JP2009128174A - Time synchronization system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a time synchronization system capable of synchronizing highly accurately each time between a plurality of devices. <P>SOLUTION: This time synchronization system is equipped with at least a first testing device having a reference time, and a second testing device for synchronizing time with the first testing device based on the reference time of the first testing device. The first testing device calculates a transmission delay time, and transmits a time informing frame determined by adding the reference time to the transmission delay time to the second testing device, and the second testing device uses a time in the time informing frame as a reference time. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a time synchronization system that performs data transmission using time information, and more particularly to a time synchronization system that can achieve time synchronization between a plurality of devices with high accuracy.

  In recent years, WANs have been constructed in each region based on LAN technology, and a communication network in which these are connected by a backbone network has been constructed on a nationwide scale. As known communication devices for connecting LANs and WANs, switches, routers, gateways, and the like are known, and exchange / transmission of signals in frame units is performed.

  By the way, in some tests of such communication apparatuses, time information is used. For example, when examining the internal processing time of devices such as routers and switches for each port, test data including time information is generated and sequentially input to one port of the device under test. Receives test data output from other ports, and obtains the difference between the reception time and the time information included in the received test data for each port. Prior art documents of such communication systems using switches and routers include the following.

JP 2006-074083 A

Hereinafter, a conventional time synchronization system will be described with reference to FIG. FIG. 5 is a configuration example of a time synchronization system according to the prior art. The transmission test apparatus 10 transmits a test frame via the test target apparatus 30 and receives the test frame 500 at the reception test apparatus 20.

Here, the test frame 500 includes, for example, a preamble 511, a header portion, a payload portion, and a frame check code 523 as shown in FIG. The header portion includes a transmission destination address 512, a transmission source address 513, and control information 514. The payload portion includes an arbitrary pattern 521 and transmission time information 522.

The transmission test apparatus 10 embeds the transmission time in the transmission time information 522 of the test frame 500 and transmits it. When receiving the test frame 500, the reception test apparatus 20 compares the transmission time information 522 and the time information held by the reception test apparatus 20 to calculate a delay time from transmission to reception.

With this method, it is possible to measure the delay time generated by the frame exchange process performed by the test target device 30. At this time, it is a condition that the time information held by each of the transmission test apparatus 10 and the reception test apparatus 20 is synchronized.

  FIG. 7 is a configuration example of a time synchronization system when the same time information is used on the transmission side and the reception side. In the system of FIG. 7, time synchronization is realized by using the same time information in a test apparatus that performs transmission and a test apparatus that performs reception. Therefore, it is necessary to arrange the two at a short distance where the wiring delay does not affect, for example, in the same housing.

FIG. 8 is a configuration example of the time synchronization system when the transmission side and the reception side are directly wired. In the system of FIG. 8, a wiring is prepared between the transmission test apparatus 50 and the reception test apparatus 51, and the reception test apparatus 51 (or the transmission test apparatus) is based on the time information of the transmission test apparatus 50 (or the reception test apparatus 51). 50) is notified of time information, and time synchronization is realized by counting the time using the same clock signal.

  FIG. 9 is a configuration example of a time synchronization system when an external reference time such as GPS is used. In the system of FIG. 9, each of the transmission test apparatus 60 and the reception test apparatus 61 is provided with a time information reception port and uses an external reference time acquisition function such as GPS.

As another method of synchronization, an NTP (Network Time Protocol) client function may be installed in each test apparatus, and time synchronization may be realized by independently acquiring reference time information.

As described above, the time synchronization of the system is conventionally achieved by various methods.

  However, in the system of FIG. 7, since both the transmission side and the reception side must use one time information, the transmission / reception block must be arranged at a short distance where the wiring delay does not affect, for example, in the same housing. There is a problem that must be.

Further, the system of FIG. 8 has a problem that time synchronization cannot be achieved with high accuracy because a delay time due to wiring of a clock signal and a reference time signal becomes a time synchronization error. Further, there is a problem that even when the time synchronization is shifted due to wiring abnormality or the like, it cannot be detected.

In addition, the system of FIG. 9 has a problem in that an error between devices occurs due to the accuracy of the external reference time, in addition to the need for reference time information outside the system. Further, since it is necessary to be able to receive signals such as GPS, there is a problem in that the cost of the entire system increases.

  An object of this invention is to provide the time synchronization system which can take the time synchronization between several apparatuses with high precision.

In order to achieve such a problem, the invention described in claim 1
In a time synchronization system comprising at least a first test device having a reference time and a second test device that synchronizes time with the first test device based on the reference time of the first test device,
The first test apparatus calculates a transmission delay time and transmits a time notification frame obtained by adding a reference time to the transmission delay time to the second test apparatus,
The second test apparatus uses the time of the time notification frame as a reference time.

The invention according to claim 2
In a time synchronization system including at least a first test device having a reference time and a second test device that synchronizes time with the first test device based on the reference time of the first test device,
The first test apparatus includes:
A time storage unit for storing a reference time of the own test apparatus;
Based on the time of the time notification frame returned by the second test apparatus and the reference time stored in the time storage unit, the transmission delay time that occurs until the time notification frame reaches the second test apparatus is calculated. A delay time calculation unit,
A delay time storage unit for storing the delay time calculated by the delay time calculation unit;
The reference time stored in the time storage unit and a time notification frame including information indicating that the delay measurement is performed are transmitted, and the reference time stored in the time storage unit is stored in the delay time storage unit. A time transmission unit that transmits a time notification frame with a delay time added,
The second test apparatus includes:
When a time notification frame including reference time and delay measurement is received, it is returned to the first test apparatus as it is, and the delay time stored in the delay time storage unit is added to the reference time stored in the time storage unit. A time receiving unit for receiving a time notification frame;
A time storage unit that stores the time in the time notification frame received by the time reception unit.

And the invention of claim 3 is
Time synchronization method in a time synchronization system comprising at least a first test device having a reference time and a second test device that synchronizes time with the first test device based on the reference time of the first test device Because
A first step in which a time transmission unit of the first test apparatus transmits a time notification frame including information indicating that a reference time and delay measurement are performed;
A second step in which the time receiving unit of the second test apparatus returns the time notification frame to the first test apparatus as it is;
The delay time calculation unit of the first test apparatus calculates a transmission delay time that occurs until the time notification frame reaches the second test apparatus based on the time of the folded time notification frame and the reference time. 3 steps,
A fourth step in which the time transmitter of the first test apparatus transmits a time notification frame obtained by adding a reference time to the transmission delay time calculated in the third step;
A fifth step in which the time receiving unit of the second test apparatus receives the time notification frame input in the fourth step;
A time storage unit of the second test apparatus includes a sixth step of storing the time of the time notification frame received in the fifth step.

  The present invention has the following effects. The first test apparatus calculates a transmission delay time, and transmits a time notification frame obtained by adding a reference time to the transmission delay time to the second test apparatus, and the second test apparatus determines the time of the time notification frame. Since the reference time is used, it is possible to provide a time synchronization system that can achieve time synchronization between a plurality of devices with high accuracy.

The time synchronization system of the present invention will be described below. FIG. 1 is a diagram for explaining the outline of the operation of the present invention. First, as shown in FIG. 1A, the test apparatus 100 and the test apparatus 200 are wired so that a “clock signal”, a “reference time notification signal”, and a “turnback time notification signal” can be transmitted. .

The operation of FIG. 1 will be described. As shown in FIG. 1B, the test apparatus 100 notifies the test apparatus 200 of the reference time. The test apparatus 200 notifies the test apparatus 100 of the received reference time as it is. The test apparatus 100 compares the received time with its own reference time, and calculates a return delay time, that is, a round-trip delay time.

The test apparatus 100 calculates a wiring delay from the calculated return delay time to the test apparatus 200 as shown in FIG. In this case, since the reference time received by the test apparatus 200 is returned to the test apparatus 100 as it is, for example, 1/2 of the round trip delay time is calculated as the wiring delay. As shown in FIG. 1D, the test apparatus 100 notifies the test apparatus 200 of the time obtained by adding its own reference time and the wiring delay, and the test apparatus 200 uses this time as the reference time.

  FIG. 2 is a functional block diagram of a test apparatus used in the time synchronization system according to the present invention. In FIG. 2, a test apparatus 100 is a test apparatus having a reference time and an oscillator 110. The test apparatus 200 is a test apparatus that receives the time and clock from the test apparatus 100.

  The oscillator 110 is an oscillator that generates a clock used to count up the time. The time storage unit 111 is a block that stores time information (for example, a reference time) and counts up using a clock. The time transmitter 112 is a block that transmits time information to the outside. The delay time calculation unit 113 is a block that compares the time information from the outside with the time of its own device to calculate the transmission delay.

The delay time storage unit 114 is a block that stores the delay time calculated by the delay time calculation unit 113. The time receiving unit 115 is a block that receives time information from the outside and performs time information return, time registration, and time information output from the time storage unit 116 in accordance with an instruction in the received information. The time storage unit 116 is a block that stores the time information received by the time reception unit 115 and counts up using a clock.

The operation of FIG. 2 will be described. Hereinafter, an operation until time synchronization (A. time synchronization sequence) and an operation for confirming whether time synchronization is achieved with respect to a device synchronized with this method (B. time synchronization confirmation) will be described. Separately described.

A. The time synchronization sequence test apparatus 100 transmits a time notification frame including time information in the time storage unit 111 and information indicating that delay measurement is performed from the time transmission unit 112. Here, the time notification frame includes time information 603 as well as information on various commands 602 (delay measurement: 0, time registration: 1, time request: 2) as shown in FIG. Since “0” is selected because delay measurement is performed.

Returning again to FIG. When the test apparatus 200 receives the time information frame instructing the time information and delay measurement (0: delay measurement is designated by the command 602 in FIG. 3), the test apparatus 200 transmits the time notification frame to the return test apparatus 100 as it is.

The test apparatus 100 uses the delay calculation unit 113 to calculate a transmission delay until the time notification frame reaches the test apparatus 200 based on the time in the folded time notification frame and the time of its own apparatus. For example, “(time of own device−notified time) / 2” is set as the transmission delay time.

The calculated delay time is stored in the delay time storage unit 114. The time transmission unit 112 transmits a time notification frame whose content of time registration is a value obtained by adding the value of the delay time stored in the delay time storage unit 114 to the reference time stored in the time storage unit 111. At this time, the command 602 in FIG. 3 specifies 1: time registration.

When the time reception unit 115 of the test apparatus 200 receives the time notification frame transmitted from the time transmission unit 112, the time reception unit 115 stores the time in the frame in the time storage unit 116. In this way, time synchronization is established between the test apparatus 100 and the test apparatus 200.

B. The time synchronization confirmation test apparatus 100 transmits a time notification frame in which a time request (command 602 selects “2”) is selected from the time transmission unit 112. When receiving the time notification frame, the test apparatus 200 transmits time information in the time storage unit 116 to the test apparatus 100.

The test apparatus 100 compares the time in the time notification frame with the time of its own apparatus by the delay calculation unit 113 and confirms whether the time is correctly synchronized. For example, if the time obtained by adding the delay time stored in the delay time storage unit 114 to the time in the received time notification frame notification matches the reference time of its own device, it is determined as normal.

As described above, the test apparatus 100 calculates the transmission delay time and transmits a time notification frame obtained by adding the reference time to the transmission delay time to the second test apparatus, and the test apparatus 200 transmits the time notification frame. Since the time is set as the reference time, it is possible to provide a time synchronization system that can achieve time synchronization between a plurality of devices with high accuracy.

  Next, as an application of the present invention, a method for synchronizing time between a plurality of test apparatuses will be described with reference to FIG. The function of the test apparatus 310 includes both the function block of the test apparatus 100 and the function block of the test apparatus 200 shown in FIG. The test apparatuses 320, 330, and 340 have the same functional block diagram as the test apparatus 310.

  First, a plurality of test apparatuses 310, 320, 330, and 340 are connected with cables of arbitrary lengths in order to wire clock, reference time, and turn-back time signals (FIG. 4A). The reference time possessed by the test apparatus 310 is notified to the test apparatus 320 by the method described in FIG. 2, and the reference time is shared (FIGS. 4B and 4C).

Subsequently, the reference time of the test apparatus 320 is notified to the test apparatus 330 in the same procedure (FIGS. 4D and 4E). The description after the test apparatus 340 is omitted because the same procedure may be repeated.

In this way, by repeating the operation described in FIG. 2 one after another, it becomes possible to synchronize the time between the test apparatuses regardless of the number of test apparatuses.

It is drawing for demonstrating the outline | summary of operation | movement of this invention. It is a functional block diagram of the test apparatus used with the time synchronization system by this invention. It is an example of the time notification frame of the present invention. It is an application example of the time synchronization system by this invention. It is a structural example of the time synchronization system by a prior art. It is a structural example of a test frame. It is a structural example of the time synchronization system in the case of using the same time information on the transmission side and the reception side. It is a structural example of the time synchronization system in the case where the transmission side and the reception side are directly wired. It is a structural example of the time synchronization system at the time of utilizing external reference time, such as GPS.

Explanation of symbols

100 Test apparatus 110 Oscillator 111 Time storage section 112 Time transmission section 113 Delay time calculation section 114 Delay time storage section 115 Time reception section 116 Time storage section 200 Test apparatus

Claims (3)

In a time synchronization system comprising at least a first test device having a reference time and a second test device that synchronizes time with the first test device based on the reference time of the first test device,
The first test apparatus calculates a transmission delay time and transmits a time notification frame obtained by adding a reference time to the transmission delay time to the second test apparatus,
The second test apparatus uses the time of the time notification frame as a reference time. In a time synchronization system including at least a first test device having a reference time and a second test device that synchronizes time with the first test device based on the reference time of the first test device,
The first test apparatus includes:
A time storage unit for storing a reference time of the own test apparatus;
Based on the time of the time notification frame returned by the second test apparatus and the reference time stored in the time storage unit, the transmission delay time that occurs until the time notification frame reaches the second test apparatus is calculated. A delay time calculation unit,
A delay time storage unit for storing the delay time calculated by the delay time calculation unit;
The reference time stored in the time storage unit and a time notification frame including information indicating that the delay measurement is performed are transmitted, and the reference time stored in the time storage unit is stored in the delay time storage unit. A time transmission unit that transmits a time notification frame with a delay time added,
The second test apparatus includes:
When a time notification frame including reference time and delay measurement is received, it is returned to the first test apparatus as it is, and the delay time stored in the delay time storage unit is added to the reference time stored in the time storage unit. A time receiving unit for receiving a time notification frame;
A time synchronization system comprising: a time storage unit that stores a time in a time notification frame received by the time reception unit. Time synchronization method in a time synchronization system comprising at least a first test device having a reference time and a second test device that synchronizes time with the first test device based on the reference time of the first test device Because
A first step in which a time transmission unit of the first test apparatus transmits a time notification frame including information indicating that a reference time and delay measurement are performed;
A second step in which the time receiving unit of the second test apparatus returns the time notification frame to the first test apparatus as it is;
The delay time calculation unit of the first test apparatus calculates a transmission delay time that occurs until the time notification frame reaches the second test apparatus based on the time of the folded time notification frame and the reference time. 3 steps,
A fourth step in which the time transmitter of the first test apparatus transmits a time notification frame obtained by adding a reference time to the transmission delay time calculated in the third step;
A fifth step in which the time receiving unit of the second test apparatus receives the time notification frame input in the fourth step;
A time synchronization method in the time synchronization system, wherein the time storage unit of the second test apparatus includes a sixth step of storing the time of the time notification frame received in the fifth step.

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