KR20200046923A - Apparatus and method for measuring latency in passive optical network system - Google Patents

Abstract

Disclosed are a delay time measurement apparatus for a manual optical network system and a method thereof. The delay time measurement method performed by an optical line terminal (OLT) includes the following steps of: receiving a delay time measurement message about a class, assigned a service requiring a low delay, from a controller; storing a moment when a request message for bandwidth assignment is received from an optical network unit (ONU) as a first time in response to the received delay time measurement message; storing the bandwidth requested through the request message stored at the first time as a request value; storing the total of bandwidths, assigned when a grant message is generated for the bandwidth assignment of the ONU after the first time, as a grant value; determining whether the grant value is greater than or equal to the request value by comparing the request value to the grant value stored after the first time; storing a moment when the request message is received from the ONU after the determination of whether the grant value is greater than or equal to the request value as a second time; and delivering the stored first and second times to the controller. The controller can measure the longest delay time for a specific queue of the ONU based on the first and second times received from the OLT.

Description

Delay time measuring device and method in passive optical network system {APPARATUS AND METHOD FOR MEASURING LATENCY IN PASSIVE OPTICAL NETWORK SYSTEM}

The present invention relates to an apparatus and method for measuring a delay time in a passive optical network system (Passive Optical Network, PON), and more specifically, an optical line terminal (hereinafter referred to as OLT) and an optical network unit (Optical) in a PON system. It relates to an apparatus and method for managing the state of a time-sensitive service by measuring a delay time generated between Network Units (hereinafter referred to as ONUs) without separate measurement equipment.

An access network such as a PON or a mobile network includes multiple access nodes (e.g., PON ONU / eNB in a mobile network) and an access point (e.g., PON OLT / mobile network UE) and P2MP (Point-to Since the network is configured in the form of -multipoint), a method of sharing uplink resources for communication is used.

A method such as fixed bandwidth allocation (FBA) or dynamic bandwidth allocation (DBA) is used to allocate uplink resources shared by multiple access nodes without collision. The fixed bandwidth allocation method is a non-status reporting (Non-SR) method that allocates each access node to use a predetermined bandwidth at a predetermined time. While this fixed-band allocation method has no delay time variation, the uplink bandwidth is always allocated even when there is no data to be transmitted upward by the access node, and thus, the efficiency is deteriorated.

In order to supplement this, the dynamic band allocation method to which the SR (Status Report) method was applied was applied. In the dynamic band allocation method, the access nodes periodically transmit their buffer state to the access point at a predetermined time, or request uplink bandwidth from the access point when there is uplink traffic based on their buffer state, and allocate from the access point Uplink data can be transmitted as much as the received bandwidth. This dynamic bandwidth allocation method is excellent in efficiency, but delay variation for bandwidth request and bandwidth allocation is increased.

In the case of the existing PON, it provides a round trip time (RTT) measurement method to measure the delay deviation on the link. As an example, if the OLT uses the OAM (Operation Administration Maintenance) message to deliver the current time to the ONU, the ONU synchronizes its time with the OLT's current time and returns the OAM message to the OLT at the time requested by the OLT. can do. The OLT can calculate the round trip delay time deviation by comparing the time returned from the ONU with its own time.

However, such an RTT measurement method may have a problem in that it is impossible to measure a delay variation that varies depending on a network situation because a queuing delay time that causes a delay variation of actual uplink data transmission is not included.

The present invention provides an apparatus and method for managing a state of a time-sensitive service by measuring a delay time for an uplink of a PON system in real time without a separate OAM packet or equipment.

Delay time measurement method performed by an optical line terminal (OLT) according to an embodiment of the present invention includes receiving a delay time measurement message for a class to which a service requiring low latency is allocated from a controller; Storing, as a first time, a time point when a request message requesting bandwidth allocation is received from an optical network unit (ONU) in response to the received delay time measurement message; Storing a bandwidth requested through the request message stored in the first time as a request value; Storing a sum of allocated bandwidths as a grant value when generating a grant message for bandwidth allocation of the ONU after the first time; Determining whether the grant value is greater than or equal to the request value by comparing a request value and a grant value stored after the first time; Storing a second time when a request message is received from the ONU after determining that the grant value is greater than or equal to the request value; And passing the stored first time and second time to the controller, wherein the controller uses the first time and the second time received from the OLT to determine the maximum delay time for a specific queue of the ONU. Can be measured.

In the storing of the second time, the reception of the request message and the transmission of the grant message are defined as one cycle, and in response to the condition of whether the grant value is greater than or equal to the request value for each cycle. If the cycle has a periodic time, if the condition is satisfied, the second time is calculated and stored before receiving the request message of the next cycle. If the cycle does not have a periodic time, if the condition is satisfied The reception time of the request message of the next cycle may be stored as the second time.

The controller determines low-latency characteristics of a specific queue of the ONU based on the measured maximum delay time, and manages a state of a service that requires the low-delay based on the determination result. The OLT can be controlled to increase or decrease the allocable bandwidth.

According to an embodiment of the present invention In a passive optical network (PON) system, an optical line terminal (hereinafter referred to as OLT) for measuring delay time includes a processor, and the processor is configured for a class to which a service requiring low latency is allocated from a controller. A delay time measurement message is received, and in response to the received delay time measurement message, a time point at which a request message for requesting bandwidth allocation from an optical network unit (ONU) is received is stored as a first time. The bandwidth requested through the request message stored in 1 hour is stored as a request value, and when generating a grant message for allocating the ONU bandwidth after the first time, the sum of the allocated bandwidth is stored as a grant value. The grant value stored after the time is compared to the request value, and the grant value is the request. It is determined whether it is greater than or equal to a test value, and stores a time point when the request message is received from the ONU as a second time after the grant value is determined to be greater than or equal to the request value, and stores the stored first time and The second time is transmitted to the controller, and the controller can measure the maximum delay time for a specific queue of the ONU using the first time and the second time received from the OLT.

The processor defines the reception of the request message and the transmission of the grant message as one cycle, and the cycle is a periodic time corresponding to a condition that the grant value is greater than or equal to the request value for each cycle. If the condition is satisfied, the second time is calculated and stored before receiving the request message of the next cycle. If the cycle does not have a periodic time, the request message of the next cycle is received when the condition is satisfied. The time can be stored as a second time.

The controller determines low-latency characteristics of a specific queue of the ONU based on the measured maximum delay time, and manages a state of a service that requires the low-delay based on the determination result. The OLT can be controlled to increase or decrease the allocable bandwidth.

The controller may use the measured maximum delay time as a service state management factor to provide various services such as low-latency and low-power services according to various service requirements.

As an embodiment of the service status management of the controller, the delay status for each queue is determined by the ONU based on the measured maximum delay time, and the queue is not satisfied by comparing the delay requirement for each service requested by the ONU. To increase the available bandwidth temporarily, or add a wavelength to provide low-latency service.

On the contrary, if the delay requirement of the highest service in which the multi-queue or multi-wavelength delay sum used by the ONU satisfies is set, the services set in the multi-queue are integrated into a single queue or controlled to use a single wavelength to provide low-power services. You can.

According to an embodiment of the present invention, it is possible to manage a state of a time-sensitive service by measuring a delay time for an uplink of a PON system in real time without a separate OAM packet or equipment.

1 is a view showing the configuration of a delay time measurement system according to an embodiment of the present invention.
2 is a diagram showing a dynamic band allocation method according to an embodiment of the present invention.
3A and 3B are diagrams illustrating a method for measuring a maximum delay time according to an embodiment of the present invention.

Hereinafter, embodiments will be described in detail with reference to the accompanying drawings. However, various changes may be made to the embodiments, and the scope of the patent application right is not limited or limited by these embodiments. It should be understood that all modifications, equivalents, or substitutes for the embodiments are included in the scope of rights.

The terms used in the examples are for illustrative purposes only and should not be construed as limiting. Singular expressions include plural expressions unless the context clearly indicates otherwise. In this specification, the terms "include" or "have" are intended to indicate the presence of features, numbers, steps, actions, components, parts or combinations thereof described herein, one or more other features. It should be understood that the existence or addition possibilities of fields or numbers, steps, operations, components, parts or combinations thereof are not excluded in advance.

Unless defined otherwise, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by a person skilled in the art to which the embodiment belongs. Terms such as those defined in a commonly used dictionary should be interpreted as having meanings consistent with meanings in the context of related technologies, and should not be interpreted as ideal or excessively formal meanings unless explicitly defined in the present application. Does not.

In addition, in the description with reference to the accompanying drawings, the same reference numerals are assigned to the same components regardless of reference numerals, and redundant descriptions thereof will be omitted. In describing the embodiments, when it is determined that detailed descriptions of related known technologies may unnecessarily obscure the subject matter of the embodiments, detailed descriptions thereof will be omitted.

1 is a view showing the configuration of a delay time measurement system according to an embodiment of the present invention.

Time-sensitive services (hereinafter referred to as citizenship services) must satisfy the upward delay time from the access node to the access point. To this end, the present invention measures the uplink delay time of the queue corresponding to the class to which the citizenship service is assigned in real time through the dynamic band allocation method to which the SR method is applied, and the corresponding queue has low delay characteristics based on the measured uplink delay time. You can manage whether or not.

The dynamic band allocation method to which the SR method is applied is composed of a three-stage cyclic structure: 1) bandwidth request, 2) bandwidth allocation, and 3) uplink traffic delivery & bandwidth request. Since the uplink resource is shared in a circular structure, the access node must allocate sufficient bandwidth from the access point as much as the total amount of traffic stored in the buffer so that the uplink traffic can be delivered without buffer delay.

The present invention utilizes the delay generation characteristic of the dynamic band allocation method to which the SR method is applied, and compares the bandwidth requested by the access node with the bandwidth allocated by the access point, thereby increasing the upward delay time for a specific queue of ONU providing citizenship service Can be measured. And the present invention proposes a method of managing the state of the citizenship service by determining whether a specific queue of the ONU satisfies the low-latency characteristic based on the measured upward delay time.

Referring to FIG. 1, the delay time measurement system 100 may include a controller 110, an OLT 120, and an ONU 130. First, the controller 110 may designate a class to which the citizenship service is assigned and transmit a delay time measurement message to the access point, that is, the OLT 120.

The OLT 120 may receive an uplink bandwidth request message, that is, a request message, requesting bandwidth allocation for a specific queue corresponding to a class to which the citizenship service is allocated from the ONU 130 in response to the received delay time measurement message. have. In addition, the OLT 120 may store a time point at which the request message is received from the ONU 130 as the first time T1.

Thereafter, the OLT 120 may calculate the bandwidth allocable to the specific queue based on the service level agreement (SLA) of the ONU 130. Then, the OLT 120 may generate an uplink bandwidth allocation message, that is, a grant message, using the calculated allocable bandwidth, and transmit the generated grant message to the ONU 130.

The ONU 130 may transmit the traffic stored in a specific queue to the OLT 120 based on the bandwidth included in the received grant message.

Thereafter, the OLT 120 stores the point in time when all traffic stored in a specific queue of the ONU 130 is received as the second time T2, and controls the first time T1 and the second time T2 as the controller ( 110).

Then, the controller 110 may measure the maximum delay time for a specific queue of the ONU 130 using the first time T1 and the second time T2 received from the OLT 120. In addition, the controller 110 may determine whether the citizenship service corresponding to the specific queue of the ONU 130 satisfies the low-delay characteristic based on the measured maximum delay time. Thereafter, the controller 110 may manage the state of the citizenship service according to the determination result.

For example, when it is determined that the citizenship service corresponding to the specific queue of the ONU 130 does not satisfy the low-delay characteristic based on the measured maximum delay time, the controller 110 determines the corresponding ONU 130 The OLT 120 can be controlled to increase the allocable bandwidth for the queue.

On the contrary, when it is determined that the citizenship service corresponding to the specific queue of the ONU 130 satisfies a low-delay characteristic more than necessary based on the measured maximum delay time, the controller 110 determines the specific ONU 130 The OLT 120 may be controlled to allocate an allocable bandwidth for the queue to another queue.

2 is a diagram showing a dynamic band allocation method according to an embodiment of the present invention.

The dynamic band allocation method of the present invention may have a three-stage cyclic structure. Referring to FIG. 2, the access node, that is, the ONU 130 may transmit (step 1) the amount of traffic stored in its queue to the access point, that is, the OLT 120 using a request message.

Then, the OLT 120 calculates the allocable bandwidth in consideration of the bandwidth agreement and the available bandwidth with the ONU 130, and transmits a grant message including the calculated bandwidth information to the ONU 130 (step 2) can do.

Finally, the ONU 130 transmits the traffic stored in its queue to the OLT 120 as much as the bandwidth allocated through the grant message, and at the same time, uses the request message to determine the amount of traffic waiting to be transmitted to its queue using the request message. ) Can have a cyclic structure (3 steps).

In the case of the dynamic band allocation method to which the SR method is applied, since the upward data is transmitted through the three-step circular structure as described above, the ONU 130 cannot transmit the traffic stored in the queue until sufficient bandwidth is obtained from the OLT 120. do. Due to this, the ONU 130 increases the uplink delay time for the queue according to the network situation, and has a disadvantage in that it is impossible to accurately measure the uplink delay time without calculating the queuing delay.

The present invention provides a more accurate method for measuring the upward delay time by measuring such a queuing delay, and a more detailed method for measuring the upward delay time will be described with reference to FIG. 3 below.

3A and 3B are diagrams illustrating a method for measuring a maximum delay time according to an embodiment of the present invention.

The SR method provided in the present invention can be divided into two methods based on the periodicity of the request message. Specifically, there may be a scheme in which (1) a request message is exchanged based on a queue state rather than a specific period, or (2) exchanged based on a specific period.

(1) The method may transmit a message to report the required bandwidth to the ONU 130 when the OLT 120 can allocate bandwidth. Then, the ONU 130 requiring uplink bandwidth may be allocated a bandwidth from the OLT 120 by transmitting a request message based on the traffic stored in its queue. That is, in the method (1), since the request message is exchanged based on the queue state of the ONU 130, the time point at which the request message is transmitted from the ONU 130 to the OLT 120 may always be different.

(2) In the method, the OLT 120 and the ONU 130 may allocate bandwidth by exchanging grant messages and request messages according to a preset period. That is, in the method (2), since the request message is exchanged based on a preset period, that is, a specific period, the time at which the request message is transmitted from the ONU 130 to the OLT 120 may always be the same. Accordingly, in the method (2), a cycle time in which a pair of request messages and grant messages are transmitted and received can be fixed.

<First Example>

3A is a diagram illustrating a method for measuring a maximum delay time according to the method (1).

Referring to FIG. 3A, in step 302, the OLT 120 may receive a delay time measurement message for a class to which citizenship service is assigned from the controller 110.

Then, in step 304, the OLT 120 receives a request message, which is an uplink bandwidth request message for a specific queue corresponding to the class to which the citizen service is assigned, from the ONU 130 in response to the received delay time measurement message. Then, it is possible to identify the first time T1, which is the time when the request message is received.

In step 306, the OLT 120 may store the identified first time T1, and may store the requested bandwidth value through the request message as a request value.

In a subsequent step 308, the OLT 120 calculates the bandwidth allocable to the specific queue based on the service level agreement contracted with the ONU 130, and grants the uplink bandwidth allocation message using the calculated allocable bandwidth. You can generate a message. At this time, the OLT 120 may store the bandwidth value allocated to the ONU 130 through the grant message as a grant value.

In step 310, the OLT 120 may transmit the generated grant message to the ONU 130.

In step 312, the OLT 120 compares the request value stored in step 306 with the grant value stored in step 308 to determine whether the result of (grant value-request value) is greater than or equal to zero. can do. Specifically, the OLT 120 defines the reception of a pair of request messages and the transmission of a grant message as one cycle time, and a grant that previously stores the grant value allocated through the grant message every cycle time. Values can be summed. In addition, the OLT 120 may compare the accumulated grant value with the request value stored in the first time T1.

In step 314, the OLT 120 may determine a second time, which is a time point when all traffic stored in a specific queue of the ONU 130 is received, based on the periodicity of the cycle time. In the first scheme according to FIG. 3A, the request message is exchanged based on the queue state rather than a specific cycle, so the cycle time may not have a periodic time.

Accordingly, the OLT 120 continuously receives the request message and traffic data from the ONU 130 as in step 316, and the next cycle of the cycle time at which the result of (Grant value-Request value) is greater than or equal to 0. The reception time of the request message received at the time when the time starts may be determined as the second time T2.

In step 318, the OLT 120 may transmit information of the first time T1 and the second time T2 to the controller 110, and in step 320, the controller 110 may receive the received agent. The maximum delay time for a specific queue of the ONU 130 may be measured based on the information of the first time T1 and the second time T2.

At this time, the OLT 120 stores the reception time of the request message in units of each cycle time as T1-1 ,,, T1-n, and requests the bandwidth requested through the request message by request value-1, ,,, request value After storing as -n, the above process can be performed in the same way to calculate the average maximum delay time for a certain period of time.

Then, in step 322, the controller 110 may determine whether a specific queue of the ONU 130 satisfies the low-latency characteristic based on the measured maximum delay time.

Thereafter, in step 324, the controller 110 may manage the state of the citizenship service based on the determination result. In one example, when the controller 110 determines that the citizenship service corresponding to the specific queue of the ONU 130 does not satisfy the low-delay characteristic based on the measured maximum delay time, the controller 110 sends a delay timeout message to the operator. The OLT 120 may be controlled to notify or more actively increase the allocable bandwidth for the specific queue.

On the contrary, when it is determined that the citizen 110 service corresponding to a specific queue of the ONU 130 has a low-delay characteristic more than necessary based on the measured maximum delay time, the controller 110 integrates with services set in other queues. In order to manage or to control the wavelength or to control the OLT 120 to reduce the bandwidth allocable for the specific queue.

<Second Example>

3B is a diagram illustrating a method for measuring a maximum delay time according to the method (2).

Referring to FIG. 3A, in step 302, the OLT 120 may receive a delay time measurement message for a class to which citizenship service is assigned from the controller 110.

Then, in step 304, the OLT 120 receives a request message, which is an uplink bandwidth request message for a specific queue corresponding to the class to which the citizen service is assigned, from the ONU 130 in response to the received delay time measurement message. Then, it is possible to identify the first time T1, which is the time when the request message is received.

In step 306, the OLT 120 may store the identified first time T1, and may store the requested bandwidth value through the request message as a request value.

In a subsequent step 308, the OLT 120 calculates the bandwidth allocable to the specific queue based on the service level agreement contracted with the ONU 130, and grants the uplink bandwidth allocation message using the calculated allocable bandwidth. You can generate a message. At this time, the OLT 120 may store the bandwidth value allocated to the ONU 130 through the grant message as a grant value.

In step 310, the OLT 120 may transmit the generated grant message to the ONU 130.

In step 312, the OLT 120 compares the request value stored in step 306 with the grant value stored in step 308 to determine whether the result of (grant value-request value) is greater than or equal to zero. can do. Specifically, the OLT 120 defines the reception of a pair of request messages and the transmission of a grant message as one cycle time, and a grant that previously stores the grant value allocated through the grant message every cycle time. Values can be summed. In addition, the OLT 120 may compare the accumulated grant value with the request value stored in the first time T1.

In step 314, the OLT 120 may determine a second time, which is a time point when all traffic stored in a specific queue of the ONU 130 is received, based on the periodicity of the cycle time. In the second scheme according to FIG. 3B, the request message is exchanged based on a specific period, so that the cycle time can be fixed to a periodic time.

Therefore, the OLT 120 continuously receives the request message and the traffic data from the ONU 130 as in step 318, and it is possible to check the cycle time at which the result of (Grant value-Request value) is greater than or equal to 0. have.

At this time, since the request message is exchanged based on a specific cycle and the cycle time is fixed, the OLT 120 has a second time (T2) before the request message is received at the time the next cycle time starts, as in step 316. By calculating, information of the first time T1 and the second time T2 may be transmitted to the controller 110. In this case, since the second time T2 can be calculated before the reception of the next request message, there is an advantage that the uplink delay time can be calculated more quickly.

In step 320, the controller 110 may measure a maximum delay time for a specific queue of the ONU 130 based on the received first time T1 and second time T2 information.

At this time, the OLT 120 stores the reception time of the request message in units of each cycle time as T1-1 ,,, T1-n, and requests the bandwidth requested through the request message by request value-1, ,,, request value After storing as -n, the above process can be performed in the same way to calculate the average maximum delay time for a certain period of time.

Then, in step 322, the controller 110 may determine whether a specific queue of the ONU 130 satisfies the low-latency characteristic based on the measured maximum delay time, and in step 324, the controller The 110 may manage the state of the citizenship service based on the determination result.

The method according to the embodiment may be implemented in the form of program instructions that can be executed through various computer means and recorded on a computer readable medium. The computer-readable medium may include program instructions, data files, data structures, or the like alone or in combination. The program instructions recorded on the medium may be specially designed and configured for the embodiments or may be known and usable by those skilled in computer software. Examples of computer-readable recording media include magnetic media such as hard disks, floppy disks, and magnetic tapes, optical media such as CD-ROMs, DVDs, and magnetic media such as floptical disks. -Hardware devices specially configured to store and execute program instructions such as magneto-optical media, and ROM, RAM, flash memory, and the like. Examples of program instructions include high-level language code that can be executed by a computer using an interpreter, etc., as well as machine language codes produced by a compiler. The hardware device described above may be configured to operate as one or more software modules to perform the operations of the embodiments, and vice versa.

The software may include a computer program, code, instruction, or a combination of one or more of these, and configure the processing device to operate as desired, or process independently or collectively You can command the device. Software and / or data may be interpreted by a processing device, or to provide instructions or data to a processing device, of any type of machine, component, physical device, virtual equipment, computer storage medium or device. , Or may be permanently or temporarily embodied in the transmitted signal wave. The software may be distributed on networked computer systems, and stored or executed in a distributed manner. Software and data may be stored in one or more computer-readable recording media.

As described above, although the embodiments have been described with limited drawings, those skilled in the art can apply various technical modifications and variations based on the above. For example, the described techniques are performed in a different order than the described method, and / or the components of the described system, structure, device, circuit, etc. are combined or combined in a different form from the described method, or other components Alternatively, even if replaced or substituted by equivalents, appropriate results can be achieved.

Therefore, other implementations, other embodiments, and equivalents to the claims are also within the scope of the following claims.

100: delay time measurement system
110: controller
120: OLT
130: ONU

Claims (6)

In the method for measuring the delay time performed by an optical line terminal (OLT),
Receiving a delay time measurement message for a class to which a service requiring low latency is allocated from a controller;
Storing, as a first time, a time point when a request message requesting bandwidth allocation is received from an optical network unit (ONU) in response to the received delay time measurement message;
Storing a bandwidth requested through the request message stored in the first time as a request value;
Storing a sum of allocated bandwidths as a grant value when generating a grant message for bandwidth allocation of the ONU after the first time;
Determining whether the grant value is greater than or equal to the request value by comparing a request value and a grant value stored after the first time;
Storing a second time when a request message is received from the ONU after determining that the grant value is greater than or equal to the request value; And
Passing the stored first time and second time to the controller
Including,
The controller,
Delay time measurement method for measuring the maximum delay time for a specific queue of the ONU using the first time and the second time received from the OLT. According to claim 1,
The step of storing the second time,
The reception of the request message and the transmission of the grant message are defined as one cycle, and in response to the condition that the grant value is greater than or equal to the request value for each cycle.
When the cycle has a periodic time, if the condition is satisfied, the second time is calculated and stored before receiving the request message of the next cycle,
When the cycle does not have a periodic time, when the condition is satisfied, a method for measuring a delay time of storing the request message reception time of the next cycle as the second time. According to claim 1,
The controller,
Allocable bandwidth for a specific queue of the ONU to determine low-latency characteristics of the specific queue of the ONU based on the measured maximum delay time, and to manage a state of a service that requires the low delay based on the determination result Delay time measurement method to control the OLT to increase or decrease. In an optical line terminal (hereinafter referred to as OLT) for measuring a delay time in a passive optical network (PON) system,
Processor
Including,
The processor,
Receiving a delay measurement message for a class to which a service requiring low latency is allocated from the controller,
In response to the received delay time measurement message, the first time stores a time point when a request message requesting bandwidth allocation is received from an optical network unit (ONU),
The bandwidth requested through the request message stored in the first time is stored as a request value,
When the grant message is generated for the ONU bandwidth allocation after the first time, the sum of the allocated bandwidth is stored as a grant value,
Compare the grant value and the request value stored after the first time to determine whether the grant value is greater than or equal to the request value,
When the grant value is determined to be greater than or equal to the request value, a time point at which the request message is received from the ONU is stored as a second time,
The stored first time and second time are transmitted to the controller,
The controller,
An optical line terminal measuring a maximum delay time for a specific queue of the ONU using the first time and the second time received from the OLT. According to claim 4,
The processor,
The reception of the request message and the transmission of the grant message are defined as one cycle, and in response to the condition that the grant value is greater than or equal to the request value for each cycle.
When the cycle has a periodic time, if the condition is satisfied, the second time is calculated and stored before receiving the request message of the next cycle,
When the cycle does not have a periodic time, when the condition is satisfied, the optical line terminal stores the request message reception time of the next cycle as the second time. According to claim 4,
The controller,
Allocable bandwidth for a specific queue of the ONU to determine low-latency characteristics of the specific queue of the ONU based on the measured maximum delay time, and to manage a state of a service that requires the low delay based on the determination result Optical line terminal to control the OLT to increase or decrease.

Images