JP6501138B2 - Delay measurement method, delay measurement device, and program - Google Patents

Description

  The present invention relates to a delay measurement method, a delay measurement device, and a program.

  In recent years, in a delay measurement method for measuring a delay of packet transmission between two devices, an offset value of time between devices is calculated from transmission / reception time of a round trip packet etc. between two devices, and the offset value is used There is known a method of measuring transmission delay by synchronizing time between two devices (see, for example, Patent Document 1).

US Patent Application Publication No. 2014/0056318

  However, since the accuracy of the clock for measuring the time of each device is not necessarily the same among the devices, the above-described delay measurement method may not be able to accurately measure the transmission delay between the devices.

  The present invention has been made to solve the above problems, and an object thereof is to provide a delay measurement method, a delay measurement device, and a program capable of more accurately measuring a transmission delay between devices.

In order to solve the above-mentioned problems, one aspect of the present invention repeatedly transmits and receives a reciprocating message between a first device and a second device, and the first device and the second in the reciprocating message are repeatedly transmitted and received. A transmitting / receiving step of measuring each transmission time and reception time with the device, a time difference between the transmission times of each of two transmission messages transmitted from the first device, and a second device receiving Calculating a clock error per unit time between the first device and the second device based on the time difference between the reception times of the two transmission messages. Based on the transmission time and the reception time, the minimum value of the round trip transmission delay value which is the round trip transmission delay value in the round trip message is extracted, and based on the extracted minimum value. There are a time difference calculating step of calculating a unit time difference indicating a time difference at the reference time of the first device and the second device, and the clock error per least unit time, based on said device time differences A correction step of correcting the transmission time and the reception time in the second device of the reciprocation message, and monitoring the reciprocation message periodically, and the reciprocation message indicates the clock error or the inter-device time difference when updating satisfies a predetermined condition, see contains an update step of updating the clock error, or the device time difference, and if the predetermined condition is satisfied, among the forward packet TTL (time to Live) is The first condition that the return messages are equal and the TTLs of return packets are equal, and the first condition The delay measurement method is characterized in that two round-trip messages satisfying the second condition that the back-transmission delay values are equal or close round-trip messages are obtained .

Further, according to one aspect of the present invention, in the delay measurement method described above, the first device and the second device may be determined based on the transmission time and the reception time of the second device corrected by the correction step. The method is characterized by including an estimation step of estimating a transmission delay between itself and the device.

  Further, according to one aspect of the present invention, in the above delay measurement method, the error calculation step selects at least two of the round-trip messages in which a difference between round-trip transmission delay values in the round-trip messages is within a predetermined range. The clock error is calculated based on the time difference between the transmission time and the reception time in two transmission messages of at least two of the two round-trip messages selected by the first step and the first step. And the second step.

  Further, according to one aspect of the present invention, in the delay measurement method described above, at least two of the two or more round trip messages in which the difference between the round trip transmission delay values is minimized among the plurality of round trip messages in the first step. To select.

  Further, according to one aspect of the present invention, in the above-mentioned delay measurement method, in the second step, when there are three or more reciprocating messages selected by the first step, the time difference of the transmission time is The clock error may be calculated based on a time difference between the transmission times of the two transmission messages that are maximized and a time difference between the reception times.

  Further, according to one aspect of the present invention, in the above-mentioned delay measurement method, in the second step, the three or more transmissions are performed when the number of round trip messages selected by the first step is three or more. A plurality of the clock errors are calculated based on the message, an average clock error which is an average value of the calculated plurality of clock errors is calculated, and the correction step calculates the round trip message based on the average clock error. A transmission time and the reception time are corrected.

  Further, according to one aspect of the present invention, in the above-mentioned delay measurement method, the minimum value of the round trip transmission delay value, which is the round trip transmission delay value in the round trip message, is extracted based on the transmission time and the reception time. Calculating an inter-apparatus time difference indicating an inter-apparatus time difference between the first apparatus and the second apparatus based on the minimum value, and calculating the clock per unit time in the correcting step. The transmission time and the reception time of the reciprocating message may be corrected based on an error and the inter-device time difference.

  Further, according to one aspect of the present invention, in the above-described delay measurement method, the time difference calculating step corresponds to the reciprocation message in which a reciprocation transmission delay value in one of the plurality of reciprocation messages is minimized among the plurality of the reciprocation messages. The round trip transmission delay value is extracted as the minimum value.

  Further, according to one aspect of the present invention, in the above-described delay measurement method, in the time difference calculation step, the transmission delay value of the forward path which becomes the minimum among the transmission delay values of the plurality of outward paths corresponding to the plurality of reciprocating messages; It is characterized in that an added value with a return transmission delay value which is the smallest among transmission delay values of a plurality of return paths corresponding to a plurality of the return messages is extracted as the minimum value.

  Moreover, one aspect of the present invention is characterized in that, in the above-mentioned delay measurement method, the minimum value is extracted based on the transmission time and the reception time corrected based on the clock error.

  Further, according to one aspect of the present invention, in the above-described delay measurement method, the round trip message is periodically monitored, and the round trip message satisfies a predetermined condition for updating the clock error or the inter-device time difference. And updating the clock error or the inter-device time difference.

Further, according to one aspect of the present invention, transmission and reception of reciprocating messages between the first device and the second device are repeatedly transmitted and received, and transmission of the first device and the second device in the reciprocating messages is performed. A transmitting / receiving step of measuring a time and a reception time, a time difference between each of the transmission times between two transmission messages transmitted from the first device, and two transmission messages received by the second device Acquiring a clock error per unit time between the first device and the second device, which is calculated based on the time difference between the reception times of each of the transmission time, and the transmission time And extracting the minimum value of the round trip transmission delay value, which is the round trip transmission delay value in the round trip message, based on the reception time, and based on the extracted minimum value, The reciprocation message based on a time difference calculating step of calculating an inter-device time difference indicating a time difference between a first device and the second device at a reference time, the clock error per unit time, and the inter-device time difference wherein the step of correcting the transmission time and the reception time of the second apparatus, based on the transmission time and the reception time of the corrected second device by said correction step, the first device Estimating the transmission delay between the second device and the second device, and monitoring the reciprocation message periodically, and the predetermined condition that the reciprocation message updates the clock error or the inter-device time difference. If meet, the clock error, or the saw including an updating step of updating the device time difference, and if the predetermined condition is satisfied A first condition that TTL (Time To Live) of forward packets are equal and a TTL of return packets is equal, and a second condition that the round trip transmission delay values are equal or close The delay measurement method is characterized in that two round trip messages to be satisfied are obtained .

Further, according to one aspect of the present invention, transmission and reception of reciprocating messages between the first device and the second device are repeatedly transmitted and received, and transmission of the first device and the second device in the reciprocating messages is performed. A transmitting / receiving step of measuring a time and a reception time, a time difference between each of the transmission times between two transmission messages transmitted from the first device, and two transmission messages received by the second device Calculating a clock error per unit time between the first device and the second device based on the time difference between the reception times of each of the transmission time and the reception time. The minimum value of the round trip transmission delay value which is the round trip transmission delay value in the round trip message is extracted based on the time, and the first parameter is extracted based on the extracted minimum value. Calculating an inter-apparatus time difference indicating a time difference between the first apparatus and the second apparatus at a reference time, and periodically monitoring the reciprocation message, and the reciprocation message indicates the clock error or the inter-apparatus time difference when updating satisfies a predetermined condition, see contains an update step of updating the clock error, or the device time difference, and if the predetermined condition is satisfied, among the forward packet TTL (time to Live) is When the two round trip messages having the first condition that the TTLs of the return packets are equal and the round-trip messages equal to each other and the second condition that the round-trip transmission delay values are equal or close round-trip messages are obtained It is a delay measurement method characterized by being.

Further, according to one aspect of the present invention, a reciprocating message reciprocating between the first device and the second device is repeatedly transmitted and received, and transmission time of each of the first device and the second device in the reciprocating message is transmitted. And an acquisition unit for acquiring the reception time, a time difference between the transmission times of the two transmission messages transmitted from the first device, and two transmission messages of the two transmission messages received by the second device. An error calculator configured to calculate a clock error per unit time between the first device and the second device based on a time difference between the reception times of each of the transmission time and the reception time; Based on the minimum value of the round trip transmission delay value which is the round trip transmission delay value in the round trip message, and the first apparatus and the second apparatus are extracted based on the extracted minimum value. A time difference calculating section for calculating a unit time difference indicating a time difference at the reference time of the location, and the clock error per least unit time, based on said inter-device time difference, the in the second device of the reciprocating message A correction unit that corrects the transmission time and the reception time, and monitoring the round trip message periodically, and the clock when the round trip message satisfies the clock error or a predetermined condition for updating the inter-device time difference, the clock An error, or an update unit for updating the inter-device time difference, and in the case where the predetermined conditions are satisfied, it is a round trip message in which TTL (Time To Live) of forward packets is equal and TTL of return packets is equal. That the first condition that there is, and that the round trip transmission delay values are equal or close round trip messages The second embodiment of the present invention is a delay measurement apparatus characterized in that two of the two round-trip messages that satisfy the second condition are obtained .

Further, according to one aspect of the present invention, a computer repeatedly transmits and receives a reciprocating message between a first device and a second device, and transmits and receives between a first device and a second device in the reciprocating message. A transmitting / receiving step of measuring each transmission time and reception time, a time difference between each of said transmission times between two transmission messages transmitted from said first device, and two received by said second device An error calculating step of calculating a clock error per unit time between the first device and the second device based on a time difference between the reception times of the transmission messages; and the transmission time And the minimum value of the round trip transmission delay value which is the round trip transmission delay value in the round trip message based on the reception time, and based on the extracted minimum value , The first device and the time difference calculating step of calculating a unit time difference indicating a time difference at the reference time of the second device, and the clock error per least unit time, based on said inter-device time difference, A correction step of correcting the transmission time and the reception time in the second device of the reciprocation message, monitoring the reciprocation message periodically, and updating the clock error or the inter-device time difference of the reciprocation message And the update step of updating the clock error or the inter-device time difference is executed, and the TTL (Time To Live) of the forward packets is equal to the case where the predetermined condition is satisfied. And the first condition that the TTLs of return packets are equal to each other in the same round trip message, and It is a program which is a case where two said round-trip messages which satisfy the 2nd condition which are the same or near round-trip messages whose return transmission delay value is equal are obtained .

  According to the present invention, the transmission delay between devices can be measured more accurately.

FIG. 1 is a block diagram showing an example of a delay measurement system and a delay measurement device according to a first embodiment. It is a figure explaining the transmission time in the reciprocation message of 1st Embodiment, and reception time. It is a figure which shows the example of data of the time information storage part in 1st Embodiment. It is a figure which shows the example of data of the correction information storage part in 1st Embodiment. It is a figure explaining the time difference between the devices in a 1st embodiment. It is a figure explaining the clock error in a 1st embodiment. It is a figure which shows an example of calculation processing of the clock error in 1st Embodiment. It is a figure which shows an example which extracts the minimum value of the round trip transmission delay value by a round trip delay method. It is a figure which shows an example which extracts the minimum value of the round trip transmission delay value by a one way delay method. It is a figure which shows an example of the calculation process of the time difference between apparatuses in 1st Embodiment. It is a flowchart which shows an example of the delay measurement method by the delay measurement system of 1st Embodiment. It is a flowchart which shows an example of calculation processing of the clock error by 1st Embodiment. It is a flowchart which shows an example of the calculation process of the time difference between apparatuses by 1st Embodiment. It is a block diagram showing an example of a delay measurement system and a delay measurement device according to a second embodiment. It is a flowchart which shows an example of the delay measurement method by the delay measurement system of 2nd Embodiment.

Hereinafter, a delay estimation method and a delay measurement system according to an embodiment of the present invention will be described with reference to the drawings.
First Embodiment
FIG. 1 is a block diagram showing an example of a delay measurement system 1 and a delay measurement apparatus 10 according to the present embodiment.

As shown in this figure, the delay measurement system 1 includes an NW (network) device 100 and an NW device 200 connected via a network NW1. Here, the NW device 100 (an example of a first device) is a device that measures the transmission delay of packets with the NW device 200, and, for example, a computer device such as a personal computer, a PDA (Personal Digital Assistant), It is an apparatus that can be connected to the network NW1, such as a mobile terminal such as a mobile phone.
The NW device 200 (an example of a second device) is a device that can be connected to the network NW1 like the NW device 100, and is a device for which the transmission delay is to be measured.

The NW device 100 further includes a delay measurement device 10, a transmission / reception unit 20, and an input unit 30.
The transmission / reception unit 20 communicates with the NW device 200 via the network NW1. The transmission / reception unit 20 repeatedly transmits and receives a reciprocating message between the NW device 100 and the NW device 200 based on the control of the time acquisition unit 51 of the delay measurement device 10 described later, Each transmission time and reception time with the NW device 200 are measured. Here, the round trip message is a message for measuring a transmission delay of, for example, Ethernet Operations Administration and Maintenance-Delay Measurement (EOAM-DM) or Two-Way Active Measurement Protocol (TWAMP). The round trip message (round trip frame or round trip packet) is composed of the forward packet and the backward packet, and the message received by the NW device 100 includes transmission time T1 and reception time T4 of the NW device 100 as shown in FIG. , Reception time T2 and transmission time T3 of the NW device 200 are included. In communication between the NW device 100 and the NW device 200, the priority of transmission and reception of the reciprocation message may be set higher than transmission and reception of other messages.

FIG. 2 is a diagram for explaining transmission time and reception time in a round trip message according to the present embodiment.
As shown in FIG. 2, time T1 indicates the transmission time of the forward packet transmitted by the transmission / reception unit 20 of the NW device 100, and time T2 indicates the forward packet transmitted by the transmission / reception unit 20 of the NW device 100 in the NW device 200. It shows the reception time. Here, the forward pass transmission delay value d1 which is the forward pass transmission delay value is (T2−T1), but since the clock included in the NW device 100 and the clock included in the NW device 200 are not the same time, the forward pass The transmission delay value d1 is not an accurate forward transmission delay.

Further, time T3 indicates the transmission time of the return packet transmitted by the NW device 200, and time T4 indicates the reception time of the return packet received by the transmission / reception unit 20 of the NW device 100. Here, the return transmission delay value d2 which is the transmission delay value of the return path is (T4-T3), but since the clock included in the NW device 100 and the clock included in the NW device 200 do not indicate the same time, The return transmission delay value d2 is not an accurate forward transmission delay.
A period from time T2 to time T3 indicates a delay caused by internal processing of the NW device 200.
The delay measurement method and the delay measurement apparatus 10 according to the present embodiment corrects the reception time T2 and the transmission time T3 to accurately measure (estimate) the transmission delay value of the forward path and the transmission delay value of the backward path.

Returning to the description of FIG. 1, the transmission / reception unit 20 includes a communication unit 21 and a time stamp giving unit 22.
The communication unit 21 performs data communication by, for example, the Internet protocol.
The time stamp adding unit 22 adds time information (for example, transmission time T1 and reception time T4) to the above-mentioned round trip message for measuring the transmission delay, and time information (for example, reception time T2) included in the round trip message. And transmission time T3). The time stamp adding unit 22 outputs the transmission time T1 and the reception time T4 of the NW device 100, and the reception time T2 and the transmission time T3 of the NW device 200 to the delay measurement device 10.

  The input unit 30 is, for example, an input device such as a keyboard and a mouse, receives various inputs from the user, and outputs the input to the control unit 50. The input unit 30 receives, for example, designation of a method for extracting a minimum round trip transmission delay value described later.

The delay measurement device 10 is, for example, a device for measuring the transmission delay between the NW device 100 and the NW device 200, and includes a storage unit 40 and a control unit 50.
The storage unit 40 stores various information used when measuring the transmission delay between the NW device 100 and the NW device 200. The storage unit 40 includes a time information storage unit 41, a correction information storage unit 42, and a delay information storage unit 43.

  The time information storage unit 41 is information indicating a transmission time (T1, T3) and a reception time (T2, T4) acquired (measured) via the transmission / reception unit 20 by transmitting / receiving a reciprocating message to / from the NW device 200. Remember. For example, as shown in FIG. 3, the time information storage unit 41 associates and stores identification information of a round trip message, a transmission time (T1, T3) and a reception time (T2, T4). For example, as shown in FIG. 3, the time information storage unit 41 has a forward transmission delay value d1 indicating the transmission delay value on the forward path before correction and a return transmission delay value d2 indicating the transmission delay value on the backward path before correction. And a round trip transmission delay value (RDT) indicating a round trip transmission delay value before correction may be further stored in association with identification information of the round trip message.

FIG. 3 is a view showing an example of data of the time information storage unit 41 in the present embodiment.
In the example shown in this figure, the time information storage unit 41 sets “NO.”, “Transmission time T1” and “reception time T2” of “outbound packet”, “transmission time T3” of “return packet”, and The reception time T4, the "forward transmission delay value d1", the "return transmission delay value d2", and the "round trip transmission delay value RDT" are associated and stored. Here, “NO.” Indicates the number of the round trip message (an example of identification information).

Returning to the explanation of FIG. 1 again, the correction information storage unit 42 stores information used when correcting a reception time T2 and a transmission time T3 described later. For example, as shown in FIG. 4, the correction information storage unit 42 includes “reference time (T0)”, “clock error”, “minimum round trip transmission delay value”, and “inter-device time difference (dt)”. Associate and store.
FIG. 4 is a view showing an example of data of the correction information storage unit 42 in the present embodiment.
In this figure, “reference time (T0)” indicates a time that is a reference when correcting a clock error (a fluctuation component due to a clock) described later, and “clock error” is viewed from the NW device 100 described later The value of the slope (CLKslope) of the passage of time of the NW device 200 is shown. The “minimum round trip transmission delay value” indicates the minimum value of the round trip transmission delay value described later, and the “inter-apparatus time difference (dt)” corrects fixed components (offset components) of the reception time T2 and the transmission time T3. Shows the time difference between the devices.

  Referring back to FIG. 1 again, the delay information storage unit 43 stores the result of the transmission delay (for example, one-way delay) measured by the delay measurement apparatus 10. The result of the transmission delay stored in the delay information storage unit 43 is read by a read instruction or various applications received from the user via the input unit 30, and used for processing such as presenting (displaying) to the user .

  The control unit 50 is, for example, a processor including a CPU (Central Processing Unit) or the like, and centrally controls the NW device 100 (delay measurement device 10). The control unit 50 includes a time acquisition unit 51, a clock error calculation unit 52, a time difference calculation unit 53, a time correction unit 54, and a delay calculation unit 55.

  The time acquisition unit 51 (an example of an acquisition unit) repeatedly transmits and receives a reciprocating message, and acquires the transmission time (T1, T3) and the reception time (T2, T4) of the NW device 100 and the NW device 200 in the reciprocating message. Do. The time acquisition unit 51 stores the acquired transmission times (T1, T3) and reception times (T2, T4) in the time information storage unit 41 in association with the identification information of the round trip message as shown in FIG. The time acquisition unit 51 also determines the forward transmission delay value d1, the return transmission delay value d2, and the round trip transmission delay value RDT based on the acquired transmission times (T1, T3) and reception times (T2, T4). calculate. The time acquisition unit 51 associates the identification information of the reciprocation message, the calculated forward transmission delay value d1, the return transmission delay value d2, and the reciprocation transmission delay value RDT, as shown in FIG. Remember.

  The clock error calculation unit 52 (an example of the error calculation unit) is a time difference between transmission times T1 in two transmission messages transmitted from the NW device 100 and a time difference between reception times T2 in two transmission messages received by the NW device 200. And calculates the clock error (CLKslope) per unit time between the NW device 100 and the NW device 200. In the following description, the clock error (CLKslope) per unit time may be simply referred to as the clock error (CLKslope). The clock error calculation unit 52 causes, for example, the time acquisition unit 51 to transmit and receive a reciprocating message a plurality of times (N times) via the transmitting and receiving unit 20, and transmit time (T1, T3) and reception in a plurality of (N) reciprocating messages. The time (T2, T4) is acquired. The clock error calculation unit 52 is a process of selecting at least two reciprocation messages in which the difference between the reciprocation transmission delay value RDT is within a predetermined range from the N reciprocation messages stored in the time information storage unit 41 (first Process). The clock error calculation unit 52 selects, for example, at least two round-trip messages in which the difference between the round-trip transmission delay values RDT is minimized from the N round-trip messages.

Also, the clock error calculation unit 52 calculates the clock error (CLKslope) based on the time difference between the transmission time T1 and the reception time T2 in two transmission messages of the selected at least two round-trip messages ( Execute the second process). For example, when the number of round trip messages selected by the first process described above is three or more, the clock error calculation unit 52 determines the time difference between the transmission time and the reception time of the two transmission messages for which the time difference between the transmission times becomes maximum. The clock error (CLKslope) is calculated based on the time difference of Here, the clock error is a slope (CLKslope) of the passage of time of the NW device 200 viewed from the NW device 100. The clock error calculation unit 52 stores the calculated clock error (CLKslope) in the correction information storage unit 42. Also, the clock error calculation unit 52 stores the transmission time T1 used when calculating the clock error (CLKslope) in the correction information storage unit 42 as a temporary reference time T0.
The details of the process of calculating the clock error (CLKslope) will be described later.

  The time difference calculation unit 53 extracts the minimum value of the round trip transmission delay value which is the round trip transmission delay value in the round trip message based on the transmission time and the reception time, and based on the extracted minimum value, the NW device 100 and NW An inter-apparatus time difference indicating the time difference between the apparatus 200 and the reference time is calculated. The time difference calculation unit 53 causes, for example, the time acquisition unit 51 to transmit and receive a reciprocating message a plurality of times via the transmitting and receiving unit 20, and causes transmission time (T1, T3) and reception time (T2, T4) in a plurality of reciprocating messages to be acquired. . The time difference calculation unit 53 determines the minimum round trip transmission delay value (the minimum value of the round trip transmission delay value) based on, for example, the transmission times (T1 and T3) and the reception times (T2 and T4) stored in the time information storage unit 41. RDTmin) is extracted (calculated), and the inter-device time difference (dt) is calculated based on the minimum round trip transmission delay value (RDTmin). The time difference calculation unit 53 further includes a minimum round trip delay extraction unit 531 and an inter-apparatus time difference calculation unit 532.

  The minimum round trip delay extraction unit 531 has two methods, a round trip delay method and a one-way delay method, based on the transmission times (T1 and T3) and the reception times (T2 and T4) stored in the time information storage unit 41. Thus, the minimum round trip transmission delay value (RDTmin) is extracted. Here, in the round trip delay method, a round trip transmission delay value RDT corresponding to a round trip message in which a round trip transmission delay value RDT in one round trip message is minimum among a plurality of round trip messages is a minimum round trip transmission delay value (RDTmin). It is a method to extract as. Also, with the one-way delay method, the forward transmission delay value (d1 min) that is the smallest of the plurality of forward transmission delay values d1 and the backward transmission delay value (d2 min) that is the minimum of the plurality of backward transmission delay values d2 ) Is extracted as the minimum round trip transmission delay value (RDTmin). In the one-way delay method, the minimum round trip transmission delay value (RDTmin) is extracted by using the reception time T2 and the transmission time T3 corrected based on the clock error (CLKslope) by the time correction unit 54 described later.

The minimum round trip delay extraction unit 531 is, for example, a minimum by one of the above two methods based on designation information specifying a method of extracting the minimum round trip transmission delay value received from the user via the input unit 30. The round trip transmission delay value (RDTmin) is extracted. The minimum round trip delay extraction unit 531 stores the extracted minimum round trip transmission delay value (RDTmin) in the correction information storage unit 42.
The details of the two methods of the round trip delay method described above and the one-way delay method will be described later.

The inter-apparatus time difference calculation unit 532 calculates an inter-apparatus time difference (dt) based on the minimum round trip transmission delay value (RDTmin) extracted by the minimum round trip delay extraction unit 531. The inter-apparatus time difference calculation unit 532 stores the calculated inter-apparatus time difference (dt) in the correction information storage unit 42.
The details of the calculation of the inter-device time difference (dt) will be described later.

The time correction unit 54 (an example of the correction unit) corrects the transmission time T3 and the reception time T2 of the reciprocating message based on at least the clock error (CLKslope). When the time correction unit 54 (correction unit) executes the one-way delay method described above, the reception time is received based on the reference time (T0) stored in the correction information storage unit 42 and the clock error (CLKslope). T2 and transmission time T3 are corrected. Further, when the time correction unit 54 calculates the transmission delay by the delay calculation unit 55 described later, the reference time (T0) stored by the correction information storage unit 42, the clock error, and the inter-device time difference (dt) And correct the reception time T2 and the transmission time T3.
The details of the time correction by the time correction unit 54 will be described later.

  The delay calculation unit 55 (an example of the estimation unit) determines the transmission delay between the NW device 100 and the NW device 200 based on the transmission time T3 and the reception time T2 corrected by the time correction unit 54 (for example, one-way delay). Value) (estimate). The delay calculation unit 55 causes, for example, the time acquisition unit 51 to transmit and receive the reciprocated message via the transmission and reception unit 20, and acquires the transmission time (T1, T3) and the reception time (T2, T4) in the reciprocated message. The delay calculation unit 55 acquires, from the time information storage unit 41, the transmission times (T1, T3) and the reception times (T2, T4) acquired by the time acquisition unit 51. The delay calculation unit 55 causes the time correction unit 54 to correct the transmission time T3 and the reception time T2, and the corrected transmission time T3 and reception time T2, and the transmission time T1 received from the time information storage unit 41 and the reception Based on the time T4, the one-way delay value of the forward path and the one-way delay value of the backward path are calculated. The delay calculating unit 55 causes the delay information storage unit 43 to store the calculated one-way delay value and the one-way delay value on the return path.

<Operation principle of correction processing of reception time T2 and transmission time T3>
Next, the operation principle of the correction process of the reception time T2 and the transmission time T3 by the delay measurement device 10 according to the present embodiment will be described.
FIG. 5 is a diagram for explaining the time difference between the devices in the present embodiment.
In this figure, the graph shows the relationship between the elapsed time from the reference time T0 and the time difference between the NW device 100 and the NW device 200, which is the time difference between the devices. In this graph, the vertical axis indicates the time difference between the devices, and the horizontal axis indicates the elapsed time from the reference time T0. Further, the waveform W1 shows the change with respect to the elapsed time of the time difference between the devices.

  As shown in this figure, in the time difference between the NW device 100 and the NW device 200, there is a fixed component (offset) which is a time difference (dt) at the reference time T0, and a time difference (dclk) which increases with the passage of time. And the clock fluctuation component. The fluctuation component due to the clock is an error that arises from the difference between the NW device 100 and the NW device 200 in the accuracy of the clock that counts time. The time difference between devices at a certain time is expressed as the following equation (1).

(Time difference between devices at a certain time) = (time difference due to clock error)
+ (Time difference at reference time T0) (1)

FIG. 6 is a diagram for explaining clock errors in the present embodiment.
FIG. 6A shows an example of the relationship between the correct elapsed time and the elapsed time of the device. In this graph, the vertical axis shows the elapsed time of the device, and the horizontal axis shows the correct elapsed time. The waveform W2 indicates the elapsed time of the NW device 100, and the waveform W3 indicates the elapsed time of the NW device 200. The waveform W4 indicates an ideal elapsed time when the clock accuracy is a standard value, and the slope is "1". On the other hand, in the example shown in FIG. 6A, since the clock is slower than the standard value (ideal value) in the NW apparatus 100, as shown in the waveform W2, the time advances later than the correct elapsed time. It is shown that. Further, the NW device 200 indicates that the clock advances faster than the correct elapsed time, as shown by the waveform W3, because the clock is faster than the standard value (ideal value).

In this embodiment, in order to correct the elapsed time of the NW device 100 and the NW device 200, as shown in FIG. 6B, the relationship between the elapsed time of the NW device 200 and the elapsed time of the NW device 100 is used. .
FIG. 6B illustrates an example of the relationship between the elapsed time of the NW device 100 and the elapsed time of the NW device 200. In this graph, the vertical axis indicates the elapsed time of the NW device 200, and the horizontal axis indicates the elapsed time of the NW device 100. The waveform W5 indicates that the elapsed time of the NW device 200 is faster than the elapsed time of the NW device 100. In this case, the slope (CLKslope) is a value larger than "1"(CLKslope> 1). . The waveform W6 shows the case where the elapsed time of the NW device 200 is later than the elapsed time of the NW device 100. In this case, the slope (CLKslope) becomes a value smaller than "1" (CLKslope <1). . The waveform W7 shows the case where the elapsed time of the NW device 200 and the elapsed time of the NW device 100 coincide, and the slope (CLKslope) becomes “1” (CLKslope = 1).
In the present embodiment, the time correction unit 54 uses the slope (CLKslope) of the elapsed time of the NW device 200 based on the elapsed time of the NW device 100 to calculate the fluctuation component (dclk) due to the clock in FIG. In addition, the reception time T2 and the transmission time T3 are corrected.

<Calculation process of clock error>
Next, with reference to FIG. 7, the details of the calculation process of the clock error in the present embodiment will be described.
FIG. 7 is a diagram showing an example of clock error calculation processing in the present embodiment.
In the example shown in this figure, an example of transmission time (T 1, T 3) and reception time (T 2, T 4) in N round-trip messages acquired by the time acquisition unit 51 via the transmission / reception unit 20 is shown. The clock error calculation unit 52 extracts, for example, at least two or more round trip messages meeting the following two conditions from N round trip messages.

(Condition 1) This is a round trip message in which TTL (Time To Live) of forward packets are equal and TTL of return packets is equal.
This is because when the TTLs are equal, it is likely that two round trip messages have been transmitted through equal paths on the forward and return paths respectively. This is because when the paths are different in the two round-trip messages, errors due to the differences in the paths occur. In this case, the TTL of the forward packet and the TTL of the return packet in one round-trip message may be equal to or different from each other.

(Condition 2) Round-trip transmission delay value RDT is equal (or close) round-trip messages.
That is, the clock error calculation unit 52 selects at least two round trip messages in which the difference between the round trip transmission delay values in the round trip messages is within a predetermined range.
Here, that the round trip transmission delay value RDT is equal (or close) means that the forward path transmission delay value and the backward path transmission delay value in the two round trip messages are very close. Strictly speaking, although there may be cases (or vice versa) in which the return path is reduced by the amount of the forward path, it is rare that the path is the same and the delay amount is the same in the direction in which the backward delay cancels. Therefore, the change in the transmission delay value on the forward path and the return path here can be considered as a change in the deviation between the devices due to the clock error.

  For example, as shown in FIG. 7, the clock error calculation unit 52 selects at least two round-trip messages (“measurement 1” and “measurement N”) that minimize the difference between the round-trip transmission delay values out of N round-trip messages. Choose "). The clock error calculation unit 52 uses the two round-trip messages to determine the slope of the elapsed time of the NW device 200 based on the elapsed time of the NW device 100 which is the clock error per unit time according to the following equation (2) Calculate CLKslope). Further, the clock error calculation unit 52 sets a temporary reference time T0 as shown in the following equation (3).

CLKslope = (T2 _N -T2 ₁ ) / (T1 _N -T1 ₁ ) (2)
T0 = T1 ₁ (3)

Here, transmission time T1 ₁ shows the transmission time T1 of the NW device 100 in reciprocating message "measurement 1", transmission time T1 _N denotes the transmission time T1 of the NW device 100 in reciprocating message "Measurement N" ing. Further, the reception time T2 ₁ shows a reception time T2 of the NW device 200 in reciprocating message "measurement 1", the reception time T2 _N is shows a reception time T2 NW device 200 in reciprocating message "Measurement N" There is.
As described above, the clock error calculation unit 52 calculates the time difference between the transmission times of the two transmission messages transmitted from the NW device 100 (T1 _N- T1 ₁ ) and the reception time of the two transmission messages received by the NW device 200. The clock error (CLKslope) per unit time is calculated based on the time difference (T2 _N- T2 ₁ ) of

  The clock error calculation unit 52 generates the clock based on the time difference between the transmission time and the reception time of the two transmission messages that maximizes the time difference between the transmission times when the number of selected round trip messages is three or more. Calculate the error. Further, when the number of selected round trip messages is three or more, the clock error calculation unit 52 calculates a plurality of clock errors (CLKslope) based on three or more transmission messages, and calculates a plurality of clock errors ( An average clock error which is an average value of CLKslope may be calculated instead of the clock error per unit time (CLKslope) described above.

<Extraction process of minimum round trip transmission delay value by round trip delay method>
Next, details of the process of extracting the minimum value of the round trip transmission delay value RDT according to the round trip delay method in the present embodiment will be described with reference to FIG.
FIG. 8 is a diagram showing an example of extracting the minimum value of the round trip transmission delay value RDT by the round trip delay method in the present embodiment.
In the example shown in this figure, the transmission time (T1, T3), the reception time (T2, T4), the forward transmission delay value d1, and the return in the N round-trip messages acquired by the time acquisition unit 51 via the transmission / reception unit 20. An example of the transmission delay value d2 is shown. The minimum round trip delay extraction unit 531 of the time difference calculation unit 53 calculates the round trip transmission delay value RDT by the following equation (4) in the round trip delay method.

  RDT = d1 + d2 (4)

The minimum round trip delay extraction unit 531 extracts, as the minimum round trip transmission delay value (RDTmin), the round trip transmission delay value having the minimum round trip transmission delay value RDT among “measurement 1” to “measurement N”. In the example shown in FIG. 8, the round trip transmission delay value RDT of “measurement 3” is the minimum value, and the minimum round trip delay extraction unit 531 determines the round trip transmission delay value RDT of “measurement 3” as the minimum round trip transmission delay value (RDT min Extracted as).
The minimum round trip delay extraction unit 531 may extract the minimum round trip transmission delay value (RDTmin) by obtaining the round trip transmission delay value RDT corresponding to each round trip message stored in the time information storage unit 41.

<Extraction of minimum round trip transmission delay value by one-way delay method>
Next, with reference to FIG. 9, the details of the process of extracting the minimum value of the round trip transmission delay value RDT by the one-way delay method in the present embodiment will be described.
FIG. 9 is a diagram showing an example of extracting the minimum value of the round trip transmission delay value RDT according to the one-way delay method in the present embodiment.
In the example shown in this figure, the transmission time (T1, T3r), the reception time (T2r, T4), the forward transmission delay value d1, and the return in the N round-trip messages acquired by the time acquisition unit 51 via the transmission / reception unit 20. An example of the transmission delay value d2 is shown. Here, the reception time T2r and the transmission time T3r are the times corrected by the time correction unit 54 according to the following equations (5) and (6) using the clock error (CLKslope) per unit time described above. is there.

T2r = T2 + (T1-T0) × CLKslope (5)
T3r = T3 + (T1−T0) × CLKslope (6)

Here, the variable T0 is a reference time.
In the one-way delay method, the minimum round trip delay extraction unit 531 of the time difference calculation unit 53 causes the time correction unit 54 to use the reception time T2r and the transmission time T3r corrected by the above equations (5) and (6) Calculate it against. Then, the minimum round trip delay extraction unit 531 calculates the forward path transmission delay value d1 and the backward path transmission delay value d2 for each round trip message according to the following equations (7) and (8).

d1 = T2r-T1 (7)
d2 = T4-T3r (8)

The minimum round trip delay extraction unit 531 extracts the forward path transmission delay value having the smallest forward path transmission delay value d1 as the minimum forward path transmission delay value (d1 min) among “measurement 1” to “measurement N”. In the example illustrated in FIG. 9, the minimum round trip delay extraction unit 531 extracts the forward transmission delay value d1 of "measurement 3" as the minimum forward transmission delay value (d1 min).
Further, the minimum round trip delay extraction unit 531 extracts a return transmission delay value with the smallest return path transmission delay value d2 among the “measurement 1” to “measurement N” as the minimum return path transmission delay value (d2 min). In the example shown in FIG. 9, the minimum round trip delay extraction unit 531 extracts the return transmission delay value d2 of “measurement 1” as the minimum return transmission delay value (d2 min).
The minimum round trip delay extraction unit 531 calculates the minimum round trip transmission delay value (RDTmin) according to the following equation (9) based on the extracted minimum forward path transmission delay value (d1 min) and the minimum return path transmission delay value (d2 min) calculate.

  RDTmin = d1min + d2min (9)

<Calculation processing of inter-device time difference>
Next, with reference to FIG. 10, a process of calculating the inter-device time difference (dt) from the minimum round trip transmission delay value (RDTmin) will be described.
FIG. 10 is a diagram showing an example of the process of calculating the inter-device time difference in the present embodiment.
In this figure, the round trip message is expressed excluding the internal processing period of the NW apparatus 200 from the reception time T2 to the transmission time T3, and the minimum round trip transmission delay value (RDTmin) is the forward transmission delay value d1 and the return transmission It is expressed as the sum of the delay value d2.
The inter-device time difference calculation unit 532 of the time difference calculation unit 53 assumed that the forward transmission delay value d1 and the backward transmission delay value d2 are equal by the following equation (10) based on the minimum round trip transmission delay value (RDTmin) The hypothetical one-way delay value dx of the case is calculated.

  dx = RDTmin / 2 ... (10)

  Further, the inter-device time difference calculation unit 532 calculates an inter-device time difference (dt) according to the following equation (11) based on the calculated one-way delay value dx.

  dt = (d1−dx) or (dx−d2) (11)

The reason for using the minimum round trip transmission delay value (RDTmin) to calculate the inter-device time difference (dt) is to reduce the calculation error of the assumed one-way delay value dx due to the transmission delay.
The inter-apparatus time difference calculation unit 532 stores the calculated inter-apparatus time difference (dt) in the correction information storage unit 42. The inter-device time difference calculation unit 532 uses the transmission time T1 (for example, the transmission time T1 of "measurement 3" in FIG. 8) used in the series of processes for calculating the inter-device time difference (dt) as the reference time T0. The setting is made to be stored in the correction information storage unit 42.

<Time correction processing and calculation processing of one-way delay>
Next, the details of the time correction process by the time correction unit 54 and the calculation process of the one-way delay by the delay calculation unit 55 will be described.
The time correction unit 54 uses the NW device according to the following equation (12) and (13) based on the reference time T0 stored in the correction information storage unit 42, the clock error (CLKslope), and the inter-device time difference (dt). The reception time T2 and the transmission time T3 of 200 are corrected.

T2s = T2 + (T1-T0) × CLKslope + dt (12)
T3s = T3 + (T1−T0) × CLKslope + dt (13)

Here, the variable T2s indicates the corrected reception time T2, and the variable T3s indicates the corrected transmission time T3.
Next, based on the reception time T2s and the transmission time T3s corrected by the time correction unit 54, and the transmission time T1 and the reception time T4 of the NW device 100 not corrected, the delay calculation unit 55 And the one-way delay value of the return path and the one-way delay value of the return path are calculated by the equation (15).

(One way delay value of the outward path) = T2s−T1 (14)
(One-way delay value of return path) = T4-T3s (15)

The operation of the delay measurement system 1 according to the present embodiment will now be described with reference to FIGS.
FIG. 11 is a flowchart showing an example of a delay measurement method by the delay measurement system 1 of the present embodiment.
In this figure, first, the delay measurement apparatus 10 executes a process of calculating a clock error (step S101). As described above, the clock error calculation unit 52 of the delay measurement device 10 calculates the clock error (CLKslope) per unit time, and stores the calculated clock error (CLKslope) in the correction information storage unit 42. The details of the process of step S101 will be described later with reference to FIG.

  Next, the delay measuring device 10 executes an inter-device time difference calculation process (step S102). As described above, the time difference calculation unit 53 of the delay measurement device 10 calculates the inter-device time difference (dt), and stores the calculated inter-device time difference (dt) in the correction information storage unit 42. The details of the process of step S102 will be described later with reference to FIG.

  Next, the delay measuring device 10 transmits and receives a round trip message between the NW device 100 and the NW device 200 (step S103). The transmission and reception unit 20 of the delay measurement device 10 transmits and receives, for example, a round trip message to and from the NW device 200 via the network NW1.

  Next, the delay measuring device 10 acquires the transmission time and the reception time (step S104). That is, the time acquisition unit 51 of the delay measurement device 10 acquires the transmission time (T 1, T 3) and the reception time (T 2, T 4) in the reciprocation message and stores the time in the time information storage unit 41.

  Next, the delay measuring device 10 corrects the transmission time and the reception time (step S105). That is, the time correction unit 54 of the delay measurement device 10 receives the reception time T2 of the NW device 200, based on the clock error (CLKslope) stored in the correction information storage unit 42, the reference time T0, and the inter-device time difference (dt). The transmission time T3 is corrected to match (synchronize) with the time of the NW device 200. The time correction unit 54 corrects, for example, the reception time T2 and the transmission time T3 based on the above-described equations (12) and (13).

  Next, the delay measuring device 10 calculates a one-way delay value (step S106). That is, the delay calculation unit 55 of the delay measurement device 10 calculates the one-way delay value of the forward path and the one-way delay value of the backward path, for example, based on the above-mentioned equations (14) and (15).

  Next, the delay calculating unit 55 determines whether the calculated one-way delay value is valid (step S107). The delay calculation unit 55 determines, for example, whether or not the one-way delay value is valid, based on whether or not the calculated one-way delay value becomes a valid value (positive value). For example, when the one-way delay value is a positive value, the delay calculation unit 55 determines that the one-way delay value is valid (step S107: YES), and the process proceeds to step S108. Further, for example, when the one-way delay value is a negative value or “0”, the delay calculation unit 55 determines that the one-way delay value is not valid (step S107: NO), and returns the process to step S101. Calculation of the correction information of the clock error and the inter-device time difference is executed again.

In step S108, the delay calculation unit 55 stores the calculated one-way delay values (one-way delay value for forward pass and one-way delay value for return pass) in the delay information storage unit 43.
Next, the delay calculating unit 55 determines whether the measurement is completed (step S109). The delay calculating unit 55 ends the process when the measurement is ended (step S109: YES). In addition, when the measurement is not completed (step S109: NO), the delay calculation unit 55 returns the process to step S103, and executes the process of calculating the one-way delay value (periodically) at predetermined time intervals.

Next, the process of step S101 of FIG. 11 described above will be described in detail with reference to FIG.
FIG. 12 is a flowchart showing an example of the calculation process of the clock error according to the present embodiment.
As shown in FIG. 12, the delay measuring device 10 performs transmission and reception (N times of measurement) of the round trip message (step S201). That is, for example, the clock error calculation unit 52 of the delay measurement device 10 causes the time acquisition unit 51 to transmit and receive the round trip message N times via the transmission and reception unit 20.

  Next, the clock error calculation unit 52 acquires the transmission time (T1, T3) and the reception time (T2, T4) in the N round-trip messages via the time acquisition unit 51 (step S202). Specifically, the clock error calculation unit 52 acquires the transmission time (T1, T3) and the reception time (T2, T4) stored in the time information storage unit 41 by the time acquisition unit 51.

  Next, the clock error calculation unit 52 extracts two round trip messages from the N round trip messages (step S203). For example, as described above with reference to FIG. 7, the clock error calculation unit 52 selects at least two round-trip messages in which the difference between the round-trip transmission delay values RDT is minimized.

Next, the clock error calculation unit 52 calculates a clock error (CLKslope) (step S204). The clock error calculation unit 52 calculates a clock error (CLKslope) per unit time based on, for example, the above-mentioned equation (2).
Next, the clock error calculation unit 52 stores the calculated clock error (CLKslope) in the correction information storage unit 42 (step S205). After the process of step S205, the clock error calculation unit 52 ends the process of step S101 of FIG.

Next, the process of step S102 in FIG. 11 described above will be described in detail with reference to FIG.
FIG. 13 is a flowchart showing an example of the process of calculating the inter-device time difference according to the present embodiment.
As shown in FIG. 13, the delay measuring device 10 performs transmission and reception (N times of measurement) of the round trip message (step S301). That is, for example, the time difference calculation unit 53 of the delay measurement device 10 causes the time acquisition unit 51 to transmit and receive the round trip message N times via the transmission and reception unit 20.

  Next, the time difference calculation unit 53 acquires the transmission time (T1, T3) and the reception time (T2, T4) in the N round trip messages via the time acquisition unit 51 (step S302). Specifically, the time difference calculation unit 53 acquires the transmission time (T1, T3) and the reception time (T2, T4) stored in the time information storage unit 41 by the time acquisition unit 51.

  Next, the minimum round trip delay extraction unit 531 of the time difference calculation unit 53 branches the process according to the designated measurement method (step S303). The minimum round trip delay extraction unit 531 advances the process to step S304 when the designated measurement method received from the user via the input unit 30 is the “round trip delay method”. In addition, when the designated measurement method received from the user via the input unit 30 is the “one-way delay method”, the minimum round trip delay extraction unit 531 proceeds to step S305.

  In step S304 (in the case of the “round trip delay method”), the minimum round trip delay extraction unit 531 extracts the minimum value (minimum round trip transmission delay value (RDTmin)) of the round trip transmission delay value RDT based on one round trip message. That is, the minimum round trip delay extraction unit 531 extracts the minimum round trip transmission delay value (RDTmin), for example, as described above with reference to FIG. After the process of step S304, the minimum round trip delay extraction unit 531 advances the process to step S309.

  In step S305 (in the case of the “one-way delay method”), the minimum round trip delay extraction unit 531 corrects the clock error between the acquired transmission time T3 and reception time T2. That is, the minimum round trip delay extraction unit 531 corrects the reception time T2 and the transmission time T3 according to Equations (5) and (6), for example, as described above with reference to FIG.

  Next, the minimum round trip delay extraction unit 531 extracts the minimum value of the forward transmission delay value d1 (step S306). The minimum round trip delay extraction unit 531 calculates the forward transmission delay value d1 corresponding to each round trip message according to the above-described equation (7), for example, based on the reception time T2r and the transmission time T1 which are corrected reception time T2. Do. The minimum round trip delay extraction unit 531 extracts the minimum value (d1 min) of the forward transmission delay value from among the calculated N forward transmission delay values d1.

  Next, the minimum round trip delay extraction unit 531 extracts the minimum value of the return transmission delay value d2 (step S307). The minimum round trip delay extraction unit 531 calculates, for example, the return transmission delay value d2 corresponding to each round trip message according to the above-described equation (8) based on the transmission time T3r that is the corrected transmission time T3 and the reception time T4. Do. The minimum round trip delay extraction unit 531 extracts the minimum value (d2 min) of the return transmission delay value from among the calculated N return transmission delay values d2.

  Next, the minimum round trip delay extraction unit 531 extracts the minimum round trip transmission delay value (RDTmin) (step S308). That is, the minimum round trip transmission delay value (D1min) and the minimum value (d2min) of the return path transmission delay value are added by the minimum round trip delay extraction unit 531 according to the above-described equation (9) Calculate RDTmin). After the process of step S308, the minimum round trip delay extraction unit 531 advances the process to step S309.

In step S309, the inter-apparatus time difference calculation unit 532 of the time difference calculation unit 53 calculates an assumed one-way delay value (hypothesis one-way delay value dx). That is, the inter-device time difference calculation unit 532 calculates the hypothetical one-way delay value dx based on the above-described equation (10).
When extracting the minimum round trip transmission delay value (RDTmin) using each method, the minimum round trip delay extraction unit 531 extracts TTL of the minimum value of each transmission delay value, and the TTL of the forward packet is selected from among them. Each minimum value may be extracted from the round trip message in which the TTL of the return packet and the return packet are equal. For example, in step S304, when the minimum value of the round trip transmission delay value is extracted from the plurality of round trip messages, the minimum round trip delay extraction unit 531 round trip transmission of the round trip message in which the TTL of the forward packet and the TTL of the return packet are equal. The delay value may be extracted as the minimum value of the round trip transmission delay value. Thereby, the delay measurement device 10 can measure the transmission delay between devices more accurately.

  Next, the inter-device time difference calculation unit 532 calculates an inter-device time difference (dt) (step S310). That is, the inter-device time difference calculation unit 532 calculates the inter-device time difference (dt) based on the above-mentioned equation (11).

  Next, the inter-apparatus time difference calculation unit 532 stores the calculated inter-apparatus time difference (dt) in the correction information storage unit 42 (step S311). After the process of step S311, the inter-apparatus time difference calculation unit 532 ends the process of step S102 of FIG.

As described above, the delay measurement method according to the present embodiment includes the transmission / reception step, the error calculation step, and the correction step. In the transmitting and receiving step, the transmitting and receiving unit 20 repeatedly transmits and receives a reciprocating message reciprocating between the NW device 100 (first device) and the NW device 200 (second device), and the NW device 100 and NW in the reciprocating message Each transmission time and reception time with the device 200 are measured. In the error calculation step, the clock error calculation unit 52 calculates the difference between the transmission time of the two transmission messages transmitted from the NW device 100 and the time difference of the reception times of the two transmission messages received by the NW device 200. The clock error (CLKslope) per unit time between the NW device 100 and the NW device 200 is calculated. In the correction step, the time correction unit 54 corrects the transmission time and the reception time of the round trip message based on at least the clock error per unit time.
As a result, an error between the time measured by the NW device 100 and the time measured by the NW device 200 is reduced, so that the delay measurement method according to the present embodiment is, for example, between the NW device 100 and the NW device 200. When measuring transmission delay (e.g., one-way delay value), it can be measured more accurately. That is, the delay measurement method according to the present embodiment can more accurately measure the transmission delay between devices.

  In the delay measurement method according to the present embodiment, when performing delay measurement continuously, it is not necessary to measure the offset value (inter-device time difference (dt)) between devices each time delay measurement is performed. The load (computation amount) can be reduced to measure the transmission delay.

In addition, the delay measurement method according to the present embodiment includes an estimation step of estimating a transmission delay between the NW device 100 and the NW device 200 based on the transmission time and the reception time corrected by the correction step.
Thus, the delay measurement method according to the present embodiment can more accurately estimate the transmission delay between devices.

Further, in the present embodiment, the error calculation step includes the following first step (first process) and the second step (second process). In the first step, the clock error calculation unit 52 selects at least two round trip messages in which the difference between the round trip transmission delay value (round trip transmission delay value RDT) in the round trip message is within a predetermined range. In the second step, the clock error calculation unit 52 calculates the clock error (based on the time difference between the transmission time and the reception time of the two transmission messages of the at least two round-trip messages selected in the first step). Calculate CLKslope).
Thus, the delay measurement method according to the present embodiment calculates a clock error (CLKslope) based on two round-trip messages having close round-trip transmission delay values RDT. The two round-trip messages whose round-trip transmission delay value RDT is close are likely to have passed the same path on the network NW1, and further, between the two round-trip messages, the forward path transmission delay value (d1) and the backward path transmission delay It means that the value (d2) is close. Therefore, the delay measurement method according to the present embodiment can calculate the clock error (CLKslope) more accurately. Therefore, the delay measurement method according to the present embodiment can more accurately measure the transmission delay between devices.

Further, in the present embodiment, in the first step described above, the clock error calculation unit 52 selects at least two round-trip messages of which the difference between the round-trip transmission delay values is minimum from the plurality of round-trip messages.
Thereby, the clock error calculation unit 52 calculates the clock error (CLKslope) based on the two round trip messages having the closest round trip transmission delay value RDT. Therefore, the delay measurement method according to the present embodiment can calculate the clock error (CLKslope) more accurately.

Further, in the present embodiment, in the second step described above, when the number of round trip messages selected in the first step is three or more, the clock error calculation unit 52 maximizes the time difference between transmission times 2 A clock error (CLKslope) is calculated based on the time difference between the transmission time and the reception time in one transmission message.
Since the clock error (CLKslope) can be calculated more accurately as the time difference between the transmission times is larger, the delay measurement method according to the present embodiment can calculate the clock error (CLKslope) more accurately.

In the second step described above, when the number of round trip messages selected in the first step is three or more, the clock error calculation unit 52 generates a plurality of clock errors (based on three or more transmission messages). CLKslope) may be calculated, and an average clock error which is an average value of the calculated plurality of clock errors may be calculated. In this case, in the correction step described above, the time correction unit 54 corrects the transmission time and reception time of the reciprocation message based on the average clock error.
Thus, the delay measurement method according to the present embodiment can calculate the clock error (CLKslope) more accurately, and can correct the transmission time and reception time of the reciprocation message more accurately.

In addition, the delay measurement method according to the present embodiment includes a time difference calculation step. In the time difference calculation step, the time difference calculation unit 53 extracts the minimum value (minimum round trip transmission delay value (RDTmin)) of the round trip transmission delay value, which is the round trip transmission delay value in the round trip message, based on the transmission time and reception time. . Furthermore, in the time difference calculation step, the time difference calculation unit 53 calculates an inter-apparatus time difference (dt) indicating the time difference between the NW device 100 and the NW device 200 at the reference time, based on the extracted minimum value. Then, in the correction step described above, the time correction unit 54 corrects the transmission time and the reception time of the reciprocation message based on the clock error (CLKslope) and the inter-device time difference (dt).
Thus, the delay measurement method according to the present embodiment can more accurately correct the transmission time and reception time of the reciprocation message. Therefore, the delay measurement method according to the present embodiment can more accurately measure the transmission delay between devices.

Further, in the present embodiment, in the above-described time difference calculation step, the time difference calculation unit 53 determines the round trip transmission delay value corresponding to the round trip message with the smallest round trip transmission delay value in one round trip message among the plurality of round trip messages. , As the minimum round trip transmission delay value (RDTmin) (round trip delay method).
Thus, the delay measurement method according to the present embodiment can extract the minimum round trip transmission delay value (RDTmin) with high accuracy by a simple means.

Further, in the present embodiment, in the above-described time difference calculation step, the time difference calculation unit 53 determines the forward transmission delay value (d1 min) among the plurality of forward transmission delay values corresponding to the plurality of reciprocating messages, The sum of the transmission delay value (d2min) of the return path which is the minimum among the transmission delay values of the plurality of return paths corresponding to the plurality of return messages is extracted as the minimum roundtrip transmission delay value (RDTmin).
Thus, the delay measurement method according to the present embodiment extracts the minimum round trip transmission delay value (RDTmin) based on the minimum value of the transmission delay value for each of the forward path and the return path. It can be extracted as (RDTmin).

Further, in the present embodiment, in the above-described time difference calculating step, the time difference calculating unit 53 extracts the minimum round trip transmission delay value (RDTmin) based on the transmission time and the reception time corrected based on the clock error (CLKslope). .
Thus, the delay measurement method according to the present embodiment extracts the minimum round trip transmission delay value (RDTmin) based on the corrected accurate transmission time and reception time, so that the minimum round trip transmission delay value (RDTmin) can be more accurately determined. Can be extracted as

Further, the delay measurement device 10 according to the present embodiment includes a time acquisition unit 51, a clock error calculation unit 52, and a time correction unit 54. The time acquisition unit 51 repeatedly transmits and receives a reciprocating message between the NW device 100 and the NW device 200, and acquires transmission time and reception time of the NW device 100 and the NW device 200 in the reciprocating message. The clock error calculation unit 52 calculates the difference between the transmission time of the two transmission messages transmitted from the NW device 100 and the time difference of the reception times of the two transmission messages received by the NW device 200, The clock error (CLKslope) per unit time with the NW device 200 is calculated. Then, the time correction unit 54 corrects the transmission time and the reception time of the round trip message based on at least the clock error (CLKslope) per unit time.
As a result, the delay measurement apparatus 10 according to the present embodiment has the same effects as the above-described delay measurement method according to the present embodiment, and can more accurately measure the transmission delay between the apparatuses. Moreover, since the delay measurement system 1 according to the present embodiment includes the delay measurement device 10, the same effect as the delay measurement device 10 can be obtained, and the transmission delay between the devices can be measured more accurately.

Second Embodiment
Next, a delay estimation method and a delay measurement system according to a second embodiment will be described with reference to the drawings.
FIG. 14 is a block diagram showing an example of the delay measurement system 1a and the delay measurement device 10a according to the present embodiment.

As shown in this figure, the delay measurement system 1a includes the NW device 100a (an example of a first device) connected via the network NW1 and the NW device 200 (an example of a first device) There is. The NW device 100 a further includes a delay measurement device 10 a, a transmitting / receiving unit 20, and an input unit 30.
In addition, in this figure, the same code | symbol is attached | subjected about the structure same as the structure shown in FIG. 1, The description is abbreviate | omitted.

The delay measurement device 10a is, for example, a device for measuring the transmission delay between the NW device 100a and the NW device 200, and includes a storage unit 40 and a control unit 50a.
The control unit 50a is, for example, a processor including a CPU, and centrally controls the NW device 100a (the delay measurement device 10a). The control unit 50a includes a time acquisition unit 51, a clock error calculation unit 52, a time difference calculation unit 53, a time correction unit 54, a delay calculation unit 55, and a correction information update unit 56.
The present embodiment is different from the first embodiment in that the delay measurement device 10 a includes a correction information update unit 56.

  The correction information updating unit 56 periodically monitors the round trip message, and updates the correction information (clock error (CLKslope), reference time T0, inter-device time difference (dt)) stored in the correction information storage unit 42. For example, the correction information updating unit 56 determines whether or not there is a round-trip message that matches the conditions for clock error measurement ((condition 1) and (condition 2) above) in the round-trip message when measuring the one-way delay value. Determine if When there is a round trip message matching the measurement condition of the clock error, the correction information update unit 56 uses the round trip message as the “measurement N” of FIG. Calculate the error (CLKslope). The correction information update unit 56 stores the clock error (CLKslope) calculated by the clock error calculation unit 52 in the correction information storage unit 42.

  The correction information updating unit 56 also changes the NTP when the recalculated clock error (CLKslope) changes by a predetermined value (for example, ± 20%) or more as compared with the previous clock error (CLKslope). It is determined that the time of the NW device 200 has been reset by (Network Time Protocol) or the like. In this case, the correction information update unit 56 causes the clock error calculation unit 52 and the time difference calculation unit 53 to calculate and set again the clock error (CLKslope), the reference time T0, and the inter-apparatus time difference (dt). Make it memorize in 42.

  In addition, for example, the correction information updating unit 56 uses a round-trip message shorter than the minimum round-trip transmission delay value (RDTmin) when calculating the current inter-device time difference (dt) in the round-trip message when measuring the one-way delay value. Determine if there is. When there is a round trip message shorter than the minimum round trip transmission delay value (RDTmin), the correction information update unit 56 sets the round trip transmission delay value of the round trip message as the minimum round trip transmission delay value (RDTmin) Calculate the time difference (dt). The correction information update unit 56 stores the inter-device time difference (dt) calculated by the time difference calculation unit 53 in the correction information storage unit 42 and updates it. Further, the correction information update unit 56 stores the transmission time T1 of the reciprocation message as the reference time T0 in the correction information storage unit 42 and updates it.

  When there is a round trip message shorter than the minimum round trip transmission delay value (RDTmin), the correction information updating unit 56 performs the following correction instead of causing the time difference calculation unit 53 to calculate the inter-apparatus time difference (dt) again. The inter-device time difference (dt) may be calculated by In this case, the correction information updating unit 56 determines the difference between the round-trip transmission delay value of the round-trip message and the minimum round-trip transmission delay value (RDTmin) at the time of calculating the current inter-device time difference (dt) A correction is performed by equally allocating d1 and the return transmission delay value d2 and subtracting them. Then, the correction information updating unit 56 may calculate the inter-device time difference (dt) based on the corrected forward transmission delay value d1 and the backward transmission delay value d2.

Next, with reference to FIG. 15, the operation of the delay measurement system 1a according to the present embodiment will be described.
FIG. 15 is a flowchart showing an example of a delay measurement method by the delay measurement system 1a of the present embodiment.
In this figure, the processing from step S401 to step S408 is the same as the processing from step S101 to step S108 shown in FIG. 11, so the description thereof is omitted here. In addition, the process of step S401 is the same as the process shown in FIG. 12 mentioned above, and the process of step S402 is the same as the process shown in FIG. 13 mentioned above.

  In step S409, the correction information updating unit 56 of the delay measuring device 10a determines whether or not the round trip message matches the clock error measurement conditions ((condition 1) and (condition 2) described above). If the correction information update unit 56 matches the conditions for clock error measurement (step S409: YES), the process proceeds to step S410. Further, when the correction information update unit 56 does not match the conditions for clock error measurement (step S409: NO), the process proceeds to step S412.

  In step S410, the correction information update unit 56 updates the clock error (CLKslope). That is, the correction information update unit 56 causes the clock error calculation unit 52 to calculate the clock error (CLKslope) per unit time using the round trip message. The correction information update unit 56 stores the clock error (CLKslope) calculated by the clock error calculation unit 52 in the correction information storage unit 42.

  Next, the correction information updating unit 56 determines whether or not the clock error (CLKslope) has fluctuated by a predetermined value or more (step S411). That is, the correction information update unit 56 determines whether the clock error (CLKslope) calculated by the clock error calculation unit 52 has fluctuated by, for example, ± 20% or more. If the clock error (CLKslope) fluctuates by a predetermined value or more (step S411: YES), the correction information updating unit 56 returns the process to step S401 and calculates the clock error (CLKslope) and the inter-device time difference (dt) again. Then, the correction information (clock error (CLKslope), reference time T0, inter-device time difference (dt)) is updated. Further, if the clock error (CLKslope) has not changed by a predetermined value or more (step S411: NO), the correction information updating unit 56 advances the process to step S412.

  In step S412, the correction information updating unit 56 determines whether the round-trip transmission delay value of the round-trip message is the minimum value. That is, is whether the correction information updating unit 56 has a round-trip message shorter than the minimum round-trip transmission delay value (RDTmin) when calculating the current inter-device time difference (dt) in the round-trip message when measuring the one-way delay value? It is determined whether or not. If the round trip transmission delay value of the round trip message is the minimum value (step S412: YES), the correction information updating unit 56 advances the process to step S413. Further, if the round-trip transmission delay value of the round-trip message is not the minimum value (step S412: NO), the correction information updating unit 56 advances the process to step S414.

  In step S413, the correction information updating unit 56 updates the inter-device time difference (dt). That is, the correction information updating unit 56 causes the time difference calculating unit 53 to calculate the inter-device time difference (dt) with the round-trip transmission delay value of the round-trip message as the minimum round-trip transmission delay value (RDTmin). The correction information update unit 56 stores the inter-device time difference (dt) calculated by the time difference calculation unit 53 in the correction information storage unit 42 and updates it. Further, the correction information update unit 56 stores the transmission time T1 of the reciprocation message as the reference time T0 in the correction information storage unit 42 and updates it.

  In step S414, the control unit 50a of the delay measurement device 10a determines whether the measurement is completed. The control unit 50a ends the process when the measurement is ended (step S414: YES). In addition, when the measurement is not completed (step S414: NO), the delay calculation unit 55 returns the process to step S403, and executes the process of calculating the one-way delay value (periodically) at predetermined time intervals.

As described above, the delay measurement method according to the present embodiment includes an update step in addition to the delay measurement method according to the first embodiment. In the updating step, the delay measuring device 10a (correction information updating unit 56) periodically monitors the reciprocation message, and if the reciprocation message satisfies a predetermined condition, the correction information stored in the correction information storage unit 42 ( The clock error (CLKslope), the reference time T0, and the inter-apparatus time difference (dt) are updated. Here, the predetermined condition is a condition for updating the correction information, and, for example, the condition of the clock error measurement described above ((condition 1) and (condition 2) described above), the round trip transmission delay value of the round trip message is It is a condition such as being a minimum value.
Thus, the delay measurement method according to the present embodiment can achieve the same effect as the delay measurement method according to the first embodiment, and can further improve the correction accuracy of the transmission time and reception time of the NW device 200. In addition, since the clock error (CLKslope) is periodically updated, the delay measurement method according to the present embodiment is, for example, a case where the clock frequency of the NW device 100a and the NW device 200 changes due to a temperature change or the like. Also, the transmission delay between devices can be measured more accurately.
Further, in the delay measurement method according to the present embodiment, for example, even when the time of the NW device 200 is reset by NTP or the like, the correction information is appropriately updated, so that the transmission delay between the devices can be made more accurately. It can be measured.

  In the present embodiment, the delay measurement method and the update step are performed in a series of processes, but may be performed in different processes. For example, in the updating step, the processing from step S401 to step S402 and the processing from step S409 to step S413 may be continuously performed in the background. In this case, after calculation processing of inter-device time difference is performed in step S402, it is determined in step S409 whether or not the conditions for clock error measurement are met. That is, the update step is continuously performed as a separate process from the delay measurement method. In this case, the priority of the process of the update step may be set higher than that of the other processes. Thereby, the delay measuring device 10a can calculate the correction information more accurately, and can appropriately update the correction information.

In addition, this invention is not limited to said each embodiment, It can change in the range which does not deviate from the meaning of this invention.
For example, in each of the above-described embodiments, the example in which the NW device 100 (100a) includes the delay measurement device 10 (10a) has been described, but the present invention is not limited to this. For example, the delay measurement device 10 (10a) may be provided outside the NW device 100 (100a), and externally measure the transmission delay between the NW device 100 and the NW device 200.

  Further, part of the configuration of the delay measurement device 10 (10a) may be provided outside the NW device 100. For example, part of the control unit 50 (50a) may be provided outside as a processing device on the network NW1. Alternatively, part or all of the storage unit 40 may be provided externally as a storage device on the network NW1. Also, in this case, the delay measurement device 10 (10a) receives the correction information (clock error (CLKslope), reference time T0, inter-device time difference (dt)) generated (calculated) in advance from an external storage device, The transmission time and the reception time may be corrected by acquiring the correction information. For example, the delay measurement method may include a transmission / reception step, an error acquisition step, a time difference calculation step, a correction step, and an estimation step. In this case, in the error acquisition step, the delay measurement device 10 (10a) may acquire a clock error per unit time between the NW device 100 (100a) and the NW device 200.

In each of the above-described embodiments, the delay measuring device 10 (10a) has been described as an example not including the input unit 30 and the transmitting / receiving unit 20, but may be configured to include the input unit 30 or the transmitting / receiving unit 20. .
In each of the above embodiments, the clock error calculation unit 52 calculates the clock error (CLKslope) based on the transmission time T1 and the reception time T2, but the transmission time T3 and the reception time T4 are described. The clock error (CLKslope) may be calculated based on
In each of the above embodiments, the clock error calculation unit 52 has described an example in which the clock error (CLKslope) is calculated as the slope of the passage of time of the NW device 200 viewed from the NW device 100 (100a). It is not limited to For example, the clock error calculation unit 52 may calculate the clock error (CLKslope) as the slope of the passage of time of the NW device 100 (100a) viewed from the NW device 200. Also, the clock error calculation unit 52 may calculate the clock error using a statistical method such as normal distribution or the least square method, for example.

In each of the above-described embodiments, the time difference calculation unit 53 has described an example in which the minimum round trip transmission delay value (RDTmin) is extracted without performing correction by the clock error (CLKslope) in the round trip delay method. The correction by the clock error (CLKslope) may be performed. In this case, the delay measurement device 10 (10a) can further enhance the correction accuracy of the transmission time and the reception time.
The time difference calculation unit 53 corrects the clock error (CLKslope) to extract the minimum round trip transmission delay value (RDTmin) in the one-way delay method, but the clock difference (CLKslope) It is not necessary to make corrections. In this case, the delay measuring apparatus 10 (10a) can simplify the process of extracting the minimum round trip transmission delay value (RDTmin) in the one-way delay method, and can reduce the processing load (calculation amount). .

  In each of the above embodiments, although the example of switching between the round trip delay method and the one-way delay method has been described according to the method of extracting the minimum round trip transmission delay value received from the user via the input unit 30, the invention is limited thereto. It is not a thing. For example, even if the time difference calculation unit 53 switches and executes the round trip delay method and the one-way delay method according to the reliability (stability) of the clock error, such as uncertainty about the accuracy of the clock error (CLKslope). Good. In addition, the time difference calculation unit 53 may calculate the inter-device time difference (dt) by any one method of the round trip delay method and the one-way delay method.

In addition, each structure with which the delay measurement system 1 (1a) mentioned above is equipped has a computer system inside. Then, a program for realizing the function of each component included in the delay measurement system 1 (1a) described above is recorded in a computer readable recording medium, and the computer system reads the program recorded in the recording medium. Processing may be performed in each configuration provided in the above-described delay measurement system 1 (1a) by performing the processing. Here, "to read and execute the program recorded on the recording medium into the computer system" includes installing the program on the computer system. The “computer system” mentioned here includes an OS and hardware such as peripheral devices.
Also, the “computer system” may include a plurality of computer devices connected via a network including communication lines such as the Internet, WAN, LAN, and dedicated lines. The term "computer-readable recording medium" refers to a storage medium such as a flexible disk, a magneto-optical disk, a ROM, a portable medium such as a ROM or a CD-ROM, or a hard disk built in a computer system. As described above, the recording medium storing the program may be a non-transitory recording medium such as a CD-ROM.

  The recording medium also includes a recording medium provided internally or externally accessible from the distribution server for distributing the program. It should be noted that the program is divided into a plurality of parts, and after downloading at different timings, the configurations combined in each configuration provided in the delay measurement system 1 (1a), and the distribution servers that distribute each of the divided programs are different. Good. Furthermore, "computer-readable recording medium" holds a program for a certain period of time, such as a volatile memory (RAM) in a computer system serving as a server or a client when the program is transmitted via a network. We shall include things. Further, the program may be for realizing a part of the functions described above. Furthermore, it may be a so-called difference file (difference program) that can realize the above-described functions in combination with a program already recorded in the computer system.

  In addition, part or all of the above-described functions may be realized as an integrated circuit such as LSI (Large Scale Integration). Each function mentioned above may be processor-ized separately, and part or all may be integrated and processor-ized. Further, the method of circuit integration is not limited to LSI's, and implementation using dedicated circuitry or general purpose processors is also possible. In the case where an integrated circuit technology comes out to replace LSI's as a result of the advancement of semiconductor technology, integrated circuits based on such technology may also be used.

  1, 1a: delay measurement system, 10, 10a: delay measurement device, 20: transmission / reception unit, 21: communication unit, 22: time stamp giving unit, 30: input unit, 40: storage unit, 41: time information storage unit, 42: Correction information storage unit, 43: Delay information storage unit, 50, 50a: Control unit, 51: Time acquisition unit, 52: Clock error calculation unit, 53: Time difference calculation unit, 54: Time correction unit, 55: Delay calculation , 56: correction information update unit, 531: minimum round trip delay extraction unit, 532: inter-device time difference calculation unit, 100, 100a, 200: NW device, NW1: network

Claims (13)

A transmitting and receiving step of repeatedly transmitting and receiving a reciprocating message reciprocating between the first device and the second device, and measuring transmission time and reception time of the first device and the second device in the reciprocating message, respectively; When,
The time difference between the respective transmission times between two transmission messages transmitted from the first device, and the time difference between the respective reception times between the two transmission messages received by the second device Calculating a clock error per unit time between the first device and the second device based on
Based on the transmission time and the reception time, the minimum value of the round trip transmission delay value which is the round trip transmission delay value in the round trip message is extracted, and the first device and the first device are extracted based on the extracted minimum value. A time difference calculating step of calculating an inter-apparatus time difference indicating a time difference between the second apparatus and the second apparatus at a reference time;
Correcting the transmission time and the reception time of the second message of the reciprocated message based on at least the clock error per unit time and the inter-device time difference ;
Updating the clock error or the inter-apparatus time difference when the reciprocation message is monitored periodically and the clock error or the inter-apparatus time difference is satisfied a predetermined condition satisfying the reciprocation message; only including,
In the case where the predetermined condition is satisfied, the first condition that the TTL (Time To Live) of the forward packets is equal and the TTL of the return packets is equal, and the round-trip transmission delay value is equal or It is a case where two said round trip messages which satisfy the second condition that they are close round trip messages are obtained.
Delay measurement wherein a call. Estimating the transmission delay between the first device and the second device based on the transmission time and the reception time of the second device corrected by the correction step. The delay measurement method according to claim 1, characterized in that The error calculation step is
A first step of selecting at least two of said round trip messages whose difference between round trip transmission delay values in said round trip messages is within a predetermined range;
A second step of calculating the clock error based on a time difference between the transmission times of the transmission messages of two of the at least two round-trip messages selected by the first step and a time difference between the reception times The delay measurement method according to claim 1 or 2, further comprising: In the first step,
The delay measurement method according to claim 3, wherein at least two of the plurality of round trip messages for which the difference between the round trip transmission delay values is minimized are selected from the plurality of round trip messages. In the second step,
When there are three or more reciprocating messages selected in the first step, based on the time difference between the transmission times of the two transmission messages and the reception time among the two transmission messages for which the time difference between the transmission times is maximized. The delay measurement method according to claim 3, wherein the clock error is calculated. In the second step,
When the number of round trip messages selected in the first step is three or more, a plurality of the clock errors are calculated based on the three or more transmission messages, and the average value of the calculated plurality of clock errors is calculated. Calculate the average clock error, which is
In the correction step,
The delay measurement method according to claim 3 or 4, wherein the transmission time and the reception time of the round trip message are corrected based on the average clock error. In the time difference calculating step,
Among the plurality of the reciprocating message, the round-trip transmission delay value round-trip transmission delay value in one of the reciprocating message corresponding to said reciprocating message becomes minimum claim 1, wherein the extracting as the minimum value The delay measurement method according to any one of claims 6 . In the time difference calculating step,
Among the transmission delay values of a plurality of forward paths corresponding to a plurality of the reciprocating messages, the transmission delay value of the forward path which is the smallest, and the return path which is the minimum of the transmission delay values of a plurality of return paths corresponding to the plurality of the reciprocating messages The delay measurement method according to any one of claims 1 to 6, wherein an addition value with the transmission delay value of is extracted as the minimum value. And based on the corrected transmission time and the reception time on the basis of the clock error, the delay measuring method as claimed in any one of claims 8, characterized in that extracting the minimum value. A transmitting and receiving step of repeatedly transmitting and receiving a reciprocating message reciprocating between the first device and the second device, and measuring transmission time and reception time of the first device and the second device in the reciprocating message, respectively; When,
The time difference between the respective transmission times between two transmission messages transmitted from the first device, and the time difference between the respective reception times between the two transmission messages received by the second device Obtaining a clock error per unit time between the first device and the second device, which is calculated based on
Based on the transmission time and the reception time, the minimum value of the round trip transmission delay value which is the round trip transmission delay value in the round trip message is extracted, and the first device and the first device are extracted based on the extracted minimum value. A time difference calculating step of calculating an inter-apparatus time difference indicating a time difference between the second apparatus and the second apparatus at a reference time;
Correcting the transmission time and the reception time of the second message of the round trip message based on the clock error per unit time and the inter-device time difference;
Estimating a transmission delay between the first device and the second device based on the transmission time and the reception time of the second device corrected by the correction step ;
Updating the clock error or the inter-apparatus time difference when the reciprocation message is monitored periodically and the clock error or the inter-apparatus time difference is satisfied a predetermined condition satisfying the reciprocation message; only including,
In the case where the predetermined condition is satisfied, the first condition that the TTL (Time To Live) of the forward packets is equal and the TTL of the return packets is equal, and the round-trip transmission delay value is equal or It is a case where two said round trip messages which satisfy the second condition that they are close round trip messages are obtained.
Delay measurement wherein a call. A transmitting and receiving step of repeatedly transmitting and receiving a reciprocating message reciprocating between the first device and the second device, and measuring transmission time and reception time of the first device and the second device in the reciprocating message, respectively; When,
The time difference between the respective transmission times between two transmission messages transmitted from the first device, and the time difference between the respective reception times between the two transmission messages received by the second device Calculating a clock error per unit time between the first device and the second device based on
Based on the transmission time and the reception time, the minimum value of the round trip transmission delay value which is the round trip transmission delay value in the round trip message is extracted, and the first device and the first device are extracted based on the extracted minimum value. A time difference calculating step of calculating an inter-apparatus time difference indicating a time difference between the second apparatus and the second apparatus at a reference time;
Updating the clock error or the inter-apparatus time difference when the reciprocation message is monitored periodically and the clock error or the inter-apparatus time difference is satisfied a predetermined condition satisfying the reciprocation message; only including,
In the case where the predetermined condition is satisfied, the first condition that the TTL (Time To Live) of the forward packets is equal and the TTL of the return packets is equal, and the round-trip transmission delay value is equal or It is a case where two said round trip messages which satisfy the second condition that they are close round trip messages are obtained.
Delay measurement wherein a call. An acquisition unit that repeatedly transmits and receives a reciprocating message reciprocating between the first device and the second device, and acquires transmission time and reception time of the first device and the second device in the reciprocating message; ,
The time difference between the respective transmission times between two transmission messages transmitted from the first device, and the time difference between the respective reception times between the two transmission messages received by the second device An error calculation unit that calculates a clock error per unit time between the first device and the second device based on
Based on the transmission time and the reception time, the minimum value of the round trip transmission delay value which is the round trip transmission delay value in the round trip message is extracted, and the first device and the first device are extracted based on the extracted minimum value. A time difference calculating unit that calculates an inter-apparatus time difference indicating a time difference between the second apparatus and the second apparatus at a reference time;
A correction unit that corrects the transmission time and the reception time of the second message of the reciprocating message based on at least the clock error per unit time and the inter-device time difference ;
An updating unit that periodically monitors the round trip message and updates the clock error or the inter-apparatus time difference when the round-trip message satisfies the clock error or a predetermined condition for updating the inter-apparatus time difference; Equipped with
In the case where the predetermined condition is satisfied, the first condition that the TTL (Time To Live) of the forward packets is equal and the TTL of the return packets is equal, and the round-trip transmission delay value is equal or It is a case where two said round trip messages which satisfy the second condition that they are close round trip messages are obtained.
Delay measurement device comprising a call. On the computer
A transmitting and receiving step of repeatedly transmitting and receiving a reciprocating message reciprocating between the first device and the second device, and measuring transmission time and reception time of the first device and the second device in the reciprocating message, respectively; When,
The time difference between the respective transmission times between two transmission messages transmitted from the first device, and the time difference between the respective reception times between the two transmission messages received by the second device Calculating a clock error per unit time between the first device and the second device based on
Based on the transmission time and the reception time, the minimum value of the round trip transmission delay value which is the round trip transmission delay value in the round trip message is extracted, and the first device and the first device are extracted based on the extracted minimum value. A time difference calculating step of calculating an inter-apparatus time difference indicating a time difference between the second apparatus and the second apparatus at a reference time;
Correcting the transmission time and the reception time of the second message of the reciprocated message based on at least the clock error per unit time and the inter-device time difference ;
Updating the clock error or the inter-apparatus time difference when the reciprocation message is monitored periodically and the clock error or the inter-apparatus time difference is satisfied a predetermined condition satisfying the reciprocation message; was executed,
In the case where the predetermined condition is satisfied, the first condition that the TTL (Time To Live) of the forward packets is equal and the TTL of the return packets is equal, and the round-trip transmission delay value is equal or It is a case where two said round trip messages which satisfy the second condition that they are close round trip messages are obtained.
Program.

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