JP2009130623A - Optical subscriber line terminal station device, communication system including same, and packet transmitting method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical subscriber line terminal station device capable of preventing a packet from being discarded in ONU (Optical Network Unit) and efficiently using the down band of PON (Passive Optical Network). <P>SOLUTION: A transmission packet amount correcting part 18 corrects a transmission packet amount to ONU to a buffer residual amount when an ONU buffer residual amount updated by a buffer residual amount updating part 16 is smaller than a transmission packet amount determined by a scheduling processing part 17. A transmission sequence changing part 19 changes a transmission sequence to a plurality of ONUs so as to set values (amount of buffer allowance) obtained by subtracting the transmission packet amount determined by the scheduling processing part 17 from the ONU buffer residual amount updated by the buffer residual amount updating part 16 in a descending order. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a PON (Passive Optical Network) that is a medium-shared communication in which a plurality of home-side devices share a medium and transmit data, and in particular, an EPON that transmits data as an Ethernet (registered trademark) frame. The present invention relates to an optical subscriber line terminal apparatus (OLT (Optical Line Terminal)) capable of efficiently using a downstream band in (Ethernet (registered trademark) PON), a communication system including the same, and a packet transmission method.

  In recent years, networks capable of broadband access are becoming widespread, and among them, GE-PON (Gigabit Ethernet-PON) capable of high-speed communication attracts attention. Since GE-PON is a medium-shared communication in which a plurality of home devices share a medium and transmit data, it is important to efficiently use the PON band. As a technique related to efficient use of the downstream PON band, there is an invention disclosed in Patent Document 1 below.

  The optical subscriber line termination device (ONU (Optical Network Unit)) disclosed in Patent Document 1 controls for notification to the OLT (queue overflow alarm) when the queue length exceeds a set threshold value H. Generate a frame and send it to the OLT. When the OLT receives this queue overflow alarm, the OLT restricts frame transfer to the ONU.

When the queue length falls below the set threshold value L, a control frame for notification to the OLT (queue overflow alarm clear) is generated and transmitted to the OLT. When the OLT receives this queue overflow alarm clear, the OLT resumes the frame transfer to the ONU.
JP 2007-49376 A

  In the ONU disclosed in Patent Document 1 described above, when the queue length exceeds a threshold value, that is, when the remaining amount of the ONU buffer is low, a control frame is transmitted to the OLT, and frame transmission from the OLT is performed. It is to stop. For this reason, it takes a certain amount of time until the OLT stops frame transmission after the ONU buffer remaining capacity is low.

  For example, when a control frame is transmitted to an OLT located 20 km away from the ONU, it takes about 10 μs. If a frame is transmitted from the OLT to the ONU at 10 Gbps, IFG (Inter-Frame Gaps) and PA () between the ONU transmitting a control frame to the OLT and the OLT stopping frame transmission. About 12.5 KBytes (= 10000 / 6.4 × 8) including Pre-Amble) is transmitted to the ONU. If the ONU cannot store this data in the buffer, the frame is discarded. Therefore, there is a problem that the downstream band may not be used efficiently.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to prevent packets from being discarded by an optical subscriber line terminating device and to efficiently use the PON downstream band. It is an object of the present invention to provide a possible optical subscriber line terminal equipment, a communication system including the same, and a packet transmission method.

  According to one aspect of the present invention, an optical subscriber line terminal device that transmits packets received from a higher-level network to a plurality of optical subscriber line termination devices, and should be transmitted to the plurality of optical subscriber line termination devices Storage means for storing packets, scheduling means for scheduling packets stored in the storage means, receiving means for receiving remaining buffer capacity from a plurality of optical subscriber line terminating devices, and remaining buffer received by the receiving means And control means for controlling the amount of transmission packets and / or the order of transmission to the plurality of optical subscriber line termination devices determined by the scheduling means according to the quantity.

  Therefore, it is possible to prevent packets from being discarded by the optical subscriber line terminating device.

  Preferably, the control means corrects the amount of packets transmitted to the plurality of optical subscriber line termination devices determined by the scheduling means in accordance with the remaining buffer capacity received by the receiving means, and receives by the receiving means. And changing means for changing the order of transmission to the plurality of optical subscriber line termination devices determined by the scheduling means in accordance with the remaining buffer capacity and the amount of transmission packets determined by the scheduling means.

  Therefore, it is possible to promote the recovery of the remaining buffer capacity of the optical subscriber line terminating device, where the remaining buffer capacity is reduced.

  More preferably, the correction means corrects the amount of transmission packets to the optical subscriber line terminating apparatus to the buffer remaining amount when the remaining buffer capacity received by the receiving means is smaller than the transmission packet amount determined by the scheduling means. To do.

  Therefore, it is possible to prevent packets exceeding the remaining buffer capacity from being transmitted.

  More preferably, the changing means is a transmission order to the plurality of optical subscriber line terminating devices so that a value obtained by subtracting the amount of transmission packets determined by the scheduling means from the remaining amount of the buffer received by the receiving means is in descending order. To change.

  Accordingly, it is possible to more appropriately prompt the recovery of the remaining buffer capacity of the optical subscriber line terminating device in which the remaining buffer capacity is reduced.

  More preferably, the control means further has a value obtained by subtracting a bandwidth remaining due to the correction of the transmission packet amount by the correction means, and a value obtained by subtracting the transmission packet amount determined by the scheduling means from the remaining amount of the buffer received by the reception means from a predetermined value. Allocating means for allocating to a larger optical subscriber line terminating device.

Therefore, the PON downstream band can be used more efficiently.
Preferably, the receiving means receives a report frame or a management frame including a remaining buffer capacity from a plurality of optical subscriber line terminating devices.

  Therefore, it is not necessary to generate a dedicated control frame for notifying the remaining buffer capacity, and an increase in upstream traffic can be prevented.

  According to another aspect of the present invention, an optical subscriber line terminal device that receives a frame from an upper network, and a plurality of optical signals that receive a frame transmitted from the optical subscriber line terminal device and transmit it to a home network A communication system including a subscriber line termination device, wherein an optical subscriber line terminal device stores a packet to be transmitted to a plurality of optical subscriber line termination devices, and is stored in the storage means Scheduling means for scheduling packets, receiving means for receiving the remaining buffer capacity from a plurality of optical subscriber line terminating devices, and a plurality of optical signals determined by the scheduling means in accordance with the remaining buffer capacity received by the receiving means Control means for controlling the amount of transmission packets and / or the order of transmission to the subscriber line terminator, each of the optical subscriber line terminators being an optical subscriber line Comprising a buffer means for storing packets received from the station apparatus, and transmission means for transmitting the buffer remaining capacity of the buffer means to the optical line termination.

  According to still another aspect of the present invention, there is provided a packet transmission method for an optical subscriber line terminal apparatus that transmits a packet received from an upper network to a plurality of optical subscriber line termination apparatuses, the plurality of accumulated The step of scheduling packets to be transmitted to the optical subscriber line terminator, the step of receiving remaining buffer capacity from a plurality of optical subscriber line terminators, and the received buffer remaining capacity are determined by scheduling. A step of changing a transmission packet amount and / or transmission order to the plurality of optical subscriber line termination devices, and a packet to the plurality of optical subscriber line termination devices according to the changed transmission packet amount and / or transmission order. Transmitting.

  According to an aspect of the present invention, the control means determines the amount of transmission packets and / or the order of transmission to the plurality of optical subscriber line termination devices determined by the scheduling means in accordance with the remaining buffer capacity received by the receiving means. Therefore, it is possible to prevent the packet from being discarded by the optical subscriber line terminating device.

  FIG. 1 is a block diagram showing an overall configuration of a communication system according to an embodiment of the present invention. This communication system includes an OLT 1 that is a station-side device and a plurality of ONU # 1 to ONU # N (2-1 to 2-N) that are home-side devices. The OLT 1 and the ONU # 1 to ONU # N (2-1 to 2-N) are connected by the PON.

  The OLT 1 is connected to a wide area network (hereinafter referred to as an upper network) such as the Internet. Moreover, ONU # 1 to ONU # N (2-1 to 2-N) are connected to a terminal via a home network such as a LAN (Local Area Network).

  The OLT 1 can receive the downstream frame at 10 Gbps via the upper network, and can transmit the downstream frame to any of the ONU # 1 to ONU # N (2-1 to 2-N) at the same speed. It is. Moreover, ONU # 1 to ONU # N (2-1 to 2-N) can relay a downstream frame via a home network at 10/100/1000 Mbps.

  FIG. 2 is a block diagram showing a schematic configuration of the OLT 1 in the embodiment of the present invention. The OLT 1 includes an SNI (Service Network Interface) downlink receiving unit 11 that receives downlink frames from an upper network, a buffer 12 that accumulates frames received by the SNI downlink receiving unit 11, and ONU # 1 to ONU # N ( PON downlink transmission unit 13 that transmits downlink frames to 2-1 to 2-N) and a PON uplink reception unit that receives uplink frames from ONU # 1 to ONU # N (2-1 to 2-N) 14, a frame distribution processing unit 15 that distributes frames received by the PON uplink reception unit 14, and ONU # 1 to ONU # N (2-1 to 2-2) based on the control frame distributed by the frame distribution processing unit 15. N) a buffer remaining amount update unit 16 for updating the buffer remaining amount, and a frame for scheduling downlink frames for each ONU. The scheduling processing unit 17, the transmission packet amount correction unit 18 that corrects the transmission amount of packets addressed to each ONU determined by the scheduling processing unit 17 (hereinafter referred to as transmission packet amount), and the scheduling processing unit 17 A transmission order changing unit 19 that changes the transmission order of the determined packets, and an SNI upstream transmission unit 20 that transmits the upstream frame distributed by the frame distribution processing unit 15 to the upper network are included.

  The SNI downlink reception unit 11 receives a downlink frame via an upper network, distributes the received frame to each FIFO (First In First Out) in the buffer 12 according to the destination, and stores the packet.

  The buffer 12 includes ONU 1 FIFO to ONU N FIFO (21-1 to 21-N) in which packets addressed to each ONU are sorted and accumulated.

  The scheduling processing unit 17 refers to the packet accumulation amount of each FIFO in the buffer 12 and sequentially selects the FIFO by the round robin method among the FIFOs in which the packets to be transmitted are accumulated, and the transmission packet amount addressed to each ONU And determine the transmission order. Note that a conventional scheduling method is used as the downlink frame scheduling method itself in the present embodiment. For details of the scheduling method, refer to Japanese Patent Application Laid-Open Nos. 2004-343734 and 2007-49376 filed by the present applicant.

  The PON downlink transmission unit 13 converts the packet output from the buffer 12 from an electrical signal to an optical signal and transmits the packet to the ONU # 1 to ONU # N (2-1 to 2-N).

  The PON upstream receiving unit 14 receives an upstream frame by converting an optical signal from the ONU # 1 to ONU #N (2-1 to 2 -N) into an electrical signal, and transfers the upstream frame to the frame distribution processing unit 15.

  The frame distribution processing unit 15 determines the type of the frame received from the PON upstream receiving unit 14, transfers a data frame to be transmitted via the upper network to the SNI upstream transmitting unit 20, and includes the remaining amount of the ONU buffer. The control frame is transferred to the buffer remaining amount update unit 16.

  The SNI upstream transmission unit 20 transmits the data frame transferred from the frame distribution processing unit 15 via the upper network.

  The buffer remaining amount update unit 16 extracts the ONU buffer remaining amount included in the control frame received from the frame distribution processing unit 15 and updates the buffer remaining amount of each ONU. Note that the buffer remaining amount update unit 16 has a table for storing the buffer remaining amount in each ONU, and according to the buffer remaining amount of the ONU included in the control frame received from the frame distribution processing unit 15. Update the corresponding part in the table.

  The transmission packet amount correction unit 18 corrects the transmission packet amount addressed to each ONU determined by the scheduling processing unit 17 and notifies the buffer 12 of the corrected transmission packet amount. A method of correcting the transmission packet amount will be described later.

  The transmission order changing unit 19 changes the packet transmission order to the ONU determined by the scheduling processing unit 17 and notifies the buffer 12 of the changed transmission order. A method for changing the transmission order will be described later.

  FIG. 3 is a flowchart for explaining the processing procedure of the remaining buffer capacity update unit 16. First, when the PON upstream receiving unit 14 receives a control frame (report frame) from one of the ONUs, the buffer remaining amount updating unit 16 receives the report frame via the frame distribution processing unit 15 and receives the ONU included in the report frame. The remaining amount of the buffer is extracted (S11).

  Next, the remaining buffer capacity update unit 16 updates the remaining buffer capacity by storing the extracted remaining buffer capacity in the corresponding portion of the internal table (S12). These processes are performed every time a report frame is received from the ONU.

  FIG. 4 is a flowchart for explaining processing procedures of the scheduling processing unit 17, the transmission packet amount correction unit 18, and the transmission order change unit 19. First, the scheduling processing unit 17 refers to the packet accumulation amount of each FIFO in the buffer 12 to perform scheduling of packets to be transmitted to each ONU, and determines a transmission packet amount and a transmission order corresponding to each ONU (S21). ).

  Next, the transmission packet amount correction unit 18 obtains the buffer remaining amount of the corresponding ONU from the table in the buffer remaining amount update unit 16 (S22), and the transmission packet amount whose buffer remaining amount is determined by the scheduling processing unit 17 It is determined whether or not this is the case (S23).

  If the remaining buffer capacity is equal to or greater than the transmission packet amount (S23, Yes), the process proceeds to step S25 as it is without correcting the transmission packet amount. If the buffer remaining amount is less than the transmission packet amount (S23, No), the transmission packet amount is corrected to the buffer remaining amount (S24), and the process proceeds to step S25.

  In step S25, it is determined whether or not the correction of the transmission packet amount for all ONUs has been completed. If there is an ONU whose transmission packet amount correction has not been completed (S25, No), the process returns to step S22 and the subsequent processing is repeated.

  When the correction of the transmission packet amount for all the ONUs is completed (S25, Yes), the band remaining due to the correction of the transmission packet amount is allocated to the ONU having a large buffer remaining amount (S26). Here, the ONU having a large remaining buffer capacity refers to an ONU in which the remaining buffer capacity is determined to be equal to or larger than the transmission packet amount in step S23 and the packets to be transmitted to the buffer 12 are accumulated.

  Further, an ONU having a buffer clearance amount, which will be described later, may be a predetermined threshold value, for example, an ONU having a large buffer remaining amount.

  When there are a plurality of ONUs with a large remaining buffer capacity (buffer clearance), bandwidths may be allocated in the order of ONUs with a large remaining buffer capacity (buffer clearance), and the amount of packets stored in the buffer 12 Bands may be allocated in the order of many ONUs. However, bandwidth allocation exceeding the remaining buffer capacity (buffer clearance) is not performed.

  Next, the transmission order changing unit 19 calculates the buffer clearance amount of each ONU from the transmission packet amount to each ONU determined by the scheduling processing unit 17 and the buffer remaining amount of each ONU, and the order in which the buffer clearance amount is large. The transmission order is changed so as to become (S27).

  FIG. 5 is a diagram for explaining a method for calculating the buffer clearance. FIG. 5 shows, as an example, a method for calculating the buffer clearance amount of ONU # 1 to ONU # 4 (2-1 to 2-4). It is assumed that the unit of the transmission packet amount and the buffer remaining amount is KByte, and the buffer clearance amount is calculated by the following equation.

Buffer clearance amount = (ONU buffer remaining amount) − (Transmission packet amount determined by the scheduling processing unit 17) (1)
In ONU # 1 (2-1), the transmission packet amount determined by the scheduling processing unit 17 is “80”, and the remaining buffer capacity is “130”, so that the buffer clearance amount is calculated as “50”. .

  Similarly, the buffer space of ONU # 2 (2-2) is “0”, the buffer space of ONU # 3 (2-3) is “−30”, and the buffer space of ONU # 4 (2-4) is The quantity is calculated as “−20”.

  At this time, the transmission order changing unit 19 changes the transmission order so that the order of ONU # 1, ONU # 2, ONU # 4, and ONU # 3 is large. In this way, the order of the ONUs with the least amount of space is left in order to wait for the remaining buffer capacity of the ONUs to recover. As a result, the possibility of the packet being discarded by the ONU can be reduced.

  In the calculation of the buffer clearance amount, instead of using the transmission packet amount determined by the scheduling processing unit 17, the transmission packet amount after allocating the surplus bandwidth in step S26 may be used.

  Finally, the PON downlink transmission unit 13 receives the packet output from the buffer 12 based on the transmission packet amount corrected by the transmission packet amount correction unit 18 and the transmission order changed by the transmission order change unit 19, and receives the ONU # 1 to ONU # N (2-1 to 2-N) are transmitted (S28). Then, the process returns to step 21 and the subsequent processing is repeated.

  FIG. 6 is a block diagram showing a schematic configuration of the ONU 2 in the embodiment of the present invention. The ONU 2 includes a PON downlink receiver 31 that receives a downlink frame from the OLT 1 and a UNI (User Network Interface) downlink transmitter 32 that transmits a data frame received by the PON downlink receiver 31 to a terminal via a home network. And a control frame processing unit 33 that generates a control frame including the remaining buffer capacity of the buffer memory 35, a UNI uplink receiving unit 34 that receives a data frame from a terminal via a home network, and a control frame processing unit 33. A buffer memory 35 for storing the received control frame and the data frame received by the UNI uplink receiving unit 34, and a PON uplink transmitting unit 36 for transmitting the frame stored in the buffer memory 35 within the band permitted by the OLT 1. Including.

  The control frame processing unit 33 periodically calculates the remaining buffer capacity of the buffer memory 35, generates a report frame (control frame) including the buffer remaining capacity, and accumulates it in the buffer memory 35. The PON upstream transmission unit 36 notifies the remaining amount of the buffer of the ONU 2 by transmitting the report frame accumulated in the buffer memory 35 to the OLT 1.

  This notification can also use the Reserved field of the MPCP REPORT frame specified by IEEE 802.3ah, or the Reserved of other management frames such as OAM (Operations, Administration and maintenance) specified by IEEE 802.3ah. It is also possible to use fields, Vendor extension fields, and the like. Since the MPCP REPORT frame is periodically transmitted from the ONU 2 to the OLT 1 (with a cycle of about several ms), a useless bandwidth is not used for notification, and the delay for notification is also minimized. It is possible to suppress it.

  As described above, according to the OLT 1 in the present embodiment, the transmission packet amount to the ONU is corrected in accordance with the remaining buffer capacity of the ONU, and the transmission order is changed so as to increase the buffer clearance amount. Therefore, it is possible to prevent a packet from being discarded by the ONU and to efficiently use the PON downstream band.

  In addition, since the band remaining due to the correction of the transmission packet amount is assigned to the ONU having a large remaining buffer capacity (buffer clearance), the PON downlink band can be used more efficiently.

  In the above description, the transmission packet amount and the transmission order determined by the transmission packet amount correction unit 18 and the transmission order change unit 19 are changed. However, the transmission packet corrected by the transmission packet amount correction unit 18 is changed. Only the amount may be changed, or only the transmission order determined by the transmission order changing unit 19 may be changed. Even when only one of them is changed, packets can be prevented from being discarded by the ONU, and the PON downstream band can be used efficiently.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

It is a block diagram which shows the whole structure of the communication system in embodiment of this invention. It is a block diagram which shows schematic structure of OLT1 in embodiment of this invention. 5 is a flowchart for explaining a processing procedure of a buffer remaining amount update unit 16; 10 is a flowchart for explaining processing procedures of a scheduling processing unit 17, a transmission packet amount correction unit 18, and a transmission order changing unit 19. It is a figure for demonstrating the calculation method of the buffer clearance amount. It is a block diagram which shows schematic structure of ONU2 in embodiment of this invention.

Explanation of symbols

  1 OLT, 2-1 to 2-N ONU, 11 SNI downlink reception unit, 12 buffer, 13 PON downlink transmission unit, 14 PON uplink reception unit, 15 frame distribution processing unit, 16 buffer remaining amount update unit, 17 scheduling processing unit , 18 Transmission packet amount correction unit, 19 Transmission order change unit, 20 SNI uplink transmission unit, 211-1 to 21-N FIFO, 31 PON downlink reception unit, 32 UNI downlink transmission unit, 33 Control frame processing unit, 34 UNI uplink Reception unit, 35 buffer memory, 36 PON upstream transmission unit.

Claims (8)

An optical subscriber line terminal device that transmits a packet received from an upper network to a plurality of optical subscriber line termination devices,
Storage means for storing packets to be transmitted to the plurality of optical subscriber line terminating devices;
Scheduling means for scheduling packets stored in the storage means;
Receiving means for receiving a remaining buffer capacity from the plurality of optical subscriber line terminating devices;
Control means for controlling the amount of transmission packets and / or the order of transmission to the plurality of optical subscriber line termination devices determined by the scheduling means in accordance with the remaining buffer capacity received by the receiving means. Subscriber line terminal equipment. The control means corrects a transmission packet amount to the plurality of optical subscriber line terminating devices determined by the scheduling means according to the remaining buffer capacity received by the receiving means;
Changing means for changing the order of transmission to the plurality of optical subscriber line termination units determined by the scheduling means according to the remaining buffer capacity received by the receiving means and the amount of transmission packets determined by the scheduling means The optical subscriber line terminal equipment according to claim 1, comprising:   The correction means corrects the transmission packet amount to the optical subscriber line terminating apparatus to the buffer remaining amount when the remaining buffer capacity received by the receiving means is smaller than the transmission packet amount determined by the scheduling means. The optical subscriber line terminal equipment according to claim 2.   The changing means is a transmission order to the plurality of optical subscriber line terminating devices such that a value obtained by subtracting the amount of transmission packets determined by the scheduling means from the remaining buffer capacity received by the receiving means is in the descending order. The optical subscriber line terminal equipment according to claim 2 or 3, wherein   The control means further has a value obtained by subtracting a transmission packet amount determined by the scheduling means from a remaining amount of the buffer received by the receiving means from a predetermined value as a band remaining due to the correction of the transmission packet quantity by the correction means. 5. The optical subscriber line terminal apparatus according to claim 2, further comprising an allocating means for allocating to a larger optical subscriber line terminating apparatus.   6. The optical subscriber line terminal apparatus according to claim 1, wherein the receiving unit receives a report frame or a management frame including a buffer remaining amount from the plurality of optical subscriber line terminating devices. An optical subscriber line terminal device that receives a frame from an upper network, and a plurality of optical subscriber line terminal devices that receive a frame transmitted from the optical subscriber line terminal device and transmit the frame to a home network A communication system,
The optical subscriber line terminal equipment stores storage means for storing packets to be transmitted to the plurality of optical subscriber line terminators;
Scheduling means for scheduling packets stored in the storage means;
Receiving means for receiving a remaining buffer capacity from the plurality of optical subscriber line terminating devices;
Control means for controlling the amount of transmission packets and / or the order of transmission to the plurality of optical subscriber line termination devices determined by the scheduling means in accordance with the remaining buffer capacity received by the receiving means,
Each of the optical subscriber line termination devices includes a buffer means for storing a packet received from the optical subscriber line terminal device;
And a transmission means for transmitting the remaining buffer capacity of the buffer means to the optical subscriber line terminal equipment. A packet transmission method for an optical subscriber line terminal apparatus for transmitting a packet received from an upper network to a plurality of optical subscriber line termination apparatuses,
Scheduling the packets to be transmitted to the stored optical subscriber line termination devices;
Receiving buffer remaining capacity from the plurality of optical subscriber line termination devices;
Changing a transmission packet amount and / or transmission order to the plurality of optical subscriber line termination devices determined by the scheduling according to the received buffer remaining capacity;
Transmitting a packet to the plurality of optical subscriber line terminating devices according to the changed transmission packet amount and / or transmission order.

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