JP5804566B2 - Sleep control method, optical communication system, and optical network termination device - Google Patents

Description

  The present invention relates to an optical communication system in which an optical subscriber line terminator (OLT) and an optical network terminator (ONU) are connected via an optical fiber transmission line and transmitted / received by an optical signal. It relates to low power consumption technology.

  An optical network is a network in which one OLT performs point-to-point or point-to-multipoint communication with one or a plurality of ONUs via an optical fiber transmission line.

  In order to reduce the power consumption of the optical network, an ONU sleep function that stops the main function of the ONU when there is no data traffic has been discussed. Among them, a method called Doze or Cyclic sleep is G.I. Standardization is underway by 987.3, IEEE1904.1, etc., and is expected as an effective technique for reducing the power consumption of ONUs.

  A configuration of an optical communication system related to this specification is shown in FIG. The optical communication system includes an OLT 1, an ONU 2, an optical fiber transmission line 8 and an optical splitter 9. The OLT 1 includes a logic unit 41, a transmission / reception unit 42, and an SNI (Service Node Interface) physical layer unit 43. The ONU 2 includes a logic unit 11, a transmission / reception unit 12, and a UNI (User Network Interface) physical layer unit 13.

  In Doze, it is confirmed by UNI monitoring of the logic unit 11 that there is no upstream data traffic, sleep control is performed by the logic unit 41, state switching is performed by the logic unit 11, and the ONU 2 shifts from the wake-up state to the Doze state. In the Doze state, the ONU 2 reduces the power consumption by stopping part or all of the transmission function of the upstream traffic while maintaining the function related to the reception of the downlink traffic.

  In cyclic sleep, it is confirmed by UNI monitoring of the logic unit 11 that there is no upstream data traffic, and it is confirmed by SNI monitoring of the logic unit 41 that there is no downstream data traffic, and the logic unit 11 and the logic unit 41 indicate that. Exchange messages. The sleep control is performed by the logic unit 41, the state is switched by the logic unit 11, and the ONU 2 shifts from the wake-up state to the cyclic sleep state.

  If upstream traffic is input to ONU 2 when ONU 2 is in the Doze state or Cyclic sleep state, ONU 2 cancels the Doze state or Cyclic sleep state and starts data communication.

  Even when there is no upstream traffic input in the cyclic sleep state, the ONU 2 is activated to confirm sleep continuation after a predetermined sleep continuation time. If downstream traffic addressed to ONU2 is input to OLT1 during the cyclic sleep state, OLT1 transmits a message with downstream traffic to ONU2 at the confirmation of sleep continuation, and ONU2 determines that sleep is suspended and receives downstream data. Start. If the downstream traffic destined for ONU2 is not input to OLT1 during the cyclic sleep, ONU2 transitions again to the cyclic sleep state.

  As described above, when there is no downlink traffic, the transition to the cyclic sleep state and the activation of the traffic confirmation are repeated periodically, and this sleep method is called cyclic sleep. In the following description, when Doze and Cyclic sleep are not distinguished, they are simply described as sleep.

  Depending on which part of the ONU 2 is stopped during the sleep, the power consumption, the time taken to shift to the sleep state, and the time to shift from the sleep state to the wake-up state vary. G. In 987.3, Doze that does not stop the portion related to the reception function of the downlink traffic and Cyclic sleep that may stop the portion related to the reception function of the downlink traffic in the sleep state are separately described. IEEE1904.1 describes the former as Tx sleep and the latter as TRx sleep.

  As a condition to enter sleep, a method that triggers that traffic does not arrive for a certain period of time to reduce delay, or that the amount of frames accumulated in the queue becomes smaller than the threshold to increase the power saving effect Has been proposed (see, for example, Non-Patent Document 1).

Ryosuke Kubo, Junichi Kani, Yukihiro Fujimoto, Naoto Yoshimoto, Kiyomi Kumozaki, Performance Analysis of 10 Giga-Class PON System with Power Saving Function, IEICE Technical Report, CS2009-2, pp. 7-12

  In the data transmission method using TCP, an ACK frame is returned to the transmission side when data is received on the reception side (section (a) in FIG. 4). If the transmission side cannot receive the ACK frame, the data reachability can be ensured by retransmitting the data to the reception side.

  If the next frame cannot be sent before receiving the ACK frame, the amount of data that can be transmitted per unit time is significantly limited if the round trip delay time is large. Window control that may be transmitted is performed (section (b) in FIG. 4). In window control, the amount of data that can be transmitted before receiving an ACK frame is limited by the window size. When transmission data is lost, it is determined that congestion has occurred, and the window size is reduced. As a result, it is possible to prevent the amount of data that can be transmitted over the communication path from being transmitted and avoid congestion.

  When a terminal under the control of ONU 2 downloads a file or the like using TCP, downlink data is continuously transmitted by TCP, and downlink traffic arrives at ONU 2. In addition, ACK frames sent from the terminals under the ONU 2 arrive at the ONU 2 intermittently at short intervals (section (c) in FIG. 4).

  In the sleep method triggered by the fact that the traffic does not arrive for a certain period of time as described above, when the arrival of the ACK frame is shorter than the threshold, the sleep mode cannot be entered at all, and there is a problem that it is difficult to obtain a power saving effect.

  Also in the sleep method using the amount of frames accumulated in the queue as a threshold, it is necessary to wake up every time an ACK frame that has arrived exceeds the threshold. During frequent wake-ups, it takes time to stop some functions of the ONU 2 and time to start the corresponding functions, so there is a problem that the power saving effect is reduced by intermittent arrival of ACK frames. It was.

  Accordingly, in order to solve the above-described problems, the present invention provides a sleep control method, an optical communication system, and an optical network termination device that can obtain a power saving effect by sleep even while TCP traffic is flowing. For the purpose.

  In order to achieve the above object, the present invention thins out an ACK frame for a data frame in order to make it easy to go into sleep, and suppresses the TCP transmission rate reduction at least once before using up the congestion window. Send a frame. FIG. 5 is a diagram for explaining the operation of the frame in the present invention. In the present invention, the ACK frame is not returned every time for the data frame from the transmission side, but the ACK frame is returned about once every plural times. By doing in this way, the opportunity to sleep the block which transmits an ACK frame increases.

  Specifically, in the sleep control method according to the present invention, an optical subscriber line termination device (OLT: Optical Line Terminal) and an optical network termination device (ONU: Optical Network Unit) perform optical communication via an optical fiber transmission line. In the optical communication system to be performed, a sleep control method for setting the ONU to a sleep state or a wake-up state based on an amount of traffic passing through the ONU per unit time, the reception confirmation frame and other frames included in the traffic And performing a thinning-out operation for thinning out the reception confirmation frame based on a predetermined rule.

  The present invention controls the ACK frame (acknowledgment confirmation frame) of TCP traffic to be thinned out, thereby increasing the opportunity for the ONU to go to sleep and realizing efficient low power consumption. Therefore, the present invention can provide a sleep control method that can obtain a power saving effect due to sleep even while TCP traffic is flowing.

  In the sleep control method according to the present invention, for the predetermined rule, the number from the count start of the reception confirmation frame or the elapsed time from the count start time of the reception confirmation frame is constant until a predetermined threshold is reached. A plurality of the reception confirmation frames that meet the requirements may be grouped, and at least only the latest reception confirmation frame may be used.

  The ACK frame can be transmitted only once or a plurality of times from the start of counting the ACK frame until the predetermined number is reached, or from the start of counting the ACK frame until the predetermined time liquefies. Thus, by thinning out the ACK frame, the ONU sleep opportunities can be increased.

  In the sleep method using the amount of frames accumulated in the queue as a threshold, if the threshold is made very large without considering communication quality, the power saving effect by sleep can be obtained, but the ACK frame does not return. There is a risk that the TCP session may be disconnected due to a decrease in the TCP transmission rate or a timeout. The decrease in transmission rate and timeout not only affect the communication quality, but also increase the communication time and result in lost opportunity for sleep.

  Therefore, in the sleep control method according to the present invention, it is preferable to set the separately defined threshold based on a congestion window, an advertisement window, or a round trip delay time. A sleep control method, an optical communication system, and an optical network terminator capable of obtaining a power saving effect due to sleep even while TCP traffic is flowing, and capable of both reducing TCP transmission rate and suppressing session disconnection It is possible to provide.

  Therefore, in the sleep control method according to the present invention, the separately determined threshold value may be increased from an initial value to such an extent that the number of the reception confirmation frames per unit time can be maintained. Even when the appropriate threshold value is unknown, it is possible to set the appropriate threshold value without lowering the transmission rate by adaptively changing the threshold value.

  Therefore, the sleep control method according to the present invention may change the ONU from the sleep state to the wake-up state when the number of reception confirmation frames having the same reception confirmation number exceeds a certain number. The duplicate confirmation number is evidence that the data frame has not been transmitted to the receiving side. Therefore, when there is an ACK frame with the same reception confirmation number, the ONU is woken up to promptly retransmit the missing data frame to the transmission side.

  Therefore, the sleep control method according to the present invention starts the thinning-out operation when the amount of the reception confirmation frame per unit time exceeds a predetermined value, and the amount of the reception confirmation frame per unit time is the predetermined value. If it becomes less, the thinning operation may be stopped. Even for an application that requires high-speed response, the reception confirmation frame is immediately transmitted, so that control without impairing the high-speed response is possible.

  The sleep control method is executed by any one of the OLT, ONU, and home gate device (HGW) in the optical communication system having a function of thinning-out reception confirmation frames.

  The present invention can provide a sleep control method, an optical communication system, and an optical network termination device that can obtain a power saving effect due to sleep even while TCP traffic is flowing.

It is a figure explaining the structure of the optical communication system relevant to this invention. It is a figure explaining the structure of the optical communication system which concerns on this invention. It is a figure explaining the structure of the optical communication system which concerns on this invention. It is a figure explaining the window control relevant to this invention. It is a figure explaining the effect of the sleep control method concerning the present invention. An ACK frame is returned about once every RTT.

  Embodiments of the present invention will be described with reference to the accompanying drawings. The embodiments described below are examples of the present invention, and the present invention is not limited to the following embodiments.

(Embodiment 1)
In the optical communication system of this embodiment, the ONU thins out the ACK frame. Specifically, the ONU puts the transmission function block in a sleep state and wakes up only at a predetermined time. As the ONU operates in this manner, the chance of sleep increases. The ACK frame is transferred only when the ONU wakes up, and the ACK frame is thinned out. Also, since the ACK frame arrival interval becomes longer in the device to which the ACK frame is transferred, the sleep chance of the reception block increases.

[Configuration of optical communication system]
The configuration of the optical communication system of this embodiment is shown in FIG. The optical communication system includes an OLT 1, an ONU 2, and an optical fiber transmission line 3. In FIG. 2, one OLT 1 and one ONU 2 are connected in a point-to-point manner via an optical fiber transmission line 3, but as shown in FIG. 1, one OLT 1 and a plurality of ONUs 2 are optical fiber transmissions. A point-to-multipoint connection may be established via the path 3 and the optical splitter 9.

[Configuration of ONU]
The ONU 2 includes a traffic monitoring unit 21, a buffer 22, a transmission / reception unit 23, a transmission unit 24, a reception unit 25, a sleep determination / instruction unit 26, and a reception confirmation frame monitoring unit 28.

[Description of each part through which traffic passes]
Downstream traffic is transmitted from the OLT 1 to the downstream side via the transmission / reception unit 23 and the reception unit 25. Upstream traffic is transmitted from the downstream side to the OLT 1 via the traffic monitoring unit 21, the buffer 22, the transmission unit 24, and the transmission / reception unit 23.

[Description of traffic monitoring unit]
The traffic monitoring unit 21 monitors whether there is upstream traffic. Then, the sleep determination / instruction unit 26 is notified that there is upstream traffic. Each block capable of sleeping in the ONU 2 receives a sleep start command (to be described later) from the sleep determination / instruction unit 26 and shifts to a sleep state. Then, in response to a sleep release command (to be described later) from the sleep determination / instruction unit 26, the state shifts to the wake-up state.

[Explanation of how to identify the reception confirmation frame]
The traffic monitoring unit 21 detects the arrival of a frame corresponding to the reception confirmation frame, and if it is a reception confirmation frame, notifies the reception confirmation frame monitoring unit 28 without notifying the sleep determination / instruction unit 26 directly. In order to determine whether the frame corresponds to the reception confirmation frame, for example, it is used that the frame size is equal to a specified value or that a specific bit is equal to a specified value. In the case of a TCP ACK frame, the protocol number of the IP header is TCP, the A flag of the TCP header is set, the payload length is 0, that is, the Ethernet (registered trademark) frame length is the preamble and the interface. An example is to confirm that it is 64 bytes excluding the frame gap.

[Description of sleep cancel command by sleep determination / instruction unit]
The sleep determination / instruction unit 26 is notified from the traffic monitoring unit 21 that there is upstream traffic. When the flow rate per unit time exceeds a separately defined threshold, a sleep release command is output to each block capable of sleeping.

[Description of Sleep Start Command by Sleep Judgment / Instruction Unit 26]
When determining that there is no upstream traffic, the sleep determination / instruction unit 26 outputs a sleep start command to each block capable of sleeping. The determination that there is no upstream traffic is, for example, triggered by the passage of a certain time after notification from the traffic monitoring unit 21 that there is upstream traffic, or by monitoring the buffer 22 and the specific queue is empty. To do.

[Description of reception confirmation frame monitoring unit]
The reception confirmation frame monitoring unit 28 is notified of information related to the reception confirmation frame from the traffic monitoring unit 21. The reception confirmation frame monitoring unit 28 notifies the sleep determination / instruction unit 26 of the presence / absence of upstream traffic based on the notified information.

[Grouping of reception confirmation frames ((5) (8) described later)]
For example, the reception confirmation frame monitoring unit 28 regards a reception confirmation frame having the same combination of the transmission source IP address and the transmission destination IP address as a reception confirmation frame group in one connection, and the reception confirmation frame in the same connection is received as described later. The sleep determination / instruction unit 26 is not notified until the confirmation frame number threshold is exceeded, and the sleep determination / instruction unit 26 is notified when the reception confirmation frame number threshold is exceeded. Reduce.

[Grouping of reception confirmation frames ((6) (7) described later)]
As a criterion for judging multiple reception confirmation frames as the same connection, the same sequence number may be considered as the same connection instead of the combination of the source address and the destination address, and the increase in the reception confirmation number is within a certain range. May be regarded as the same connection, or may be determined as the same connection by combining them.
If it is ACK in TCP, the sequence number of the acknowledgment packet in the same connection is the same.
For example, when the segment size is set to 1460 bytes and the delayed ACK that returns one ACK is enabled for two data segments, the reception confirmation number is increased. An example in which the same connection is considered when the number increment is 2920 or less is given.

[Control of transmission timing of reception confirmation frame by time threshold (described later (9))]
In addition, the reception confirmation frame monitoring unit 28 provides a reception confirmation frame time threshold instead of the reception confirmation frame count threshold, and sleeps until the reception confirmation frame time threshold is exceeded after the last reception confirmation frame in the same connection is transmitted. By notifying the judgment / instruction unit 26 but notifying the sleep judgment / instruction unit 26 when the reception confirmation frame time threshold is exceeded, the number of times of outputting the sleep release command by the reception confirmation frame may be reduced.

[Set threshold of number from advertisement window size ((10) (13) described later)]
The reception confirmation frame number threshold setting in the reception confirmation frame monitoring unit 28 is, for example, a setting based on the window size described in the reception confirmation frame in the case of ACK in TCP. Specifically, when the window size described in the reception confirmation frame is 65535 bytes and the reception confirmation number increment of the reception confirmation frame is 2720, the time since the transmission of the reception confirmation frame in the same connection last time When the increment of the reception confirmation number exceeds 62815 obtained by subtracting 2720 from 65535, the sleep determination / instruction unit 26 may be notified, or the number of reception confirmation frames 23 obtained by dividing 62815 by 2720 has been exceeded. The sleep determination / instruction unit 26 may be notified at the time, or a value obtained by multiplying these values by a coefficient of 0 or more and 1 or less may be set as a threshold value from the side on the safe side.

[Set a threshold value from the time stamp value (described later (11) (13))]
The reception confirmation frame monitoring unit 28 sets the reception confirmation frame time threshold value based on the time stamp value described in the reception confirmation frame, for example, in the case of ACK in TCP.

[Set time threshold from advertisement window size ((10) (13) described later)]
The reception confirmation frame time threshold in the reception confirmation frame monitoring unit 28 may be set based on the window size described in the reception confirmation frame. Specifically, when the window size described in the reception confirmation frame is 65535 bytes, the increment of the reception confirmation number after the transmission of the reception confirmation frame in the same connection last time exceeds 65535. However, a value obtained by multiplying this value by a coefficient of 0 or more and 1 or less may be set as the threshold value from the side on the safe side.

[Obtain a threshold value base value from another device (described later (17))]
In addition, the reception confirmation frame number threshold and the reception confirmation frame time threshold in the reception confirmation frame monitoring unit 28 are set from a device connected under the ONU 2 and more accurately grasping the congestion window size and the round trip delay time. You may set based on the value notified.

[Set based on the arrival interval of the reception confirmation frame (described later (18))]
The reception confirmation frame time threshold in the reception confirmation frame monitoring unit 28 may be set based on the arrival interval of reception confirmation frames in the same connection. Specifically, in the case of an ACK in TCP, the arrival interval of the reception confirmation frame is determined using the fact that the window size is smaller than the bandwidth delay product immediately after the start of the connection and the arrival interval of the ACK group is substantially equal to the round trip delay time. It may be counted and set as a reception confirmation frame time threshold, or a value obtained by multiplying this value by a coefficient of 0 or more and 1 or less may be set as a threshold from the side on the safe side.

[Effect of this optical communication system]
Even when a large number of reception confirmation frames arrive in the same connection, the sleep determination / instruction unit 26 issues a sleep release command to each sleepable block until receiving a notification from the reception confirmation frame monitoring unit 28. Since transmission is not performed, each sleepable block can stay in the sleep state for a long time, and the number of transitions between the activated state and the sleep state can be reduced.

  In addition, the reception confirmation frame monitoring unit 28 makes a sleep determination at a cycle shorter than the interval at which the TCP transmission terminal uses up the window size by setting the reception confirmation frame time threshold or the reception confirmation frame number threshold in the reception confirmation frame monitoring unit 28. / Since the notification is sent to the instruction unit 26, the ONU 2 transits to the activated state, the reception confirmation frame is transmitted, and the reception confirmation frame can be received before the TCP transmission terminal uses up the window size. As a result, it is possible to suppress a decrease in the transmission rate of the TCP transmission terminal and session disconnection.

[Variable threshold ((12) described later)]
The reception confirmation frame monitoring unit 28 sets the reception confirmation frame time threshold or the reception confirmation frame number threshold so that the number of reception confirmation frames received in the same connection per unit time is monitored and the transmission rate does not decrease. The reception confirmation frame time threshold or the reception confirmation frame number threshold may be increased from a small initial value while confirming the above.

  Specifically, for example, the initial value of the reception confirmation frame count threshold is set to 1, and the reception confirmation frame monitoring unit 28 starts to send a notification to the sleep determination / instruction unit 26 every time a reception confirmation frame is received. A value obtained by multiplying the number of reception confirmation frames received per unit time by the reception confirmation frame number threshold by a coefficient of 0 or more and 1 or less is held as a transmission rate decrease determination threshold. The reception confirmation frame number threshold is increased exponentially, and when the number of reception confirmation frames received per unit time falls below the transmission rate reduction judgment threshold, the reception confirmation frame number threshold is returned to one step lower. Is given as an example. The increasing method may be increased proportionally instead of exponentially increasing. The threshold value to be changed may be a reception confirmation frame time threshold value instead of the reception confirmation frame number threshold value.

  Specifically, for example, in the case of TCP ACK, the ONU 2 may not be able to acquire all the contents of the IP header and TCP header. For example, the time stamp that is treated as an option is valid at both the transmitting terminal and the receiving terminal. If not, you cannot get it. Thus, even when the appropriate threshold is unknown, it is possible to set an appropriate threshold that does not decrease the transmission rate by adaptively changing the threshold.

The optical communication system of the present embodiment may have the functions described below.
[Decimation of reception confirmation frame ((14) described later)]
The reception confirmation frame monitoring unit 28 may leave only the latest reception confirmation number among the reception confirmation frames of the same connection, and discard the reception confirmation frame with the old reception confirmation number. By discarding the old reception confirmation frame, the possibility of transmitting all the reception confirmation frames stored in the buffer in one given transmission permission is increased, and a transition to the sleep state is made without waiting for the next transmission permission. It becomes possible.

[Reminder immediately after loss detection (described later (15))]
Also, the reception confirmation frame monitoring unit 28 includes the reception confirmation frames of the same connection.
When a certain number of reception confirmation frames with overlapping reception confirmation numbers are continuously received, a notification may be sent immediately to the sleep determination / instruction unit 26. Specifically, for example, in the case of TCP ACK, when three or more reception confirmation frames with overlapping reception confirmation numbers are received, a notification of the missing segment is immediately sent to the sleep determination / instruction unit 26. Resending can be promptly prompted.

  In TCP communication, a TCP receiver writes a reception confirmation frame with a reception confirmation number written up to a segment that can be received. For this reason, when there is a segment that could not be received, a reception confirmation frame with a duplicated reception confirmation number is transmitted each time a segment connected to that segment is received. When the TCP sender receives a reception confirmation frame in which three or more reception confirmation numbers are duplicated, it retransmits the missing segment.

[Reduction of rate increase delay (described later (16))]
In addition, the reception confirmation frame monitoring unit 28 sends a notification to the sleep determination / instruction unit 26 every time a reception confirmation frame is received until the number of reception confirmation frames received in the same connection per unit time exceeds a separately determined threshold. The notification to the sleep determination / instruction unit 26 may be suppressed until the number of reception confirmation frames received in the same connection per unit time falls below a separately defined threshold.

  Specifically, for example, in the case of ACK in TCP, if the reception confirmation frame is thinned out immediately after the start of communication and the window size of the TCP transmitting terminal is small and has not reached the bandwidth delay product, the increase in the window size is delayed. There are concerns.

  In TCP communication, there is a mechanism in which the TCP transmission terminal increases the window size exponentially, triggered by the reception of ACK, particularly slow start immediately after the start of communication, and if the transmission timing of ACK is delayed during this period, the window size The increase can be delayed.

  For example, the threshold value may be mechanically determined to be 1000 frames in 1 s. In this example, when the frame size is 1250 bytes, the connection is performed at a speed of 10 Mbps or more. Thus, the notification to the sleep determination / instruction unit 26 is suppressed.

  By introducing control switching based on this threshold, a reception confirmation frame is immediately transmitted even for applications that require a small number of receptions per unit time and high-speed response. Control without impairing the performance becomes possible.

(Embodiment 2)
In the optical communication system of the present embodiment, the home gateway device (HGW) detects the ACK frame and instructs the ONU to thin out the ACK frame. Specifically, the HGW places the transmission function block in the sleep state with respect to the ONU and wakes up only at a predetermined time. As the HGW operates in this manner, the opportunity for ONU sloop increases. The ACK frame is transferred only when the ONU wakes up, and the ACK frame is thinned out. Also, since the ACK frame arrival interval becomes longer in the device to which the ACK frame is transferred, the sleep chance of the reception block increases.

[Configuration of optical communication system]
The configuration of the optical communication system of this embodiment is shown in FIG. The optical communication system includes an OLT 1, an ONU 6, an optical fiber transmission line 3, and an HGW 5. The difference from the configuration of the first embodiment shown in FIG. 2 is that the HGW 5 is connected under the ONU 6.

[Configuration of ONU]
The ONU 6 includes a buffer 62, a transmission / reception unit 63, a transmission unit 64, a reception unit 65, and a sleep determination switch unit 67.

[Configuration of HGW]
The HGW 5 includes a traffic monitoring unit 51, a buffer 52, a transmission / reception unit 53, a sleep determination unit 56, and a reception confirmation frame monitoring unit 58.

[Description of each part through which traffic passes]
Downstream traffic is transmitted downstream from the OLT 1 via the transmission / reception unit 63, the reception unit 65, and the transmission / reception unit 53. The upstream traffic is transmitted from the downstream side to the OLT 1 via the traffic monitoring unit 51, the buffer 52, the transmission / reception unit 53, the sleep determination switch unit 67, the buffer 62, the transmission unit 64 and the transmission / reception unit 63.

[Description of traffic monitoring unit, sleep determination unit, sleep instruction unit]
The traffic monitoring unit 51 monitors whether there is upstream traffic. Then, the sleep determination unit 56 is notified that there is upstream traffic. The sleep determination unit 56 transmits a sleep start command to the ONU 6 when it is determined that the amount of traffic to wake up per unit time has not arrived according to a separately provided sleep threshold. The sleep determination unit 56 transmits a sleep cancel command to the ONU 6 when it is determined that the traffic amount to be woken up per unit time has arrived according to a separately provided sleep threshold.

  When the sleep determination switch unit 67 receives the sleep start instruction or the sleep release instruction transmitted from the HGW 5, the sleep determination switch unit 67 notifies the sleep instruction to each sleepable block of the ONU 6, and other frames to the buffer 62. Forward. Each block in the ONU 6 capable of sleeping receives a sleep start command from the sleep determination switch unit 67 and shifts to a sleep state. Then, in response to a sleep release command from the sleep determination switch unit 67, the state shifts to a wake-up state.

  The difference from the first embodiment is that the configuration of the ONU 6 is further simplified by making the sleep determination not by the ONU 6 but by the HGW 5. In general, compared to the ONU, the HGW is often accompanied by a higher layer control function, so that the reception confirmation frame monitoring unit 58 is relatively easy to implement.

  The traffic monitoring unit 51 detects the arrival of a frame corresponding to the reception confirmation frame, and notifies the reception confirmation frame monitoring unit 58 of the arrival confirmation frame without notifying the sleep determination unit 56 directly. The operation of the reception confirmation frame monitoring unit 58 is the same as the operation of the reception confirmation frame monitoring unit 28 described in the first embodiment.

The following is a summary of the optical communication systems of the first and second embodiments.
[Task]
When the sleep method is adopted as the PON method, there is a problem that when TCP traffic is flowing, the ACK frame may cause the device not to go into sleep at all and the low consumption efficiency is lowered. Therefore, this optical communication system controls the number of transmissions of ACK frames of TCP traffic, thereby increasing the number of opportunities for the ONU to go to sleep and realizing efficient low power consumption.

(1) [ONU treats ACK specially]
An optical communication system comprising an ONU, wherein the ONU shifts from a wake-up state to a sleep state when determining that the amount of traffic to be observed per unit time is below a certain amount,
When the ONU determines that the received traffic includes a reception confirmation frame, the ONU uses a calculation method different from that for other frames as the amount of traffic to be observed for the reception confirmation frame per unit time. Optical communication system.

(2) [HGW thins out ACK]
An optical communication system comprising an ONU and an HGW, wherein the ONU shifts from a wake-up state to a sleep state when determining that the amount of traffic to be observed per unit time is below a certain amount,
The optical communication system, wherein the HGW reduces the number of transmissions of the reception confirmation frame when determining that the observed traffic includes the reception confirmation frame.

(3) [OLT thins out ACK (down)]
An optical communication system including an OLT and an ONU, wherein the ONU shifts from a wake-up state to a sleep state when it determines that the amount of traffic to be observed per unit time is below a certain amount,
The optical communication system, wherein the OLT reduces the number of times of transmission of a reception confirmation frame when determining that the observed traffic includes a reception confirmation frame.

(4) [The end on the ACK transmission side reduces the number of ACK transmissions]
A communication terminal that performs communication via an optical communication system including an ONU, wherein the ONU shifts from a wake-up state to a sleep state when determining that the amount of traffic to be observed per unit time is below a certain amount,
The communication terminal reduces the number of transmissions of a reception confirmation frame for a data frame transmitted from a communication partner.

(5) [Perform ACK grouping by destination / source pair]
The optical communication system and the communication terminal according to any one of (1) to (4), wherein it is determined from the destination and the transmission source described in the frame that the frames are continuous reception confirmation frames.

(6) [Perform ACK grouping when ACK number increment is below threshold]
Judge that it is a consecutive acknowledgment frame when the increment of the acknowledgment number of the received acknowledgment frame from the acknowledgment number described in the previously received acknowledgment frame is within the specified threshold The optical communication system and the communication terminal according to any one of (1) to (4).

(7) [Perform ACK grouping by sequence number]
The optical communication system and the communication terminal according to any one of (1) to (4), wherein it is determined from a sequence number described in a frame that the frames are continuous reception confirmation frames.

(8) [When ACK transmission timing is determined by a number threshold]
(5) to (5), wherein at least the reception confirmation frame with the most advanced reception confirmation number is transmitted among the reception confirmation frames when the number of received reception confirmation frames exceeds a separately determined threshold value. (7) The optical communication system and communication terminal according to any one of the above.

(9) [When ACK transmission timing is determined by time threshold]
Among the received reception confirmation frames, when at least a predetermined threshold has elapsed from the first reception time, at least the reception confirmation frame with the most advanced reception confirmation number is transmitted among the reception confirmation frames. The optical communication system and the communication terminal according to any one of (5) to (7).

(10) [When receiving ACK threshold is set based on congestion window]
The optical communication system and the communication terminal according to (8) or (9), wherein the threshold value of the reception confirmation frame is calculated based on a congestion window or an advertisement window.

(11) [When threshold of reception ACK is set based on round trip delay time]
The optical communication system and the communication terminal according to (8) or (9), wherein the threshold value of the reception confirmation frame is calculated based on a round trip delay time.

(12) [When variable threshold of received ACK is made]
The threshold value of the reception confirmation frame is increased from the initial value while the number of reception confirmation frames received per unit time does not decrease, the optical communication system according to (8) or (9), And communication terminals.

(13) [When snooping and acquiring a threshold value]
The optical communication system according to (10) or (11), wherein a window size or a round-trip delay time used as a reference for calculating a threshold value of a reception confirmation frame is acquired by snoop of the reception confirmation frame, and communication Terminal.

(14) [decimate ACK]
The optical communication system and the communication terminal according to (8) or (9), wherein only the frame having the most advanced reception confirmation number is left as the reception confirmation frame, and other reception confirmation frames are discarded. .

(15) [Send immediately after loss detection]
The optical communication system and the communication terminal according to (8) or (9), wherein a reception confirmation frame is immediately transmitted when a reception confirmation frame having the same reception confirmation number is received for a threshold value or more separately defined. .

(16) [Suppress rate increase delay]
When the amount of reception confirmation frames received per unit time exceeds the threshold specified separately, the operation to reduce the number of reception confirmation frames is started. The operation of reducing the number is stopped, the optical communication system and the communication terminal according to (8) or (9).

(17) [A threshold is notified from another terminal]
The optical communication according to (8) or (9), wherein a round-trip delay time or a congestion window value used as a reference for calculating a threshold value of a reception confirmation frame is notified from another terminal and set. System and communication terminal.

(18) [Acquire RTT from the arrival interval of the ACK group]
The optical communication system according to (11), wherein a round trip delay time used as a reference for calculating a threshold value of a reception confirmation frame is acquired from an arrival interval of reception confirmation frames and set.

  According to these configurations, even when communication that needs to return a reception confirmation such as TCP communication is performed, it is possible to know the number of transmissions of reception confirmation per unit time without limiting the communication rate. Based on this, it is possible to set the number of reception confirmation transmissions and the transmission cycle.

  The present invention reduces the frequency of reception confirmation transmission within a range that does not limit the communication rate in communication that needs to return reception confirmation, such as TCP communication, and power saving effect associated with ensuring idle time effective for sleep, It is possible to provide a technology that can simultaneously maintain communication quality.

  The present invention can be applied as a low power consumption technology in a PON including an OLT and an ONU.

1: OLT
2, 6: ONU
3, 8: Optical fiber transmission line 5: HGW
9: Optical splitter 11: Logic unit 12: Transmission / reception unit 13: UNI physical layer unit 21, 51: Traffic monitoring unit 22, 52, 62: Buffers 23, 53, 63: Transmission / reception unit 24, 64: Transmission unit 25, 65: Reception unit 26: Sleep determination / instruction unit 28: Reception confirmation frame monitoring unit 41: Logic unit 42: Transmission / reception unit 43: SNI physical layer unit 56: Sleep determination unit 67: Sleep determination switch unit

Claims (8)

In an optical communication system in which an optical subscriber line terminator (OLT) and an optical network terminator (ONU) perform optical communication via an optical fiber transmission line , data is received at the receiving side. A data transmission method is adopted in which a reception confirmation frame is sent back to the transmission side, and a thinning-out operation is performed on the reception side from the ONU or the ONU to thin out the reception confirmation frame transferred to the transmission side based on a predetermined rule. A sleep control method characterized in that, based on the reception confirmation frame, the number of outputs of a sleep release command issued to the ONU sleepable block is reduced .
  The predetermined rule includes a plurality of the reception confirmations that meet certain requirements until the number of the reception confirmation frames from the count start or the elapsed time from the count start time of the reception confirmation frames reaches a separately defined threshold value. The sleep control method according to claim 1, wherein the frames are grouped so that at least only the latest reception confirmation frame is included.   The sleep control method according to claim 2, wherein the separately defined threshold is set based on a congestion window, an advertisement window, or a round trip delay time.   3. The sleep control method according to claim 2, wherein the separately determined threshold value is increased from an initial value to such an extent that the number of reception confirmation frames per unit time can be maintained.   5. The sleep control method according to claim 1, wherein when the number of reception confirmation frames having the same reception confirmation number exceeds a certain number, the ONU is changed from a sleep state to a wake-up state.   When the amount of the reception confirmation frame per unit time exceeds a specified value, the thinning operation is started, and when the amount of the reception confirmation frame per unit time is less than the predetermined value, the thinning operation is stopped. The sleep control method according to any one of claims 1 to 5, wherein:   An optical communication system in which an OLT and an ONU perform optical communication via an optical fiber transmission line, and an optical communication system including a sleep control unit that implements the sleep control method according to claim 1.   An ONU having the sleep control means provided in the optical communication system according to claim 7.

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