JP2012151660A - Intra-station device and communication system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an intra-station device and a communication system that can implement low power consumption.SOLUTION: An intra-station device has a layer 2 switch comprising a shared buffer accumulating a downstream frame and a master station side device which receives the downstream frame from the layer 2 switch and transmits it to a plurality of slave station side devices. The master station side device determines whether a first slave station side device of the plurality of slave station side devices is in a sleep state in which power supply to a part of devices in the first slave station side device is stopped or not; and transmits a frame stop signal for making transmission to the downstream frame addressed to the first slave station side device in the sleep state be stopped. The layer 2 switch stops transmission of the downstream frame addressed to the first slave station side device of the downstream frames accumulated in the shared buffer, when receiving the frame stop signal.

Description

  The present invention relates to an intra-station device and a communication system that communicate with a lower-level device such as a user terminal using a PON (Passive Optical Network) system.

  As a system for drawing in a transmission path from a higher-level device such as a server to a lower-level device, for example, there is a PON system (for example, see Non-Patent Document 1). A master station side device (OLT: Optical Line Terminal) constituting the PON system includes a plurality of interface cards, and each interface card is connected to a plurality of slave station side devices (ONU: Optical Network Unit) on the lower side. The OLT is connected to a layer 2 switch (hereinafter abbreviated as L2SW), and the L2SW is connected to a host device.

  For example, there is a technology for reducing the power consumption of the PON system by stopping the power supply to some devices in the ONU (sleep state) when there is no downstream frame transmission from the host device to the ONU for a predetermined time. Yes (see, for example, Patent Document 1). When an arbitrary ONU shifts to the sleep state, a downstream frame addressed to the arbitrary ONU is accumulated in the buffer of the OLT interface card. When the ONU is released from the sleep state, the OLT reads the accumulated frame and transmits it to the ONU.

IEEE Standard 802.3av, (2009). JP 2008-263281 A

  In the conventional means for reducing the power consumption based on the transition of the ONU to the sleep state, it is necessary to store the downstream frames addressed to all the ONUs in the sleep state in the OLT buffer. there were.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide an in-station apparatus and a communication system capable of reducing power consumption.

  An intra-station apparatus according to the present invention receives a downlink frame transmitted from a higher-level apparatus to a plurality of slave station-side apparatuses, and includes a layer 2 switch including a shared buffer for accumulating the downlink frame, and the layer 2 switch An intra-station device having a master station side device that receives a downlink frame and transmits the downlink frame to a plurality of slave station side devices, wherein the master station side device is a first of the plurality of slave station side devices. A sleep determination unit that determines whether the slave station side device is in a sleep state in which power supply to some devices in the first slave station side device is stopped; and the first slave station side device A frame control signal transmitter for transmitting to the layer 2 switch a frame stop signal for stopping transmission of a downlink frame addressed to the first slave station side device when the state is in a state; A down frame control unit that controls to stop transmission of a down frame addressed to the first slave station side device among the down frames accumulated in the shared buffer when a stop signal is received; To do.

  In addition, the communication system according to the present invention receives a downlink frame transmitted from a higher-level device to a plurality of slave station-side devices, and includes a layer 2 switch including a shared buffer for storing the downlink frame, and the layer 2 switch A communication system having a master station side device that receives the downlink frame from a plurality of slave station side devices that receive the downlink frame from the master station side device, wherein the master station side device includes the plurality of slave station side devices. The first slave station side device when the first slave station side device among the slave station side devices is in a sleep state in which power supply to a part of the devices in the first slave station side device is stopped A frame stop signal for stopping transmission of a downlink frame addressed to the layer 2 switch is transmitted to the layer 2 switch. When the layer 2 switch receives the frame stop signal, the layer 2 switch stores the downlink frame stored in the shared buffer. Characterized by stopping the transmission of the downlink frame of the first daughter devices destined out of.

  According to the intra-station apparatus and the communication system of the present invention, when the OLT determines that a specific ONU is in a sleep state, the OLT transmits a downlink frame addressed to the specific ONU among the downlink frames stored in the shared buffer in the L2SW. Since the flow control is performed so as to stop, the power consumption of the PON system can be reduced.

The block diagram which shows Embodiment 1 of this invention. The figure which showed the structure of the existing pause frame. The figure which showed the frame structure of the frame stop signal which embedded the identification information of ONU in the pause frame. The sequence diagram explaining the operation | movement which stops reading of the downstream frame addressed to ONU in a sleep state. The sequence diagram explaining the operation | movement which cancels | releases the read stop of the ONU addressed downstream frame in a sleep state when a downstream frame generate | occur | produces in the sleep state of ONU. The sequence diagram explaining the operation | movement which cancels | releases the read stop of the ONU addressed downstream frame in a sleep state, when the upstream frame generate | occur | produces in the sleep state of ONU. The figure which showed the frame structure of the frame control signal which added the VLAN tag (TAG) to the pause frame. The figure which showed the frame structure of the frame stop signal which embedded the MAC address of ONU in a sleep state in the transmission source address area | region of a pause frame.

Embodiment 1 FIG.
FIG. 1 is a configuration diagram illustrating Embodiment 1 of the present invention.

  The PON system is configured by connecting an OLT 100 and a plurality of ONUs 200 with an optical fiber via an optical coupler 150 that is an optical device that equally distributes optical power. Further, the L2SW 400 is connected to the upper side of the OLT 100. A system configured with the OLT 100, the plurality of ONUs 200, and the L2SW 400 is defined as a communication system. A device including the OLT 100 and the L2SW is defined as an in-station device 1000. A lower device 300 such as a PC is connected to the lower side of the ONU 200, and a higher device 500 such as a server is connected to the upper side of the L2SW 400.

  The OLT 100 includes a plurality of interface cards 110-1 to 110 -N, and an ONU 200 is connected to the lower side of the PON interface 111 of each interface card 110. The upper interface 112 of the interface card 110 in the OLT 100 is connected to the L2SW 400, and each interface card 110 is concentrated by the L2SW 400.

  The OLT 100 will be described in detail. The interface card 110-1 provided in the OLT 100 includes a PON interface 111, an upper interface 112, an OLT frame separation unit 113, a first buffer unit 114, an OLT read control unit 115, an OLT frame read unit 116, 1 optical transmission / reception unit 117, first buffer monitoring unit 118, first sleep processing unit 119, sleep determination unit 120, and frame control signal transmission unit 121. The same applies to the other interface cards 110-i to 110-N.

  The OLT frame separation unit 113 separates the downstream frames transmitted via the higher-order interface 112 for each of the destination ONUs 200-1-1-1 to 200-1-N, and accumulates them in the first buffer unit 114. The OLT frame separation unit 113 identifies a destination ONU based on a destination MAC (Media Access Control) address in the frame. In addition, you may identify based on VLAN (Virtual Local Area Network) ID instead of a MAC address.

  The first buffer unit 114 accumulates downlink frames to be transmitted to the ONUs 200-1-1-1 to 200-1-N connected to the interface card 110-1.

  The OLT read control unit 115 controls the OLT frame read unit 116 so as to read the downlink frames stored in the first buffer unit 114 based on a predetermined priority.

  The OLT frame reading unit 116 reads the downlink frame from the first buffer unit 114 based on the control of the OLT read control unit 115, and divides the read downlink frame into a plurality of time intervals (time division multiplexing). To the optical transmission / reception unit 117.

  The first optical transmission / reception unit 117 converts the downstream frame output from the OLT frame reading unit 116 from an electrical signal to an optical signal, and transmits all the ONUs 200-1-1 to 200-1 -N via the PON interface 111. Multicast to. The ONUs 200-1-1-1 to 200-1-N receive only the frames addressed to the received downlink frames and discard the others.

  The first optical transceiver 117 receives the optical signals transmitted from the ONUs 200-1-1-1 to 200-1-N and converts them into electrical signals.

  The first buffer monitoring unit 118 monitors the accumulation amount of downstream frames addressed to the ONUs 200-1-1-1 to 200-1-N accumulated in the first buffer unit 114. When a downstream frame addressed to a specific ONU is accumulated, the information of the ONU and the downstream frame accumulation amount information are output to the first sleep processing unit 119 as a downstream monitoring signal.

  Based on the downlink monitoring signal from the first buffer unit 118, the first sleep processing unit 119 determines an ONU in which no downlink frame has been accumulated for a predetermined time (hereinafter referred to as monitoring time). Then, a sleep request signal for requesting the ONU to shift to the sleep state is transmitted to the ONU that has not accumulated the downstream frame. The sleep request signal includes information about the time to start sleep (sleep start time) and how long to sleep (sleep time). The ONU 200 that has received the sleep request signal sleeps according to this information. The sleep state is maintained from the start time to the sleep time.

  Note that “ONU is in a sleep state” means that the ONU has stopped supplying power to some of the devices in the ONU. In the present embodiment, as an example, a state where a second optical transmission / reception unit 201 (described later) in the ONU 200 is OFF will be described as a “sleep state”, but the present invention is not limited to this. . For example, only the optical transmission unit of the second optical transmission / reception unit 201 may be stopped, only the optical reception unit may be stopped, or power supply to a PON chip (not shown in FIG. 1) may be stopped.

  Further, based on the downlink monitoring signal, the first sleep processing unit 119, when the downlink frame addressed to the ONU in the sleep state is accumulated in the first buffer unit 114, the wakeup signal to the ONU. Send. Details of the wake-up signal will be described later.

  The sleep determination unit 120 causes each ONU to sleep based on a sleep approval signal, a wakeup approval signal, and a wakeup notification signal (details of which will be described later) sent from the ONUs 200-1-1-1 to 200-1-N. It is determined whether it is in a state, and the determination result and information of the target ONU are output to the frame control signal transmission unit 121 as a determination result signal.

  Based on the determination result signal from the sleep determination unit 120, the frame control signal transmission unit 121 embeds identification information of the ONU in the sleep state in the pause frame that controls the flow of the downstream frame between the higher-level device 500 and the ONU 200. Then, a frame control signal is generated and transmitted to the L2SW 400 via the upper interface 112. The ONU identification information may be a MAC address, a VLAN ID, or the like, for example.

  The configuration of the pause frame and the frame configuration of the frame control signal will be described with reference to FIGS. FIG. 2 is a diagram illustrating a configuration of a pause frame used for flow control between apparatuses connected by Ethernet (registered trademark). The pause frame consists of a 6-byte destination address, a 6-byte transmission source address, a 2-byte length / type, a 2-byte operation code, a 2-byte interruption time, a 42-byte padding, and a 4-byte FCS (Frame Check Sequence). And have.

  In the present embodiment, a frame control signal is generated using a frame in which ONU identification information is embedded using part or all of the padding area of the existing pause frame shown in FIG. The frame configuration is shown in FIG. The L2SW 400 reads the interruption and ONU identification information from the received frame control signal. During the interruption time, the transmission of the downstream frame addressed to the ONU corresponding to the read identification information is stopped. Further, when the L2SW 400 receives the frame control signal in which the interruption time is set to “0”, the L2SW 400 resumes transmission of the downstream frame addressed to the corresponding ONU. That is, the frame control signal includes information on the ONU in the sleep state and information for instructing stop or restart of the downstream frame from the intra-station apparatus 1000 to the ONU in the sleep state. Hereinafter, a frame control signal that controls to stop transmission of a downlink frame is defined as a frame stop signal, and a frame control signal that is controlled to resume transmission of a downlink frame (that is, a signal set to interruption time 0) is defined as a frame restart signal. Will be explained. Note that the frame resumption signal does not necessarily have to be set to 0 in the interruption time, and may be a predetermined value as long as the arrival of the downstream frame to the ONU 200 is not delayed.

  Returning to FIG. 1, the ONU 200 will be described in detail by taking the ONU 200-1-1 as an example. The ONU 200-1-1 includes a second optical transmission / reception unit 201, a second buffer unit 202, a second buffer monitoring unit 203, and a second sleep processing unit 204. The same applies to the other ONUs 200.

  The second optical transmission / reception unit 201 converts the downstream frame from the OLT 100 from an optical signal to an electrical signal and transmits the converted signal to the lower level apparatus 300-1. When the sleep request signal or wake-up signal described above is sent from the OLT 100, the optical signal is converted into an electric signal and output to the second sleep processing unit 204.

  The second buffer unit 202 accumulates the upstream frame addressed to the higher-level device 500 transmitted from the lower-level device 300-1-1.

  The second buffer monitoring unit 203 monitors the amount of uplink frames accumulated in the second buffer unit 202. When the uplink frame is accumulated, an uplink monitoring signal for notifying the accumulation is output to the second sleep processing unit 204.

  The second sleep processing unit 204 outputs a power control signal to the second optical transmission / reception unit 201 based on an instruction from the OLT 100, and controls the power of the second optical transmission / reception unit 201 to be turned on or off. When a sleep request signal is sent from the OLT 100, the second sleep processing unit 204 outputs a power control signal to the second optical transmission / reception unit 201 at the sleep start time based on its own internal timer and turns off. To do. Then, when the sleep time elapses, the second sleep processing unit 204 outputs a power control signal to the second optical transmission / reception unit 201 and turns on again (sleep return).

  When a predetermined time elapses after returning from sleep, the second sleep processing unit 204 outputs the power control signal to the second optical transmission / reception unit 201 again to turn it off, and shifts to the sleep state. In this way, the ONU 200 performs an operation of repeatedly starting and stopping at regular time intervals.

  When the second sleep processing unit 204 is in the sleep return state and receives a wake-up signal from the OLT 100, the second sleep processing unit 204 enters a wake-up state, outputs a power control signal to the second optical transmission / reception unit 201, and turns on. Will be maintained. That is, the wake-up state of the ONU 200 refers to a state in which the ONU 200 does not enter the sleep state unless the OLT 100 requests the sleep again.

  When receiving the wake-up signal from the OLT 100, the second sleep processing unit 204 transmits a wake-up approval signal for notifying that the wake-up is approved to the OLT 100.

  When the second sleep processing unit 204 receives an uplink monitoring signal from the second buffer monitoring unit 203 during the sleep state of the ONU 200-1-1, it outputs a power control signal to the second optical transmission / reception unit 201. Turns on forcibly and shifts to the wake-up state. When the upstream frame transmission to the OLT 100 is permitted, a wakeup notification signal indicating that the state has shifted to the wakeup state is transmitted to the OLT 100 via the second optical transmission / reception unit 201.

  Next, details of the L2SW 400 will be described. The L2SW 400 includes an L2SW frame separation unit 401, a shared buffer 402, a plurality of L2SW frame reading units 403-1 to 403-N, and a plurality of downlink frame control units 410-1 to 410-N. The plurality of L2SW frame reading units 403-1 to 403-N and the plurality of downlink frame control units 410-1 to 410-N correspond to the interface cards 110-1 to 110-N of the OLT 100, respectively.

  The L2SW frame separation unit 401 distributes and stores the downstream frames from the higher-level device 500 to the shared buffer 401.

  The shared buffer 402 is a buffer that accumulates downlink frames addressed to all ONUs 200 connected to the intra-station apparatus 1000.

  The L2SW frame reading unit 403 reads a downlink frame addressed to the ONU 200 connected to each interface card 110 in the OLT 100 from the downlink frames stored in the shared buffer 402 and transmits the frame to the OLT 100. For example, with regard to the L2SW frame reading unit 403-1, the downlink frames addressed to the ONUs 200-1-1-1 to 200-1-N connected to the corresponding interface card 110-1 are read from the shared buffer 402, and the interface card is read. 110-1 is transmitted.

  In addition, the L2SW frame reading unit 403-1 stops or restarts reading of the downstream frame addressed to each ONU based on the control from the downstream frame control unit 410-1.

  The downlink frame control unit 410-1 receives the frame stop signal transmitted from the downlink frame control signal transmission unit 121 of the OLT 100, and among the downlink frames stored in the shared buffer 402, the downlink frame addressed to the ONU in the sleep state L2SW frame reading section 403-1 is controlled so as to stop transmission. Also, it receives the frame resumption signal and controls the L2SW frame reading unit 403-1 so as to resume transmission of the downstream frame addressed to the ONU in the sleep state accumulated in the shared buffer 402.

  The details of the downlink frame control unit 410 will be described using the downlink frame control unit 410-1 as an example. The downlink frame control unit 410-1 includes a frame control signal analysis unit 404, a shared buffer monitoring unit 405, and an L2SW read control unit 406.

  The frame control signal analysis unit 404 extracts information about ONU identification information and interruption time from the frame control signal, and outputs the information to the L2SW read control unit 406.

  Based on the output from the frame control signal analysis unit 404, the L2SW readout control unit 406 controls the L2SW frame readout unit 403-1 so as to stop or restart the downlink frame transmission (reading) addressed to the corresponding ONU.

  The shared buffer monitoring unit 405 monitors the accumulated amount of downlink frames addressed to the ONU 200-1 connected to the interface card 110-1 among the downlink frames accumulated in the shared buffer 402. When there is a downstream frame accumulation, the destination ONU information and the accumulation amount information are output as a shared monitoring signal to the L2SW read control unit 406 for notification.

  When the L2SW read control unit 406 receives the shared monitoring signal during sleep of the ONU 200 and is notified of the accumulation of the downstream frame addressed to the ONU 200, the L2SW frame readout is performed so as to cancel the stop of reading the downstream frame addressed to the ONU 200. The unit 403-1 is controlled.

  Next, the downlink frame flow control operation according to the first embodiment will be described with reference to the sequence diagrams of FIGS. Hereinafter, description will be made assuming that the ONU 200-1-1 shifts to the sleep state as an example.

  A flow control operation for stopping reading of a downstream frame addressed to the sleep ONU after the ONU 200-1-1 enters the sleep state will be described with reference to the sequence diagram of FIG. In this series of operations, no uplink or downlink frame is generated.

  First, the ONU sleep process in step S1 will be described. If the first sleep processing unit 119 of the OLT 100 is not notified from the first buffer unit 114 that the downstream frame has been stored for the ONU 200-1-1 during the monitoring time, the first sleep processing unit 119 sends a sleep request signal to the ONU 200-1. -1 (step S1a). The sleep request signal includes information of sleep time T3 and sleep time T4-T3.

  The second sleep processing unit 204 of the ONU 200-1-1 that has received the sleep request signal transmits a sleep approval signal to the OLT 100 (step S1b). When the sleep determination unit 120 of the OLT 100 receives the sleep approval signal, the sleep determination unit 120 of the OLT 100 determines that the ONU 200-1-1 has shifted to the sleep state, and the ONU sleep process ends (time T1). The above is the ONU sleep process. Thereafter, the ONU 200-1-1 shifts to the sleep state at time T3 (> T2) and maintains the sleep state until time T4.

  Next, processing for stopping a downstream frame addressed to an ONU that is in a sleep state will be described. When the ONU sleep process is completed at time T1 (step S1), the frame control signal transmission unit 121 of the OLT 100 determines, based on the determination result signal from the sleep determination unit 120, the downlink frame control unit 410-1 of the L2SW 400. A frame stop signal set so as to stop the flow of the downstream frame addressed to the ONU in the sleep state during the interruption time Tp is transmitted (step S2).

  When the L2SW 400 receives the frame stop signal at time T2, the downstream frame control unit 410-1 reads out the downstream frame addressed to the ONU 200-1-1 from the downstream frames stored in the shared buffer 402 from time T2 to time T6. Flow control is performed so as to stop during the period (Tp).

  If no upstream frame or downstream frame occurs, it is not necessary to cancel the reading stop of the downstream frame. Therefore, when no uplink frame or downlink frame occurs, the OLT 100 continues to send a frame stop signal to the L2SW 400 at a time interval shorter than the interruption time Tp in order to prevent cancellation of reading stop of the downlink frame (step S3). ).

  For example, in the example of FIG. 4, when the time T6 is reached, the frame stop signal received by the L2SW 400 at time T2 has elapsed, and the reading of the downstream frame is resumed. Therefore, the OLT 100 performs the frame at time T5 before time T6. Send a stop signal.

  With reference to the sequence diagram of FIG. 5, a description will be given of the reading stop cancellation operation of the downstream frame addressed to the ONU 200-1-1 when the downstream frame addressed to the ONU 200-1-1 occurs during the sleep state of the ONU 200-1-1. .

  When the ONU sleep process is completed between the OLT 100 and the ONU 200-1-1 at time T01 (step S01), the OLT 100 transmits a frame stop signal set to the interruption time Tp to the L2SW 400 (step S02).

  Receiving the frame stop signal at time T02, the L2SW 400 stops reading the downlink frame addressed to the ONU 200-1-1 from the shared buffer 402 until time T07.

  On the other hand, the ONU 200-1-1 shifts from the wake-up state to the sleep state at the time T03 designated by the OLT 100 based on the ONU sleep process, and enters the sleep state until the time T05 designated by the OLT 100.

  The process up to this point is the same as the example of FIG. 4 described above, but a downstream frame addressed to the ONU 200-1-1 is sent from the higher-level device 500 to the L2SW 400 at time T04 when the ONU 200-1-1 is sleeping. Then (step S03), the L2SW 400 cancels the downlink frame reading stop process and transmits the downlink frame to the ONU 200-1-1. The operation will be described below.

  When a downstream frame addressed to the ONU 200-1-1 is sent, first, the downstream frame control unit 410-1 transmits to the OLT 100 only one downstream frame addressed to the ONU 200-1-1 to the OLT 100 (step S04). .

  Specifically, the shared buffer monitoring unit 405 of the downstream frame control unit 410-1 detects a downstream frame addressed to the ONU 200-1-1 and outputs a shared monitoring signal to the L2SW read control unit 406. Then, the L2SW read control unit 406 instructs the L2SW frame read unit 403-1 to read only one downlink frame addressed to the ONU 200-1-1 based on the shared monitoring signal, and the L2SW frame read unit 403-1 performs the OLT 100. One frame is transmitted.

  When the OLT 100 receives one downlink frame addressed to the ONU 200-1-1 from the L2SW 400, the OLT 100 accumulates the one frame in the first buffer unit 114 and changes the ONU 200-1-1 from the sleep state to the wake-up state. A wakeup signal is transmitted so as to shift (step S05). The OLT 100 can recognize that a downlink frame addressed to the ONU 200-1-1 has occurred by receiving one downlink frame from the L2SW 400.

  Specifically, the first buffer monitoring unit 118 in the OLT 100 detects the downlink 1 frame addressed to the ONU 200-1-1 transmitted from the L2SW 400 from the first buffer unit 114, and transmits the downlink monitoring signal to the first monitoring signal. The data is output to the sleep processing unit 119. Then, the first sleep processing unit 119 that has received the downlink monitoring signal generates a wake-up signal and transmits it to the ONU 200-1-1. By doing this, the L2SW 400 can notify the OLT 100 that only one frame has been transmitted and can notify that the downstream frame has been accumulated. Therefore, the storage capacity of the first buffer unit 114 in the OLT 100 is hardly increased and power consumption is not hindered. .

  The time at which the OLT 100 transmits the wake-up signal to the ONU 200-1-1 may be within the time period after the time T05 when the ONU 200-1-1 shifts from the sleep state to the sleep return state and before the shift to the sleep state again. However, as in the example of FIG. 5, it is preferable to transmit at a timing at which the wake-up signal arrives immediately after time T05 when the ONU 200-1-1 shifts to the sleep recovery state. By doing so, the ONU 200-1-1 can receive the wake-up signal and enter the wake-up state as soon as it enters the sleep recovery state, so that the subsequent processing can be performed quickly and the downstream frame can be received without delay. Is possible.

  The ONU 200-1-1 that has received the wake-up signal enters a wake-up state, and the second sleep processing unit 204 transmits a wake-up approval signal to the OLT 100 (step S06).

  When the OLT 100 receives the wake-up approval signal from the ONU 200-1-1, the OLT 100 recognizes that the ONU 200-1-1 is in the wake-up state and accumulates the ONU 200-1-1 in the shared buffer 402 of the L2SW 400. A frame resumption signal is generated and transmitted to the L2SW 400 so as to cancel the reading stop process of the downlink frame being received (step S07).

  Specifically, the sleep determination unit 120 of the OLT 100 receives the wake-up approval signal from the ONU 200-1-1, determines that the ONU 200-1-1 is in the wake-up state, and determines the determination result as a determination result signal. To the frame control signal transmission unit 121. Upon receiving the determination result signal, the frame control signal transmission unit 121 embeds the identification information of the ONU 200-1-1 and the interruption time “0” in the pause frame, and transmits the pause signal to the downstream frame control unit 410-1 of the L2SW 400. To do.

  Receiving the frame restart signal at time T06, the L2SW 400 cancels the downlink frame reading stop process addressed to the ONU 200-1-1 and restarts reading. Then, after time T06 when reading is resumed, the downstream frame is transmitted to the ONU 200-1-1 via the OLT 100 (step S08).

  The time for stopping the reading of the downstream frame was set to the interruption time Tp (T07-T02). However, since the downstream frame was transmitted from the higher-level device 500 during the sleep of the ONU 200-1-1, the reading of the downstream frame was stopped. The time is T06-T02.

  With reference to the sequence diagram of FIG. 6, a description will be given of an operation for canceling reading stop of a downstream frame addressed to the ONU 200-1-1 when an upstream frame is generated while the ONU 200-1 is in the sleep state.

  Since the ONU sleep process in step S001 and the frame stop signal transmission in step S002 are the same as steps S1 and S2 in FIG. 4 or steps S01 and 02 in FIG. 5, the description thereof is omitted here. The ONU 200-1-1 shifts to sleep at time T003 and maintains the sleep state until time T005.

  When the upstream frame is transmitted from the lower-level apparatus 300-1-1 to the ONU 200-1-1 at time T004 when the ONU 200-1-1 is in the sleep state (step S003), the ONU 200-1-1 returns to sleep. After time T005, a wakeup notification signal for notifying the transition to the wakeup state is transmitted to the OLT 100 (step S004). In the example of FIG. 6, a wake-up notification signal is transmitted when returning from sleep (time T005).

  Specifically, during sleep of the ONU 200-1-1, the second buffer monitoring unit 204 detects an upstream frame accumulated in the second buffer unit 202, and sends an upstream monitoring signal to the second sleep processing unit 204. Output to. The second sleep processing unit 204 transmits a wake-up notification signal to the OLT 100 after the sleep return time based on the uplink monitoring signal. Note that the ONU 200-1-1 cannot transmit the wake-up notification signal during the time since the OLT 100 is not permitted to transmit the upstream frame during the sleep state (T005-T003).

  The ONU 200-1-1 transmits an upstream frame to the OLT 100 after time T005 (step S005). Specifically, when the second sleep processing unit 204 instructs the second buffer unit 202 to transmit, an upstream frame is transmitted from the second buffer unit 202 to the OLT 100.

  In the example of FIG. 6, the ONU 200-1-1 transmits an uplink frame a predetermined time after transmitting the wakeup notification signal, but the uplink frame is transmitted simultaneously with the wakeup notification signal. You may send it.

  The upstream frame is stored in an upstream frame buffer (not shown in FIG. 1) in the interface card 110-1, and is subjected to certain processing and transmitted to the upper network.

  The OLT 100 that has received the wake-up notification signal from the ONU 200-1-1 transmits a frame resumption signal to the L2SW 400 in order to cancel the reading stop process for the downstream frame (step S006).

  Specifically, the sleep determination unit 120 receives the wake-up notification signal, determines that the ONU 200-1-1 has shifted from the sleep state to the wake-up state, and uses the determination result as a determination result signal as a frame control signal transmission unit. It outputs to 121. Upon receiving the determination result signal, the frame control signal transmission unit 121 embeds the identification information of the ONU 200-1-1 and the interruption time “0” in the pause frame, and transmits the pause signal to the downstream frame control unit 410-1 of the L2SW 400. To do.

  Receiving the frame resumption signal at time T006, the L2SW 400 cancels the downlink frame reading stop process addressed to the ONU 200-1-1 and resumes reading. When the downlink frame is transmitted from the higher-level apparatus 500 after time T06 when reading is resumed (time T007), the L2SW 400 transmits the downlink frame to the ONU 200-1-1 via the OLT 100 (step S007).

  As for the timing at which the OLT 100 transmits the frame resumption signal to the L2SW 400, the downstream frame is not always generated when the wakeup notification signal is received from the ONU 200-1-1. Therefore, the wakeup notification signal is received. Thus, the frame resumption signal must not be transmitted immediately. In the example of FIG. 6, it is only necessary that the frame restart signal can reach the L2SW 400 by the time T007 when the downstream frame is sent to the L2SW 400.

  However, since the ONU 200-1-1 is already in the wake-up state at the stage of receiving the wake-up notification signal and can receive the downstream frame at any time, the OLT 100 receives the wake-up notification signal and immediately receives the frame. It is preferable to cancel the reading stop of the downstream frame by transmitting a restart signal to the L2SW 400. By doing so, the ONU 200-1-1 can receive the downstream frame immediately after shifting from the sleep state to the wake-up state, thereby improving the traffic efficiency.

  As described above, according to Embodiment 1 of the present invention, when a specific ONU 200 shifts to a sleep state, the OLT 100 transmits a frame stop signal for stopping transmission of a downlink frame addressed to the ONU 200 to the L2SW 400, The L2SW 400 stops transmission of downlink frames addressed to the ONU 200 in the sleep state among the downlink frames stored in the shared buffer 402 for a predetermined time (interruption time). By doing so, the downstream frames transmitted from the higher-level device 500 during the sleep state of the ONU 200 can be accumulated in the shared buffer 402 of the L2SW 400, so that the buffer mounting amount in the OLT 100 can be reduced and the in-station device can be reduced. Power consumption can be reduced.

  Note that if the downstream frame addressed to the ONU 200 in the sleep state is accumulated in the shared buffer 402 in the L2SW 400, the buffer mounting amount in the L2SW 400 is required conventionally. However, the shared buffer 402 has a configuration in which a plurality of interface cards in the OLT 100 are concentrated, and the buffer usage efficiency can be increased by the statistical multiplexing effect. That is, when viewed as an in-station device 1000 that combines the OLT 100 and the L2SW 400, the buffer mounting amount can be reduced, and the power consumption can be reduced. As a result, the power consumption of the entire PON system can be reduced.

  In FIG. 3, the frame configuration of the frame control signal is configured to embed ONU identification information using part or all of the padding area of the pause frame, but the frame configuration shown in FIG. 7 may be used.

  FIG. 7 shows a frame configuration in which a VLAN tag (TAG) is added to an existing pause frame. In this case, the ONU identification information is a VLAN ID in the VLAN tag, and the L2SW 400 identifies the destination ONU of the downstream frame by the VLAN ID. The TAG is 4 bytes, and is composed of a 2-byte TPID (Tag Protocol Identifier), a 3-bit priority, a 1-bit CFI (Canonical Format Identifier), and a 12-bit VLAN ID.

  Further, instead of the frame configuration of the frame control signal shown in FIG. 3 or FIG. 7, the frame configuration shown in FIG. 8 may be used.

  FIG. 8 shows a frame configuration in which the sleep ONU MAC address is embedded in the source address area of the pause frame. The ONU identification information in this case is a MAC address, and the L2SW 400 identifies the downstream frame destination ONU by the MAC address.

  4, the sleep operation may be performed based on a sleep request from the ONU 200 instead of an instruction (sleep request signal) from the OLT 100 to the ONU 200. In that case, a sleep request is made from the ONU 200 to the OLT 100, and the OLT 100 issues a sleep approval to the ONU 200. When a sleep request is notified from the ONU 200, the sleep determination unit 120 of the OLT 100 recognizes the sleep transition of the ONU 200, and the sleep process ends.

  In FIG. 4, when no uplink frame or downlink frame occurs, the OLT 100 sends a frame stop signal to the L2SW 400 at a time interval shorter than the interruption time Tp in order to prevent cancellation of reading stop of the downlink frame. Although it has been described that the transmission is continued, the frame stop signal may be transmitted only once by setting the interruption time Tp for a long time without doing this.

  In FIG. 5, it has been described that when the downstream frame is sent to the L2SW 400 during the sleep of the ONU 200-1-1, the downstream frame reading stop process is canceled and only one frame is transmitted to the OLT 100. For example, several frames that do not hinder an increase in the storage capacity of the first buffer unit 114 may be used. In addition, one frame transmitted from the higher-level device 500 may not be transmitted to the OLT 100, and for example, the shared buffer monitoring unit 405 or the like may notify the first sleep processing unit 119 that a downstream frame has been transmitted directly. .

100 OLT
110-1 to 110-N interface card 111 PON interface 112 upper interface 113 OLT frame separation unit 114 first buffer unit 115 OLT read control unit 116 OLT frame reading unit 117 first optical transmission / reception unit 118 first Buffer monitoring unit 119 first sleep processing unit 120 sleep determination unit 121 frame control signal transmission unit 150-1 to 150-N optical coupler 200-1-1 to 200-1-N ONU
201 Second optical transmission / reception unit 202 Second buffer unit 203 Second buffer monitoring unit 204 Second sleep processing unit 300-1-1-1 to 300-1-N Lower-level device 400 L2SW
401 L2SW frame separation unit 402 Shared buffer 403-1 to 403-N L2SW frame reading unit 404 Frame control signal analysis unit 405 Shared buffer monitoring unit 406 L2SW reading control unit 410-1 to 410-N Downstream frame control unit 500 Host device 1000 In-station device

Claims (9)

A layer 2 switch including a shared buffer for receiving a downlink frame transmitted from a higher-level device to a plurality of slave station-side devices and storing the downlink frame;
An intra-station device comprising: a master station side device that receives the downlink frame from the layer 2 switch and transmits the downlink frame to a plurality of slave station side devices;
The master station side device
A sleep determination unit that determines whether a first slave station side device among the plurality of slave station side devices is in a sleep state in which power supply to some devices in the first slave station side device is stopped; ,
A frame control signal transmission unit configured to transmit a frame stop signal for stopping transmission of a downlink frame addressed to the first slave station side device to the layer 2 switch when the first slave station side device is in the sleep state; Prepared,
The layer 2 switch
A downlink frame control unit for controlling to stop transmission of a downlink frame addressed to the first slave station side device among the downlink frames stored in the shared buffer when the frame stop signal is received; In-station equipment characterized. The downlink frame control unit includes a shared buffer monitoring unit that monitors the accumulation of the downlink frame in the shared buffer,
When the shared buffer monitoring unit detects that the downlink frame addressed to the first slave station side device is accumulated in the shared buffer, the layer 2 switch has stored the downlink frame in the master station side device. Notice that
The master station side device that has received the notification cancels the sleep state of the first slave station side device, and the frame control signal transmission unit resumes transmission of a downlink frame addressed to the first slave station side device. Send a restart signal to the downlink frame control unit,
The downlink frame control unit, when receiving the frame resumption signal, controls to resume transmission of a downlink frame addressed to the first slave station side device among the downlink frames stored in the shared buffer. The intra-station device according to claim 1.   3. The layer 2 switch notifies the master station side device that the downlink frame has been accumulated by transmitting one downlink frame addressed to the first slave station side device. The in-station device described in 1. The frame control signal transmission unit transmits a downstream frame addressed to the first slave station side device when the first slave station side device is released from the sleep state due to accumulation of an upstream frame addressed to the higher order side device. A frame resumption signal for resuming transmission is transmitted to the downlink frame control unit;
The downlink frame control unit, when receiving the frame resumption signal, controls to resume transmission of a downlink frame addressed to the first slave station side device among the downlink frames stored in the shared buffer. The in-station apparatus according to claim 1, wherein   The downlink frame control signal transmission unit embeds identification information of the first slave station side device in a pause frame that controls a flow of the downlink frame between the higher-level device and the slave station side device. 5. The intra-station device according to claim 1, wherein a downlink frame stop signal is generated.   6. The intra-station apparatus according to claim 2, wherein the downlink frame control signal transmission unit generates the frame resumption signal by setting a predetermined value in a pause time region of the pause frame. . A layer 2 switch having a shared buffer for receiving downlink frames transmitted from a higher-level device to a plurality of slave station-side devices and storing the downlink frames, and a master station side receiving the downlink frames from the layer 2 switch A communication system comprising a device and a plurality of slave station side devices that receive the downlink frame from the master station side device,
The master station side device
When the first slave station side device among the plurality of slave station side devices is in a sleep state in which power supply to some devices in the first slave station side device is stopped, the first slave station side device A frame stop signal for stopping transmission of a downlink frame addressed to the station side device is transmitted to the layer 2 switch;
The layer 2 switch
A communication system characterized by stopping transmission of a downlink frame addressed to the first slave station side device among the downlink frames stored in the shared buffer when the frame stop signal is received. A master station side device that receives a downstream frame from a layer 2 switch connected to the upper side and transmits it to a plurality of slave station side devices connected to the lower side,
A sleep determination unit that determines whether a first slave station side device among the plurality of slave station side devices is in a sleep state in which power supply to some devices in the first slave station side device is stopped; ,
A frame control signal transmission unit that generates and transmits a frame stop signal for stopping transmission of a downlink frame addressed to the first slave station side device when the first slave station side device is in the sleep state; A master station side device characterized by that. A layer 2 switch including a shared buffer that is connected to an upper side of a master station side device and stores downlink frames addressed to a plurality of slave station side devices connected to a lower side of the master station side device;
When receiving the frame control signal transmitted from the master station side device, control is performed to stop transmission of a downlink frame addressed to the first slave station side device among the downlink frames stored in the shared buffer. A layer 2 switch comprising a downstream frame control unit.

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