A.

  In order to achieve the above-described object, a path switching method according to the present invention is a subscriber-side termination device distribution that sends one or more switching buffers and packets addressed to a subscriber-side termination device to be switched to the switching buffer. Each of which includes a plurality of terminal units, each of which includes a plurality of terminal devices connected to one or a plurality of subscriber-side terminal devices via a transmission line route, wherein the switching of the route occurs In this case, the subscriber-side termination device allocating 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 path switching is performed. When the switching is normally performed, the switching source terminal device discards the packet stored in the switching buffer, and the switching destination terminal device deletes the packet stored in the switching buffer. It is intended to switch the path without interruption by sending.

  According to the station-side termination device and the path switching method according to the present invention, even when the number of accommodated subscriber-side termination devices is large, connection with the subscriber-side termination device without causing packet loss Can be provided without increasing the circuit scale. Further, according to the station-side termination device and the path switching method according to the present invention, even if it is necessary to stop the path switching operation for some reason during the wavelength switching operation, the packet is not switched before the switching. It becomes possible to recover to the state.

It is a principal part block diagram of TWDM-PON for demonstrating the path | route switching method which concerns on this Embodiment. It is a schematic diagram for demonstrating the path | route switching method which concerns on 1st Embodiment. It is a sequence diagram for demonstrating the path | route switching method which concerns on 1st Embodiment. It is a schematic diagram for demonstrating the path | route switching method which concerns on 2nd Embodiment. It is a sequence diagram for demonstrating the path | 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. However, the drawings are merely schematically shown to the extent that the present invention can be understood. In the following, a preferred configuration example of the present invention will be described. However, numerical conditions and the like are merely preferred examples. Therefore, the present invention is not limited to the following embodiments, and many changes or modifications that can achieve the effects of the present invention can be made 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. FIG. 1 is a main part configuration diagram of a TWDM-PON for explaining a path switching method according to the present embodiment to be described later.

  TWDM-PON is an optical access network using a PON system. In TWDM-PON (optical communication system), a downstream signal from an OLT (station side terminal device) to an ONU (subscriber side terminal device) and an upstream signal from the ONU to the OLT are transmitted and received. In addition, the uplink signal and the downlink signal include data signals transmitted / received between a host network (not shown) connected to the OLT and a user terminal (not shown) connected to the ONU, 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 regarding 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 ONUs 300-1 to m (m is an integer of 2 or more, collectively referred to as “ONU 300”), and an optical splitter 400 that is an optical passive element. Optical fibers are connected between the OLT 100 and the optical splitter 400, and between the ONUs 300-1 to m and the optical splitter 400, respectively.

  The OLT 100 includes an LLID identification unit 110, an OSU sorting unit (terminating device sorting unit) 120, a plurality of OSUs (terminating device) 200-1 to n (n is an integer of 2 or more, and collectively referred to as “OSU200”), A plurality of optical transmitters 130-1 to 130-n (collectively “optical transmitter 130”) and an OLT control unit (station-side terminal device control unit) 140 are configured.

  The LLID identification unit 110 is connected to the OSU sorting unit 120. The LLID identifying unit 110 identifies the destination ONU 300 based on the identification information of the downlink packet input from the upper network. For example, VLAN ID (Virtual Local Area Network IDentifier: VID) included in an Ethernet (registered trademark) packet (frame) can be used as identification information of the downstream packet. The LLID identification unit 110 includes an LLID identification table 112 that associates VIDs with logical link identifiers (LLIDs: Logical Link IDs). Basically, the LLID is assigned to the connected ONUs 300 one to one. For this reason, the LLID identification unit 110 can identify the destination ONU 300 from the VID of the downlink packet using the LLID identification table 112. The LLID identifying unit 110 adds the LLID assigned to the destination ONU 300 to the downlink packet and sends it to the OSU sorting unit 120.

  The OSU distribution unit 120 is connected to a plurality of OSUs 200-1 to 200-n. In the TWDM-PON 10, each ONU 300-1 to m is registered in one of the plurality of OSUs 200-1 to 200-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 OSU 200 is registered for each LLID using two parameters, the switching source OSU 200 and the switching destination OSU 200, for use in path switching described later. The OSU sorting unit 120 sends a downlink packet to the identified OSU 200.

  The OSUs 200-1 to 200-n are connected to the optical transmitters 130-1 to 130-n on a one-to-one basis. Further, different wavelengths (λ1 to λn) are fixedly assigned to the optical transmitters 130-1 to 130-n, respectively. The optical transmitters 130-1 to 130-n are connected to the ONUs 300-1 to 300-m via the 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. Since the OSUs 200-1 to 200-n are connected to the optical transmitters 130-1 to 130-n in a one-to-one relationship, the transmission wavelength of the downstream packet is determined by the OSU 200 in which the destination ONU 300 is registered. Therefore, in the following description, the wavelength assigned to the optical transmitters 130-1 to 130-n connected to a certain OSU 200-1 to n may be expressed as the wavelength assigned to the OSU 200-1 to n.

  Each of the OSUs 200-1 to 200-n includes an ONU distribution unit (subscriber-side terminal device distribution unit) 210, a buffer unit 220, a scheduler unit 250, and a control signal generation unit 260. The buffer unit 220 includes one through queue 222 and one or more switching queues 224-1 to 224 -k (k is an integer of 1 or more) in parallel. Note that the number k of the switching queues 224 corresponds to the number of path switching that can be performed simultaneously. Therefore, a plurality of switching queues 224 are preferably provided. On the other hand, when the number k of the switching queues 224 increases, the circuit scale increases. Therefore, the number k of switching queues 224 is preferably smaller than the number of ONUs 300 that can be registered in each OSU 200 to suppress an increase in circuit scale. The switching queue 224 corresponds to a “switching buffer” according to the present invention.

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

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

  The control signal generator 260 generates a control signal such as a gate packet used for establishing a PON link. The reception wavelength switching instruction in the ONU 300 can be performed using this control signal.

  The through queue 222 and the plurality of switching queues 224-1 to 224-k issue a transmission request to the scheduler unit 250 when a packet is input. The scheduler unit 250 adjusts the output in accordance with the downstream packet transmission request from each of the queues 222 and 224-1 to k and the control signal transmission request from the control signal generation unit 260, and the optical transmitters 130-1 to 130-1. A downstream 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 assignment table 122. Further, the traffic passing through the OLT 100 is monitored to determine the timing and contents of path switching. Further, the reading from the scheduler unit 250 of each OSU 200 is also monitored.

  Further, when changing the OSU 200 that is the registration destination of the switching target ONU 300, the OLT control unit 140 cancels the switching source OSU 200, registers it in the switching destination OSU 200, and switches the switching target OSU 200. Notification of. In addition, about this notification, the OLT control part 140 may instruct | indicate directly to OSU200, and may add and add to that to the packet sent to each OSU200.

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

About the structure except having mentioned above, it can comprise similarly to well-known TWDM-PON.

Next, a route switching method according to the present embodiment will be described with reference to FIGS.
FIG. 2 is a schematic diagram for explaining the path switching method, and FIG. 3 is a sequence diagram until each ONU 300 receives a downlink packet transmitted from the higher level network via the SNI (Service Node Interface). is there. Here, the LLID of the ONU 300-1 is 10, the LLID of the ONU 300-2 is 20, and the LLID of the ONU 300-3 is 30. In other words, in the LLID identification table 112, is assigned to LLID = 10, LLID = 20, and LLID = 30. In FIG. 3, OSU 200-1 is “OSU 1”, OSU 200-2 is “OSU 2”, ONU 300-1 is “ONU 1”, ONU 300-2 is “ONU 2”, and ONU 300-3 is “ONU 3”. It is written. Further, among the input packets from the SNI shown in FIG. 3, X indicates that the packet is destined for ONU1, Y is ONU2, and Z is the destination of ONU3. Further, the suffixes “I” to “VI” shown in FIG. 2 and FIG. 3 each represent time.

At time I, the ONU 300-1 is registered in the OSU 200-1, the ONU 300-2 is registered in the OSU 200-1, and the ONU 300-3 is registered in the OSU 200-2. That is, in the LLID allocation table 122, LLID = 10, switching source OSU (hereinafter referred to as “source OSU”) = 1, switching destination OSU (hereinafter referred to as “destination OSU”) = 1, LLID = 20, source OSU = 1. The source OSU = 1 and the destination OSU = 2 are allocated to the destination OSU = 1 and LLID = 30.
Accordingly, the OSU sorting unit 120 sends the packet Xi (i = 0, 1,...) Addressed to the ONU 300-1 to the OSU 200-1, and the packet Yj (j = 0, 1,...) Addressed to the ONU 300-2. ) Are sent to OSU 200-1, and packets Zk (k = 0, 1,...) Addressed to ONU 300-3 are sent to OSU 200-2. Here, it is assumed that the transmission wavelength of the OSU 200-1 is set to λ1, and the transmission wavelength of the OSU 200-2 is set to λ2.

  The packet Xi passes through the through queue 222 of the OSU 200-1, the scheduler unit 250, and the optical transmitter 130-1, and is sent to the ONU 300-1 with a LLID identifier = 10 as a downstream signal of wavelength λ1. The packet Yj passes through the through queue 222 of the OSU 200-1, the scheduler unit 250, and the optical transmitter 130-1, and is sent to the ONU 300-2 with a LLID identifier = 20 as a downstream signal of wavelength λ1. The packet Zk passes through the through queue 222 of the OSU 200-2, the scheduler unit 250, and the optical transmitter 130-2, and is sent to the ONU 300-3 with a LLID identifier = 30 as a downstream signal of wavelength λ2.

  Here, consider a case where the registration destination (accommodation destination) of the ONU 300-1 is switched from the OSU 200-1 to the OSU 200-2. This switching is performed based on an instruction from the OLT control unit 140 for the purpose of, for example, distribution of communication load.

  At time II, the OLT control unit 140 rewrites the LLID assignment table 122 and assigns source OSU = 1 and 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 the ONU 300-1 sent from the upper network to the OLT 100 is sent to both the OSU 200-1 and the OSU 200-2.

  However, at this time, since the reception wavelength of the ONU 300-1 is λ1, the downstream signal with the wavelength λ2 from the OSU 200-2 cannot be received. Therefore, the OSU 200-1 needs to instruct the ONU 300-1 to switch the reception wavelength to λ2. However, there is a possibility that packets addressed to the ONU 300-1 are accumulated in the OSU 200-1 in an untransmitted state. Further, it may take time to switch the reception wavelength in the ONU 300-1.

  Therefore, in consideration of the time required for wavelength switching of the ONU 300-1 and the time until there is no packet addressed to the ONU 300-1 stored in the OSU 200-1, the wavelength switching for the ONU 300-1 is performed in addition to the wavelength switching. It is better to give instructions at the same time. The instruction is performed by transmitting the XS packet shown in FIG. 3 to the ONU 300-1, and the ONU 300-1 is notified of the switching wavelength and the switching timing. The XS packet is transmitted from the control signal generation unit 260 of the OSU 200-1.

  After time II, when receiving a packet addressed to the ONU 300-1, the OSU 200-1 and the OSU 200-2 determine whether the ONU 300-1 is the ONU 300 to be switched. At time II, when the LLID allocation table 122 is rewritten, the OLT control unit 140 notifies the OSU 200-1 and the OSU 200-2 that the ONU 300-1 is the ONU 300 to be switched. The ONU distribution unit 210 of each of the OSU 200-1 and the OSU 200-2 recognizes that the ONU 300-1 is the ONU 300 to be switched by this notification.

  Subsequently, at time III, the ONU distribution unit 210 of each of the OSU 200-1 and the OSU 200-2 determines whether the ONU 300-1 has been learned or not learned in the learning table 212. Here, since the ONU 300-1 is not registered, it is determined that the ONU 300-1 has not yet been learned. The ONU sorting unit 210 sends an unlearned packet addressed to the ONU 300 to one of the unused switching queues, and causes the learning queue to learn the switching queue. Here, the switching queue 224-1 is selected as an unused switching queue. This switching queue may be selected by selecting an unused switching queue. The switching queue may be selected in ascending order of numbers, or may be selected at random.

  After the switching queue 224-1 is selected, the packet addressed to the ONU 300-1 is sent to the switching queue 224-1, and 10 is stored in the LLID column of the learning table 212 of each of the OSU 200-1 and the OSU 200-2. 1 is registered (see time III in FIG. 2). As a result, the ONU 300-1 has been learned. After the ONU 300-1 has been learned, the ONU distribution unit 210 of each of the OSU 200-1 and the OSU 200-2 refers to the learning table 212 to transfer the packet addressed to the ONU 300-1 to the switching queue 224-1. Send to.

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

  Thereafter, at time V, the OLT control unit 140 rewrites the LLID assignment table 122 and assigns the source OSU = 2 and the destination OSU = 2 to LLID = 10 (see time V in FIG. 2). A packet addressed to the ONU 300-1 sent from the upper network to the OLT 100 after rewriting the LLID allocation table 122 is sent to the OSU 200-2. At the same time, the scheduler unit 250 of the OSU 200-2 transmits the packets stored in the switching queue 224-1 to the ONU 300-1. Further, the OSU 200-1 clears (discards) the packet stored in the switching queue 224-1 and releases the learning entry. The learning entry is released by deleting the ONU 300-1 and the switching queue 224-1 from the learning table 212. The OSU 200-1 sets the ONU 300-1 as a non-switching target.

  At time VI, there are no packets stored in the switching queue 224-1 of the OSU 200-2, and the learning entry is released. The learning entry is released by deleting the ONU 300-1 and the switching queue 224-1 from the learning table 212. The OSU 200-2 sets the ONU 300-1 as a non-switching target. After the learning entry is released and the ONU 300-1 becomes a non-switching target, the packet addressed to the ONU 300-1 is sent to the optical transmitter 130-2 via the through queue 222 and the scheduler unit 250 of the OSU 200-2.

  Note that, for example, when the registration destination of the ONU 300-2 is changed from the OSU 200-1 to the OSU 200-2 while the path of the ONU 300-1 is being switched, the path can be switched by the above-described 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 status of the path switching, and limits the number of ONUs 300 that perform wavelength switching at the same time to the number of switching queues or less.

  According to the OLT (station-side terminal apparatus) and the path switching method of the present invention, the number of ONUs 300 that simultaneously perform switching processing is limited, and switching queues that hold packets that are being switched are stored according to the number of accommodated ONUs. Can be reduced. In addition, since the number of queues is reduced, the amount of memory necessary for buffer address management can be reduced. This makes it possible to economically provide an OLT and a path switching method capable of switching without interruption.

[Second Embodiment]
With reference to FIG.4 and FIG.5, the station side termination | terminus apparatus and the path | route switching method which concern on this Embodiment are demonstrated. In the route switching method according to the present embodiment, when there is a need to stop the route switching operation for some reason during the route switching operation described in the above embodiment, the packet switching method before switching is not generated. This is a route switching method that makes it possible to recover the state. Accordingly, the configuration of the TWDM-PON including the station-side terminal device according to the present embodiment is the same as that of the TWDM-PON 10 according to the above-described embodiment, so that detailed description will be given with reference to FIG. 1 if necessary. Omitted. In FIG. 5, OSU 200-1 is “OSU 1”, OSU 200-2 is “OSU 2”, ONU 300-1 is “ONU 1”, ONU 300-2 is “ONU 2”, and ONU 300-3 is “ONU 3”. It is written.

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

  As shown in FIG. 5, at time V, since the wavelength switching is stopped before the wavelength switching of the ONU 300-1 is completed, the OLT control unit 140 uses the XT packet shown in FIG. The ONU 300-1 is notified. The XT packet is transmitted from the control signal generation unit 260 of the OSU 200-1. The ONU 300-1 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 assignment table 122 and assigns the source OSU = 1 and the destination OSU = 1 to LLID = 10 (see time V in FIG. 4). A packet addressed to the ONU 300-1 sent from the upper network to the OLT 100 after the LLID allocation table 122 is rewritten is sent to the OSU 200-1. Also, the OSU 200-2 clears (discards) the packets stored in the switch queue 224-1 and releases the learning entry (see time V in FIG. 5). The learning entry is released by deleting the ONU 300-1 and the switching queue 224-1 from the learning table. The OSU 200-2 sets the ONU 300-1 as a non-switching target.

  Thereafter, after the time necessary for the ONU 300-1 to switch back to the switching source wavelength has elapsed, the scheduler unit 250 of the OSU 200-1 transmits the packets stored in the switching queue 224-1 to the ONU 300-1.

  At time VI, there are no packets stored in the switching queue 224-1 of the OSU 200-1, and the learning entry is released (see time VI in FIG. 5). The learning entry is released by deleting the ONU 300-1 and the switching queue 224-1 from the learning table. The OSU 200-1 sets the ONU 300-1 as a non-switching target. After the learning entry is released and the ONU 300-1 becomes a non-switch target, the packet addressed to the ONU 300-1 is sent to the optical transmitter 130-1 via the through queue 222 and the scheduler unit 150 of the OSU 200-1.

Here, application examples of the station side termination device and the path switching method according to the present embodiment will be described. Although the path switching stop according to this embodiment may be forcibly performed by the system operator of the TWDM-PON 10, in this case, based on the result of the fault monitoring unit provided in each part of the TWDM-PON 10. This is a case where the OLT 100 performs autonomously. The OLT 100 constantly monitors the operating state of each part of the TWDM-PON 10 including the subordinate ONU 300. Then, in the case where the system of the TWDM-PON 10 does not operate normally when the path switching is executed due to the failure, the path switching stop process is executed. In this case, the path switching stop sequence is as follows.
(1) Route switching execution. The path switching sequence is started in the above-described procedure.
(2) A failure occurs in the OSU 200-2 before the path switching is completed. Although the failure mode is not particularly limited, in this example, for example, the failure of the transmission wavelength is caused by the 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 path is switched while the optical transmitter 130-2 is out of order, packets addressed to the ONU 300-1 cannot be transmitted.
(3) The OLT 100 transmits the above-described XT packet to the ONU 300-1 via the OSU 200-1 using the detection of the transmission wavelength failure as a trigger.
(4) The sequence of the path switching stop process is started according to the procedure described above. The received wavelength is switched back in the ONU 300-1 shown in FIG.
(5) The route switching stop process is completed.
As described above, the operation of the OLT 100 in the path switching stop process due to the failure of the OLT 100 is not different from the operation of the OLT for stopping the path switching described above. However, the cause of the path switching stop process is not limited to the OLT failure, and may be a failure that has occurred in one of the ONUs 300, for example.

  According to the OLT (station-side terminal apparatus) and the path switching method according to the present embodiment, even if an attempt is made to stop the switching operation during path switching due to, for example, 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 switching target ONU has been described, but the present invention is not limited to this. For example, a plurality of ONU paths that have the same wavelength switching time can be switched using a single switching queue.

  In each of the above-described embodiments, the station side termination device and the path switching method according to the present invention have been described as examples applied to TWDM-PON. However, the present invention is not limited to this. The station-side terminal device and the path switching method according to the present invention may be applied to, for example, a path switching for load distribution and an uninterrupted switching to a redundant path when a failure occurs in a general network. Of course, even when applied to a general network, the path switching stop process is performed according to the above-described procedure.

1 TWDM-PON
2 OLT
3 Control device 4 OSU
5 Optical transceiver 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 (9)

One or a plurality of switching buffers and a subscriber-side termination device allocating unit for sending packets addressed to the switching target subscriber-side termination device to the switching buffer are provided, and each of the one or a plurality of subscriptions is routed through a transmission path. A plurality of terminal devices connected to the user-side terminal device;
A terminating device sorting unit that sends the received packet to the terminating device in which the terminating device on the subscriber side of the packet is registered, and
When the switching of the path occurs, the termination device sorting unit sends a packet addressed to the switching target subscriber side termination device to the switching source termination device and the switching destination termination device,
The subscriber-side termination device allocating unit of each of the switching-source termination device and the switching-destination termination device sends a packet addressed to the switching-target subscriber-side termination device to the switching buffer. A station side termination device control unit;
Switching occurred between the identifier assigned to each of the subscriber-side termination devices and the termination device in which the subscriber-side termination device is registered with the first termination device indicating the currently connected termination device. An identifier assignment table that designates and associates with a second termination device indicating a switching destination termination device in the case,
The terminating device allocating unit determines a terminating device to which the received packet is referred with reference to the identifier assignment table,
When the switching of the path occurs, the station-side terminal device control unit writes the second terminal device corresponding to the identifier of the subscriber-side terminal device to be switched from the switching source terminal device to the switching destination terminal device. The station-side termination device according to claim 1. The switching of the path is stopped until the switching process is completed after an instruction to execute the switching process accompanying the switching of the path is sent from the switching source terminal apparatus to the switching target subscriber-side terminal apparatus. If
The station-side terminal device control unit sends an instruction to stop the switching process to the switching target subscriber-side terminal device via the switching source terminal device,
The station-side terminal device according to claim 2, wherein the subscriber-side terminal device to be switched that has received the instruction to stop the switching process switches the state of the own device back to the state before receiving the instruction to execute the switching process. The transmission line is an optical transmission line;
Each of the subscriber-side terminators is connected to the terminator by setting the reception wavelength to the transmission wavelength of the terminator at the connection destination,
When the switching of the path occurs, the station-side terminal device control unit has timing information set so that wavelength switching is completed after there is no packet sent to the switching buffer of the switching source terminal device. The included wavelength switching instruction from the transmission wavelength of the switching source termination device to the transmission wavelength of the switching destination termination device is sent to the switching target subscriber termination device via the switching source termination device. 2. The station side termination device according to 2. After the wavelength switching instruction is sent to the switching target subscriber termination device, the station side termination device control unit sets the first termination device corresponding to the identifier of the switching target subscriber termination device to the switching source. Rewrite from the termination device to the switching destination termination device,
After completing the wavelength switching,
The switching source termination device discards the packet stored in the switching buffer and then sets the switching target subscriber side termination device as a non-switching target.
5. The station side according to claim 4, wherein the terminating device at the switching destination sends the packet stored in the switching buffer to the terminating device at the switching target, and sets the terminating device at the switching target as a non-switching target. Termination equipment. When the switching of the path is stopped after the wavelength switching instruction is sent from the switching source termination device to the switching target subscriber-side termination device until the wavelength switching is completed,
The station-side terminal device control unit sends an instruction to stop wavelength switching to the switching target subscriber-side terminal device via the switching source terminal device,
The subscriber-side terminal device to be switched that has received the wavelength switching stop instruction switches back the received wavelength from the transmission wavelength of the switching destination terminal device to the transmission wavelength of the switching source terminal device. Station side terminal equipment. After the wavelength switching stop instruction is sent to the switching target subscriber-side terminating device, the station-side terminating device control unit sets the second corresponding to the identifier of the switching target subscriber-side terminating device in the identifier assignment table. Write back the end device from the switch-destination device to the switch-source device,
After the writeback is complete,
The terminating device at the switching destination sets the subscriber-side terminating device to be switched to the non-switching target after discarding the packet stored in the switching buffer before the write-back,
The switching source terminating device sends the packet stored in the switching buffer after the completion of the switchback to the switching target subscriber terminating device, and then sets the switching target subscriber terminating device as a non-switching target. Item 7. The station-side termination device according to Item 6. One or a plurality of switching buffers and a subscriber-side termination device allocating unit for sending packets addressed to the switching target subscriber-side termination device to the switching buffer are provided, and each of the one or a plurality of subscriptions is routed through a transmission path. A path switching method using a station-side terminal device including a plurality of terminal devices connected to a user-side terminal device,
When the switching of the path occurs, the subscriber-side termination device allocating unit of each of the switching-source termination device and the switching-destination termination device stores the packet addressed to the switching target subscriber-side termination device in the switching buffer. Send,
When the path switching is performed normally, the switching source terminal device discards the packet stored in the switching buffer, and the switching terminal device deletes the packet stored in the switching buffer. Route switching method that switches the route without interruption by sending it to the terminal device on the user side. When the switching of the path is stopped, the switching destination terminal device discards the packet stored in the switching buffer, and the switching terminal device deletes the packet stored in the switching buffer as a switching target joining device. The route switching method according to claim 8, wherein the route is switched back without interruption by being sent to the person-side terminal device.