JP2021002886A - Communication system, subscriber line termination device, and subscriber line end station device - Google Patents

Abstract

To utilize an allocated transmission band more efficiently.SOLUTION: In a communication system including a subscriber line termination device and a subscriber line end station device, the subscriber line termination device includes a queue of uplink data sent to the subscriber line end station device, and a congestion avoidance processing unit that discards uplink data from the queue, and the subscriber line end station device includes a transmission permission unit that permits transmission of uplink data using the allocation request amount declared by the subscriber line termination device, and the system further includes a permit adjustment unit that controls transmission permission such that the discrepancy between the amount of uplink data permitted for transmission at the time of transmission and the amount of uplink data in the queue does not become large.SELECTED DRAWING: Figure 1

Description

The present invention relates to a communication system, a subscriber line termination device, and a subscriber line end station device.

In a passive optical network (PON), a subscriber line terminal device (OLT: Optical Line Terminal) and a subscriber line terminal unit (ONU: Optical Network Unit) are combined with an optical distribution network (ODN). ) To communicate point-to-point or point-to-multipoint. Hereinafter, the direction from ONU to OLT is referred to as "upward". Hereinafter, the direction from the OLT to the ONU is referred to as "downward".

In a PON in which time division multiplexing (TDM) is used, a downlink signal is transmitted to an ONU housed in an OLT via an ODN. The OLT gives a downlink signal such as an ONU-ID, an Alloc-ID, or an LLID (Logical Link ID), which is an identifier indicating a destination. The ONU may discard the downlink signal to which the identifier that is not the destination is assigned.

The OLT uses time division multiplexing to receive uplink signals from a plurality of ONUs at different times. The OLT cannot correctly decode the uplink signals when the uplink signals that should arrive at different times arrive (collide) at the same time. Therefore, in PON using time division multiplexing, transmission of uplink signals is permitted according to the procedure of Dynamic Bandwidth Assignment (DBA). For dynamic bandwidth allocation, there is a method in which the ONU transmits a DBRu (Dynamic Bandwidth Report upstream) or the like indicating a band allocation request to the OLT, and the OLT transmits a GATE signal or the like indicating a transmission permission to the ONU.

As a method of avoiding the congestion of the uplink signal, transmission suppression to the user device by back pressure or the like, tail dropping such as EPD (Early Packet Discard) and PPD (partial packet detection) in the ONU or ONU priority queue are randomly discarded. There are AQM (Active Queue Management) such as RED (Random Early Discard) and WRED (Weighted RED). Tail Dropping is a congestion avoidance method in which when the priority queue or the like exceeds a predetermined length, the rear frame is dropped before being input to the priority queue or the like. AQM is a congestion avoidance method in which frames are discarded in advance before congestion occurs. Compared to Tail Dropping, AQM has a higher affinity with traffic congestion control that slows down traffic during congestion such as Transport Layer Transmission Control Protocol (TCP), and is effective.

Toshiyuki Iwata, Yasuhiko Nakanishi, Yoichi Maeda, Proposal of traffic control method for PON-type architecture access, IEICE Journal, Vol.J89-B, No.5, PP.705-719

However, in the congestion avoidance method of discarding frames, there is a problem that the ONU cannot fully utilize the allocated transmission band because the frames may be discarded after the band allocation request is made.

In view of the above circumstances, it is an object of the present invention to provide a technique capable of more efficiently utilizing the allocated transmission band.

One aspect of the present invention is a communication system including a subscriber line termination device and a subscriber line end station device, wherein the subscriber line termination device is a queue of uplink data transmitted to the subscriber line end station device. , The congestion avoidance processing unit that discards the uplink data from the queue, and the subscriber line end station device grants the transmission permission of the uplink data using the allocation request amount declared by the subscriber line termination device. A queue adjustment unit that is provided with a transmission permission unit to perform transmission and controls the congestion avoidance processing unit so that the difference between the amount of uplink data permitted to be transmitted at the time of transmission and the amount of uplink data of the queue does not become large, or a transmission permission unit at the time of transmission. The declaration adjustment unit that controls the allocation request amount so that the discrepancy between the upstream data amount of the queue and the uplink data amount of the queue does not become large, or the uplink data amount permitted to be transmitted at the time of transmission and the uplink data amount of the queue. It is a communication system characterized in that it further includes at least one of permission adjusting units for controlling transmission permission so that the divergence does not become large.

One aspect of the present invention is the above-mentioned communication system, and when the queue adjustment unit is provided, the queue adjustment unit uses the declared allocation request amount for uplink data transmission corresponding to the allocation request amount. During that time, the congestion avoidance processing unit suppresses the discarding of the uplink data.

One aspect of the present invention is the above-mentioned communication system, and when the queue adjustment unit is provided, the queue adjustment unit uses the declared allocation request amount for uplink data transmission corresponding to the allocation request amount. During that time, control is performed so that the uplink data is discarded up to the amount of data that exceeds the allocation request amount.

One aspect of the present invention is the above-mentioned communication system, and when the declaration adjustment unit is provided, the declaration adjustment unit is the data discarded by the congestion avoidance processing unit based on the amount of the discarded uplink data. The amount is calculated as a predicted disposal value, and the estimated disposal value is subtracted from the upstream data amount of the queue or the allocation request amount to control the allocation request amount.

One aspect of the present invention is the above-mentioned communication system, and when the permission adjustment unit is provided, the permission adjustment unit determines a difference between the allocation request amount and the uplink data amount received from the subscriber line termination device. The transmission permission amount calculated as the difference prediction value and allocated to the subscriber line termination device is controlled by using the result of subtracting the difference prediction value from the allocation request amount.

One aspect of the present invention is the above-mentioned communication system, and when the cue adjustment unit is provided, the cue adjustment unit sets parameters used for determining a condition for discarding the uplink data from the cue, and the cue adjustment unit is used. Controls the congestion avoidance processing unit.

One aspect of the present invention includes a queue of uplink data transmitted to the subscriber line end station device and a congestion avoidance processing unit that discards the uplink data from the queue, and the amount of uplink data permitted to be transmitted at the time of transmission. The queue adjustment unit that controls the congestion avoidance processing unit so that the discrepancy between the data and the uplink data amount of the queue does not become large, or the discrepancy between the uplink data amount permitted for transmission at the time of transmission and the uplink data amount of the queue is large. It is a subscriber line termination device further comprising at least one of the declaration adjustment units that controls the allocation request amount so as not to become.

One aspect of the present invention includes a transmission permission unit that permits transmission of uplink data using the allocation request amount declared by the subscriber line termination device, and the amount of uplink data permitted to be transmitted at the time of transmission of the subscriber line termination device. The queue adjustment unit that controls the congestion avoidance processing unit of the subscriber line termination device so that the deviation from the uplink data amount of the queue does not become large, or the uplink data amount permitted to be transmitted at the time of transmission of the subscriber line termination device and the queue. The deviation between the amount of uplink data permitted to be transmitted at the time of transmission of the declaration adjustment unit or the subscriber line termination device that controls the allocation request amount so that the deviation from the amount of uplink data does not become large and the amount of uplink data of the queue It is a subscriber line end station device further comprising at least one of permission adjusting units for controlling transmission permission so as not to be large.

According to the present invention, the allocated transmission band can be utilized more efficiently.

It is an overall block diagram of the communication system 1. It is a 1st functional block diagram which shows a specific example of the functional structure of ONU 100 of 1st Embodiment. It is a 2nd functional block diagram which shows a specific example of the functional structure of ONU 100 of 1st Embodiment. It is a 3rd function block diagram which shows a specific example of the functional structure of ONU 100 of 1st Embodiment. It is a flowchart which shows the flow of the process which suppresses the discarding of the frame of 1st Embodiment. It is a flowchart which shows the flow of the process which suppresses the discarding of the frame corresponding to the requested queue of 1st Embodiment. It is a flowchart which shows the flow of the process which controls the disposal based on the frame which arrived after the allocation request of 1st Embodiment. It is a flowchart which shows the flow of the process of transmitting the allocation request amount to the OLT200 of 1st Embodiment. It is a flowchart which shows the flow of the process of discarding a frame after calculating the disposal predicted value of 1st Embodiment. It is a 1st function block diagram which shows a specific example of the functional structure of the OLT200 of 2nd Embodiment. It is a 2nd functional block diagram which shows a specific example of the functional structure of the OLT200 of 1st Embodiment. It is a 3rd function block diagram which shows a specific example of the functional structure of the OLT200 of 1st Embodiment. It is a flowchart which shows the flow | flow of the process which determines the transmission permission amount by the OLT200 of the 2nd Embodiment. It is a flowchart which shows the flow of setting of the congestion avoidance parameter of 5th Embodiment. It is a flowchart which shows the flow of setting of the congestion avoidance parameter of 5th Embodiment, and discarding a requested queue. It is a flowchart which shows the flow of the setting of the congestion avoidance parameter of 5th Embodiment, and the process of discarding based on the arrival frame. It is a flowchart which shows the flow of setting of the congestion avoidance parameter of 5th Embodiment, and the process of suppressing the discarding of a frame. It is a flowchart which shows the flow of setting of the congestion avoidance parameter based on the disposal prediction value of 5th Embodiment.

(First Embodiment)
FIG. 1 is an overall configuration diagram of the communication system 1. The communication system 1 includes a plurality of ONU100s, OLT200s, and ODN300s. The ONU 100 and the OLT 200 are communicably connected to each other via the ODN 300. Each ONU 100 is communicably connected to a plurality of user devices 400.

The ONU 100 is a subscriber line terminating device. The ONU 100 is a device that realizes communication with another communication device by a signal passing through a communication network. The communication network to which the ONU 100 is connected is, for example, a passive optical communication network such as PON. The ONU 100 is installed, for example, in the home of a user who receives a communication service. The ONU 100 may be a part of a device such as FTTB (Fiber to the building).

The ONU 100 includes a queue for storing uplink data (hereinafter referred to as “frame”) received from the user device 400. The ONU 100 discards queue frames by a congestion avoidance processing unit such as AQM or Tail Dropping at the time of congestion or when congestion is predicted.

The OLT 200 is a subscriber line end station device. The OLT 200 is a device that realizes communication with another communication device (for example, ONU) by a signal passing through a communication network. The communication network to which the OLT 200 is connected is, for example, a passive optical communication network such as PON. The OLT 200 is installed, for example, in a station building connected to a communication network.

The ODN 300 transmits an uplink signal and a downlink signal. When the ODN 300 includes an optical splitter, the ODN 300 combines the uplink signals transmitted from the ONU 100 and transmits the uplink signals to the OLT 200. When the ODN 300 includes an optical splitter, the ODN 300 branches the downlink signal transmitted from the OLT 200 and transmits the downlink signal to the ONU 100.

The user device 400 is a device operated by the user. The user device 400 is installed, for example, in the home of a user who receives a communication service. The user device 400 is a communicable information processing device such as a personal computer, a smartphone, a mobile phone, a tablet computer, a wireless LAN router, or a television receiver.

2 to 4 are first to third functional block diagrams showing a specific example of the functional configuration of the ONU 100 of the first embodiment. The ONU 100 includes a first communication unit 101, a second communication unit 102, a frame storage unit 103, and a control unit 105. The ONU 100 may include a waste information storage unit 104.

The first communication unit 101 is a network interface. The first communication unit 101 transmits the frame to the OLT 200 as an uplink signal according to the transmission permission received from the OLT 200. The first communication unit 101 receives the downlink signal transmitted from the OLT 200 as downlink data.

The second communication unit 102 is a network interface. The second communication unit 102 transmits the downlink data received from the OLT 200 to the user device 400. The second communication unit 102 receives the frame transmitted from the user device 400.

The frame storage unit 103 is configured by using a storage device such as a magnetic hard disk device or a semiconductor storage device. The frame storage unit 103 holds a queue of frames. The frame storage unit 103 may hold the frame so that the user device 400 or the connection can be identified.

The waste information storage unit 104 is configured by using a storage device such as a magnetic hard disk device or a semiconductor storage device. The waste information storage unit 104 stores the waste information. The discard information is information about the frame discarded by the congestion avoidance processing unit 107. The discard information may include the amount of data of the discarded frame, the information for identifying the user device 400 as the transmission source, and the discard time.

The control unit 105 controls the operation of each unit of the ONU 100. The control unit 105 is executed by a device including, for example, a CPU (Central Processing Unit) and a RAM (Random Access Memory). The control unit 105 executes the allocation request unit 106 by executing the allocation request program, the congestion avoidance processing unit 107 by executing the frame discard program, the queue adjustment unit 108 by executing the queue adjustment program, and the request adjustment program. By doing so, they may function as the declaration adjustment unit 109 described with reference to FIG.

The allocation request unit 106 transmits a signal (for example, a REPORT signal) requesting the OLT 200 to allocate a band. Specifically, the allocation request unit 106 acquires a queue length indicating the length of the queue stored in the frame storage unit 103. The allocation request unit 106 may calculate the amount of data from the acquired queue length. The allocation request unit 106 transmits the queue length or the calculated data amount as the allocation request amount to the OLT 200. Sending the allocation request amount from the ONU 100 to the OLT 200 is one aspect of the declaration.

The congestion avoidance processing unit 107 discards the frames held in the queue by executing AQM, Tail Dropping, or the like. The congestion avoidance processing unit 107 may generate disposal information based on the discarded frames.

In the present embodiment, at least one of the cue adjustment unit 108 and the declaration adjustment unit 109 is provided. In the present embodiment, the bandwidth request value or the queue length or the discard is controlled so that the discrepancy between the amount of uplink data permitted to be transmitted at the time of transmission and the amount of uplink data of the queue does not become large.

In the present embodiment, as shown in FIG. 2, the control unit 105 may include a cue adjustment unit 108. The queue adjustment unit 108 controls the congestion avoidance processing unit 107 to discard frames at a predetermined time after the allocation request amount is transmitted to the OLT 200, or until the uplink data is transmitted by the transmission permission corresponding to the allocation request amount. Specifically, the queue adjusting unit 108 controls the discarding of frames by the congestion avoidance processing unit 107 by using a predetermined method. The predetermined method is the first, second or third method described later.

In the present embodiment, as shown in FIG. 3, the control unit 105 may include a declaration adjustment unit 109. The declaration adjustment unit 109 adjusts the allocation request amount so that the discrepancy between the allocation request amount for the OLT 200 and the frame amount held at the time of transmission permission becomes small. Specifically, the declaration adjustment unit 109 adjusts the allocation request amount by the allocation request unit 106 by using a predetermined method. The predetermined method is the fourth or fifth method described later. The declaration adjustment unit 109 is an aspect of the declaration adjustment unit. The filing adjustment unit controls the allocation request amount for the OLT 200.
In the present embodiment, as shown in FIG. 4, the control unit 105 may include a cue adjustment unit 108 and a declaration adjustment unit 109.

(First method)
The first method will be described with reference to FIGS. 2 and 5. FIG. 5 is a flowchart showing a flow of processing for suppressing the discarding of the frame of the first embodiment. The flowchart shown in FIG. 5 is executed when the congestion avoidance processing unit 107 discards a frame.

The queue adjustment unit 108 determines whether or not a predetermined time has elapsed since the allocation request amount was transmitted to the OLT 200 (step S101). The predetermined time may be the time until the transmission permission is received from the OLT 200, the time set in advance in the ONU 100, or the time specified in advance from the OLT 200. , It may be until the time calculated by statistical processing such as average elapses based on the history of the time until the past transmission permission is received.

When the predetermined time has elapsed (step S101: YES), the congestion avoidance processing unit 107 enables the frame to be discarded (step S102). Specifically, the congestion avoidance processing unit 107 may discard the frame when the queue length is longer than a predetermined value or the queue is significantly extended. When the predetermined time has not elapsed (step S101: NO), the queue adjustment unit 108 suppresses the frame discard by the congestion avoidance processing unit 107 (step S103). The congestion avoidance processing unit 107 may be configured to suppress the discarding of frames by transmitting uplink data.

(Second method)
The second method will be described with reference to FIGS. 2 and 6. FIG. 6 is a flowchart showing a flow of processing for suppressing the discarding of frames corresponding to the requested queue of the first embodiment. The flowchart shown in FIG. 6 is executed when the congestion avoidance processing unit 107 discards a frame.

The queue adjustment unit 108 determines whether or not a predetermined time has elapsed since the allocation request amount was transmitted to the OLT 200 (step S201). The predetermined time may be the time until the transmission permission is received from the OLT 200, the time set in advance in the ONU 100, or the time specified in advance from the OLT 200. , It may be until the time calculated by statistical processing such as average elapses based on the history of the time until the past transmission permission is received.

When the predetermined time has elapsed (step S201: YES), the congestion avoidance processing unit 107 enables the frame to be discarded (step S202). When the predetermined time has not elapsed (step S201: NO), the queue adjustment unit 108 suppresses the discarding of the frame corresponding to the queue length for which the allocation request has been made by the congestion avoidance processing unit 107 or the frame related to the allocation request. (Step S203).

In the second method, the congestion avoidance processing unit 107 discards the frames of the queue that are not included in the allocation request amount at the timing when the predetermined time has not elapsed. When the congestion avoidance processing unit 107 can identify the user device 400 or the connection for each frame, and when the frame discarding is not controlled by the queue adjustment unit 108, the congestion avoidance processing unit 107 discards the frame within a predetermined time. It may be configured to preferentially discard a frame of a user device 400 or a connection that has not been set.

Specifically, the congestion avoidance processing unit 107 integrates the frame discard history in advance by an index average or the like. The congestion avoidance processing unit 107 may preferentially discard the connection having a small integrated value or the frame of the user device 400, except for the frame whose discard is suppressed. Further, when the frames to be discarded are biased toward the same connection or the user device 400, the congestion avoidance processing unit 107 may reduce the frame discard rate or the number of discards, or is configured not to discard the frames. May be good.

(Third method)
The third method will be described with reference to FIGS. 2 and 7. FIG. 7 is a flowchart showing a flow of processing for controlling disposal based on a frame arriving after the allocation request of the first embodiment. The flowchart shown in FIG. 7 is executed when the congestion avoidance processing unit 107 discards a frame.

The queue adjustment unit 108 determines whether or not a predetermined time has elapsed since the allocation request amount was transmitted to the OLT 200 (step S301). The predetermined time may be the time until the transmission permission is received from the OLT 200, the time set in advance in the ONU 100, or the time specified in advance from the OLT 200. , It may be until the time calculated by statistical processing such as average elapses based on the history of the time until the past transmission permission is received.

When the predetermined time has elapsed (step S301: YES), the congestion avoidance processing unit 107 enables the frame to be discarded (step S302). When the predetermined time has not elapsed (step S301: NO), the queue adjusting unit 108 determines whether or not the queue length is larger than the allocation request amount (step S303).

If it is larger than the allocation request amount (step S303: YES), the congestion avoidance processing unit 107 discards the frame corresponding to the excess data amount (step S304). For example, when the ONU 100 receives a frame after transmitting the allocation request amount, the congestion avoidance processing unit 107 discards the frame up to the sum of the lengths of the received frames. If it is not larger than the allocation request amount (step S303: NO), the queue adjustment unit 108 ends the process. The congestion avoidance processing unit 107 may be configured to suppress the discarding of frames by transmitting uplink data.

The congestion avoidance processing unit 107 may be configured to discard in frame units, up to the sum of the received frame lengths. With this configuration, partial disposal of the frame can be avoided. When the received frame length exceeds the MTU (Maximum Transmission Unit), the congestion avoidance processing unit 107 may discard the frame.

In the third method, short frames may be preferentially discarded. The congestion avoidance processing unit 107 integrates the frame discard history in advance by an index average or the like. The congestion avoidance processing unit 107 stops discarding frames received from the connection or the user device 400 when the integration result exceeds a predetermined difference or ratio as compared with the integration result of the other connection or the user device 400. It may be configured to do so. With this configuration, it is possible to eliminate the case where short frames are preferentially discarded.

The third method is configured to fit frame boundaries, but may have a low MTU (or less than MTU), a higher MTU (or less than MTU), and an allocation request. It may be a quantity.

(Fourth method)
The fourth method will be described with reference to FIGS. 3 and 8. FIG. 3 is a second functional block diagram showing a specific example of the functional configuration of the ONU 100 of the first embodiment. FIG. 8 is a flowchart showing a flow of processing for transmitting an allocation request amount to the OLT 200 of the first embodiment. The flowchart shown in FIG. 8 is executed when the allocation request unit 106 transmits the allocation request amount to the OLT 200.

The declaration adjustment unit 109 acquires information (hereinafter referred to as “prediction information”) for calculating the predicted value of the frame to be discarded by the congestion avoidance processing unit 107 (step S401). The predicted information may include the queue length, the extension speed of the queue length, and the disposal information stored in the disposal information storage unit 104, or a fixed value or the queue length and the queue length given in advance from the controller, OLT200, or the like. A function in which the extension speed and the disposal speed of the above are used as variables may be given from the OLT 200, the controller, or the like, and calculated by the declaration adjustment unit 109 based on the function. The declaration adjustment unit 109 calculates a discard prediction value of the discarded frame based on the prediction information (step S402). The discarded discard value is a value that predicts the amount of frames discarded by the congestion avoidance processing unit 107.

The declaration adjustment unit 109 determines whether or not the estimated disposal value is greater than 0 (step S403). If the estimated disposal value is greater than 0 (step S403: YES), the allocation request unit 106 subtracts the estimated disposal value from the allocation request amount (step S404). If the predicted disposal value is not greater than 0 (step S403: NO), the allocation request unit 106 transmits the allocation request amount to the OLT 200 as it is (step S405). The allocation request unit 106 may reduce the expected disposal value according to the particle size of MTU, TQ, or the like.

(Fifth method)
The fifth method will be described with reference to FIGS. 4 and 9. FIG. 4 is a third functional block diagram showing a specific example of the functional configuration of the ONU 100 of the first embodiment. FIG. 9 is a flowchart showing the flow of the process of discarding the frame after calculating the disposal predicted value of the first embodiment. The flowchart shown in FIG. 9 is executed when the allocation request unit 106 transmits the allocation request amount to the OLT 200 from step S401 to step S405. Steps S501 to S503 are executed when the congestion avoidance processing unit 107 discards a frame. Since steps S401 to S405 are the same as the fourth method, the description thereof will be omitted.

The queue adjustment unit 108 determines whether or not the amount of frames discarded by the congestion avoidance processing unit 107 is within the expected discard value (step S501). If it is within the predicted discard value (step S501: YES), the congestion avoidance processing unit 107 discards the frame (step S502). If it is not within the estimated disposal value (step S501: NO), the queue adjustment unit 108 adjusts the amount of frames to be discarded within the predicted disposal value, and causes the congestion avoidance processing unit 107 to discard it (step S503). ..

In the communication system 1 configured in this way, the queue adjusting unit 108 controls the discarding of frames by the congestion avoidance processing unit 107 by a predetermined method. Therefore, the discrepancy between the allocation request amount transmitted by the ONU 100 and the amount of frames held at the time of transmission permission can be reduced, and the transmission band can be utilized more efficiently. In addition, the declaration adjustment unit 109 adjusts the allocation request amount transmitted to the OLT 200. Therefore, the discrepancy between the allocation request amount transmitted by the ONU 100 and the amount of frames held at the time of transmission permission can be reduced, and the transmission band can be utilized more efficiently.

The frame storage unit 103 may be configured to store a plurality of queues. For example, the frame storage unit 103 may store the priority-controlled frame in the priority queue and store the other queues in the normal queue. The frame storage unit 103 may be configured to store a queue for each user device 400. When a plurality of queues are stored in the frame storage unit 103, the queue adjusting unit 108 may control the discarding of frames for each queue length of the queue, or discards frames based on the total value of each queue length. May be controlled.

(Second Embodiment)
FIG. 10 is a functional block diagram showing the functional configuration of the OLT 200 of the second embodiment. The OLT 200 includes a first communication unit 201, a second communication unit 202, and a control unit 204. The OLT 200 may include a history information storage unit 203. The ONU 100 of the second embodiment includes at least an allocation request unit 106 and a congestion avoidance processing unit 107, but the queue adjustment unit 108 and the declaration adjustment unit 109 may not be provided.

The first communication unit 201 is a network interface. The first communication unit 201 receives an uplink signal from the ONU 100. The first communication unit 201 transmits the downlink data received from the higher-level device to the ONU 100 as a downlink signal.

The second communication unit 202 is a network interface. The second communication unit 202 transmits the frame received from the ONU 100 to a higher-level device. The second communication unit 202 receives the downlink data transmitted from the higher-level device.

The history information storage unit 203 is configured by using a storage device such as a magnetic hard disk device or a semiconductor storage device. The history information storage unit 203 stores the history information. The history information is information indicating the difference between the allocation request amount received from the ONU 100 and the data amount actually received.

The control unit 204 controls the operation of each unit of the OLT 200. The control unit 204 is executed by a device including, for example, a CPU and a RAM. The control unit 204 executes the transmission permission unit 205 by executing the transmission permission program, the permission adjustment unit 207 by executing the permission adjustment program, the declaration adjustment unit 206 by executing the declaration value adjustment program, and the queue adjustment program. By doing so, they may function as the cue adjusting unit 208.

The transmission permission unit 205 transmits a signal indicating transmission permission (for example, a GATE signal, BWMap, etc.) to the ONU 100. Specifically, the transmission permission unit 205 calculates the transmission permission amount based on the allocation request amount received from the ONU 100. The transmission permission unit 205 includes the transmission permission amount in the signal and transmits the transmission to the ONU 100.

In the present embodiment, at least one of the declaration adjustment unit 206 as shown in FIG. 10, the permission adjustment unit 207 as shown in FIG. 11, and the cue adjustment unit 208 as shown in FIG. 12 is provided. In the present embodiment, permission or bandwidth request value or queue length or discard is controlled so that the difference between the amount of uplink data permitted for transmission at the time of transmission and the amount of uplink data in the queue does not become large. Although not shown, a plurality or all of the declaration adjustment unit 206, the permission adjustment unit 207, and the cue adjustment unit 208 provided in FIGS. 10 to 12 may be provided and prorated to reduce the deviation.

In the present embodiment, as shown in FIG. 10, the control unit 204 may include the declaration adjustment unit 206. The declaration adjustment unit 206 adjusts the allocation request amount so that the discrepancy between the amount of uplink data permitted to be transmitted at the time of transmission and the amount of uplink data in the queue or the amount of frames is small. Specifically, the declaration adjustment unit 206 adjusts the allocation request amount by the allocation request unit 106 by using a predetermined method. The predetermined method is the above-mentioned fourth or fifth method.

In the present embodiment, as shown in FIG. 11, the control unit 204 may include the permission adjustment unit 207. The permission adjusting unit 207 determines the transmission permission amount so that the discrepancy between the transmission permission amount allocated to the ONU 100 and the actually received data amount becomes small. The specific flow of processing will be described with reference to the flowchart of FIG. 13 described later.

A flowchart showing a flow of processing in which the OLT 200 of the second embodiment determines a transmission permission amount will be described with reference to FIGS. 11 and 13. FIG. 11 is a second functional block diagram showing a specific example of the functional configuration of the OLT 200 of the first embodiment. FIG. 13 is a flowchart showing a flow of processing in which the OLT 200 of the second embodiment determines a transmission permission amount. The flowchart shown in FIG. 13 is executed when the permission adjusting unit 207 transmits the transmission permission amount to the ONU 100.

The OLT 200 receives the allocation request amount from the ONU 100 (step S601). The permission adjustment unit 207 acquires history information from the history information storage unit 203 (step S602). The permission adjustment unit 207 calculates the difference prediction value of the frames discarded by the ONU 100 based on the history information (step S603). The difference predicted value is a value that predicts the difference between the allocation request amount and the data amount received from the ONU 100. In the calculation, a function with variables such as a fixed value, a declared value, a change rate of the declared value, or a transition of the actual usage rate with respect to the allocation, which is set in advance from the controller or the like, may be given from the controller or the like and set based on the function. .. The actual usage rate may be acquired by OLT, or may be predicted by a higher-level device, a controller, or the like based on the flow rate of the higher-level device.

The permission adjusting unit 207 determines whether or not the difference predicted value is larger than 0 (step S604). When the difference prediction value is larger than 0 (step S604: YES), the permission adjustment unit 207 reduces the difference prediction value from the transmission permission amount. The transmission permission unit 205 transmits the subtracted value as the transmission permission amount to the ONU 100 (step S605). When the difference predicted value is not larger than 0 (step S604: NO), the transmission permission unit 205 transmits the transmission permission amount to the ONU 100 as it is (step S606).

In the communication system 1 configured in this way, the permission adjustment unit 207 adjusts the transmission permission amount to be allocated to the ONU 100 based on the difference between the received allocation request amount and the actually received data amount. Therefore, the discrepancy between the allocation request amount received from the ONU 100 and the data amount actually received by the OLT 200 can be reduced, and the transmission band can be used more efficiently.

The flow of the transmission permission processing by the OLT 200 will be described with reference to FIGS. 10 and 8. FIG. 10 is a third functional block diagram showing a specific example of the functional configuration of the OLT 200 of the first embodiment. In the first embodiment, FIG. 8 is described in detail as a flowchart showing the flow of processing of the allocation request amount in the ONU 100. In the second embodiment, the flowchart shown in FIG. 8 is executed when the declaration adjustment unit 206 transmits the transmission permission amount to the ONU 100.

The declaration adjustment unit 206 acquires information (hereinafter referred to as “prediction information”) for calculating the predicted value of the frame to be discarded by the congestion avoidance processing unit 107 (step S401). The prediction information may include the queue length, the extension speed of the queue length, and the history information stored in the history information storage unit 203, or the fixed value, the declared value, or the extension of the declared value given in advance from the controller or the like. A function in which the speed, the disposal speed, etc. are variables may be given from the controller or the like, and the declaration adjustment unit 206 may calculate based on the function. The declaration adjustment unit 206 calculates the discarded frame predicted value of the discarded frame based on the predicted information (step S402). The discarded discard value is a value that predicts the amount of frames discarded by the congestion avoidance processing unit 107.

The declaration adjustment unit 206 determines whether or not the estimated disposal value is greater than 0 (step S403). When the estimated disposal value is larger than 0 (step S403: YES), the declaration adjustment unit 206 sets the value obtained by subtracting the estimated disposal value from the allocation request amount as the transmission permitted amount (step S404). When the discarded disposal predicted value is not larger than 0 (step S403: NO), the transmission permission unit 205 transmits the transmission permission amount to the OLT 200 as it is (step S405). The transmission permission unit 205 may reduce the estimated disposal value according to the particle size of MTU, TQ, or the like.

(Third Embodiment)
The communication system 1 of the third embodiment is configured by combining the ONU 100 of the first embodiment and the OLT 200 of the second embodiment. The communication system 1 configured in this way may predict or control the amount of waste of frames proportionally divided by ONU100 and OLT200.

When the predicted value is exchanged between ONU100 and OLT200, the amount of frame discarded is apportioned as follows. Specifically, the permission adjustment unit 207 of the OLT 200 calculates a statistical value such as an average value of the amount of waste of frames. The statistical value is used by the permission adjustment unit 207 to reduce the transmission permission amount. The transmission permission unit 205 transmits a statistical value, for example, an average value, for example, a value obtained by subtracting a dispersion amount N times the average value from the transmission permission amount, as a transmission permission amount to the ONU 100. The OLT 200 transmits the calculated statistical value to the ONU 100. When it is necessary to reduce the allocation request amount from the statistical value, the queue adjustment unit 108 of the ONU 100 transmits a value obtained by subtracting the difference from the statistical value from the allocation request amount to the OLT 200.

When the predicted value is not exchanged between ONU100 and OLT200, the amount of frame discarded is apportioned as follows. Specifically, the permission adjustment unit 207 of the OLT 200 calculates the difference prediction value as in the second embodiment. The OLT 200 transmits a value obtained by subtracting the difference prediction value from the transmission permitted amount to the ONU 100. The queue adjustment unit 108 of the ONU 100 transmits data to the OLT 200 based on the transmission permitted amount. When a change such as a sudden increase in the amount of uplink data from the ONU 100 occurs, the declaration adjustment unit 109 of the ONU 100 transmits a value obtained by subtracting the rapidly increased amount of uplink data from the allocation request amount to the OLT 200.

In the communication system 1 configured in this way, the ONU 100 and the OLT 200 control the allocation request amount and the transmission permission amount, respectively. Therefore, the allocated transmission band can be utilized more efficiently.

(Fourth Embodiment)
The communication system 1 in the fourth embodiment is different from the first or second embodiment in that congestion avoidance parameters are set, but the other configurations are the same. Hereinafter, the points different from the first or second embodiment will be described.

FIG. 2 is a functional block diagram showing a functional configuration of the ONU 100 according to the fourth embodiment. In the ONU 100, the queue adjusting unit 108 sets the parameters. The ONU 100 is the same as the ONU 100 in the first embodiment in other respects.

Parameters such as congestion avoidance parameters set by the queue adjustment unit 108 may be held by using a storage device such as a magnetic hard disk device or a semiconductor storage device. The congestion avoidance parameter is a parameter used for determining the condition for discarding the frame held in the queue by AQM operating on the ONU100, Tail Dropping, or the like.

The control unit 105 controls the operation of each unit of the ONU 100. The control unit 105 is executed by a device including, for example, a CPU and a RAM. The control unit 105 executes the allocation request unit 106 by executing the allocation request program, the congestion avoidance processing unit 107 by executing the frame discard program, the queue adjustment unit 108 by executing the queue adjustment program, and the declaration adjustment program. By doing so, they may function as the filing adjustment unit 109.

The queue adjustment unit 108 outputs the congestion avoidance parameter to the congestion avoidance processing unit 107. The congestion avoidance processing unit 107 executes frame discarding by AQM, Tail Dropping, or the like based on the received congestion avoidance parameters.

In the fourth embodiment, the OLT 200 may include a cue adjusting unit. FIG. 12 is a functional block diagram showing a specific example of the functional configuration of the OLT 200 according to the fourth embodiment. The control unit 204 of the OLT 200 in FIG. 12 includes a cue adjustment unit 208.

The parameters set by the queue adjusting unit 108 of the ONU 100 may be determined by the queue adjusting unit 208 of the OLT 200 and set in the ONU 100. In that case, the queue adjustment unit 208 determines the congestion avoidance parameter based on the bandwidth request amount or the bandwidth allocation status of the uplink signal of the ONU 100. The queue adjustment unit 208 calculates the band demand amount of the uplink signal of the ONU 100 from the sum of the band demand amounts received from each ONU 100 as a parameter. The queue adjustment unit 208 transmits the determined congestion avoidance parameter to the ONU 100.

The congestion avoidance parameter may be a target queue length, a threshold value at which frame discarding is started by the congestion avoidance processing unit 107, or a threshold value at which discarding is stopped. The congestion avoidance processing unit 107 discards frames so as to be close to the target queue length. The congestion avoidance parameter for RED and the like may be adjusted for each priority queue, Alloc-ID, LLID or ONU100. Further, when the OLT 200 includes a priority queue, the congestion avoidance parameter may be adjusted for each priority queue. The queue adjustment unit 208 may periodically execute the determination of the congestion avoidance parameter, may be the same as the DBA cycle, or may be a divisor or a multiple of the DBA cycle.

In the communication system 1 configured in this way, the OLT 200 determines congestion avoidance parameters that define operations such as AQM and Tail Dropping. The queue adjustment unit 108 of the ONU 100 sets the congestion avoidance parameter in the congestion avoidance processing unit 107. The congestion avoidance processing unit 107 discards the frame based on the set congestion avoidance parameter. Therefore, the discarding of frames can be changed according to the operating status of the communication system 1, and the transmission band can be used more efficiently.

Here, it is assumed that the cue adjustment unit 208 of the OLT 200 sets the parameters via the cue adjustment unit 108 of the ONU 100, but the ONU 100 does not have the cue adjustment unit 108, and the cue adjustment unit 208 of the OLT 200 avoids congestion of the ONU 100. The parameters of the processing unit 107 may be set.

Further, in this embodiment, the cue adjustment unit is arranged in the ONU or the OLT, but other than that, for example, a controller for controlling the ONU or the OLT or an arbitrary place inside or outside the network may be arranged. However, the response is delayed by the delay related to the communication with the congestion avoidance processing unit, and it is desirable that the location has less delay from the viewpoint of reducing the overshoot of the response.

(Fifth Embodiment)
In the fifth embodiment, the queue adjusting unit 108 of the ONU 100 or the queue adjusting unit 208 of the OLT 200 determines the timing for setting the congestion avoidance parameter determined in the fourth embodiment. The cue adjusting unit 108 determines the timing by the following sixth to tenth methods. The sixth to tenth methods are executed when the ONU 100 receives the congestion avoidance parameter.

(Sixth method)
The sixth method will be described with reference to FIG. FIG. 14 is a flowchart showing a flow of setting the congestion avoidance parameter of the fifth embodiment. The queue adjustment unit 108 determines whether or not a predetermined time has elapsed since the allocation request amount was transmitted to the OLT 200 (step S701). The predetermined time may be the time until the transmission permission is received from the OLT 200, the time set in advance in the ONU 100, or the time specified in advance from the OLT 200. , It may be until the time calculated by statistical processing such as average elapses based on the history of the time until the past transmission permission is received.

When the predetermined time has elapsed (step S701: YES), the queue adjusting unit 108 sets the congestion avoidance parameter in the congestion avoidance processing unit 107 (step S702). When the predetermined time has not elapsed (step S701: NO), the parameter setting unit 111 sets the congestion avoidance parameter in the congestion avoidance processing unit 107. The queue adjustment unit 108 suppresses frame discard by the congestion avoidance processing unit 107 until a predetermined time elapses (step S703). In step S703, the queue adjustment unit 108 may be configured to postpone the timing of setting the congestion avoidance parameter in the congestion avoidance processing unit 107.

(7th method)
The seventh method will be described with reference to FIG. FIG. 15 is a flowchart showing a flow of setting the congestion avoidance parameter of the fifth embodiment and discarding the requested queue. The queue adjustment unit 108 determines whether or not a predetermined time has elapsed since the allocation request amount was transmitted to the OLT 200 (step S801). The predetermined time may be the time until the transmission permission is received from the OLT 200, the time set in advance in the ONU 100, or the time specified in advance from the OLT 200. , It may be until the time calculated by statistical processing such as average elapses based on the history of the time until the past transmission permission is received.

When the predetermined time has elapsed (step S801: YES), the queue adjusting unit 108 sets the congestion avoidance parameter in the congestion avoidance processing unit 107 (step S802). When the predetermined time has not elapsed (step S801: NO), the queue adjustment unit 108 sets the congestion avoidance parameter in the congestion avoidance processing unit 107. The queue adjustment unit 108 suppresses the discarding of frames corresponding to the requested queue by the congestion avoidance processing unit 107 (step S803). In step S803, the queue adjustment unit 108 may be configured to postpone the timing of setting the congestion avoidance parameter in the congestion avoidance processing unit 107.

In the seventh method, the congestion avoidance processing unit 107 discards the frames of the queue that are not included in the allocation request amount at the timing when the predetermined time has not elapsed. When the congestion avoidance processing unit 107 can identify the user device 400 or the connection for each frame, and when the frame discarding is not controlled by the queue adjustment unit 108, the congestion avoidance processing unit 107 discards the frame within a predetermined time. It may be configured to preferentially discard a frame of a user device 400 or a connection that has not been set.

For example, the congestion avoidance processing unit 107 integrates the frame discard history in advance with an exponential average or the like. The congestion avoidance processing unit 107 may preferentially discard the connection having a small integrated value or the frame of the user device 400, except for the frame whose discard is suppressed. Further, when the frames to be discarded are biased toward the same connection or the user device 400, the congestion avoidance processing unit 107 may reduce the frame discard rate or the number of discards, or is configured not to discard the frames. May be good.

(8th method)
The eighth method will be described with reference to FIG. FIG. 16 is a flowchart showing the flow of setting the congestion avoidance parameter of the fifth embodiment and the process of discarding based on the arrived frame. The queue adjustment unit 108 determines whether or not a predetermined time has elapsed since the allocation request amount was transmitted to the OLT 200 (step S901). The predetermined time may be the time until the transmission permission is received from the OLT 200, the time set in advance in the ONU 100, or the time specified in advance from the OLT 200. , It may be until the time calculated by statistical processing such as average elapses based on the history of the time until the past transmission permission is received.

When the predetermined time has elapsed (step S901: YES), the queue adjusting unit 108 sets the congestion avoidance parameter in the congestion avoidance processing unit 107 (step S902). When the predetermined time has not elapsed (step S901: NO), the queue adjusting unit 108 determines whether or not the amount of data calculated from the queue length is larger than the allocation request amount (step S903).

If it is not larger than the allocation request amount (step S903: NO), the queue adjustment unit 108 sets the congestion avoidance parameter in the congestion avoidance processing unit 107 (step S902). When it is larger than the allocation request amount (step S903: YES), the queue adjustment unit 108 sets the congestion avoidance parameter in the congestion avoidance processing unit 107. The queue adjustment unit 108 suppresses the discarding of frames corresponding to the requested queue by the congestion avoidance processing unit 107 (step S904). For example, when the ONU 100 receives a frame after transmitting the allocation request amount, the congestion avoidance processing unit 107 discards the frame up to the sum of the lengths of the received frames.

The congestion avoidance processing unit 107 may be configured to discard in frame units, up to the sum of the received frame lengths. With this configuration, partial disposal of the frame can be avoided. If the received frame length exceeds the MTU, the congestion avoidance processing unit 107 may discard the frame.

In the eighth method, short frames may be preferentially discarded. The congestion avoidance processing unit 107 integrates the frame discard history in advance by an index average or the like. The congestion avoidance processing unit 107 stops discarding frames received from the connection or the user device 400 when the integration result exceeds a predetermined difference or ratio as compared with the integration result of the other connection or the user device 400. It may be configured to do so. With this configuration, it is possible to eliminate the case where short frames are preferentially discarded.

The eighth method is configured to fit frame boundaries, but may have a low MTU (or less than MTU), a higher MTU (or less than MTU), and an allocation request. It may be a quantity.

(9th method)
The ninth method will be described with reference to FIG. FIG. 17 is a flowchart showing the flow of setting the congestion avoidance parameter of the fifth embodiment and the process of suppressing the discarding of frames. The declaration adjustment unit 109 acquires the forecast information (step S1001). The declaration adjustment unit 109 calculates the disposal prediction value based on the prediction information (step S1002).

The queue adjustment unit 108 determines whether or not a time has elapsed that does not cause disposal by the congestion avoidance processing unit 107 (step S1003). When the time has not elapsed (step S1003: NO), the queue adjustment unit 108 sets the congestion avoidance parameter in the congestion avoidance processing unit 107. The queue adjustment unit 108 suppresses frame discard by the congestion avoidance processing unit 107 until a predetermined time elapses (step S1004). In step S1004, the queue adjustment unit 108 may be configured to postpone the timing of setting the congestion avoidance parameter in the congestion avoidance processing unit 107. When the time has elapsed (step S1003: YES), the queue adjustment unit 108 sets the congestion avoidance parameter in the congestion avoidance processing unit 107 (step S1005).

(10th method)
The tenth method will be described with reference to FIG. FIG. 18 is a flowchart showing the flow of setting the congestion avoidance parameter based on the disposal predicted value of the fifth embodiment. The flowchart shown in FIG. 18 is the same as the ninth method from step S1001 to step S1004.

The queue adjustment unit 108 determines whether or not the amount of frames discarded by the congestion avoidance processing unit 107 is a value higher than the predicted value by the MTU (step S1101). When the value is MTU higher than the predicted value (step S1101: YES), the queue adjustment unit 108 suppresses the setting of the congestion avoidance parameter (step S1102). If the value is not higher than the predicted value by MTU (step S1101: NO), the queue adjustment unit 108 sets the congestion avoidance parameter in the congestion avoidance processing unit 107 (step S1103).

In the communication system 1 configured in this way, the queue adjustment unit 108 adjusts the timing for setting the congestion avoidance parameter. The queue adjustment unit 108 does not immediately set the congestion avoidance parameter. Therefore, the congestion avoidance processing unit 107 can prevent the case where extra frames are discarded from the queue by setting the congestion avoidance parameter, and can utilize the allocated transmission band more efficiently. ..

(Sixth Embodiment)
The communication system 1 of the sixth embodiment is configured by combining any one of the first to third embodiments and the fifth embodiment. In the communication system 1 configured in this way, the congestion avoidance parameters are dynamically changed. Specifically, the queue adjustment unit 208 determines the congestion avoidance parameter. The queue adjustment unit 108 sets the determined congestion avoidance parameter in the congestion avoidance processing unit 107. The congestion avoidance processing unit 107 discards frames based on the congestion avoidance parameters. Therefore, the ONU 100 can more efficiently utilize the allocated transmission band even when the amount of uplink data increases or decreases.

In the embodiment of the present application, the cue adjustment unit, the declaration adjustment unit, and the permission adjustment unit are arranged in any control unit of ONU or OLT or ONU and OLT, but other than that, for example, a controller or a network for controlling ONU or OLT. It may be placed anywhere inside or outside. However, the response is delayed by the delay related to the communication with the ONU or OLT, and it is desirable that the location has less delay from the viewpoint of reducing the overshoot of the response.

The PON applied to the present invention may be a gigabit passive optical network (G-PON), and other PONs such as broadband PON (BPON) and Ethernet PON (EPON) (Ethernet: registered trademark). , NG-PON2 or XGS-PON.

Although the present invention has been described by taking one or more ONUs as an example, other network termination devices (for example, ONTs) used for PON may be used. Although the present invention has been described by taking RED as an example, other congestion avoidance methods such as WRED may be used. Although the ONU has been described with the example of having one Alloc-ID and LLID, the ONU may have a plurality of Alloc-ID and LLID.

An example of a PON system in which signals in an optical layer are time-division-multiplexed has been described, but a communication system that collects ONU uplink data by a switch or the like arranged between an OLT or an ONU-OLT, especially an uplink from multiple ONUs in an OLT. It is suitable for a system that controls the transmission time of uplink data in order to reduce delay fluctuations due to waiting between data.

The following additional notes are disclosed with respect to the communication system 1 shown in the present embodiment.
(Appendix 1)
In a communication system including a subscriber line termination device and a subscriber line end station device,
The subscriber line termination device
A queue of uplink data transmitted to the subscriber line end station device and
A congestion avoidance processing unit that discards the uplink data from the queue, and
With
The subscriber line end station device
A transmission permission unit that permits transmission of the uplink data using the allocation request amount declared by the subscriber line termination device, and
With
At least one of the subscriber line termination device and the subscriber line end station device controls transmission permission so that the difference between the amount of uplink data permitted for transmission at the time of transmission and the amount of uplink data in the queue does not become large. Equipped with a permit adjustment unit
A communication system characterized by that.
(Appendix 2)
The permission adjustment unit calculates the difference between the allocation request amount and the uplink data amount received from the subscriber line termination device as a difference prediction value, and uses the allocation request amount and the difference prediction value to the subscriber. Control the amount of transmission permission assigned to the line termination device,
The communication system according to Appendix 1.
(Appendix 3)
A queue of uplink data sent to the subscriber line end station device,
A congestion avoidance processing unit that discards the uplink data from the queue, and
It is provided with a permission adjusting unit that controls transmission permission so that the discrepancy between the amount of uplink data permitted for transmission at the time of transmission and the amount of uplink data in the queue does not become large.
A subscriber line terminating device characterized by that.
(Appendix 4)
A transmission permission unit that permits transmission of uplink data using the allocation request amount declared by the subscriber line termination device, and
It is provided with a permission adjusting unit for controlling transmission permission so that the difference between the amount of uplink data permitted to be transmitted at the time of transmission of the subscriber line termination device and the amount of uplink data in the queue of the uplink data does not become large.
A subscriber line end station device characterized by that.

Although the embodiments of the present invention have been described in detail with reference to the drawings, the specific configuration is not limited to this embodiment, and includes designs and the like within a range that does not deviate from the gist of the present invention.

The present invention is applicable to an optical access service that provides a user with an optical communication environment.

1 ... Communication system, 100 ... ONU, 101 ... 1st communication unit, 102 ... 2nd communication unit, 103 ... Frame storage unit, 104 ... Discard information storage unit, 105 ... Control unit, 106 ... Allocation request unit, 107 ... Congestion Avoidance processing unit, 108 ... Queue adjustment unit, 109 ... Declaration adjustment unit, 200 ... OLT, 201 ... 1st communication unit, 202 ... 2nd communication unit, 203 ... History information storage unit, 204 ... Control unit, 205 ... Transmission permission Unit, 206 ... Declaration adjustment unit, 207 ... Permit adjustment unit, 208 ... Queue adjustment unit, 300 ... ODN, 400 ... User device

Claims (4)

In a communication system including a subscriber line termination device and a subscriber line end station device,
The subscriber line termination device
A queue of uplink data transmitted to the subscriber line end station device and
A congestion avoidance processing unit that discards the uplink data from the queue, and
With
The subscriber line end station device
A transmission permission unit that permits transmission of the uplink data using the allocation request amount declared by the subscriber line termination device, and
With
At least one of the subscriber line termination device and the subscriber line end station device controls transmission permission so that the difference between the amount of uplink data permitted for transmission at the time of transmission and the amount of uplink data in the queue does not become large. Equipped with a permit adjustment unit
A communication system characterized by that. The permission adjustment unit calculates the difference between the allocation request amount and the uplink data amount received from the subscriber line termination device as a difference prediction value, and uses the allocation request amount and the difference prediction value to the subscriber. Control the amount of transmission permission assigned to the line termination device,
The communication system according to claim 1. A queue of uplink data sent to the subscriber line end station device,
A congestion avoidance processing unit that discards the uplink data from the queue, and
It is provided with a permission adjusting unit that controls transmission permission so that the discrepancy between the amount of uplink data permitted for transmission at the time of transmission and the amount of uplink data in the queue does not become large.
A subscriber line terminating device characterized by that. A transmission permission unit that permits transmission of uplink data using the allocation request amount declared by the subscriber line termination device, and
It is provided with a permission adjusting unit for controlling transmission permission so that the difference between the amount of uplink data permitted to be transmitted at the time of transmission of the subscriber line termination device and the amount of uplink data in the queue of the uplink data does not become large.
A subscriber line end station device characterized by that.

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