JP2023028711A - Buffer allocation device, subscriber line terminal device, buffer allocation method and program - Google Patents

Abstract

To mount a device for buffering transmission data at a lower cost.SOLUTION: A buffer allocation device includes an acquisition unit that acquires request buffer amounts requested for a plurality of queues, and a setting unit for converting a request buffer amount for each queue into a first lowest conversion buffer amount based on a lowest data accommodation efficiency that may occur in a first storage unit, allocating a buffer amount calculated based on the first lowest conversion buffer amount and a lowest required buffer amount per cycle of dynamic bandwidth allocation to a queue having the lowest priority, and allocating a buffer amount calculated based on a first buffer amount which is a buffer amount obtained by subtracting the buffer amount allocated to the lowest priority queue from the total capacity of the first storage unit for queues other than the lowest priority queue, and a second buffer amount which is the total of the first lowest conversion butter amounts of the queues other than the lowest priority queue.SELECTED DRAWING: Figure 2

Description

The present invention relates to a buffer allocation device, a subscriber line terminal device, a buffer allocation method and a program.

FTTH (Fiber To The Home) has become popular worldwide in response to the growing need for high-speed access services. Mainstay FTTH services in Japan include, for example, GE-PON (Gigabit Ethernet PON) and 10G-EPON (10 Gigabit Ethernet PON), which realize gigabit-class transmission speeds.

In GE-PON and 10G-EPON, TDMA (Time Division Multiple Access) technology is used in upstream communication from ONUs to OLTs. Also, one of the functions required to operate GE-PON and 10G-EPON as a system is a DBA (Dynamic Bandwidth Allocation) function. The DBA function is a bandwidth control function that dynamically allocates bandwidth in upstream communication according to traffic volume. The DBA function realizes efficient upstream bandwidth without generating unused bandwidth by appropriately switching the allocated bandwidth according to the status of upstream communication traffic flowing through each ONU.

In the DBA function, each ONU notifies the OLT of the amount of uplink data waiting for transmission accumulated in the uplink transmission buffer by means of a REPORT frame. On the other hand, based on the received REPORT frame, the OLT uses the GATE frame to set the transmission start time and transmission permission amount of the upstream data to each ONU so that each ONU can transmit the upstream data without time collision. Instruct the ONU. Each ONU transmits uplink data based on the transmission permission amount at the transmission start time indicated by the GATE frame. In this way, the DBA function is realized by exchanging data using the GATE frame and the REPORT frame.

"Technical Basic Lecture [GE-PON Technology] 4th. Systemization Function of GE-PON", NTT Technical Journal, pp. 59-61, November 2005

By the way, when providing multiple services to one user, for example, in order to ensure service quality when quality assurance type communication such as VoIP (Voice over Internet Protocol) and video distribution are multiplexed, a priority control function is required. (see Non-Patent Document 1). With the priority control function, it is possible to preferentially transmit data in order of importance. It becomes possible to ensure the quality of high-priority service.

In general, ONUs perform priority control for transmission of uplink data. ONUs require a large amount of buffers in order to control the transmission timing of upstream data. Therefore, the ONU has an upstream transmission buffer (hereinafter referred to as "internal buffer") for temporarily storing upstream data in its internal PON chip. This built-in buffer also has a plurality of upstream transmission queues. The PON chip referred to here is an LSI (Large Scale Integration) of the main functions of the ONU for cost reduction.

However, even then, there are cases where the buffer capacity is insufficient only with the built-in buffer mounted on the PON chip. In this case, it is necessary to add an external upstream transmission buffer (hereinafter referred to as an "external buffer") such as a DDR SDRAM (Double-Data-Rate Synchronous Dynamic Random Access Memory) to form a two-stage buffer configuration. be. This external buffer is also configured to have a plurality of upstream transmission queues. Each upstream transmission queue of the built-in buffer and each upstream transmission queue of the external buffer are associated with each other on a one-to-one basis. Due to the two-stage buffer configuration, buffering is performed in the external buffer even when there is no free space in the built-in buffer, so that the occurrence of buffer overflow can be prevented.

However, conventionally, in such a two-stage buffer, a setting method for setting a necessary and sufficient buffer amount for each buffer has not been clearly shown. Therefore, in order to prevent a state in which the entire set buffer size cannot be allocated to the internal buffer (hereafter referred to as "oversubscription"), the buffer size of the external buffer should be set with a margin. had to be able to As a result, there is a problem that the device cost of the transmission buffer increases.

The present invention has been made in view of the above points, and provides a buffer allocation device, a subscriber line terminal device, a buffer allocation method, and a program that can implement equipment for buffering transmission data at a lower cost. intended to provide

According to one aspect of the present invention, an acquisition unit acquires information indicating a request buffer amount for each of a plurality of queues, and the request buffer amount for each queue is determined based on the lowest possible data accommodation efficiency in a first storage unit. to the first minimum converted buffer amount, and for the queue with the lowest priority in the first storage unit, the first minimum converted buffer amount and the minimum per cycle of the dynamic bandwidth allocation function allocate a buffer amount calculated based on the required buffer amount, and assign a buffer amount calculated based on the total capacity of the first storage unit to the queues other than the queue with the lowest priority in the first storage unit from the total capacity of the first storage unit. a first buffer amount, which is a buffer amount obtained by subtracting the buffer amount assigned to the queue with the lowest priority in the storage unit; A buffer allocation device comprising: a second buffer amount that is the sum of minimum converted buffer amounts; and a setting unit that allocates a buffer amount calculated based on.

Further, one aspect of the present invention is an acquisition unit that acquires information indicating a request buffer amount for each of a plurality of upstream transmission queues, The first minimum converted data length is converted based on the efficiency, and the first minimum converted data length and the dynamic bandwidth allocation function per cycle for the uplink transmission queue with the lowest priority of the built-in buffer and the minimum required buffer size, and assigning the built-in buffer from the total capacity of the built-in buffer to an uplink transmission queue other than the uplink transmission queue with the lowest priority of the built-in buffer. a first buffer amount that is a buffer amount obtained by subtracting a buffer amount allocated to the uplink transmission queue with the lowest priority of the built-in buffer; A subscriber line terminal equipment comprising: a second buffer amount that is the sum of minimum converted buffer amounts;

According to another aspect of the present invention, an obtaining step of obtaining information indicating a request buffer capacity for each of a plurality of queues; is converted into the first minimum converted buffer amount based on the above, and for the queue with the lowest priority in the first storage unit, the first minimum converted buffer amount and per cycle of the dynamic bandwidth allocation function and the minimum required buffer capacity, and assigns the buffer capacity calculated based on the minimum required buffer capacity to the queues other than the queue with the lowest priority in the first storage section from the total capacity of the first storage section. A first buffer amount, which is a buffer amount obtained by subtracting a buffer amount assigned to the queue with the lowest priority in the first storage unit, and a buffer amount of the queues other than the queue with the lowest priority in the first storage unit and a setting step of allocating a buffer amount calculated based on a second buffer amount that is the sum of the first minimum converted buffer amounts.

Another aspect of the present invention is a program for causing a computer to function as the above buffer allocation device.

The invention allows equipment for buffering transmitted data to be implemented at a lower cost.

1 is an overall configuration diagram of PON 1 in an embodiment of the present invention; FIG. It is a block diagram which shows the structure of ONU20 in embodiment of this invention. FIG. 10 is a diagram for explaining the process of setting an uplink transmission buffer by the ONU 20 according to the embodiment of the present invention; FIG. 10 is a diagram for explaining the process of setting an uplink transmission buffer by the ONU 20 according to the embodiment of the present invention; FIG. 10 is a diagram for explaining the process of setting an uplink transmission buffer by the ONU 20 according to the embodiment of the present invention; 4 is a flow chart showing an example of the operation of the ONU 20 according to the embodiment of the present invention;

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[PON configuration]
A PON (Passive Optical Network) is an optical access system that provides FTTH services at high speed and at low cost. A PON does not perform optical-to-electrical conversion, but uses low-cost passive optical splitters to split an optical signal into multiple parts. As a result, the PON can realize an economical network by sharing one optical fiber with a plurality of users. Mainstay FTTH services in Japan include, for example, GE-PON, which achieves gigabit-class transmission speeds, and 10G-EPON, which has ten times the bandwidth of GE-PON.

The overall configuration of the PON 1 according to this embodiment will be described below. FIG. 1 is an overall configuration diagram of a PON 1 according to an embodiment of the invention. As shown in FIG. 1, the PON 1 includes an OLT (Optical Line Terminal; subscriber line terminal equipment) 10 and a plurality of (n units in FIG. 1) ONUs (optical network units; subscriber line terminal equipment). 20 , an optical fiber 30 and an optical splitter 40 .

The OLT 10 is installed, for example, in the office of a telecommunications carrier. The ONU 20 is installed, for example, in the user's home (or premises). The optical fiber 30 is laid, for example, between the station office of the telecommunications carrier and the user's home. The optical splitter 40 splits the optical fiber 30 . A plurality of ONUs 20 are connected to one OLT 10 by installing an optical splitter 40 that multiplexes and demultiplexes optical signals between the OLT 10 and the ONUs 20 .

The OLT 10 receives the optical signal transmitted from the ONU 20 and transfers it to a host device or a host network (for example, the Internet, etc.). Also, the OLT 10 receives signals from a host device or a host network and transfers them to each ONU 20 . The OLT 10 plays a role of controlling and monitoring the PON section and the ONU 20 .

The ONU 20 receives the optical signal transmitted from the OLT 10 and converts it into an electrical signal. The ONU 20 then transfers the converted electrical signal to the user's terminal device (for example, PC or the like). The ONU 20 also receives an electrical signal transmitted from a user's terminal device and converts it into an optical signal. The ONU 20 then transfers the converted optical signal to the OLT 10 .

In the PON 1, TDM (Time Division Multiplexing) technology is used in communication from the OLT 10 to the ONU 20 (hereinafter referred to as "downlink communication"). TDM is a technique for multiplexing and transmitting signals of a plurality of users so that they do not overlap in time.

In downstream communication, the same signal transmitted from the OLT 10 and split by the optical splitter 40 (hereinafter referred to as “downstream signal”) is transferred to all the ONUs 20 connected to the OLT 10 . That is, each ONU 20 is also transferred with data other than the data addressed to its own ONU 20 . Therefore, each ONU 20 extracts only the data addressed to its own ONU 20 from the transferred data, and discards the other data (addressed to other ONUs 20).

Also, in the PON 1, the TDMA technology is used in communication from the ONU 20 to the OLT 10 (hereinafter referred to as "uplink communication"). In upstream communication, signals from a plurality of ONUs 20 (hereinafter referred to as “upstream signals”) are multiplexed by the optical splitter 40 . Therefore, if the upstream signals from the ONUs 20 are randomly transmitted, there is a possibility that they will collide on the optical fiber 30 . Therefore, the TDMA controls the transmission timing of upstream signals from the ONUs 20 and the transmission amount of upstream data so that the upstream signals from each ONU 20 are multiplexed on the optical fiber 30 without collision. .

A DBA function is one of the functions required to operate GE-PON and 10G-EPON as a system. The DBA function is a bandwidth control function that dynamically allocates bandwidth in upstream communication (hereinafter referred to as "upstream bandwidth") according to traffic volume. The DBA function can flexibly allocate an upstream bandwidth according to the traffic of upstream communication from each ONU 20 (hereinafter referred to as "upstream traffic"). Since the DBA function allocates the upstream bandwidth only to the ONUs 20 in which upstream traffic is flowing, the upstream bandwidth can be used without waste. The DBA function appropriately switches the bandwidth to be allocated according to the status of upstream traffic flowing through each ONU 20, thereby realizing efficient upstream bandwidth without generating unused bandwidth.

GE-PON and 10G-EPON control the transmission of upstream signals using a protocol called MPCP (Multi Point Control Protocol). The OLT 10 instructs each ONU 20 of the upstream signal transmission start time and transmission permission amount using the GATE frame so that each ONU 20 can transmit the upstream signal without time collision.

On the other hand, each ONU 20 notifies the OLT 10 of the amount of uplink data waiting for transmission accumulated in the uplink transmission buffer of its own ONU 20 by means of a REPORT frame. The DBA function is realized by using the GATE frame and the REPORT frame.

The mechanism of the DBA function will be briefly described below. When the ONU 20 receives the upstream data, it temporarily stores the upstream data in the upstream transmission buffer. The ONU 20 writes the amount of accumulated upstream data in a REPORT frame and transmits the REPORT frame to the OLT 10 .

From the received REPORT frame, the OLT 10 grasps the data amount of the uplink data waiting for transmission accumulated in the ONU 20 . The OLT 10 calculates the upstream bandwidth to be allocated to the ONU 20 based on the accumulated data amount of the ONU 20 and the usage bandwidth of the other ONUs 20 . Specifically, the OLT 10 calculates the transmission start time and the transmission permission amount of the upstream signal of the ONU 20 . The OLT 10 writes the calculated value in the GATE frame and transmits the GATE frame to the ONU 20 .

The ONU 20 transmits a designated amount of data (permitted transmission amount) of uplink data at a designated transmission start time according to the instructions written in the received GATE frame. At this time, the ONU 20 may re-notify the OLT 10 of the amount of uplink data accumulated in the uplink transmission buffer for the next uplink bandwidth allocation.

By repeating the above procedure, the OLT 10 can grasp the status of upstream traffic in each ONU 20 and appropriately allocate an upstream bandwidth to each ONU 20 according to the status.

[Configuration of ONU]
The configuration of the ONU 20 in this embodiment will be described below. FIG. 2 is a block diagram showing the configuration of the ONU 20 according to the embodiment of the invention. As shown in FIG. 2, the ONU 20 includes a TRx 21, a MAC processing unit 22, a PHY 23, and an external buffer 24. FIG.

A TRx (Transmitter/Receiver) 21 is an optical transmitter/receiver that transmits and receives optical signals between its own device and the OLT 10 . The TRx 21 converts the digital data (electrical signal) for upstream transmission output from the MAC processing unit 22 into an optical signal (upstream signal) and outputs the optical signal (upstream signal) to the optical fiber 30, and also converts the optical signal (downstream signal) transmitted from the OLT 10 into an optical signal (upstream signal). ), converts the received optical signal into digital data (electrical signal), and outputs it to the MAC processing unit 22 .

A MAC (Media Access Control) processing unit 22 is a functional unit of the data link sublayer that controls transmission and reception of data. The MAC processing unit 22 is generally configured using a PON chip. The MAC processing section 22 includes a buffer setting section 220 and an internal buffer 221 . The buffer setting unit 220 sets the buffer amounts of the internal buffer 221 and the external buffer 24 . In the following description, the built-in buffer 221 and the external buffer 24 may be collectively referred to as "upstream transmission buffer".

The internal buffer 221 and the external buffer 24 are configured using a storage medium such as a magnetic hard disk device or a semiconductor storage device. The built-in buffer 221 and the external buffer 24 accumulate upstream data received by the PHY 23 . The internal buffer 221 and the external buffer 24 each have a plurality of upstream transmission queues. In the following description, the upstream transmission queue of the internal buffer 221 may be called "internal queue", and the upstream transmission queue of the external buffer 24 may be called "external queue".

A PHY (PHYsical sublayer) 23 is a functional part of the physical layer. The PHY 23 is a communication interface that connects its own device and lower devices (for example, user communication terminals, etc.). The PHY 23 acquires an analog signal transmitted from a lower-level device, converts it into a digital signal, and outputs the converted digital signal to the MAC processing unit 22 . Also, the PHY 23 acquires the digital signal output from the MAC processing unit 22, converts it into an analog signal, and transmits the converted analog signal to the lower apparatus.

[How to set up transmission buffer]
Hereinafter, a method for setting up transmission buffers by the ONU 20 in this embodiment will be described using a specific example. 3 to 5 are diagrams for explaining the setting processing of the upstream transmission buffer by the ONU 20 according to the embodiment of the present invention.

Here, it is assumed that the built-in buffer 221 and the external buffer 24 of the ONU 20 each have four upstream transmission queues. As shown in FIG. 3, the internal buffer 221 and the external buffer 24 each have four upstream transmission queues from upstream transmission queue #0 to upstream transmission queue #3. Here, uplink transmission queue #3 has the highest priority, followed by uplink transmission queue #2 and uplink transmission queue #1, and uplink data is stored in the uplink transmission queues in this order. shall be Then, the ONU 20 transmits the upstream data stored in the transmission queue #3 with the highest priority, transmits the upstream data stored in the transmission queue #2 after the queue becomes empty, and then similarly transmits the upstream data stored in the transmission queue #3. Uplink data is transmitted in order of #1 and transmission queue #0.

Hereinafter, upstream transmission queue #0 to upstream transmission queue #3 of internal buffer 221 are referred to as internal queue q#0 to internal queue q#3, respectively, and upstream transmission queue #0 to upstream transmission queue #3 of external buffer 24 are referred to as internal queue q#0 to internal queue q#3. They are referred to as an external queue Q#0 to an external queue Q#3, respectively.

The buffer setting unit 220 stores in the external queue Q#0 the upstream data that did not fit within the buffer capacity allocated to the internal queue q#0. Similarly, the buffer setting unit 220 stores the upstream data that did not fit within the buffer amount assigned to the internal queue q#1 in the external queue Q#1, and stores the upstream data in the external queue Q#1. Upstream data that does not fit within the buffer amount range is stored in the external queue Q#2, and upstream data that does not fit within the buffer amount assigned to the built-in queue q#3 is stored in the external queue Q#3. do. In this way, the built-in queue q#n and the external queue Q#n are two-stage buffers corresponding to each other, and each upstream data is temporarily stored by this set of upstream transmission queues.

First, the buffer setting unit 220, in accordance with an instruction from a predetermined equipment and line maintenance and monitoring function (for example, an extended OAM (Operation, Administration, and Maintenance) function), stores the built-in queue q#0 to built-in queue q#3. (hereinafter simply referred to as "desired buffer size").

Here, as shown in FIG. 3, the buffer size to be set for the built-in queue q#0 is 600 [KB], the buffer size to be set for the built-in queue q#1 is 300 [KB], and the built-in queue q Assume that the buffer size to be set for #2 is 200 [KB] and the buffer size to be set for internal queue q#3 is 100 [KB].

Next, the buffer setting unit 220 sets the buffer amount to be set for each of the determined built-in queues q#0 to q#3 to a buffer amount corresponding to the data length that provides the minimum accommodation efficiency in the built-in buffer 221. Convert. The data length at which the minimum accommodation efficiency is used here is the data length at which the buffer unused area becomes the largest when the upstream data is accommodated in the upstream transmission queue. The buffer setting unit 220 determines the converted buffer amount as the buffer amount of uplink data to be secured in each of the built-in queues q#0 to q#3 (hereinafter, also simply referred to as "the secured buffer amount"). do.

Here, it is assumed that the minimum accommodation efficiency in the built-in buffer 221 is 1/1.5. Therefore, the amount of buffer to be secured in the internal queue q#0 is 900 [KB] (=600*1.5), and the amount of buffer to be secured in the internal queue q#1 is 450 [KB] (=300*1.5). 5), the amount of buffer to be secured in the internal queue q#2 is 300 [KB] (=200*1.5), and the amount of buffer to be secured in the internal queue q#3 is 150 [KB] (=100*1.5). 1.5).

Next, the buffer setting unit 220 calculates the minimum required buffer amount per cycle of the DBA function. The reason why the minimum amount of buffer required per cycle of the DBA function is calculated is that the upstream data can only be output from the built-in buffer 221 per cycle. This is due to the constraint of That is, the buffer setting unit 220 calculates a buffer amount corresponding to the maximum uplink data transmission permission amount (Data Grant) that can be granted by the OLT 10 per cycle of the DBA function (similarly to the above, the buffer The setting unit 220 converts the data length into a buffer amount corresponding to the minimum accommodation efficiency of the built-in buffer 221).

Here, it is assumed that the buffer amount corresponding to the data length of the maximum amount of transmission permission (Data Grant) of uplink data that can be granted is 525 [KB].

Next, the buffer setting section 220 allocates a buffer amount so that the built-in queue q#0, which is the uplink transmission queue with the lowest priority, has the maximum uplink rate. Specifically, the buffer setting unit 220 sets the calculated buffer amount to be secured in the built-in queue q#0 (hereinafter also referred to as "buffer amount A") and the calculated maximum upload data that can be added. is compared with a buffer amount (hereinafter also referred to as “buffer amount B”) corresponding to the data length that is the minimum accommodation efficiency in the built-in buffer 221 for the transmission permission amount (Data Grant). If the buffer amount A is larger than the buffer amount B, the buffer setting unit 220 sets so that the buffer amount B is allocated to the built-in queue q#0. On the other hand, if the buffer amount A is less than or equal to the buffer amount B, the buffer setting unit 220 sets so that the buffer amount A is allocated to the built-in queue q#0.

Here, as described above, the buffer amount A is 900 [KB] and the buffer amount B is 525 [KB]. Since the buffer amount A is larger than the buffer amount B, a buffer amount (buffer amount B) of 525 [KB] is allocated to the built-in queue q#0 as shown in FIG.

Next, the buffer setting section 220 calculates the amount of buffer actually allocated to the external queue Q#0. Specifically, when the buffer amount B is allocated to the built-in queue q#0 in the above description, the buffer setting unit 220 sets the buffer amount reserved for the built-in queue q#0 to the built-in queue q#0. allocates to the external queue Q#0 the amount of buffer that could not be set due to the setting of the buffer amount for the external queue Q#0 (the buffer setting unit 220 sets the buffer size corresponding to the data length that is the minimum accommodation efficiency in the external buffer 24). amount).

Here, as described above, a buffer amount of 525 [KB] is allocated to the built-in queue q#0. Since this buffer amount of 525 [KB] corresponds to the data length that is the minimum accommodation efficiency of the built-in buffer 221, A buffer amount of 350 [KB] (=525/1.5) is allocated to the built-in queue q#0. Therefore, it is necessary to allocate the remaining 250 [KB] (=600-350) of the buffer size of 600 [KB] initially set for the internal queue q#0 to the external queue Q#0. be.

Here, it is assumed that the minimum accommodation efficiency in the external buffer 24 is 1/1.2. Therefore, as shown in FIG. 3, a buffer amount of 300 [KB] (=250×1.2) is allocated to the external queue Q#0.

Next, the buffer setting unit 220 subtracts the buffer amount allocated to the internal queue q#0 from the total capacity of the internal buffers 221 (internal queue q#0 to internal queue q#3) (hereinafter also referred to as "buffer amount X") and the total amount of buffers secured in built-in queues q#1 to q#3, which are built-in queues other than the built-in queue q#0 with the lowest priority (hereinafter , also referred to as “buffer amount Y”), it is determined whether or not oversubscription can occur.

For example, if the internal queue q#0 to internal queue q#2 have all used up the total capacity of the internal buffer 221, the buffer capacity of the internal queue q#3 is 0 [KB]. In this case, even if the upstream data of the internal queue q#3 is acquired, the internal queue q#3 cannot store the upstream data. As a result, oversubscription of the upstream data occurs in the built-in buffer, and data that cannot be stored is stored in the external buffer.

Next, when the buffer amount X is larger than the buffer amount Y, the buffer setting section 220 sets the internal queues q#1 to q#3 to the internal queues q#1 to q#3, respectively. Allocate the amount of buffer to be secured to #3. On the other hand, when the buffer amount X is less than or equal to the buffer amount Y, the buffer setting unit 220 distributes the buffer amount X to the built-in queues q#1 to q#3 according to the desired buffer amount ratio. , to the built-in queue q#1 to built-in queue q#3. As described above, by distributing the buffer amount X to the built-in queues q#1 to q#3 according to the ratio of the desired buffer amounts, oversubscription of upstream data in the built-in buffer can be avoided.

Here, as shown in FIG. 4, it is assumed that the total capacity of the built-in buffer 221 (built-in queue q#0 to built-in queue q#3) is 1 [MB] (=1,024 [KB]). As described above, a buffer amount of 525 [KB] is allocated to the built-in queue q#0. Therefore, the buffer capacity (that is, buffer capacity X) that can be allocated to the internal queues q#1 to q#3 is the remaining 499 [KB] (=1,024-525).

Further, as shown in FIG. 4, the buffer amounts required for the built-in buffers Q#1 to Q#3 are 450 [KB], 300 [KB], and 150 [KB], respectively. Therefore, the sum of these buffer amounts (that is, buffer amount Y) is 900 [KB], which exceeds 499 [KB]. Therefore, since the buffer amount X is equal to or smaller than the buffer amount Y, it is determined that oversubscription may occur, and a buffer amount of 499 [KB] is allocated to each of the built-in queues q#1 to q#3. It is distributed according to the ratio of the buffer amount to be set and assigned to each of the built-in queues q#1 to q#3.

Specifically, as shown in FIG. 4, a buffer capacity of 249 [KB] (≈499×300/(300+200+100)) is allocated to the built-in queue q#1, and 166 [KB] is allocated to the built-in queue q#2. KB] (≈499×200/(300+200+100)) is allocated, and a buffer size of 83 [KB] (≈499×100/(300+200+100)) is allocated to the built-in queue q#3.

Next, the buffer setting section 220 calculates the amount of buffer to be allocated to each of the external queues Q#1 to Q#3. Specifically, when the buffer amount X is less than or equal to the buffer amount Y in the above description, the buffer setting unit 220 selects the above The amount of buffer that could not be set for the internal queues q#1 to q#3 is allocated to the external queues Q#1 to Q#3 (the buffer setting unit 220 is converted into a buffer amount corresponding to the data length that is the minimum accommodation efficiency in the external buffer 24).

Here, as described above, a buffer amount of 249 [KB] is allocated to the built-in queue q#1. Since this 249 [KB] is the physical size, 166 [KB] (≈ 249 ÷ 1.5) of the 300 [KB] buffer capacity to be initially set for the built-in queue q#1 is equivalent to the built-in queue size. It is assigned to q#1. Therefore, it is necessary to allocate the remaining 134 [KB] (=300-166) of the buffer size of 300 [KB] desired to be initially set for the internal queue q#1 to the external queue Q#1. be.

Here, as described above, the minimum accommodation efficiency in the external buffer 24 is 1/1.2. Therefore, as shown in FIG. 5, a buffer amount of 161 [KB] (≈134×1.2) is allocated to the external queue Q#1.

Also, here, as described above, a buffer amount of 166 [KB] is allocated to the built-in queue q#2. Since this buffer amount of 166 [KB] is equivalent to the data length at which the built-in buffer 221 has the minimum accommodation efficiency, A buffer amount of 111 [KB] (≈166÷1.5) is allocated to the built-in queue q#2. Therefore, it is necessary to allocate the remaining 89 [KB] (=200-111) of the buffer size of 200 [KB] initially set for the internal queue q#2 to the external queue Q#2. be.

Here, as described above, the minimum accommodation efficiency in the external buffer 24 is 1/1.2. Therefore, as shown in FIG. 5, a buffer amount of 107 [KB] (≈89×1.2) is allocated to the external queue Q#2.

Also, here, as described above, a buffer amount of 83 [KB] is allocated to the built-in queue q#3. Since this buffer amount of 83 [KB] corresponds to the data length that is the minimum accommodation efficiency of the built-in buffer 221, A buffer amount of 55 [KB] (≈83÷1.5) is allocated to the built-in queue q#3. Therefore, it is necessary to allocate the remaining 45 [KB] (=100-55) of the buffer size of 100 [KB] initially set for the internal queue q#3 to the external queue Q#3. be.

Here, as described above, the minimum accommodation efficiency in the external buffer 24 is 1/1.2. Therefore, as shown in FIG. 5, a buffer amount of 54 [KB] (=45×1.2) is allocated to the external queue Q#3.

[Operation of ONU]
The operation of the ONU 20 in this embodiment when setting up the upstream transmission buffer will be described below. FIG. 6 is a flow chart showing an example of the operation of the ONU 20 according to the embodiment of the invention. Here, it is assumed that the built-in buffer 221 and the external buffer 24 each have n (n is an integer equal to or greater than 1) upstream transmission queues.

First, the buffer setting unit 220 determines the amount of buffer to be set for each of the built-in queues q#0 to q#n-1 based on the upstream data acquired from the PHY 23 (step S01).

Next, the buffer setting unit 220 sets the buffer amount to be set for each of the built-in queues q#0 to q#n−1 determined in step S01 to correspond to the data length that provides the minimum accommodation efficiency in the built-in buffer 221. It converts to the amount of buffer to be used (step S02). The buffer setting unit 220 determines the converted buffer capacity as the buffer capacity to be reserved for each of the built-in queues q#0 to q#n−1.

Next, the buffer setting unit 220 calculates the minimum required buffer amount per cycle of the DBA function (step S03).

Next, the buffer setting unit 220 sets the buffer amount so that the built-in queue q#m (m is an integer satisfying 0≤m≤n-1), which is the upstream transmission queue with the lowest priority, has the maximum upstream rate. assign. Specifically, the buffer setting unit 220 sets the calculated buffer amount (buffer amount A) to be secured in the built-in queue q#m and the calculated maximum grantable uplink data transmission permission amount (Data Grant ) is compared with the buffer amount (buffer amount B) corresponding to the data length at which the built-in buffer 221 has the minimum accommodation efficiency. If the buffer amount A is larger than the buffer amount B, the buffer setting unit 220 sets so that the buffer amount B is allocated to the built-in queue q#m. On the other hand, if the buffer amount A is less than or equal to the buffer amount B, the buffer setting unit 220 sets so as to allocate the buffer amount A to the built-in queue q#m (step S04).

Next, the buffer setting unit 220 determines whether or not it is necessary to allocate a buffer amount to the external queue Q#m corresponding to the internal queue q#m, which is the uplink transmission queue with the lowest priority (step S05). . Specifically, the buffer setting unit 220 has a buffer amount that could not be set by setting the buffer amount for the built-in queue q#m in step S04, out of the buffer amount to be secured for the built-in queue q#m. (that is, when the internal queue q#m is allocated the buffer amount B), it is determined that it is necessary to allocate the buffer amount to the external queue Q#m.

If it is determined that it is necessary to allocate a buffer amount to the external queue Q#m (step S05: YES), the buffer setting unit 220 assigns The amount of buffer that could not be set due to the setting of the buffer amount for q#0 is allocated to the external queue Q#0 (step S06).

Next, the buffer setting unit 220 subtracts the buffer capacity allocated to the built-in queue q#m from the total capacity of the built-in buffers 221 (built-in queue q#0 to built-in queue q#n−1). Whether or not oversubscription can occur is determined by comparing the buffer amount (buffer amount X) with the total buffer amount (buffer amount Y) secured in the built-in buffers other than the built-in queue q#m with the lowest priority. (step S07).

Next, if the buffer amount X is greater than the buffer amount Y (that is, if it is determined that oversubscription does not occur; step S07: NO), the buffer setting unit 220 A desired buffer amount (that is, a buffer amount to be secured for each built-in queue other than the built-in queue q#m) is allocated to each built-in queue (step S08).

On the other hand, if the buffer amount X is equal to or less than the buffer amount Y (that is, if it is determined that oversubscription may occur; step S07: YES), the buffer setting unit 220 sets the buffer amount X to the built-in The amount of buffer is distributed to each built-in queue other than the queue q#m according to the ratio of the desired buffer amount, and allocated to each built-in queue other than the built-in queue q#m (step S09).

Next, the buffer setting unit 220 calculates the amount of buffer to be allocated to each external queue other than the external queue Q#m. Specifically, when the buffer amount X is equal to or smaller than the buffer amount Y in the above (step S07: YES), the buffer setting unit 220 sets the buffer amount to be reserved for each external queue other than the external queue Q#m. Of these, the amount of buffer that could not be set by setting the buffer amount for each internal queue other than the internal queue q#m is allocated to each external queue other than Q#m (the buffer setting unit 220 is converted into a buffer amount corresponding to the data length that is the minimum accommodation efficiency in the external buffer 24) (step S10). With this, the operation of the ONU 20 shown in the flowchart of FIG. 6 is completed.

As described above, the ONU 20 in this embodiment converts the buffer amount to be set for each upstream transmission queue into the buffer amount when the built-in buffer 221 achieves the minimum accommodation efficiency. First, the ONU 20 preferentially assigns the built-in buffer 221 to the upstream transmission queue with the lowest priority. At this time, if the buffer size to be set is larger than the minimum required buffer size per cycle of the DBA function, the ONU 20 allocates the minimum required buffer size to the built-in buffer 221 and removes the remaining buffer size. allocated to the attachment buffer 24.

With such a configuration, the ONU 20 in this embodiment can appropriately set the buffer amount of the two-stage upstream transmission buffer. Specifically, the external buffer 24 stores upstream data that cannot fit in the built-in buffer 221 . Then, while allocating a sufficient amount of buffer to the upstream transmission queue #0, which is assumed to be the best effort class and is the class that requires the largest amount of buffer, the upstream transmission that is assumed to be the bandwidth guarantee class. By securing only the amount of data guaranteed per cycle of the DBA function in queues #1 to #3 in the internal buffer 221, upstream data can be transmitted efficiently based on priority. The best-effort class referred to here is a quality class for providing communication services that give priority to economic efficiency and flexibility similar to those of the general Internet. The bandwidth guarantee class referred to here is a priority class, and is a quality class suitable for providing communication services that require real-time performance, such as videophone and video distribution. As a result, according to the ONU 20 of the present embodiment, it is possible to use a combination of low-cost, low-capacity buffers, so that a configuration that satisfies the required performance of the ONU 20 can be obtained at a lower cost. Therefore, according to the ONU 20 of this embodiment, a device for buffering transmission data can be implemented at a lower cost.

Also, as described above, the ONU 20 in this embodiment allocates the remaining buffer capacity to the uplink transmission queues other than the uplink transmission queue with the lowest priority. At this time, if the amount of buffer to be set exceeds the total capacity of the built-in buffer 221, oversubscription may occur. Allocate a buffer volume to each, dividing the remaining total capacity by a volume ratio.

By providing such a configuration, the ONU 20 in this embodiment can prevent oversubscription and suppress an increase in the amount of buffer required for the external buffer 24 .

According to the embodiments described above, the buffer allocation device comprises an obtaining unit and a setting unit.
For example, the buffer allocation device is the ONU 20 or the MAC processing unit 22 in the embodiment, the acquisition unit is part of the MAC processing unit 22 in the embodiment, and the setting unit is the buffer setting unit 220 in the embodiment. The acquisition unit acquires information indicating the request buffer capacity for each of the plurality of queues. For example, the plurality of queues are upstream transmission queue #0 to upstream transmission queue #n in the embodiment, and the request buffer capacity is the amount of upstream data to be set in built-in queue q#0 to built-in queue q#n in the embodiment. is the amount of buffer.

The setting unit converts the requested buffer amount for each queue into a first minimum converted buffer amount based on the lowest possible data accommodation efficiency in the first storage unit. For example, the first storage unit is the built-in buffer 221 in the embodiment, and the first minimum converted buffer capacity is the buffer capacity corresponding to the data length that provides the minimum accommodation efficiency in the built-in buffer 221 in the embodiment. The setting unit calculates for the queue with the lowest priority in the first storage unit based on the first minimum conversion buffer amount and the minimum required buffer amount per cycle of the dynamic bandwidth allocation function. Allocate a buffer amount. For example, the queue with the lowest priority in the first storage unit is the built-in queue q#0 in the embodiment, and the dynamic bandwidth allocation function is the DBA function in the embodiment. The setting unit assigns a buffer to the queue with the lowest priority in the first storage unit from the total capacity of the first storage unit for the queues other than the queue with the lowest priority in the first storage unit. Calculated based on the first buffer amount, which is the buffer amount after subtracting the buffer amount, and the second buffer amount, which is the sum of the first minimum converted buffer amounts of the queues other than the queue with the lowest priority in the first storage unit allocates the amount of buffer For example, queues other than the queue with the lowest priority in the first storage unit are built-in queue q#1 to built-in queue q#n in the embodiment.

In the buffer allocation device described above, the setting unit assigns the first lowest conversion buffer if the first buffer amount is larger than the second buffer amount for the queues other than the lowest priority queue in the first storage unit. If the first buffer size is equal to or less than the second buffer size, the second buffer size is distributed according to the ratio of the requested buffer size of the queue other than the queue with the lowest priority in the first storage unit. You may make it each allocate an amount.

In the buffer allocation device described above, the setting unit compares the first minimum converted buffer amount with the required buffer amount indicating the minimum required buffer amount per cycle of the dynamic bandwidth allocation function, and determines the first minimum converted buffer amount. If the buffer amount is larger than the required buffer amount, the required buffer amount is assigned to the queue with the lowest priority in the first storage unit. The first minimum converted buffer amount may be assigned to the queue with the lowest priority in the storage unit. For example, the required buffer amount is the buffer amount corresponding to the data length corresponding to the maximum uplink data transmission permission amount (Data Grant) that can be given by the OLT 10 per cycle of the DBA function in the embodiment.

In the buffer allocation device described above, the setting unit determines the amount of buffers not set in the queue with the lowest priority in the first storage unit based on the lowest possible data accommodation efficiency in the second storage unit. may be converted into a second minimum converted buffer amount by , and the second minimum converted buffer amount may be allocated to the queue with the lowest priority in the second storage unit. For example, the second storage unit is the external buffer 24 in the embodiment, and the second minimum converted buffer amount is the buffer amount corresponding to the data length that is the minimum accommodation efficiency in the external buffer 24 in the embodiment. , the queue with the lowest priority in the second storage unit is the external queue Q#0 in the embodiment.

In the buffer allocation device described above, the setting unit assigns the amount of buffers not set in the queues other than the lowest priority queue of the first storage unit to the lowest possible data accommodation in the second storage unit. The efficiency may be converted into a second minimum converted buffer amount, and the second minimum converted buffer amount may be allocated to queues other than the queue with the lowest priority in the second storage unit. For example, queues other than the queue with the lowest priority in the second storage unit are external queue Q#1 to external queue Q#n-1 in the embodiment.

A part or all of the ONU 20 in the above-described embodiment may be realized by a computer. In that case, a program for realizing this function may be recorded in a computer-readable recording medium, and the program recorded in this recording medium may be read into a computer system and executed. It should be noted that the "computer system" referred to here includes the OS and hardware of peripheral devices. The term "computer-readable recording medium" refers to portable media such as flexible disks, magneto-optical disks, ROMs and CD-ROMs, and recording devices such as hard disks built into computer systems. Furthermore, "computer-readable recording medium" means a medium that dynamically retains a program for a short period of time, like a communication line when transmitting a program via a network such as the Internet or a communication line such as a telephone line. It may also include something that retains the program for a certain period of time, such as a volatile memory inside a computer system that serves as a server or client in that case. Further, the program may be for realizing a part of the functions described above, or may be capable of realizing the functions described above in combination with a program already recorded in the computer system. It may be implemented using a programmable logic device such as an FPGA (Field Programmable Gate Array).

Although the embodiment of the present invention has been described in detail with reference to the drawings, the specific configuration is not limited to this embodiment, and design and the like are included within the scope of the gist of the present invention.

1 PON, 10 OLT, 20 ONU, 21 TRx, 22 MAC processing unit, 23 PHY, 24 external buffer, 30 Optical fiber 40 Optical splitter 220 Buffer setting unit 221 Built-in buffer

Claims (8)

an acquisition unit that acquires information indicating a request buffer amount for each of a plurality of queues;
converting the request buffer amount for each of the queues into a first minimum converted buffer amount based on the lowest possible data accommodation efficiency of the first storage unit, and calculating the lowest priority queue of the first storage unit; allocates a buffer amount calculated based on the first minimum equivalent buffer amount and the minimum required buffer amount per cycle of the dynamic bandwidth allocation function, and assigns the highest priority of the first storage unit to 1st buffer capacity, which is the buffer capacity obtained by subtracting the buffer capacity allocated to the queue with the lowest priority in the first storage section from the total capacity of the first storage section for queues other than the queue with the lowest priority A setting unit that allocates a buffer amount calculated based on a buffer amount and a second buffer amount that is the sum of a first minimum converted buffer amount of a queue other than the queue with the lowest priority in the first storage unit. and,
Buffer allocation device with When the first buffer amount is larger than the second buffer amount, the setting unit sets the first minimum converted buffer amount to each of the queues other than the queue with the lowest priority in the first storage unit. allocation, when the first buffer amount is less than or equal to the second buffer amount, the second buffer amount is distributed according to the ratio of the requested buffer amount of the queues other than the queue with the lowest priority in the first storage unit. 2. The buffer allocating apparatus of claim 1, each allocating a buffer amount. The setting unit compares the first minimum converted buffer amount with a required buffer amount indicating a minimum required buffer amount per cycle of the dynamic bandwidth allocation function, and determines the first minimum converted buffer amount as the required buffer amount. If it is larger than the buffer amount, the required buffer amount is allocated to the queue with the lowest priority in the first storage unit, and if the first minimum converted buffer amount is equal to or less than the required buffer amount, the 3. The buffer allocation device according to claim 1, wherein said first minimum converted buffer amount is allocated to said queue having the lowest priority in said first storage unit. The setting unit sets a buffer amount not set in the queue having the lowest priority in the first storage unit to a second minimum conversion buffer based on the lowest possible data accommodation efficiency in the second storage unit. 4. The buffer allocation device according to any one of claims 1 to 3, wherein the second minimum converted buffer amount is converted to an amount, and the second minimum converted buffer amount is allocated to the queue having the lowest priority in the second storage unit. The setting unit adjusts the amount of buffer not set in the queue other than the queue with the lowest priority in the first storage unit based on the lowest possible data accommodation efficiency in the second storage unit. 5. The buffer allocation device according to claim 4, wherein the second minimum converted buffer capacity is converted into a second minimum converted buffer capacity, and the second minimum converted buffer capacity is allocated to a queue other than the queue with the lowest priority in the second storage unit. an acquisition unit that acquires information indicating a request buffer size for each of a plurality of upstream transmission queues;
Converting the request buffer amount for each of the upstream transmission queues into a first minimum converted data length based on the lowest possible data accommodation efficiency of the built-in buffer, for the uplink transmission queue with the lowest priority of the built-in buffer allocate a buffer amount calculated based on the first minimum converted data length and the minimum required buffer amount per cycle of the dynamic bandwidth allocation function, and the upstream transmission with the lowest priority of the built-in buffer a first buffer capacity, which is a buffer capacity obtained by subtracting a buffer capacity allocated to the uplink transmission queue with the lowest priority of the built-in buffers from the total capacity of the built-in buffers for the uplink transmission queues other than the queue; a setting unit that allocates a buffer amount calculated based on a second buffer amount that is the sum of the first minimum equivalent buffer amounts of the uplink transmission queues other than the uplink transmission queue with the lowest priority of the built-in buffer;
subscriber line terminal equipment. an obtaining step of obtaining information indicating the amount of request buffers for each of the plurality of queues;
converting the request buffer amount for each of the queues into a first minimum converted buffer amount based on the lowest possible data accommodation efficiency of the first storage unit, and calculating the lowest priority queue of the first storage unit; allocates a buffer amount calculated based on the first minimum equivalent buffer amount and the minimum required buffer amount per cycle of the dynamic bandwidth allocation function, and assigns the highest priority of the first storage unit to 1st buffer capacity, which is the buffer capacity obtained by subtracting the buffer capacity allocated to the queue with the lowest priority in the first storage section from the total capacity of the first storage section for queues other than the queue with the lowest priority A setting step of allocating a buffer amount calculated based on a buffer amount and a second buffer amount that is the sum of a first minimum equivalent buffer amount of a queue other than the queue with the lowest priority in the first storage unit. and,
Buffer allocation method with A program for causing a computer to function as the buffer allocation device according to any one of claims 1 to 5.

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