JP2006340078A - Flow control method and apparatus thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To highly accurately measure a single direction delay time while using an inexpensive quartz clock or the like. <P>SOLUTION: A transmitter side apparatus stores the predetermined number of calculation results of the single direction delay time informed from a receiver side apparatus, calculates the deviation of variation in the delay time from the predetermined number of stored calculation results, and corrects the single direction delay time to be informed from the receiver side apparatus on the basis of the deviation of variation in the delay time acquired by calculation. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a flow control method for controlling the communication speed of packet communication using IP (Internet Protocol) or the like.

  In the Internet, IP, which is a best effort protocol, is used. Generally, TCP (Transmission Control Protocol) is used as an upper protocol of IP. TCP has functions of retransmission control for performing data arrival compensation and flow control for adjusting communication speed.

  TCP flow control is realized by a mechanism that dynamically changes the window size, that is, the buffer size on the transmission side. There are two purposes used. The first is to realize a communication speed according to the capability of the receiving side by matching with the buffer size of the receiving side. The second is to realize congestion avoidance control by setting the communication speed to avoid the congestion state of the network.

  Various methods have been proposed and implemented as the second congestion avoidance control mechanism. There is a method called TCP Reno as a general congestion avoidance control method. In TCP Reno flow control, control is performed such that the window size is gradually increased, that is, the communication speed is increased, and if a data loss occurs during transfer, the window size is halved.

  There is also a method called TCP Vegas. In this case, the window size is controlled based on RTT (Round Trip Time) between the transmission side and the reception side. When the network is congested, a phenomenon is observed in which the amount of data accumulated in the queues of routers in the network increases and the delay time increases, and the window size is controlled based on this observation result. This is intended to realize communication that does not cause data loss, and can be said to be control that improves throughput by reducing the number of times of performing retransmission control.

  An RTT measurement method will be described with reference to FIG. First, the transmission side device 1 sends out a packet 3 in which the time of the clock 2 built in the transmission side device 1 is marked toward the reception side. The packet 3 passes through the network N, reaches the reception side device 5, and is sent out toward the return transmission side device 1. The transmitting apparatus 1 calculates the RTT by comparing the arrival time of the returned packet 4 with the time stamped on the packet 4.

  TCP Vegas has many advantages over TCP Reno, such as low throughput stability and low delay (for details of the flow control method of TCP Vegas, see Non-Patent Document 1, for example).

L. Brakmo, L.M. Peterson, “TCP Vegas: End to End Congestion Aviation on a Global Internet” IEEE Journal on Selected Areas in Communications, Vol. 8, pg. 1465-1480, October

  TCP Vegas uses a round-trip delay time such as RTT, but may not accurately represent the congestion status in the network. This is because the delay time varies greatly depending on the congestion state of the return path. Therefore, in order to accurately represent the congestion state in the network, it is desirable to perform control using the one-way delay time from the transmission side to the reception side. Hereinafter, in this specification, the one-way delay time is described as OWT (One Way trip Time).

  An example of an OWT measurement method will be described with reference to FIG. First, the transmission side device 6 sends out a packet 8 in which the time of the clock 7 built in the transmission side device 6 is stamped to the reception side device 10. The packet 8 reaches the receiving side through the network. One-way delay time (OWT) is calculated by comparing the time stamped on the arrived packet 8 with the time of the clock 11 built in the receiving apparatus 10. The calculation result is transmitted to the transmission side apparatus 6 (packet 9).

  Since the RTT is a round-trip delay time, the clock for measuring the delay time is the clock 2 of the transmission side apparatus 1. That is, the transmission time and the reception time are recorded by the same clock 2, and the delay time is measured. On the other hand, when measuring the OWT, the clock that records the transmission time is the clock 7 of the transmission side device 6, and the clock that records the reception time is the clock 11 of the reception side device 10, and the clock to be recorded is different. This means that the accuracy of the watch is important.

  In order to improve the accuracy of the timepieces 7 and 11 of the transmission side device 6 and the reception side device 10, for example, a method of using a cesium or rubidium timepiece for both transmission and reception is conceivable. For example, if the accuracy of the rubidium clock is ± 10 ^ -10, the deviation of the clock for transmission and reception is about 0.02 ms per day. If the absolute value of the delay time is on the order of 1 ms or more, there is an error of 2% or less, and it has sufficient accuracy for measuring the delay time. For example, the transmission / reception clock is adjusted only once a day. Is enough.

  In general, a clock of rubidium or cesium is expensive, and it is desirable to use an inexpensive quartz clock or the like. However, the quartz watch generally has an accuracy of about ± 10 ^ -6. In this case, the time difference between the sending and receiving clocks is about 200 ms per day, and in order to measure with the same accuracy as the above rubidium, it is necessary to set the sending and receiving clocks at a frequency of at least once every 10 seconds. is there.

  As described above, there is a problem that the timepiece used in the high-accuracy measurement of OWT is expensive because it is necessary to use a rubidium or cesium timepiece.

  The present invention has been made under such a background, and an object of the present invention is to realize a flow control capable of performing highly accurate OWT measurement while using an inexpensive quartz watch or the like. To do.

  The concept of timepiece accuracy in the present invention will be described. The accuracy of the watch may change due to external factors such as temperature, but it is considered to be an almost constant deviation if the environment is stable. For example, when the accuracy is ± 10 ^ -6 with a quartz watch, the deviation between the two quartz watches falls within a certain value within 2 millionth of a second.

In the present invention, the clock is corrected by utilizing the fact that the deviation between the two clocks for transmission and reception is constant as described above. A method of time correction will be described. FIG. 3 shows an example in which the time course of OWT is plotted without correcting the transmission / reception clock. In FIG. 3, the horizontal axis represents elapsed time, and the vertical axis represents OWT. Although the OWT varies depending on the congestion state of the network, a certain correlation appears between the elapsed time and the OWT. For example, a linear expression (graph 50)
y = ax + b
It can be described by. The slope a of the linear expression is the deviation between the two watches. The calculation result of OWT is corrected using this information.

  As described above, it is possible to realize the flow control using the result of the OWT subjected to the clock correction.

  That is, the first aspect of the present invention is used for packet communication between one transmission side device and one reception side device, and is based on OWT between the transmission side device and the reception side device. This is a flow control method for estimating the congestion state of the device and controlling the communication speed between the transmission side device and the reception side device according to the estimation result.

  Here, a feature of the present invention is that the transmitting side device executes a step of marking a packet with a transmission time based on a clock in the own device, and the receiving side device is based on a clock in the own device. A delay calculation step of calculating an OWT by calculating a difference between the reception time of the packet and a transmission time stamped on the packet, and a step of notifying the transmission side device of a calculation result of the delay calculation step. And the transmission side device holds a predetermined number of calculation results notified from the reception side device, and a time variation calculation step of calculating a deviation of time variation of the delay time from the held predetermined number of calculation results; And a step of correcting the OWT notified from the receiving side device based on the deviation of the time variation of the delay time obtained by the time variation calculating step. In the filtrate.

  Alternatively, the present invention is used for packet communication between one transmitting device and a plurality of receiving devices, and estimates the congestion state in the network based on OWT between the transmitting device and the receiving device. And a flow control method for controlling a communication speed between the transmission side device and the reception side device according to the estimation result.

  Here, a feature of the present invention is that the transmitting side device executes a step of marking a packet with a transmission time based on a clock in the own device, and the receiving side device is based on a clock in the own device. A delay calculation step of calculating an OWT by calculating a difference between the reception time of the packet and a transmission time stamped on the packet, and a step of notifying the transmission side device of a calculation result of the delay calculation step. The transmission side device holds a predetermined number of calculation results notified from the plurality of reception side devices for each of the reception side devices, and a predetermined number of calculation results held for each of the reception side devices. A time variation calculating step for calculating a deviation of the time variation of the delay time for each receiving side device, and the receiving side device obtained by this time variation calculating step There OWT notified from a plurality of the receiving apparatus based on the deviation of the time variation of the delay time of the at executing and correcting each.

  At this time, a step of extracting the largest value among the plurality of OWTs corrected by the correcting step as a value used for communication speed control can be executed.

  As a result, it is possible to detect a transmission path that is most likely to be in a congestion state, and to set a communication speed at which this transmission path does not fall into a congestion state.

  Alternatively, a step of extracting a maximum value excluding a value equal to or higher than a threshold value among a plurality of OWTs corrected by the correcting step as a value used for communication speed control can be executed.

  In other words, performing communication speed control based on the largest value among a plurality of OWTs can be said to be the most secure communication speed control for the purpose of avoiding congestion. If the OWT becomes abnormally large due to the occurrence of a failure, etc., the communication speed of the transmission path in which the failure has occurred is unified to the communication speed of other normal transmission paths. As a result, the communication speed cannot be controlled correctly.

  In order to avoid such a situation, it is desirable to set a threshold value for ignoring OWT that seems to be abnormal and perform communication speed control.

  Furthermore, the transmission-side apparatus can prohibit communication with the reception-side apparatus whose corrected OWT is equal to or greater than a threshold value.

  According to this, it is possible to prohibit communication performed using a transmission path that has become an OWT that is apparently abnormal due to a transmission path failure or the like, and to eliminate invalid communication.

  The time variation calculation step may execute a step of formulating a deviation of OWT time variation as a linear expression. In deriving the linear expression, a least square method can be used. Such a simple method can be used to correct OWT, which is a feature of the present invention.

  A second aspect of the present invention is a transmission side device provided with means for executing the flow control method of the present invention.

  In addition, a third aspect of the present invention is a receiving side device including means for executing the flow control method of the present invention.

  A fourth aspect of the present invention is a program that, when installed in an information processing apparatus, causes the information processing apparatus to realize a function corresponding to the transmission side apparatus or the reception side apparatus of the present invention.

  By recording the program of the present invention on a recording medium, the information processing apparatus can install the program of the present invention using the recording medium. Alternatively, the program of the present invention can be directly installed in the information processing apparatus via a network from a server holding the program of the present invention.

  Thereby, the transmission side apparatus or the reception side apparatus of this invention is realizable using a general purpose information processing apparatus.

  According to the present invention, it is possible to realize high-precision flow control by OWT using an inexpensive timepiece such as a quartz timepiece.

(First Example)
A first embodiment of the present invention in one-to-one packet communication between transmission and reception will be described with reference to FIGS. FIG. 4 is an overall configuration diagram of one-to-one packet communication for transmission and reception. FIG. 5 is a block diagram of the transmission side apparatus of the first embodiment. FIG. 6 is a block diagram of the receiving side apparatus of the first embodiment. FIG. 7 is a flowchart for performing flow control of the first embodiment. FIG. 8 shows an example of changes in the elapsed time of OWT, with the elapsed time on the horizontal axis and the OWT on the vertical axis.

  As shown in FIG. 4, the first embodiment is used for packet communication between one transmission-side device 60 and one reception-side device 70, and OWT between the transmission-side device 60 and the reception-side device 70. Is a flow control method for estimating a congestion state in the network N and controlling the communication speed between the transmission side device 60 and the reception side device 70 according to the estimation result.

  Here, the feature of the first embodiment is that, as shown in FIG. 5, the transmission side device 60 performs a step of marking the transmission time on the packet by the OWT packet generation unit 15 based on the clock 13 in the own device. Then, as shown in FIG. 6, the receiving side device 70 calculates the difference between the reception time of the packet based on the clock 24 in the device itself and the transmission time stamped on the packet by the OWT calculation unit 25. Thus, the delay calculation step for calculating the OWT and the step of notifying the transmission side device 60 of the calculation result of the delay calculation step by the OWT result transmission unit 26 are executed. The transmission side device 60 notifies the reception side device 70 of the notification. A step of holding a predetermined number of calculated results in the OWT result holding unit 19, and a deviation of time variation of the delay time from the predetermined number of calculation results held in the OWT result holding unit 19 The OWT correction unit 18 corrects the OWT notified from the receiving side device 70 based on the time variation calculation step calculated by the time variation deviation calculation unit 17 and the deviation of the time variation of the delay time obtained by the time variation calculation step. The step is to execute.

  Hereinafter, the flow control method of the first embodiment will be described in detail.

  First, as shown in step S1 of FIG. 7, the OWT packet generator 15 generates an OWT packet with the time stamped by the clock 13 built in the transmitter apparatus 60 from the transmitter apparatus 60, and sends it to the output buffer 21. Output from the output unit 23.

  Next, as shown in step S <b> 2, the OWT packet transmitted from the transmission side device 60 is received by the input unit 29 of the reception side device 70 and sent to the input buffer 27.

  Next, as shown in step S3, the OWT calculation unit 25 calculates OWT. The OWT value is a difference between the time by the clock 24 built in the receiving side device 70 and the time stamped in the OWT packet.

  Next, as shown in step S <b> 4, the OWT result transmission unit 26 generates a packet in which the OWT calculation result is engraved, sends the packet to the output buffer 28, and transmits the output unit 30 to the transmission side device 60.

  Next, as shown in step S <b> 5, the packet on which the result of calculating the OWT is imprinted by the input unit 22 of the transmission side device 60 is received, sent to the input buffer 20, and held by the OWT result holding unit 19.

  Next, as shown in step S <b> 6, the time variation deviation calculation unit 17 calculates a time variation deviation from the past N OWT values.

As a method of calculating the deviation of the time fluctuation, the past N OWT values are linearized by the least square method. The primary expression is y = ax + b
And The y-axis is OWT and the x-axis indicates elapsed time. The coefficient a is the deviation, and the constant term b is the OWT value at the reference time when OWT correction is performed. That is, the OWT value is obtained when the time of the transmission side device 60 and the reception side device 70 are combined.

  Further, instead of directly obtaining a linear expression from the past N OWT values, an average value of OWT for a certain period may be obtained, and a linear expression may be obtained from the average value. The graph of FIG. 8 is a diagram in which OWT values in a certain network are plotted with an average value of about every minute over about two days. The graph 32 is a linear graph obtained from the graph 31 by the least square method.

Next, as shown in step S7, the OWT correction unit 18 corrects the OWT. As a correction method, when the OWT value at time t is OWT [t] and the correction value is OWT ′ [t],
OWT ′ [t] = OWT [t] + (at + b)
It becomes.

Next, as shown in step S7, the communication speed calculation unit and the control unit 14 calculate the communication speed according to the OWT value. As a calculation method, when the OWT value when congestion does not occur is set to baseOWT, the same method as TCP Vegas,
1-baseOWT / OWT
There is a method of determining according to the value of.

  Next, as shown in step S8, the communication speed calculation unit and control unit 14 controls the communication speed based on the value calculated in step S7.

(Second embodiment)
A second embodiment of the present invention in 1-n packet transmission and reception will be described with reference to FIGS. FIG. 9 is an overall configuration diagram of packet communication in which transmission and reception are 1 to n. FIG. 10 is a block diagram of the transmission side apparatus of the second embodiment. The block diagram of the receiving side apparatus of the second embodiment is the same as that of FIG. 6 of the first embodiment. FIG. 11 is a flowchart for performing the flow control of the second embodiment.

  As shown in FIG. 9, the second embodiment is used for packet communication between one transmission-side device 61 and a plurality of reception-side devices 70, and OWT between the transmission-side device 61 and the reception-side device 70. Is a flow control method for estimating the congestion state in the network N and controlling the communication speed between the transmission side device 61 and the reception side device 70 according to the estimation result.

  Here, the feature of the second embodiment is that, as shown in FIG. 10, the transmitting side device 61 performs a step of marking the transmission time on the packet by the OWT packet generating unit 36 based on the clock 33 in the own device. Then, as shown in FIG. 6, the receiving side device 70 calculates the difference between the reception time of the packet based on the clock 24 in the device itself and the transmission time stamped on the packet by the OWT calculation unit 25. Thus, the delay calculation step for calculating the OWT and the step of notifying the transmission side device 61 of the calculation result of the delay calculation step by the OWT result transmission unit 26 are executed. The transmission side device 61 includes a plurality of reception side devices 70. A predetermined number of the calculation results notified from each of the receiving side devices 70 in the OWT result holding unit 40 and an OWT result holding unit in each of the receiving side devices 70 A time variation calculation step for calculating the deviation of the time variation of the delay time for each receiving side device 70 from the predetermined number of calculation results held at 0 by the time variation deviation calculation unit 38, and the reception obtained by this time variation calculation step The OWT correction unit 39 corrects the OWT notified from the plurality of reception side devices 70 based on the deviation of the time variation of the delay time for each side device 70.

  At this time, the step of extracting the largest value among the plurality of OWTs corrected by the correction step by the OWT value comparison unit 34 as a value used for communication speed control is executed.

  In this embodiment, the OWT value comparison unit 34 further includes a step of extracting, as a value used for communication speed control, a maximum value excluding a value equal to or greater than a threshold value among the plurality of OWTs corrected by the correcting step. Execute.

  Then, the communication speed calculation unit and the control unit 35 of the transmission side device 61 perform communication control so as to prohibit communication with the reception side device 70 whose corrected OWT is equal to or greater than the threshold value.

  Hereinafter, the flow control method of the second embodiment will be described in detail.

  First, as shown in step S9 of FIG. 11, the OWT packet generator 36 generates an OWT packet with the time stamped by the clock 33 built in the transmitter device 61 from the transmitter device 61, and sends it to the output buffer 42. Output from the output unit 44.

  Next, as shown in step S <b> 10, the OWT packet transmitted from the transmission side device 61 is received by the input unit 29 of each reception side device 70 and sent to the input buffer 27.

  Next, as shown in step S11, the OWT calculation unit 25 calculates OWT. The OWT value is a difference between the time by the clock 24 built in the receiving side device 70 and the time stamped in the OWT packet.

  Next, as shown in step S <b> 12, the OWT result transmission unit 26 generates a packet imprinted with the OWT calculation result, sends the packet to the output buffer 28, and transmits the output unit 30 to the transmission side device 61.

  Next, as shown in step S <b> 13, the packet on which the result of calculating the OWT is stamped by the input unit 43 of the transmission side device 61 is received, sent to the input buffer 41, and held by the OWT result holding unit 40.

  Next, as shown in step S14, the time fluctuation deviation calculation unit 38 calculates a deviation of time fluctuation from the past N OWT values. The method for calculating the deviation of the time variation is the same as the method described in the first embodiment.

  Next, as shown in step S <b> 15, the OWT value comparison unit 34 compares the OWT values transmitted from the n receiving side devices 70. As a comparison method, as described above, a value having the largest OWT value is selected. Alternatively, the maximum OWT value excluding a value equal to or greater than the threshold value is selected.

  Next, as shown in step S16, the OWT correction unit 39 corrects the OWT value.

  Next, as shown in step S <b> 17, the communication speed calculation unit and the control unit 35 calculate the communication speed according to the OWT value.

  Next, as shown in step S18, the communication speed calculation unit and control unit 35 controls the communication speed based on the value calculated in step S17.

  Further, the communication speed calculation unit and the control unit 35 can also perform communication control so as to prohibit communication with the receiving-side device 70 whose OWT value is equal to or greater than the threshold value.

(Third embodiment)
The third embodiment is a program that, when installed in a general-purpose information processing apparatus, causes the information processing apparatus to realize a function corresponding to the transmission side apparatus or the reception side apparatus of the present embodiment. This program is recorded in a recording medium and installed in the information processing apparatus, or installed in the information processing apparatus via a communication line, so that the information processing apparatus receives the transmission side devices 1, 6, 60, 61, and reception. Functions corresponding to the side devices 5, 10 and 70 can be realized.

  According to the present invention, it is possible to realize high-precision flow control by OWT using an inexpensive watch such as a quartz watch, so that the network operation efficiency can be improved by low-cost equipment investment. it can.

The figure explaining the measuring method of RTT. The figure explaining the measuring method of OWT. The figure showing the time change of OWT. 1 is a diagram illustrating the overall configuration of one-to-one packet communication between transmission and reception. The block block diagram of the transmission side apparatus of a 1st Example. The block block diagram of the receiving side apparatus of a 1st Example. The flowchart for performing the flow control of a 1st Example. The figure which shows an example of the measured value of OWT. The whole block diagram of 1 to n packet communication of transmission and reception. The block block diagram of the transmission side apparatus of a 2nd Example. The flowchart for performing the flow control of 2nd Example.

Explanation of symbols

1, 6, 60, 61 Transmission side device 2, 7, 11, 13, 24, 33 Clock 3, 4, 8, 9 Packet 5, 10, 70 Reception side device 14, 35 Communication speed calculation unit and control unit 15, 36 OWT packet generation unit 16, 37 Output control unit 17, 38 Time variation deviation calculation unit 18, 39 OWT correction unit 19, 40 OWT result holding unit 20, 27, 41 Input buffer 21, 28, 42 Output buffer 22, 29, 43 Input unit 23, 30, 44 Output unit 25 OWT calculation unit 26 OWT result transmission unit 31, 32, 50 Graph 34 OWT value comparison unit N Network

Claims (10)

Used for packet communication between one transmitting device and one receiving device, estimating the congestion state in the network based on the one-way delay time between the transmitting device and the receiving device, and In a flow control method for controlling a communication speed between the transmission side device and the reception side device according to an estimation result,
The transmission side device executes a step of marking a transmission time on a packet based on a clock in its own device,
The receiving side device
A delay calculating step of calculating a one-way delay time by calculating a difference between a reception time of the packet based on a clock in its own device and a transmission time stamped on the packet;
Performing the step of notifying the transmission side device of the calculation result of the delay calculation step;
The transmitting device is:
Holding a predetermined number of calculation results notified from the receiving side device;
A time fluctuation calculating step for calculating a deviation of the time fluctuation of the delay time from the predetermined number of calculation results held;
And a step of correcting the one-way delay time notified from the receiving side device based on the deviation of the time fluctuation of the delay time obtained by the time fluctuation calculating step. Used for packet communication between one transmitting device and a plurality of receiving devices, estimating a congestion state in the network based on a one-way delay time between the transmitting device and the receiving device, In a flow control method for controlling a communication speed between the transmission side device and the reception side device according to an estimation result,
The transmission side device executes a step of marking a transmission time on a packet based on a clock in its own device,
The receiving side device
A delay calculating step of calculating a one-way delay time by calculating a difference between a reception time of the packet based on a clock in its own device and a transmission time stamped on the packet;
Performing the step of notifying the transmission side device of the calculation result of the delay calculation step;
The transmitting device is:
Holding a predetermined number of calculation results notified from a plurality of the receiving side devices for each of the receiving side devices;
A time fluctuation calculating step for calculating a deviation of a time fluctuation of a delay time for each of the receiving side devices from a predetermined number of calculation results held for each of the receiving side devices;
Correcting each one-way delay time notified from a plurality of the receiving side devices based on a deviation of the time fluctuation of the delay time for each receiving side device obtained by the time fluctuation calculating step. A flow control method.   The flow control method according to claim 2, wherein a step of extracting the largest value among the plurality of one-way delay times corrected by the correcting step as a value used for communication speed control is executed.   The flow control method according to claim 2, wherein a step of extracting a maximum value excluding a value equal to or greater than a threshold value among a plurality of one-way delay times corrected by the correcting step as a value used for communication speed control is executed.   The flow control method according to claim 4, wherein the transmission side device prohibits communication with the reception side device whose corrected one-way delay time is equal to or greater than a threshold value.   The flow control method according to claim 1, wherein the time variation calculation step executes a step of formulating a deviation of the time variation of the one-way delay time as a linear expression.   The flow control method according to claim 6, wherein a least square method is used in deriving the linear expression.   A transmission-side apparatus comprising means for executing the flow control method according to claim 1.   A receiving-side apparatus comprising means for executing the flow control method according to claim 1.   A program that, when installed in an information processing device, causes the information processing device to realize a function corresponding to the transmission side device according to claim 8 or the reception side device according to claim 9.

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