JP5813539B2 - Station side device and PON system - Google Patents

Description

  The present invention relates to a station side device and a PON system.

  Conventionally, a passive optical network (PON) system mainly used in FTTH (Fiber To The Home) service is known as a subscriber optical fiber network system for subscriber homes such as ordinary homes. It has been. In this PON system, one optical fiber connected to a station side device (OLT: Optical Line Terminal) is branched by an optical branching circuit (optical splitter), and is divided into a plurality of subscriber side devices (ONU: Optical Network Unit). It is an optical transmission system that connects and shares a single optical fiber among a plurality of users (for example, see Patent Document 1).

  Here, in the PON section connecting the subscriber side apparatus and the station side apparatus, bandwidth control such as DBA (Dynamic Bandwidth Allocation) control is used in the PON interface (hereinafter referred to as “PIF”). Bandwidth control such as DBA control can dynamically transmit optically to each ONU for upstream bandwidth traffic (digital data such as voice, documents, images, etc. moving on the network) from the ONU to the station side device. This is a function for allocating bandwidth. By DBA control, bandwidth control in consideration of fairness among subscribers and congestion control for reducing congestion of data communication traffic due to optical transmission are performed.

  Conventionally, as a specific means of congestion control between two different devices, flow control is known. In the flow control, in order to prevent the receiving side process from catching up traffic in data communication, adjustments such as transmission stop and speed limit are performed according to the communication status.

JP 2007-142664 A

  However, conventional general flow control is performed according to port units or priority units, and DBA control is performed for each PON section. That is, for example, control in consideration of subscribers in a plurality of different PON sections is not sufficiently considered. For this reason, even when DBA control is normally performed for a plurality of subscriber side devices in one PON section at the time of output congestion from the station side device to the host network, a large amount of traffic is generated in other PON sections. As a result, fairness cannot be maintained as a result.

  Therefore, in view of the above circumstances, an object of the present invention is to provide means for performing DBA control that maintains fairness across a plurality of different PON sections.

  The station-side apparatus according to the first invention includes an aggregation switch unit, a management unit, a determination unit, a calculation unit, and a DBA control unit. The aggregation switch unit aggregates a flow of traffic indicating transmission data for each subscriber transmitted from a subscriber side device connected under each PON interface, and then outputs the traffic to a predetermined destination. The management unit centrally manages flows based on an identifier for identifying a flow for each subscriber-side device aggregated by the aggregation switch unit and a priority of the flow. The determination unit determines whether or not the output port from which the aggregation switch unit outputs the traffic is based on a flow that is managed by the management unit. When the determination unit determines that the congestion state is present, the calculation unit calculates a bandwidth limit value for making the distribution of the output bandwidth of the flow for each subscriber-side device fair. The DBA control unit performs DBA control, which is a bandwidth control method of the PON interface, across a plurality of different PON sections based on the bandwidth limit value calculated by the calculation unit.

  In a second aspect based on the first aspect, the calculation unit calculates a bandwidth limit value for making the distribution of the output bandwidth of the flow with the same priority between the subscriber side devices fair.

  In a third aspect based on the first or second aspect, the DBA control unit controls the output band by feeding back the band limit value to the DBA control.

  According to a fourth invention, in any one of the first to third inventions, the identifier includes an input port number of a traffic input destination, a MAC (Media Access Control) address of a subscriber side device, and a virtual network VLAN (Virtual Local Area Network) number for configuring the network. The aggregation switch unit identifies the traffic flow of each subscriber based on the identifier, and sets the priority based on a parameter associated with the importance of the traffic.

  In a fifth aspect based on the fourth aspect, the band management table is provided. The bandwidth management table manages bandwidth limit values associated with identifiers and priorities. The management unit centrally manages traffic flows based on the bandwidth management table.

  A PON system according to a sixth aspect of the invention comprises a subscriber side device connected to a user terminal and a station side device connecting a plurality of subscriber side devices via a PON line. The station side device includes an aggregation switch unit, a management unit, a determination unit, a calculation unit, and a DBA control unit. The aggregation switch unit aggregates a flow of traffic indicating transmission data for each subscriber transmitted from a subscriber side device connected under each PON interface, and then outputs the traffic to a predetermined destination. The management unit centrally manages flows based on an identifier for identifying a flow for each subscriber-side device aggregated by the aggregation switch unit and a priority of the flow. The determination unit determines whether or not the output port from which the aggregation switch unit outputs the traffic is based on a flow that is managed by the management unit. When the determination unit determines that the congestion state is present, the calculation unit calculates a bandwidth limit value for making the distribution of the output bandwidth of the flow for each subscriber-side device fair. The DBA control unit performs DBA control, which is a bandwidth control method of the PON interface, across a plurality of different PON sections based on the bandwidth limit value calculated by the calculation unit.

  In a seventh aspect based on the sixth aspect, the subscriber apparatus includes a transmission buffer memory and a transmission control unit. The transmission buffer memory temporarily records transmission data of the user terminal. The transmission control unit buffers the transmission data in the transmission buffer memory when the output port is congested, and transmits the transmission data being buffered to the station side device in accordance with the data transmission start timing.

  The present invention can provide means for performing DBA control that maintains fairness across a plurality of different PON sections.

1 is a diagram illustrating an example of a configuration of a PON system 100. FIG. It is a figure which shows an example of a structure of a subscriber side apparatus. 5 is a diagram illustrating an example of a bandwidth management table 16. FIG. It is a figure which shows an example of the DBA management table. 3 is a flowchart showing an example of the operation of the station side device 1. It is a figure which shows an example of a structure of the conventional PON system. It is a figure which shows an example of the internal structure of the subscriber side apparatus of 2nd Embodiment.

(First embodiment)
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. First, the configuration of the PON system 100 will be described.

<Configuration of PON system 100>
FIG. 1 is a diagram illustrating an example of the configuration of the PON system 100. The PON system 100 according to an embodiment of the present invention employs, for example, a GE-PON (Gigabit Ethernet (registered trademark) -Passive Optical Network) system. GE-PON is one of the high-speed optical access methods standardized as “IEEE 802.3ah” standard by the Institute of Electrical and Electronics Engineers (IEEE). The GE-PON is composed of a station side device (OLT) 1 and a home-installed subscriber side device (ONU). The subscriber side device is connected to a user terminal (hereinafter referred to as “terminal”) in the house. Furthermore, GE-PON is a system that bi-directional full-duplex transmission of Ethernet (registered trademark) data signals at a maximum of 1 gigabit (Gbit) / second.

  Therefore, the PON system 100 includes the station side apparatus 1 according to an embodiment of the present invention and a plurality of subscriber side apparatuses (ONUs 101 to 104). The plurality of subscriber-side devices (ONUs 101 to 104) are connected to the home terminals (T1 to T4), respectively.

  In FIG. 1, for ease of explanation, the number of subscriber-side devices (ONUs 101 to 104) and terminals (T1 to T4) is illustrated as four, but the number is not limited to these. , ONUs are installed for each subscriber's home. Moreover, you may connect to several terminal etc. from one ONU. The terminal may be, for example, a personal computer or an Internet Protocol telephone (IP telephone).

  Further, in the PON system 100, in the first PON section, one optical fiber connected to the station side apparatus 1 is branched by the optical branch circuit L1, and connected to a plurality of subscriber side apparatuses (ONUs 101 and 102). . Further, in the PON system 100, in the second PON section, one optical fiber connected to the station side apparatus 1 is branched by the optical branch circuit L2, and connected to a plurality of subscriber side apparatuses (ONUs 103 and 104). .

  Hereinafter, the configuration of the subscriber side apparatus and the station side apparatus 1 in the PON system 100 will be specifically described. For convenience of explanation, the terminals T1 to T4 and the ONUs 101 to 104 are assumed to be the same model as an example.

<Configuration of subscriber side device>
FIG. 2 is a diagram illustrating an example of the configuration of the subscriber side device. Since the ONUs 101 to 104 are the same model, the ONU 101 will be described as a representative. The ONU 101 includes a user side interface unit (hereinafter referred to as “user side IF unit”) 21, an ONU control unit 22, and an OLT side communication unit 23.

  The user-side IF unit 21 provides an interface for performing data communication with the terminal T1. The ONU control unit 22 controls the operation of the entire ONU 101. The ONU control unit 22 includes a frame transmission / reception unit 22a and a PON control unit 22b.

  The frame transmission / reception unit 22a receives the frame received from the station side device 1 output from the OLT side communication unit 23, and outputs it to the terminal T1 side via the user side IF unit 21. Conversely, the frame transmission / reception unit 22 a creates a frame based on transmission data input from the terminal T <b> 1 side via the user side IF unit 21 and outputs the frame to the OLT side communication unit 23. The frame transmitting / receiving unit 22a outputs a control frame to the PON control unit 22b among the frames received from the OLT side communication unit 23. Also, the frame transmission / reception unit 22a converts the received data into the received data and outputs the received data to the terminal T1 side only when it matches the LLID (Logical Link Identification) given from the station side device 1 side when the ONU is registered. That is, in GE-PON, the received frame is selected using the identifier LLID. The station apparatus 1 determines the value of the LLID when registering the ONU. The station side apparatus 1 determines LLID so that duplication does not occur among the ONUs under its control, and notifies each ONU 101-104.

  The PON control unit 22b analyzes the control frame and controls the GE-PON according to the analysis content.

  The OLT side communication unit 23 converts an optical signal received from the station side device 1 into an electrical signal, and converts an electrical signal transmitted to the station side device 1 into an optical signal. The OLT side communication unit 23 provides means for performing communication processing using, for example, WDM (Wavelength Division Multiplexing). WDM is a system in which a plurality of optical signals having different wavelengths are multiplexed and transmitted simultaneously on a single optical fiber.

<Configuration of station side device 1>
As shown in FIG. 1, the station-side device 1 includes a first PON interface (hereinafter referred to as “first PIF”) 11, a second PON interface (hereinafter referred to as “second PIF”) 12, and an aggregation switch unit (hereinafter referred to as “aggregation SW”). A transmission / reception unit 14, a control unit 15, a bandwidth management table 16, a DBA management table 17, a first DBA control unit 18, and a second DBA control unit 19.

  The first PIF 11 and the second PIF 12 are PON interface boards mounted on the station-side device 1 and can be connected to a maximum of 32 ONUs from one optical fiber cable via an optical branch circuit. For example, when 16 PON interface boards are mounted, the station side device 1 can be connected to a maximum of 512 units (32 units × 16 units) per station side device 1.

  The aggregation SW unit 13 is one of the relay devices of the network, and determines the destination of data (packet) in the data link layer (second layer) of the OSI (Open Systems Interconnection) reference model and transfers it. The aggregation SW unit 13 includes a switch unit (hereinafter referred to as “SW unit”) 13a and a buffer memory 13b. The SW unit 13a includes an input port P1, an input port P2, and an output port P3. The aggregation SW unit 13 aggregates the flow (traffic amount as the data flow rate) of traffic (transmission data and the like) from the first PIF 11 and the second PIF 12.

  Specifically, the SW unit 13a transmits the flow of traffic for each subscriber transmitted from the ONUs 101 and 102 connected under the first PIF 11 and the ONUs 103 and 104 connected under the second PIF 12 to the input port P1. , P2 is aggregated. In this case, the SW unit 13a temporarily records the traffic in the buffer memory 13b via the output port P3. The buffer memory 13b is a volatile memory, and is composed of, for example, a RAM (Random Access Memory) that can temporarily record 1 gigabyte of data. Further, the SW unit 13a outputs the traffic to the destination of the transmission destination.

  Further, for example, the aggregation SW unit 13 identifies the traffic flow of each subscriber based on three identifiers: (1) the input port number of the SW unit 13a, (2) the MAC address, and (3) the VLAN number. To do.

  The MAC address is a physical address uniquely assigned to hardware such as a network device on the network. In the figure, the MAC address is expressed as MAC.

  In this embodiment, for convenience of explanation, the MAC address of the terminal T1 is A, the MAC address of the terminal T2 is B, the MAC address of the terminal T3 is C, and the MAC address of the terminal T4 is D. Note that the MAC addresses A, B, C, and D are actually 48-bit (48 binary digits) numbers according to the standard, and the first 24 bits represent a vendor code (a code indicating a manufacturer), and the second half. 24 bits represent a vendor assigned code (product-specific code).

  The VLAN number is an identification number for configuring a virtual network. The virtual LAN is a function that groups terminals connected to a network, for example, independently of a physical LAN configuration.

  In this embodiment, for convenience of explanation, the terminals T1 to T4 when transmitting traffic with high priority are grouped by the VLAN number 100, and the terminals T1 to T4 when transmitting traffic with low priority are grouped with the VLAN number. Grouped by 200.

  In addition, the aggregation SW unit 13 determines the traffic of each subscriber based on VLAN # ID assigned to each input port (P1, P2) and CoS (Class of Service) value which is a kind of QoS (Quality of Service) technology. Set the flow priority.

  The QoS technology is a technology for performing communication by giving priority to specific traffic over other traffic, for example. The CoS value is a kind of parameter associated with the importance of traffic, and is used, for example, when giving priority to a layer 2 frame in a field in a so-called VLAN tag.

  Therefore, in the PON system 100, a plurality of logical paths (LL: Logical Link) can be set between the station side apparatus 1 and each ONU using the above identifiers, etc. Priority control can be performed for each logical path.

  The transmission / reception unit 14 transmits / receives data to / from an upper network (not shown) of the station side device 1. The control unit 15 is a processor that performs overall control of the station-side device 1. The control unit 15 also functions as a bandwidth management unit 15a, a congestion state determination unit 15b, and a bandwidth limit value calculation unit 15c.

  The bandwidth management unit 15a centrally manages the flow based on the identifier (input port number, MAC address, VLAN number of the SW unit 13a) and priority. Specifically, the bandwidth management unit 15 a centrally manages the traffic flow for each subscriber-side device based on the bandwidth management table 16.

  FIG. 3 is a diagram illustrating an example of the bandwidth management table 16. The bandwidth management table 16 is composed of five items, and centrally manages flows by managing bandwidth limit values associated with the above identifiers (input port number, MAC address, VLAN number) and priority. Thereby, in the 1st DBA control part 18 and the 2nd DBA control part 19, the information on the band limit value based on the flow managed centrally can be obtained easily. Details of the processing using the bandwidth management table 16 will be described in an operation example of the station side device 1 (FIG. 5).

  The congestion state determination unit 15b determines whether or not there is a congestion state of the output port (P3) from which the aggregation SW unit 13 outputs traffic, based on a flow that is centrally managed by the bandwidth management unit 15a. When the congestion state determination unit 15b determines that the congestion state determination unit 15b is in the congestion state, the bandwidth limit value calculation unit 15c calculates a bandwidth limit value for making the distribution of the output bandwidth of the flow with the same priority for each subscriber side device fair. calculate. Here, it is preferable that the bandwidth limit value calculation unit 15c calculates a bandwidth limit value for making the distribution of the output bandwidth of the flow with the same priority among the subscriber side devices fair. As a result, the distribution of the output bandwidth of the flow with the same priority becomes fair at the time of congestion. Therefore, in the station side device 1, the flow from the subscriber side device has the same priority over a plurality of different PON sections. Can be fair.

  The first DBA control unit 18 performs DBA control of the first PIF 11 based on the bandwidth limit value calculated for each priority by the bandwidth limit value calculation unit 15c. Similarly, the second DBA control unit 19 also performs DBA control of the second PIF 12 based on the bandwidth limit value.

  Here, the first DBA control unit 18 and the second DBA control unit 19 perform DBA control by receiving an instruction to feed back the band limit value to the DBA control from the band management unit 15a. At this time, the first DBA control unit 18 and the second DBA control unit 19 perform DBA control based on the DBA management table 17. That is, the first DBA control unit 18 and the second DBA control unit 19 control the output band by feeding back the band limit value to the DBA control. Thereby, the 1st DBA control part 18 and the 2nd DBA control part 19 can perform band control in consideration of fairness over a plurality of different PON sections.

  FIG. 4 is a diagram illustrating an example of the DBA management table 17. The first DBA control unit 18 and the second DBA control unit 19 manage the DBA management table 17 to be used based on the bandwidth management table 16.

  FIG. 4A shows a DBA management table 17 used for DBA control of the subscriber-side apparatus ONU 101 connected to the terminal T1 and the subscriber-side apparatus ONU 102 connected to the terminal T2. FIG. 4B shows a DBA management table 17 used for DBA control of the subscriber-side apparatus ONU 103 connected to the terminal T3 and the subscriber-side apparatus ONU 104 connected to the terminal T4.

  The DBA management table 17 is composed of five items. Specifically, the DBA management table 17 includes items of MAC address, VLAN number, priority, LLID, and DBA setting information. Details of processing using the DBA management table 17 will be described in an operation example of the station side device 1 (FIG. 5).

<Operation of station side device 1>
Next, an example of the operation of the station side device 1 will be described. FIG. 5 is a flowchart showing an example of the operation of the station side device 1. When the station side apparatus 1 receives an instruction to start the apparatus when the power is turned on (power is turned on), the aggregation SW unit 13 starts a traffic flow identification process for each subscriber. Specifically, the aggregation SW unit 13 analyzes the traffic frame (packet) received by the SW unit 13a, and determines the traffic flow of each subscriber from the input port number, MAC address, and VLAN number of the SW unit 13a. Identify. Then, the aggregation SW unit 13 sets the priority of the traffic flow of each subscriber.

  Furthermore, the bandwidth management unit 15a appropriately sets the bandwidth limit value of the bandwidth management table 16 according to the traffic flow of each subscriber. In this embodiment, optical transmission is performed by dividing into high priority traffic (for example, voice data) and low priority traffic (for example, digital data such as documents and images). In order to make the explanation easy to understand, it is assumed that the high-priority traffic of 10 Mbps (bits per second) at the maximum and the low-priority traffic of 1000 Mbps at the maximum are transmitted from the terminals T1 and T2. In addition, high-priority traffic of 10 Mbps at maximum is transmitted from the terminals T3 and T4. In addition, it is assumed that low priority traffic with a maximum of 980 Mbps is transmitted from the terminal T3. Further, it is assumed that low priority traffic is not transmitted from the terminal T4.

  On the other hand, the control part 15 starts the process of the flowchart shown in FIG.

  Step S101: The congestion state determination unit 15b of the control unit 15 checks the congestion state of the output port P3. Specifically, the congestion state determination unit 15b statistically measures the flow of traffic passing through the output port P3 with a counter or the like. The congestion state determination unit 15b determines that the state is a congestion state, for example, when there is no more free space in the buffer memory 13b. Note that the congestion state determination unit 15b may determine that the congestion state is present when there is no more free space in the buffer memory 13b and the control unit 15 discards part of the traffic accumulated in the buffer memory 13b.

  Step S102: When it is in a congestion state (step S102: Yes), the control unit 15 proceeds to the process of step S103. On the other hand, when it is not a congestion state (step S102: No), the control part 15 transfers to the process of step S105 mentioned later.

  Step S103: The bandwidth limit value calculation unit 15c of the control unit 15 performs a bandwidth limit value calculation process. Here, in the station side apparatus 1, since it is preferable to transmit high priority traffic to a high-order network, suppose that it does not carry out a band limitation. In the bandwidth management table 16 of FIG. 3, the blank bandwidth limit value corresponding to the priority (high) means that bandwidth limitation is not performed.

  Accordingly, the bandwidth limit value calculation unit 15c performs a bandwidth limit value calculation process for low priority traffic having the same priority. In this case, the bandwidth limit value calculation unit 15c calculates the bandwidth limit value so that a maximum of 1 gigabyte of traffic is output from the output port via the buffer memory 13b. This is because the first DBA control unit 18 and the second DBA control unit 19 perform bandwidth control and congestion control considering the priority and fairness among the subscribers. If the output traffic is kept so as not to exceed the capacity of the buffer memory 13b, congestion will not occur.

  Specifically, the bandwidth limit value calculation unit 15c is configured so that the high-priority traffic flows of the subscriber side devices (ONUs 101 to 104) are each set to 10 Mbps (the output bandwidth is equivalent to 40 Mbps). The bandwidth limit value is calculated so that the low-priority traffic flows of the subscriber side devices (ONUs 101 to 104) are fair. However, since there is no low-priority traffic for the ONU 104, in this case, the bandwidth limit value calculation unit 15c results in a fair flow of the low-priority traffic of the subscriber side devices (ONUs 101 to 103). The bandwidth limit value may be calculated so that Therefore, the bandwidth limit value calculation unit 15c calculates the bandwidth limit value as 320 Mbps (960 Mbps / 3 equally) because it is sufficient to allocate 960 Mbps (output bandwidth) equally.

  As a result, the bandwidth management unit 15a of the control unit 15 sets the bandwidth limit values in the bandwidth limit value fields corresponding to the priority (low) in the bandwidth management table 16 of FIG.

  Specifically, the bandwidth management unit 15a determines the bandwidth limit value of the ONU 101 connected to the terminal T1 specified by the input port number (P1), the MAC address (A), the VLAN number (200), and the priority (low). Is set to 320 Mbps. Further, the bandwidth management unit 15a sets the bandwidth limit value of the ONU 102 connected to the terminal T2 specified by the input port number (P1), the MAC address (B), the VLAN number (200), and the priority (low) to 320 Mbps. Set.

  Further, the bandwidth management unit 15a sets the bandwidth limit value of the ONU 103 connected to the terminal T3 specified by the input port number (P2), the MAC address (C), the VLAN number (200), and the priority (low) to 320 Mbps. Set. Note that the bandwidth management unit 15a does not send traffic for the ONU 104 connected to the terminal T4 identified by the input port number (P2), MAC address (D), VLAN number (200), and priority (low) at this time. Since it does not exist, the bandwidth limit value is set to 0 Mbps.

  When the setting of the bandwidth limit value by the bandwidth management unit 15a is completed, the control unit 15 proceeds to the process of step S104.

  Step S104: The bandwidth management unit 15a instructs the first DBA control unit 18 and the second DBA control unit 19 to perform DBA control processing based on the bandwidth limit value. Specifically, the bandwidth management unit 15a notifies the first DBA control unit 18 and the second DBA control unit 19 of the input port number, MAC address, VLAN number, and bandwidth limit value. That is, the bandwidth limit value (output value) calculated for each traffic flow of each subscriber is used as the input value together with the input port number, MAC address, and VLAN number associated with the bandwidth limit value as the first DBA. This is fed back to the control unit 18 and the second DBA control unit 19.

  The first DBA control unit 18 and the second DBA control unit 19 specify a logical link (LLID) in which a traffic flow is accommodated based on the MAC address and the VLAN number. Then, the first DBA controller 18 and the second DBA controller 19 change the DBA setting information for the corresponding logical link in the DBA management table 17 to the bandwidth limit value fed back. In this case, the first DBA control unit 18 changes the bandwidth limit value fed back to the bandwidth limit value column of the DBA management table 17 in FIG. Further, the second DBA control unit 19 changes the bandwidth limit value fed back to the bandwidth limit value column of the DBA management table 17 in FIG. The DBA management table 17 shown in FIGS. 4A and 4B exemplifies a state after changing the bandwidth limit value.

  Next, the first DBA control unit 18 performs known DBA control on the first PIF 11 based on the changed band limit value. Further, the second DBA control unit 19 performs known DBA control on the second PIF 12 based on the changed band limit value. By performing these feedback control operations, in this embodiment, it is possible to realize bandwidth control and congestion control in consideration of priority and fairness among subscribers accommodated in different PON interfaces. And the control part 15 transfers to the process of step S105.

  Step S105: The control unit 15 determines whether or not the DBA control process based on the bandwidth limit value is being performed. When the DBA control process is not being performed (step S105: No), the control unit 15 returns to the process of step S101. That is, the control unit 15 does not need to perform the DBA control process based on the bandwidth limit value if the process of step S102 is not in a congestion state. Therefore, the control unit 15 repeatedly executes the processes of steps S101, S102, and S105 until a congestion state occurs.

  On the other hand, when the DBA control process is being performed (step S105: Yes), the control unit 15 proceeds to the process of step S106.

  Step S106: The control unit 15 checks whether or not the flow of the input traffic has changed below a threshold value. If the input traffic flow is not less than or equal to the threshold (step S106: No), the control unit 15 returns to the process of step S101. In this case, since the congestion state is avoided by the DBA control process based on the bandwidth limit value, the control unit 15 repeatedly executes the processes of steps S101, S102, S105, and S106. The threshold value is, for example, the capacity of the buffer memory 13b.

  On the other hand, when the flow of the input traffic is equal to or less than the threshold (step S106: Yes), the control unit 15 proceeds to the process of step S107.

  Step S107: The control unit 15 performs a band limit value release process. The reason why the bandwidth limit value release processing is performed is that when the flow of input traffic is equal to or less than the threshold value, the output port P3 is not congested even if DBA control processing based on the bandwidth limit value is no longer performed. Therefore, the bandwidth management unit 15a cancels the bandwidth limit value in the bandwidth limit value column corresponding to the priority (low) in the bandwidth management table 16 shown in FIG. Further, the first DBA control unit 18 and the second DBA control unit 19 respectively leave the DBA setting information column of the DBA management table 17 shown in FIG. 4 blank. Then, the first DBA control unit 18 and the second DBA control unit 19 perform DBA control without using a band limit value.

  And the control part 15 returns to the process of step S101 again. Thereafter, when the flow of input traffic increases again and a congestion state occurs, the control unit 15 proceeds to the process of step S103, and performs the bandwidth limit value calculation process again. Further, the control unit 15 proceeds to the process of step S104 and performs the DBA control process based on the bandwidth limit value again.

  In this way, in this embodiment, during congestion, each PON interface (first PIF11, second PIF12) performs DBA control processing based on the bandwidth limit value, so that subscribers accommodated in different PON interfaces Bandwidth control and the like can be performed.

  Next, using a comparative example, the difference between the DBA control process based on the bandwidth limit value of the present embodiment and the conventional DBA control process will be clarified.

  FIG. 6 is a diagram illustrating an example of the configuration of a conventional PON system 200. For convenience of explanation, in the PON system 200, the functions of the bandwidth management unit 15a, the congestion state determination unit 15b, and the bandwidth limit value calculation unit 15c are stopped from the PON system 100 illustrated in FIG. Further, the bandwidth management table 16 and the DBA management table 17 are not used. Therefore, in FIG. 6, the bandwidth management unit 15a, the congestion state determination unit 15b, the bandwidth limit value calculation unit 15c, the bandwidth management table 16, and the DBA management table 17 are not illustrated.

  In the PON system 200, DBA control processing is not comprehensively performed across a plurality of different PON sections. Specifically, the terminals T1 and T2 transmit high-priority traffic with a maximum of 10 Mbps and low-priority traffic with a maximum of 1000 Mbps as in FIG. In this case, for example, in the PON section connecting the subscriber side devices (ONUs 101 and 102) and the station side device 1, a high priority of 10 Mbps from each of the subscriber side devices (ONUs 101 and 102) is obtained by the conventional DBA control processing. Traffic, 490 Mbps low priority traffic (1 Gbps in total) is generated.

  Also, from the terminals T3 and T4, as in FIG. 1, high-priority traffic with a maximum of 10 Mbps is transmitted. In addition, it is assumed that low priority traffic with a maximum of 980 Mbps is transmitted from the terminal T3. Further, it is assumed that low priority traffic is not transmitted from the terminal T4.

  In this case, in the PON system 200, for example, in the PON section connecting the subscriber side devices (ONUs 103 and 104) and the station side device 1, from the respective subscriber side devices (ONUs 103 and 104) by the conventional DBA control processing. High priority traffic of 10 Mbps is generated, and low priority traffic of 980 Mbps (total 1 Gbps) is generated from the ONU 103.

  As a result, the aggregation SW unit 13 calculates a bandwidth limit value for making the output bandwidth distribution fair in each PON section. Then, the transmission / reception unit 14 outputs a total of 1 Gbps traffic. The breakdown is as follows: high-priority traffic of 10 Mbps and low-priority traffic of 240 Mbps with respect to the output of traffic from the terminal T1 and traffic from the terminal T2. The traffic from the terminal T3 is high priority traffic of 10 Mbps and low priority traffic of 480 Mbps. Further, the traffic from the terminal T4 is a high priority traffic of 10 Mbps.

  Therefore, in the conventional PON system 200, 240 Mbps low priority traffic and 480 Mbps low priority traffic are output at the time of congestion. Therefore, as shown in this example, the low priority accommodated in different PON sections is output. The fairness of the priority traffic will not be maintained.

  On the other hand, in the PON system 100 according to the present embodiment, the DBA control process is performed over a plurality of different PON sections at the time of congestion. Therefore, for example, as shown in FIG. The priority traffic is 320 Mbps, and the fairness of the traffic is maintained.

  As described above, according to the first embodiment, it is possible to provide means capable of performing DBA control that maintains fairness across a plurality of different PON sections.

(Second Embodiment)
Next, a second embodiment will be described. Here, in 1st Embodiment and 2nd Embodiment, the same code | symbol is attached | subjected about the same component, description is abbreviate | omitted, and a difference is mainly demonstrated.

  The PON system 100 of the second embodiment is characterized in that each subscriber-side device has a transmission buffer memory for bandwidth control and a function for controlling data communication using the transmission buffer memory.

  FIG. 7 is a diagram illustrating an example of an internal configuration of the subscriber side device according to the second embodiment. In FIG. 1, the subscriber side devices (ONUs 101 to 104) of the first embodiment are replaced with the subscriber side devices (ONUs 101 to 104) of the second embodiment. In order to make the description easy to understand, the subscriber side devices (ONUs 101 to 104) of the second embodiment are assumed to be the same model, and the ONU 101 will be described as a representative.

  The ONU 101 of the second embodiment further includes a transmission buffer memory 22c and a transmission control unit 221b as compared to the ONU 101 of the first embodiment.

  The transmission buffer memory 22c is a buffer memory for the purpose of lowering the bandwidth control to the PON section in the DBA control.

  The transmission control unit 221b buffers transmission data in the transmission buffer memory when the output port P3 of the station side device 1 is congested. In this case, the transmission control unit 221b receives a control frame indicating an instruction to buffer transmission data from the station-side device 1, and temporarily records the transmission data in the transmission buffer memory 22c. Further, the transmission control unit 221b transmits the buffered transmission data to the station side device 1 in accordance with the start timing of data transmission. In this case, the transmission control unit 221b receives a control frame indicating the start of data transmission from the station side device 1, and transmits the transmission data being buffered to the station side device 1.

  More specifically, the transmission control unit 221b transmits, for example, buffered transmission data to the station apparatus 1 by receiving a control frame (transmission permission notification) called “GATE frame” from the station apparatus 1. To do. This GATE frame is composed of data transmission start time and transmission duration instruction information for the ONU. When the output port P3 of the station side device 1 is not congested, the transmission control unit 221b transmits the transmission data to the station side device 1 without buffering it in the transmission buffer memory.

  Next, an operation example of the subscriber side devices (ONUs 101 to 104) and the station side device 1 in the PON system 100 of the second embodiment will be described. The operation of the station side device 1 is basically the same as the processing of the flowchart (FIG. 5) described in the first embodiment.

  However, when the output port (P3) of the SW unit 13a is congested, the first DBA control unit 18 and the second DBA control unit 19 limit the output bandwidth for each subscriber side device (ONUs 101 to 104) by the DBA control process. Thereby, the transmission control part 221b performs buffering of the transmission data which are not output for every subscriber side apparatus (ONU101-104).

  Therefore, according to the second embodiment, the buffer memory 22c on the subscriber side device (ONU 101 to 104) side and the buffer memory 13b on the station side device 1 side can be effectively used. The buffer capacity of the memory 13b can be reduced.

<Supplementary explanation of the embodiment>
(1) In the above embodiment, the GE-PON system is adopted as the PON system 100. However, the PON system is not limited to the GE-PON system, and any other PON system is adopted as long as it is a PON system used in the FTTH service. You may do it.

  (2) In the above embodiment, the number of input ports of the SW unit 13a has been described as two in order to make the description easy to understand. However, the number of input ports is not limited to this number. Moreover, although the number of output ports of the SW unit 13a has been described as one, the number of output ports is not limited to this number.

  (3) In the above embodiment, in order to make the explanation easy to understand, the priority level is set to two levels of high and low, but the priority level may be set in multiple levels.

DESCRIPTION OF SYMBOLS 1 ... Station side apparatus, 13 ... Aggregation SW part, 15a ... Band management part, 15b ... Congestion state determination part, 15c ... Band limit value calculation part, 18 ... 1st DBA control , 19 ... second DBA controller, 100 ... PON system

Claims (6)

After aggregating a flow of frames including transmission data for each user terminal connected to the subscriber side device transmitted from a subscriber side device connected under each PON (Passive Optical Network) interface, An aggregation switch that outputs frames to a predetermined destination; and
Based on the priority identifier and the flow identifying a pre Symbol flow, a management unit that centrally manages the flow of the subscriber unit each time the aggregation switch unit aggregated,
A determination unit that determines whether or not the output port from which the aggregation switch unit outputs the frame has a congestion state based on the flow that is managed by the management unit;
When the determination unit determines that the congestion state is present, an output band for the low-priority flow among the flows for each of the subscriber-side devices is equally distributed to the subscriber-side devices as a bandwidth limit value. A calculation unit;
A DBA control unit that performs DBA (Dynamic Bandwidth Assignment) control, which is a bandwidth control method of the PON interface, across a plurality of different PON sections based on the bandwidth limit value calculated by the calculation unit;
A station-side device comprising: In the station side apparatus of Claim 1,
The DBA control unit controls the output band by feeding back the band limit value to the DBA control . In the station side apparatus of Claim 1 or Claim 2,
The identifier includes an input port number of an input destination of the frame, a MAC (Media Access Control) address of the user terminal, and a VLAN (Virtual Local Area Network) number for configuring a virtual network,
The station side apparatus , wherein the aggregation switch unit sets the priority based on the identifier . In the station side apparatus of Claim 3 ,
A bandwidth management table for managing the bandwidth limit value associated with the identifier and the priority ,
The management unit, based on the bandwidth management table, a station-side apparatus, characterized in that centrally manages the flow of the subscriber unit per. In a PON system composed of a subscriber side device connected to a user terminal and a station side device connecting a plurality of the subscriber side devices via a PON line ,
The station side device
An aggregation switch unit that aggregates a flow of frames including transmission data for each of the user terminals transmitted from a subscriber-side device connected under each PON interface, and then outputs the frame to a predetermined destination;
Based on an identifier for identifying the flow and the priority of the flow, a management unit that centrally manages the flow for each of the subscriber side devices aggregated by the aggregation switch unit;
A determination unit that determines whether or not the output port from which the aggregation switch unit outputs the frame has a congestion state based on the flow that is managed by the management unit;
When the determination unit determines that the congestion state is present, an output band for the low-priority flow among the flows for each of the subscriber-side devices is equally distributed to the subscriber-side devices as a bandwidth limit value. A calculation unit;
A DBA control unit that performs DBA control as a bandwidth control method of the PON interface across a plurality of different PON sections based on the bandwidth limit value calculated by the calculation unit;
PON system, characterized in that the have a. In the PON system according to claim 5 ,
The subscriber side device is:
A transmission buffer memory for temporarily recording transmission data of the user terminal ;
Buffering the transmission data in the transmission buffer memory when the output port is congested, and transmitting the transmission data being buffered to the station side device according to the start timing of data transmission ; and
A PON system characterized by comprising:

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